| 摘要 |
PROBLEM TO BE SOLVED: To provide an image reader that recognizes the type of CCDs and properly drives them without the need for changing a peripheral circuit even when the CCDs with different valid pixel numbers are employed. SOLUTION: An upper limit numbers of pixels in a conventionally used linear sensor is 7500, and a CPU 14 sets a clock frequency to a gate array GA 1 so that 7500+αsets of clocks are arranged within a prescribed line period. Then a lamp is lighted and a reference white board is read. Then the GA 1 counts the number of data with a threshold level of 64/255 or more, and when the count is in excess of a content of a register R1 (e.g. 6000), '1' is set to a register R2, and when the count is less than the content of the register R1, '0' is set to the register R2. The CPU reads the content of the register R2, and when the content is '1', the processing is finished at the current setting. When the content is '0', the CPU determines that a currently provided CCD 12 is not a CCD of 7500 pixels and similarly confirms whether or not the CCD is a CCD of 5000 pixels. In this case, the content is reset to a value corresponding to the CCD of 5000 pixels, e.g. 4000 or the like.
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