| 摘要 |
PURPOSE:To eliminate need for an exclusive device and to decrease the write time by storing a pattern whose shading is corrected by the data of a white original read in a picture reader into an EEPROM, subtracting the content by the read value so as to apply shading correction. CONSTITUTION:A read value of white original is fed to a sample-and-hold circuit 4 and converted by an A/D converter 5. The value is stored in a RAM 3 according to a write address 8 and a write timing 9 formed based on a clock 12 from an address generating circuit in a timing generating circuit 7 and a digital value corresponding to each bit for one line in the main scanning direction is written in the RAM 3. A microprocessor 1 reads the data of the RAM 3, converts it into a shading correction value and the result is stored in the EEPROM 2. Thus, the shading correction pattern is obtained corresponding to each bit for one line in the main scanning direction from the EEPROM 2.
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