So you made a hologram! But it is either not perfect or not even visible. Don't despair. We all have made holograms that are blank or have issues. I am going to run down the list of mistakes I have uncovered. I am not the best person to write this discussion but since no one else has one on-line I am going to give it a try. If anyone can help please drop me an e-mail.
Problem Cause Image Missing
Motion or improper developing
Card left in the object beam or reference beam after checking beam ratios.
Image Missing parts
If the object is missing parts then the object was in motion during exposure.
If the film is missing views then that portion of the film was in motion. (Air bubbles in the index matching fluid will cause this problem.)
Image "Drippy" This is caused by soft emulsions and/or excessive pressure during squeegeeing. Image Dim
Under or over exposure.
Motion of the bench or film.
Beam ratios wrong.
Image has Rainbow Lines Light entered the edge of the plate and bounced between the two surfaces. Make sure to block any light entering the edges of the plate during exposure and reconstruction.
Image has Circular Patterns (Bull's eye)
Dust under film when laminated to the backing plate before exposure.
Reflection Hologram Blurry
It is normal to only have 4 inches of usable depth. The actual depth is related to how narrow of a bandwidth you are using for reconstuction. If you are looking for greater depth adjust your development to narrow the reconstruction bandwidth. There will be a corresponding decrease in brightness.
Image has Black Lines on the Object Object moved slightly.
Laser changed frequencies during exposure.
Image Flashes at Extreme Viewing Angles
Laser beam was reflecting off something on the table and reaching the plate. It is important to card off any stray light from the beam. Image has Black Lines on the Plate The plate was moving during exposure.
Plate is Completely Dark
Plate won't Turn Dark in the Developer
Forgot to add part B for 2-part developer.
Image Flashes Rainbows from a Specific Location This spot is too bright. If the object is very shiny try spraying with a flatting spray. Flat clear lacquer works if you can't find flatting spray.
Rotating the polorization of the object beam with a 1/2 waveplate can turn off shiny parts of the object. Use a polorizer rotated to coincide with the reference polorization to view the object illumination as you rotate the 1/2 waveplate.
Diagnosing the Problem
Once you have identified the cause it is important to figure out exactly what corrective action will help.
This is one of the most common problems. To find out if you are stable it is useful to make an interferometer. I am going to describe three and you can choose which one you would like to use. Each has it's advantages and disadvantages.
This interferometer is the simplest interferometer. The laser shines through a beam splitter to make two legs that are 90 degrees to each other.
John Klayer's Method
Please free to contact me at: email@example.com
Copyright © 2002 Colin Kaminski