Focus servo device of a system for reading out recorded informat

Details Focus servo device of a system for reading out recorded informat Focus servo device of a system for reading out recorded informat

1983-07-22

1987-01-13

Psitos, Aristotelis M.

Dynamic information storage or retrieval

Control of storage or retrieval operation by a control...

Mechanism control by the control signal

250201, G11B 708, G11J 120

Patent

active

046370056

ABSTRACT:
In a system for optically reading out information recorded on a recording medium, the focus servo device includes an object lens supported by a resilient support member and a focus servo loop. The focus loop includes a driving current generating means for generating a driving current of a cylindrical coil of a focus actuator connected to the object lens in accordance with an output signal of a pickup means which includes the object lens. The improvement is that the dc loop gain of the focus servo loop is substantially raised to infinity, so as to reduce the magnitude of the focus error signal which is required to produce the driving current of the cylindrical lens for moving the object lens against the resilient force of the support member. Further, the focus servo device is characterized by a phase retarding circuit for reducing the amount of the phase rotation at the higher frequency range so as to assure the stability of the operation of the focus servo loop.

REFERENCES:
patent: 4286147 (1981-08-01), Tsuboi et al.
patent: 4446546 (1984-05-01), Miller
patent: 4475182 (1984-10-01), Hosaka
patent: 4497047 (1985-01-01), Fujiie et al.

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