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Theory of Parallax Barriers
By SAM H. KAPLAN
The parallax barrier, which is a type of selective masking device now being applied in color television and in stereoscopic imagery, is discussed. A brief history along with the principle and geometric relationship underlying its operation is given. Various systems employing two or more image elements per aperture and utilizing the maximum image area are described. It is also shown that nonplanar and nonparallel arrangements are possible, and that plane barrier surfaces may be coupled to nonplanar image surfaces. Furthermore, lenses may replace the mechanical-type barriers resulting in a more light-efficient system. Formulae are presented and specific applications to multiple-color television tubes are discussed.
PARALLAX BARRIER may be defined as a masking device which, when interposed between an object space and an image space, prevents any given part of the image space from being sighted from any but a given set of predetermined directions. Since both light and electron beams travel along straight paths, the laws of geometric optics apply irrespective of direction of travel along this path. Consequently, parallax barriers can be utilized where a viewing screen is observed from predetermined directions as in stereoscopic imagery, or where a luminescent screen is impinged upon by electron beams coming from specified directions, as in color television tubes. Parallax barriers are now being used for both of these purposes.
Presented on April 21, 1952, at the Society's Convention at Chicago, 111., by Sam H. Kaplan, Consultant, 3713 W. Arthington, Chicago 24, 111.
Brief History
The concept of the parallax barrier is generally attributed to Berthier1 of France who suggested it in 1896. However it was first applied by Frederick E. Ives1 to produce stereoscopic still pictures in 1904. These were called "parallax stereograms" and required no separate viewing accessories. The substitution of lenses as an alternate to mechanical blocking barriers was proposed by Gabriel Lippman of France in 1908.2 A barrier system with more than two elements behind each barrier aperture was invented by C. W. Kanolt who obtained U.S. Patent 1,260,682 on March 26, 1918. His stereoscopic pictures were called "parallax panoramagrams" and revealed a multitude of stereoscopic views as the picture was viewed from different angles. A radial nonparallel-type barrier system was invented by B. T. Ivanof3 who first
July 1952 Journal of the SMPTE Vol. 59
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