| 摘要 |
PROBLEM TO BE SOLVED: To provide a relatively inexpensive sheet size sensor without need for separate switches or sensor matrix for determining a sheet size. SOLUTION: A paper guide 102 slidable in the left/right direction is mounted, abutting to a paper stack 54, on the bottom 100 of a tray. A gray scale 104 which is continuously variable is printed on the bottom of the guide 102. The gray scale 104 is located at a position to be detected by a sensor 110 located under the tray 100. Signals are outputted from the radiation part of the sensor, reflected on the gray scale, and detected by the receiving part of the sensor. Then the sensor 110 produces a signal, a function of the value expressing the quantity of the reflected light. Since the quantity of the reflected light is variable according to the position of the gray scale, the position of the sensor and the sheet size can be measured by measuring the quantity of the reflected light. |
