Patent ID: 8229323
Filing Date: 2012-07-24
Classification: G02B,G03G

Abstract:
1. A scanning optical apparatus, comprising: a light source unit including a plurality of light emission portions; a deflection unit for deflecting a plurality of light fluxes for scanning that are emitted from the plurality of light emission portions; an incident optical system which is disposed in an optical path between the light source unit and the deflection unit, and includes a plurality of optical elements disposed for each of the plurality of light fluxes so as to make each of the plurality of light fluxes emitted from the plurality of light emission portions enter a deflection surface of the deflection unit with an oblique angle in a sub scanning section; a plurality of imaging optical systems disposed so as to correspond to the plurality of light fluxes deflected for scanning by the same deflection surface of the deflection unit; and a positional regulation member for holding the plurality of optical elements each having an x reference surface for performing positional regulation of the optical element in an optical axis direction and a z reference surface for performing positional regulation of the optical element in a sub scanning direction, wherein: each of the plurality of imaging optical systems makes each of the plurality of light fluxes deflected for scanning by the deflection surface of the deflection unit form an image on a surface to be scanned; the plurality of optical elements are formed integrally; the plurality of light fluxes outgo from the plurality of optical elements with different angles in the sub scanning section; each of principal rays of the plurality of light fluxes emitted from the plurality of light emission portions is parallel to an optical axis of each of the plurality of optical elements in the sub scanning section; each of the plurality of optical elements is held by a casing so that the x reference surface and the z reference surface of each of the plurality of optical elements contact with the positional regulation member; and when an angle between a normal of the x reference surface and each of the principal rays of the plurality of light fluxes outgoing from the plurality of optical elements in the sub scanning section is denoted by θ, an angle between the principal ray having a smallest value of θ among the plurality of light fluxes outgoing from the plurality of optical elements and a normal of the deflection surface in the sub scanning section is denoted by α, a light flux diameter of the light flux entering an incident surface of the optical element in the sub scanning section is denoted by D, and an optical path length from the incident surface of the optical element to the deflection surface is denoted by L, with regard to the principal ray of at least one light flux of the plurality of light fluxes outgoing from the plurality of optical elements, the following conditional equation is satisfied and with regard to the angle α between the light flux outgoing from the optical element and the normal of the deflection surface in the sub scanning section, the following conditional equation is satisfied