| 摘要 |
PROBLEM TO BE SOLVED: To provide a scanning optical device with which sufficient aberration correction is attained by itself. SOLUTION: A scanning optical device 40 for converging scanning light reflected by a polygon mirror 50 is formed of a light-transmitting member. The scanning light is transmitted through a first surface 41, reflected by a second surface 42, transmitted through the first surface 41 and emitted. The first and second surfaces possess, on a reference axis, an intersection with first and second reference planes both of which are perpendicular to a single reference axis. The first surface is an optical curved surface coming into contact with the first reference plane at the intersection with the reference axis, and the amount of sagging of the second surface from the second reference plane is defined by a polynomial, in which two-dimensional coordinates in the main scanning direction lie within the second reference plane and a subscanning direction perpendicular to it is set as a variable by taking the intersection with the reference axis as an origin. The coefficients of the polynomial by which the second surface is defined have a value other than zero, with respect to terms including only the first order component of the coordinates in the subscanning direction.
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