DRIVING SYSTEM FOR SEMICONDUCTOR LASER

PURPOSE:To perform a precise self-control of a wavelength of emitting light, by a method wherein a part of laser light, whose wavelength is selected, is detected by a collection element, a driving current for laser is controlled by said detecting output so that a light output is maximized in terms of a given wavelength. CONSTITUTION:A part of radiating light is introduced to a microcomputer 13 through a first photo detector D1 immediately before laser light is radiated from a detector. A laser driving current value I0, bringing a maximum value P1, is stored in a memory circuit 14 of the microcomputer 13. In case laser radiation light, which is displaced in a wavelength, passes a difraction grating G, a light power is reduced to P2. If the light power, brought to P2, is detected by a first photo detector, it is compared with a light power set to P1, and it is immediately decided that irradiating light is displaced in a wavelength. Thus, the microcomputer 13 controls a constant-current power source through a laser driving current to work so that spread of irradiating light is narrowed to the original. This enables to perform a precise self-control of a wavelength of emitting light.