| 摘要 |
PURPOSE:To control accurately the light outputted from a light source by amplifying differentially the outputs of photoelectric transducing means having photoelectric transducing properties which are in proportional relations with each other and thereby compensating the change in the photoelectric transducing properties due to the ambient temperature. CONSTITUTION:When the oscillation output of a laser 1 is reduced due to the rise in the ambient temperature, differential amplification 7 is performed through addition of the increase DELTAIOAT and DELTAIOBT of dark current to variations DELTAIOA and DELTAIOB due to the reduction of output of the laser, given that the current of photoelectric transducing elements 2A and 2B before the rise in temperature is IOA and IOB respectively, and thus an output V is obtained. When the photoelectric transducing properties of the elements 2A and 2B are equal to each other, DELTAIOAT equals DELTAIOBT and an expression, V=R(IOA-DELTAIOA(1-k) where k is the transmission ratio of an attenuator provided in the photoreceiving part of the element 2B, is obtained. Accordingly, the output of the laser can be returned to a prescribed value only through detection of the change in output of the 1aser 1. This is also applicable to the case of lowering of the ambient temperature. By this constitution, the output of a light source can be controlled accurately irrespective of the change in the ambient temperature. |
