On 9/10/19 10:58 AM, John Robertson wrote:
What is interesting is that a number of digital cameras will work in the IR range, so I've thought of getting a visible light filter whenever I again order some lens from Edmonds to play with some of my cameras to see how far they actually see. I have used camera phones for checking IR diodes (including laser diodes on CD players) and the older iPhones worked for that - which was handy for troubleshooting trough optos.
While CMOS and CCD imagers can be very handy for visualizing the near-IR output from IR LEDs, LASERs, and such (750-900nm or so), this approach won't get you very far for thermal imaging. The IR response of CMOS and CCD imagers doesn't extend up into the thermal IR wavelength range. The "infrared" spectrum is a broad segment of the EM spectrum, 750nm to 1mm wavelength. This is particularly broad, especially when compared to the width of the human visual spectrum, which ranges from ~375nm to ~740nm for most people. Most consumer-grade Si CMOS and CCD imagers have useful unfiltered response up to about 1050-1100nm (1.05um-1.1um) or so. The type of IR radiation that's useful for passive thermal imaging consists of significantly longer wavelengths, from ~6um to ~15um...starting at ~6x the wavelength at which typical silicon junction photosensitivity drops off. Due to CMOS/CCD sensors' lack of sensitivity in this region, thermal imagers are usually implemented using a 2D array of thermopiles, essentially tiny stacks of thermocouples, one per pixel, with solid germanium optics. -Dave -- Dave McGuire McGuire Scientific Services, LLC New Kensington, PA _______________________________________________ Techtoolslist mailing list Techtoolslist@flippers.com https://pairlist7.pair.net/mailman/listinfo/techtoolslist FTP site is: ftp://ttl.arcadetech.org/TTL/Test_Equipment Archive site: http://seven.pairlist.net/pipermail/techtoolslist/