| 摘要 |
PURPOSE:To enable the yellow portion of a color ink portion or the like to be definitely detected by providing the light receiving surface of a photosensitive element with a filter for transmitting the light with a wavelength in the neighborhood of 560nm. CONSTITUTION:A sensor 8 is formed in a casing 81 with a groove 82 through which a color ink ribbon passes. A light emitting element 83, such as a light emitting diode, and a photosensitive element 84, such as a photodiode, are housed in the manner to oppose the groove 82. The element 83 has its peak emission wavelength selected in the neighborhood of values 560-580nm. Further, the light receiving surface of the element 84 is provided with a filter 85 (interference film adhered to the light receiving surface by evaporation) and transmits only the light with a wavelength in the neighborhood of a value 560nm. The light from the element 83 has only yellow transmitted through the color ink ribbon due to the spectral characteristics of the ribbon. Further, by disposing the filter 85, the element 84 hardly detects magenta in particular and therefore the difference in the detecting output for yellow and the other colors can be made distinct. |
