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using the QTI sensor to detect colours — Parallax Forums

using the QTI sensor to detect colours

rusty009rusty009 Posts: 21
edited 2008-12-10 18:46 in General Discussion
Hey, I am trying to sense a white line with my boe-bot robot. I have a QTI sensor but it only senses a white line on a black background. How do I get the sensor to sense a white line on an any colour surface, so for instance a white line on a red surface ? Thanks in advance.

Comments

  • Carl HayesCarl Hayes Posts: 841
    edited 2008-12-10 17:14
    One way would be to use a blue filter on the sensor. The red surface reflects only red light, which won't pass the blue filter on the sensor, so to the sensor anything red will appear black.

    I am unfamiliar with that particular sensor, but surely it can sense the contrast between red and white surfaces anyway? Unless, of course, it responds only to red light, in which case white and red would appear red to it, and it would be totally blind when fitted with a blue filter.

    But a light sensor that was inherently sensitive only to red would be a strange beast.

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    · -- Carl, nn5i@arrl.net
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2008-12-10 18:46
    The QTI sensor senses reflected IR. As such, it is not sensitive to visible colors, unless those colors also exhibit different reflectances at 940nm, the wavelength of the sensor's emitter. Therefore, no amount of filtering in the visible region will improve contrast from the QTI's point of view.

    -Phil
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