| 摘要 |
PROBLEM TO BE SOLVED: To attain high gradation by devising the reader to process image data in bit number, providing a higher degree than a current 8-bit gradation number without increasing the cost much. SOLUTION: The reader is provided with a black reference data arithmetic means that obtains high degree 10-bit black reference data from an 8-bit A/D converter 21 A/D-converting data from a plurality of black reference photoelectric conversion elements provided in an image sensor, a black reference data memory 23 that stores the 10-bit black reference data obtained from the black reference data arithmetic means, an image data integral multiple means 24 that applies a four times image data to the image data outputted from the image sensor and A/D-converted to match the bit number with that of the black reference data, an arithmetic means 25 that subtracts the 10-bit black reference data from the 10-bit image data, and a black level correction circuit 22 that provides an output of image data which has been subjected to black level correction. |
