| 摘要 |
PURPOSE:To prevent ruggedness from being generated at a boundary part of a line in a main scanning direction, by detecting the width in the sub-scanning direction of a light-emitting region so that the optical power level at an end part of the light-emitting region of each LED element is not lower than a specified percentage of that at an end part on the electrode leading-out side. CONSTITUTION:The width in the sub-scanning directin of a light-emitting region is so determined that the optical power level LD at the end part on the side opposite to the electrode leading-out side is not lower than 70% of the optical power level LC at the end part on the electrode leading-out side, both in an optical power distribution curve (solid line) for odd-numbered LED elements 2 (a', c', e'...) and in that (broken line) for even-numbered LED elements 2 (b', d', f'...). Accordingly, the stagger between recording positions of adjacent picture elements in the sub-scanning direction is markedly reduced, and the ruggedness generated at the boundary part of a line in the main scanning direction is reduced to such a level as to be visually negligible. |
