| 摘要 |
PROBLEM TO BE SOLVED: To provide an image forming device capable of preventing trouble of an AE mode which is caused by a change in an amount of light with an elapse of time. SOLUTION: In an output signal, an A-part corresponds with the output value of the bank ground of an original document and a B-part is the output value of the image area of the original document. In the case where data for altering the reference value of an AE sensor with the elapse of time is fetched, a reference value is altered with predetermined timing, for example every 1000 sheets of paper. When the data of the 100-th original document before the alteration is fetched for it and the reference value is determined based on it, the data of the original documents which are 900-th, 1900-th, 2900-th and so on are fetched. The position where the data is fetched may be arbitrarily determined, as 10mm from the front end or the entire area of the original document in a scanning direction. In the case the data is fetched in an area between D and E, the value A of the output signal corresponding to the part where an amount of reflected light is largest in the area is adopted as the reference. |
