a deviation of an optic axis of a laser projector is detected , and the deviation is corrected . laser projector &# 39 ; s cpu executes : commanding a laser beam source of one color , out of laser beam sources of three colors , to emit a laser beam ; shutting off the laser when sensing that the laser beam is received in a light - receiving region ; applying a laser of a color to be detected as to the presence or absence of a deviation of the axis until its reception in the light - receiving region is sensed ; keeping time starting when light reception in the light - receiving region is sensed and ending when light reception in a light - receiving region adjacent thereto is sensed ; calculating a relative time difference of each of the colors with respect to a reference color ; and correcting a light emission timing of the laser beam source of each of the color , based on the calculated time .