Producing a Computer Generated Hologram.
Noah Corwin, Syosset High School,
Harold Metcalf and John Noé,
Laser Teaching Center, University at Stony Brook 11794-3800.
A hologram is the recording upon photographic film of the interference
pattern caused by two beams of laser light, one direct from the laser and
one which has reflected from an object in its path. The beam that is
directed at the object is called the object beam, while the beam that goes
directly to the photographic plate is called the reference beam. The
hologram provides more information than a traditional photograph provides.
When the hologram is viewed, the reconstructed object looks
three-dimensional and its appearance changes with the viewing angle. A
computer generated hologram is different in that the interference pattern
is created using a computer and a printer. The printed hologram is viewed
by methods similar to a regular hologram, for example, by shining laser
light through it.
The type of computer generated hologram that will be created in this project was described in a paper by Thad G. Walker, from the University of Wisconsin at Madison. His method involves manipulation of the pixel data in a two dimensional black and white image, using a simple program in the C programming language, which is provided within the paper. A typical image could be initials, or simple graphic. The program uses a Fourier transform, to convert the image into an interference pattern. When laser printed at high quality on transparency paper, a laser beam projected through the pattern from the right distance will recreate the two dimensional pattern of the original image.