Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Reexamination Certificate
1999-03-10
2001-07-03
Edun, Muhammad (Department: 2651)
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
C369S044280
Reexamination Certificate
active
06256275
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a disc reproducing apparatus for reproducing an optical disc such as a CD-ROM or a DVD and a method for detecting its vibration.
2. Description of the Related Art
Recently, the speed-up (improvement of the reading speed of data) of disc drives for reproducing an optical disc such as a CD-ROM or a DVD is remarkable. By speeding up the disc drive, when a disc having a mass eccentricity (disc with its center of gravity deviated from the center of rotation) is reproduced by such a disc drive, the vibration generated in synchronization with the rotations of the disc becomes a prominent problem. This vibration is a factor to deteriorate the tracking performance of an optical pickup, resulting in lowering the data reading performance. The vibration and noise which leak out of the drive increase, and the use environment is remarkably degraded.
Conventionally, in order to suppress vibration generated when the disc having the mass eccentricity is reproduced, the vibration of the optical pickup and the like is directly detected by a sensor using an oscillator, and for example, a reproducing speed (transfer rate) is lowered if the vibration exceeding a predetermined value is detected.
But, such a method requires, in addition to a vibration sensor, many additional components such as a circuit for A/D conversion of the output from the vibration sensor to input a controller, causing a problem of increasing assembling man-hours and costs. Since a piezoelectric element type impact sensor is sensitive to surrounding electromagnetic noise, special consideration must be given to the mounting method and the use. In this connection, the cost is increased. In addition, these vibration sensors have a problem of having a detection error due to deviation or the like of parts.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the invention to provide a disc reproducing apparatus which can detect very accurately the magnitude of vibration caused by the mass eccentricity of a disc when it is driven at a high speed, and a method for detecting the vibration.
It is another object of the invention to provide a disc reproducing apparatus, which can detect very accurately the magnitude of vibration caused by the mass eccentricity of a disc without using any sensor part for detecting the vibration, and a method for detecting the vibration.
It is still an object of the invention to provide a disc reproducing apparatus which can determine an amount of mass eccentricity of a disc with great accuracy.
In order to achieve the objects of the invention, the disc reproducing apparatus according to the invention comprises an optical pickup which reads out information recorded on a disc as an RF signal and generates a tracking error signal; and a vibration detection means which detects vibration of the disc based on the RF signal and the tracking error signal output from the optical pickup.
According to the invention, the vibration detection means includes a displacement detection means which detects, based on the RF signal and the tracking error signal output from the optical picking, a first displacement of the optical pickup and the disc produced in a direction of the disc surface when the disc is driven at a first speed and a second displacement of the optical pickup and the disc produced in a direction of the disc surface when the disc is driven at a second speed which is faster than the first speed; and a calculation means which determines, as vibration resulting from the mass eccentricity of the disc, a difference between the first displacement and the second displacement respectively detected by the displacement detection means.
The magnitude of vibration caused when the disc is driven at a high speed is a sum of the amount of mass eccentricity of the disc and the vibration caused by the mass eccentricity and the high-speed driving of the disc. When the disc is driven at a low speed, e.g., 1×speed, an amount of vibration caused by the mass eccentricity of the disc can be considered to be substantially zero. Therefore, only the vibration component caused by the mass eccentricity of the disc can be extracted by subtracting the first displacement detected at the low speed driving from the second displacement detected at the high speed driving.
Thus, the disc-reproducing apparatus according to the invention uses the RF signal and the tracking error signal output from the optical pickup to detect the vibration caused by the mass eccentricity of the disc. Consequently, a sensor component for detecting vibration can be eliminated, and the problem that the vibration could not be detected with great accuracy because of the sensitivity of the sensor component and the deviation of the mounting position can be remedied.
According to the invention, the first displacement detected when the disc is driven at a low speed, e.g., 1×speed, substantially does not include the vibration component caused by the mass eccentricity of the disc. Therefore, the present invention judges the first displacement as the amount of mass eccentricity of the disc and can automatically reject the disc, which has the amount of mass eccentricity exceeding a predetermined value, as a nonconforming disc.
REFERENCES:
patent: 4703468 (1987-10-01), Baba et al.
patent: 5202872 (1993-04-01), Shinada
patent: 6028826 (2000-02-01), Yamamoto et al.
patent: 10-69709 (1998-03-01), None
Eguchi Toyokazu
Masubuchi Hayato
Sakuma Satoshi
Edun Muhammad
Kabushiki Kaisha Toshiba
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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