| 摘要 |
PURPOSE:To allow the displaying of a high-quality image by changing the incident angle of a laser beam for drawing to a rotary polygonal mirror according to the division angle of the respective plane mirrors of the rotary polygonal mirror so that the horizontal scanning by the laser beam for drawing is kept always constant. CONSTITUTION:A laser beam lr for reference is made incident to the plane mirror corresponding to the period before one horizontal period of the plane mirror to which the laser beam li for drawing is made incident among the plane mirrors of the rotary polygonal mirror 1 and the reflected laser beam lr is detected by a two divided light detector 17 to obtain the signal correspond ing to the division angle of the plane mirror so that the incident angle of the laser beam li for drawing to the rotary polygonal mirror 1 can be changed by an acoustooptical element 5 according to the signal obtd. by delaying the above-mentioned signal by one horizontal period. The horizontal scanning by the reflected laser beam lo from the polyhedral mirror 1 is kept constant at all times in this way in spite of the fluctuation in the division angles of the respective plane mirrors of the rotary polygonal mirror 1. The high-quality images are thus displayed. |
