Patent ID: 7239433

Claim:
An image reading apparatus comprising: a timing adjusting circuit which adjusts a generation timing of a drive signal for driving at least an image pickup element which reads an object image and outputs an image signal of the object image; a memory circuit which stores an adjustment value of the generation timing of the drive signal adjusted by said timing adjusting circuit; a drive signal generating circuit which generates the drive signal in accordance with the adjustment value stored in said memory circuit; a pixel sampling circuit which samples the image signal a plurality of times in one image pickup element; a changing rate detection circuit which calculates a changing rate of image signals sampled at adjacent sampling timings, from the image signals sampled by said pixel sampling circuit; and a discrimination circuit which judges whether the image signal is normal or not in accordance with the changing rate of the image signal calculated by said changing rate detection circuit, wherein in a case that said discrimination circuit judges that the image signal is abnormal, said timing adjusting circuit adjusts the generation timing of the drive signal.