| US 7,499,478 B2 | ||
| Laser driver, optical disk apparatus using the same, and laser control method | ||
| Makoto Nihei, Hitachinaka (Japan); Toshimitsu Kaku, Sagamihara (Japan); Akihiro Asada, Chigasaki (Japan); and Takashi Hoshino, Yokohama (Japan) | ||
| Assigned to Hitachi, Ltd., Tokyo (Japan); and Hitachi-LG Data Storage, Inc., Tokyo (Japan) | ||
| Filed on Sep. 09, 2004, as Appl. No. 10/937,908. | ||
| Application 10/937908 is a continuation of application No. 09/943860, filed on Aug. 30, 2001, granted, now 6,810,050. | ||
| Claims priority of application No. 2001-158105 (JP), filed on May 28, 2001. | ||
| Prior Publication US 2005/0030989 A1, Feb. 10, 2005 | ||
| This patent is subject to a terminal disclaimer. | ||
| Int. Cl. H01S 3/13 (2006.01) | ||
| U.S. Cl. 372—29.015 [372/33; 372/38.1; 372/38.01; 372/38.02; 372/38.07] | 3 Claims |
| 1. 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.
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