| 摘要 |
PROBLEM TO BE SOLVED: To correctly detect a density of a toner image by providing relative range variable means varying the relative range between the toner carrier and photoreceiving means as irregular reflection light of the projected light on the toner carrier increasing. SOLUTION: This device preliminarily sets the relative range L between a transfer belt 1 and an optical sensor 5 with a shift corresponding to a stipulated regular reflection light receiving range, so as to enable fetching irregular reflection into a light receiving element 3 with a same level as a shape of a transfer belt 1 being preliminarily scratched, even if the transfer belt 1 is in a new state. Then, in company with the scratch on the transfer belt 1 becoming badly, the irregular reflection light become to hardly enter in the light receiving element 3. Namely, the relative range variable means 4 control the relative range L between the transfer belt 1 and the optical sensor 5 so as to be gradually brought close to the stipulated normal reflection light receiving range, so that the ratio of the normal reflection light quantity and the irregular reflection light quantity among the reflection light received by the light receiving element 3. Therefore, the light receiving ratio of the irregular reflection light received by the light receiving element 3 can be adjusted to the specific level. |
