Vectograph

A vectograph is a kind of stereoscopic technology that uses polarized glasses to view a three-dimensional photographic image embedded in a plastic sheet.

Polaroid Corporation invented a technique to make a polarized filter sheet more or less strongly polarized in response to a photographic image projected on it. When the sheet is processed, it appears relatively clear in normal light, but viewed through a correctly-oriented polarizing filter, the image is seen.

By stacking two of these sheets, a separate image may be transmitted to each eye, and when viewed through polarizing 3D glasses, the viewer sees a three-dimensional image.

Perhaps the most common image reproduced in this medium is the Titmus Fly Stereotest, which is used by Optometrists and ophthalmologists to determine if patients have normal steroscopic vision.

Joseph Mahler (cousin of famed composer/conductor Gustav Mahler) is the inventor of the Vectograph. Mr. Mahler immigrated to the U.S. from Czechoslovakia in 1938 with his wife Anna and two daughters Hana and Helen. He died in Laguna Hills, California in July 1981 at the age of 81.

One of the most seen vectographs was the large wall vectograph print advertisement that was displayed in Grand Central Station during 1940s of a candy rool of Life Savers. It was taken by Charles Debois Hodges who worked for Keystone using a Stereo Graphic camera before its processing by Polaroid.

Around 2000, the Rowland Institute, once part of Polaroid and now part of Harvard University, revived a modernized version of the technology under the name "StereoJet," but as of 2006, it is unclear whether the technology is available.