Try some OPTICS
Holograms Drawn by Hand
|Giant-fringe holography? nondiffractive holograms? single-fringe holograms? scratch holograms? sandpaper holograms? abrasion holograms? scratch-o-grams? holosketches? wire-brush holograms? car-hood holograms? phonograph holograms? incoherent holography? Aha: chatoyant holography!|
I've stumbled across a technique for drawing holograms directly upon a
plastic plate by hand.
It sounds impossible, but I've been sitting on the
livingroom sofa making holographic images of floating polyhedra, words, 3D
starfields, opaque objects, etc. No laser, no isolation table, no
darkroom, no expensive film plates. This takes nothing more than a
compass and some scraps of plexiglas. Too cool, if I say so myself!
There's an interesting story behind this technique, but first, the instructions.
Obtain a small piece of acrylic plastic and a good, non-wobbly set of
"dividers" (a compass with two points.) I used a $10 compass from an art
supply store and replaced the pencil lead with the supplied metal point.
The compass must be the type with an adjusting screw to set the spacing of
the points. Or, you can use a 4-in. piece of wood with a couple of
finishing nails driven through it to form a pair of points. For the
plastic, a CDROM 'jewel case' works fine.
Next, use a marker to draw a simple pattern such as the letter "V" near
the lower edge of the plate. This will be the image that we'll encode
onto the surface. Draw your "V" less than 1 in. tall (2cm). Set the
spacing of the compass points to a couple of inches. Place one point on
of the small "V" at the bottom of the plate, and *gently* drag the other
point lightly across the plastic so you make an arc-shaped scratch that
looks something like the figure below.
This is your first scratch. It helps to tilt the compass so the point
trails across the surface and does not dig in or chatter. The scratch
should be easily visible, but not extremely deep.
The scratch should be dark and polished, not white and dusty. It should
show a small highlight when viewed in sunlight or under a pointsource
illuminator such as a small, clear light bulb. Now, while keeping the
dividers at exactly the same spacing, place the point at a different place
on the little "V" and use the other point to make a single circular
scratch as before. Do this again and again, ten times or more, each time
placing the point on a different spot on the little "V". When completed,
the overlapping arc-shaped scratches should look like you've swept a bit
of sandpaper across the top of the plastic plate. The little letter "V"
should be full of holes made by the other point of the compass.
[ Detailed Instructions]
To view the resulting hologram image, observe the scratches in sunlight.
If your plate is transparent it helps to place something black behind it,
or to paint the rear surface dark for contrast. While holding the plate
chest-high with the little "V" towards your body, rotate yourself around
so you face the sun, tilt the plate up and down, and look at the
scratches. At a certain angle you will see a moving highlight in the
scratches. It will look like a collection of little stars, a mini-
constellation in the shape of the letter "V". That's the hologram. If
you go back and add more and more scratches in between the ones you
already made, eventually your letter "V" hologram will look like solid
white lines rather than rows of stars.
When viewed with both eyes open, the "V" seems to float deep within the
plastic. Its virtual depth is determined by the compass: if the spacing
of the points was set to 1 in., the image appears 1 in. below the plastic
surface. You can also hold the plate upside down, with the scratches at
the edge of the plate towards your body, and the holographic image will
float in space above the plate.
Several hologram plates.
(Obviously you cannot see the 3D effect in this flat photograph.)
Depending on the tilt of the plate with respect to the sun, you might
accidentally discover the "pseudoscopic" image of the "V," and it may
appear to float *above* the surface of the plastic. Tilt the plate to
bring the far edge up and towards you and you'll then find the
"orthoscopic" image floating deep within the plate.
If you had inscribed your entire name on the plastic, you'd now be seeing
it down there within the surface. (hint hint!) It's also possible to draw
complicated 3D objects by varying the compass spacing as you slowly draw
glowing lines one point at a time. The distance between the compass
points controls the depth of the hologram-dots you are making. I've been
drawing cubes, pyramids, and holes with glowing stars at the bottom. As
with conventional holograms, opacity effects can be achieved by
controlling the location of the endpoints of the scratches. And many
other sophisticated effects produced by conventional rainbow holography
can be duplicated in black plastic and scratch patterns.
CHANCE FAVORS THE *CURIOUS,PLAYFUL* MINDAll this all started while I was walking along the rows of cars in the parking lot at work. I noticed this one black station wagon hood that had a number of glowing highlights created by the sunlight. Typical science hobbyist response: I stopped and began playing with them. I was moving my head back and forth in order to make them slide around, when I noticed that some of the highlights seemed to exist a few inches WITHIN the surface of the car hood. I've long been interested in stereo images, so I started examining these "deep" highlights in detail. Some of the larger ones had an interesting structure, appearing as an 8 in. circular blotch of light with a radial pattern of filaments and a mottled central area. All these highlight-patterns seemed identical, and were floating at various depths within the car hood.
Gritty car hood after careful "polishing" with a dry paper towel.
The handprints in the above photo might appear to be on the surface of the hood, but in real life they look holographic and seem to float about one foot deep within the surface of the hood. Appears like white fishes in a dark pond.
With a start I suddenly I realized what I was seeing. It was incredible:
each highlight was in the shape of a wool polishing mit, with matted
fibers in the center surrounded by outwards-pointing wooly filaments! The
matted part was in the shape of a human hand! There were several of them
floating at various depths all over the car hood, with some of them even
floating in space *above* the hood. They had been invisible to me, but
then they weren't.
Science is perception!
It wasn't long before I had half the optosensor engineering department out
there acting like fools, moving their heads back and forth in front of
this black station wagon. I searched through the rest of the sunlit
parking lot and found several other cars with glowing distorted handprints
deep within various surfaces. Once you realized they were handprints, the
shape was unmistakable.
I proposed several crude theories to explain the phenomena, as well as
numerous hoaxes which could be done via Elvis-shaped polishing mitts to
encode miraculous images onto everyday objects. (The Hood of Turin?) It
was about a week before I figured out what was really going on. The
images were naturally-occurring holograms. The owner of the car had
obviously polished the hood with a dirty lambswool mitt, and the millions
particles of grit in the mitt traced out millions of nearly-parallel
scratches in the black paint. The particular hand motion had created a
geometry of abrasion patterns which turn out to be nearly identical to the
interference patterns which make up those embossed-foil whitelight
Benton rainbow holograms.
But there was something extremely weird going on here (I mean even
more weird than hood scratches causing images!) These scratches have
random spacing. They seemed to be functioning as holograms without the
benefit of optical interference. This is impossible of course, since
holography is completely based upon interference effects. However, the
"Rainbow" hologram technique invented by Benton at MIT allows a hologram
to function regardless of illumination frequency. The optical bench for
the classic single-stage "Rainbow" holography setup includes a horizontal
slit which produces relatively large horizontal swatches of fine-line
interference patterns on the film (figure A above.) The recorded
interference pattern encodes the depth information as variations in
orientation of the fringes across the stripe. In Benton's Rainbow
Holograms, only the fringe orientation is important. The fringe
spacing (wavelength) is not. Once I was clued in by the existence of the
car-hood holograms, I realized that I could interpret Benton's white-light
technique as allowing holograms to function regardless of *fringe
spacing.* Frequency-independence leads to size-independence of fringes,
figure B above. Nobody seems to realize that a Rainbow Hologram will
still function even when the spacing of its fringes was made random. Or
even if it were to be made immensely large.
No one seems to realize that the well-known "Rainbow Hologram" technique
can also let you produce holograms which are not based on optical
interference at all. This makes it possible for you to create holograms
where the "interference fringes" are so large that they are easily seen
by the naked eye; where they are more like the grooves of an LP record
than like the patterns on a CDROM. And if the arrays of hyperbolic
interference fringes in a conventional Rainbow Hologram are replaced by
widely-spaced, hand-ruled scratches on a plastic plate, it becomes
possible to draw complicated holographic images directly by hand with a
sharp tool. Neolithic holography! Multiple parallel scratches aren't
necessarily required, and
circles can replace the hyperbolae. The circular-scratch technique is
able to produce holographic images, and sweeping circular motions of
gritty polishing mits can produce these holograms accidentally.
Hand-drawn cube hologram
(STEREO PAIR, for crosseyed viewing)
Has anyone heard of this trick before? I've yet to find it mentioned in
any (1995) holography article or text. It's starting to look like this is
(AHA! Someone clued me in. A 1992 paper by Plummer & Gardner (ref. below) does detail just such a discovery. The authors completely analyse the math behind the reflections made by arrays of circular scratches produced by the orbits of a lapping tool on a metal mirror. -Bill B., 10/23/95The scratch-hologram technique might be very useful in reducing the amount of data required for computer-generated holography. The size independence characteristic suggests that billboard-sized holograms wouldn't be impossible to build. Also, an incoherent-light holo-camera is feasible: if an object is illuminated with structured light resembling a dense random starfield and is photographed at 2f distance by a camera having a curved slit-aperature over its lens, and if the resulting plate is used to etch fine lines onto a metal or plastic surface, the result will be a photographically produced "scratch hologram" of the original object.
Conventional Rainbow Embossed holograms do trounce it badly in the
brightness and sharpness catagories, but conventional techniques won't let
you create a "physics educational" hologram with giant interference
easily viewed with the unaided eye. And conventional holography won't let
you sit by the side of a lake in Vermont with plexi and dividers, drawing
holographic virtual images of floating polyhedra by hand.
- Bill Beaty
P.S. The required tools are so simple that ancient peoples could have
drawn these images in hardened sooty resin pools with wooden tools, had
they but known the trick. Several ancient civilizations were heavily into
geometry. I wonder if any artifacts exist in storage somewhere which
appear to have some 'sandpaper marks' on their polished surfaces... ;)
Matthew Brand, "Specular Holography," Applied Optics V50 #25 pp5042-5046 (2011)
Nils Abramson, "Incoherent Holography" Proc. SPIE Vol. 4149, pp153-164, Holography 2000, Tung H. Jeong; Werner K. Sobotka; Eds.
W. Plummer & L. Gardner, "A mechanically generated hologram?" Applied Optics, V.31 No.31, pp. 6585-6588 (Nov 1992)
Hans Weil, 1930s work
E. Garfield, Essays of an Information Scientist, V5 pp348-354 1981-82 ISI's "World Brain" by the late Gabriel Liebermann: The World's First Holographic Engraving (3ft x 4ft scribed aluminum), also Liebermann's site and machine drawings
Jearl Walker, WHAT DO PHONOGRAPH RECORDS HAVE IN COMMON WITH WINDSHIELD WIPERS? The Amateur Scientist, Scientific American. July 1989 Vol261 No1. pp106-109
"A Binocular Illusion" by Paul Kirkpatrick in American Journal of Physics. Vol. 22, No 7. Page 492. October 1954.
"Reflections on a gramophone record" by J.B. Lott in Mathematical Gazette. Vol. 47, No. 360. Pages 113-118. May 1963.
F. S. Yu, A. Tal, H. Chen, Optical Engineering, Vol.19 No.5, pp. 666-678, "One-step rainbow holography: recent development and application."
W. Siemens-Wapniarski, M. Givens, Applied Optics, March 1968, vol 7 no 3, p535 "Experimental Production of Synthetic Holograms."
H. Caulfield, National Geographic, Vol.165, No.3, p. 372
Homemade (laser) Holograms : The Complete Guide to Inexpensive,
The Complete Book of Holograms : How They Work and How to Make Them
Holography Handbook : Making Holograms the Easy Way
Laser Focus World, March 2003
TLC's show While you were Out had a scratch-holo in Thinking man's room (see the "after" version)
Helix #65, April/May '99
Yesmag Science Magazine, #9, Spring '98 p25...and was featured in an old episode of "The Big Bang", a children's science TV show in the UK.