EARLY HISTORY OF
SCRATCH/ABRASION HOLOGRAPHY
In article <3u3tju$bv8@news1.halcyon.com>, sciclub@chinook.halcyon.com says...
Hi, I'm writing a hobby article about a frequency- and size-independent
holography method based on low duty cycle square gratings (rather than the
sinusoid gratings of conventional holography.) It's quite neat, and allows
crude holograms to be made without a laser.
I'm looking for similar articles, but have so far been unable to find any
reference to such a thing in the U. Wash. library's collection of
journals. Might anyone here be familiar with similar work? Or with
holography based on oriented fibers, mechanically blazed gratings,
aperiodic gratings, etc.?
Date: Sat, 22 Jul 1995 11:11:49 +0000
Subject: Re: Holography without interference
William-
The way you make this type of "hologram" is to lay a Ronci ruling (striped mask) onto of a piece of black and white film. Expose an image onto it using a conventional lens system. Then process the film, and bleach it if you want. The bleached film will look clear.
To read the picture use a 4F system. Put the film in front of a lens, then illuminate it with a collimated beam of light. At the focal length of the lens you will see a focal point and two side spots. Put a block up so only one side spot will pass. Reimge the beam with another lens. you will get the picture back.
This is called saptial filtering. the Ronci rulling acts like a carrier, similar to an AM signal carrier for radio waves. You can superimpose many images on the film and recall them by moving the block. I've seen 16 on one clear film. You can also encode color pictures on black and white film.
If you are really interested, and are going to do the experiment I can look up my lab notes and send them to you
> : In article <3u3tju$bv8@news1.halcyon.com>, sciclub@chinook.halcyon.com says...
> : >
> : >Hi, I'm writing a hobby article about a frequency- and size-independent
> : >holography method based on low duty cycle square gratings (rather than the
> : >sinusoid gratings of conventional holography.) It's quite neat, and allows
> : >crude holograms to be made without a laser.
> : >
> : >I'm looking for similar articles, but have so far been unable to find any
> : >reference to such a thing in the U. Wash. library's collection of
> : >journals. Might anyone here be familiar with similar work? Or with
> : >holography based on oriented fibers, mechanically blazed gratings,
> : >aperiodic gratings, etc.?
Date: Sat, 22 Jul 1995 20:50:15 -0700
Reply-To: Forum for Physics Teachers
Sender: Forum for Physics Teachers
From: William Beaty
Subject: Holograpy without interference
Remember last year when I was asking about naturally-occuring holograms and axicon lenses? I've finally given up on trying to track down this info on my own. I'd like to see if anyone on phys-l has heard of something similar to the following.
It all started when I noticed some glowing highlights in a polished black auto hood. Some of the highlights were in the shape of human handprints, but they appeared as virtual images a few cm below the surface of the hood. Some of them actually floated above the surface. They were produced when a slightly-gritty polishing cloth was swept in a particular trajectory across the hood, which created many thousands of fine scratches in the finish in a special pattern. I worked out the mechanism behind these apparent holographic images and found that they were similar to Benton "rainbow" holograms, but lack interference patterns.
It seems that the Benton technique, in creating frequency independence, also removes any *need* for interference patterns. If one takes a whitelight hologram and replaces the hyperbolic gratings with widely-spaced hand-ruled scratches, the hologram still works!
I've been sitting in my living room making floating 3D polyhedra, glowing letters, 3D starfields, opaque objects which occlude background patterns, etc. All with a set of dividers and some scraps of black plexiglas. Too cool, if I say so myself.
In one-step Benton holography, the beam from the object is masked with a slit aperture near an imaging lens, with the result that each point on the object creates a sharply-masked horizontal stripe of interference pattern on the film plane. If the spatial frequency of the sets of hyperbolic diffraction fringes is vastly increased, and if the 50/50 duty cycle of the fringes is reduced to under 10/90 ( as in widely spaced ruled scratches,) the multiple orders of the diffracted beam become blended into a continuous fan of light. But the geometry of the of the Benton technique guarantees that the hologram will still reconstruct an image. There's no overall interference involved: the ruled scratches can be fractions of mm apart, all. When done on black plexi, the hologram looks like the grooves in an old LP album, rather than like a rainbow-hued CD platter. However, the resulting hologram has fully stereoscopic 3D, and objects can be created which extend below and above the plane of the plastic. The resulting hologram can be reconstructed with white pointsource illumination or with sunlight.
Date: Sun, 23 Jul 1995 13:37:06 +0000
Subject: Re: Holography without interference
> I've heard of this one. It's similar, and it should give me some leads.
> However, it's not what I'm doing. I'm looking for info on a trick based
> on a combination of Benton rainbow holography and mechanically ruled
> gratings. In one-step Benton holography, the interference pattern is
> masked with a slit aperture so that each point on the object creates a
> horizontal stripe of interference pattern on the film plane. If the sets
> of hyperbolae are replaced with hand-ruled circular lines while
> preserving the rest of the geometry, the frequency-independance effects of
> the Benton technique guarantee that the hologram still works. There's no
> overall interference involved: the ruled scratches can be fractions
> of mm apart, can have random spacing, or can be single scratches with no
> adjacent scratches at all.
>
> The resulting pattern can be viewed under white pointsource illumination
> or sunlight. It's possible to use this technique to hand-draw (slowly, a
> point at a time) words and pictures, simple 3D polyhedra, opaque objects
> which occlude a background pattern, etc. A pair of dividers makes the
> curved lines, and a piece of black plexiglas acts as the 'film.'
>
This sounds like hand made zone plates, or Kinoforms. I don't quite understand the procedure. You draw grating lines within a slit shaped area on a plexi substrate?
> Date: Sun, 23 Jul 1995 16:46:03 -0700 (PDT)
> Subject: Re: Holography without interference
>
> To hand-draw a 'pontillistic' virtual image, you simply draw large numbers
> of scratches with various positions and radii, one for each glowing point
> on the desired image. This of course takes a bit of time when done
> manually. I'm currently working on a form of 3D photography based on the
> above.
I have done something like this, using zone plates. Drawing zone on paper then photographing onto B&W film to reduce size. I have the following comments:
1. F# is dependent on number of zones. i.e. your efficiency is going
to be very low
2. efficiency can be increased 3x by bleaching
3. with scratches you will get many higher diffraction orders reducing
your signal to noise ratio. At best you would expect a S/N of 1:3
I wrote a program once that drew zone plates corresponding to each point I wanted to produce (sort of a Fresnel Transform). It added the zones for an array of points then printed on a piece of paper. I photograhed and bleached it. It worked but had those shortcommings.
> Date: Wed, 26 Jul 1995 07:40:01 -0700 (PDT)
> Subject: Re: Holography without interference
>
> > > To hand-draw a 'pontillistic' virtual image, you simply draw large numbers
> > > of scratches with various positions and radii, one for each glowing point
> > > on the desired image. This of course takes a bit of time when done
> > > manually. I'm currently working on a form of 3D photography based on the
> > > above.
> >
> > I have done something like this, using zone plates. Drawing zone
> > on paper then photographing onto B&W film to reduce size. I have the
> > following comments:
> >
> > 1. F# is dependent on number of zones. i.e. your efficiency is going
> > to be very low
>
> This is true. These scratch-holograms look good in sunlight against a
> dark background, but otherwise are too dim for realworld application.
>
> > 2. efficiency can be increased 3x by bleaching
>
> Since the scratch-hologram operates by reflection/refraction more than by
> diffraction (when the scratch widths are >> wavelength), phase effects are
> not going to be very important. Would a single bleached line in the
> emulsion act as a reflective fiber? If not, bleached emulsion might not
> record the scratch-hologram at all. But the use of macroscopic scratches
> >> than light wavelengths would allow mirror effects and blaze angle to be
> put to use.
Although scratches are refelcting, you must have some sort of diffraction happening for the curved line to transform into a spot.
>
> > 3. with scratches you will get many higher diffraction orders reducing
> > your signal to noise ratio. At best you would expect a S/N of 1:3
>
> Ah, but the higher diffraction orders are the key to the effect. The
> geometry of the Benton Rainbow Hologram makes reconstruction operate
> correctly regardless of illumination frequency, recording frequency, or
> spacing of the interference fringes. The higher orders would not add
> noise, they would just make the hologram viewable from a wider range of
> angles (and of course make the image dimmer) Another way of looking at it:
> the scratch-hologram trick is based not on diffraction gratings (zone
> plates), but on single reflective scratches. Sort of a single-slit
> diffraction version of holograpy.
I don't get this. If I remember correctly a rainbow hologram gives stereoscopic effect left to right and no color, and color top to bottom but no stereo effect. The scratches would still give color, just as a single diffraction slit gives color.
>
>
> > I wrote a program once that drew zone plates corresponding to each
> > point I wanted to produce (sort of a Fresnel Transform). It added the
> > zones for an array of points then printed on a piece of paper. I
> > photograhed and bleached it. It worked but had those
> > shortcommings.
>
> Very interesting! But wouldn't there be cross-modulation, since printer
> ink does not obey superposition? Black + black <> 2(black). A hobbyist
> published something similar years ago about use of laser printers for
> this. He did it with a 35mm camera and a 300dpi printer, and
> reconstructed simple geometric figures.
Have you made these scratch devices and do they work?
Date: Tue, 1 Aug 1995 07:41:03 +0000
Subject: Re: Holography without interference
> > >
> > > Very interesting! But wouldn't there be cross-modulation, since printer
> > > ink does not obey superposition? Black + black <> 2(black). A hobbyist
> > > published something similar years ago about use of laser printers for
> > > this. He did it with a 35mm camera and a 300dpi printer, and
> > > reconstructed simple geometric figures.
No cross coupling, the functions are multiplied not added in the supperposition. so the zone values go between zero and 1 and are multiplied, so 1x1=1.
> >
> > Have you made these scratch devices and do they work?
>
> Yep! The first thing I did was to sign my name as a 2" deep virtual image
> in a piece of plexiglas. I drew it one point at a time with a compass,
> which took quite a while. The letters appear as dotted lines, and the
> overall image is flat and parallel to the surface of the plexi, only it's
> 2" deep and require pointsource illumination for viewing. Looks
> impressive in sunlight. It appears white, with maybe the tiniest color
> speckle from the thinner scratches. As with rainbow holograms, if you
> rotate the plate 90degrees, the depth disappears.
what is the recipe for the curvature of the striations?
> No cross coupling, the functions are multiplied not added in the
> supperposition. so the zone values go between zero and 1 and are
> multiplied, so 1x1=1.
But it was my impression that multiplication is the same as cross modulation. If a big black band is printed over several smaller ones, it wipes them out. But if a big stripe of phase-shift is exposed on top of finer stripes in a bleached emulsion, it merely adds, giving superposition of signals, and so no cross coupling. In electronics a signal multiplier is the same as a modulator, and generates sum and difference frequencies.
>
> what is the recipe for the curvature of the striations?
>
To generate virtual writing, use the same radius always. Radius of curvature is approximately equal to perceived depth of the spots. To give it an initial try, use a small radius, like a couple of cm. The first one of these I ever made had a 30cm radius and was very hard to view.
I've also managed to make 'naturally occurring holograms' of my hand by using a gritty paper towel and a polished black surface. All the points on the image are drawn simultaneously, and the resulting image is flat.
> >Date: Fri, 25 Aug 1995 07:30:02 PDT
> >William Beaty wrote:
> >
> >>>Here's how to try out this technique:
> >I am interested in trying this but have one question. Should the
> >scratch be just an arc as shown (about 90 degrees long) or a full
> >circle?
The arc-shaped scratches are designed to give a stereo orthoscopic image when illuminated from above. The length of the arc (angle, actually) controls the angle of view. A very short arc could be used, but then the illuminator and the observer would have to be at just the right angles before the image could be viewed. Try drawing one of these patterns, and you'll rapidly get a feel for how the image behaves.
Do try drawing full circles too, this will give an orthoscopic and pseudoscopic image. I might be stretching the definition of "orthoscopic", etc., here, but two images do appear when full-circle scratches are illuminated, and the horizontal parallax does make one image appear to float within the plate, while the other floats in front of it.
Note that these images are composed of reflective highlights perceived as moving along the scratches. Look for the image *in* the scored area. Similar highlights can be observed when a record album is held in sunlight or when a streetlight shines through an auto windshield that's been scored by the wipers. If conventional holography corresponds to the bands of color seen in a CDROM platter, then the above "holography" corresponds to the glistening grooves of old vinyl records!
. . . . . . . . . . . . . . . . . . . . . uuuu / oo \ uuuu
. . . . . . . . , . . . . . . . . . . . . . . . . . . . .
William Beaty voice:206-781-xxxx
bbs:206-789-xxxx cserv:71241,3623
EE/Programmer/Science exhibit designer
http://amasci.com/
Seattle, WA 98117 billb,eskimo.com
SCIENCE HOBBYIST web page
>Subject: RE: Holography without interference
>Date: Tue, 29 Aug 1995 13:46:59 PDT
>
>Mr. Beaty,
>
>I tried your abrasion holograms by spelling the word
>"Science" with ever increasing radii. It worked beautifully;
>I saw the letters at ever increasing depth and could change
>my view to see the perspective change.
>
>The effect however is not holographic since there is no
>recorded phase information. If one were to take a picture
>of the image, all of the letters would be in focus no
>matter how deep they appeared. Also, you cannot have
>obscuration of a bright object behind a dark one.
>
>The effect is basically that of many small mirrors (the small
>portion of the groove that bisects the angle b/n the source
>and the eye) each acting as its own point source. These are
>the bright pixels used to create the image. The arched grooves
>are therefore the paths that the pixels follow as one's
>perspective of the image changes.
>
>While it's not holography, the effect is really cool and
>I plan to play with it quite a bit. Thanks for sharing
>this with me.
>
>Date: Wed, 30 Aug 1995 13:33:17 PDT
>From: William Beaty
>>>I tried your abrasion holograms by spelling the word
>>>"Science" with ever increasing radii. It worked beautifully;
>>>I saw the letters at ever increasing depth and could change
>>>my view to see the perspective change.
>>>
>
>Excellent! Be sure to saw off the bottom of the plastic plate where the
>pinpricks lie. Then you'll only be left with the abrasion pattern, with
>nothing to give away the "secret message" to your befuddled collegues. ;)
>
>>>The effect however is not holographic since there is no
>>>recorded phase information.
>
>Heh, I was waiting for this. Whether or not it is holographic depends on
>how narrowly you define the word. Since this 'hologram' technique does
>not use interference, one COULD use this to argue that it is not holography.
>But phase information is stored in these holograms.
>
>>>If one were to take a picture
>>>of the image, all of the letters would be in focus no
>>>matter how deep they appeared.
>
>Not strictly true. The bright points of light are actually images of the
>sun being viewed through long, thin, curved reflectors. What do you see
>when you view the reflection of a distant point in a cylindrical mirror?
>You see a distorted image, but the phase of the wavefronts are not
>destroyed. These 'abrasion' holograms contain horizontal phase information
>but not vertical, which is also the case with rainbow holograms. The
>horizontal parallax and 3D images exist because the images DO have
>virtual depth (but astigmatically, only in the X direection)
>
>>> Also, you cannot have obscuration of a bright object behind a dark one.
>
>You can if you know the trick. It's the same as with conventional holography.
>If I were to build a conventional hologram by superposing zoneplate lenses
>in order to generate image points one at a time, I might get the
>impression that holography only generates transparent images and cannot be
>made to produce opacity effects. But this is not true. Conventional
>holograms are able to record opaque objects because the resulting zoneplate
>lenses have missing sections where the particular image point is being
>obscured. In the 'abrasion hologram' it is possible to achive the same
>effect by limiting the extent of the curved scratches. I've managed to
>hand-draw a black square in front of a glowing starfield, and a
>glowing-edge square which obscures the letter "B" deeper behind it. (The
>"B" can be viewed by tilting the plate so you can see AROUND the
>foreground image of the opaque square.) Opaque objects aren't simple
>to create by hand, but aren't impossible.
>
>Glad you had fun with this effect!
>
Date: Sat, 26 Aug 1995 12:18:17 +0500
Subject: Holography without interference ? The references.
Hello Mr. Beaty,
Here is the reference on "abrasion holography" :
*) W. T. Plummer and L. R. Gardner, "A mechanically generated hologram",
Applied Optics Vol.31, No. 31 (1 November 1992) pp.6585-6588.
Plummer and Gardner have given a nonholographic theory for 3D image
reconstruction from mechanically abraded "pseudoholograms", which is,
probably, the first report on mechanically recorded holograms.
It may fit your experimental results.
Date: Wed, 6 Sep 95 15:48:29 -0700
To: billbeskimo.com
Subject: re: abrasion holograms
I tried your technique for "abrasion holograms" on a clear acrylic sheet and
eventually got an excellent result. Initially my scratches were too deep
(my stylus was too sharp) and I found that I got the best results by barely
touching the stylus to the plastic. (If the stylus makes an audible noise as
it scratches, I'm pressing too hard.) I created a wire-frame cube by etching
circles of two different radii along the edges of a drawn square (to form the
front and back faces of the cube) and then etching concentric circles spanning
those radii at the four corners of the drawn square (to form the cube edges
which vary in depth). Now I'm going to try to experiment with drawing partial
arcs to try to create a solid view which shows at most three faces of the cube.
I like your idea of creating holographic sculptures with curved polished
metal rods. I might try a scaled-down version with some wire. Thanks for
the suggestions... I'm having better success with this than I've had with my
photo-chemical holographic attempts out in my garage.
Date: Mon, 14 Aug 1995 21:46:12 -0500 (CDT)
Subject: Abrasion holograms
Bill,
I am a physics teacher at a high school in southern Texas. Myself and one of my students are very interested an trying to reproduce the type of three-d image you described. After reading your posting, I am not sure what you mean when you are referring to "dividers." My assumption is a device similar to a mechanical compass (circle-drawing type) with one leg on the object and the other moved in a circular arc while scratching the plexiglass. Is this correct? Is there just one scratch for each point chosen on the object?
Any information (or source for such) would be greatly appreciated.
Date: Wed, 23 Aug 1995 12:42:43 -0700 (PDT)
To: info-holo@MOM.SPIE.ORG
Subject: Holography without interference
I'm writing a hobbyist article on an interesting pseudo-holographic effect I've discovered. I'm collecting a list of references, but I've yet to run across any paper which describes the effect. I'd like to find out if anyone here has heard of it before.
Benton Rainbow Holograms are somewhat frequency-independent. This is the same as saying that they're somewhat independent of fringe spacing. If you take the interference pattern from a Rainbow Hologram, change the sinusoidal fringes into low-duty square waves to generate multiple orders, then vastly reduce the spatial frequency, the hologram will still reconstruct the original image. Even if the "fringes" are 1mm apart the hologram still works!
I've been making simple whitelight holograms by scribing them directly onto a piece of polished acrylic with a sharp tool. Starfields and polyhedra are quite easy to do. Has anyone heard of anything like this? Older papers on Rainbow Holograms don't mention it, and I'm working my way up to more recent ones.
. . . . . . . . . . . . . . . . . . . . . uuuu / oo \ uuuu
. . . . . . . . , . . . . . . . . . . . . . . . . . . . .
William Beaty voice:206-781-xxxx
bbs:206-789-xxxx cserv:71241,3623
EE/Programmer/Science exhibit designer
http://amasci.com/
Seattle, WA 98117 billb,eskimo.com
SCIENCE HOBBYIST web page
Date: Wed, 23 Aug 1995 22:58:17 -0700 (PDT)
From: William Beaty
To: info-holo@MOM.SPIE.ORG
Subject: Abrasion holograms
Here's a quick rundown on making "abrasion holograms"
In Rainbow Holograms the fringe pattern generated upon the film by each point on the object is a masked horizontal stripe, with the orientation of fringes looking something like this crude depiction:
||||||//////====----====\\\\\\||||||
It's similar to a small slice of a zoneplate lens.
In a rainbow hologram the image is recorded as an array of these stripes, with the X,Y position of each stripe corresponding to the X,Y position of each object point. The depth information for each point is encoded as the overall size of the stripe. An image-point which reconstructs as deep within the hologram will have a broad stripe of interference with slightly-curved fringes, while a shallow point will have a tiny stripe and tightly-curved fringes. So a Rainbow hologram is very similar to a standard 2D photograph in structure, but with a variety of various sizes of swatches of interference fringes storing the depth info for each recorded point.
The above crude figure implies something interesting. Going from monochromatic to whitelight illumination spreads the diffracted image of the illuminator into a stripe of rainbow colors which will be seen within the horizontal "slot" of each fringe pattern, but this does not move the reconstructed patch of light horizontally. Horizontal position and stereo-3D effects are controlled only by the ORIENTATION of the fringes, and not by their spacing. Changes to the spatial frequency of the fringes will only affect the the rainbow-colored artifact and the vignetting. If the fringes were made square rather than sinusoid, and if the spacing was made very large, the interference pattern would then diffract the illuminating beam into closely-spaced multiple order beams. This would not alter the geometry of the reconstructed image, it would simply make the image appear white instead of rainbow, and would widen the angle from which it could be viewed.
In the limit as the interference fringe spacing is made >> than the illumination wavelength, the fringes begin to behave as individual reflective lines. Yet the hologram will still function. See what this is leading to?
The geometry of the Rainbow Hologram allows anyone to draw the fringe patterns by hand with a needle, and thereby to create holographic images without lasers and even without interference. This can be taken to ridiculous lengths: giant holograms composed of curved, polished metal rods become feasible.
It is not strictly necessary that the horizontal swatch of interference pattern be exactly duplicated in order to produce a hologram. When the fringes have been widely separated they stop interacting, so an individual "fringe" can be used. The pattern of nested hyperbolic lines can be replaced with a single reflective fiber or surface scratch. It need not even be hyperbolic, a circular scratch drawn with a compass makes a dandy "diffraction grating."
I've been drawing holograms of simple 3D objects by scratching a polished plastic plate by hand with a compass. The X,Y position of the scratches determines the X,Y position of the reconstructed points, and the radius of each scratch determines the perceived depth of the point.
So far I've drawn such things as polyhedra, starfields, text at various depths, opaque planes which hide text behind them, boxes with walls composed of random dots, etc. When lit with an extended source these "holograms" appear as sets of fine curved scratches, somewhat like several superposed LP record albums. When illuminated by a point source, each scratch produces a small "highlight," and the whole set of scratches produces a 3D object composed of bright points.
Date: Thu, 24 Aug 1995 12:53:52 +0500
Subject: Holography without interference ?
Hello Mr. Beaty,
It seems you have explored the power of the principle of holography what Gabor incidentally invented while working to increase the magnification in electron microscopy. I wish to share some facts about the subject of your interest.
In standard rainbow holography (Benton type), a slit is used "to reduce the information content of the hologram". And then one can expect a near fruitfull reconstruction even with white-light sources (of course at the expense of the vertical or horizontal parallax; that depends on how the slit is placed. But for getting a "rainbow" reconstruction from ordinary off-axis holograms, the slit (real or synthesized) is not must. For this case a Fresnel hologram of a transmitting objest (not diffused) can be used to demonstrate the principle.
If you are talking about "mechanically generated holograms", you may find some references in recent Applied Optics (in 1991/1992). It is basically the process of "writing" holograms on some plastic material on which it is easy to "scrible" (scratch) well defined (high resolution) fringes (i.e., hills and valleys). In my opinion, if the spatial frequency (I mean the carrier frequency) is low, still one can expect a holographic reconstruction. But, the reconstructed images will be nearer to the zero order undiffracted light (cross refer in-line Gabor holograms).
If you could briefly tell your story of resaerch, I can try to find the exact types of references you are searching for.
>Date: Thu, 24 Aug 1995 12:37:37 PDT
>From: William Beaty
>
>
>> Hallo William,
>> I found your Idea extremely interesting, I do'nt know anything
>> like this, maybe you could try to make a patent (you never know).
>> I am not able to help you, but I am interested in having more
>> details, if you want.
>> I would like to make my own 3d drawings one day.
>
>Hi! I've posted a description of my technique to info-holo.
>
>I believe that patents are more trouble than they are worth, unless one
>makes a really "earthshaking" discovery. And then one must go and start a
>business based upon the discovery, and unless the business does hundreds
>of thousands in sales, the cost of the patent legal fees will never be
>recovered. There is of course a small chance that some other business
>would buy a patent, but the "not invented here" syndrome makes this
>feasible only with large amounts of knocking on doors and salesmanship.
>I'd rather go by Harold Edgerton's philosophy to "have fun, and talk to
>everyone about everything you're doing."
>
>. . . . . . . . . . . . . . . . . . . . . uuuu / oo \ uuuu . . . . . . . . , . . . . . . . . . . . . . . . . . . . .
>William Beaty voice:206-781-xxxx bbs:206-789-xxxx cserv:71241,3623
>EE/Programmer/Science exhibit designer http://amasci.com/
>Seattle, WA 98117 billb,eskimo.com SCIENCE HOBBYIST web page
Date: Fri, 22 Sep 1995 06:57:05 -0700 (PDT)
Subject: Re: Drawing holograms by hand (fwd)
>
> In article <43isoh$rc3@news1.halcyon.com> you wrote:
> : In my SCIENCE DEMONSTRATIONS section I've recently added a file on how to
> : draw holograms by hand with a sharp tool. No lasers, no darkroom, real
>
> I've done a bit of holography on the side, so I might be a bit qualified
> to beg to differ, at least by asking: "How?" I can see that such an
> approach would provide a picture with stereo or dimensional
> capabilities. But I don't believe it would be possible to create a true
> hologram by hand with a sharp tool.
>
> I am curious about what you achieve.
I call the 'abrasion hologram' by the name 'hologram' because the overall geometry of the pattern of scratches is very similar to Benton rainbow holograms. Do you know what interference pattern is produced when a rainbow hologram is made of a tiny point? The pattern appears to the eye as a narrow horizontal streak. The interference fringes within this streak are curved, since the streak is a slice of a gabor zoneplate. If this streak of fringes were to be replaced with a reflective scratch in the shape of a portion of a circular arc having the SAME RADIUS as the curves of interference fringes in the real hologram, this scratch would create a point-image having the same position, depth, and horizontal parallax of the point-image in the real hologram.
Is this a hologram? Depends on how preceisely you define the word. If 'hologram' requires interference, then my 'abrasion hologram' is obviously not a hologram. But the mechanism by which the 'abrasion hologram' operates is very very close to that of rainbow holograms. And 'abrasion holograms' are like rainbow holograms in that they both require pointsource lighting, they both produce horizontal parallax but not vertical, the mechanism behind both is the reflection of light from oriented line segments, the reflective lines in both must be at the same angle and position, and both can produce pseudoscopic images if rotated 180.
My first 'scratch hologram' was the words 'science club' appearing as an image 12" deep within an acrylic sheet, and viewed in transmission mode in sunlight. Since then I've drawn images of large cubes that float below the surface of the plastic, a tetrahedron with one point extending out into the air, 3D starfields, a starfield with an opaque black square floating in the foreground, cylindrical and spherical surfaces made of glowing points, a square tunnel with stars deep inside, vertical planes with two different patterns drawn on opposite surfaces, and crude animations which 'play' when the plastic plate is tilted. I 'scratched' my wife a Valentine's day card with all the patterns and writing at various depths. Most anything done with rainbow holograms can be done with 'abrasion holograms.' Except the rainbow artifact of course.
Date: 20 Sep 1995 18:51:45 U
Subject: Made first hologram. Nifty!
I made my first "scratch-o-gram" today. Have you come up with a name for this technique (hopefully better than "scratch-o-gram" :)?
Luckily I happened to have a spare piece of black acrylic around. On my first try I made the scratches too deep; usually you want to either avoid scratching these sheets when you're working with them or groove them deeply to break them along the scratch.
You may or may not know that these sheets can be heat-formed at fairly low (kitchen oven) temperatures. Even better, they retain most of their surface texture (or lack thereof) after they've been heated, worked, and cooled. When I have the time I'll try warping a hologrammed sheet. Can you think of some 3D surfaces that would be aesthetically/mathematically interesting when combined with the scratch technique?
Have you tried different ways of making the scratches? Maybe I'll try these when I get the chance:
sandpaper cut-outs
hacksaw blade (drawn perpendicular to the blade)
pet flea-comb (metal kind)
spirograph
Thanks for posting this fun and innovative idea! Great website too.
Date: Sun, 03 Sep 95 06:48:35 0600
Subject: holograms
Hi there! Fascinated by Tesla, I stumbled across your very comprehensive and cool science pages. Totally cool. I'm impressed. Anyway, I read just a few of your many articles. One was your observation of holographic polishing mitts in black station wagons.
Well anyway, this reminded me of something I think I've seen but have been unable to confirm. Around the time Discover magazine was founded, my dad started subscribing to it. That was probably over ten years ago. An early feature of theirs showcased particularly novel inventions or discoveries, often made by accident.
I am pretty sure I recall reading about a 13-year old Dutch kid who had managed to make a holographic image in a way no one had thought of before. I think his dad worked with glass, perhaps as a maker of Christmas tree ornaments.
The kid used an open shoebox as a frame for his device. Across the top (and only in the middle portion of the box) he laid many rows of sticks. Hanging from each stick were many many strings. Each string was coated with tiny reflective spheres. That's obviously the toughest part, but the article mentioned that with glass making equipment this was a trivial step.
So, what he had at this point was a shoebox whose middle volume was full of glass beads. At one end which was left empty, he placed an object. I think a hole may have been cut in that end of the box and a bright light pointed through. Evidently a 3-D image of the object was plainly visible! I don't know whether the image was somehow suspended *within* the reflective spheres or on the other side.
As far as I can tell, this set-up produces a true interference hologram; the spheres provide both the interfering and reference signals (I am kind of confused by a lot of holographic theory, so I may be spewing falsehoods). I think the kid got a patent, and everyone "In The Know" acknowledged his novel discovery. Pretty cool, eh?
So, have you heard of this phenomenon or article? I'd love to find an archive of Discover but haven't been able to. I also haven't searched in six years.
Again, your page is wonderful...I'll be visiting it often and telling my friends about it.
ps. Oh yeah! My brother recently acquired a plasma sphere. He talked about wanting to set up a room in which the discharges surrounded the participants! I didn't understand how that could possibly work without killing everybody for lack of oxygen; also what would the discharges discharge to? Then I saw that your Seattle Weird Science Meeting actually describes or includes a glassless plasma sphere. We are from Illinois and lamentably won't be in Seattle anytime soon. What is this all about, or do I have it all wrong? I will certainly inform my brother that his idea may not be as far-fetched as I had thought!
Subject: "scrath" holograms
Date: Mon, 25 Sep 1995 13:00:57 -0500 (CDT)
Bill,
Just stumbled on your "scratch" hologram technique whilst chasing different links from Geek Site of the Day :)
I think what you've bumped into is more related to the techniques used to generate those 3D stereogram images that you see in gift shops and, well, pert near everywhere these days. Seems you're using the compass as a mechanical way to generate controlled spacings in the same way a computer is usually used to compute the separation map.
The newsgroup alt.3d carries discussion about these things and there's a fair amount of material available on the subject. I had an article in Dr. Dobbs Journal, a PC-ish programming magazine, back a while ago wherein I discussed the computer techniques for generating the images.
Nonetheless, I'm gonna stare at some car hoods after work tonite :)
Date: Mon, 25 Sep 1995 19:11:35 -0700 (PDT)
Subject: Re: "scrath" holograms
>
> I think what you've bumped into is more related to the techniques used
> to generate those 3D stereogram images that you see in gift shops and,
> well, pert near everywhere these days. Seems you're using the compass
> as a mechanical way to generate controlled spacings in the same way a
> computer is usually used to compute the separation map.
Hi Dennis! If you're describing the old lenticular postcards (or slitmask poster-sized 3D plates,) no, these scratch thingys are not similar. If by 'stereogram' you mean Rainbow holograms synthesized from multiple-lens camera photos, then yes, the hand-drawn holograms are very similar.
Are you familiar with the structure of the interference patterns in Rainbow holograms? The scratch-hologram pattern is similar in a couple of specific ways: XY position of centers of fringe curvature, and radius of fringe curvature. I think no one has realized that Benton's Rainbow hologram in being frequency-independent is also size-independent, and if the interference fringes in a Rainbow hologram are greatly enlarged and made square rather than sinusoid in density profile, the darn hologram still works! Rainbow holograms depend on the horizontal-slit/ converging-lens geometry in order to trade vertical parallax for frequency independance. The resulting interference pattern for each point is a horizontal swatch of curved fringes. Changing the spatial frequency of the fringes only alters the rainbow-colored artifact (and the vignetting) but does not affect the geometry of the perceived image. The upshot: replace the fine fringes with large crude reflective lines having the same curvature and position as the swatches of fringes in a Rainbow hologram, and this converts the spatial output into gazillions of close-spaced higher order diffractive beams, which still reconstruct the same 3D object and preserves the same horizontal parallax! Yes, visions of mile-wide scratch-holograms made of bent metal bars still dance in my brain.
> The newsgroup alt.3d carries discussion about these things and there's
> a fair amount of material available on the subject.
Yep, I posted the original article in alt.3d and in the SPIE info-holo listserve. Only a little response, which seemed to divide equally between people who tried the technique and were amazed, and those who didn't try it and were objecting to my labeling it "holography!"
> I had an article
> in Dr. Dobbs Journal, a PC-ish programming magazine, back a while ago
> wherein I discussed the computer techniques for generating the images.
Hmmm, did you do the article in Circuit Cellar Ink, where 300 dpi laserprinter binary hologram output was reduced to tiny patches on 35mm film, and simple objects like the letter 'A' were reconstructed? That one was pretty cool. Your name sounds familiar.
I've yet to explore any film-output versions of the scratch holograms. If an emulsion could be found which creates reflective lines when narrow lines are exposed on it, the scratch-hologram would work great, and should have vastly smaller resolution requirements than conventional computer-generated holography. Such an emulsion might not be necessary if instead the exposure was made in photoresist and the lines were etched into a polished surface. Another route I've yet to explore. A great step backwards for photo masks: resolution requirements more akin to that of an LP record, rather than that of a CD! ;)
Date: Sun, 3 Sep 1995 11:02:06 -0700 (PDT)
Subject: Re: holograms
Hi Carl! Glad you enjoyed my stuff. I keep thinking, if we all were able to look into everyone's filing cabinets, publication would become unecessary, and we probably would see a lot more interesting stuff that never gets published!
> The kid used an open shoebox as a frame for his device. Across the top
> (and only in the middle portion of the box) he laid many rows of sticks.
> Hanging from each stick were many many strings. Each string was coated
> with tiny reflective spheres. That's obviously the toughest part, but
> the article mentioned that with glass making equipment this was a
> trivial step.
Oh boy. I think I'm familiar with this effect, having happened across something very similar myself in 1985. If it really is the same, it does not involve holography, but instead is a matter of pinhole cameras and retroreflectors. Glass beads are retroreflectors, same as 'corner cube' mirrors and plastic car reflector prisms (which are actually arrays of tiny corner cubes.) When light hits any of these devices, the rays are sent back down the same path as the incoming rays. And if his device is the same, then it also requires a mirror somewhere in the box.
My device was a 4ft. square board covered with car reflectors. A small mirror was held a few feet away from this board, and oriented so it bounced the light from a well-lit object onto the board's surface. If the observer then looked over the edge of this mirror toward the retroreflector board, he/she would see a fully-3D image of the well-lit object floating down inside the surface of the board. By drawing ray-diagrams of the system I was able to see that the property of retroreflection, of returning rays back towards their source, would cause the eyes of the observer to see only the rays coming from the object from one viewpoint, as if the small mirror had been turned into a tiny pinhole. The other eye does the same thing, but from a different viewpoint. The retroreflector boards acts like a frosted screen, but a very strange one which sends two different image patterns to each of your eyes, and so creates 3D images.
So if the Dutch kid has a similar device, he went to a lot of unnecessary trouble. Instead of coating strings with beads, he could have bought some reflector tape, or at least poured his beads on a sticky surface in order to make a frosted retroreflector screen. Or he could have done as I did: buy a huge pile of yellow car reflectors from American Science Surplus, then mess around with them. I discovered the effect accidentally while playing with a mirror in the Exhibits dept. of the Museum of Science in Boston where I worked. My retroreflector panel was sitting nearby, and I suddenly saw a 3D veiw of the Boston skyline floating deep inside it. Pretty cool, eh? This was years ago, and I've never come up with any application for the effect. But if the kid has a patent, HE'S the one who has to do the work in figuring out a way to make money off it! :)
> ps. Oh yeah! My brother recently acquired a plasma sphere. He talked
> about wanting to set up a room in which the discharges surrounded the
> participants! I didn't understand how that could possibly work without
> killing everybody for lack of oxygen; also what would the discharges
> discharge to? Then I saw that your Seattle Weird Science Meeting
> actually describes or includes a glassless plasma sphere. We are from
> Illinois and lamentably won't be in Seattle anytime soon. What is this
> all about, or do I have it all wrong? I will certainly inform my
> brother that his idea may not be as far-fetched as I had thought!
I think there is an article from Ed Harris on my tesla coil page about this. The gas must be pure helium with a tiny trace of something else (like neon, nitrogen, etc.) If it was set up in a room, it would be hard to keep the gas nearly pure. But people could stay alive in the room using simple breathing masks, no pressure suits required. It might be easier to set up a big box with gloves sealed into holes in the box. Up until last month it was commonly assumed that plasma globes required a near-vacuum to operate. But during discussions on the tesla coil listserv, someone claimed that Radio Shack plasma globes used 1-atomsphere helium. Ed Harris went out and tried putting a balloon on his plasma globe supply. After flushing the balloon repeatedly with helium so only a tiny trace of air was left, the plasma globe worked!
Date: Sun, 8 Oct 1995 02:14:14 -0500
Subject: hand drawn holograms
I had a friend send me a reference to your www posting about the hand drawn holograms, and I was delighted with it and sent it on to some others. Unfortunately I don't have a piece of black plexiglass handy (I sometimes do) like my friend thought I might, so I haven't been able to try it yet.
I do have a laser printer, however, so I tried to simulate the technique on both white paper and transparency clear plastic. Since I know nothing about the critical issues about this type of holograms I didn't know if I were on an absurdly wild goose chase, or whether there was a possibility of it working (I thought maybe spacing the transparency away from a dark surface by a thickness or more might do the trick). I have some nice patterns, and they're fun to look at, but since I don't know exactly what I'm looking for or how pronounced the effect is I may or may not have success.
The other problem comes from looking at too many stereo images, and my eyes kind of fuzz over when I look at these kinds of things. A tyranosaurus didn't jump out, though.
Anyway, I thought if you had an opinion on whether there is the possibility of printing these holograms I'd sure like to hear it. Thanks for putting up the original info.
Date: Sun, 8 Oct 1995 09:58:33 -0700 (PDT)
Subject: Re: hand drawn holograms
> I had a friend send me a reference to your www posting about the hand drawn
> holograms, and I was delighted with it and sent it on to some others.
> Unfortunately I don't have a piece of black plexiglass handy (I sometimes
> do) like my friend thought I might, so I haven't been able to try it yet.
Hi Chuck! Black plexi is not required, the standard clear kind works fine. In fact, you can make a Transmission-type 'hologram' from clear plexiglas by viewing a distant pointsource of light through it after it's been scratched. The first 'hologram' I made was this type, but later I discovered that the Reflection-type 'hologram' was brighter. If you view it in reflection mode, it helps to have a black background behind the plate. This can be black paper, black paint, or the plate can be black plexiglas.
> I do have a laser printer, however, so I tried to simulate the technique on
> both white paper and transparency clear plastic.
Me too! I immediately tried this, but with no results. A printing technique can be tested using a single printed line. If you hold the sheet under a pointsource (clear lightbulb, the sun, etc.) and you see a small reflected highlight on the printed line, then that printing technique will probably work for holography. The little highlight will slide around as you move the sheet. I could see no highlight on laserprinting on transparancy. This hologram technique SHOULD work if the printed pattern is etched into a metal surface, or if an X-Y plotter is used to scribe a plastic sheet. It might even be possible to etch the pattern into a stamp, and then hammer it against plexiglas to make multiple copies. I haven't tried these yet.
> The other problem comes from looking at too many stereo images, and my eyes
> kind of fuzz over when I look at these kinds of things. A tyranosaurus
> didn't jump out, though.
The true test is whether there is any image at all. If you can see your encoded pattern (a little triangle? even a circular blotch?) in the scratch reflections, and if it shifts around as you move the plate, then your test has succeeded.
Any printing technique will require that the line be very smooth (no jaggies.) The reflected highlight must slide along smoothly as you move the scratched plate. If it jerks around, or if the highlight appears as a number of separate points, the hologram won't work well, if at all.
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