Re: [ATM] LED's and Diode Electronics

["Bob May" <bobmay@nethere.com>]

Pulsing LEDs has been used in the industry for a long time now.  What
happens is that the apparent brightness is higher to the viewer than if the
LED got the average current as a steady current.  This effect makes it
easier to make arrays bright but not exceed their power rating.  You do have
a limit as the LEDs do produce less brightness with higher steady currents.
Most of the alphanumeric displays do the pulsing of the individual LEDs
which also reduces the current needed to drive the array.
The  problem with our usage of pulsing LEDs is that if you use a camera to
see the returned light, you'll have irregular lighting of the mirror over
time and this will interfere with the testing because you're looking at the
brightness of the return and that won't be constant over the timeframe of a
frame of the video.
My problem is more that the brightness is more than enough unless the LED is
dimmed a bit.  I desire to run the camera at the point where it's autogain
function isn't excited as this ends up messing with the brightness of the
return of the light.  Yes, I can put a very bright LED in there but even
that will just mean that I've got to dim the LED evem more than I'm doing
now to get that desirable level of brightness that I prefer.
Bob May
bobmay@nethere.com
http://nav.to/bobmay
http://bobmay.astronomy.net

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