| 摘要 |
PURPOSE:To ensure that a print error attributed to some degree of meandering print surface including a dark part such as photograph can be accurately detected by using a tolerable value for comparison and making a tolerable value for the specific area of the print surface higher than that of any other area. CONSTITUTION:If a print surface 3 meanders, a track deviates to the right and the left from a light receiving element 27 in an advance direction. Therefore, the light receiving element 27 is allowed to device as a whole instead of the print surface 3 and thereby move in parallel with the print surface. Further, an electric signal is previously sampled to obtain signals (B), (C). The signals are significantly influenced at a part corresponding to a photograph, if the print surface includes part of photographs X1, X2 and slightly meanders. The part where the value of a signal (A) varies significantly due to the signals (B), (C), corresponds to the area for the photographs X1, X2. If a tolerable value is to be obtained using the signals (A), (B), (C) thus obtained, an allowance a is adjusted for a floor value, where the area for the photographs X1, X2 area concerned, and an allowance alpha is adjusted for a reference signal (A), where some other area is concerned. |
