Optical scanning device, image reading device provided with this, image forming device, and photographing device

Abstract

An image reading device comprising a rotary polygon mirror () for scanning a light flux from a light source (), an imaging optical system () for forming on a reflection plane of the mirror () a linear image larger than the width in a main scanning direction of the one reflection plane, and a curved-face mirror (), wherein the light source (), the imaging optical system (), the rotary polygon mirror () and the curved-face mirror () are disposed in different positions in a sub-scanning direction, a light flux from the imaging optical system () shines obliquely onto the polygon mirror (), and a light flux reflected off the mirror () beams obliquely onto the curved-face mirror (). Since one curved-face mirror can beam a light flux reflected from the rotary polygon mirror onto a surface to be scanned and the rotary polygon mirror having a small inscribed radius and many reflection planes can be used, satisfactory optical performance and high-speed feature can be realized.