Dynamic information storage or retrieval – Control of storage or retrieval operation by a control... – Mechanism control by the control signal
Patent
1985-05-16
1988-07-12
Cardillo, Raymond F.
Dynamic information storage or retrieval
Control of storage or retrieval operation by a control...
Mechanism control by the control signal
369 32, 369 45, G11B 7095, G11B 7085, G11B 2108
Patent
active
047574879
ABSTRACT:
In a method of detecting track crossings on an optical disc, a light source irradiates a light beam onto an optical disc having guide tracks in the form of a recess and the light beam is reflected and diffracted into a zero order light beam and positive and negative primary light beams. The light beams are defocused so as to produce interference patterns between the zero light beam and the positive and negative primary light beams. The interference patterns are detected by a four split light detector disposed between two parts of a two split detector. The outputs of the detectors are fed to an adder and to a subtractor for producing a sum signal and a difference signal respectively. The sum signal and difference signal are fed to a phase detector. Defocusing of the light beams is effected by a focusing coil to which is fed the amplified output of an adder of a reference signal controlled by a control circuit.
REFERENCES:
patent: 4484319 (1984-11-01), Koishi et al.
patent: 4504938 (1985-03-01), Tajima
patent: 4512004 (1985-04-01), Nonaka
patent: 4525826 (1985-06-01), Nakamura et al.
patent: 4546460 (1985-10-01), Ando
Kato Kiichi
Yanagida Tsuneo
Burns Robert E.
Cardillo Raymond F.
Garland Steven R.
Lobato Emmanuel J.
Olympus Optical Company Limited
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