| 摘要 |
PURPOSE:To enable to obtain a good output even with the title diode whose threshold current and differential quantum efficiency both vary by controlling the pulse current by means of a temperature detecting circuit and controlling it under a specific temperature so that this current becomes constant. CONSTITUTION:A photo diode 4 receives the laser light of a laser diode 3, inputs the output of said diode 4 to a bias control circuit 5, varies the bias value of the output of a bias circuit 6, and controls the output of the diode 3. The outer temperature is detected by means of the temperature detecting circuit 7; when the temperature increases, the degree of amplification of a current amplifying circuit 2A is made large. Thereby, control is performed to the direction for the gradient of the current-photo output characteristic of the diode 3. Here, in the case of using the laser diode whose threshold current and differential quantum efficiency both vary with temperatures, said efficiency gradually decreases, when the temperature exceeds 25 deg.C. Therefore, the degree of amplification of the circuit 2A is kept constant by a clamping circuit 8 at less than 25 deg.C by means of the output of the circuit 7; contrarily, when the temperature exceeds 25 deg.C, the degree of amplification of the circuit 2A is controlled by means of the output of the circuit 7. |
