| 摘要 |
An apparatus for detecting double-feed of sheets of paper with a light-transmission sensor. The light-transmission sensor is composed of a light emitting source, such as an LED, and a light receiving sensor located on both sides of a paper transport path. Before the first sheet is fed, the gain of a variable gain amplifier, which amplifies an output of the light receiving sensor, is present at a predetermined value so that an output level of the amplifier may be appropriate. When the first sheet passes the light transmission sensor, an output level of the variable gain amplifier is measured and the level for a sheet is stored. Each time a sheet is fed in the sequential paper feeding operation, the output level of the amplifier is measured and compared with the stored data to detect double-feed of sheets. If the level is not appropriate, the intensity of the light emitting source is controlled in order to correct the level.
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