wp axis thermal cameras en 37661 0912 lo

7/27/2019 Wp Axis Thermal Cameras en 37661 0912 Lo

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Som lk oThermal cameras in surveillance



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All network cameras have a basic physical limitation: they need light to work.

At least up to now.

Sure, some network cameras have night and day unctionality that allows them to operate in very poor

lighting conditions, down to ractions o a lux. And o course, i natural light is not available it can besubstituted by electrical light, either visible to the human eye or inrared. But in some instances thesesolutions have serious drawbacks – they can be expensive, and energy consuming; and illumination cre-ates shadows where an intruder can hide – to mention a ew.

The rst true thermal network camera is a perect complement to any proessional IP-Surveillance sys-tem; it can be seamlessly combined with existing equipment, and it is possible to secure an area or aperimeter that lies in complete darkness.

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Thermal imaging is nothing new. But until recently, costs have usually been prohibitive, making practical

applications outside the military rare. This has started to change as new sensors, new materials and otherimprovements are driving the volumes and making prices more reasonable. Thermal cameras can now beound in various lines o business such as the aircrat industry, shipping industry, and security and surveil-lance. The technology is also used in public services like re ghting and law enorcement. Lately it haseven appeared in consumer products, albeit oten expensive ones like luxury cars.

Complete darkness, haze, smoke, rain, snow, even bright and blinding lights – a thermal network camera will still be able to detect people and objects.

Like any other camera, a thermal or thermographic camera collects electromagnetic radiation which isormed into an image. But while a conventional camera works in the range o visible light, i.e. with wave-lengths between approximately 400 and 700 nanometers (0.4–0.7 μm), a thermal camera is designed todetect radiation with greater wavelengths, up to around 14,000 nanometers (14 μm). Radiation in this parto the electromagnetic spectrum is reerred to as inrared, or commonly IR, which in turn can be dividedinto several sub-groups.

Near-inrared light has a wavelength o about 0.7–1.5 µm, which is just beyond what the human eye can see.Camera sensors, on the other hand, can be built to detect and make use o this type o radiation. A so-calledday-and-night camera uses an IR-cut lter during daytime to lter out IR-light so it will not distort the colorso images as perceived by the human eye. When the camera is in night mode, the IR-cut lter is removed.Since the human eye is unable to see inrared light the camera displays the image in black and white. Near-inrared light also requires some kind o light source – either natural, such as moonlight, or man-made, suchas street lights or a dedicated IR-lamp.

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Moving urther away rom visible light, the rest o the IR-spectrum is usually divided into the ollowingcategories:

Short-Wave Infrared (SWIR), approx. 1 – 3 µm>

Mid-Wave Infrared (MWIR), approx. 3 – 5 µm>

Long-Wave Infrared (LWIR), approx. 8 – 12 µm>

Very Long-Wave Infrared (VLWIR), approx. 12 – 25 µm>

Far-Wave Infrared (FWIR), approx. 25 µm – 1 000 µm or 1 mm>

Note that there is a gap between 5 µm (MWIR) and 8 µm (LWIR). This part o the waveband is virtuallyunusable or thermal imaging purposes because o the high spectral absorption o the atmosphere in thisrange. Microwaves have a wavelength exceeding 1 mm. At the ar end o the spectrum are radio waves, with awavelength o 1 meter and more. In the other end o the spectrum, wavelengths shorter than those o visible light are successively reerred to as ultraviolet, x-rays, and gamma rays.

Conventional cameras work in the range o visible light, i.e. with wavelengths between approximately 0.4–0.7 μm.Thermal cameras, on the other hand, are designed to detect radiation in the much broader inrared spectrum, up to

around 14 μm (the distances in the spectrum above are not according to scale).

W mks wok?Images, as they are perceived by the human eye, can be described as light reected by dierent objects.No light means no reection and thus the eye is “blind” under such circumstances. Thermal images on theother hand, are not dependent on visible light. Instead, images are created by operating in the inraredspectrum. It works perectly well even in total darkness since the ambient light level does not matter.

What makes this possible is the act that all objects – organic or inorganic – emit a certain amount o inrared radiation as a unction o their temperature. This is true or all objects that have a temperaturethat is above absolute zero, i.e. 0 degrees Kelvin (-273° C or -459° F). That means that even very coldobjects, such as ice or an outdoor steel post in winter, emit thermal radiation.

The ability to emit absorbed energy is termed emissivity. All materials have more or less emissivity (e). Theirrespective value ranges, depending on their dierent properties, rom 0 to 1. The latter value only appliesor a theoretical object called a Black-body. In general it could be said that the duller and blacker a mate-rial is, the closer its emissivity is to 1. Conversely, a more reective material has a lower e value. For ex-ample highly polished silver and brass have an emissivity o about 0.02 and 0.03 respectively. Iron has anemissivity o 0.14 – 0.035 i polished, but 0.61 i it has rusted red. Regular glass, which eectively blocksthermal radiation, has an emissivity o 0.92.

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All objects emit thermal radiation which can be detected with a thermal network camera. Images are generally pro-

duced in black and white but can be articially colored to make it easier to distinguish dierent shades.

An object’s thermal radiation is also dependent on its temperature – the hotter it is the more thermal radia-tion it emits. Humans cannot see this, but we can sense it, or example, when we approach a camp re orenter a sauna. The greater the temperature dierence in a scene, the clearer will the thermal images will be.

Furthermore, some materials will have a dierent emissivity in the mid-wave inrared spectrum than in thelong-wave span. For imaging purposes these dierences in emissivity are, or the most part, o secondaryimportance since the camera’s sensitivity can be dened as its capability to distinguish between tempera-ture dierentials.

Thermal images are sometimes associated with bright, intense colors – which may seem a bit odd consider-ing that the camera works outside the spectrum o visible light. The answer is that the colors are createddigitally, so-called pseudo-colors. Each color or nuance represents a dierent temperature, usually whiteand red or higher temperatures, over green, blue and violet or colder ones. The reason is oremost practi-cal since the human eye is better at distinguishing dierent shades o color than dierent shades o grey.

Detectors used or thermal imaging can be broadly divided into two types: Cooled thermal imagers that

typically operate in the mid-wave inrared (MWIR) band and uncooled thermal imagers that operate in thelong-wave inrared (LWIR) range.

as cold s gs – coold dcosCooled inrared detectors are usually contained in a vacuum-sealed case and cooled to temperaturesas low as 60 to 100° K (circa -210° to -170° C or -346° to -274° F), depending on the type and levelo perormance desired. These extremely low temperatures are accomplished with so-called cryo-genic coolers. Cooling is needed to reduce thermally induced noise – at higher temperatures the sen-sors risk being ooded or “blinded” by their own thermal radiation. The equipment not only makes thedetectors relatively bulky and expensive, but also rather energy-consuming.

Although this technology is both expensive and demanding in maintenance, it has benets. These

detectors work in the mid-wave spectral band, which provides better spatial resolution because thewavelengths are much shorter and provide higher thermal contrast than in the long-wave band.Hence, cooled detectors can distinguish smaller temperature dierences and produce crisp, high reso-lution images.

Another advantage is that greater sensitivity also allows the use o higher F-number lenses. Conse-quently, cooled detectors are a better choice or long range detection, i.e. 5 km – 16 km (3 – 10 mi).

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The sensor in an uncooled thermal camera is not dependent on cryogenic cooling. In this case the sensoris stabilized at or close to the ambient temperature, using less complicated temperature control ele-ments. Sensors o this kind operate in the long-wave inrared band.

A widespread design is based on microbolometer technology. This is typically a tiny resistor with high

temperature-dependent properties on a silicon element, which is thermally insulated and read elec-tronically. Changes in scene temperature will cause changes in the bolometer which are then convertedinto electrical signals and processed into an image. The camera’s sensitivity to inrared radiation, i.e. itscapability to distinguish dierent temperature dierences in a scene, can be expressed as its NETD-value (Noise Equivalent Temperature Dierence). Later generations o bolometers have reached NETD aslow as 20 mK.

Uncooled thermal image sensors are smaller and built with ewer moving parts . Not only does this makethem less expensive than their cooled counterparts but also allows or much longer service intervals.Whereas the cooled cameras typically need a rebuild or the cryocooler every 8,000 to 10,000 hours, anuncooled camera can run continuously or years.

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Thermal cameras do not only perorm well in total darkness, they also perorm well under difcult cli-matic circumstances such as haze, dust, rain, snow and smoke. All the same, there are physical limita-tions to the perormance o thermal cameras.

Deep shadows or other difcult lightings situations – thermal network cameras are an excellent complement to regu-

lar surveillance cameras.

Water droplets or small dust particles in the air will naturally hinder the transmittance o thermal radiationrom a single object, making it harder to detect rom a great distance. Consequently, haze, snow and rainwill hamper camera perormance. Water limits thermal radiation and the moisture in the air evens outtemperature dierences between dierent objects in the picture. Thereore, a thermal camera will producebetter and clearer images during winter time with clear skies and good weather conditions than under

comparable atmospheric conditions during summer when humidity is usually higher.

But even with these limitations considered, when it comes to detection, thermal cameras are superior toconventional cameras under a wide range o difcult weather conditions.

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The integration o thermal cameras into the conventional video surveillance market is not ree rom chal-lenges – technical as well as legal and other.

A number o products and technologies that can be used both or military purposes and in commercialapplications are called dual-use goods. Exports o such items are regulated in the international Wasse-

naar Arrangement rom 1996, which aims to promote transparency and greater responsibility in trans-ers o conventional arms as well as dual-use goods and technologies.

Not surprisingly, thermal imaging technologies, which oten have been originally developed or militaryuse, all under this category. Thermal sensors may thereore only be reely exported i the maximumrame rate is 9 ps or below. Most cameras or surveillance purposes all under this category. Cameraswith a maximum o 111,000 pixels and a rame rate o up to 60 ps can be sold in the US, the EU, and ahandul o other riendly nations, on the condition that the buyer is registered and can be traced.

Regardless o these restrictions, resolutions are generally much lower or thermal cameras than or con-ventional network cameras. This is primarily due to the more expensive sensor technology involved inthermal imaging. However, lower rame rate is less o a problem in most surveillance applications since

thermal cameras are rst and oremost used or detection and not or identication.

No lurking in the shadows! Thermal network cameras can also be used indoors to improve building security and emer-gency management. They can veriy that people are not hiding in a building ater closing time, and prevent vandalismand institutional riots.

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More troublesome, at least rom an economic point o view, is that there are no standard optics orthermal cameras. Any adaptation o ocal length or a special required eld o view must be done at theactory. The reason why regular optics and lenses, such as a standard CS-mount or C-mount, cannot beused is that ordinary glass efciently blocks thermal radiation. Manuacturers thereore have to rely onother materials. Presently, Germanium is most used or thermal camera optics. This very expensive met-alloid, chemically similar to tin and silicon, blocks visible light while letting thermal radiation through.

Naturally, the same requirements apply or housings, making it impossible to use standard housings oroutdoor installations. Like lenses, housings must thus be specially adapted or thermal cameras.

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Although the investment costs are high, thermal cameras are not unknown within security and surveil-lance; on the contrary. They are primarily used in high security buildings and areas, such as , or example,nuclear power plants, prisons, airports, pipelines, and sensitive railway sections.

So ar, however, incorporating thermal cameras into a conventional video surveillance system has not

been a straightorward operation. With the development o thermal network cameras, compatibility willo course, be ar less o an issue. New devices will more easily integrate with, or example, existingvideo management systems.

Among other benets that IP-Surveillance brings are Power over Internet (PoE), distributed intelligentvideo, standardized video compression techniques and audio support.

PoE is a technology or sae and simultaneous transer o electrical power and data in Ethernet networks,thus eliminating the need or power cables and reducing installation costs. Intelligent video is a compre-hensive term or any solution where the video surveillance system automatically perorms an analysis o the captured video, such as motion detection, audio detection, and virtual ences, or sets o an alarmwhen cameras are vandalized or tampered with. With thermal network cameras, this analysis can be

distributed out to the cameras leading to improved efciency and scalability.

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With thermal imaging becoming relatively cheaper and an integral part o IP-Surveillance systems, awhole range o uses becomes both possible and economically viable. Thermal cameras can be an excel-lent complement in many situations where conventional cameras are inadequate or insufcient.

They are, o course, unparalleled in a situation o total darkness. They can also be an option in areas thatare very difcult to illuminate eectively, or example a sea ront, a harbor, or any other vast expanse o open water. Similarly, articial light not only runs the risk o revealing where the cameras are placed,enabling parties to avoid or vandalize them, but can also create projected shadows in which an intruder

can avoid detection.

Furthermore, spotlights can blind as well as illuminate. So cameras that do not rely on light can be thepreerred solution in many dierent trafc situations, whether it is in railway tunnels, on air strips or onregular streets. Thermal cameras, on the other hand, cannot be blinded by bright lights or laser beams.

All in all, thermal network cameras perectly complement and complete a network video system, makingsure that objects, people, and incidents are detected 24 hours a day, seven days a week.

The rst true thermal network cameras, AXIS Q1910, or indoor applications, and the AXIS Q1910-E, with tailor-made

protective housing or outdoor installations.

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www.xs.com

abou axs CommunconsAxis is an IT company oering network video solutions or

proessional installations. The company is the global

market leader in network video, driving the ongoing shit

rom analog to digital video surveillance. Axis products

and solutions ocus on security surveillance and remote

monitoring, and are based on innovative, open technology

platorms.

Axis is a Swedish-based company, operating worldwidewith ofces in more than 20 countries and cooperating

with partners in more than 70 countries. Founded in 1984,

Axis is listed on the NASDAQ OMX Stockholm under the

ticker AXIS. For more inormation about Axis, please visit

our website at www.axis.com.

©2009 Axis Communications AB. AXIS COMMUNICATIONS, AXIS, ETRAX, A RTPEC and VAPIX are registered trademarks or trademark applications o Axis ABin various jurisdictions. All other company names and products are trademarks or registered trademarks o their respective companies. We reserve the rightto introduce modications without notice.

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