Patent ID: 6979809

Claim:
An image reading apparatus having a first mode for high resolution reading and a second mode for high gradation reading, said apparatus comprising: a light source adapted to apply light to an original image; a movable reading unit adapted to convert reflected light of said light source applied to the original image into a voltage; a moving unit adapted to move a reading position of said reading unit at a speed which is the same for the first mode for high resolution reading and the second mode for high gradation reading; a generator adapted to generate a driving signal for said reading unit, said signal having patterns which are varied in accordance with said reading modes, wherein a frequency of the driving signal in the second mode for high gradation reading is lower than a frequency of the driving signal in the first mode for high resolution reading, and an accumulation time of each of pixels of the driving signal in the second mode for high gradation reading is longer than an accumulation time of each of pixels of the driving signal the driving signal in the first mode for high resolution reading; and a converter adapted to convert analog signals from said reading unit to a digital signal having a plurality of numbers of bits, wherein a number of bits in the second mode for high gradation reading is higher than a number of bits in the first mode for high resolution reading.