Patent ID: 7372796
Filing Date: 2008-05-13
Classification: G11B

Abstract:
1. An apparatus for controlling a monitor photo diode, which monitors an optical signal output from a laser diode for writing data on or reading data from a disk, the apparatus comprising: a comparator which compares a voltage signal corresponding to a detected optical power output from the laser diode with a predetermined reference voltage signal; a medium gain selector which selectively issues a first gain selected from a first plurality of gains to the comparator depending on a type of the disk; and an operation gain selector which selectively issues a second gain selected from a plurality of output gains to the comparator depending on a type of the optical signal output from the laser diode so as to issue a monitoring signal according to the issued first and second gains for use in controlling the laser diode, the output gains being multiplied by the output of the medium gain selector.