Focus servo apparatus

Details Focus servo apparatus Focus servo apparatus

1988-05-23

1991-04-23

Richardson, Robert L.

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With servo positioning of transducer assembly over track...

Optical servo system

369 4429, G11B 700

Patent

active

050105388

ABSTRACT:
In a focus servo apparatus for moving an objective lens in an optical disk drive from a distant position toward the surface of the disk and maintaining the lens in the correct focus position by means of a servo loop having a lead-in detection circuit for generating an acquisition signal when the objective lens is within the controllable range and a servo loop switch for closing the servo loop in response to the acquisition signal, a lead-in circuit generates a drive signal to move the objective lens into this range before the servo loop is closed. The drive signal rises to an initial peak, then falls back to a lower level. A bias signal is added to the drive signal when the optical disk drive is horizontally mounted. This apparatus overcomes problems caused by friction and the weight of the objective lens.

REFERENCES:
patent: 4286147 (1981-08-01), Tsuboi et al.
patent: 4544837 (1985-10-01), Tanaka et al.
patent: 4634853 (1987-01-01), Kanamaru
patent: 4773052 (1988-09-01), Sugiura et al.
patent: 4819220 (1989-04-01), Miyazaki et al.
patent: 4823330 (1989-04-01), Arter et al.

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