Optical disk reproducing device with automatic focus control loop
AssigneeRohm Co., Ltd.
InventorsYuichi Kawada, Hiroshi Oyabu
Life of this patent
Estimating the term…
Abstract
In an optical disk reproducing device, through a provision of a control circuit, movement of focus point of laser beams is set at positions ahead or back to the focus position causing to enter into an automatic focus control loop, and a retry search signal for searching the focusing position is caused to be generated by the search signal generation means, thereby, a refocusing control in case when an automatic focusing servo loop can not be maintained can be started from the positions ahead or back to the focus position causing to enter into the automatic focus control loop.
Claims8
An optical disk reproducing device which includes a laser beam source which irradiates laser beams onto an optical disk, a photo detector which receives the reflection beams from the optical disk and generates a position error detection signal with respect to a focus position error for the optical disk, a detection circuit which receives the position error detection signal and detects a focus position of the laser beams locating in a range of an automatic focus control loop, and a focus servo device which changes over to the automatic focus control loop in response to the detection signal of the detection circuit and performs an automatic focusing of the laser beams for the optical disk in response to the position error detecting signal, characterized in that, the optical disk reproducing device further comprising,
- a driver which controls the focus position of the laser beams in response to a driving signal;
- a search signal generation means which generates as the driving signal a search signal which continuously advances or backs the focus position of the laser beams with respect to the optical disk;
- a memory means which stores the focus position of the laser beams at the moment in response to the detection signal from the detection circuit or a signal output value of the search signal generation means corresponding to the focus position;
- a first control circuit which causes the search signal generation means to generate as a retry search signal a drive signal which moves the focus of the laser beams from positions ahead or back to the focus position toward the focus position based on the focus position of the laser beams stored in the memory means or the signal output value stored in the memory means;
- and,
- a second control circuit which operates the first control circuit while releasing the automatic focus control loop when the detection signal from the detection circuit is stopped or when the detection signal with respect to the position error moves out from the focus position.
Dependencies are inferred from the claim text.