| 摘要 |
PURPOSE:To decrease the flare by a light beam which is reflected by a scanning surface and light incident end face and is made incident again on the scanning surface and to maintain high condensing efficiency with the optical detector which propagates the emitted light or reflected light generated from the scanning surface subjected to main and sub-scanning by a light beam up to the light receiving surface or a photodetector by a light guide having the light incident end face extending along a main scanning line. CONSTITUTION:The point for scanning with the light beam on the scanning surface 1 in a lateral viewing state viewed from the same direction as the main scanning direction of the light beam 3 is designated as O, the arbitrary incident point at the light incident end face 2a of the emitted light 4 as A, the angle formed by a segment OA and the scanning surface 1 as alpha, the angle formed by the progressing direction of the light beam 3 reflected at the point A after the reflection at the point O and the scanning surface 1 as beta, and the angle formed by the normal taken from the scanning surface 1 and the light incident end face 2a as theta. The above-mentioned angles are so set as to attain alpha/2>=beta AND theta>=15 deg..
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