Dynamic information storage or retrieval – Storage or retrieval by simultaneous application of diverse... – Magnetic field and light beam
Patent
1988-09-28
1990-09-25
Richardson, Robert L.
Dynamic information storage or retrieval
Storage or retrieval by simultaneous application of diverse...
Magnetic field and light beam
360114, 369107, G11B 1110
Patent
active
049598210
ABSTRACT:
An optical pick-up for scanning a magneto-optically recorded disk in which the disk reflects a first principal beam onto a first photodetector. This first principal beam has a plane of polarization which is rotated in one direction. The recorded disk reflects a second principal beam onto a second photodetector. This second principal beam has a plane of polarization that is rotated in another direction. A data signal is generated from the difference between output photovoltages of the first and second photodetectors. A diffraction grating splits the main beam from a light emitting source, into the principal beams and into subsidiary beams. The main beam from the light emitting source is focused on the recorded disk through the diffraction grating. Auxiliary photovoltages are generated from the auxiliary beams, and these are subtracted for generating the data signal. The output voltage of the second photodetector has noise components that are in phase and which are generated by the main beam. This output voltage of the second photodetector contains also noise components of opposite phase that are generated by the subsidiary beams. The output signal of the first photodetector, on the other hand, has only noise components generated by the main beam.
REFERENCES:
patent: 4569035 (1986-02-01), Tomita
patent: 4691308 (1987-09-01), Takagi et al.
Morimoto Yasuaki
Zucker Friedhelm
Deutsche Thomson-Brandt GmbH
Fogiel Max
Richardson Robert L.
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