| 摘要 |
PROBLEM TO BE SOLVED: To simultaneously detect a deviation of a position in a main scanning direction, a position deviation in a subscanning direction, a tilted scanning line on a scanned plane, a tilt of the main scanning direction in a rotating direction, out of focus, and a degree of deviation in gradient in a state of out of focus (degree of freedom) that are required quantities to be detected in the alignment of an optical unit. SOLUTION: The method detects each position of each cross point between a read scanning line and each line segment of an adjustment mark 12 and an output level at each cross point based on a characteristic between each pixel position and its output level obtained by reading one line of the adjustment mark 12 placed at a prescribed position, compares the values with prescribed values and detects a deviation of a position in a main scanning direction, a position deviation in a subscanning direction, a tiled scanning line on a scanned plane, a tilt of the main scanning direction in a rotating direction, out of focus, and a gradient in a state of out of focus that are the values on the read scanning line.
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