| 摘要 |
PURPOSE:To correct the dispersion between picture elements of an image sensor at a required exposure range for reading a picture efficiently by correcting the dispersion in the characteristic of the image sensor at a low exposure region. CONSTITUTION:An ND filter 18 is arranged between a lens 14 and a line sensor 16 in the direction of arrow removably. The density of the ND filter is selected to obtain a correction signal so that outputs of all picture elements being components of an image sensor are identical to each other at an exposure larger than a minimum value of an exposure range and smaller than a maximum value of the exposure range required for reading a picture. Thus, the photoelectric output characteristic of a picture signal processing unit is adjusted so that an output picture data PD of an effective picture element 16a is coincident at an exposure Y. |
