| 摘要 |
PURPOSE:To attain fetch of a correction reference data with high accuracy by applying at least one main scanning to a reference face whose density is uniform while applying defocusing. CONSTITUTION:At least one of a white color reference board 5, an objective lens system 3 and a photosensor 4 is moved in the direction of optical path, the white color reference board 5 is placed at a non-focal point, and a lighting device assembled in a picture input device 2 is used for lighting. A white refer ence data memory 13 and an adder 10 are conducted via a switch circuit 17, the photosensor 4 is used to apply main scanning for one line's content and an output picture signal is inputted to one input terminal of an adder 10 via an A/D converter 9. A data stored in a corresponding storage area is read from the white reference data memory 13, the data are added and a new data is stored newly to the original storage area of the memory 13. The white level reference face is scanned while being in defocusing state, and since the data are averaged, the reference data with high accuracy is obtained with less effect of a foreign material.
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