| 摘要 |
PROBLEM TO BE SOLVED: To form high-quality picture images, by making the line width in the direction of a detecting line of a resist mark a specific times as wide as the width of detection in the direction of the detecting line of a photoelectric sensor, in a picture image forming apparatus which detects the position of the resist mark and performs resist correction. SOLUTION: A resist mark is detected at specified sampling intervals by an optical sensor unit 25 successively with the movement of a transfer belt 10. Here, the line width of the resist mark in the direction of detection by the optical sensor unit 25 and the width of detection of the optical sensor unit 25 are set so that their relation may satisfy a fixed condition and a detected signal whose peak waveform changes smoothly from a minimum value up to a peak value is obtained. Setting is performed so that the value of W1/W2 may be 0.8 or less, when widths of the peak waveform at positions where its output values are 1/2 and 1/e<2> times as large as the peak value are represented as W1 and W2. The line width in the direction of detection of the resist mark is three times or less as large as the width of detection in the direction of detection of the optical sensor. |
