Optical Design and Husserl’s Phenomenology

David ShaferDavid Shafer Optical Design

USA

Founder of Phenomenology

• PhD in mathematics

• Became professor of philosophy at University of Gottingen, later at Freiburg

• One of the most influential philosophers of the 20th century

Husserl’s insights

• Perception depends on what is out there (reality)+ what we bring to it

• With practice we can see what we have added, like hidden assumptions and interpretations

• If subtracted off, then we are left with reality

The Goal Remove from an optical design problem hidden

assumptions, false choice options, unnecessary constraints, etc.

Result = the true problem

Very hard to do, because we see things that are not really there. It is just human nature.

An example - we easily see faces that are not there

It is very hard to resist this

But seeing face depends on orientation

Even animals make these perceptual overlays on reality

• A bird outline is moved across the sky above baby geese.• When moving in one direction it looks like an

adult goose• When moved in the opposite direction it looks

like a hawk, and represents danger• It is the exact same shape, only the motion is

different

Baby geese and danger

HawkGoose

How to reduce what we bring to a design problem(so as to discover what the real problem is)

• Change coordinate system or orientation of diagrams

• Question hidden assumptions in any diagrams/drawings

• Restate design problem in terms of goals, without stating the means to those goals.

• Try to identify limited choice assumptions

Change coordinate system or orientation of diagrams

Try to quickly say the colors of the letters of these words

Then try again with them turned upsidedown

Being able to read is a handicap here, so turn upside down

Copying (forging) a signature

Herman Darvick

You will tend to write in your own style – hard to avoid

Only copy shapes, not letters

Upside down

To be copied

Confusing – what is this?

Good – have an open mind about what you are seeing

Rotated picture

Here we use familiar sights to interpret and understand the picture, But the picture has not changed. Our perception has changed

Bad – we see much more, like intended use of the water, than is really there.It is just water – the swimming use is what we bring to it.

This view is more reality-based

Optical design goal

• Minimize what I bring to a problem

• Look for hidden assumptions

• Question all assumptions

• Look for alternate choices

• Be smart in solving the problem but “stupid” in understanding it (i.e., don’t assume

anything)

Dec 2007 / Slide 18

Laser FusionQuestioning assumptions in a drawing

19

Highly aspheric lens

Conic mirror

Target pellet

Early Laser Fusion Experiments

Laser input Laser input

Dec 2007 / Slide 20

Target pelletfilled with tritium gas

Dec 2007 / Slide 21

Target ignition at100 million degrees

22

Conventional lens picture from textbook – light stops at focal point : film, detectors, etc.

23

Less common view = light keeps on going

Insight Target pellet is not part of optical system

Hidden assumption – rays are stopped by target pellet, as system drawing shows New Idea• Remove target pellet and only consider the

optics. What happens then?• Then rays hit two mirrors instead of one• Consider a new design with two reflections

Only one ray shown, with target removed

Rays sees two reflections, then leaves system

26

Only one half is traced here

Now is aspheric, not conic

New design, with two reflections before hitting target

27

Slower speed lens, much less asphericity, better ghost images, less lens heating,lower cost

Original design

New, better design

Further insight

New hidden assumption - rays are stopped by target after two reflections

• Consider three reflection design

• Result is even better system – all reflective, no lens heating or ghost images

Simple telescope example

Hole in mirror

image

Insight• Hole in mirror is not part of optics

• Don’t assume a hole

• Consequence – light reflects again at primary mirror

• Explore opportunities to use that

Corrected for spherical aberration, coma, and astigmatism

Final image

First image

Path of a single ray

Image

Corrected for spherical aberration, coma, and astigmatism (with two conic mirrors)

Final image first image

Further insight

• If no hole in secondary mirror then get another reflection there.

• don’t assume holes in mirrors

• Investigate multiple reflection systems with just two mirrors

Two spheres, four reflections

3.33X

Corrected for spherical aberration,coma, astigmatism, and Petzvalcurvature, with just two spheres.

/ Slide 36

Stereo paintings viewer

37

“natural” way to think – right eye sees image on right, left eye sees image on left

“Unnatural” way to thinkEqually useful alternate arrangement – but must switch paintings positions

Dec 2007 / Slide 38

Effect on viewer of reverse stereo

Try to identify assumptions about limited choices

New type of stereo viewer

Arrangement when not in use and folded up

Works both ways, but having crossed lines of sight gives more room for eyes and larger field of view.

Crossed lines of sight

Ray path does not give usual color or distortion of prisms

Door Hole Viewer

Eyepupil

Outside of door

Door viewer optics – strong negative power

Extremely wide angle rays

Inside of door

Eye outside door looking in

Can’t see inside because of extreme vignetting – rays miss the eye

Can only see a very narrow angle through the optics

Optics pupil is inside the system, where eye can’t get at it

Used by police and firemen. Also spies and voyeurs

But there is a sneaky way around this!

Actual system Door hole viewereye

Peephole Reverse Viewer

Door width

Binocular or monocular optics

Unfolded light path

Prisms equivalent

eye

eye

Hidden assumption about binoculars/monoculars

• We are supposed to look through one end but not the other one

• But that is what we, humans, bring to the optical device – it is not part of it

Insight

• You can look through it backwards too and maybe find a new use for it.

Optics used backwards

eye

eye

Relayed image of eye

eye

Move these optics towards right and match up pupils

That effectively then puts eye completely to right of the door viewer, and inside the room

Relayed image of eye

Door width

Next -

Another example of questioning hidden assumptions in a drawing or diagram

Results - a new type of perfect optical system, with no aberrations

Maxwell’s Fish Eye (1854)a gradient index ball

Every point on surface of ball is imaged perfectly to opposite point on ball

Ray paths inside ballare arcs of circles

n = 3.0 at center, 1.5 at outer rim

Hidden assumption in this drawingRays stop at point #2

But in reality they would total internal reflect there and continue on

Point #1 Point #2

Actual ray path

Reflects here at surface of ball

Starts here

Returns here, reflects again, and goes around forever

New Idea Cut ball in half and put reflecting coating on outside surface

It can be proven that then every point on flat diameter surface is imaged perfectly back onto that same surface

•First new perfect optical system in over 50 years

•The only perfect system that forms a flat real image of a flat real object

Known perfect optical systems

• Flat mirror flat and real flat and virtual• Aplanatic surface curved and real curved and virtual

• Maxwell fish eye curved and real curved and real

• Luneberg lens collimated curved and real

• New design flat and real flat and real

Object image

How to reduce what we bring to a design problem

• Change coordinate system or orientation of diagrams

• Question hidden assumptions in any diagrams/drawings

• Restate design problem in terms of goals, without stating the means to those goals.

• Try to identify limited choice assumptions