| 摘要 |
PURPOSE:To prevent a photodetecting range from deviation by dividing an optical beam projected from an optional angle around a projection point to a rotary polygon mirror with equal angles and arranging the rotation center axis core of the rotary polygon mirror on a position allowing a complete light part to have uniform length. CONSTITUTION:A point intersecting the minimum necessary quantity 10 of reflected light with the position of the rotary polygon mirror 1 is a position 11 and the reflecting position is A'. A position having the same quantity as the quantity 10 of light by changing a surface 1a in accordance with the rotation of the rotary polygon mirror 1 is B' and the reflecting position is B'. Namely, the reflected light 4 and 6 of the optical beam at the positions A' and B' are uniform and the length LA' of the complete light part is equal to the length LB'. Thus, one end 7 and the other end 8 of the one surface 1a of the rotary polygon mirror 1 are determined in accordance with the necessary light 10 and the intersecting point of lines extended from respective end surfaces 7, 8 to the center is determined as the axial core 9 in accordance with the interior angle 12 corresponding to the number of surfaces of the polygon. |
