Shutters for Holography
Making a shutter is good for many reasons. While many great holograms have been made with a black card as a shutter, a real shutter allows you to remain farther from the bench during exposure and will increase the stability of your system. Since stability is so extremely important one should choose a shutter that does not induce vibrations.
While many people have used shutters from cameras with sucess I have worried about the vibrations induced by the shutter. I bought a milli-amp meter from Radio Shack for $4 and disassembled it. I removed the needle and replaced it with a strand of copper wire. On this wire I glued 1/4 of a slip cover from a microscope slide and glued a piece of mylar from a ballon to it with UV cure glue from Norland. I now have a movable mirror but the meter was grossly out of balance. On the lower side of the needle there is a counter weight. I carefully wrapped a strand of wire around it with two pairs of tweezers and slowly filled it with solder until the balance was restored. The only things left to do were to find a suitable resistor that allowed the meter movment to move slowly and hit the end point without vibration and to mount the meter.
Thanks to a piece of inspiration and some testing from Tom B. I decided to make a beam dump. This allows me to dispose of the beam without any back reflections and without having it go somewhere that might fog the film. I took a glass shade 12 welding filter and cut it in half lengthwise. I then bounced the beam into the middle of the two plates mounted in parrallel so it entered at a 45 degree angle. At each point the glass absorbs much of the light and after only a few bounces I can not see the beam.