| 摘要 |
A multi-beam optical scanning apparatus includes a semiconductor laser array slanted relative to a sub-scanning direction and emitting a plurality of optical beams; a coupling lens converting a shape of each optical beam emitted from the semiconductor laser array; and an aperture with an opening having a size of A<SUB>m</SUB>xA<SUB>s</SUB>, arranged after the coupling lens in a direction in which the optical beam progresses, where A<SUB>m </SUB>is a dimension of the opening in a main scanning direction and A<SUB>s </SUB>is a dimension of the opening in the sub-scanning direction. When a length in the main scanning direction of a contour line defined by 1/e<SUP>2 </SUP>strength of a maximum strength of an optical beam at the position of the aperture is L<SUB>m</SUB>, and a length in the sub-scanning direction of the contour line defined by 1/e<SUP>2 </SUP>strength of the maximum strength of the optical beam at the position of the aperture is L<SUB>s</SUB>, the following conditional expressions are satisf
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