| US 7,526,006 B2 | ||
| Laser power control circuit | ||
| Minoru Ochiai, Kyoto (Japan); and Yoshihiro Kanda, Osaka (Japan) | ||
| Assigned to Panasonic Corporation, Osaka (Japan) | ||
| Filed on Sep. 06, 2006, as Appl. No. 11/515,745. | ||
| Application 11/515745 is a division of application No. 10/853131, filed on May 26, 2004, abandoned. | ||
| Claims priority of application No. 2003-148328 (JP), filed on May 26, 2003. | ||
| Prior Publication US 2007/0002912 A1, Jan. 04, 2007 | ||
| Int. Cl. H01S 3/00 (2006.01) | ||
| U.S. Cl. 372—33 [372/38.1; 372/38.01; 372/38.02; 372/38.04; 372/38.07; 372/38.09] | 5 Claims |
| 1. A laser power control circuit for obtaining a constant laser power by performing negative feedback so that a photoelectric-converted
voltage which is obtained by photoelectric-converting a portion of light emitted from a semiconductor laser becomes equal
to a reference voltage, said laser power control circuit including:
a variable voltage supply connected to the reference voltage;
a first switch that selectively outputs either the reference voltage or the photoelectric-converted voltage;
a differential amplifier having two input terminals, a first one of the input terminals being connected to the variable voltage
supply, and a second one of the input terminals being connected to the first switch;
a second switch that selects whether an output of the differential amplifier is transmitted to a laser driving circuit or
not;
a selector that receives the reference voltage and an output voltage from the differential amplifier, and selects one of the
reference voltage and the output voltage from the differential amplifier; and
an A/D converter that receives from the selector the selected one of the reference voltage and the output voltage from the
differential amplifier, and converts the selected one of the reference voltage and the output voltage from the differential
amplifier into a digital signal.
|