Patent ID: 6462866
Filing Date: 2002-10-08
Classification: G02B,H04N

Abstract:
An image reading apparatus comprising:a light source for illuminating an original image; an imaging optical system for forming an image of the illuminated original image on the focal plane of the system; a sensor unit arranged in front of said focal plane; an A/D converter for converting the output signal of said sensor unit into an n-bit digital signal; and an infrared cut filter unit arranged on the optical path between the light source and the sensor unit, said infrared cut filter having a wavelength zone satisfying the relationship as expressed by the formula below: T&lE;100(2**n), where T is the transmittivity of said infrared cut filter, ** indicates exponentiation, and n is the number of bits of the digital signal, said infrared cut filter unit including at least two infrared cut filters arranged on the optical path between the light source and the sensor unit, said infrared cut filters showing respective spectral characteristics that are different from each other.