Patent ID: 6816623
Filing Date: 2004-11-09
Classification: H04N

Abstract:
An image reading apparatus comprising:a light source for illuminating an original; a white member which is illuminated by light emitted from said light source; a photoelectric converting element for receiving reflection light from the original and from said white member, and for providing an output image signal; shading compensating means for compensating the output image signal on the basis of light received by said photoelectric converting element from said white member; and; control means for controlling a timing during which said photoelectric converting element reads said white member, said timing being based on an elapsed time from a start of illumination of said light source and on a size of the original in a longitudinal direction of the light source, wherein the shorter the elapsed time from the start of illumination of said light source, the greater a frequency of reading said white member, and the larger the size of the original in the longitudinal direction of said light source, the greater the frequency of reading said white member.