| 摘要 |
PURPOSE: To enhance the detecting accuracy of yellow and a light color by alternately emitting a plurality of light emitting diodes as a lighting source, so that the colors suitable for the respective light emitting diodes can be detected. CONSTITUTION: A line image sensor 12 is arranged on an optical axis 14 that is perpendicular to a web 10 on which a picture pattern has been printed, and reflected light and scattered light beams are imaged on the line image sensor 12 by means of a lens system 13. Red color light emitting diodes RD and blue color light emitting diodes BD are arranged in line respectively, and they are thrown on the web 10 being the measuring surface in the directions oblique to the line sensor 12. This optical system is incorporated in a line follower head so that the web 10 of a guide roll is irradiated. As the line image sensor 12, one which is monochromatic and whose light receiving elements of 1024 pieces or 2048 pieces are arranged in a row is used. Thus, even if the color may be yellow or lighter thereof, it can be detected. |
