Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Reexamination Certificate
1998-05-18
2001-04-24
Psitos, Aristotelis M. (Department: 2651)
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
C369S044290, C369S044350
Reexamination Certificate
active
06222802
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of Korean Application No. 1997-19222, filed May 19, 1997, in the Korean Industrial Property Office.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical disc drive, and in particular, to a device and method for automatically controlling a sled loop gain for determining a driving voltage level of a sled motor.
2. Description of the Related Art
An optical disc drive for use in a digital video disc (hereinafter referred to as DVD) player or a compact disc (CD) player performs a focusing operation for shifting a lens up and down, and a tracking operation for shifting the lens to the left and right to settle the lens to direct a laser beam in an on-track position.
The tracking consists of two tracking steps. One is to drive a sled motor in order for a pickup to approach a target track, and another is to control a driving voltage provided to a tracking actuator to finely shift the tip of the lens to the target track. The former tracking step can shift the lens widely, but can not shift the lens promptly due to an inertia moment. The latter tracking step has a fast response, but has a narrow movable range of the pickup.
Accordingly, in order for the lens to jump over many tracks, the optical disc drive first shifts the lens by using the former tracking step, and then performs a fine tracking by using the latter tracking step. Furthermore, when the optical disc drive is driven in the state that the laser beam is on-track, the lens is finely tracked by the latter tracking step so as to shift to an outer circumference along the track on the optical disc. In order to compensate for the lean of the lens toward the outer circumference due to the fine tracking, the optical disc drive shifts the pickup by means of the former tracking step.
However, the conventional optical disc drive has a fixed sled loop gain for controlling the driving voltage supplied to the sled motor to compensate for the lean to be equal to a minimum driving voltage VsmvO for shifting the pickup. On the other hand, every product has a slightly different minimum driving voltage Vsmv0 for driving the pickup to shift over the track. Therefore, each product has low reliability.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a device and method for automatically controlling a sled loop gain so as to control a driving voltage, detected when a laser beam passed through a lens and onto an optical disc is on-track after jumping tracks, to be changed to a minimum driving voltage.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
To achieve the foregoing and other objects, according to an aspect of the present invention, there is provided a device for automatically controlling a sled loop gain in an optical disc drive having a sled motor. The device includes a pickup for irradiating a laser beam onto an optical disc and receiving a reflected beam to read a signal recorded on the optical disc; a tracking error detector connected to the pickup so as to receive the read signal of the pickup, to detect a tracking error signal from the read signal; a phase compensator connected to the tracking error detector, to compensate for a phase deviation of the tracking error signal; a first lowpass filter connected to the phase compensator, to control the phase-compensated tracking error signal according to a fixed gain thereof; a controller to cause the pickup to jump N tracks when the laser beam is on-track, and determine the sled loop gain for controlling a signal output from the first lowpass filter to be changed to a minimum driving voltage upon completion of the track jump; a second lowpass filter to control the signal output from the first lowpass filter according to the sled loop gain generated from the controller; and a sled motor driver to drive the sled motor according to a signal output from the second lowpass filter.
According to another aspect of the present invention, there is provided a method for automatically controlling a sled loop gain in an optical disc drive having a pickup including a lens and a laser diode. The method includes the steps of: (a) compensating for a phase deviation of a tracking error signal detected from a signal read from an optical disc, and controlling the phase-compensated tracking error signal according to a fixed gain; (b) causing the lens to jump N tracks when a laser beam passed through the lens is on-focus and on-track; (c) reading the gain controlled signal generated at the step (a), if the laser beam passed through the lens is on-track after jumping N tracks; (d) determining the sled loop gain for controlling the signal read at the step (c) to be changed to a minimum driving voltage for driving a sled motor; and (e) controlling the signal output generated at the step (a) according to the sled loop gain.
REFERENCES:
patent: 4835754 (1989-05-01), Yamamoto et al.
patent: 5054013 (1991-10-01), Kawamura
patent: 5146443 (1992-09-01), Iwase et al.
patent: 5548569 (1996-08-01), Shimizume et al.
patent: 5886963 (1999-03-01), Abe et al.
patent: 5896353 (1999-04-01), Naohara
Psitos Aristotelis M.
Samsung Electronics Co,. Ltd.
Staas & Halsey , LLP
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