| 摘要 |
PURPOSE: To prevent a stain due to dust, etc., from being detected erroneously as a pattern mark, to accurately stop a belt and to display a desired pattern correctly in a belt type pattern display device. CONSTITUTION: An interval along the turning surface of a display belt 52 between an optical sensor 30 and an optical sensor 31 is set at a value equivalent to four pitches of the pattern mark 60, and when one of the optical sensors 30 and 31 detects the pattern mark 60, another sensor detects the pattern mark 60 located at a position separated by four pitches. Since the output level of the optical sensor 31 on the other side is set at a high level even when the stain R exists on the edge of the display belt 52 and the output level of the optical sensor 310 goes to a low level, no pattern mark signal is outputted from a detecting part, therefore, the stain R is prevented from being detected erroneously as the pattern mark 60. |
