Re: How do you measure laser interference with cameras?

Greetings Kevin:

References:
1. Simple Holography, The Easiest Way to Make Holograms
By T. H. Jeong, Raymond Ro, Riley Aumiller (Lake Forest College)
and Misashi Iwasaki (Kyoto Institute of Technology)
with contributions from Jeff Blythe (University of Cambridge)
Edited by Alec Jeong

http://www.holokits.com/a-make_holograms.htm

2. Mad Science Archives: When waves collide, do both kinds of interference occur?

http://www.madsci.org/posts/archives/1997- 03/853194471.Ph.r.html

The process of interference between electromagnetic waves ranging from radio
waves to light waves is used for a large number of applications. The
application that you describe in your question is called Holography.
Holography is one of the most interesting uses of interference. Microwave
holograms are being used for radar antennas and to search for hidden weapons
on airline travelers. Light wave holograms are used to prevent tampering
and copying paper money and passports, drivers licenses and credit cards.
They also are used to preserve the design of sculptures and other works of art.

Interference occurs when electromagnetic waves of the same frequency cross
each other. The waves can be moving in the same direction, in opposite directions
or at an angle to each other. When the position of the crests and troughs of
two waves match each other they add and we obtain a bright spot and when the
position of a wave crest matches a wave trough the waves cancel each other
and we get a dark spot. An optical hologram is composed of an array of millions
of these interference points recorded on high resolution film plate. In
Reference 2. I have plotted the development of simple one dimensional
interference patterns.

The basic optical hologram is formed from the interference between two light
beams obtained from a common source, usually a laser. One beam comming directly
from the laser is called the Reference Beam and the second beam is
reflected from or transmitted through an object to be recorded is called
the Object Beam. In your question the beam looping around the microscope
is the Reference Beam and the beam passing through the microscopic object is
the object beam. These beams form a Transmission Hologram. If the object
beam was composed of light reflected from the microscopic object a
Reflection Hologram would be formed. Reflection holograms are very
difficult to make with a microscope and microscopic objects.

The interference between the object and reference beams forming the hologram
are usually recorded on high resolution photographic film. The difficulty
in making an optical hologram is to keep the distance between the object, the
film and some of the optics from moving (vibrating) less than about 1/10 of a
light wavelength during the several seconds (about 1 to 30 sec.) required to
expose a typical holographic film plate. Moving particles that move a few
micrometers (microinches) will not provide a stable inteference pattern and
will not show up in the hologram; however, fixed particles will be in the
three dimensional holographic image just as they were in the actual environment
of the object. This stability usually requires expensive optical tables, and lens
and mirror mounts to eliminate micro-vibrations.

However, a number of techniques for students to make simple holograms are in
presented in Reference 1. A large amount of information on holography with
dozens of links can be found in the Mad Science Archives when searching for
Holography. Unfortunatly a Google search for "Making Holograms" will come up
with about 100,000 web sites, a true information overload!

Best wishes for the New Year, Your Mad Scientist
Adrian Popa