A revised version of an earlier slidehare.net post

1. My 51 years of optical design – some highlights
Dave Shafer
David Shafer Optical Design
Fairfield, Connecticut 06824
shaferlens@sbcglobal.net
203-259-1431

2. My early years

3. As a young boy I was always
fascinated by magnifying glasses
Optics is kind of like magic
It was not what you do or see with it that interested
me. It was the lens itself and how it did this magic.

4. Some kinds of flashlight
bulbs have a very small glass
lens on their tips.
I used to carefully break the end off
with a hammer and use the tiny lens as
a high power magnifying glass – about
50X magnification

5. I also made water
drop microscopes. A
small drop of water
can very easily give
100X magnification,
but it has to be held
up extremely close to
your eye for you to
see through it.
The first single lens
microscope, from 300 years
ago, had a tiny glass lens
and was about 250X, but a
water drop works well too.

6. 1957 Sears Roebuck catalog
when I was 14 I had two 100X, 200X, 300X
microscopes from Sears. One I used
and one I got on sale for $4.50 and
took apart to get at the lenses

7. I lived on a small
farm, until I went
to college. We had
5,000 chickens.

8. We also had one cow, and I did not drink
pasteurized milk until I went to college.

9. Our farm was
very far from
city lights and
the night skies
were very dark –
perfect for
astronomy.
Many people
have never seen
a really dark sky,

10. When I was 13 years
old I got a mail-order
kit for grinding and
polishing a 150 mm
aperture telescope
mirror, and something
like this was the
result.

11. A historical note
here. Very soon
after the telescope
was invented
something else was
invented that did
not exist before.
Window shades.

12. I bought a small
star spectroscope
(100 mm long) and
drew charts of the
solar spectrum, with
its many absorption
lines. Now, over 50
years later, that exact
same spectroscope
costs about 10X more
money.

13. I devoured these three books
when I was 14 as well as the
very wonderful story of the
Mt. Palomar telescope.

14. I discovered
for the first
time, back
then, that men
and women
see the world
differently.
This is still a
mystery to me.

15. I found that men are relatively simple, with an off/on
switch, but that women are more complicated. Who knew??

16. I was hooked on optics! When I was 15 years old
I got Conrady’s two books on lens design.

17. I also got a book that was
full of complicated diagrams
like this one. It made optics
look pretty difficult.

18. Some of this material was hard to
understand but I stuck with it

19. I have always been able to focus my
attention very well

20. I figured that with
time I would be
able to understand
and communicate
with math at the
required level.

21. When I was in high school there were no personal computers yet
and no large main frame computers that were available to the
general public. I traced a few light rays through an achromatic
doublet lens, with trigonometric ray tracing using tables of 6
decimal place logarithms. After you do that once you never want
to do it again! But I still knew that I wanted to be a lens designer.

22. Back then in the late 1950’s there was almost nothing written about
lens design so there was nowhere to get help with my study of it.

23. When I went to college in
1961 big universities had a
main frame computer.
Data was input using
punched cards. At the
University of Rochester,
where I went, the Optics
department was able to use
this computer and students
like me were able to do
some simple lens design
problems.

24. Back in 1961, when I was a
freshman, you had to wear a
U of R beanie for your first
year. I have just gotten mine
here. In 1965 I graduated in
philosophy and then went to
U of R grad school in optics.

25. While at the University of Rochester I had an electrifying
experience – I met my wife

26. Her grandmother (in math),
her mother (in history),
herself (in English), and our
daughter (in philosophy)
have all gone to the U of R.
That had better be me

27. She was able to see beyond my
very unsophisticated exterior to
my very unsophisticated interior.
But I was able to convince her to
accept me and we have been
married for 52 years now.

28. During a summer job in 1964
at Itek Corp, I was the first to
observe in the lab a spiral
interference fringe. Bob
Shannon came up with the
correct theoretical explanation
and an article about it was
published in Applied Optics in
1965, while I was an
undergraduate at U of R. That
summer I did a lot of HeNe
laser interferometer
experiments in the lab
The red laser would look red to me in the morning,
when I started work, and would look orange and dimmer
as the day went on as I stared into the laser optics more
and more. Now I can look directly at the sun with no
effect. Oh wait …. that was the moon.

29. In the 1950’s electro-mechanical calculators (electricity
powered the calculating gears) were used to do optical
raytracing. To trace one light ray through one optical surface
took about 3 minutes. In the early 1960’s true digital
computers (main frames) were developed and they could
trace one ray-surface per second. Today an ordinary PC can
trace about 30 million ray-surfaces per second.

30. Optimization of optical
systems requires matrix
inversion. Hand calculations or
electromechanical calculators
in the 1950’s did 2 X 2 matrix
inversions – two variables and
two aberrations. Very many
of them, in sequence. Today,
with my PC, I optimize complex
lithographic lenses with many
high-order aspherics. I can
optimize several thousand rays
using about 100 variables and
there is an enormous matrix
inversion – in just a few
seconds.

31. The early lens design
programs were not at all
user-friendly and you had to
carefully study the program
manual in order to effectively
work with the program. If
you changed jobs you might
have to learn a whole new
program at the new place. I
did that several times and
have used ORDEALS, ACCOS,
SYNOPSIS, the Perkin-Elmer
in-house program, and OSLO.

32. Although computers
have revolutionized
optical design, there is
still a big need for
creative thinking by the
designer, using your
own mental PC

33. I have found that the
best way to be creative
when faced with an optical
design problem, or
basically any problem at
all, is to question hidden
assumptions. We all make
unwarranted assumptions,
all the time.

34. When I was a kid I bought an AM radio
I made an unwarranted assumption

35. AM radio PM radio
I thought I was going to have to buy two radios.
(this is a joke)

36. My first job after college, in
1966, was at Itek, a small
high-tech company that did
military optics – mostly very
high resolution reconnaissance
cameras for the U-2 spy plane
and for early space satellite
cameras.
I worked on a top-secret
project there that was a new
way to detect Russian
submarines. Some years ago
this secret technology was
declassified and today you can
read all about it on the
internet. More about this in a
moment.
Submarine with its periscope
above the water surface

37. The first part of my career
was dominated by Cold War
tensions. We were in the early
days of our space programs
and there was a big arms race.
Sometimes rockets didn’t work
right. We thought that there
was a missile gap with Russia.

38. The very high altitude U-2 spy plane found during
flyovers of Russia that they did not have nearly as
many missiles as we had thought, in the early
1960s. This chart shows the actual reality back
then, based on reconnaissance photos.

39. The CORONA
satellite program
took pictures
over Russia and
then ejected film
canisters that
were caught in
midair. Some
were missed and
fell into the
ocean but most
were caught.This was a top secret program,
based at Itek, near Boston, where
I was working.

40. The timing of the film canister catch had to be very
precise. The film gave further proof that the “Missile
Gap” with Russia was false and that information was
used as a bargaining point in the Salt Talks with
Russia for arms reduction.

41. The CORONA satellite took stereo
photo pairs that had certain projective
distortions. Those photos were then
reimaged by the Gamma Rectifier lens,
which cancelled out those distortions. I
worked on that design at Itek Corp. in
the late 1960s. These lenses were built
and then worked 24 hours a day for 10
years straight fixing spy photo
distortions.

42. Back to the
submarine
project.
Submarine with its periscope above the water surface

43. In World War I and World War II submarines would be
found by looking for their periscopes sticking up above the
water. Sometimes the sun would reflect off the front surface
of the periscope optics, but there was also sun glint off of the
water waves and it was very hard to tell them apart.

44. From an airplane the water
wake left by the moving
periscope could be seen.
But if the submarine
was moving slowly or
not at all then the
wake was very hard to
see, like in this case
here.

45. What was needed was a
new and highly sensitive
way to spot submarine
periscopes, when they were
above the surface of the
water.
The solution was to use
optics and lasers in a new,
top-secret way.
This new technology was given, back in
1966, the code name “Optical Augmentation”
and it is still called that today. You can look it
up on the internet.

46. We all know
about red eye
from camera
flash photos.

47. The eye retina reflects back the
focused light and then it is collimated
by the eye lens. It can then travel long
distances backwards without spreading
very much. That is why flash camera
“red eyes” are so bright, like this cat.
Eye retina

48. Near IR
laser beam
Eye retina
Periscope
optics
A low power near-IR laser beam
was sent out over the water surface,
from a ship, and scanned around by
360 degrees. If there is a periscope
above the water then the laser light
goes down the periscope optics tube
and is focused on the eye retina of the
person who is looking through the
periscope. That light then reflects off
the retina, is collimated by the eye’s
lens, and reverses its path back up the
tube and out. It travels back over the
water to the ship where the laser is
located and a very bright “red eye”
can be seen.
Water level

49. The energy collection area of the periscope optics
is very much larger than that of the eye by itself, so
the retro-reflected signal is orders of magnitude
larger and gives a huge “red eye” effect.

50. You may find this hard to believe but
with this relatively simple technology a
submarine periscope can be detected
that is many kilometers away. The laser
used is near IR instead of a visible
wavelength so that the person looking
through the periscope will not know
that they have been detected.
This same technology can be used in other ways. Airplanes can
detect the eyes of soldiers looking through the sights of
camouflaged anti-aircraft guns. Film or a detector array at the
focus of a camera also reflects back light and that is then
collimated by the camera lens on the way back out. Hidden
cameras can be found this way. From the ground level a laser can
detect space satellite camera optics. A pulsed laser can actually
measure the distance to a hidden camera, telescope, or periscope.

51. Today you can buy several versions of
this declassified technology on the
internet for less than $100 and find
hidden cameras in your hotel room or
other places, especially those tiny pin-
hole sized cameras - like on cellphones.

52. The countermeasure that can defeat this system is
pathetically cheap, simple, and very low-tech. Back when I
was working on this project the countermeasure ideas
were at a classification level above top secret.
In general most expensive high tech new weapon related
systems, like that below, can be defeated at a cost well
below 1% of the cost of the system that is being defeated.
To date all the
bogus tests of this
system have been
completely rigged
and even then
most fail. Do not
believe the hype
about this system.

53. The Navy now has an extremely expensive high power laser system
that is designed to shoot down and burn up cruise missiles in flight.
Here is a simple ultra-cheap countermeasure that defeats this laser
system – have a reflective mirror coating on the whole outside of the
missile. Then the incoming laser power will not be nearly enough to
destroy the missile. Most will be reflected away. An ultra-cheap
optics idea.

54. Early warning missile defense system
(Work I did in 1972, 45 years ago).
In 1971 I changed jobs and worked for a company
that specialized in infra-red military optics. One
project was this ----

55. If a missile from behind
the earth comes over the
rim of the earth it will be
seen here by a satellite
against a black sky, but it
will be very close to an
extremely bright earth,
which gives an unwanted
signal that vastly exceeds
the missile’s infra-red heat
signal. But that is the easy
case. Much worse is when
the satellite is on the night
side and the missile is seen
against a sun-lit earth’s
limb.

56. With the sun behind the horizon, the earth’s limb is
ten orders of magnitude brighter than the missile’s
infra-red heat signal.

57. Astronomers use a special kind of telescope, a
coronoscope, to look at the sun’s corona. They need
to block out the light from the body of the sun and
just look at the sun’s edge. This is possible using a
“Lyot stop” and this very old technology was used in
missile defense satellite optics.
It can block out very bright light that is just
outside the field of view of the telescope and which
is being diffracted into that field of view. That
unwanted diffracted light can be many orders of
magnitude brighter than the dim signal that the
telescope wants to see, in its field of view.

58. Rim of aperture stop is source of diffracted light
Light
from
earth
limb
Second aperture stop is smaller than image of first stop,
and it blocks out-of-field diffracted light from earth limb.
Lyot stop
principle
Two confocal
parabolic mirrors
give well-corrected
afocal imagery
Field of view rays
Diffracted light is focused unto second aperture stop

59. The use of the Lyot stop
principle, plus super-polished
optics, makes it possible to
reject almost all of the
extremely bright unwanted
signal from the sun and the
earth’s limb and to just see
the missile signal.
I worked on some space optics systems to make
accurate measurements of the earth limb signal profile,
as well as some wide angle reflective space-based
telescopes for reconnaissance.

60. I also designed optics for medical infra-red imaging
systems. The infra-red heat temperature map of a person’s
face or other parts of the body can often show different kinds
of illness, including cancer. There is no physical contact with
the patient, just infra-red optical imaging.
Display shows temperature
as different colors.

61. In 1975 I changed
companies again and
went to work for Perkin-
Elmer Corp., a maker of
laboratory instruments.
They were just starting
to get into making some
lithographic equipment.
Their “Micralign” optical system made it possible to make 1.0u
circuit feature sizes on 75 mm diameter silicon wafers, using mercury
i-line light from a lamp. This was a 1.0 X magnification system. I
designed a next generation 5X system that was able to make .50u
feature sizes. The 5X magnification made the mask easier to make.

62. An ant holding 1.0 mm square chip, with tiny
circuit features. What plans does the ant have for this chip?
It is hard
for us to
imagine
how small
one micron
really is.

63. A guitar made the same size as a red blood
cell, using nanotechnology

64. nanotechnology

65. 30 years ago computer chips had circuit features one micron in size
One
micron

66. Today’s chips have about .03u circuit features

67. In 1976 I also worked on early experiments in
Laser Fusion

68. Laser fusion, if it ever works, will be about as cost
effective a way to produce energy as it is to go to the moon
in order to get some sand for your children’s sandbox. It’s
main use, if it works, will probably be to test the physics of
new nuclear bomb designs. My work was in the very early
days of laser fusion, around 1976.

69. Conic mirrorConic mirror
Highly aspheric lens
Target pellet
Very high power laser beams enter from opposite sides
and are focused onto the tiny target pellet.
Laser beam Laser beam

70. Target pellet
filled with
tritium gas

71. Laser fusion ignition
at 100 million degrees

72. Conic mirrorConic mirror
Highly aspheric lens
Target pellet
The highly aspheric lens was made of the highest possible
purity glass but it would still absorb enough of the very high
power laser energy so that it would often explode!
Laser beam Laser beam

73. I thought of a new type of design where there are two reflections from the
mirrors instead of one, before focusing on the target pellet. The result is that
the focusing lens is much thinner, with very much less asphericity and it does
not explode. It is also much less expensive to make.
An identical ray
path is not shown
here for this side
of system

74. One of my first
patents, in
1977, was for
an unusual kind
of telescope
that only has
spherical
mirrors.
Many years later one of these unusual telescopes was
sent on the Cassini space craft to Saturn. Later another
one went to the asteroid Vesta, and took photos.

75. This is the Cassini space
craft before being launched.
Another of my telescopes
was on a space mission to
visit a comet and fly up
close to it.
Close up of
asteroid Vesta,
taken recently
from space with
my telescope.

76. When my telescope on the
flight to the planetoid Ceres first
started showing the mysterious
bright “lights” it looked for a
while like we had found lights
from an alien city.

77. Another telescope of my design was on the Rosetta
mission to land on a comet

78. My middle years
My early years

79. In 1980 I started my own
one-person optical design
business. This was very
unusual, back in 1980 and
is still not very common
today in the USA. In most
other countries it is very
rare. It was possible for
me because I had lots of
business right away in
lithography optics design,
with some companies like
Tropel, Ultra-Tech, and
Perkin-Elmer.
My early design work
back then was done on
an Apple computer,
using the OSLO design
program.

80. Since 1980 I have
worked at home.
That experience is
not for everybody,
but I like it.

81. 81
Salvador Dali
Spanish Surrealist artist
One very interesting
short project I had, in
1980, was for the artist
Salvador Dali.

82. Dali was once called “a
genius, up to his elbow”
because of his amazing
technical skills, but crazy
ideas – like his 1936
lobster telephone.
Dali working at his desk

83. 83
Salvador Dali
Late in life Dali mastered the art of making stereo pair
paintings, sometimes of scenes that only existed in his
amazing imagination. He wanted a novel new kind of
stereo viewer to view the stereo painting pairs.

84. When I met him in 1980 Dali was an older man and not
in the best shape, but his mind was tack sharp. I spent
about an hour alone with him discussing stereo ideas

85. 85
Salvador Dali stereo painting pair, with about
8 distinct 3-D depth planes

86. 86
I had always
been fascinated
by stereo effects,
like this 1957
Sears catalog
ViewMaster.
It was a lot of
fun to work on
this 3-D project
for Salvador Dali.

87. Salvador Dali had managed to
paint a stereo pair of paintings,
which is an amazingly difficult
thing to do. He wanted a new
type of stereo viewer to go with
his unusual painting pair. The
paintings would be on a wall
and then a person would look at
them with a stereo viewer that
could be adjusted for the
viewer’s distance from the
paintings.

88. 88
You just have to remember to
switch the positions of the stereo
paintings if you go for the alternate
viewing configuration. If you don’t
you get reverse stereo, which is
hard on the brain.

89. Deviating prism
wedges can make a
stereo viewer but they
have a lot of
dispersive color and
mapping distortion
and are not adjustable. I realized that a different ray path
through a prism can have no color, no
distortion, and be adjustable.

90. The final viewer was just
two 45-90-45 degree
prisms with a flexible
hinge that joined them
along one prism edge.
They could be folded up,
when not being used, into
a larger size triangle.
I did not have to go
anywhere near a computer
to do this design project!

91. A 20” aperture Shafer-Maksutov telescope in Swansea,Wales

92. In the 1980’s both Field and
Shafer independently published
descriptions of a new kind of
telescope. It is ideally suited for
amateur telescope makers
because it is very simple and
inexpensive to make. There are
two spherical mirrors and a single
thick meniscus lens. My version
has been called by others the
Shafer-Maksutov. It uses the lens
thickness as a more important
design parameter than Ralph
Field’s design version.
For a large aperture telescope the lens
thickness gets too large and expensive. Then a
better solution is to split it into two thin lenses.

93. A retired doctor, a member
of the Swansea (Wales, UK)
Astronomical Society, read
about my design and offered
to fund the building of a 20”
(500 mm) aperture telescope.
The less than ideal observatory site is right on the beach. The telescope is
used mostly for public education. It has recently been relocated to a better
site inland.

94. Around 1990 I did the design, with a f/2.5 spherical primary mirror and about an f/18
system. The two lenses are both flat on one side and have the same convex/concave
radius on the other side. BK7 glass was used, the cheapest optical glass.
The design is diffraction – limited over the
visual spectrum over a small field size.

95. It is the largest telescope in Wales

96. This is quite a jump up in size from the ½ meter
aperture telescope in Swansea, Wales

97. Budgets will determine where this quest for
ever larger telescopes will end.

98. Recently I have discovered an amazing design, of just two conic surfaces with three reflections
between them. With a 100 meter diameter f/.75 primary mirror and a f/4.6 system it is
diffraction-limited at .5000u over a .10 degree diameter curved field, giving a 800 mm diameter
image. Both mirrors are very close to being parabolas. The obscuration due to the hole in the
secondary mirror is about 8% area. The big weakness is it can’t be baffled well.
f/.75
primary
mirror

99. The Kilometer-Scope!!
One
kilometer
f/1.0 primary mirror
diffraction-limited f/6
system over a 4 meter
diameter image

100. Just as the telescope is huge, the spectrograph is too. I did a
design for it. It is unusual because the spectrograph requires
an external aperture stop.

101. Because it is all-reflective it can handle the deep UV through the IR

102. Door Hole Viewer

103. Eye
pupil
Outside
of door
Door viewer optics – strong negative power
gives wide field of view
Extremely wide angle rays
Inside
of door

104. 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
Wide angle exit pupil of door viewer is inside it, where
outside eye cannot get close enough to it to be effective

105. Used by police and firemen. Also spies and voyeurs
But there is a sneaky way around this!

106. Actual system
Door hole viewer
eye
Peephole Reverse Viewer
Door width

107. 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. You have more choices here
than just the usual way of looking through it.

108. Binocular or monocular optics
Unfolded light path
Prisms equivalent
eye
eye

109. Optics used backwards
eye
eye
Relayed
image of eye

110. eye
Move these optics towards right and match up
its exit pupil to the pupil of door viewer.
That effectively then puts eye completely to
right of the door viewer, and inside the room
Relayed image of eye
Relayed image of eye pupil can be put inside
door viewer or even outside it, inside the room
eye

111. After I started my company in 1980 my optical design work has
included camera lenses, medical optics, telescopes, microscopes,
and many other systems. Since 1996 almost all of my work has
been lithographic designs for Zeiss, in Germany, and wafer
inspection designs for KLA-Tencor, in California.
A typical lithographic 4X stepper lens design, from 2004. It is .80 NA,
1000mm long, has 27 lenses and 3 aspherics. The 27 mm field diameter
on the fast speed end has distortion of about 1.0 nanometer, telecentricity
of about 2 milliradians, and better than .005 waves r.m.s. over the field at
.248u. More modern designs have more aspherics and fewer lenses.

112. These
lithographic
stepper
lenses are
made by
Zeiss and
then put into
ASML chip-
making
machines.

113. These state of the art
stepper lenses cost about
$20 million each and
many hundreds have
been made by Zeiss and
sent to ASML. In 2006
I invented a new type of
design that combines
mirrors and lenses and it
is now the leading-edge
Zeiss product, making
today’s state of the art
computer chips.

114. I have several patents on this new kind of lithographic system, that
combines lenses and mirrors. Many of the lenses are aspheric, to reduce the
amount of surfaces and glass volume. Some of these designs have 4 mirrors
and some have 2 mirrors. One important characteristic of these designs is
that there are two images inside the design, while conventional stepper lenses
have no images inside the design. These are immersion designs, with a thin
layer of water between the last lens surface and the silicon wafer that is being
exposed. The design being made today by Zeiss is 1.35 NA and works with
.193u laser light. They will not say, and I won’t either, if it looks like this
design here or one of my other patents.
Aspheric mirror
Aspheric mirror
wafer
mask

115. With my latest version of this lens/mirror design and double-patterning
exposures it would be possible to write a 300 X 300 spot image onto an
area the size of single red blood cell – more than enough to etch a good
photo of yourself, or to write an office memo, onto that surface.
Red blood
cells, 8u
across

116. For some years I have been working for Zeiss on EUV
(X-ray) lithography, which will be the next generation of
lithography systems. This only uses mirrors.

117. The aspheric mirrors made for these high-performance
optical systems are aligned to a precision of a few
millionths of a millimeter (i.e. nanometers). Their surface
figure quality (admissible deviation from the exact
mathematically required surface) and the surface roughness
are approximately three or four times the diameter of a
hydrogen atom. (!!!!!!!)

118. 118
All-silica broadband design
For KLA-Tencor I have developed new designs for wafer inspection
that cover an enormous spectral region with only a single glass type.
wafer
.266u through .800u

119. Prototype, made by Olympus, .90 NA, wavelength = .266u - .800u

120. My future
My plan is to work forever, but with fewer hours. I love optical
design! After death I plan to cut back to maybe 20 hours a week.

121. My time is finished
- any questions?