| 摘要 |
PURPOSE:To achieve a reduction of the distortion of a semiconductor laser by inverting a difference between a detected signal and an input signal and adding the inverted difference to the input signal. CONSTITUTION:A light beam emitted from one side surface of a semiconductor laser 110 is detected by a photodiode 122, and the detected beam is then inverted and amplified by an inverting amplifier 124. This beam is outputted as a detected signal D. An input signal S is outputted after its delay time and level have been adjusted in a delay element 312 in such a way that there is no time difference between an opposite phase component of the detected signal D and the input signal. The input signal S and the detected signal D are added to each other by means of a waveform adder 134, and then distortion components are outputted. The level of the components thus outputted is made constant by an attenuator 136 and a level detecting circuit 138, and the components are added to the input signal S by a waveform adding circuit 139. Therefore, a feedback loop is established so as to cancel the distortion components of a laser beam, so that the distortion components of the laser beam are reduced. The amount of a feedback is controlled by the magnitude of distortion components delivered from an AGC circuit, whereby it is possible to reduce the distortion of a laser beam in a superior manner. |
