baker@csl.dl.nec.com (Larry Baker) (05/10/91)
[]
Here's the summary of responses to my posting re: Computer Generated Holography.
I only got one response today, so I figure any more are going to be few and
far between, so here it is. I've mailed a copy to everyone who contributed.
I've also including net postings, namely William De Rieken's, simply to have
a complete summary. I'll keep updating it as more come in; if you have
something to add, please send and/or post it, and I'll add it to the file.
When I decide it's grown sufficiently, I'll mail and post a revised copy.
/////////////////////////////// Summary ////////////////////////////////////
baker@csl.dl.nec.com (Larry Baker)
A friend pointed me to Foley, van Dam, Feiner & Hughes, "Computer
Graphics Principles and Practice," 2nd Ed., pp. 918-919, which contains
a brief section by Stephen A. Benton of the MIT Media Laboratory on
"Digitial Holography." No algorithms are given. The references are:
Dallas, W. J., "Computer Generated Holograms," in /The Computer in Optical
Research/, Frieden, B. R., ed., Springer-Verlag, New York, 1980, 291-366.
Benton, S. A., "Survey of Holographic Stereograms," Proceedings of SPIE,
367, August 1982, 15-19.
Tricoles, G. "Computer Generated Holograms: an Historical Review," /Applied
Optics/, 26(20), October 1987, 4351-4360.
I was tempted to type in the section (it's rather short), but not wanting
to violate copyrights I decided not to. Like they say in the Time-Life
commercials: "Read the book!"
From: Steve Swales <steve@image.lle.rochester.edu>
I asked a similar question a while back (though I was looking for CGH using
laser printers specifically) and got lots of me too's, but nothing useful.
I can dig up the 'standard' refs. for you if you don't get them from anyone
else (who probably has them at their fingertips, which I don't), but if
you get anything about CGHs on laser printers, or PD software for CGH, please
forward me a copy, if you would be so kind.
Thanks,
-steve
-------------------------------------------------------+"Come, Watson, come!"
Steve Swales (716) 275-0265,-3857,-5101| he cried. "The game is
steve@bat.lle.rochester.edu (128.151.32.111)| afoot. Not a word!
{decvax,harvard,ames,rutgers}!rochester!ur-laser!steve| Into your clothes and
University of Rochester 250 East River Road| come!" S.H.
Laboratory for Laser Energetics Rochester, NY 14623| 'The Abbey Grange'
From: loeffler@mcc.com (David D. Loeffler)
I am interested in seeing your summary. Sometime ago (1972) I had
just gotten back from Vietnam and was assigned to NSA. While spending
my last 9 months of active duty there I as given a chance to generate
a synthetic hologram. We did not have any fancy graphics facilities
and I had to hack a fourier transform in APL and then by hand plot the
data on a large sheet of graph paper. I then photographed the plot on
a high resolution glass plate and then photographed the resulting
picture on another high resolution plate. I developed the plates
myself and in the end I was able to get a small enough image that we
could view the holograph though a microscope using a laser and we got
what we were looking for. It was fun at the time. We did it because
we found a article that described how one could generate a hologram.
From: stadler@pender.ee.upenn.edu (J. Scott Stadler)
Circuit Cellar INK Issue 14, April/May 1990 has an article on computer
generated holograms. The theory is there, but the holograms that were
generated were very simple. If you need more Info, you can call the
Circuit Cellar BBS at 203-871-1988 8,N,1,300-2400 bps.
Good Luck
From: rick@pangea.Stanford.EDU (Rick Ottolini)
Popular Science Nov 1990 had a cover article on the subject.
The guys at the MIT Media Lab are probably the furthest along,
but they rarely publish.
From: "David D. Loeffler" <AI.Loeffler@MCC.COM>
(Re: previous response)
Sorry but the article is long gone. The researcher I was working with had a
very long last name and I am sure I can not spell it.
From a fading memory - the graph I did was something like 30 by 30 and we
encoded phase and intensity information in a bar by its position and width
in the grid element. We had to do it twice - the second time I doubled
the number of terms in the transform for the calculation (2nd harmonic?).
The original graph was about 3' by 3' and as reduced to about .1" on a side.
Still the holographic image as very small - it would get larger the smaller
we make the graph but there was a limit on the glass plates and the way
we photographed them. Therefore we needed a microscope to view the images.
The image we chose was simple, just the letter "F". The first pass the
letter repeated itself but the second attempt the repeated images where
much farther away and much fainter. Since much of the work was manual we
decided not to continue. I then went on to write simulations of magnetic
domains (bubbles) and permalloy (circuit) elements in a revolving magnetic
field and never went back to the holograms.
Now, if we had a program to generate a hologram and a device to display it
in almost real time then imagine the impact on 3-d graphics!
From: pmartz@dsd.es.com (Paul Martz)
I helped produce a computer-generated hologram, but I don't think what
we did is what you're interested in. We shot film of a rotating object
off the screen of an ESV computer and transferred it frame-by-frame
onto a holographic plate. The results are to be displayed in the
siggraph art show this year, if you are planning on attending.
-paul pmartz@dsd.es.com
Evans & Sutherland
From: keng@zcar.asd.sgi.com (Ken Greenebaum)
There was an article in 'Circuit Cellar Ink' over a year ago about that
subject. At that time there was some discussion on this group about it.
Some people from the MIT media lab had a lot to say.
There was some source code floating around as well.
Please post a Bibliography if you get that far.
Sorry I couldn't be more specific.
-Ken
From: bill@vicorp.com (Bill Arduser)
Dear Larry
Could you please summerize the responses that you get
about digital holography, and post them back to comp.graphics?
I would also be very interested in some refs. Thanks!
From: Burton Rosenberg <burt@Princeton.EDU>
i would like to know what you come up w/.
-burt
From: David Banks <banks@cs.unc.edu>
Marc Levoy (then at UNC-Chapel Hill, now at Stanford)
collaborated with Mike Halle of MIT to produce a
hologram of a head, volume-rendered from medical data
and showing a radiation treatment beam.
I would like a copy of the results you compile. Please
send them to me at banks@cs.unc.edu. Thanks.
David Banks
From: jepsen@godzilla.cgl.rmit.oz.au (Mary Lou Jepson)
I have literally hundreds of references on Computer generated
holography. If you are just starting I recommend these:
From THE COMPUTER IN OPTICAL RESEARCH, the last
chapter by Dallas.
Also the CGH chapter in Hariharan's book OPTICAL HOLOGRAPHY
(publisher Oxford)
from E. Wolf's PROGRESS in OPTICS XVI Chapter III by
Wai-Hon Lee (COmputer Generated Holograms: Techniques
and Applications)
if you are interested in sythetic holograms (like
stereograms -- not usually called CGH -- so as to distinquish
them from holograms where the fringe pattern is actually
computed) check out the papers of Dr. Stephen Benton.
SPIE is soon to put out a book in it's MILESTONE papers
series that groups together what it considers to be the
milestone papers in Computer Generated Holography. The
editor is Dr. Sing H Lee. It may even be out now, it wasn't
two months ago ( the last time I checked..)
Anyway good luck to you. I work in Display CGH, but not much has been
done yet (in comparison to what the public percieves has been done
as a result of things like the holo-deck in STAR-TREK!) There is a LONG
LONG way to go... but it's really fun.
Mary Lou Jepsen RMIT Melbourne, Australia
Article: 4195 of comp.graphics
From: will@rins.ryukoku.ac.jp (will)
Newsgroups: comp.graphics
Subject: Re: Digital Holography
Summary: INFO
Message-ID: <261@rins.ryukoku.ac.jp>
Date: 9 May 91 03:26:13 GMT
Organization: Ryukoku Univ., Seta, Japan
The following is from previous postings on this subject:
>> From: wiml@milton.acs.washington.edu:
There was a "how to" article on this in the Apr-May 1990 issue of
Circuit Cellar Ink ('issue 14'). The author managed to generate holograms
by taking a picture of his VGA screen and photoreducing it, but it should
be possible to photoreduce, say, laser printer output and get better
results from having more dots ...
Last time this topic came up (around Apr-May 1990) there was some
source code posted to do the calculation. I didn't save any of it, however.
>> From: halazar@media-lab.MEDIA.MIT.EDU Sat Jan 12 13:17:17 1991:
Taking a momentary break from the ol' thesis to answer this repeated
and nagging question, "What about those computer generated holograms,
anyway?", he dived in....
ALL 94% OF YOU EVER WANTED TO KNOW ABOUT COMPUTER GENERATED HOLOGRAMS
A hologram is a medium that records the direction and intensity of
light, in contrast to a photograph, which only records light's
intensity. Typically, the holographic material (usually a high
resolution photosensitive emulsion) records an interference pattern
caused by the simultaneous exposure of two sources of coherent light:
one reflected from the object being imaged, the other directly from a
reference or carrier beam. This interference pattern is such that if
the developed hologram is placed in the original reference beam, light
is diffracted or reflected in such a way that the original object
appears to float in space at its original location. The spatial
relationship between the viewer and objects in the scene appears
identical in "real life" and in the hologram. More complicated
holographic processes can produce white-light illuminable, even
multi-color holograms.
Computer generated holograms replace the objects in the scene with
synthetic objects. Presently, two major types of computer generated
holograms exist. The first, and the most difficult to produce, is
commonly called a CGH (computer generated hologram; yes, brace
yourself for confusion). CGHs are made by calculating the
interference patterns to be recorded on the holographic plate by first
figuring out what part of the synthetic object is visible from what
part of the hologram, then summing the phase and amplitude of the
light that each part of the object reflects. For interesting objects,
this calculation must be performed for many points on the hologram
because the spatial frequencies range from 100-1000 fringes per
millimeter. Recording the information onto the holographic medium is
also a problem; for CGH optical elements, for instance, the pattern
is often recorded using an electron beam writer.
Although computing fringe patterns may seem like the obvious way to
make computed holograms, the technique is impractical for large,
complicated, static images. CGH is computationally viable for simple
or repetitive interference patterns, such as optical elements.
Computing fringe patterns is also useful for dynamic holography (or
holographic video). In MIT's system, data from a memory store is
converted to an analog signal and used to modulate an acoustic signal
emitted from a transducer. This transducer is coupled to an optical
crystal in which the sound waves form compression patterns capable of
diffracting light. A small crystal can be used to "sweep out" a large
diffractive area. The diffractive pattern in memory is a holographic
fringe pattern, currently computed at up to several frames per second
(for simple wireframe objects) using a 16K processor Connection
Machine 2. The memory store is the CM2's framebuffer. However, the
image size is still quite small (3x3x3 cm) usable volume updated at
40Hz, I'd guess), and complicated objects take a long time to compute.
High quality synthesized display holograms are almost exclusively
produced using a technique known as holographic stereography. If a
hologram is analogous to a window onto the original scene, then a
stereogram is a series of many slit small windows, each only big
enough horizontally to fit the pupil of the viewer's eye when the
viewer stands up next to the plate. Instead of a view onto a 3D
scene, each little window has information about a single, 2D
projection of that scene. These projections can be created using a
moving cinema camera or standard polygonal or raytracing computer
graphics program. The different views are computed by moving the
camera, with its lens axis always facing perpendicular to the camera's
direction of travel, horizontally through the view zone. A new image
of the scene is captured every pupil's width or so. To make the
stereogram, these images are projected using laser light onto a
diffusion screen, and a vertical slit of a holographic plate is
exposed to the screen and to a reference beam. The geometrical
relationship of the slit to the projection screen is the same as the
relationship between the camera and its plane of focus when the view
for that slit was captured. So when the hologram is illuminated, a
viewer looking through the plate actually looks through two different
slits, and thus sees to different image perspectives, the same ones
that would have been seen were the viewer really looking at the
object.
A second hologram, called a transfer hologram, is commonly used to
allow the viewer to stand some distance from the stereogram. The
transfer hologram is actually a hologram of the slit hologram. When
illuminated, the transfer hologram projects an image of the slits of
the master hologram out into space, so the viewer can easily step into
the master plane without suffering facial lacerations. Because images
are only captured side to side, the stereogram exhibits only
horizontal parallax: vertical viewer motion doesn't change the
appearance of the subject.
The holographic stereogram has a lot going for it. The input
perspectives are relatively easy to produce using widely available
computer graphics techniques. In general, interesting and realistic
graphics hacks look even more interesting and realistic in a
stereogram. Only about 100 perspective images need to be generated for
a standard 20x25cm (8x10") stereogram. Transfer holograms can be
made in full, vibrant color, with a little work. Size is almost
unlimited; with a little cleverness, a rig that would fit in a
suburban garage could crank out life size computer images of Miatas.
Fringe-pattern-type CGHs just aren't anywhere near as convenient,
useful, or satisfying, and won't be for quite a while.
But, sadly, only a handful of places in the world can make
stereograms, and even fewer know how. Most of them are research
facilities, like our group. The rest are usually involved in mass
production or commissioned work so its tough unless your images or
data is really cool. A full, high quality stereogram lab costs about
$500 thousand. And the holography market is hardly booming. The
technology almost exists for a holographic printer computer
peripheral, which would open the world of low cost (couple dollars a
page), high quality 3D hardcopy to many more people, but no one wants
to put much money into it. You'd think the 1 meter square computer
generated hubcaps in the basement would convince somebody....
So the short answer is, "No, it isn't hard to compute a holographic
image. It's really hard, however, to make it into a hologram."
Unless you'd like to be a lab sponsor, that is.
--Michael Halle
Spatial Imaging Group
MIT Media Lab
mhalle@media-lab.media.mit.edu
HOPE THIS HELPS.
William Dee Rieken
Researcher, Computer Visualization
Faculty of Science and Technology
Ryukoku University
Seta, Otsu 520-21,
Japan
Tel: 0775-43-7418(direct)
Fax: 0775-43-7749
will@rins.ryukoku.ac.jp
From: m2xenix!onion!tessi!loop!dont@uunet.UU.NET (Don Taylor)
While I worked for Tektronix I found a literature search that had been done
on computer generated holograms. In particular it mentioned a book on
Digital Holography that was "a must have if you were going to do anything
in the field". I did a couple of book searches but failed to turn up a
copy. I have the reference around here somewhere or I could lean on a
couple of friends to get a look at the notes again. I think the author
might have been a Chek.
I would appreciate hearing what your receive.
Thanks
Don Taylor
503-235-6853
loop!dont@tessi.UUCP
dont@loop.UUCP
tessi!loop!dont@nosun.west.sun.com
(END OF SUMMARY)
--
--
Larry Baker
NEC America C&C Software Laboratories, Irving (near Dallas), TX
baker@texas.csl.dl.nec.com cs.utexas.edu!necssd!baker