IMAGE READING APPARATUS, IMAGE FORMING APPARATUS, METHOD FOR DETECTING FOREIGN SUBSTANCE, AND CARRIER MEANS

An image reading apparatus includes a light source (210; 310) configured to emit at least light in a first wavelength range and light in a second wavelength range different from the first wavelength range, a background member (240; 270) having different light reflectances in the first wavelength range and the second wavelength range, an imaging device (220; 320), and a foreign substance detection unit (411; 412). The imaging device (220; 320) receives reflected light from the background member (240; 270) irradiated with the light in the first wavelength range, and generates first read information. The imaging device (220; 320) further receives reflected light from the background member (240; 270) irradiated with the light in the second wavelength range, and generates second read information. The foreign substance detection unit (411; 412) detects presence or absence of a first foreign substance, based on a difference in reading level of the first read information generated by the imaging device (220; 320), and detects presence or absence of a second foreign substance, based on a difference in reading level of the second read information generated by the imaging device (220; 320).