| 摘要 |
This invention reads image data of a subject by performing pre-reading operation while changing the image reading sensitivity at a plurality of stages immediately before the start of normal reading operation of a subject image, calculates the absolute difference value between adjacent pixels of lightness data of the read image data, and sets as an optimal reading sensitivity an image reading sensitivity having a maximum absolute difference value among calculated absolute difference values in a photosensor system having a photosensor array constituted by two-dimensionally arraying a plurality of photosensors, a driver circuit for supplying a drive signal to the photosensors, and a controller for controlling reading operation of a subject image and sensitivity setting. Even when ambient light changes or the characteristics of the photosensor change, an optimal image reading sensitivity can be set in accordance with the changes. Further, even when a position where the subject is placed in the detection area of the photosensor array offsets from a normal position in performing pre-reading operation, and the read image data contains a background pattern together with the subject image, a proper image reading sensitivity can be extracted and set without any influence of the background pattern. An image reading sensitivity setting method having high reliability can be provided. |
