| 摘要 |
PURPOSE:To accurately detect the pitch position of contrast by varying the movement interval (sampling pitch) of photodetector in the optical-axis direction according to optical magnification. CONSTITUTION:A document cassette 102 received in the cassette receiver of a color image reader is irradiated linearly by an aperture type fluorescent lamp which is arranged below, and a transmission color document 120 such as a color reversal film stored in the cassette 102 is clamped by a couple of transparent glass members 122 and 123 for document protection with reflection preventing films. Image light passed through this cassette 102 is inputted to an image forming lens 124 which has a magnification varying function and made incident on a color separation prism 125 at its upper part. Then when the document is read by image sensors 126R, 126G, and 126B through a lens system, the position relation between the lens system and photodetector is set and then at least two of the document 120, lens system, and photodetector are moved by specific pitch each to detect the maximum position of the peak value of the detection signal of the photodetector, thereby performing focusing. |
