Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Reexamination Certificate
1998-01-05
2001-06-26
Huber, Paul W. (Department: 2651)
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
C369S044350, C369S116000, C369S124100
Reexamination Certificate
active
06252834
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the invention
This invention relates to an optical disc device capable of coping with plural types of optical discs, and a method for discriminating optical discs.
2. Description of Related Art
As optical discs, compact discs are in widespread use, such that optical discs of the CD type are used in many fields, to say nothing of the field of musical application. The CDs for music are usually designed as replay-only media. However, an overwrite type disc termed compact disc recordable (CD-R) is also commercialized.
On the other hand, an optical disc termed a digital versatile disc/digital video disc (DVD) has also been developed as an optical disc suitable for multimedia use. This DVD is proposed as being adaptable to a wide field of applications, such as for video data, audio data or computer data. The DVD, which is an optical disc of the same size as the CD (12 cm in diameter), has a significantly increased recording capacity.
Meanwhile, in keeping pace with development of a new optical disc, it becomes desirable to provide an optical disc device exhibiting interchangeability between conventional and newer types of optical discs.
As for the DVD, it is desirable to develop an optical disc device capable of coping with both the CD and the DVD. However, since the CD and the DVD differ in reflectivity depending on, for example, the difference in structure of the signal recording layer of the optical disc, the RF signals obtained by an optical pickup is varied in signal level, depending on the optical disc type, whilst optimum values of parameters of various servo systems, such as focusing servo or tracking servo systems, are also changed.
Therefore, an optical disc device, adapted for coping with plural optical disc types, is required to correctly discriminate the type of optical disc on loading the optical disc thereon.
If the disc is of the type in which an optical disc is housed in a cartridge, the disc type can be easily discriminated by providing a cartridge discriminating hole. However, if the optical disc is not of the type housed in a cartridge, and moreover the optical disc itself is of the same size, this mechanical discrimination system cannot be used.
Moreover, if special components or units are provided for discriminating the disc type, such as a sensor, the device is undesirably complicated in structure, while the manufacturing costs are also raised.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an optical disc device and an optical disc discriminating method in which plural optical disc types having different numbers of signal recording layers are discriminated and an operating mode corresponding to the optical disc type is set by control means based on the discriminating output for reliably reproducing the plural types of optical discs.
In one aspect, the present invention provides an optical disc device including a laser light source for radiating a laser light beam illuminated via an objective lens on a signal surface of an optical disc, laser light volume detection means for detecting the light volume of the laser light radiated from the laser light source, automatic power controlling means for controlling a laser output of the laser light source so that a detection output by the laser light volume detection means will be constant, return light detection means for detecting the return light of the laser light beam radiated by the laser light source and reflected by the signal surface of the optical disc, focusing control means for displacing the objective lens along the optical axis responsive to the focusing error signals generated on the basis of a detection output of the return light detection means for controlling the focusing state of a beam spot of the laser light on the signal surface of the optical disc and controlling means for controlling the closed-loop gain of the automatic power controlling means to a gain in meeting with the reflectivity of the optical disc based on a detection output of the return light detection means which prevails when focusing is applied to the signal surface of the optical disc by the focusing control means.
In another aspect, the present invention provides an optical disc device including a laser light source for radiating a laser light beam illuminated via an objective lens on a signal surface of an optical disc, laser light volume detection means for detecting the light volume of the laser light radiated from the laser light source, automatic power controlling means for controlling a laser output of the laser light source so that a detection output by the laser light volume detection means will be constant, return light detection means for detecting the return light of the laser light beam radiated by the laser light source and reflected by the signal surface of the optical disc, focusing control means for displacing the objective lens along the optical axis responsive to the focusing error signals generated on the basis of a detection output of the return light detection means for controlling the focusing state of a beam spot of the laser light on the signal surface of the optical disc and controlling means for controlling the closed-loop gain of the automatic power controlling means to a gain in meeting with the reflectivity of the optical disc based on a detection output of the return light detection means which prevails when focusing is applied to the signal surface of the optical disc by the focusing control means.
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Application No. 08/915,877, Feb. 1, 2000.
Patent Abstracts of Japan, JP 8-83465, published Mar. 26, 1996, Sony Corporation.
Huber Paul W.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Sony Corporation
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