Thu 5 Nov, 2009 02:18 am
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?
If anyone can give any opinions, i would greatly appreciate. Thanks!
Let see if you only wish to detect your source being on in sun light I would suggest placing a signal on it and then used a old analog second older OP amp RC filtering technology to block out anything but that signal bandwidth.
In any case we need more details of what you are looking to do.
I've actually done more research, so if you have some time to spare and is still interested, please kindly continue:
Basically i want the webcam and infrared LED to be like 10 cm spart. I want my filtered webcam to only detect the infrared from my LED (approx 940 nm) and nothing else, like i have mentioned.
But i am not sure if, let's say (one of the noisiest possible scenarios), direct bright sunlight reflects off a silver ring at optimum angle, will my webcam detect it? Will it be even more intense than the light from LED?
From what i read, infrared from sunlight is quite intense, compared to visible light from common lightings; and sunlight can reach up to 35000 ++ lux for whole spectrum.
The solar spectrum:
Silver spectral reflectance:
I would not look for your light but for a signal I had placed on that light for example sunlight does not have a 20 khz sine wave on it.
As long as your detector/webcam is not completely saturated by the sunlight you can tell if the LED is there or not by so doing.