| 摘要 |
PROBLEM TO BE SOLVED: To detect existence of sheets at plural positions as well as existence of sheets at one position as in conventional devices by using a single detection element to receive light radiated from a light emitting part by a light receiving part. SOLUTION: A sensor comprises a light detection element comprising a single light emitting part 31a and a single light receiving part 31b for receiving light radiated from the light emitting part by the light receiving part, and outputting an electric signal in accordance with light intensity of received light, and light shielding flags disposed in a light way between the light emitting part and the light receiving part. In this case, the light receiving flags are composed of plural light shielding flags 32, 33 of different light transmitting factors, and the light shielding flags 32, 33 are set to be actuated by sheets existing at different positions, thereby existence of sheets at two positions can be detected by the single detection element based on four types of light receiving intensities at the light receiving part 31b. |
