Patent ID: 7359099

Claim:
An image reading device comprising: a photoelectric device including a plurality of pixels and provided with an empty transfer part, the empty transfer part outputting an empty transfer level corresponding to black dummy pixels which are always shaded and are not used for reading an image; an A-D converter performing A-D conversion on an output signal for each pixel of said photoelectric device; a reference voltage varying part varying a reference voltage of said A-D converter to vary between first, second, and third reference voltages based on a current mode of an image scanner, the first reference voltage selected for a background removal function, and one of the second and third reference voltages being selected when the background removal function is not used; a detecting part detecting a black correction reference data from an output signal for each pixel of said photoelectric device; a black shading correcting part subtracting the black correction reference data from digital image data obtained from the output signal for each pixel of said photoelectric device when an image is read, through said A-D converter having the reference voltage set therein; and a correcting part correcting the black correction reference data by a ratio between a first digital black level value obtained from an output voltage level of said empty transfer part obtained through said A-D converter when the black correction reference data is detected and a second digital black level value obtained from an output voltage level of said empty transfer part obtained through said A-D converter when the image is read.