Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Patent
1979-10-09
1982-05-04
Cardillo, Jr., Raymond F.
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
369 58, G11B 700
Patent
active
043285740
ABSTRACT:
A method and apparatus for detecting crossmodulation distortion on an optical sound track by detecting variations in the light transmitted through a predetermined area on the sound track, the predetermined area being selected such that its transmittance varies substantially only with the amount of crossmodulation distortion on the sound track. The predetermined area preferably has a dimension along the sound track which is a whole number multiple of, and substantially greater than, the wavelength of a high frequency test signal. Light is also transmitted through a second predetermined area on the sound track which clips the high frequency test signal, thereby providing a low frequency phase reference for determining the relative exposure of the film. In an alternate embodiment, the predetermined areas are divided into primary and secondary areas, mutually spaced by a distance which is out-of-phase with respect to the wavelength of a low frequency test signal. Crossmodulation distortion information is obtained by comparing the light transmitted through both areas. Instead of single predetermined areas, multiple areas spaced by whole number multiples of the low frequency signal wavelength can be used to improve the resolution of the system's frequency response. A mask with defined apertures controls the light paths. Testing for crossmodulation distortion can be done by simply moving the film by hand a short distance through the test equipment. Because crossmodulation is continuously monitored, diagnostic testing is also possible.
REFERENCES:
patent: 1769908 (1930-07-01), De Forest
patent: 2538354 (1951-01-01), Corcoran et al.
patent: 3728495 (1973-04-01), Vlahos
patent: 4044207 (1977-08-01), Vlahos
Tremaine, Audio Cyclopedia, 2nd Ed., Sections 18.225-18.299, pp. 970-1,000, 1977.
Cardillo, Jr. Raymond F.
Koppel Richard S.
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