an optical information processing apparatus includes a light source for radiating a light beam onto an optical information recording medium . a first photosensor is provided for partially receiving the light beam emitted from the light source and generating an output , and a second photosensor is provided for receiving either a light beam reflected by the recording medium or a light beam transmitted through the recording medium and generating an output . a control circuit controls power of the light beam emitted from the light source using the output from the first photosensor , and a correction circuit automatically corrects linearity of the output of the first photosensor with respect to the power of the light beam emitted from the light source in accordance with the output from the second photosensor .