Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Patent
1989-06-12
1991-01-22
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
2502018, 369 4441, 369 4442, H01J 4000
Patent
active
049872923
ABSTRACT:
A method and apparatus for measuring the focus and tracking of a light beam on a medium in an optical data storage system. A split lens, comprising two halves of a lens separated along the optical axis and displaced from each other along the plane of the cut, is used to focus the light reflected or refracted from the medium onto a quad-cell. The quad cell comprises four light sensors arranged in four quadrants about a center point. According to the invention, the amount of light incident on quadrants of the quad-cell indicates the focus and alignment of the light beam on the medium. In accordance with another aspect of the invention, the above apparatus is used to measaure the collimation or distribution of intensity of a light beam. Another aspect of the invention is the manufacture of the split lens. A lens is sawed into two halves and the halves are mounted using a housing displaced from each other along the plane of the cut.
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Bouwhuis, G. et al., "Principles of Optical Disk Systems", Philips Research Laboratories, Eindhoven, pp. 70-81.
Allen Stephone B.
Digital Equipment Corporation
Nelms David C.
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