摘要 |
PROBLEM TO BE SOLVED: To accurately adjust a process control condition in accordance with the degree of the wear on the surface layer part of a photoreceptor. SOLUTION: A pit whose state change in a thickness direction is detected by an optical pit detecting device 17 is formed on the surface layer part 15a of the photoreceptor drum 15. A step-formed pit 28, a step-formed conical pit or juxtaposed hollow columnar pits are mentioned as this pit. The state of the pit is changed according to the progress of the wear on the surface layer part 15a. By detecting the change of the state, the process control condition is adjusted in accordance with the degree of the wear. |