| 摘要 |
PURPOSE:To change a format type as desired and to realize good image quality and exposing conditions with a simple mechanism by making variable the scanning speed in the main scanning direction and the auxiliary scanning direction orthogonal thereto according to the spot size in the changed main scanning direction. CONSTITUTION:When a spot size decreases, scanning lines are obstructive to the eye unless the scanning speed in the main scanning direction and the auxiliary scanning direction orthogonal thereto is changed and there is a need for decreasing the feed in the main and auxiliary scanning directions. More specifically, if it is assumed that the spot size S2 is made to 1/2 times as compared to S1 by converting the same with an optical system, the rotating speed of a rotary polyhedral mirror 10 is set at 1/2 times and the auxiliary scanning speed at 1/2 times in this stage. If the spot size decreases, the exposing energy par unit area increases correspondingly and therefore the intensity of the diffracted light beam of an A/O modulator 5 is weakened by decreasing the quantity of the electricity to be inputted to said modulator so that the same exposure is obtd. |
