Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Patent
1995-05-04
1997-10-28
Tran, Thang V.
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
369 13, 369 4431, G11B 700
Patent
active
056823665
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an apparatus for recording signals on an optical disc.
BACKGROUND ART
In the past, it has been the practice with the optical disc recording apparatus so that when signals are recorded on an optical disc, the operation of confirming whether the written signals can be correctly read out is performed for the purpose of enhancing the reliability of the signals recorded on the optical disc.
The most common one of the known methods is a method known as the RAW (read after write) check. According to this method, after the recording of a signal on a certain data region of an optical disc or immediately after the recording, the operation of reproducing the recorded signal is performed so as to check the reproduced data and thereby to check whether the signal has been recorded correctly.
FIG. 6 is a block diagram showing the construction of a conventional device for performing the RAW check. In FIG. 6, the laser beam emitted from a head 622 is first projected on an optical disc 621 and the reflected light from it is received by the photodetector in the head 622. The resulting output signal from the photodetector is outputted as binary coded data through a reproducing circuit 623 and a binarization circuit 624. In this way, the signal recorded on the optical disc 621 is read out in the form of binary coded data. This binary coded data is converted into parallel data by a serial/parallel converter 625 and the data read out is subjected to error correction by an ECC decorder circuit 626 thereby confirming whether the recorded signal can be reproduced as the correct data.
Also, it has been known in the past that the frequency band of an amplifier utilized for the detection of a servo signal for the servo control is sufficient if it is on the order of several KHz.
The servo control is "a control system so constructed that a controlled system follows up arbitrary changes of a desired value" and generally the focusing control of the optical disc apparatus is such that a disc surface position is the desired value and the focal point of a laser beam is caused to follow up this surface position. Also, in the case of the tracking control the desired value is the central position of a data recording portion on the optical disc and a laser beam is projected on this surface position thus causing the center of the resulting light spot to follow up the surface position. A control element is mainly composed of an electric system so that the difference between the desired value and the controlled system or the current position is converted into an electric difference signal and the signal is sent to the controlled system in the feedback system so as to reduce the difference to zero.
Further, the servo controls employed by the optical disc recording and reproducing apparatus include for example a head movement control for moving the signal read/write head to the desired position, a focusing control for positioning the focal point of light entering into and emerging from the head to a signal recording portion of the disc and a tracking control for causing the focal point of the light to follow a track on the disc and the signals used for these controls are servo signals.
With the above-mentioned conventional techniques, however, the reproducing operation for the data checking of the written signals is performed after the writing operation during the signal recording and therefore a long time is required as compared with the recording operation without the RAW check. While it is conceivable to add a separate head which performs a reproducing operation for data checking purpose to overcome the problem of time consumption, there is the disadvantage of requiring an additional head optical system.
DISCLOSURE OF INVENTION
It is an object of the present invention to provide an optical disc recording apparatus which requires no additional head optical system and capable of reducing the time required for a data checking operation.
To accomplish the above object, an optical disc recording a
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Kurita Shinichi
Saito Jun
Yamanaka Yoshihiro
Nikon Corporation
Tran Thang V.
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