| 摘要 |
PURPOSE:To reduce a subscan-directional irregularity in spot shape due to distortion by providing a slit stop which is long in a main scanning direction and limits light other than light of the '0'th order. CONSTITUTION:A slit aperture A which is placed between a polygon mirror 9 and a recording film 11 has its slit width set so that the light of '0'th order is passed and light of high order is limited, and the aperture is arranged about a scan as a center. When this slit A is formed in an arcuate shape almost about the point where laser light 2 crosses the center part of the polygon mirror 9 almost as the center, the width of the aperture corresponding to each angle of visibility can be made constant. This slit is shown by A'. For the purpose, the slit aperture A which passes only the light of the '0'th order and limits light of high order in general is set as shown in a figure to remove the influence of diffracted light of high order although the light of the '0'th order can not be constant in intensity. |
