| 摘要 |
PROBLEM TO BE SOLVED: To make setting of a threshold to discriminate presence/absence of an document unnecessary and to exactly detect document size even when there are variation and aging of a reflection type optical sensor. SOLUTION: Angle detection between a document retainer white board 14 and document glass is performed by an angle detection means (a document cover closed state detection switch 15, an angle detection part 16). Then, output values from the reflection type optical sensors 12a-12c in the case of predetermined first and second angles are acquired at a state that there is no document on the document glass 11 and ratio between them is stored in a storage means 18 as reference output ratio. When the document size is actually detected, ratio among output values of the respective reflection type optical sensors 12a-12c in the case of the first and second angles detected by the angle detection means is compared with the reference output ratio stored in the storage means 18 and when the ratio among the output values of the reflection type sensors 12a-12c is less than the reference output ratio, it is judged that there is the document at a detected part of the reflection type optical sensor. COPYRIGHT: (C)2008,JPO&INPIT
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