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From: siegman@sierra.STANFORD.EDU (Anthony E. Siegman)
Newsgroups: sci.electronics,sci.optics
Subject: Re: IR source (loose)
Message-ID: <60@sierra.STANFORD.EDU>
Date: 6 Apr 91 19:21:56 GMT
References: <1991Apr3.211135.21492@syssoft.com> <1991Apr6.182801.25556@ux1.cso.uiuc.edu>
Organization: Stanford University
Lines: 17

>I need an IR source (800 nm) that produces a beam about 1ft by 1in at
>a distance of about 1.5m with the intensity equal to the center of
>a flashlight bulb beam.  It doesn't matter if other freqencies are
>present but it would be nice to avoid them (reduce actual heat from the
>source).

That's a pretty imprecise power specification, since human eyes can't
see 800 nm.  But the 800 nm wavelength specification also says that a
GaAs laser diode is the way to go for electrical efficiency and
brightness -- maybe even just GaAs LEDs, depending on how much power
you actually want in the illuminated area.

GaAs lasers or LEDs are readily available and reasonably cheap; and
designing an optical system to project a string of one or more lasers
or LEDs into roughly the spot you want shouldn't be too hard...though
only after you first specify how many watts/cm^2 at 800 nm you really
want in the spot, and how close to exactly 800 nm this has to be.