[Laser] Can some explain Steradian please

[Paul Cianciolo]

Hello Folks,

I wonder if there is some one out there in Laserland or LEDland, that can
explain the term steradian in layman's terms.

As the term applies to LED's and intensity.

For example if we start with a "reference LED"

And drive it with say 2 volts and 100 ma that equals 200 milliwatts of DC
input power
What that equates to in terms of light output at a given wavelength I don't
know.

But lets pick a wavelength 940 nm.

Please forgive me if I use some terms in appropriately.


So we have an LED with a set DC input level, and a set radiation pattern,
Lambertian lets say.

SO........

There is a math formula that defines what a Steradian is and I assume that
our reference LED illuminates with a given level.

LEDs are made with all sorts of 1/2 power beam angles. for 160 deg to 3
degs.  So if we put a lens in front of our reference LED and try to
collimate the beam into a narrower 1/2 power angle, does that increase the
mW/Sr?

Is it as simple as looking for the LED with the highest mW/Sr for the
"brightest" infrared LED?

PauLC
W1VLF
http://www.rescueelectronics.com/