Importance

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Abstract

An image reading apparatus with a plurality of line sensors comprises a reference level adjusting circuit for adjusting a level of a dark output outputted from one of the line sensors to a reference level, and a level difference adjusting circuit for progressively adjusting to a minimum a dark output level difference between the reference level adjusted line sensor and a second line sensor adjacent to the former sensor, a dark output level difference between the second line sensor and a third line sensor adjacent to the second line sensor, and so on. When three or more line sensors are used, a level of a dark output outputted from one of the three line sensors which is located at the center of a sensor array of the three sensors is adjusted to the reference level. Alternatively, a level of a dark output outputted from one of three line sensors which is located at one of the ends of a sensor array of the three line sensors is adjusted to the reference level. With such an arrangement, even when a linear array of a plurality of line sensors is used, the resultant image is free from lines and stripes or density irregularity, because the level differences at the channel boundary levels are adjusted to be zeroed.

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First Claim