| 摘要 |
PURPOSE:To detect a width without causing a wrong detection even against paper of an indefinite size by detecting the width of paper by plural light emitting element groups which are placed at a constant interval in a prescribed direction and whose light emitting current is controlled through a memory, and a photodetector. CONSTITUTION:An LED array 15 is formed by LEDs arranged at a prescribed interval in the width direction of paper 12, and a current supplied to each LED of the array 15 is stored in a memory so that an output of a photodetector 16 opposed to the array 15 becomes constant, in case when there is no paper 12. The current is supplied successively to the LED through this memory, a width of the paper 12 is detected based on a comparison of the output of the element 16 and the reference value, and even against paper of an indefinite size, its width can be detected without causing a wrong detection. |
