| 摘要 |
PURPOSE:To prevent a malfunction of a sensor from occurring due to the light emitted by the sensor itself, by inclining a surface of a light-shielding body opposed to a platen relative to a light-emitting and light-receiving plane of a photosensor, in a paper detector comprising a reflection-type photosensor on one side of a small hole formed in the platen and the light-shielding body on the other side thereof. CONSTITUTION:At the time of paper detection, a light-shielding body 5 is surely located on the upper side of a small hole 2 provided in a platen 1 so as to present disturbing light 11 from being incident on a photosensor 3. When a paper 4 is present on the platen 1, light emitted from a light-emitting element in the photosensor 3 is reflected by the back side of the paper to be incident on a light-receiving element, whereby the presence of the paper is detected. When the paper 4 is absent on the platen, the light from the light-emitting element is reflected by a bottom surface of the light- shielding body 5, but, since the bottom surface is a slant surface 6, the light is reflected to the exterior of the photosensor, so that the reflected light is not received by the light-receiving element. Therefore, in the absence of the paper 4, a malfunction of the photosensor is not caused by the light emitted from the photosensor itself, even when the light-shielding body 5 is proximity to the paper 4. |
