Disclosed herein is a laser noise cancel circuit for reducing laser noises
in a reproduction system for an optical disk device including, a
gain-variable amplifying noise cancel circuit for amplifying a monitor
output signal for laser light, a first low-pass filter for extracting low
frequency signal components of a monitor output signal for noise
canceling, a second low-pass filter for extracting low frequency signal
components, a negative return loop circuit for controlling a gain in the
amplifying noise cancel circuit based on the low frequency signal
components of the monitor output signal for noise canceling extracted as
well as on the low frequency signal components of the reproduced high
frequency signal extracted, to determine the low frequency signal
component rate of the monitor output signal for noise canceling as
identical to the low frequency signal component rate of the reproduced
high frequency signal, and an arithmetic circuit for generating the
reproduced high frequency signal with the laser noise components
cancelled by canceling the laser noise components extracted from the
monitor output signal for noise canceling with a low frequency signal
component rate determined as identical to the low frequency signal
component rate of the reproduced high frequency signal with the laser
noise components of the reproduced high frequency signal.