[sci.optics] IR source

frerichs@ux1.cso.uiuc.edu (David J Frerichs) (04/07/91)

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).
I am thinking of flashlight bulbs (a line of them) in a reflector aparatus,
does anyone have any ideas on this?  BTW, the solution needs to be CHEAP.

Thanks.

djf

siegman@sierra.STANFORD.EDU (Anthony E. Siegman) (04/07/91)

>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.

ins_atge@jhunix.HCF.JHU.EDU (Thomas G Edwards) (04/08/91)

In article <1991Apr6.182801.25556@ux1.cso.uiuc.edu> frerichs@ux1.cso.uiuc.edu (David J Frerichs) writes:
>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.

Solid-State IR Lasers are to be had for fairly cheap prices (some $20 
and down)...you will probably need to build a current-limiting 
device to keep the output intensity down to the 0.01 mW range for what
you are trying to do.  Use an IR passing lens or curved mirror to
provide the excess divergence.  (Warning...do not look into laser
with remaining eye).

Otherwise, for saner less dangerous missions, Edmund Scientific sells
IR Passband filters which you can put on a very bright floodlamp.

-Tom