Optical disk discriminating device

Details Optical disk discriminating device Optical disk discriminating device

1988-08-18

1991-03-26

McElheny, Jr., Donald

Dynamic information storage or retrieval

With servo positioning of transducer assembly over track...

Optical servo system

369 4427, 369 54, G11B 700

Patent

active

050035215

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

This invention relates to an optical disk discriminating device for discriminating the kinds of the disk, such as the optical disk dedicated to reproduction or the recordable optical disk, and may be applied for example to an optical disk recording and/or reproducing apparatus provided with the function of opto-magnetic recording.


BACKGROUND ART

There has been extensively provided an optical disk device dedicated to reproduction, including a CD player or a video disk player employing an optical disk such as a digital audio disk or so-called compact disk or a video disk. There is also proposed an optical disk recording and/or reproducing apparatus in which data may be recorded and/or reproduced with the use of a rewritable opto-magnetic disk.
It is noted that, for optically reading the information recorded on the optical disk, an optical pickup head is extensively used in which the laser light is radiated on the recording surface of the optical disk to detect the light reflected from the recording surface. The disk dedicated to reproduction presents reflectivity on the recording surface different from that on the recording surface of the recordable disk, such that, in the case of the optical disk dedicated to reproduction, such as the compact disk, about 90% of the light is reflected by the aluminium reflecting surface applied to the recording surface, whereas, in the case of the rewritable opto-magnetic disk, about 10 to 20 percent of the light is reflected from the opto-magnetic recording layer, such as the TbFeCo layer.
For assuring compatibility with respect to the compact disk in the optical disk recording and/or reproducing apparatus employing a rewritable opto-magnetic disk, it is necessary to switch the gains of the tracking servo or focus servo employing the reproduction outputs obtained at the optical pickup head, or occasionally to switch the polarities of the error signals in dependence upon the kind of the optical disk which is in use, since the reflectivities on the recording surfaces of the disk dedicated to reproduction and the recordable disk are different from each other, as discussed hereinabove.
Thus the present invention is aimed to realize an optical disk recording and/or reproducing apparatus wherein the operation of the optical disk recording and/or reproducing apparatus is switched automatically in dependence upon the kind of the optical disk to enable both the disk dedicated to reproduction and the recordable disk to be reproduced, and provides an optical disk discriminating device which is adapted for discriminating the disk dedicated to reproduction and the recordable disk from each other.


DISCLOSURE OF THE INVENTION

An optical disk discriminating device comprising an optical pickup for detecting the light reflected from the recording surface of the disk, the optical pickup including means for irradiating the recording surface of an optical disk with a beam of light, photosensor means for converting incident light into a corresponding electrical output signal, an objective lens for focussing the light reflected by the optical disk's recording surface onto the photosensor, servo means for shifting the objective lens along its optical axis into and out of its focussed state, and discriminating circuit means having level comparator means and supplied with the photosensor's output signal for comparing its signal level obtained in the vicinity of the focussed state of the objective lens with a reference level and producing an error signal output which is supplied to the servo means, characterized in that the discriminating circuit means, includes means for discriminating the type of optical disk which is being read on the basis of the difference in magnitude of the photosensor's output signal caused by the difference in reflectivity of the recording surface of the optical disks.


BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the essential construction of an embodiment of an optical disk discriminating device according to the present inven

REFERENCES:
patent: 4611317 (1986-09-01), Takeuchi et al.
patent: 4642803 (1987-02-01), Drexler
patent: 4685098 (1987-08-01), Yoshida
patent: 4688203 (1987-08-01), Koishi et al.
patent: 4831611 (1989-05-01), Sasaki et al.

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