Abstract: An injection current controller 113 is provided to supply a given injection current. A semiconductor laser (LD) 112 receives the injection current from the injection current controller to output a laser beam. An etalon 114 discriminates the wavelength of the laser beam output from the semiconductor laser. A photodetector (PD) 116 is provided to detect the intensity of the output beam from the etalon. An LD temperature controller 117 performs temperature control of LD so as to bring the output of PD to a predetermined value and, when the output of PD becomes the predetermined value, reserves a corresponding temperature of LD and, at the next temperature control start time, initiates temperature control based on a finally reserved temperature of LD.

Abstract: A surveying instrument comprising optical system means having an optical axis to be coincided with an object to be observed, positional deviation detecting means for detecting the deviation of said optical axis with respect to the object and either means for displaying the detection result of said positional deviation detecting means or means for driving said optical system according to the detection results of said positional deviation detecting means so as to bring said axis in coincidence with the object. According to the present invention, an observer can achieve surveying operation over watching the display, and thus easy and accurate operation is possible.