Image sensor unit, image reading apparatus, image forming apparatus, and paper sheet distinguishing apparatus

An image sensor unit (60) includes: a light source part (25) that emits at least ultraviolet light in a main-scan direction to an object to be illuminated; a light condenser (32) that focuses light from the object to be illuminated; an image sensor (75) that converts the light focused by the light condenser (32), into an electric signal; and an ultraviolet cut part (65) that is disposed between the object to be illuminated and the image sensor (75), cuts off ultraviolet light in light reflected by the object to be illuminated, and allows fluorescent light to transmit therethrough. The image sensor (75) includes an ultraviolet detection part (77) that detects light in the ultraviolet light emitted from the light source part (25), the detected light having been reflected by a reflecting part but having not transmitted through the ultraviolet cut part (65).