| 摘要 |
PROBLEM TO BE SOLVED: To provide an image forming apparatus which can form an image with a constantly normal printing quality by detecting a stain in linear scale before the stain affects the printing quality, so as to enable a user to perform cleaning, replacement, etc. SOLUTION: An optical sensor 38 is switched to a normal sensitivity and carried to the left, and next switched to a sensitivity lower than the normal sensitivity and carried to the right at a low speed, so as to be stopped in a reference position. A difference with respect to an initial value 0 in the reference position is computed by reciprocating a carriage 52. When the computed difference exceeds a predetermined valueα, it is determined that the linear scale 50 may be stained heavily enough to disable the normal printing operation in the near future, and an alarm message is displayed on a display device. When the difference is equal to/smaller than the predetermined valueα, it is determined that the stain do not adhere to the linear scale 50 or that the stain adhering to the linear scale falls within an allowable range, and the alarm message is not displayed. COPYRIGHT: (C)2005,JPO&NCIPI
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