The red and green are OK. The blue/purple may be too low.
In order to record and reconstruct colour holograms, you need to familiarise yourself with the CIE colour chart (below).
- CIE 1931.jpg (45.5 KiB) Viewed 3099 times
Notice that the figure has a set of colours around the perimeter. All the colours that will reconstruct can be determined by a triangle connecting the three laser wavelengths you intend to use. That is, all the colours within the triangle will be recorded and can be reconstructed (all these colours are called the "gamut" of the hologram, by the way). You'll notice that if you draw a triangle connecting 405 (extreme lower left corner) to 650 (pretty much extreme right corner) to 532 (almost to the top of the diagram), you'll miss most of the greens. Also, 405 is barely visible (I can't see it!). The human eye sees comfortably between 450 and 680, after that, the colours get very dim.
There is much argument about the "ideal gamut" for colour holography, but I prefer either 488 or 457 for the blue. You'll notice that the 488 pretty much misses out the deep blues and purples. But, my arguemnt for using 488 is that natural colours rarely include such deep colours. At any rate, with the help of the CIE chart, you'll be able to determine the best gamut for your object.
I think 5 mW may be on the low side. By the time the beams hits the plate and the object, you'll have precious little light left, and the exposures will be long. The bane of holographers is motion, any motion of less than the width of a human hair will destroy the hologram. The longer the exposure, the more prone to motion.
