Patent ID: 7499478

Claim:
An optical disk apparatus comprising: a semiconductor laser which emits a laser beam onto an optical disk; a semiconductor laser driver which produces a high frequency current and drives said semiconductor laser with a current, with the high-frequency current being superimposed thereon, and measures the frequency of said high-frequency current, wherein said laser driver includes: a semiconductor laser drive circuit which feeds a DC current to said semiconductor laser; a high frequency superimposing oscillator which produces a high-frequency current to be superimposed on the output current of said semiconductor laser drive circuit; and a frequency measuring circuit which measures the frequency of the high-frequency current produced by said high frequency superimposing oscillator and outputs the measured frequency to said main controller, wherein said frequency measuring circuit includes: a binary digitizing circuit which converts the high-frequency current into a digital signal; a frequency demultiplying circuit which implements the frequency demultiplication for the digital signal to produce the high frequency superimposition monitor signal; and a frequency counter which counts the frequency of the high-frequency of the high-frequency current based on a reference clock signal supplied from the outside of said laser driver and the high frequency superimposition monitor signal; a main controller which controls the frequency of said high-frequency current produced by said semiconductor laser driver by using the frequency measured by said semiconductor laser driver, wherein said main controller controls the frequency of said high-frequency current within valid frequency range of a regulation; and a register which holds the value of frequency measured by said frequency measuring circuit.