A transmission light source unit includes a first light source portion including: a first light source; and a first light guide that shapes light emitted by the first light source into a line and emits the light toward a conveyance path of a paper sheet. An image sensor unit includes: a second light source portion that emits light toward the conveyance path of the paper sheet; and an image sensor that detects the light emitted by the first light source portion and transmitted through the paper sheet and the light emitted by the second light source portion and reflected by the paper sheet. A first light diffusing surface of the first light guide is provided with at least one of concave portions and convex portions including inclined surfaces and inclined relative to a normal line of the first light emission surface.

An illumination apparatus includes: a light source; a rod-like light guide having an incident surface that enters light from the light source that is disposed on one side in a main-scan direction, a diffusing surface that diffuses light that enters from the incident surface, and an emission surface that linearly emits light towards a bill; and a reflection member having a reflection surface that reflects light diffused by the diffusing surface to the light guide. The light guide has a locking projection that is locked in the reflection member on one side in the main-scan direction. The reflection member has a locking hole in which the locking projection is locked. A cut-out portion at which one part is cut out is formed in the locking hole.

A light guide includes a plurality of boss portions. A round hole portion is provided near the center of a base member for fixing the light guide, and slit portions are provided on both ends thereof. The round hole portion supports one boss portion in both the longitudinal direction and the lateral direction of the light guide. The slit portions support boss portions in the lateral direction of the light guide, but are free in the longitudinal direction of the light guide. That is, the center of the light guide is fixed from both directions, and thus both ends of the light guides can expand away in the longitudinal direction. This cuts the influence of expansion by half.

In an image sensor unit, a frame includes a light blocking portion that protrudes toward one surface of a circuit board at a position between a light source and an image sensor. On the one surface of the circuit board, a conductive portion that continuously overlaps with external lines of the light blocking portion in a sub-scan direction in a view of the circuit board in a direction orthogonal to the one surface is formed.

A light guide includes an incidence surface configured to allow light from a light emitting unit to enter the light guide, a light guide portion configured to propagate the light entering via the incidence surface, a reflection portion configured to reflect the propagated light, an exit surface configured to allow light reflected on the reflection portion to exit, and a protrusion portion configured to position the light guide, wherein the protrusion portion is provided downstream of the reflection portion.

A photoelectric conversion device includes a current consumption circuit configured to consume current such that a difference between a current consumption during a blanking period and a current consumption during a standby period is reduced.

Reference portions are arranged in a reference area outside a main area in a main scanning direction, each having a lower surface of one of a plurality of determination colors. A reference data offset value is set based on reference pixel data of the reference area obtained when a light emitting unit of a scanning unit is not caused to emit light. A color determination process is executed to correct the reference pixel data in line image data obtained when the light emitting portion is caused to emit light with the reference data offset value, and to determine which determination color the corrected reference pixel data is data of. A unit drive device executes driving operations that are sequentially selected from a plurality of trial driving operations according to the determination result of the color determination process, and positions the scanning unit at a home position.