Optical information reading method for reducing laser noise usin

Details Optical information reading method for reducing laser noise usin Optical information reading method for reducing laser noise usin

1993-10-21

1995-09-05

Epps, Georgia Y.

Dynamic information storage or retrieval

Specific detail of information handling portion of system

Radiation beam modification of or by storage medium

369116, 369 54, 372 26, G11B 7125

Patent

active

054485487

ABSTRACT:
A method for optically reading recorded information by radiating laser light emitted from a semiconductor laser which oscillates in a single longitudinal mode to an information recording medium and by detecting laser light reflected from a recording face of the information recording medium is disclosed. In the method, the optical frequency of the laser light is modulated in order that the modulated optical frequency is a periodic function dependent on time, and the absolute value of a time differential coefficient R (Hz/s) of the periodic function, a spectral line width .delta. .nu. (Hz) of the laser light, and a time period .tau. (s) from the time when the laser light is emitted to the time when the laser light reflected from the recording face of the information recording medium reaches the semiconductor laser satisfy the condition of R.gtoreq..delta. .nu./.tau.. The periodic function varies to have a sawtooth waveform or a triangular waveform.

REFERENCES:
patent: 5313448 (1994-05-01), Sukeda et al.
M. Morimura et al., Optronics, No. 6 (Jun.), pp. 60-66, 1991, "Semiconductor Devices for Photonic Measurement Use".
H. Nishihara, Applied Physics, vol. 61, No. 1, pp. 2-13, 1992, "Integrated-optic Techniques Using Diffraction Gratings".
S. Matsui et al., Applied Optics, vol. 23, No. 22, pp. 4001-4006, 1984, "Low Noise Characteristics of V-channeled Substrate Inner Stripe Laser in Single-longitudinal-mode Operation".
T. Kobayashi et al., Shingakugihou OQE 87-153, pp. 65-71, 1987, "FM Heterodyne Measurement of Distance Using a Semiconductor laser".

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