| 摘要 |
PURPOSE:To control optical fatigue of a photosensitive body and to detect a stable visual pattern by placing a light shielding plate in a retreating position through a driving means while the visual pattern formed on the photosensitive body is crossed over a photodetection means. CONSTITUTION:The optical shutter 40 is installed in between a P sensor 18P and the photosensitive body 7 which shields the light from a light emitting diode LED so that the photosensitive body 7 is not irradiated, and this can be driven to be rotated with a rotating shaft 42 as a center. Then, while the visual pattern formed on the photosensitive body 7 is crossed over an optical detection means 18P by a control means, a driving means is energized and the light shielding plate 40 is driven to the retreating position which is off the position between the photodetection means 18P and the photosensitive body 7, from the shielding position between the photodetection means 18P and the photosensitive body 7. Therefore, the photosensitive body 7 is never irradiated by the light emitting element LED, and the optical fatigue of the photosensitive body 7 is suppressed. Thus, the stable visual pattern with a high precision can be detected. |
