| US 7,573,922 B2 | ||
| Semiconductor laser driving unit and image forming apparatus having the same | ||
| Tomohiko Kamatani, Hyogo (Japan); and Hiroaki Kyogoku, Hyogo (Japan) | ||
| Assigned to Ricoh Company, Ltd., Tokyo (Japan) | ||
| Filed on Aug. 31, 2006, as Appl. No. 11/515,151. | ||
| Claims priority of application No. 2005-255324 (JP), filed on Sep. 02, 2005. | ||
| Prior Publication US 2007/0053395 A1, Mar. 08, 2007 | ||
| Int. Cl. H01S 3/00 (2006.01) | ||
| U.S. Cl. 372—38.01 [372/38.02; 372/38.07] | 12 Claims |
| 1. A semiconductor laser driving unit controlling driving of a semiconductor laser by performing automatic power control to
automatically control a current to be supplied to the semiconductor laser so that a desired amount of light emission is obtained,
the semiconductor laser driving unit comprising:
a bias current generator circuit part configured to generate a predetermined bias current lower than an oscillation threshold
current of the semiconductor laser and constantly output the generated bias current to the semiconductor laser;
a switching current generator circuit part configured to generate a first current for causing the semiconductor laser to emit
light, and to output the generated first current to the semiconductor laser in accordance with a control signal input to the
switching current generator circuit part;
an initialization circuit part configured to perform a predetermined initialization operation to detect a light emission characteristic
of the semiconductor laser, and to cause the switching current generator circuit part to generate a second current of a value
obtained from the detected light emission characteristic; and
an offset current setting circuit part configured to cause the switching current generator circuit part to generate the first
current in which a set offset current is added to the second current,
wherein the bias current generator circuit part detects an amount of light emission of the semiconductor laser, and generates
and outputs the bias current so that the amount of light emission of the semiconductor laser produced by a sum of the generated
bias current and the first current output from the switching current generator circuit part is a predetermined value.
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