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ABRASION HOLOGRAMS
FREQUENTLY-ASKED QUESTIONS
(c)1996 William Beaty

----------------------------------------------------------   
These holograms aren't extremely hard to produce, 
so don't be put off by the massive amount of 
discussion below.  I'm just trying to cover all bases.
----------------------------------------------------------   
1. HOW DOES IT WORK? WHAT'S THE THEORY?

2. I DON'T UNDERSTAND HOW TO MAKE THEM.

3. I TRIED IT AND IT DIDN'T WORK!

4. HOW CAN I VIEW THESE HOLOGRAMS INDOORS?

5. WHY DOES THE PLASTIC HAVE TO BE BLACK?

6. CAN'T THESE HOLOGRAMS BE VIEWED IN "TRANSMISSION" MODE?

7. HOW DID YOU MAKE THAT CUBE IN 3D?

8. WHAT'S THE BEST PLASTIC?

9. THIS IS *NOT* HOLOGRAPHY!

10. ARE YOU INSANE?!

11. THIS IS A HOAX, RIGHT?


 












Q: I DON'T UNDERSTAND HOW TO MAKE THEM!

A: Follow the instructions on the top page, but also take a look at the following diagrams:

[Click to download GIF]
1. Make curved scratches as shown above

Your first hologram should be something very simple. How about the letter "V."

First draw the little "V" as a guide. Draw it near the bottom edge of your piece of plastic. Next, use the dividers to make lots of curved scratches above the "V". For each scratch, place the point on a different spot on the "V." Each scratch should be a quarter-arc or even a half-circle. Don't change the distance between the metal points. Make about twenty scratches. Even more is better.


[Click to download GIF]
2. Make LOTS more scratches on the plastic plate

Each scratch will create a single glowing dot in the finished hologram. That means you should make lots and lots of curved scratches. If you just make a few scratches, your hologram will look like a collection of sparks. If you make enough scratches (spaced closely like the grooves of a vinyl record album), the rows of sparks in the hologram will start to look like glowing white lines.

IMPORTANT NOTE: Each scratch must look dark and shiny. If they look white and dusty, then your hologram won't work. If the sharp point of the compass makes a squeeking noise, then that scratch is useless. Make your scratches slowly, so the compass point doesn't squeek.


[Click to download GIF]
3. Cut the little picture off the bottom of the plate

The scratches ARE the hologram. If you wish, you can cut your little "V" drawing off the bottom of the plastic plate. If people only see the plastic plate with "sandpaper marks", they won't know what the picture looks like until they see the actual holographic image.










Q: I TRIED IT AND IT DIDN'T WORK!"

A: If your hologram doesn't work, the problem could be from three main sources: the illumination, the viewing angle, or the hologram itself.

A) ILLUMINATION PROBLEMS

Holograms are sometimes hard to view, so at the start, USE SUNLIGHT OUTDOORS. The bright light will make your holographic image easy to recognize. If sunlight is lacking, then use an overhead street light outdoors at night. The dark background and the small bright light source gives good results. Once you know that your holograms are working and you can see them under sunlight, you can try bare lightbulbs indoors. Even flourescent tubes will work somewhat if you stand so the tube is lined up perpendicular to the hologram. But avoid light bulbs and flourescent tubes at the start, they make the hologram too hard to see.

When illuminating holograms indoors, avoid using a bulb in a fixture that has a white reflector, or one that is very close to the white ceiling. These will make the hologram image blurry. The ideal light source will look like an intense pinpoint having a black background. A small clear lightbulb hanging from a wire in a darkened room is best. If your only lamp has some sort of reflector, you might consider painting the reflector black. A frosted bulb will work OK if it is about 5 ft or more from your hologram. A transparent light bulb is preferred. Halogen pin-spots (used in track lighting) work very well.

These holograms work best when the reflected background is dark, so try shading the windows and turning off all room lights except the one used for illumination, or try viewing them at night. This isn't a requirement. However, a dark environment makes the holograms appear to be VERY bright.

B) PROBLEMS WITH VIEWING ANGLE
Stand so you are facing the light source, or with the light source directly overhead. (If the light source is behind you, your hologram will only operate over a very small range of viewing angles, and the correct angle might be hard to find.)

Hold the hologram so the scratches are humped upwards in the center. If you hold it so the scratches are bowl-shaped (humped downwards) then the image will be upside down, and the depth will be inside-out!

While looking at the scratches, tilt the top edge of the hologram slowly farther away from you and slowly back again until you start seeing bright highlights in the scratches. Try tilting the hologram until you see the reflection of the light source in the plastic surface, then tilt it back again so the light source image appears to move up a few inches above the scratches. You should see a collection of highlights in the scratches. These highlights ARE the holographic image.

If you still cannot produce a hologram, then as a last resort, try drawing a single circular scratch on plastic like so:

                 ___----___
               /            \
             /                \
            |                  |
           |          .         |
           |                    |
            |                  |
             \                /
               \            /
                 ---____---
Hold this scratch in the sun, and you should see two little highlight reflections which move around along the scratch. The highlights will be on opposite sides of the circle, like so:
                 ___----___
               /            \    little highlight reflections.
             /               (O)
            |                  |
           |          .         |
           |                    |
            |                  |
            (O)               /
               \            /
                 ---____---

These little reflections ARE THE HOLOGRAMS. They are holograms of a single dot. When you make a complete hologram plate, every single scratch should have a little highlight when you hold the plastic plate in the sun. The little dots of highlight-reflections form the hologram (of the letter V, for example.)

If you don't see these little moving reflections, then there is something wrong with the scratch. You may have pressed too hard with the compass point, or swept the point along too fast and produced a white scratch with a shredded internal surface. Or your compass may be too wobbly, since the scratched line must be very straight and smooth. If it has little wiggles, it won't produce holographic images.

C) FAULTY HOLOGRAM
Use a sturdy, expensive compass. I tried the $2 kind, and it didn't work. It wobbled and changed spacing. A drafting compass from an art supply store works best. Expect to pay between $10 and $15. It must have a screw adjustment which sets the spacing between the points. It must have an extra metal point which can be put in place of the pencil lead in order to change the compass into "dividers." When set to a particular spacing, you should feel no "play" or wiggling if you try to move the compass arms together and apart. [WARNING! Always verify that the second metal point can actually be clamped in place of the pencil! I've encountered compasses where the supplied metal point was the wrong size and could not be used. ]

Draw one object, and LOTS of circular scratches, from lots of points on your object. For example, if you were to only draw scratches from the tips of the letter "V", your hologram would appear as three glowing dots, and would be very hard to see. Instead, draw the scratches with your compass placed upon at least nine different places spread across the "V." The more scratches, the more dots will be in the final hologram.

Use a sturdy plastic plate, like a piece of Plexiglas 1/16in thick or thicker. I found that polycarbonate "Lexan" works a little better than acrylic because the plastic is softer. Someone recently had good success using the clear plate that came with a small picture frame. The clear styrene front of CD boxes works well (and some have a black back, which gives good contrast. For your first hologram try to get some acrylic or polycarbonate (Plexiglas or Lexan.) Try other materials later, once you succeed in producing holograms.

DRAW YOUR CIRCULAR SCRATCHES VERY LIGHTLY to start. Once you have succeeded in producing good holograms, you can try drawing deeper scratches. Deeper circular scratches produce a brighter hologram. But if they are a bit too deep, the surfaces inside the scratch will be shreeded and rough, and the hologram won't work. The scratch MUST be black and shiny inside.

DULL COMPASS POINTS WORK BETTER. If you compass is new and unused with extremely sharp points, then you MUST push down very lightly when making scratches. If you push down too hard, the sharp point will create a groove with a flat-sided cross section, or will tear up the plastic into shreds. Instead your goal is to make scratches which have a rounded-bottom cross section. Try dulling the sharp points on 300 or 600 sandpaper. Also, I found that sewing machine needles work well (they have an intentionally rounded tip.) Even small nails sometimes work well. If your compass needle is too sharp, then shallow scratches will work, but deep ones won't.

AVOID MAKING WHITE, DUSTY SCRATCHES, as these will not reflect light and will not produce hologram dots. If you sweep the compass point too fast, or if you push it down too hard, it may chatter and produce a dusty, non-functioning scratch. If you make a couple white scratches by accident, don't sweat it. If *most* of the circular scratches are white, then start over.

Avoid squeaks! If the compass needle makes a squeaking or hissing sound as you scribe each scratch, then that scratch won't reflect light right. Each scratch must be smooth inside like a mirror. Scribe your scratches SLOOOOWLY to avoid squeaks. Rub a very tiny bit of oil on your plastic plate, it helps.

                            /          /
             Tilted       /          /
             compass    /          /
             point    /          /       (Side View)
                     --__      /
                      /  /--_/
                     / /
                    //   ---) Direction of Motion --)
      _____________/______________________
     |                plastic plate       |
     |____________________________________|
Try holding the compass tilted, so the point trails across the plastic and doesn't dig in and bounce.

Start with a very simple image, like a "V" or "I" or "X" Once you get this working well, you can scratch your initials, etc. If you start out with something complicated, you may do a lot of work yet have your first attempt fail. It's better to do your trial-and- error with quick and simple images.

It's easier to see holograms having shallow virtual depth, so set your compass to about 1 or 2 inch spacing between the points. The first scratch-hologram I ever made was at *fourteen* inches depth! It was *very* hard to see, and fortunately I knew exactly how to illuminate and view it, or I never would have seen the image.

Compass point too sharp? The scratches function as reflectors having curved cross-sections, so if your compass doesn't make polished scratches with curved bottoms, your hologram won't work. If your compass point is extremely sharp, then sweep it with low pressure, otherwise it will create a deep v-shaped scratch which won't reflect light properly. To make a bright hologram, use a less sharp compass point with heavier pressure when making the scratch.


Q: WHAT IS THE THEORY BEHIND THIS?

A:

See my SPIE Paper for details

The brief explanation: curved scratches reflect light as if they were thin, bent, silvery rods. When you view them in the sun, each scratch will both focus and also spread the sunlight (each scratch can produce a "virtual image" or a "real image" of the sun.) You can assemble a three-D shape from these little dots of sunlight.

Another explanation: each scratch acts as a bent mirror and reflects sunlight. Each reflection looks like a small white highlight on the shiny scratch. Each of your eyes sees a DIFFERENT REFLECTION. Your brain thinks the two different reflections are really one white dot located deep behind the scratch. It's like a "viewmaster" stereo viewer!

When you draw lots of scratches, each of your eyes sees a different pattern of dots, with one white dot per scratch. Because your two eyes see different patterns, your brain can mix the two images together and make a 3D structure in your mind. The two images are called a "stereo pair."

For each scratch, the more curved the scratch, the closer the two dots appear to be. When they are close together, your brain thinks the one white dot is closer to the plastic surface (it has shallower depth.) If the scratch is broad and sweeping, then the two dots will appear far apart, and your brain will think the one white dot is very deep behind the plastic.

Here's a less-brief explanation: holbrief.html
Here's a paper I presented at a conference: DRAWING HOLOGRAMS BY HAND at SPIE Electronic Imaging 2003

The full explanation is contained in this research paper:

W. Plummer & L. Gardner, Applied Optics, V.31 No.31, Nov. 1992, pp. 6585-6588, "A mechanically generated hologram?"
More info is here: IS IT REALLY HOLOGRAPHIC?

Info about Benton's Whitelight/Rainbow holograms is in this paper:

F. S. Yu, A. Tal, H. Chen, Optical Engineering, Vol.19 No.5, pp. 666-678, "One-step rainbow holography: recent development and application."

Q: WHY IS IT REQUIRED THAT THE PLASTIC BE BLACK?

A:

The plastic itself needn't be black, since the intent is just to provide a dark background. These holograms can be viewed either in "transmission" mode by viewing a distant light source through clear plastic, or "reflection" mode by viewing an overhead source bounced off of opaque plastic. I found that the "reflection" mode gives a much brighter hologram, and using opaque black plastic improves the contrast. If you use clear plastic, you can place the hologram on a dark tabletop with a light source above, or hold some dark paper behind the plastic, or paint the back of the clear plastic with black paint. These are improvements, not requirements.

Q: HOW DID YOU DRAW THAT CUBE IN TRUE 3D?

A:

> I'd just like to know what's going on with your '3D' cube hologram.
> According to my understanding, if I follow the instructions in your
> article I will generate a flat 2D image of a 2D original, but which
> appears to float above or below the surface as determined by the
> divider spacing. So how did you generate an apparently 3D image on one
> plate?? 
My very first 3D object was a big nasty job because I changed the spacing of the compass in order to change the depth of every single point. Every single point required a different radius. It took me hours.

But then I found a trick that makes it easy to draw straight lines in depth (where a straight line can dive inwards in 3D.) You really only have to figure out the endpoints; you have to carefully position the glowing white dots at the desired ends of the straight line. For all the points in between, just draw midpoints! Just place the compass so its fulcrum point is exactly half way between the previous endpoint fulcrum-point holes in the plastic, then adjust the compass radius until you can place a new scratch *exactly* btween the scratches of the two endpoints you've already drawn. This creates a glowing dot which is half way between two other dots. It's half way in 3D, and the two other dots can have different depths. Then do it all again: choose two adjacent dots and lay another midpoint between them. Keep putting new dots between existing dots until you've filled in the straight line.

So for the 3D cube, figure out the compass spacing only for the seven visible corner points of the cube, and draw these seven scratches. Verify in sunlight that you've made seven glowing dots which look like the corner-points of a 3D cube. Then place one compass point on the halfway spot between two existing fulcrum marks that created each of the corners, and lay a new scratch exactly half way between those two existing endpoint scratches. (you need to change the compass spacing to do this.) Repeat this for nine cube edges, nine halfway marks total. Then place the compass points on the spots half way between THOSE, and draw the new scratches (18 total). Keep repeating, dividing each line of the cube into 1/4, 1/8, 1/16, 1/32, etc., and where each curved scratch gets laid down halfway between two other scratches drawn previously. I found that I could do this freehand; adding more and more scratches between the ones that were already there. I stopped when the scratches were less than 1/16 inch apart, which made nice solid glowing lines when viewed close up. For larger holograms viewed from a few feet away, the scratches don't have to pack so densely.

Now for a REAL trick, figure out how to draw an opaque square. Not just a glowing square, but a square that hides background objects. Hide your initials behind it so that you have to tilt your head to look AROUND the square and see the initials behind it. The secret is to draw incomplete scratches when drawing the background objects, so that different parts of the background image go dark at a particular viewing angle.


Q: CAN'T THESE HOLOGRAMS BE VIEWED IN "TRANSMISSION" MODE?

A:

Yes! If you use clear plastic, try viewing your hologram using a single small light bulb in a dark room. Hold your hologram in front of your face, about 1ft from your eyes, and hold it so you look *through* the plastic at the distant light bulb. While observing the patch of scratches, move the plastic down so that the distant bulb seems to be a couple inches above the scratches from your point of view. You should see the highlight-dots light up and form a hologram in the pattern of scratches.

HINT: if the background near the light bulb is brightly lit, you may have trouble seeing the hologram. Try turning all lights off except the single clear bulb. Try suspending the bulb away from any light-colored wall or lampshade.





Q: HOW CAN I VIEW THESE HOLOGRAMS INDOORS?

A:

- You can't!! Well, it's nearly impossible to see the image unless the room is dark, and unless you use just the right light source. If your hologram doesn't seem to work, you'd better view it outdoors in the sunlight. ALWAYS view your first hologram in sunlight. That, or use a slide projector or overhead projector (or a video projector displaying a bright white field.) You can even use a streetlight outdoors at night. Once the angles of light are correct and you can "find" the image, then later you can try using a single distant light bulb indoors.

- The best light source should act like the sun. It should appear small, but be intensely bright like a 300-watt spotlight. A bright flashlight might work if it's held many feet away. Tracklights which use hundred-watt (or more) halogen spotlights are ideal. A clear light bulb can work, but the light is usually too dim. If the light source is too close to the hologram, it will make the image blurry and distorted.

- Flourecent fixtures give VERY blurry hologram images. However, if you happen to be standing under a fixture that has no diffusing plastic plate in front of it, and which has one tube or two closely- spaced tubes, then you can use it to view a very blurry hologram. Stand under the flourescent tube so the tube is perpendicular to the line between your shoulders, so the tube is in a line going forward and back. Hold the hologram in front of you and tilt it up and down until you see a blurry blotch. Tilt the top edge toward you until the hologram almost goes dark, and it will get somewhat clearer.



Q: WHAT'S THE BEST PLASTIC?

A:

- Of the types of plastic I've tried, styrene and polycarbonate seem to work best, but acrylic is the most easy to find. Polycarbonate is "Lexan(tm)" or "Tuffak(tm)", the bulletproof plastic. Acrylic is "Plexiglas(tm) or Lucite(tm), perspex and others. Acrylic can be found at glass shops and large hardware stores. Styrene is commonly found on the "jewel box" cases of music and computer CDs, the plastic covers of framed photos, etc. Softer plastic works a bit better, and tends not to make the "crunchy white" scratches that sometimes happen with acrylic. Slightly greasy plastic is best.

Glass won't work unless you can somehow make a scratch which is smooth and polished. You'd probably have to etch the scratched glass with hydroflouric acid (nasty stuff.) However, you could experiment with different types of diamond scribing tools with glass. I've never tried it.




Q: THIS ISN'T A HOLOGRAM! IT DOESN'T USE COHERENT OPTICS!

A:

Oh yeah? See Why I Call It 'Holography'. The short answer is: if these are not holograms, then neither are Benton Rainbow Holograms. Abrasion holograms employ the same optics as the holograms found on credit cards. Mine just have larger spaces between the zoneplate fringes. All white-light holograms require size-independent zoneplates in order to reconstruct sharp images using broad-spectrum light.



Q: ARE YOU INSANE? YOU SHOULD KEEP THIS SECRET AND SELL IT!

A:

see http:// amasci.com/freenrg/secret.txt for my thoughts on this.



THIS IS A HOAX, RIGHT?

A:

- I received several messages saying things like "I thought it was a hoax, but I tried it and it worked!" Huh. It never occurred to me that people would think it was a hoax. Unfortunately it is impossible to convince a "disbeliever" of anything. Anything I could say would just be part of the hoax, right? They'll have to try it themselves. This behavior is called Pathological Skepticism, and is covered on my page about Closeminded Scientists.

For the slightly-skeptical, I call your attention to the stereo pair GIF on the main holo1.html page. It shows a scratched-plastic hologram along with the glowing 3-dimensional image within its surface. An ambitious skeptic can look up this research paper:

W. Plummer & L. Gardner, Applied Optics, V.31 No.31, Nov. 1992, pp. 6585-6588,A mechanically generated hologram?,

I wasn't the first one to notice the phenomena. I'm just the first to develop the circular-scratch technique into a method for creating fully detailed hologram images.

 

 




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