I´m using the less powerfull diode from Integraf. Its my first time...and as the films are quite expensive ( i´m a student ), I want to try and not ruine any of them. So I´m making considerations about the dimesions of the scene...for making reflection holograms...how deep can the scene be?
For white light viewing of small reflection holos, the practical depth limit is no more than a few inches before objects become too badly blurred unless special techniques are used. (see the Kubota deep-image hologram post from a week or two ago) If the holo is instead lit by a spread laser beam, and its color has not shifted too much due to emulsion shrinkage, the image is sharp throughout its depth.
Does anybody have experience with this or a similar method to
achieve high image depth ? Now that I can record transmission
masters with great depth (the only issue is sufficient illumination),
I'd like to make reflection copies with as large perceived depth
as possible.
I did some preliminary testing and found that lighting with an
ultrabright LED looks very promising for play-back, as their beam is relatively
well collimated and monochromatic (the green or aqua-green ones
are at ca 525 resp 505nm. which are close enough to the 514nm line,
and give pretty high-contrast images).
One method I've used is mirrors. If the bulb is not diffused, you can use mirrors to create a fairly compact viewing system and still have the bulb apparently be a long way off and so decrease the size of the source relative to the hologram
There are actually two questions here:
How deep can you record? how deep can you see?
The depth of recording depends on the coherence length of the laser. The laser has to be coherent within the path difference between the two beams, ie the distance from plate to furthest point of object away from plate and back to plate. Usually, unless there's an etalon, it's an inch or so. To find the coherence of your laser. set up a Michaelson and make sure the two mirrors are exactly the same distance from the beamsplitter.and slowly move one mirror back. The fringes start getting less sharp. When the fringes start losing definition, the difference in the mirror seperation is the coherence length.
The depth with which you can see depends on what you're seeing it with. The smaller the source of the light relative to the hologram, the deeper you can see. If you're using an ordinary bulb with a filament the filament length is the source size that the hologram "sees". The closer the hologram to the bulb, the larger the filament size appears to the hologram and the smaller the depth of the image.Usually, under these conditions, the image depth is almost zero. As you move the hologram away, the filament size, relative to the hologram, decreases and you see more depth. About two or three feet away, you can see depth of an inch or so. If you're using a fluorescent light, especially one with a diffuser, the source size is huge and you're not going to see a great deal of depth, if any at all. If you're using a halogen the filament sizer is much smaller, allowing greater depth. Halogens still have filaments, so the further away, the deeper you can see. If you're using the sun, the image size is almost zero and you can see quite a lot of depth.