| 摘要 |
Thermal printer adapted to detect end of dye donor web by use of light beams. The printer includes a dye donor web supply spindle having a light-reflecting surface thereon. A dye donor web is wound about the spindle, the dye donor web having a predetermined number of substantially transparent color patches therein. A light source disposed near the dye donor web emits an incident light beam containing a predetermined first color penetrating the dye donor web. A portion of the incident light beam that is unabsorbed by the color patches passes through the patches of the dye donor web and is intercepted by the light reflecting surface which reflects the incident light beam. The reflected light defines a reflected light beam that passes through the dye donor web on its way to a detector disposed near the dye donor web. The detector detects the reflected light beam. The reflected light beam received by the detector indicates whether the minimum number of color patches required to produce a full-color image remains on the supply spindle. Operation of the printer is aborted when the detector detects less than the minimum number of color patches to produce a full-color image. In this manner, receiver medium is not wasted and damage to the printer and its print head are avoided.
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