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Pseudo-split beam technique by Tom B.
For the transfer, I had my uncollimated laser (with cylinder lens to square up the elliptical beam) at one end of table pointing up at 8" f/5 collimating mirror on tripod at other end (not on table). The collimated beam bounced down to the transfer setup at the Brwster angle, and was fat enough to serve as a reference beam for H2 (with a large 4x5 ND filter over it to reduce intensity, and to directly illuminate H1, another 4x5 reflection holo about 6 inches away.

H1 was made with a similar overhead pseudo-split-beam setup, ND filter over plate, objects positioned far enough away not to be shadowed. The object gets moved into the film plane during the transfer. A master bigger than the final H2 would have been better to increase the useful viewing angle.

I'd been meaning to mention this unusual technique sometime, but never got around to it. There's a lot of limitations, but it's nice not to have to worry about dealing with high-power collimated beams, spatial filters, etc.

The table is 14" x 28" x 1/4" steel plate sitting on 1/4" bubble-pack on a concrete basement floor. I can pound the floor next to it and see no fringe movement (other than from air currents etc.) Settling time from tapping the table is very fast - a second or less. For a while, I had the table coupled to the floor through plasticene balls, but found that bubble pack worked just as well, if not better because of the broad area mushy coupling of the bubble pack which might be helping to suppress resonances in the steel plate. It helps of course to have a very stable concrete floor to play on.


Overview of setup.


8" f/5 mirror on plywood mount and transfer setup, power supply below.



 Dual plate holder made from used Canon auto bellows and angle iron. The obligatory porcelain kitty is helping to hold up the black cardboard barrier that blocks stray light from the laser.


 Home-made diode laser mount with cylinder lens on wee tripod.


A nice hologram!
From Tom: "(H2) so cute I could puke, a sure sign of greatness."


From Tom: "(H2) Space Kitty fondles shiny ornament, get unpleasant surprise."


Notes on photographing reflection holograms:

I used an elderly Kodak 1.2 megapixel digicam on a mini-tripod and overhead halogen lighting. I think I used macro mode. The film was carefully cleaned and squashed under clean glass, then tilted back for best brightness from the camera's point of view. Since the flash can't be used, exposures would be too long for hand-held shooting, hence the tripod. To keep reflections from the camera body out of the image, I cut a hole in a piece of 8x11 black card stock (painted black to make it darker) just big enough for the camera lens to stick through. Some care was needed when pressing the shutter button to avoid jiggling the camera and blurring the image. Images were cleaned up using PaintShop Pro V6 or 7. I probably ended up removing a few distracting dust specks from the images. Contrast and brightness were adjusted for best looking image without misrepresenting the appearance of the hologram.


Feb 25, 2004


Title: fishdream
Author: Tom Burgess Feb 24/04
Medium: BB-640 4x5 plate, 3% TEA pretreatment
Setup: single beam Denisyuk reflection
Laser: Panasonic LNCQ05 660 nm diode, cylinder lens for 8 degree
X and Y divergence
Exposure: 15 seconds at 100 microjoules/cm2
Chemistry: Metol/Ascorbic acid developer, Brilland bleach
Lighting for pics: OptiLeds Amber LED at about 3 feet
Camera: Kodak DC3400
Fish credits: Tub o' Ocean Animals Inc.
Cat artist: Lesley Anne Ivory

The stereo pair is meant for the "cross-eyed" viewing method. Zoom the image size to a couple of inches across, get close to the
monitor and try to merge the pair. Being nearsighted helps.

March 29, 2004

The Holographers - a wry meta-commentary on cooperative holography