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Selective Incident Headlight Intensity Measurement

  1. May 11, 2017 #1
    Hey guys,
    I am trying to come up with an idea to measure incident intensity of headlights from an oncoming car for one of my uni projects. This wasn't specifically assigned project topic, we get to choose what we want to do. It's my Instrument and Measurement unit, and I had this idea thought it would have an interesting application considering how many times I have driven on the freeway and just got completely blinded by an oncoming (or following) car. We've learned of different methods of measurement like an LDR (Photoresistor) in a voltage divider and calibrating a micro controller to give you readings in Lux. But I was wondering how one could roughly go about measuring a specific car's headlight by pointing the device at it and filtering out some of the other light 'noise' so to speak? I'm thinking something akin to a pinhole camera, sort-off? Any Suggestions?
    Thanks in advance!
  2. jcsd
  3. May 11, 2017 #2


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    there are so many ways to do it.
    Yes, one way is to use a pinhole or just a hole to limit the incoming light from one direction only. The drawback is that you will get very little light on your detector this way.
    Another way is use a lens and place the detector at the focal point. You will be collecting all the light hitting the lens aperture (read something about photography, aperture setting, etc.)
    Another way is to use a camera and some software to process the image and pick the maximum intensity of the light.
    One note of caution. The sensitivity of a typical detector or a camera depends on the wavelength of light in a manner that is different from the human eye response and you would need to use a filter to bring the detector response close to the photopic curve.
  4. May 12, 2017 #3


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    Mount the sensor at one end of a tube to restrict its field of view. Depending on the sensor size you can use anything from a cardboard core from a roll of toilet paper to a straw or a piece of plastic pipe. Change the length to change the field of view.
  5. May 12, 2017 #4

    jim hardy

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    You would do the world a favor if you'd measure spectral content.

    HID and short wave LED make wavelengths known harmful to the eye yet automakers and aftermarket suppliers continue to pump out "El Blasto" equipment as advertisers brag about their ability to illuminate the countryside along both sides of the road.

    "Xenon Headlamps - the weak man's imitation of strength". It's on account of them I wear sunglasses when driving at night. I've complained to my congressman, to Ford Motor company, and to National Highway Traffic Safety Administration about the spectral content and preposterous intensity of modern headlamps.

    Anyhow, back on topic - a non reflective tube with receiver at one end should work for you.
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