Scanning optical system and light emission and reception apparatus

For a wide range of measurement object to provide a scanning optical system and the radar can obtain reflected light of sufficient intensity. The light beam emitted from the light source, since is reflected twice by the first mirror surface and a second mirror surface, the change in the rotation angle of the spot light is possible hardly projection generated in the scanning range. Thus, a plurality of spot light reflected by the second mirror surface, irrespective of the position in the main scanning direction, since the aligned state along a direction intersecting the main scanning direction in the object side can be maintained, the measured leakage can be projected light for a wide range of objects in and while one scan suppressed.