A scanning projection apparatus for displaying image comprises a light source for generating a light beam, a beam scanner which deflects the light beam to project a two dimensional image field, a modulation means for modulating the intensity of the light beam, and a sensor to detect the scanned light beam. The light source may consist of a plurality of semiconductor lasers and/or solid state lasers to generate light beams with wavelengths of red, green and blue colors aligned into a single light path. The image field is divided into an active image field for displaying image and a dark field in the perimeter of the image field wherein the light beam is switched off to reduce inherent image defects. The sensor is positioned outside the active image field to detect a scan line once per image frame to eliminate image distortion due to phase difference between the actual and the predicted positions of the scanned beam, and to detect both the horizontal and the vertical scanning operations of the beam scanner for safety precaution.