Infrared color sensitivity

Discussion in 'Electronics Resources' started by rjwheaton, Jan 26, 2014.

  1. rjwheaton

    Thread Starter New Member

    Jan 26, 2014
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    I'm currently using a Lite-on phototransistor (LTR-4206E) and a Lite-on LED (LTE-4206) as part of a object recognition scheme. These are infrared devices. The idea is to detect the reflected infrared emissions from the object as they pass by. I cannot use a method where the infrared LED and phototransistor are facing each other, so I have to use reflected emissions.

    My problem is that the system is much more sensitive to white objects as opposed to black or gray objects.

    Is there a reasonable simple (and cheap) way to resolve this? I cannot put reflective tags or anything else on the objects.

    Thanks in advance for your help.
     
  2. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
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    hi rj,
    Can you post a circuit diagram showing the Emitter and Detector circuits for this project.?
    Also some indication of the highest and lowest reflected signal strengths.
    E
     
  3. crutschow

    Expert

    Mar 14, 2008
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    Can't you just set the sensitivity to detect the least reflective object? Would the larger signal from a white object then be a problem, somehow?
     
  4. rjwheaton

    Thread Starter New Member

    Jan 26, 2014
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    The problem is that there are other object behind the moving objects. And they are very often of a light color. So if I increase the sensitivity, I end up detecting the objects that are further away, and not of interest.
     
  5. crutschow

    Expert

    Mar 14, 2008
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    Are the objects behind stationary? If so they you can just detect changes in the signal from the moving objects and ignore the DC levels.

    Otherwise can you put a black screen between the moving objects and the other objects?
     
  6. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    The Sharp brand GP2xxx sensors give an analogue voltage output that is related to the distance to the object.

    Their internal electronics eliminates colour issues, and they give a reading that can indicate distance, no matter what colour the object is.

    David Cook's excellent RobotRoom web site has a little tutorial on these sansors;
    http://www.robotroom.com/DistanceSensor.html
     
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