| 摘要 |
A sensor configuration and signal processing, which are not affected by a paper rise when a print pattern for auto head shading and density correction is read, are provided. A predetermined print pattern is printed with a plurality of heads, and the predetermined pattern that is printed is scanned with a sensor (110) to detect a density unevenness for the print pattern in each color on a nozzle basis. The sensor (110) comprises a light emitting element which emits a light including all light regions, R, G, and B, and a plurality of light receiving elements each of which receives R, G, and B lights, respectively. The plurality of light receiving elements are arranged in a main scanning direction. The print pattern printed by each head is read by the light receiving element for the complementary color light of the pattern and the light receiving element for a non-complementary color light of the pattern, and a change in density level in the nozzle column direction is detected based on the difference between the two outputs.
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