To accurately detect the kind of paper at the top, in a cassette where a plain paper and an OHP sheet are mixed by setting the arrangements of light emitting and receiving elements with respect to a paper sheet, within specific angles.
This paper kind detector provided with a reflective type sensor is constituted of the light emitting and receiving elements 1 and 2. Then, the arrangement angles of the light emitting and receiving elements 1 and 2 with the paper sheets are set 15°-30°. Even in one plain paper or plural plain papers laid one on top of another, almost the same reflectance is shown. On the other hand, when one OHP sheet exists on the plain paper or as the number of sheets laid one on top of another is larger, the reflectance is higher. In other words, the arrangement angles of the light emitting and receiving elements 1 and 2 are set 15°-30°, so that in light projected from the light emitting element 1, the light passing through the OHP sheet becomes extremely little and most of incident light becomes regular reflected light. Therefore, even if one OHP sheet exists on the plain paper, the upper sheet is hardly influenced by the lower sheet and the kind of paper at the top in the cassette can be discriminated.
FUKAZAWA NOBUAKI
WAKAMATSU KAZUHIRO
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