Optical disc recording and reproducing apparatus

Details Optical disc recording and reproducing apparatus Optical disc recording and reproducing apparatus

2000-06-21

2004-06-01

Hindi, Nabil (Department: 2651)

Dynamic information storage or retrieval

With servo positioning of transducer assembly over track...

Optical servo system

C369S094000, C369S044250, C369S044260, C369S044350

Reexamination Certificate

active

06744705

ABSTRACT:

This application is based on application No. 11-74996 filed in Japan, the contents of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to an apparatus for recording and reproducing data to or from an optical disc, or more specifically, to apparatus discriminating a read only optical disc from a recordable optical disc to perform a suitable reproducing processing dependent on a type of the optical disc.
2. Related Art
In recent years, there have widely been provided a minidisc (MD) recorder, an MD player and the like which can record and reproduce information data by using, as an optical disc, for example a minidisc to be one of writable optical magneto discs.
The MD recorder and the MD player are optical disc recording and reproducing apparatuses which can reproduce both a read only optical disc and a recordable optical disc in the same manner as a compact disc (CD) player and the like.
A first conventional example of such an apparatus, the apparatus is generally known, which discriminates whether an optical disc is a read only optical disc or a recordable optical disc by a sensor hole provided on a cartridge of the optical disc, and switches automatically an operation corresponding to the type of the optical disc for reproducing data.
As a second conventional example of the optical disc recording and reproducing apparatus, an optical disc recording and reproducing apparatus has been disclosed in Japanese Patent Laid-Open Publication No. 3-181062. The apparatus notices a difference in a reflectance on each recording plane of a read only optical disc and a recordable optical disc. The apparatus discriminates whether the optical disc is the read only optical disc or the recordable optical disc based on a difference in a peak level of a reproducing RF signal which is a detection output from the optical pickup. The optical pickup is obtained when an objective lens of an optical pickup is forcibly moved in the direction of an optic axis, that is, when the forcible movement is specifically carried out from a predetermined position beyond a focalized position. Then, the apparatus switches automatically operating conditions depending on the type of the optical disc.
However, each of the optical disc recording and reproducing apparatuses according to the first and second conventional examples has the following problems.
More specifically, in order to automatically switch the operating conditions corresponding to the type of the optical disc and to perform reproducing, it always needs to discriminate independently whether the optical disc is a read only optical disc or a recordable optical disc. In order to attach the optical disc and then reproduce the optical disc, it is required that the operation for discriminating the type of the optical disc should be separated from the operation for switching the operating conditions of the apparatus based on the result of the discrimination and the operations should be interlocked. Thus, timing management is required for each operation.
In the optical disc recording and reproducing apparatus according to the first conventional example, moreover, a detector is required for discriminating the type of the optical disc by using the sensor hole provided on the cartridge holding the optical disc. It causes an increase of the number of components and a cost. In addition, in the case of an optical disc recording and reproducing apparatus of a portable type, it is necessary to provide a space for the detector for discriminating the type of the optical disc, which obstructs a reduction in the size of the apparatus.
In the optical disc recording and reproducing apparatus according to the second conventional example, furthermore, the objective lens of the optical pickup should be passed through the focalized position once in order to discriminate the type of the optical disc. In reproducing operation, for both the read only optical disc and the recordable optical disc, it is necessary to forcibly move the objective lens of the optical pickup toward the focalized position again, and perform the focus servo. Consequently, it takes a long time from the operation for specifying the reproducing operation by a user to the start of the reproducing operation of the is optical disc.
The present invention solves the above-mentioned conventional problems. It provides an optical disc recording and reproducing apparatus which can rapidly and reliably discriminate the status of attachment of an optical disc in an optional position on a disc without requiring a detector other than an optical pickup such as a detector for performing discrimination using a sensor hole provided on a cartridge of the optical disc. The apparatus, without a complicated structure, can also apply a focus servo on optimum operating conditions according to the type of read only and recordable optical discs to perform a reproducing operation simultaneously with the discrimination processing. The apparatus can also shorten a time required from the reproducing operation by a user to the start of the reproducing operation.
SUMMARY OF THE INVENTION
In order to solve the above-mentioned problems, the optical disc recording and reproducing apparatus according to the present invention is characterized in that the level of a focus error signal and a peak occurred before focus is obtained are detected while an objective lens is forcibly moved from a predetermined position toward the focalized position (where the focus is obtained), presence of the optical disc and a type of the optical disc (read only type/recordable type) are discriminated based on a certain level, and a focus servo is switched to start a reproducing processing before the objective lens which is being moved toward the focalized position reaches a focalized position when the result of the discrimination indicative of load of the optical disc is obtained.
According to the apparatus with the above described structure, it is possible to rapidly and reliably discriminate the status of load of an optical disc at any position on a disc without requiring a detector other than an optical pickup such as a detector for performing discrimination using a sensor hole provided on a cartridge of the optical disc and without making a structure complicated. It is also to apply a focus servo on optimum operating conditions according to the type of optical discs to perform a reproducing operation simultaneously with the discrimination processing, and to shorten a time required from the reproducing operation by a user to the start of the reproducing operation.
In a first aspect of the present invention, an optical disc recording and reproducing apparatus is provided for recording and reproducing data to an optical disc. The apparatus drives an objective lens in a direction of an optic axis, irradiates a light beam on the optical disc through the objective lens, actuates a focus servo to the objective lens in response to a focus error signal generated based on reflected light from a recording plane of the optical disc, thereby reproducing data recorded on the optical disc.
The apparatus comprises a gain setting section for setting a gain for the focus error signal, and a disc discriminating section for discriminating whether a type of the optical disc which is loaded in the apparatus is a recordable type or a read only type, and discriminating whether the optical disc is loaded in the apparatus.
The gain setting section sets the gain for the focus error signal to a first gain which is specified to a recordable type optical disc before the loaded optical disc is discriminated to be of either of a read only type or a recordable type by the disc discriminating section, and switches the gain of the focus error signal to a second gain which is specified to an read only type optical disc when the optical disc is discriminated to be of the read only type by the disc discriminating section.
While the objective lens is moving toward a focalized position, the disc discriminating secti

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