Frank and Steve suggested it in the HoloTalk last week: Using one pointer for the reference beam and another pointer for the object beam. This shouldn't work. I gave it a try anyway. My first try gave a hologram and much personal excitement. Analysis of my setup showed that the hologram was produced by stray light from my "object pointer". Another hologram was tried eliminating the stray light - nothing was there, no image at all. This was a kick in the head with a steel boot! So-- anyone else want to give 2 pointer holograms a try? No try, no sigh. I don't want to hear any theoretical reasons why it won't work, I'll just come back at you with theoretical and heuristic reasons why it should work. The only responses I care to see are from those who actually try it.
Paolo Zorat - Tue, Mar 30, 99 02:11:58 AM
Frank - Sat, Apr 10, 99 10:40:52 AM
Frequency stabilization is key here. It could begin by having both diodes (or pointers) share the same power source which is divided up in it's feed. Adding to that, a shared driver board as well to the raw diodes.
However, the above may only serve to get us into the ball park. Due to manufacturing, I would assume that no two diodes will produce the exact same wavelength even with matching current and drive.
So this may add another requirement to the equation -- which would be to monitor wavelength output and make individual adjustments. Sort of like a fringe-locker, but with wavelength instead of fringe locking. This could be accomplished in a number of ways. Feedback to a variable resistor to micro-adjust current to a specific diode or changing the temperature to a specific diode. Both of these methods would cause the specific diode to adjust it's frequency.
Of course, it's rather easy to supply each diode with the same feed . . . even the same driver board. Monitoring the wavelength and making adjustments to keep the two in sync is another matter altogether. Especially if things are to be kept "inexpensive".
It's certainly possible -- and at some point it's going to be done. 207.16.159.179
Paul Kline - Tue, Apr 20, 99 01:53:54 PM
Steve Michael - Wed, Jun 16, 99 08:32:58 PM
Arturo Perez - Fri, Aug 27, 99 08:21:05 AM
Charles Freeman - Sat, Nov 20, 99 11:31:02 AM
KRANKY - Tue, Nov 23, 99 05:33:49 PM
Steve Michael - Wed, Nov 24, 99 08:41:56 PM
Ray - Tue, Jan 25, 00 12:45:15 AM
Since diode arrays are used in optical computing for read/write functions of data storage there must be a way to get two diodes in sync where one could be used for the reference and the other for the object beam.
It would be easier to test using an Interferometer setup. If the fringe pattern is stable then they will produce a hologram, if they creep then no hologram! A hologram is just a frozen interference pattern.
207.28.190.119
I've already discussed all of this with Frank and I've made over 10 holograms testing this. I wasn't successful in producing a single hologram. I even tried 3 Infiniter 200s and, of course, it didn't work. I used the same lasers and different lasers. I ran test with the same lasers connected to the same power supply and individual power supplies. Nada!!! This final confirms the same results I got from my interferometer testing where I NEVER got any fringe patterns. I even made sure the path lengths were equal!!!!! A lot of hours, film, chemistry, and frustration. I may or may not have put this to rest. 209.122.205.93
Ummm. Form a Physicist point of view... in principle, using two different light sources can't work... the sources are not coherent at any rate,
so the interference pattern you get on the plate is pure white noise. 192.112.247.7
The reference and object beams have to be of exactly the same wavelength for teh correct wavefront to be recorded on the film! Using two lasers will record an interference patern or the film all right, but there will be a random wave front, therefore no picture. No amount of arguing or anything else will excuse this fact! 146.230.128.29
I tried the holography for the first time and it was great. It amazed me how easy my first project was.
I know they get more complicated and more complex as the project gets bigger and more complex.
If you have any ideas of projects that you wouldn't mind sharing e-mail me in AOL under KEcollege. 165.199.3.53
Very enlighting information Charles. So I guess if I buy 2 $800 5mW He-Ne lasers from Aerotech, for example, and they specify 638 nm output, I can't expect exact wavelength output? If that's the case, it would seem there is some delta lambda bandwidth or variance going on and the output wavelengths between the two lasers are not exactly the same. Any thoughts? 216.164.130.83
This Question is especially for Mr. Michaels, but also for everyone else. What if you modulated both beams, like radio waves? 63.208.236.6