| 摘要 |
<p>A device for detecting the density (optical reflectivity) of an original, for use in a photocopying machine, includes a light source (LED, 1) for projecting light towards the original sheet (2), a photosensitive light detector (5) for receiving light reflected by the original and a plane or convex reflective surface (30) placed behind the original, for reflecting back to the original and to the detector light transmitted through the original. The reflective surface (30) has a fluorescent dye coating (30a) which increases the reflectivity of the surface, whereby of the measured optical reflectivity (density) of the original is independent of the paper thickness thereof. The fluorescent coating comprises diaminostilbene, uranin, thioflavine T, eosin or rhodamine B.</p> |
