Can a transmitting IR LED (or an array of such devices) be focused into a finite area rather than allowed to spread out? I think this is how laser tag systems are implemented but I am not sure and I want to try this myself. If they can be focused, what what device can accomplish that? A lens? A waveguide of sorts? Thanks for any tips!
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\$\begingroup\$ Yes, like a flashlight. But not like a laser. \$\endgroup\$– gbarryCommented May 18, 2015 at 1:40
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2 Answers
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The easy way to do this is to purchase an IR led with a narrow viewing angle. (This way you don't have to build weird contraptions to focus the IR light.) Look at the data sheets for the IR leds. Smaller viewing angle will mean a more focused IR beam.
You'll be looking for charts like this to compare the viewing angles and relative intensities:
Good Luck!
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IR light can be focused just the same as visible light. Most lenses that work with visible light will also work for IR. However they they might have noticeably worse aberrations when used at IR if they are optimized for visible use.
Also, no collimated beam propagates forever without spreading. The distance over which a beam can remain collimated is limited by the Rayleigh range, which is proportional to the beam diameter and inversely proportional to the wavelength of the light. Beyond the Rayleigh range, even a perfectly collimated beam begins to spread.
answered May 18, 2015 at 1:37