Holographyforum.org / holowiki.org

This is a test DCG hologram done yesterday. The object on the left is a piece of marble painted with squares of different colors. The DCG film is the usual kind, but the pH was raised to 6.35. Two wavelengths were used, 488 and 532. The colors were combinations of blue, green, yellow, and white. Although desaturated in this hologram, the colors came through to a reasonable extent. Power levels for the exposure were 120mJ for blue, and 600mJ for green. Lab temp and humidity were 61F and 53%. There was some damage to the gelatin due to the 1/16 inch polycarbonate sheet which I was using as a cover plate during processing to reduce blotches (which definitely works.) The sharp edges of the plastic dug into the gelatin, due to my carelessness.

In recent holograms, I've switched to using a concave mirror for beam expansion rather than a spatial filter. So far, I haven't been able to detect any difference in the final hologram. As long as the mirror is new, and kept clean, it works very well. Of course, if the spread beam is examined on a white screen, there are irregularities, but they aren't severe. For display holograms of objects, it seems that those irregularities aren't noticeable at all. Using this mirror has made my life much, much easier I'm using a mirror with a 4.5mm focal length from Edmund, which is comparable to a 60X objective. They have many other types available at a reasonable cost:

https://www.edmundoptics.com/f/concave- ... ors/12242/