husserl talk
DESCRIPTION
Shows a connection between Husserl's phenomenology and problem solving in optical designTRANSCRIPT
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