| 摘要 |
PURPOSE:To take a measurement over the entire surface of a photosensitive drum automatically with high precision by embedding a photoelectric sensor so that an optical path having a reflection point at a predetermined measurement position is formed accurately, providing a driving circuit composed of a test axis driving circuit and a photoelectric sensor, and making a decision on the basis of the output of a photodetecting element. CONSTITUTION:The photoelectric sensor 27 is composed of a pair of a light transmitting element 2a and the photodetecting element 2b and embedded opposite, for example, a desired measurement point M of an electrostatic charger 6. Consequently, the output of the photodetecting element 27b decreases or is eliminated even when the angle of the measurement point M or gap size varies. For the purpose, the output of the photodetecting element 27b corresponding to a normal position is measured previously and determined for every measurement point, and then this value is used as a threshold value to decide whether a measurement result is normal or not by a comparator. |
