Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Reexamination Certificate
1998-10-19
2001-08-07
Edun, Muhammad (Department: 2651)
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
C369S053410
Reexamination Certificate
active
06272087
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to optical disc apparatuses and, more particularly, to an optical disc apparatus which is adapted to discriminate the kind of a disc depending upon the level of a reproduced signal outputted, for example, from an RF amplifier.
2. Prior Art
In the conventional optical disc apparatuses of this kind, the reproduced signal is adjusted to a constant level by an AGC (Automatic Gain Control) circuit of an RF amplifier so that the signals recorded on the disc can be reproduced in accordance with a disc type.
In such prior art apparatuses, however, because the reproduced signal level is constantly adjusted by an AGC circuit, the normal disc (CD-ROM) and the rewritable disc (CD-RW) have respective RFDC signals generally at the same level. Accordingly, the discrimination on the disc type is impossible based on the reproduced signal outputted from the RF amplifier. This raises a problem that, if the disc type is incorrectly discriminated, the reproduced signal possibly exceeds a dynamic range of the AGC circuit as a result of a significant difference, between CD-ROM and CD-RW, in the reproduced signal level by the RF amplifier.
SUMMARY OF THE INVENTION
It is therefore a primary object of the present invention to provide an optical disc apparatus which is capable of correctly discriminating disc types.
An optical disc apparatus according to the present invention comprises: an RF amplifier which receives an RF signal outputted from an optical pickup and outputs a reproduced signal; a discriminating means which discriminates a type of a disc depending upon a level of the reproduced signal outputted from said RF amplifier; and an off means which turns an AGC circuit of said RF amplifier off when said discriminating means discriminates the type of said disc.
That is, the present invention is an optical disc apparatus characterized in that the RF amplifier AGC circuit is turned off when a type of a disc is discriminated depending on the level of a reproduced signal outputted from the RF amplifier.
Thus, when a disc is inserted into the optical disc apparatus, a focus search is carried out for the lens provided on the optical pickup. At this time, disc type discrimination is also started by the discriminating means and the off means first brings the RF amplifier AGC circuit to off. A laser beam irradiated by the optical pickup is reflected by the disc, and its reflection light is input to the RF amplifier. Disc type discrimination is made based depending upon a level of a reproduced signal outputted by the RF amplifier.
Incidentally, an adjusting means set a gain of the AGC circuit based on a result of this discrimination.
According to the present invention, the RF amplifier AGC circuit is turned off when a disc type is discriminated. Therefore, it is possible to correctly discriminate a disc type depending upon a level of a reproduced signal from the RF amplifier.
The above described objects and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 5060218 (1991-10-01), Chiyomatsu
patent: 5684771 (1997-11-01), Furukawa et al.
patent: 5959955 (1999-09-01), Choi
patent: 6061318 (2000-05-01), Hwang
Edun Muhammad
Funai Electric Co. Ltd.
Lackenbach Siegel Marzullo Aronson & Greenspan P.C.
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