School of Holography
LASER POINTER / SEMICONDUCTOR LASER HOLOGRAPHY
by Frank DeFreitas Holography Studio
Creative Holography Using
My magical journey of making
Inexpensive Laser Pointers
holograms with a $7.99 laser pointer
and inexpensive laser diodes.
Success with AC/DC Power Supply 1/23/99
(NOTE: Holograms are not 3-dimensional on your computer monitor).
The above photos show a successful hologram (of ocean coral) using an AC/DC power supply connected to the laser pointer. All previous holograms were made with the laser pointer running off of batteries (3, 1.5volt AA's). I wanted to slip in this test to find out once and for all that an "inexpensive" power supply would work. I thought that perhaps it would change the function of the diode so much, that it would not be possible to do a hologram with it. The detail in this hologram is breath-taking. It's a shame it cannot be seen in the digital photo.
WARNING: Diodes are very sensitive to the slightest changes in current/voltage. You can burn a diode out instantly if not careful (and even if you ARE careful). Hook your diode up to a power supply at your own risk. You must also make sure your polarity is correct before applying power -- as many diodes are not polarity protected (fortunately, this model is).
This power supply was $10. Add that to the $7.99 cost of the laser pointer and you've got a laser source, running without the cost of replacing batteries, for under $20 -- that is capable of making holograms up to 8 x 10-inches with very impressive depth. One thing I noticed is that the pointer is putting out more energy using the AC/DC converter. Running it at 3volts gave the same reading as 4.5volts with the batteries. The pointer was very bright at 4.5volts from the power supply. Readings from the Science and Mechanics light meter were as follows:
All readings were on the 2 scale:
3volts, 100mA = 15 reading (same as 4.5volts with batteries)
3volts, 300mA = 19/20 reading
4.5volts, 100mA = 19/20 reading
4.5volts, 300mA = 24/25 reading
Not being an expert in electronics, I was always under the impression that an electronic device would only use the amperage that it needed. And as long as you supplied the needed current (or above) you were fine. The lowest setting that I have for amperage is 100mA, which is certainly above what is needed, but I did not expect it to have any effect. I thought only increasing the voltage would increase the power output. So, I was surprised to see the jump in energy at the increased current. The output at 4.5volts, 300mA was indeed very bright, and the exposure dropped from 18 seconds using batteries to 12 seconds with the power supply for the BB-Plates.
The areas close to the emulsion are very bright, however there is quite a noticeable drop-off in brightness as depth increases. It's possible that the power supply operating at 4.5volts has changed the coherence length of the diode. The other 8 x 10-shot of the coral (shot with batteries) showed no diminished brightness all the way back to 8 inches into the hologram (see page 5).
I mentioned that the light intensity reading at 3volts from the power supply was the same as 4.5volts from the batteries. It may be necessary to drop the setting on the power supply to match this -- eliminating the boost in power, but allowing operation without purchasing batteries. A little bit of a trade-off, but not really loosing anything. The 4.5volt setting from the power supply is probably overdriving the diode too much. I think the 3volt setting will do the trick.
The above photo shows the power supply. It is a Rectocon AC/DC converter with several settings for both amperage and voltage. It is usually used to power portable Walkmans and radios, etc. Now it powers a laser diode.
I just received a box of Slavich plates from 4th Dimensional Holographics (see link page). It will be interesting to see how Slavich works out. I'm expecting nice results and I'm hoping that my PyroChrome processing will be sufficient. They are 2.5 x 2.5-inch plates, so I'll have to build another plateholder or find some way to hold them for the tests. Check back for results. I'll probably shoot one over the weekend. If not, then early next week.
Note: If you decide to do your own laser pointer holography, please remember those companies that have contributed to these tests with materials when you make your purchasing decision.
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Frank DeFreitas Holography