Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Patent
1993-04-06
1994-05-03
Young, W. R.
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
369 54, 369 58, 369 50, 369 4434, C11B 700
Patent
active
053094247
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to an optical recording apparatus for recording data by irradiating an optical recording medium with a light beam for pit formation.
BACKGROUND ART
Recently, a disk-shaped recording medium, such as an optical disc or a magneto-optical disc, utilizing the optical or magneto-optical signal recording/reproducing method, has been developed and presented to the market. As such disc-shaped recording medium, there are known a recording medium of the read-only-memory type (ROM) such as a so-called compact disc (CD), a so-called write once type recording medium on which data can be written only once by the user, and a so-called overwrite type disc, such as a magneto-optical disc, on which data re-recording is possible.
With a recording/reproducing apparatus for an optical disc, in which data are recorded or read out on or from the above mentioned write once type or overwrite type optical disc, the recording track on the optical disc is scanned by a light beam for data recording and/or reproduction, whilst the optical disc is rotationally driven at a constant angular velocity or at a constant linear velocity by spindle servo, and whilst focusing servo and/or tracking servo are supplied to an optical head on the basis of detection output of a photosensor adapted for sensing the light beam irradiated on and reflected back from the disc. The photosensor is enclosed within the optical head along with a laser diode which is driven by a laser driving circuit for outputting the light beam for data recording and/or reproduction.
With the recording/reproducing apparatus for an optical disc in which the recording track is scanned in this manner by the light beam for data recording and/or reproduction, if the power of the light beam scanning the recording track during the recording mode is too low, data cannot be recorded reliably, whereas, if the power of the light beam scanning the recording track during the reproducing mode is too high, serious effects may be produced, such as destruction of data recorded on the recording track. According to the Japanese Patent Kokai Publication No. 53-46633(1978), the intensity or volume of the light beam for data recording and/or reproduction is detected and the driving circuit for the laser diode adapted for outputting the laser beam is feedback controlled while a so-called APC servo loop for maintaining a constant beam power of the light beam is switched as a function of the prevailing operating modes for suitably switching the beam power.
Meanwhile, with an optical recording/reproducing apparatus in which the recording track is scanned by the light beam for recording and/or reproducing data on or from an optical recording medium, the light reflected from the optical recording medium is detected by an optical head, and the above mentioned focusing or tracking servo is performed on the basis of the resulting detection output. However, since the reflected light from the recording medium has been modulated by the pits formed on the recording track of the recording medium, that is, the recorded data, the operation of the servo system tends to be affected by the pits.
With the optical recording apparatus, the recording track on the optical recording medium is scanned by the recording light beam radiated by a laser diode driven by pulses in accordance with the record data during the recording mode, thereby forming the pits for data recording. However, inasmuch as a time delay .GAMMA. in the order of 300 to 400 ns is produced from the time when a recording light beam obtained by driving a laser diode by driving pulses consistent with the record data is irradiated until the pits P start actually to be formed, as shown in FIG. 1, the detection output waveform of the recording light beam reflected after irradiation on the recording track is also modulated with the above defined time delay. Thus the conventional servo system operating on the basis of the reflected light of the recording light beam exhibits a strong dependency on the pattern of the pits th
REFERENCES:
patent: 4894816 (1990-01-01), Sukeda et al.
patent: 4949311 (1990-08-01), Barnard
patent: 5109366 (1992-04-01), Moriya et al.
Edun Muhammad N.
Eslinger Lewis H.
Maioli Jay H.
Sony Corporation
Young W. R.
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