Image reading apparatus and image forming apparatus having inclined planar shape of background member to improve sheet shadow detection accuracy

Abstract

An image reading apparatus includes a conveyance member, a transparent member, a background member, and a reading unit. The reading unit arranged on an opposite side to the background member with respect to the transparent member. The reading unit includes a light source and a reading sensor. The light source emits light toward a sheet. The reading sensor reads a shadow of a sheet and an image of the sheet through the transparent member. The shadow of the sheet is projected onto the background member. As viewed in a width direction perpendicular to a conveyance direction, an irradiating direction of the light inclines downstream in the conveyance direction toward a downstream side in the irradiating direction. The background member has a planar shape that is inclined to approach the transparent member from an upstream side toward a downstream side in the conveyance direction.