| 摘要 |
A document image scanner is provided in which a platen is provided with an optical target in the form of a succession of ruling lines provided at one edge thereof. The ruling lines are inclined at an angle relative to a direction of scan of an optical sensor array such that 5% or less coverage change is provided over each pixel on a scanning line of the array. An output signal from scanning each line can be produced as a square wave signal. From the generated signal, the scanning motion may be corrected. A diagnostic tool is also provided for diagnosing scanning motion using at least two of the optical targets.
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