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Introduction

Overview

Optical Table

Environment

Laser

Beamsplitter

Mirrors/Lenses

Table Mounts

Optic Mounts

Plate Holder

Objects/Scenes

Resources

Environment

The room where the optical table is to be located should be on the ground floor of your home or in your basement. This allows the earth to dampen all or most ground vibrations caused by movement in adjacent rooms or nearby vehicular traffic. It is essential that no ground vibrations reach the table surface during the exposure of the hologram. The optical table discussed previously will dampen ground vibrations nicely. In the section on Creating Transmission & Reflection Holograms, I will show you how to set up a Michelson interferometer to visualize these potential vibrations as well as other types of movements that can affect your exposure (possibly air currents created by home air conditioning or heating, and additionally heat radiating from components caused by your hands transferring heat to a component after making last minute adjustments).

The optical table must also be located in a room that can be totally darkened. The reason for this is that when you are ready to expose a hologram, you will be placing a photographic (holographic) plate in a plate holder (without light-protection) on the optical table and no light other than that from the laser, during the exposure, should impinge on the plate. Silver halide emulsion plates, which you will be using, are sensitive to various visible wavelengths of light and the reason why the room must be completely dark. You will be using safelights which will allow you to see everything and not affect your plates or films. More on safelights later.

Your plate processing area must also be in a room that can be totally darkened. You can have your processing area in the same room as the optical table or in an adjacent room (preferably an adjacent room because of fumes from the processing chemicals possibly affecting unexposed plates and optical surfaces, although I cannot confirm this). I've done both ways, but in the last 45 years, I've always processed in an adjacent room. The processing area can also be anywhere in your house or in the building where you’re working. The exposed plate can be carried to the processing area in a light-proof box or light-proof envelope.

The room in which the optical table is housed should be large enough to accommodate an optical table at least 4 feet x 6 feet with a minimum of 3 feet of walking space around the table on three or four sides. If you can manage this on four sides, that's even better. The walking space between the table and adjacent areas will help you not to accidentally touch a table component as you walk around the table. Also needed is folding tables, shelving, and/or cupboard space to store photographic plates, optics, optical mounts, and other related setup items.

If the room is air conditioned by a single air conditioning unit, the unit will need to be turned off at least 60 minutes prior to the exposure. If the room is air conditioned or heated by a central home unit, it will need to be turned off by a thermostat at least 60 minutes prior to the exposure. If you can't turn off the central air conditioning or heating system, such as in a large building, and there's an input vent to the room, you will need to physically block the input vent. A 3/16 inch thick black foam core board held in place with duct tape works well. Any airflow over or around the optical table will cause the optical components to move during the exposure and destroy the holographic recording. Bottom line: the movement of certain components, during the exposure, of more than one-half of the laser light's wavelength of 632.8 nanometers (632.8 x 10-9 meters), will destroy the image.

The optical table room should be kept clean, no foods or drinks, and no smoking should be allowed. Smoke-related pollutants will eventually build up on optical surfaces and cause distortion and attenuation (absorption) of the laser beam.