The Strength and Technology of State-of-the-Art LED Color Sensor

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  • Kishi Takato
    IA Platform Business Headquarters, Yokogawa Electric Corporation

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  • 最先端LEDカラー計の特長と技術
  • サイセンタン LED カラーケイ ノ トクチョウ ト ギジュツ

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Abstract

For online color sensor in paper production line, conventional xenon flash lamps have been used as light source. Xenon flash lamps have some advantages on color measurement, because they have sufficient illumination and relatively flat spectrum from violet to red for accurate color measurement. However, on the other hand, the xenon flash lamps require seconds of time for charging high voltage that makes color measurement intermittent. And its spectrum contains ultraviolet ray which disturbs measurement on fluorescent sheet. To evaluate the effect of fluorescence, the conventional color sensors have optical filter mechanism to switch“UV-in”measurement and“UV-out”measurement. This means the two measurements are not obtained at the same spot of the sheet simultaneously. On the purpose of addressing the challenges, Yokogawa have developed a new online color sensor using LEDs as light source. The design and technology of controlling visible LED and UV LED separately enable continuous color measurement and reliable fluorescence measurement. Further, the LED controlling technology provides a function of rejecting ambient light coming into sensor gap.<br>Another issue is that color measurement may be influenced by the positional relationship between sensor and measurement plane because it is a kind of reflective sensor. Our new LED color sensor is equipped with an optical system designed to minimize characteristics of pass-line and pass-angle. In addition, it has a function of pass-line detection and compensation using IR LED (our patented technology). As a result, our sensor is insusceptible to deflections of pass-line and pass-angle.

Journal

  • JAPAN TAPPI JOURNAL

    JAPAN TAPPI JOURNAL 70 (3), 287-291, 2016

    JAPAN TECHNICAL ASSOCIATION OF THE PULP AND PAPER INDUSTRY

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