| 摘要 |
PURPOSE:To enlarge an operating temperature range by a method wherein a discriminating circuit which discriminates whether a temperature detected by a thermosensor is within a specified temperature range or not is provided and a feedback circuit which stabilizes an output light or a feedback circuit which controls the temperature with an endothermic heater in accordance with the output of the discriminating circuit is provided. CONSTITUTION:When an ambient temperature Ta drops below a lower limit T1=0 deg.C, a discriminating circuit 20 supplies a current to an endothermic heater 19 so as to make the resistance of a thermistor 18 on the endothermic heater 19 30 kOMEGA to heat a semiconductor laser 10. To the contrary, when the ambient temperature Ta exceeds an upper limit T2=60 deg.C, the discriminating circuit 20 supplies a reverse direction current to the endothermic heater 19 so as to make the resistance of the thermistor 18 3 kOMEGA to cool the semiconductor laser 10. When the ambient temperature Ta is between 0 deg.C and 60 deg.C, no current is supplied to the endothermic heater 19 and a light output is stabilized by a feedback circuit 17 only. With this constitution, an operating temperature range can be enlarged and, moreover, the increase of a power consumption can be halved. |
