object viewer for 2-color holograms

[Joe Farina]

To preview objects for 532/633nm holograms, I put this together using a 5mw HeNe and a green pointer. It would work well, except that the pointer has large power fluctuations over time. The parts weren't too expensive, I got the dichroic mirror and light guide off eBay, they were about $20 each. It's interesting to see the color effects when objects are illumated with these two wavelengths.

[DJ Mathson]

Nice setup. Another option could be to use a red diode, a 445 nm diode and a green dpss to get full color illumination, though it may be difficult to get an even illumination. Does the light guide even out the distribution?

[Joe Farina]

Does the light guide even out the distribution?

It doesn't seem to even it out too much, the beams need to be fairly well aligned to get an even yellow pattern. I guess these light guides are made of many individual fibers.

[BobH]

You might try a very light diffuser on the output end of the lightguide to make the beam more uniform where you use it. Also, try focusing the beams into the lightguide. They don't really work well as with collimated beams on the input, and it will give you more control over uniformity.

[Joe Farina]

Thanks for the tips, Bob. As long as the two beams are centered in the middle to the light guide, the output is quite even. But it's quite speckly, and a light diffuser helps with that, if it's held slightly beyond the end of the light guide.

[BobH]

Another thing to try is a spinning light diffuser imaged onto the input side of the lightguide. That'll despeckle and better match the input NA.

[Colin Kaminski]

Another thing to try is a spinning light diffuser imaged onto the input side of the lightguide. That'll despeckle and better match the input NA.

I had not heard of this. Thank you! I had heard of vibrating diffusers but spinning is a way better idea.