Optical recording and reproducing device with normalization of servo control signal using switchable automatic gain control circuitry

Claim 1

An apparatus for optical recording and reproducing on an optical disk comprising: an optical system for impinging a laser light recording beam onto said optical disk to record information on said optical disk and impinging a laser light reproducing beam on said optical disk to reproduce information from said optical disk, said laser light recording beam having a higher power than said laser light reproducing beam; a photoelectric device for generating electric signals in response to light from said laser light recording beam and said laser light reproducing beam from a surface of said optical disk; a first circuit means for producing a first signal representing whole light magnitude information of said reflected light in response to said electric signals from said photoelectric device; a second circuit means for producing a second signal representing servo error information of said laser light recording beam and said laser light reproducing beam on said optical disk in response to said electric signal from said photoelectric device; a division circuit comprising: an automatic gain control circuit having a signal input that inputs said first signal and a reference input for producing a gain control voltage, a gain control amplifier having a gain control input and a signal input that inputs said second signal for producing at an output terminal a division output signal, means for coupling said automatic gain control circuit and said gain control amplifier so that said gain control voltage is input to said gain control input of said gain control amplifier, and switching means for changing a dynamic range and a maximum gain of said gain control amplifier in accordance with a change between using said laser light recording beam and said laser light reproducing beam by said optical system; a phase compensation circuit having an input that inputs said division output signal for compensating a phase of said division output signal; and a driving circuit for driving said optical system in response to said compensated division output signal to control servo operation of said optical system.

Claim 2

An apparatus for optical recording and reproducing on an optical disk comprising: an optical system for impinging a laser light recording beam onto said optical disk to record information on said optical disk and impinging a laser light reproducing beam on said optical disk to reproduce information from said optical disk, said laser light recording beam having a higher power than said laser light reproducing beam; a photoelectric device for generating electric signals in response to light from said laser light recording beam and said laser light reproducing beam from a surface of said optical disk; a first circuit means for producing a first signal representing whole light magnitude information of said reflected light in response to said electric signals from said photoelectric device; a second circuit means for producing a second signal representing servo error information of said laser light recording beam and said laser light reproducing beam on said optical disk in response to said electric signal from said photoelectric device; a division circuit comprising: an automatic gain control circuit having a signal input that inputs said first signal and a reference input for producing a gain control voltage, a gain control amplifier having a gain control input and a signal input that inputs said second signal for producing at an output terminal a division output signal, means for coupling said automatic gain control circuit and said gain control amplifier so that said gain control voltage is input to said gain control input of said gain control amplifier, and switching means for changing a dynamic range and a maximum gain of said gain control amplifier in accordance with a change between using said laser light recording beam and said laser light reproducing beam by said optical system; a phase compensation circuit having an input that inputs said division output signal for compensating a phase of said division output signal; and a driving circuit for driving said optical system in response to said compensated division output signal to control servo operation of said optical system.