Dear askmehelpdesk members,

Recently I want to set up a system so that my webcam will only detect infrared (940 nm) from only my infrared LED and nothing else, using 940nm-allowed-only filters.

In case I really need to do this in a place with plenty of strong sunlight, do you think sunlight reflection from shiny rings and/or shiny metallic table surface can potentially induce noises to my webcam? Do you think that through adjustments of threshold (the level of voltage considered valid) and exposure level of my webcam, I can potentially reduce COMPLETELY ALL sunlight reflection noises, but still detect my infrared LED?

Any quick opinions please. Thank you so much.

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Originally Posted by kb_bkk

In case I really need to do this in a place with plenty of strong sunlight, do you think sunlight reflection from shiny rings and/or shiny metallic table surface can potentially induce noises to my webcam?

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Possibly. I have a client where the rising sun in the morning will trip their security system motion sensors, but I think they work in the far infrared.

Quote:

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Originally Posted by kb_bkk

Do you think that through adjustments of threshold (the level of voltage considered valid) and exposure level of my webcam, I can potentially reduce COMPLETELY ALL sunlight reflection noises, but still detect my infrared LED?

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My gut feeling is probably. I think it would depend on what you are trying to accomplish and how focused the LED is on the webcam, brightness relative to other IR emitters, distance, etc. Also, since your webcam is filtered to a specific wavelength, any reflection would have to be at exactly that frequency to reach to cam further reducing the probability of random interference.

Dear Mr./Mrs. Scleros and other viewers,

Just for information, I've done more research.

In case you have a little time to spare as well as interest, please kindly continue:

I would say one of the most noisy case within my scope would be direct sunlight reflecting on silver rings at optimum angle into the webcam.

http://wpcontent.answers.com/wikipedia/commons/thumb/9/9d/Image-Metal-reflectance.png/400px-Image-Metal-reflectance.png

You can see silver reflects so much at approx 850- 940nm

In addition, at the right angle of reflection, our eyes can easily see that direct sunlight can be extremely bright and direct sunlight can reach up to 32,000–130,000 lux for full spectrum.

According to http://lasp.colorado.edu/~bagenal/3720/CLASS4/SolarSpectrum2.jpg despite sun infrared reaching only (very approximately) 50% of the rays in the visible spectrum, I think it's reflection on a silver ring can still be more intense than a 5mm LED.

Would you agree at all on this?

kb_bkk

Here are some typical solar spectra AIR MASS 1.5 global.

Solar Spectral Irradiance: Air Mass 1.5

Quote:

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Originally Posted by kb_bkk

I would say one of the most noisy case within my scope would be direct sunlight reflecting on silver rings at optimum angle into the webcam... i think it's reflection on a silver ring can still be more intense than a 5mm LED... Would you agree at all on this?

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Yes for specific scenarios of ring, LED, and camera location.