Laser Pointer Holograms

kgb1001001 writes: "A couple of instructors at Lake Forest College and the Kyoto Institute of Technology have put together a nice little page on amateur holography using laser pointer diodes. This home-page gives enough information to get started and also includes an order form for the photographic plates and chemicals needed to develop the holograms. Also, another page discusses the same techniques and materiels, but comes with some nifty pictures (2-d of course) of the final outcome."

Comments

Too expensive

[BillyGoatThree]

Laser pointers? Film? Chemicals? BAH!

Draw them by hand using a compass and plexiglass.

Did this project last month with my brother

[flxkid]

It was really quite interesting to setup. The ones we made turned out so-so. The problem was the only room that we had to create the holograms in was on the 2nd floor of the house. So all kinds of vibrations from below caused some problems.

If ur going 2 do this urself, I'd advise setting up the project in a school's darkroom or janitor's closet with a cement floor.

Make sure ur far away from streets and all forms of noise (and therefore vibrations) as this REALLY causes problems.

FLXkid (the Visual Dataflex Guru)
...
Better VDF than VD!

Re:Counterfeits

[checkitout]

The type of holographic labels companies use are completely different from what is being described here.

The process being discussed uses glass plates, chemical developer and is monochromatic. The type of holography you're refering to uses micro embossed metal to produce an image.

I dont think they have anything to worry about. :)

Anyway, we did this for a science class in college, and it was a lot of fun even though the image of my pocket watch came out kinda dim. You need an object with a really reflective surface to get something sharp looking, plus a steady hand and a room with solid floor. There's a lot of variables to account for and a lot of people simply ended up with a glass plates with some cool looking lines on it.

Been there, done that, works great.

[FTL]

A couple of days ago I just finished creating my first set of holograms based on their techniques. And I have to say that it was a lot of fun and turned out quite well. If you've never tried creating holograms, give it a shot. It takes a bit of time, but it is well worth it.

The only catch is that these holograms are only visible at a very narrow range of angles. Not just the two angles of rotation to your eye, but also the two angles of rotation to the point light source. So it can take a bit of fiddling before you suddenly see something. But when you do, it's very sharp and detailed.

Re:Pointer? Pointless!

[hyrdra]

I'd like to make a few comments on your post as one who has been in this field for over five years.

First, TEM00 has very little to do with coherence properties. It's a type of resonant mode and has more to do with polarization than anything else. A TEM00 laser is not required to make holograms, nor is a polarized laser. In fact, ruby lasers which are not TEM00 and Argons who often mode jump left and right are used very often for holography.HeNe's are naturally coherent due to the spectral output characteristics of Neon, which doesn't change wavelength very well based on temperature or power flux. Diodes, on the other hand, have rated shift in wavelength with temperature and/or power. However, newer power supplies automatically sense changes via a feedback loop photodiode and adjust power characteristics accordingly. A good diode with a digital PSU will give you 12+ feet in workable coherence. Add a themoelectric cooler to stabilize the temperature and you can increase it even more. That being said, I doubt anyone has any use with 12 feet of coherence or more. A polarized HeNe from the manufacture Coherent, for example, has several 100's of yards coherence. But who needs that much, seriously? For doing simple objects, a few feet is plenty.

Remember, the goal is trying to record the interference patterns of two (or more) beams on a film plate. Light only interferes well with like-wavelengths, so when your diode shifts in the middle of a 40 second exposure, it will degrade the pattern and thus the diffraction efficiency (if a transmission hologram) of the hologram, and thus the brightness -- the rest of the light is loss to scattering. However, with a 50 mW diode you can easily have sub-second exposure times with a 3x4" plate, which should produce a hologram with equal quality as one produced by a HeNe.

A good test to find out the coherence length of your diode is the classical Michelson Interferometer. It produces controllable interference via a path length delta in one of the optical arms. As long as you can obtain an interference pattern at delta, that is your coherence length. I tested a 5 mW diode from Radio Shack and got around 3 feet of coherence.

There are many advantages to using laser diodes for holography over the conventional HeNe. First, they're cheap -- much more so in the price/power ratio than a new or surplus HeNe. You can get a complete 50 mW 650 nm laser diode system for around $500. That's plenty of power for doing 8x10's with exposure times in the seconds. Diodes are also small and do not involve high voltages associated with the gas discharge tube-type supplies HeNe's employ. Even a used 20 mW HeNe on eBay (which is very rare) will run you about $700 to over $1k. A new one could cost several thousand. Better to get a multiline argon and do color ~

I should also point out that you can obtain very high power diodes at around 670 nm -- these diodes produce 1W or more of power and cost only a few hundred. The beam requires a fair amount of conditioning because the emitter is rectangular and thus emmits a beam high in divergence, but an anamorphic prism pair will give you a nice round beam with 1.2 mRad of divergence for miles.

Another thing to think about it that the HeNe, as a technology, has been around since the late 1960's. It's old and there is no more R&D going on with gas lasers. Diodes, on the other hand, continue to be a very hot materials and science research area. Diodes are getting more stable, smaller, more efficient, and the wavelengths keep going doing (Nichia makes 400 nm diodes now). You can also purchase a diode pumped solid state (DPSS) system to frequency double an IR diode to create useable green output. HeNe's see no more devlopment in these areas and are being replaced by diodes. This actually decreases demand and thus increases price...do the math!!

Anyway, hope this helps someone. I have been using a TE cooled 500 mW Philips diode with digital PSU built from a PIC, with dual anamorphic filtering. With this setup I am able to create very bright holograms with several feet coherence length...

At long last -- yes, it is true you can make holograms with a laser pointer!