| 摘要 |
PROBLEM TO BE SOLVED: To obtain equal detecting accuracy, without using a CCD sensor, with a simple constitution, as the detection of a toner mark. SOLUTION: A mark detecting means 34 is mainly constituted of a light emitting element 68 for irradiating the surface on which the toner mark 60 is formed, of a carrying belt 2, a holder 70 provided on a side opposite to the carrying belt 2, a slit plate 72 which is arranged to face the light emitting element 68 and held at the bottom end of the holder 70, in a state where the plate 72 is in contact with the rear surface of the carrying belt 2 or with a very small gap and a photodiode 74 as a light receiving element which is fixed on the holder 70, so as to obtain a position facing the light emitting element 68 across the slit plate 72 and the carrying belt 2 and consists of a single light receiving surface. |
