| 摘要 |
PROBLEM TO BE SOLVED: To suppress production of a pseudo contour by using a simple means where the circuitry requires no large scale and is not made complicated. SOLUTION: An image signal read by a CCD is analog/digital converted into digital data with N+n (8 in this case) bit gradation, and the result is given to a data line replacement circuit in Figure 3. The 6th bit (Data 2) from the high-order of input data in 8 bits and the LSB (Data 0) can be replaced with each other to provide an output of data (Data 7, 6, 5, 4, 3', 2') with N (6) bit gradation. By controlling a signal given to an enable terminal of a buffer IC (3) 43 where the 5th bit (Data 2) from the high-order of the input data in 8 bits are replaced with the LSB (Data 0) and to an enable terminal of a buffer IC (2) 42 where no replacement takes place, a usual/replacement mode, that is, either of the buffer ICs (2), (3) is selected and an inverter 44 is provided for the purpose. The usual mode is selected when a reference white board is read. The replacement mode is selected when an original is read and a pseudo contour is suppressed by superimposing a noise of the Data0 on the Data2'.
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