OPTICAL SCANNER AND IMAGE FORMING APPARATUS

PROBLEM TO BE SOLVED: To provide an optical scanner which can reduce the influence on an image forming spot diameter on a surface to be scanned due to arrangement errors of a plurality of anamorphic elements and the influence on intervals of scanning lines to be formed, and which can suppress deterioration of image quality incidental to change in temperature, and to provide an image forming apparatus equipped with the optical scanner. SOLUTION: The optical scanner 1 includes: a light source 1; a pre-optical-deflection-means optical system for guiding a luminous flux from the light source 1 to an optical deflection means; an optical deflection means 6 for deflection-scanning the luminous flux; and a scanning optical system 27 for imaging, on a surface to be scanned, the luminous flux deflection-scanned by the optical deflection means 6. The pre-optical-deflection-means optical system includes: a first optical element having a negative power in a deflection scanning vertical direction; a second optical element having power only in a deflection scanning direction; and a third optical element having power only in a deflection scanning vertical direction. In the second optical element and the scanning optical system, the absolute value of the power in the deflection scanning direction satisfies ¾ m2¾