Parts of the Microscope

It is very important that we all agree on what we are going to call the parts of a microscope. As a repair person I have had to many callers tell me that the thingummy next to the small knob is broken. Well there aren't any thingummies on the modern microscope. What is worse is that a lot of times I could have told the user how to fix the problem over the phone if I just knew what the heck they were talking about!

The main module of a microscope is the frame. This is the module that contains the focus mechanism and the connecting points for other modules. The frame can be any of the types we discussed in Basics. The design and manufacture of the frame is central to the performance of the microscope.

In the bad old days the user sat behind the frame since the separate light source had to be in front. Now all microscopes let you sit in front of the frame. This makes it easier on the user since it is a lot easier to put specimens on the stage. The controls on a modern microscope are designed for use from the front. The top part of the frame of an upright microscope is called the limb. This supports the nosepiece, any intermediate pieces and the observation tube. The bottom of the frame is called the base and usually contains the electronics for the illuminator and the field diaphragm assembly.

Focus mechanisms move either the nosepiece (in AO products and inverteds) or the stage (in all other microscopes) to focus the image. The precision of the focus mechanism is critical to using high resolution objectives. If the focus mechanism isn't precise then it is difficult to focus the specimen and keep it in focus.

The fine focus can be either limited or continuous. Limited fine focus mechanisms can only focus over a limited range. These mechanisms tend to be very accurate but when you run out of fine focus you need to return the focus mechanism to the center of its range and focus as well as you can with the course to get the fine focus into range. This is a real pain, that's why most modern makers use the continuous fine focus. Continuous fine focus uses a gear reduction system to connect the coarse and fine focus. This means that the fine focus can be used through out the whole focus range. Modern continuous focus mechanisms work very well. I feel that the trade of convenience for performance is worth it.

The nosepiece attaches to the frame as a module or is mounted permanently to it. It is drilled and tapped to accept the objectives. A nosepiece is rated by how many objectives it can accept. The usual size these days is five but six place nosepieces are available and are usually a good deal.

If the nosepiece angles the objectives towards the user if is called a front facing nosepiece. If it angles the objectives towards the frame it is called a rear facing nosepiece. Rear facing nosepieces are the easiest to use although they can be more difficult to manufacture. It is easier to put specimens on a microscope with a rear facing nosepiece and it is more difficult to get your fingers on the front of the objectives and dirty them up.

Some frames have the nosepiece permanently mounted to it. This is to reduce cost and in some cases is a reasonable trade of. Removable nosepieces allow you to put another set of objectives on the microscope very easily. If you are doing a lot of techniques this is a help. Cleaning objectives is also easier with a removable nosepiece.

The objectives screw into the nosepiece. Objectives provide both resolution and magnification for the microscope. However they don't provide all the magnification or resolution. It is perfectly OK to unscrew and examine the front of objectives. In fact it is something you should do routinely.

The observation tube is attached to the frame above the nosepiece. I'm not going to even go into monoculars, a modern observation tube is a binocular at least. Observation tubes can also have positions (called ports) for

one or more documentation systems (cameras, tv,etc). The observation tube has two places to put eyepieces, also called oculars. We aren't going to call them oculars because it is yet another confusing term. The eyepieces magnify the image and provide a place to put measuring reticule. Research microscopes usually have a place in the frame to put reticules. This allows the reticule to be photographed with the specimen.

Any module located between the limb and the binocular tube is called an intermediate piece. These include fluorescence, reflected light, multi-veiw and magnification changers modules. When you are calculating the total magnification of the microscope you must include any intermediate pieces.

The stage sits below the nosepiece and supports the specimen. Most modern stages are mechanical with low, coaxial controls. This means that there is a single control hanging down from the stage that moves the specimen. It is very important that the stage be flat and that it be at right angles to the objective. If it isn't the specimen will keep going out of focus as it is moved. This is more important as the resolution of the objective increases. If you constantly have to refocus as you scan a specimen call your service person, it may be fixable.

Manufacturers are bringing out stages that have tops made out of stainless steel and ceramic. These materials really reduce the stage tops wear and are an excellent idea. The increase in cost is more than paid back by their increase in longevity and productivity. The clips that hold the specimen are called the specimen holder. No surprise here! These are made in a zillion different styles. If you don't like one then try another. Some specimen holders have adjustable spring tension. This can help when the specimen sticks to the stage.

Directly below the stage is the substage assembly. This module includes the condenser carrier and support for any other condenser optics. If the microscope is supposed to be capable of Kohler illumination then the carrier must have the ability to focus and center the condenser. A student diffusion illuminated microscope will have a focusable condenser carrier but it will not be centerable.

A Kohler illuminated microscope will have a focusing knob for the condenser and two screws that center the condenser. The screws will be facing forward or backward depending on the microscope. On most microscopes there will also be a knob or screw that locks the condenser into the condenser carrier. This allows you to remove the condenser and clean it or replace it with another with out having to completely recenter it, at least you will be in the ball park.

Different condensers are required for different techniques. If you want to do phase you will need a phase condenser, the same for Nomarski or dark field. Some condenser can do a wide range of techniques. These are called universal condensers for the wide range of things that they are capable of. They are also called "pancake" condensers because of their flat, circular construction.

Located on the condenser is the condenser diaphragm control. This may be a lever or a dial either way this controls the contrast of the microscope image. It also controls part of the resolution of the microscope. What it doesn't control is the intensity of the microscope, that is controlled by the electronics.

The base of the microscope contains the field diaphragm. This controls the size of the illuminated field. The field diaphragm control is located either around the lens located in the base or behind it. The location varies based on the manufacturer. Either under the field lens or behind the frame is the light source. Each light source uses a lamp. While this may seem like the obvious statement of the year there is a problem here. There is no such thing as a microscope lamp. Microscopes vary wildly as to what lamp they use. It is a real good idea to make a note of the lamp type and place it in the file with the rest of the information about the microscope.

All microscope manufacturers list their lamps under their parts number. Don't take this too seriously. Ask the dealer for the generic description of the lamp such as "six volt, 20 watt quartz halogen" . Usually this will be written 6V-20W Q.I.. You can then order lamps from the least expensive sources. Microscope dealers sometimes don't have the best prices on lamps since if they buy them from the microscope manufacturer

since they have gone through to long a distribution chain. There are darn few lamp manufacturers and most of them are very good. You can order lamps made by Osram and Phillips with impunity. Just get the best price by asking around and ordering in bulk. If you order for the whole lab you will get a better price than by ordering by ones and twos.

Some were on the base of the frame will be the on-off switch and light intensity control. These may be one dial or slider. The electronics of a microscope controls the light intensity. The condenser diaphragm controls the contrast not the intensity.

Most microscopes change intensity by changing the voltage to the lamp. This raises or lowers the intensity of the lamp. It also changes the color of the light that the lamp produces. Reducing the voltage makes the light more red while increasing it makes the light more blue. Mostly this isn't a problem, a blue filter will usually be adequate for most viewing. If your taking color pictures it can be a real problem. The usual way to control this is when doing color documentation is to keep the voltage at the optimum (ie. 6V for a 6V lamp). If you need to lower intensity then use a neutral density, gray, filter. Some research microscopes use only neutral density filters to control light intensity through very complex, motor drive systems. These really work but are very expensive.

What this means to you Know the parts of the microscope so you can communicate effectively. Know what lamp your microscope really uses.

The Basics of the Microscope

The modern microscope is a collection of interchangeable parts. There is no such thing as a "phase microscope" or a "fluorescence microscope", the microscope is made up of a collection of parts, call them modules, that provide the required functions. Microscope manufacturers work very hard to increase the modularity of their microscopes. The more modular the more economically they can manufacture them. They don't have to manufacture a frame just for metallurgists or a binocular head just for biologists. They can manufacture a range of modules and use them for a wide range of purposes.

There are two basic types of modern microscopes, the stereo and the compound. The stereo uses two separate light paths to get a true stereo image of the specimen. The compound has one beam path but may split that into two parts, one for each eye. This is binocular vision which is different from stereo.

When you look into a stereo microscope you see the specimen's depth in true 3-D. This makes it real easy to dissect objects, do surgery or look at complex 3-D objects. Stereos are limited in their resolution so they are limited in their magnification. Stereos are the most used microscope, they are found every were from ecology studies to machine tools.

The binocular compound is the microscope used when high resolution is needed and when depth perception is not needed. Compound means that there are two major optical parts to the microscope, an objective and an eyepiece, providing magnification. Frankly the stereo works in a very similar fashion but I'm going to use compound because every body else does.

In the old days compound microscopes could be either monocular (only one eye could be used) or binocular (both eyes are used). The modern compound microscope is binocular. Monocular microscopes are a commercial non-entity. If they are sold at all they are sold to small schools that should know better. Monoculars are very hard to use even for experienced users. They take all the fun out of the micro world. If you have budget constraints and are thinking of a monocular microscope try buying good used binocular microscopes. This is a far better plan than killing some ones love of the micro world with an impossible to use microscope.

To make it easier on all of us, me writing and you reading, I am from here on out going to call a compound microscope a microscope and a stereo microscope a stereo. That's what everyone commercially calls them and I guess I'll go along with the crowd.

A modern microscope comes in two basic frame types. These are the upright and the inverted. The upright microscope looks down on the specimen with its objectives. This is the most used type of microscope. The inverted looks up at the specimen. Inverteds are designed to be used were ever the specimen is very large or heavy or were the specimen is influenced by gravity. Yes I know that everything is influenced by gravity but some things like cells in suspension are influenced more than others. Inverted microscopes are used to look at materials, cell culture and aquatic specimens.

These types of specimens show the two uses for inverted microscopes. Materials specimens can be both large and heavy, they need the large, fixed stages that are typical of modern inverteds. Cell culture and aquatic specimens collect on the bottom of their containers. The only way to see these specimens with any ease is to look up through the bottom of the container.

Inverteds come in two sizes, routine and research. The routine size is the smaller of the two and is built with limited uses in mind. It may not have a fine focus since it is designed for low to medium powers only, its stage may not be as versatile and it may not accept cameras as easily as a research inverted. The research inverted is designed to do everything. Any technique you can think of along with a wide range of documentation accessories (35mm cameras, tv., etc.). All research inverted can be equipped for Kohler illumination. These are large, expensive and complex microscopes that can do a wide range of things. If you

need a wide range of things done with an inverted then buy one.

If you are doing materials work you will probably use a research inverted without a transmitted illuminator. This setup used to be called a metalagraph. However in todays materials scene were a metalurgist may be looking at carbon fibers and the microscope being used is the same frame as a biologists I feel that the term is outdated.

Upright microscopes come in three general sizes; student, bench top or mid size and research. The three size differ in price, capability and illumination. Bench top and research microscopes are Kohler illuminated while most student microscopes use diffusion illumination. Student microscopes are the smallest and least expensive of the three. While student microscopes can be used for advanced techniques and documentation they do not do these things with ease or grace. They are designed for bright field and phase and to be used by students. This means that they have to be rugged and simple to use.

Student microscopes are sold primarily to schools, no surprise there. They also make very good doctors office microscopes since they are simple, rugged and cheap. If you do not need high performance and ruggedness is very important consider a student microscope. The prices start at $900 to and go up to $2100 depending on equipment and the quantity you buy. Dealers usually get a better price break on student microscopes.

Bench top microscopes are used in every imaginable discipline. From textiles to animal husbandry the bench top is the work horse. Bench tops can do just about any technique you can think of. The difference between a bench top and research microscope is how many techniques they can do at one time and how many documentation devices they can use at once.

A bench top can do all the techniques you can think of but you might have to disassemble it to but on new modules. If this isn't a problem a bench top is a very good idea. If you are going to be doing only one technique and not a lot of documentation then a bench top is ideal. Modern bench top microscopes try not only to be modular but very easy to use. More and more we are seeing bench top microscopes add ease of use features like very low set control positions and tiltable heads. These features are there to make the user more productive.

Research microscopes are big. I mean big as in large as in heavy as in... well you get the idea. A modern research microscope will weigh in the range of 30Kg. to 50 Kg. This mass is composed of big optical systems, big mechanical systems and lots of electronics. These behemoths can use multiple cameras, large specimens and the widest range of simultaneous techniques. Most have built in computers to control the cameras and other functions including focus. If you are doing particularly demanding work or if you do a lot of documentation then one of these is in order. While they are expensive they can do what no other microscope can do. However a bench top may do all you want to do for a whole lot less money.

What this means to you

The two basic types of microscopes are stereo and compound. Inside the compound group are inverted and upright. There are size categories in both groups that balance money and performance.

A. Resolution

What does a microscope do besides take up space on the counter? The standard answer is that a microscope magnifies small objects.Like so many standard answers this one is wrong. A microscope reduces the angle of view of the observers eye thus improving the resolution of the observer. So there! Resolution is a much abused and misunderstood word so lets take a long look at it.

Resolution is the ability to distinguish two points as two points. For instance if you look at a red brick wall from a distance you will see a reddish object and think "A hah a brick wall". However you don't know for sure that it is a brick wall until you get close enough to see the mortar lines and the bricks. At this point you have resolved the bricks and mortar.

In a microscope a lot of resolving power in the system would let you see bands on chromosomes, small bacteria or granularity in a blood cell. Since these are very small features from experience we know they can only be seen with a high power objective. Doesn't this mean that magnification is resolution? No, magnification is not resolution.If you increase the magnification of the microscope with out increasing the resolution you get a big fuzzy image not one with more detail. We will learn more about this later.

The word resolution has been used in microscopy as a synonym for good when what it is a quantifiable factor. The sole and only determinate of resolution in a microscope is the numerical aperture of the objective. Numerical aperture is printed on each objective and is found in the manufactures literature.

Lets take a look at this bold assertion of the relationship between numerical aperture (here after called N.A.) and resolution. To understand this we need to know a few things about light. Light is mysterious and wonderful stuff. It appears to act in two ways as a wave effect (like sound waves) and as a physical or quantum effect (like electrons). When we think of light as a wave effect it is much easier to see how lens systems work. However light as quantum bundles makes photo-electric effects such as photo meters understandable.

People interact with light in several ways. We can see changes in light intensity and most of us can see color.Color is the way our eyes show us the difference in light wave length. A wave length of light is the distance from one end of a light wave to the other. The average human can see from around 400 nanometersto around 700 nm. The nanometer (nm) is the usual measure of the length of a light wave, light waves are very small.The eye see 400nm light as very deep blue and 700nm light as bright red. Because the wave length at 400nm is shorter than at 700nm and the velocity of all light is the same 400nm light has more energy. This will be important in fluoresence.

When light strikes an object several things happen. If the object is transparent then the light will be transmitted through it but will be reduced in amount by absorption. Colored transparent objects allow only the wave length (color) that it contains. This produces the intensity changes and color changes in a specimen. If we look at the light passing through a specimen we see that if the light passes through a homogeneous substance, like a mounting medium all the light in that area will travel the same distance.

Well what has distance to do with it? Since light slows down in different substances based on the refractive index of the material two waves going through closely spaced points of different refractive indexes will appear to have travelled different distances. One wave will be at a different part of its cycle than the other one.

This difference in light travel time can also take place if the light has to go through thicker or thinner materials. This is how a lens works. The lens bends light based on the thickness or the lens. A lens thick in the center will bend light toward the center and away from the thin edges. Lenses that are thick at the edges will bend light towards the edges. The amount of bending is based on the curvature of the lens and the material it is made of. Refractive index is the measure of how much the light will bend when passing from one material to another. Air has a refractive index of one (1) while immersion oil has a refractive index of

1.512. This is why oil is used, its high refractive index can bend the light towards the lens better than air.

This is commonly seen in fluorescence instruments when the fluorescence cube is removed. The image goes very slightly out of focus. This is because the light now has less distance to travel based on the refractive index of the filters. The tube length of the microscope is now less than before so it must be refocused. Many manufactures have non-fluorescence cubes, called zero cubes, to correct for this.

Light does something strange when it hits a thin object, it diffracts or bends around the object. Lets use this as an example, we take a slide and coat it with a material that leaves a lot of very, very tiny holes in the coating. Then we look at it with our microscope. What do we see? Well a lot of little tiny holes and faintly around the holes we see rings of light!These rings are the diffracted light that has angled itself away from the main column of light passing through the hole. The very thin edges of the hole have caused the light to diffract. Lets count the number of rings that we see and then change objectives to one with a higher N.A.. What happens? We can see more rings around the holes!

Rather than keep calling these things rings and light columns and such lets refer to the rings as diffracted orders of light and the center undiffracted light as the zero order. We can then number the diffracted orders 1 through n.

Why is diffraction so important? Well in a microscope diffraction is the mechanism that creates most of the image. The more diffracted orders the microscope can take in the more resolution. Because of this a microscope is referred to as a diffraction limited optical system since the availibilty of diffracted light limits resolution. The angle that the lens can accept diffracted orders is the angle or acceptance.Numerical aperture is defined as sin (1/2 (A)) were A is the angle of acceptance of the lens. Numerical aperture we can see the amount of diffraction that the lens can take in and process. This is true for a lens with air between it and the specimen. If the lens is designed to use oil you need to multiply that times the refractive index of the oil.An immersion objective is designed from the ground up, you can't improve a dry objective by immersing it.

Ernst Abbe the famous optical physicist and the first scientist at the Carl Zeiss Works took all this information and formulated a single formula for the resolution of a microscope.

R = L/na(cond)+na(obj).

Were R is the resolution in microns (spacing between resolvable objects), L is the wave length of light, na(cond) is the numerical aperture of the condenser and na(obj) is the numerical aperture of the objective. It is assumed that the na(cond) is always less than the na(obj).

From this equation we can see that there are very few ways to control the resolution of a microscope. We can lower the wave length of the light used but quite soon we will go into the invisible Ultra-violet range and we won't be able to see. The only practical way to increase the resolution of a microscope is to increase the N.A. of the objective since the N.A. of condensers is quite high.

But.... we all know that 100X objectives have more resolution than 4X's so what gives. What is going on is that the equations used to produce objectives show that it is easier to produce high magnification, high N.A. objectives. However high N.A. low magnification objectives are made, they are just very expensive.

But what is this about the condenser in the equation? Well if the light source can't produce the diffraction that the objective accepts then there will be less resolution. Think of the condenser as an objective and you will be real close to what it is. So the N.A. of the condenser and the centration of the condenser matters.

The equation shows that half the resolution potential of the microscope is generated by the condenser. By using Kohler's system of illumination we place the condenser at the optical center of the system and at the correct planar relationship to the specimen and objective.

B. Contrast

However resolution is not the only thing that is necessary to generate an image we can use. We need contrast. Contrast is the difference between the brightest point in the image and the darkest point in the image.A human on a very bright, sunny day can see a difference of 500 or more to one. If there is to much contrast in a scene you will have trouble seeing into the bright areas (called highlights) or in the dark areas (called shadows, no surprises here!). Contrast is rated by its range; ie. 1 to 100 gives a 100 times light to dark range.

Contrast is particularly important to microscopists because biological specimens are very low contrast. A well stained specimen my have no more than 12 to one, an unstained specimen may have 1 to 3 or less. Without contrast our brains can't use the resolution information, the image appears "flat" at best and invisible at worst.

To control contrast we use the condenser diaghragm. This diaphragm reduces the N.A. of the condenser and increases the contrast. This is a trade off, if you have some other way to increase contrast, electronic imaging or optical staining for instance, you can use the condenser wide open and get the best possible resolution. If not trading some resolution for some contrast is a good idea.

Contrast can also be viewed as the relative intensity of the zero order versus the diffracted orders. This reduction along with phase angle shifting of the light is the basis for optical staining techniques (also called contrast enhancement) such as phase contrast and Nomarski.

To understand phase angle shift lets look at a wave of light and see what happens when we add another wave to it. If they are at the same phase angle, in phase, they add up and the light becomes more intense. This is constructive interference. If they are 180 degrees out of phase they cancel each other out and the intensity is zero. This is destructive interference. At a quarter wave length out of phase there is constructive and destructive interference.

When the zero order light is shifted by a quarter wave length then when it encounters the diffracted orders it will set up a constructive and destructive interference with them.This effect and the reduction in the intensity of the zero order light is what produces the contrast enhancement in the phase system.

C. Depth of Focus

As we lower the total N.A. of the system another thing changes, more of the images depth is in focus. Try this; get a really poorly prepared histologically prepared specimen since your work is not bad enough for this experiment go borrow one from the turkey down the hall. Examine it with a 10X objective and then with a 40X objective. At 10X you didn't have to refocus when you saw all those folds but at 40X only a very small part of the folds were in focus.

The part of the folds (call it depth of Z axis) that is in focus is the depth of field. There is more of it with a low N.A. 10X objective than with a 40X objective. Now while using the 40X open up the condenser diaphragm all the way. Now slowly close the condenser diaphragm.See, the depth of field increases as you close the condenser diaphragm.

Depth of field can be approximated by the equation : DF = 1/N.A. of the objective. Were DF is depth of field and n.a. is the numerical aperture of the objective. This equation has some caveats however. If the N.A. of the condenser is reduced the depth of focus increases and if the working distance of the objective is increased the depth of focus increases.

D. Working Distance

Working distance is the distance from the front of the objective to the specimen plane. Usually the higher the N.A. of the objective the less working distance. However Olympus in the mid-70's increased both working distance and N.A. with its S Plan series of objectives. There are, however, limits to how much working distance can be had with how much N.A..

Working distance is important in a microscope to keep objectives away from the specimen or what is around the specimen, like oil. Since we all know that "high, dry" is neither why aren't all objectives made with as much working distance as possible?

The limits are objective N.A. and cost. It is possible to increase working distance but the cost is complexity. Some objectives for industrial purposes have enormous working distances but their cost is very high. The manufacturers publish the working distance of their objectives in their literature.

E. Immersion

This still doesn't explain oil objectives. Do we really have to use oil? Why do we have to use oil? Is this a conspiracy to keep oil makers in business?

If the objective is designed to use oil you must use oil to get an acceptable image or an image at all. What oil does is provide an improved channel for the image to travel between the specimen and objective. The characteristic we look for in an oil to do this is the index of refraction.

The index of refraction is the ability of material to bend light. Mineral oil has a higher index of refraction than water for instance. Air has an index of refraction of one while standard immersion oil is 1.55. This means that immersion oil will funnel more of the diffractive orders from the specimen to the objective.

Practically this means that the highest N.A. that can be achieved with air between the objective and specimen is 1. In practice the highest commercially available N.A. in air is .95. The highest commercially available N.A. with oil is 1.4. This is a 32% improvement!

Oil has another advantage, simplicity of use. Yes I know about the mess oil makes. I repair microscopes, believe me I know! The problem is with high N.A. 40X-60X objectives. If N.A. exceeds .8 then the cover slip thickness becomes very critical. To adjust for this the manufacturers build a cover slip compensating collar on to the objective. This must be set correctly or the image will be poor.

This is the trade of with high performance mid-range objective, oil or compensating collars. Look at it this way mess or time. Of course cost raises its ugly head. Oil objectives are easier to build than high performance dry objectives.

F. Magnification

Now that we understand resolution we can discuss the less important area of magnification. The total magnification of a microscope is the magnification of the objective times the magnification of the eyepiece times the magnification of any intermediate modules (if any). For example using a 10X objective and a 10X eyepiece and no intermediate modules will yield a total magnification of 100X.

So why not use 100X eyepieces and get 1000X total power? It could be done. In fact magnification is cheap to produce, resolution is expensive.

Well what you would get is a big fuzzy image. Eyepieces don't improve resolution. As we have seen only N.A. improves resolution. A good rule of thumb for visual observation is that the total magnification of a microscope should not exceed 1000 times the N.A. of the objective in use.

If we are using a 100X oil with a N.A. of 1.25 with 10X eyepieces we have a total magnification of 1000. Since this is significantly less that 1000 times the N.A. of 1.25 (1250) we should expect to have a very pleasant image. If we are using a dry 100X objective (these are made!) with an N.A. of .95 (950) we would expect the image to look fuzzy.

G. Parfocality

A modern microscope must have the ability to change objectives easily.In the very early days of microscopy the user unscrewed the objective and screwed in another. With the advent of the revolving nosepiece parcentricity and parfocality became important.

Parfocality means that the specimen stays in focus when the objective is changed. To judge this correctly the microscope is properly set up and then focused at high power. Then switch objectives to a low power and see how much focusing is necessary. Because depth of field is greater at lower powers parfocality is always judged from high power to low. A good microscope will require very little focus knob movement.

If you are using achromats or other curved field objectives remember to judge parfocality only in the center of the field. Parfocality is very influenced by the set up of the instrument. If the eyepieces, in particular, are not set up correctly parfocality will suffer.

Parfocality can be adjusted on most microscopes by the user or, at worst, a service person. Usually all that is required is to properly set up the eyepieces. Some times adjustments must be made to the eyetube mechanism. Leave that to a qualified service person. If parfocality can't be corrected the odds are that a bad objective is to blame.

Sometimes parfocality is corrected by a service person installing thin brass rings called shims between the objective seat and the nosepiece. This is to adjust the tube length of the microscope by extending the objective a very small amount. You can only shim an objective down (extend the tube length) not up. Shimming should be viewed as a desperate last gasp, a band aid solution not a true fix. When an objective is shimmed it no longer sits quite flat on the nosepiece.This can cause a loss of of parcentration. Brass shims are used because brass adapts to the objective seat and nosepiece the best of any material.

A service person who shims all objectives, uses other than brass shims, excessively shims or tries to adjust parfocality by screwing the objective on very tight just doesn't know what they are doing. At most one less than the total of objectives will have to be shimmed. If a lot of shims are required (more than 3 or 4 thick ones) then it is proof that the objective of microscope has sever problems that requires attention not a band aid.

H. Parcentricity

Parcentricity means that an object in the center of the field will stay in the center of the field no matter which objective is being used. To test this set the microscope up properly and find an identifiable object at high power. Switch to each objective in turn and see if it is in the center.

If you have performed Kohler illumination correctly you can close the field diaphragm and observe the image of the field diaphragm's position in the field of view. It should stay in the center of the field. Any deviation is a loss of parcentricity.

There will be some variation in the field center objective to objective. To be acceptably parcentric the center of the field should not vary more than one third of the field of view; ie. if the object is at the center with one objective it will not go out side the inner one third of the field of view with any objective.

Sometimes parcentration can be corrected by a skilled service person but usually parcentration problems are

caused by a bad nosepiece or is inherent in the construction of the instrument. Parcentricity is based on the design and manufacture of the nosepiece, mainly, and is a good indication of the general quality of the instrument.

VI. Conjugate focal planes. Were is it anyway?

How often have you seen a dirty smudge through the eyepieces and had a hard time finding it to clean it? Probably a lot. Because a microscope is a convergent-divergent instrument with conjugate focal planes tracking dirt can be a problem. Of course so can the those long words we just used.

A microscope is a convergent-divergent instrument as opposed to a parallel or infinity instrument. In an infinity instrument all light rays are parallel to each other and the optical center line of the instrument. In a microscope light rays are moving towards the center line (converging) or away (diverging) from the center line at all times. Even "infinity corrected" objectives do this.

This sets up a series of locations in the microscope were things will be in focus. At the top end of the microscope the image is in focus at our eye's retina. However if we looked at our own eye's lens (don't ask me I don't know how) we would see an image of the lamp! These are the conjugate focal planes, the retina and lens planes.

If an image is in focus when another image is in focus then it is conjugate to it. For instance if a microscope is set up correctly using Kohler illumination then when we close the field diaphragm it will be in focus along with the specimen; the field diaphragm and the specimen are said to be conjugate to each other or in the same conjugate plane. That conjugate plane is also occupied by the diaphragm of the eyepiece. This is were we put measuring reticules so they will be in focus along with specimen.

So what does the lens conjugate plane do? Well it generates the information the retinal plane sees. If we remove an eyepiece we will see the lens planes components, light source, condenser diaphragm and objective back plane.

In some microscopes you will see the filament of the lamp in the field. Most microscopes use a diffusing filter to diffuse (fuzz) the filament image so that low power objectives can be used. Even if you can't see it the filament of the lamp it is the first lens conjugate plane.

The next plane is the condenser diaphragm. To observe the condenser diaphragm remove an eyepiece and open the condenser diaphragm all the way. Now close it slowly. You will see it reduce the illuminated area in the objective back plane.

When you have reduced the maximum size of the illuminated area by a third to a half replace the eyepiece and observe the specimen. The contrast will have increased from when the condenser diaphragm was fully open. This is a very good way to set the contrast of the microscope for an objective.

While we are seeing the condenser diaphragm change we are actually seeing the back focal plane of the objective. The size of the fully illuminated area will vary by the N.A. of the objective. This means that a one third to one half reduction is individual to that N.A.. This method of setting contrast is great for photography and all forms of documentation.

There are other uses for the lens back plane. Geologists observe cross polarized specimens at the back focal plane using a Bertand lens. This is called conoscopic observation. While biologists haven't used this to any extent you never know what will be used next.

What Kohler did by defining these planes (this is the why of Kohler illumination) was to place the image of the lamp were it would do the most good. The lamp is brightest were it is in focus, so focusing it just before it goes through the condenser makes it the brightest.

Why don't we see these all at once? Well we do but we see the lens conjugate plane as an effect and the retinal plane as the image. Like dirt on our glasses we can't see the lens conjugate plane but it affects us.

This also makes dirt hunting easier. If we can see the dirt we know that it has to be conjugate to the plane we are see. For instance if we can see a blob of dirt we know that it can't be on the back of the objective since that is not conjugate to the specimen. We also know that it can't be on the front of the objective since that is not conjugate to anything.

A lot of dirt that we see in a microscope is on the lens covering the field diaphragm. This is near enough to a conjugate of the specimen that the depth of focus of the condenser will bring it in focus. Clean this area with air or with methanol and Q-tips. What this means to you Conjugate planes are parts of the microscope that are optically the same. Knowing what is conjugate to what helps us to find dirt and properly set up the microscope.

VIII. The Microscope Industry

To be profitable in the increasingly competitive world of commercial microscopy makers have to be more productive. To do this they have to design microscopesas modules. This means that a module, such as a frame, can be used by a wide range of disciplines. If a manufacturer is designing a frame they want that frame to be used in industry, research, bio-med and any place else they can sell it. To do this they must design it to take a wide range of accessory modules.

What this does for the manufacturers profitability is to bring the economics of scale to microscopes. The more frames that can be manufactured at a time the less they will cost since manufacturing set up costs will be reduced for each module produced. The key to profitability for manufacturers is modularity. The days of making one instrument at a time are, thank goodness, over.

Manufacturers don't make fluorescent or phase microscopes they make modules to add on to there frames to do these techniques. If you call a microscope representative and ask for a "phase microscope" it is admitting ignorance. The correct way to discuss a microscope with a rep. is to hit them with a stick. No, not really (well maybe just a little). What you want to say is " I want to see a bench top (or research) frame equipped for phase".

Professionals in the microscope business quit thinking in term of phase microscopes, etc, years ago. A pro today thinks in terms of the modules the manufacturer makes and how they all work together to provide the techniques the user wants.

Modern manufacturing techniques make microscope modules totally interchangeable. When you order your bright, shiny, new microscope the microscope representative goes into their warehouse and assembles your microscope by pulling parts from bins. There is no need to custom fit modules to other modules. Installing a microscope now is just a matter of opening boxes and clicking parts together. No tools needed and not a lot of brains needed either, thank goodness.

This means that when you want to add a new module for a new technique the module will fit on you instrument with no adjustment. Just snap the module on in the correct place and your in business. Installation in the commercial world is considered the simplest job around, the tough jobs are sales, training and repair.

The only drawback to all of this in some users eyes is the perceived lack of quality in modern instruments versus older instruments. As a repair person and a pro in the microscope business I'm here to tell you that it just isn't so. The older instruments can be very well made and in many cases just plain beautiful to look at but they can't compete with the best of todays microscopes.

Modern materials, lubricants and machine tools make an instrument that should last fifteen years or more as a front line instrument. Not only that but if will be able to be upgraded to a whole host of techniques that the older instruments can't be. The precision of machining on modern microscopes makes a much more accurate instrument.

A good example of this is shimming, placing thin metal washers between the objective and the nosepiece seat. This used to be common practice when installing a microscope but you should not have to shim a modern objective. If you have to then something is wrong and the manufacturer will (should) fix it under warranty. Modern interchangability means that any objective will work with on any place on the nosepiece and modules don't have to be custom fitted to each other. This used to not be true. In the old days you had to remember which objective went in which nosepiece place to make the microscope parfocal and parcentric. If you disassembled an instrument you made sure that it went back together the exact same way (say a multi-headed microscope). That isn't true of a modern products.

The optical quality of the modern microscope is better. Contrast levels are higher than ever and resolution is

increasing while prices are decreasing. There are more types of optics for more applications than ever. Field of view has increased and users can realistically wear their glasses.

Markets

The microscope market place is roughly divided into the bio-med, industrial and geology markets. Although the frames may be the same across markets the optics and accessory modules change. Each market has its defining uses and sales requirement.

The bio-med market includes the student, clinical and research sub-markets. Each of these sub-markets has its own needs. In the student market the microscopes must be inexpensive and durable. In the past most student microscopes were sold with a monocular head but, thank God, that is changing. A student microscope now has a binocular head and is diffusion illuminated.

The clinical market is one of if not the biggest dollar volume markets. A clinical microscope will have a reversed nosepiece on a desk top frame. They are always binocular and Kohler illuminated. Typical accessory modules include phase or fluorescence. Nikon and Olympus dominate this market, their prices are very close together.

Bio-med research microscopes range from the high end bench top to the large frame research microscopes. Typically they will have at least one camera. It is not uncommon for a research microscope to have a TV. camera mounted on it for documentation and image analysis.

The industrial market is divided into semi-conductor, electronic and metallurgical. Semi-conductor microscopes are used to perform quality control and manufacturing procedures on semi-conductor chips. These chips are manufactured as wafers and the wafers are then cut apart. The microscopes must be able to handle up to eight inch wafers in an ultra-clean environment.

The requirements for a semi-conductor microscope are to provide an good image, allow precise control of a huge stage and keep the user from contaminating the wafer. The circuitry on a semi-conductor wafer is so small that the least little piece of dirt will destroy that chip. The user must be able to use the instrument and be productive, in a manufacturing plant time is money.

To achieve these goals manufacturers have come up with some innovative modules. The universal illuminator lets the user switch between Nomarski, dark field, bright field and fluorescence with just a push of a lever. Ergo heads let the user adjust the angle of the head to accommodate users of all heights. Wafer stages move the specimen with out scuffing it across the stage.

Semi-conductor microscopes for wafer work are equipped with reflected light modules since wafers are opaque. The objectives used span a wide range from very high performance, short working distance to medium performance ultra-long working distance objectives. Long working distance objectives are used were probes are used to test the chip. The operator controls the probes using the microscope to observe the process.

Mask microscopes are not used for Halloween but to look at the masks used in the manufacture of wafers. These are as large or larger than wafers and are transparent. A mask microscope will be equipped with a wafer stage cut out for transmitted light. Reflected light objectives are used since no cover slip is used on a mask.

Stages for a semi-conductor microscope must be large enough to accommodate the wafer being processed. Frequently these are motor driven and computer controlled. All wafer stages must be precise but the motor drive ones must be precise and repeatable. The stage must be able to go from place to place with accuracy since it is very easy to get lost with todays complex wafers.

Electronics market microscopes are used for a broad range of circuit board and hybrid chip work. These instruments range from stereo microscopes to compound microscopes equipped with lasers. These systems are much more popular and much more developed than a few years ago, look for a lot more development.

The most common microscope in this market is the stereo. It is used to look at drills that make holes in circuit boards, the holes themselves, help the user control test probes and just about everything else in the manufacturing process. Frequently the stereo will be built into some other piece of test or manufacturing equipment.

When a manufacturer buys a microscope to be used in their equipment they are referred to as the Original Equipment Manufacturer or O.E.M. for short. O.E.M.'s are beloved by microscope manufactures since they require no follow-up service. The manufacturer just delivers the microscope and leaves.

Metalurgical microscopes are used in the metals industry and in other types of materials research and quality control. It used to be that only metallurgical microscopes were used only for metals but with the explosion in materials research they have found a home in many other labs. The metallurgical microscope is usually inverted and equipped with reflected light only.

Geology microscopes always have polarization. The optics of a geology microscope will be designed from the ground up to be used in a polarizing system. Typically a geology microscope will have a rotating stage and centerable objectives.

Bio-med and geology camera systems are almost always 35mm. Bio-med users want slides to illustrate lectures, print making for poster sessions and publication. A slide is best for these purposes. Industrial people use Polaroid and increasingly video printers. In industry photos are used for quality control verification and immediate reports. Polaroid or video printers work best for this. What this means to you

In the microscope market place there are a number of markets and sub-markets. Each one requires a different set of accessory modules however these modules will fit on most microscopes.

Manufacturers, who are all these tacky people anyway?

The manufacturer is the single most important force in the microscope business. No manufacturers, no new microscopes and one heck of a lot less fun. There are only four manufacturers that are in the top rank, these are Carl Zeiss, Leica, Nikon and Olympus.

All of these makers make excellent microscopes. The difference is in price-performance trade-ofs that only you the customer can judge. These manufacturers all produce quality goods.

Carl Zeiss and the E. Leitz component of Leica are mostly German made. They tend to be more expensive than the Japanese made Nikon and Olympus. Sometimes they are worth the extra money and sometimes not. In the bio-med market Nikon and Olympus are the real powers. In very high end research Zeiss and Leitz hold sway. This is not absolute, each maker has strengths and weakness in each area of the market place.

Olympus

Since I worked for Olympus dealers for most of my work life I'll start with Olympus. A Japanese maker, Olympus makes optical equipment, pocket tape recorders and bio-med analyzers among a wide range of products. Their optical goods include microscopes and cameras. Olympus is known in the trade for rugged and elegant mechanics and excellent optics.

They are also very conservative and tend to be slow in introducing new products. Although once they decide

to bring out a new line they have everything ready then, not months from now. In my experience Olympus makes very rugged microscopes though not the flashiest. Olympus tends to be strongest in the bio-med markets in America.

Olympus, Tokyo owns Olympus, USA who distributes product to the Olympus dealers. While Olympus USA has a lot of strengths they have a lot of weakness's. Their primary strength is a disciplined dealer corp and a strong pricing policy that focuses the sales effort on the product not on price competition. This should breed a technically competent sales corp.

In my experience it hasn't. The primary weakness of Olympus is its technical training. This is odd since they have as a consultant on of the best microscopist going, Mortimer Abromowitz. He's not only good he can write, in English no less. However Olympus has very spotty training for its personnel and little to no requirement for dealer personnel training.

Service is another weakness of Olympus. They don't really have an authorized service program and they have no in field service personnel. Couple this with a poor parts supply system and its a good thing that Olympus microscope break so infrequently. I wish Olympus would get a service and training program that is as good as their instruments.

The new Olympus BX line of bench top microscopes is the class of the field in the bench top area. The BX uses infinity corrected optics, very low set controls, ceramic stage tops, wide field eyepieces and a complete set of modules for all purposes. Olympus claims that they are going to continue to make their older BH series of microscopes at the same time as the BX. I find this hard to believe. The BX is better for all purposes and shouldn't be all that much more to make if any. If you like Olympus buy a BX.

The Olympus CH series student microscope is the class of the student field. While it can take a wide array of modules it is best as a binocular bright field student microscope. This microscope is the most sturdy microscope out their. It is diffusion illuminated so it is easy to use. Also it is an excellent doctors officer microscope.

In the inverted market Olympus makes two very good microscopes the small CK II and the research size IMT II. The CK II is great for routine tissue culture checks, it is simple and it works. The IMT II is an excellent choice for a research inverted. It has built in positions for a 35mm Olympus camera and a general purpose port. The frame accepts all Olympus heads so another camera can go on top.

Nikon

Nikon has the widest line of microscope products in the U.S.. Besides microscopes and cameras they make wafer handling stations and pattern projectors for industry. Nikon makes modules for their frames that do just about everything. Its hard to think of a technique they don't sell a module for.

A Nikon dealer has a lot more lee way than any other dealer. Nikon wants their dealer to sell microscopes and not get into discussions about territory. While this should breed a high pressure, non-technical sales person I haven't seen any real difference between the competence of the Olympus and Nikon sales forces.

Nikon has an authorized service dealer plan and an decent parts department. While the service dealer plan is not as strict as Leica's it works. Training for factory direct personnel is adequate. There is some training for sales persons every year. Training for factory service persons appears to be excellent.

In the past Nikon's sales strength was in industry and Olympus was in bio-med. With the introduction of the Labophot II line this has changed. Nikon is strong all across the board. The Labophot II and the larger Optiphot II are excellent microscopes in the bench top arena. They both have reversed nosepieces and excellent illumination. Nikon is pioneering stainless steel and ceramic stage tops to increase stage life.

Industrialy Nikon has the most complete line going. The Epiphot metalograph is the standard of the industry. Nikon stereos are adequate and the pattern projectors are excellent. The wafer station, a microscope and a wafer handling system integrated together, was pioneered by Nikon.

Nikon's high end research upright, the AFX, doesn't have all the features of some microscopes but what it has works spectacularly well. The AFX has a built in camera system that can put an identification number on each frame. This is a real help in keeping track of a large number of photographs. The camera has ports for two 35mm cameras and one large format camera and a separate port for a tv. camera.

The Diaphot II, Nikon's research inverted, is an excellent system. It is the successor to the best selling research bio-med inverted, the Diaphot. The redesign of this classic has improved its fluorescence performance and increased its ease of use. The Diaphot was always a rugged microscope and now it is even more so. The TMS Nikon's small inverted is perfectly adequate for routine work.

Carl Zeiss

Zeiss is the oldest intact optical company and the largest producer of optical equipment in the world. The Zeiss plants produce everything from microscopes to the optics used on satellites. As specified in Dr. Ernst Abbe's will the Carl Zeiss company is owned by the non-profit Carl Zeiss Medical Foundation. This corporate arrangement has given Zeiss a longer term corporate world view than other companies.

While always been noted for uncompromising quality Zeiss has also been noted for high prices. Zeiss recently eliminated all of its dealers and now sell through a direct sales force. This has reduced prices to a large extent. How this will go in the future is any ones guess but a good price on a Zeiss microscope is always welcome.

The Zeiss company has always played an important role in the microscope industry. From the time of Dr. Abbe, first scientist and later president of Zeiss, they have been in the forefront of design and manufacturing. Their newest microscope line carries that tradition forward.

An Axioscope looks unlike any other microscope out there. It has a pyramidal frame that helps it reduce vibration and control positions that make using it a dream. Its just so easy to use! The focus, stage and transmitted light controls just slip into your hands while your hands rest comfortably on the table. Couple this with well thought out modules for every technique known to man and justly famous optics and you can see why I think that this is an excellent choice for a high end research frame in the bio-med area.

When Zeiss introduced the Axio line of microscopes they went to an infinity tube length. This improved an already excellent line of optics. However it did orphan the legion of Zeiss owners. Zeiss has been good about keeping the 160mm tube length objective in stock, how long this will continue I don't know.

I get similarly worked up about the IM series of inverteds. These are the class of the field for bio-med research inverteds. The stage is huge and rugged, stand on it if you want, not recommended but you can. The optics available for it can do anything. This is one inverted that can do the whole range of bio-med applications and do them well.

Zeiss pioneered the surgical microscope and are still the sales and technology leader. If you need moderate magnification, good resolution, long working distance and real comfort in a stereo, check out the Zeiss surgical line. They are excellent for forensic applications and applications that require a lot of dissection. The more you use these stereos the more you will appreciate them.

Service and parts at Zeiss are the best in the business. The parts department has very knowledgeable persons to help you. Since the service personnel are Zeiss employees they are very responsive and well trained. Zeiss training has always been the standard of the industry. Part of the pleasure of owning a Zeiss is knowing that

real service is a phone call away.

Leica

Leica is a name you have probably heard before but not with microscopes. E. Leitz company used the Leica name for their excellent line of 35mm cameras. Leica in fact was the first 35mm camera. Now it is the product name for a whole line of products.

Leica is made up of a whole group of historically significant companies. Through a series of mergers and acquisitions that goes back into the 50's Leica is made up of Reichert, American Optical, Bausch and Lomb, Cambridge, E. Leitz and Wild. This may seem like some what of a mish-mash and it is. However this could be the defining company of this decade.

With the acquisition of American Optical (A.O.) and Bausch and Lomb (B. and L.) Leica controls the last American microscope manufacturers. While I feel uncomfortable about this these companies had deteriorated over the last 15 years. We probably will never see the B and L name again, at least on anything good. A.O. has been using the Reichert name since the sold the American Optical name years ago.

Alas the glory days of A.O. were over in the mid 70's. Corporate mismanagement and greed reduced both the great American companies to the laughing stock of the industry. The last American built compound microscope, the Reichert 410, is a hideous hunk of junk. Were the A.O. plant used to produce elegant, bullet proof microscopes they now produce a microscope so bad I can't in all good conciance recommend anyone purchase one.

However the rest of the Lieca plants produce spectacular products. Maybe we will see a reniesance of the American microscope led by the E. Leitz and Wild plant. The work force is in place at the old A.O. plant, all they need is leadership.

E. Leitz has always been know for quality. Their large frame research microscopes have been the known for superior optics since the late 1800's. There present line includes new computer controlled microscopes that will change the way we think about the research microscope. If I needed a top line, totally versatile research microscope for a wide range of uses and documentation techniques I would be very tempted by the DM (Das Mikroscop) line from Lieca. The most amazing thing about this microscope is its price. The price for all this capability is really quite low, right with Nikon. What a deal!

Wild has always produced the best stereos. If you are a serious user of stereos you need to take a look at a Wild. Of course if you are a serious stereo user you probably have a Wild. Other companies make good stereos but Wild makes the widest range of stereos with the widest range of accessory modules. They are ruggedly constructed and a delight to use.

Reichert is a company we don't see a lot of in the states except for the Reichert-Jung microtomes. Reichert, an Austrian company, for years was the research microscope producer for A.O.. With the Univar microscope they set new performance levels for research microscopes. The Polyvar research microscope has been a standard of excellence in semi-conductor research. Reichert's big winner is the Mef-3 metalograph, a do everything microscope that is easy to use, optically superb and incredibly expensive.

If this product line sounds like it overlaps, well it does. The industry is watching Leica to see how they will re-organize these talented plants to be their most productive. I would bet that over the next five years you will see a proliferation of new, innovative products that blend the talents of this world wide company.

In America they have gone a long way towards resolving overlaps and redundancies. The dealer network is strong and committed, like no other dealer group, to technical excellence. Service and support is as good or better than Zeiss and that's saying a lot.

Leica dealer service persons are the best trained and backed in the business. Parts support in the past has been spotty due to the problems of integrating all the products into one parts system. I feel certain that this will be resolved. If you have a problem with a Leica product you will get support not talk.

Other makers

The big four makers are the best known but there are other makers of microscopes. Of these the only one that makes anything worth while is Unitron. This Japanese manufacturer makes excellent inverted metallographs and a very good stereo, the ZST. However the rest of Unitron's line is poor. If you are in the market for a stereo or an inverted metalograph then check into Unitron. There prices are very good, the optics are fine and there are a lot of them out there. However there is little factory support and almost no parts.

Junk

There are a lot of microscopes out there that I haven't mentioned. That because they are junk. Usually they are an "importer trademark" microscope. This means that the importer goes the manufacturer, located God only knows were, and buys a microscope based on a low price. There is no consideration of materials choice, optics or any of the other things that make a good microscope. Bausch and Lomb is now an importer trade mark microscope. This is a real shame. The present B and L is made in China and is a blot on a great name. The persons responsible for this disgusting marketing ploy should be ashamed of themselves.

Other importer trade mark companies include Swift and the Fisher trade mark microscopes. Stay away from all of these microscopes. They aren't cheap, they perform poorly and there is no factory support. Importer trade mark vendors don't have parts or repair programs of any value. Buying these microscopes is false economy or no economy at all.

Some junk microscopes bear there own companies logo on them. Avoid them none the less. If it isn't made by Nikon, Olympus, Zeiss or Leica (with the exception of the 410) then don't buy it. Quality in a microscope comes from excellence in design and construction. These junk makers are at best copy cats who can't do it right or quick buck artists. What this means to you

Buy only products from Nikon, Olympus, Zeiss and Leica. Unitron makes a good metalograph and stereo. Other brands should not be considered.

How the microscope market works, or doesn't

This is how the microscope business works as opposed to how a microscope works. The microscope business is based on a three tier marketing system. The manufacturer sell to the dealer who then sells to you. Theoretically this leads to a very efficient system were each level does what it does best. It looks great in marketing books anyway.

All manufacturers except for Zeiss which sell directly to the customer have dealers. A dealer has an assigned territory that they are supposed to sell in and not sell out of. There may or may not be other dealers for the same microscope brand in the territory. Each manufacturer has a different territory structure.

A territory with no other dealer for the same brand is called an exclusive territory and it is what all dealers want. Dealers are not supposed to sell outside their territories but frequently do. Its just hard to turn down a sale. Of course the manufacturer expects something from the dealer and that's lots and lots of sales.

All dealers have quotas, a dollar number and in many cases a fixed number of frames that they are required to sell. A dollar amount would seem obvious but the frame volume is an important number to the manufacturer. If the manufacturer knows how many frames the dealers have to buy as a minimum then they know how many to make. Experience will show how many accessory modules and of what kinds to build.

What the manufacturer wants to do is let the dealers do all the stocking of microscopes and what the dealer wants to do is stock as little as they can get away with. This is particularly true if the dealer is financing their stock. Microscopes have a good profit margin but a slow times turn rate.

The times turn rate is the number of times in a year that you sell your inventory. When I worked for a computer wholesaler we turned our inventory about 24 to 30 times a year. That's at least twice a month. Somethings we turned 3 to 4 times a month. That's a very good number. With that high a turn rate we could afford to reduce our profit on each sale and literally make it up on volume.

A microscope dealer may have a 1.5 to 3 times turn rate per year. That means the stock is sitting around a long time. If the dealer has financed the stock each sale will have a lot of finance costs attached to it. The way out of this slow inventory turn rate is to have less inventory. But the manufacturer has the same problems so they don't want to stock in large amount either.

Now here's the rub, if the dealer doesn't have it and the manufacturer doesn't have it then the customer waits. The customer then gets ticked and cancels the order or tell everyone at a national meeting what a group of losers this brand is.

Just to make it more interesting lets throw in production scheduling. Not every part in the dealers price list is made all the time, some of them aren't made at all. Some items are only made at one time of the year, this is called a "run". If the dealer doesn't have an item and the manufacturer doesn't then you wait for the next run. This is a problem with exotic parts. An experienced dealer knows what parts they must stock to prevent shortages.

One way around shortages is to call other dealers and see if they have any extras they want to sell. It is common for dealers to sell to other dealers at 5% to 10% over their cost. They make money and move goods and keep up good relations for when they need something. If the item is rare and in demand the dealer may want to keep it for themselves and make the higher markup selling to and end user.

To sell all these microscopes the dealer is required to hire sales people. This is the coverage issue. A sales person is an expensive proposition. The usual deal for a dealer sales person with experience is a car allowance, insurance, expenses and one third of the profits of each sale in the sales rep.'s territory. Sometimes a base salary is paid and the commission reduced but the compensation package will tend to be in

this ballpark.

It's hard to get experienced sales people and it takes a long time to train an inexperienced one. The costs to the dealer are high and getting higher. The manufacturer wants to see the dealer people calling on every account every day. The dealer wants good coverage to but the dealer pays the bills. This is why the dealer wants an exclusive, costs are high and the dealer needs to keep the profit margin up.

Just to make it more fun for the dealers the manufacturers have their own sales people out in the field. These are called "factory" or "factory direct" sales persons. Theoretically they are supposed to help the dealer's sales people. Ten years ago the factory people were supposed to be more technically competent. Now they act as an alternative sales force and a way for the manufacturer to take a sale with no profit to the dealer.

This is called "sell direct" and it is the nightmare of all dealers. For what ever reason the manufacturer can bid against the dealer and take the sale away from the dealer. They may do it to make a sale they otherwise wouldn't have gotten by giving a price that the dealer couldn't afford to give. They may do it as a demonstration of who is really important or the factory person may have done all the work and deserves the credit for the sale.

If a manufacturer makes a sale the dealer may still get a percentage. Olympus contracts give the dealer the same percentage of the factory direct sale that they would make if they had made the sale. Of course if its under there profit margin then there is nothing to split. Nikon may of may not give the dealer anything, it just depends. Leica is all over the place but they have very few factory people.

Buying a microscope

Here's the scene, the long awaited money has come through and you are all set to buy the microscope you've needed for so long. Now how do you negotiate your way through the maze of specifications and sales persons to get the best microscope at the best price?

First of all you need to know what you need. You need to sit down and write out what you want the microscope to do. This can be as simple as saying "We need a new microscope for a new cytologist" or much more complex for a research application. The needs statement should say what the microscope will be used for. Let the competing manufacturers give you their ideas on how to do the job.

Call up the dealers and tell them that you are in the market, what you want the microscope to do and when you need the microscope. Ask them for quotes and demonstrations. Ask each sales person when they can let you see the microscope they recommend.

When you are dealing with a rep. you should receive professional, courteous service. The rep should call you by your honorific, and always use maam and sir. Just like a repair tech. the sales rep. should know more about the microscope than you. If the sales rep. is rude or disrespectful to you immediately report this to the owner or sales manager.

You need to get the quotations before you start setting up the demonstrations. The quotes should clearly set out what the microscope will be able to do and the cost. Be honest with the sales persons about cost. Let them know the price range you have to be in. Let them know how important cost is; very important or is performance more important. Remember in buying a microscope value is more important than price. A microscope will last at least fifteen years as a front line microscope and probably another ten years as an active part of the lab. If you save a few hundred dollars but the microscope is not as productive you have lost a lot of money. The most expensive part of a lab is personnel, make sure that the microscopes you buy make them as productive as possible.

After looking at the quotes invite the sales persons that sent acceptable quotes to come in and demonstrate their microscopes. It is more than fair to make everyone show up at similar times and show their

microscopes. This is referred to as a "head to head" demo. and if the sales person is confident about their product and interested in serving you they will jump at the chance.

A head to head demonstration is a very good way for you to see the competitive strengths and weaknesses of each microscope. You will also see the strengths and weaknesses of the sales persons and their organizations. The quality of the organization is critical. These are the people that will resolve warranty and service problems. If they don't perform neither will the microscope.

Now you need to prepare for the demonstrations. Find some space for the microscopes. They should be set up so that you can be comfortable and relaxed when looking through them. Help the sales persons to get the microscopes there. Parking and unloading can be a real hassle when you have a lot of equipment to bring in to a building. See if there is an easy way to do this.

Prepare one of your specimens to view on the microscopes. Make them as challenging as possible. You don't want to find out later that another microscope does better with the more difficult specimens. Each specimen should be viewed on each microscope.

Prepare a list of questions that you will ask all the sales persons. Include questions about service, repair, parts availibity and delivery. Make sure the sales person can and will train you and any other users to use the microscope. This includes photography or use of a video camera if it is included.

A demonstration is a very expensive proposition for a dealership. If you want the best price you need to help them keep their cost down so be fair with the companies involved. Be there when a demo is scheduled, give the sales person your full consideration. It is rude and costly to the dealer to send a person out on a demo and then no one is there to see the microscope. Have all the persons involved in the microscope's use there to see the demonstration.

Sometimes the sales person will leave the microscope with you for a period of time so that you can see how you like it. Before you accept the responsibility for the microscope check with the dealer as to their requirements and with your employer to see what their requirements are. Usually this is no problem but you want to know what your responsibility is if any thing goes wrong.

If the microscope is left with you take the time to really try it out. Make sure all the potential users try it to. The purpose of this type of demonstration if for you to see how the microscope wears on you. If you have questions call right then. Don't wait for the sales person to re-appear. If you call immediately the sales person can correct the problem right then if possible. It will also tell you a lot about what kind of service the company really gives. If they aren't quick to respond when trying to sell you something they are going to be a disaster after the sale.

If a sales person makes you a promise that has a direct bearing on your decision to buy that microscope, make the person send you that promise in writing. This is true for any purchase of goods. If this promise is not in writing you may not be able to enforce it in court or arbitration if it comes to that. If the sales person refuses to write it down and asks you to take there word then forget it. All you may be left with is words.

After the reps. have been picked up their microscopes sit down and decide which one would be best for you. Include in your evaluation the ease of use, the performance and the quality of the dealer. Once you know what you want it is time to get the price you want.

You need to know whether you are a bid, contract or private institution. The differences will affect your price negotiations. If you are a private institution you can negotiate the price yourself. If your are a contract institution there will be a contract price available to you although usually this is a floor price, with some negotiation you can do better. If you use bid you will have to know the purchasing rules very well.

Most places use a sealed bid system to purchase microscopes. This can put you at a real disadvantage. The

key to controlling a bid purchasing system is writing the bid specification. If you really want only one brand and model you will have to write the bid specifications so that only that brand will win. Your sales rep. can be a real help in writing what is called a "lock out spec.".

If you don't care what you get then a bid is a good way to drive down the price. Specify the microscope as exactly as possible, use one manufacturers specifications. This helps you to get the features you want and stops the dealers from cheapening the microscope to lower the price. This is a legitimate way to win a bid. It is up to you to write the specs. that will get you the microscope you really want.

Tell the sales reps, whose products you like, that you are willing to buy from them if they win the bid. Make sure you tell this to the dealer whose microscope you didn't spec. Otherwise they might get discouraged. Mostly users spec. the instrument they will accept and reject others.

When the bids come back review them closely and make sure that the bids are apples to apples comparisons and not apples to oranges. If you have any questions have the sales rep. bring in the exact microscope that they bid and take a look at it. If there is a problem then get with purchasing and reject that bid. The key points in a bid institution is to get the microscope you want at the lowest price. You the user must write effective specifications and get purchasing to accept them. Remember that a sales rep. is not going to give you the lowest price on a quote if they know that the microscope will be bid. If they gave you the lowest price on a quote and a competitor found out then the competitor would know what they had to beat. This is a big advantage.

If you have a price contract or you are a private institution you will have to negotiate to get the best price. Price contracts in most areas are the least discount you will receive not the fixed price. If you are a Government account covered by Government Services Administration (GSA) the dealer can't give you a lower price since this establishes this price as the price nation wide. No dealer will negotiate with a GSA account and GSA is the loser for this policy. This, along with the red tape and rapacious tactics of GSA, is the reason that most dealers hate GSA and why a lot of government accounts get lousy service.

A lot of states have gone to a contract pricing system to reduce the expenses of the bid system. Bids are expensive for all concerned from purchasing to the dealer. I know I used to do all the bidding for a company. Even at the pittance they payed me I was still expensive.

As you are discussing price be frank, bold and treat the money as yours. Act as though you were paying for the microscope out of your own pocket. This will make you a more effective negotiator. Remember that you aren't trying to be the reps. friend, you are trying to establish a business relationship. When you are talking to the sales rep. let them know how important pricing is to you. Ask them for their best price in writing. Do not show this to the competition, this is called "shopping the quote" and is a despised activity. You may just get a call telling you to bug of, its list price! When negotiating remember that the goal for a good negotiation is two fold, for you to get a good price and still have a good business relationship with the dealer. A couple of good negotiating tactics is to let the sales rep know that you are looking at the competition and that they look good, good prices to. If you need a lot of training admit it to the sales rep but if you don't ask for a price that reflects that.

Take your time when negotiating. If you push to hard and fast the dealer may not take the time to give a good price. Wait, be patient, let the dealer look out at all the stock in the warehouse just sitting there. Call back and ask if this is the best price. Let the dealer know that you have gotten quotes from the competition. Don't name figures but let them know that the competitors numbers were very good. Sometimes dealers will have equipment that they have used for demos that they can't sell for new. Ask about the price for this "demo stock". If it's available if could be a good deal for you.

When you are negotiating with a rep. you need to know their mark up. You also need to know what profit they have to have before they will loose money. On a single microscope sale a dealer needs around 18% for the deal to be profitable. This is predicated on a list price of $3,000 to $12,000. Theoretically the higher the

price the less profit margin you need since the after sale costs are similar for low and high priced microscopes.

This isn't totally true. Higher priced microscopes are more complex, weigh more and sell slower. These drive up the after sale costs to the dealer. If you expect the sales rep. to install, train and in general hand hold then that increases costs, someone has to pay the rep to do this.

Discounting microscopes is a fact of life in high volume markets such as the student market and the clinical market. In low volume markets were the technical competence of the rep. is important discounting is less frequent. Typically a clinical microscope will be discounted at least 10% by any dealer while a research microscope will be discounted 2%. To increase available discounts Nikon went to a high list price, high markup strategy.

Olympus markups are 30% on everything except the student CH line of microscopes. Usually Olympus has a 40%-45% markup on the CH line. Nikon has a minimum of a 30% margin but if dealers buy in volume and buy packages of frames, optics and accessories the margins are 40% to 45%. A Nikon dealer can afford to give a better discount. However since Nikon list prices are higher the actual price historically to the dealer has been similar to Olympus's.

Leitz products carry a 30% markup. A lot of Leitz dealers don't like to discount at all since they tend to sell big microscopes that need a lot of service. In the clinical markets Leitz dealers will discount to get your business.

Zeiss doesn't really have a markup policy since they sell direct. However in the last few years they have been very aggressive in pricing. The sales reps seem to have a fair amount of lee way in discounting the product if the need to.

When you have made a decision call both the winner and the loser. It isn't fair to leave everyone hanging. Let the loser know why you made your decision. This will help them improve, everyone needs feed back.

When the microscope is brought into the lab have the sales rep unpack it. This reduces the lost in shipping hassles. If there is something missing then the rep can note it and take care of it. If you unpack it and something is missing you could be blamed for it.

After the microscope is assembled have the rep check of everything on the packing list that will come with the microscope. Check of each item and compare it to the quote or purchase order that was used to buy the microscope. Any discrepancy should be immediately taken care of. If the equipment does not conform to the packing list then make a note of this and have the rep sign the note. This way everyone agrees that there is a problem.

Make a file and put all the documentation from the purchase in it along with the manuals for the microscope. This will help you enormously if you have a warranty dispute or question with the dealer. This is what you have to have if there is any dispute of any kind. Before a manufacturer will do anything under warranty they have to see when the microscope was purchased and who purchased it.

All manufacturers provide a warranty with the microscope. However like all warranties this may actually limit your warranty rights under state law. It is a good idea to talk with or have a seminar put on by your lawyer so persons responsible for capital goods will understand their warranty rights. This can be a real eye opener!

If there is a warranty problem or you have any question the rep. should promptly address it. This does not mean telling you everything will be all right it means getting something done about the problem. If you feel that you are getting the run around call the manufacturer and tell them your problem. Manufacturers tend to take calls like this very seriously.

What this means to you

When buying a microscope know what performance and features you want. Get quotes and demo's then bargain in good faith.

The user in the microscope market

The world of business and management has been turned upside down in recent years. Were businesses were once considered top down structures with the boss telling everyone what to do, we now have customer centered companies were the customer indeed comes first. However microscope manufacturers haven't gotten there yet.

Its not all the manufacturers fault. Customers are not demanding that there views be heard in the design offices. Computer user groups are considered crucial in the design and marketing of new computers. Computer companies listen intently to user groups. However microscope users have never had the same input.

Users must get directly involved by making sure that sales reps and dealers are being their advocates to the manufacturer. Users should insist that manufacturers pay attention to the needs of working lab personnel and not just the more features game. This doesn't mean more lip servic