[Laser] Can some explain Steradian please

[Zack Widup]

Hi Paul,

Yes.

73, Zack W9SZ

On Thu, 31 Jul 2008, Paul Cianciolo wrote:

> Hello Zack,
>
> I have read that Wikipedia article....
>
> I guess it boils down to this.
>
> So answer this question please, Would the brighter 940 nm LED be the one
> with the higher mW/Sr rating?
>
> PauLC
> W1VLF
> http://www.rescueelectronics.com/
>
>
> -----Original Message-----
> From: laser-bounces at mailman.qth.net
> [mailto:laser-bounces at mailman.qth.net]On Behalf Of Zack Widup
> Sent: Thursday, July 31, 2008 5:59 PM
> To: Paulc at snet.net; Free Space LASER Communications
> Subject: Re: [Laser] Can some explain Steradian please
>
>
>
> This is about as simple as you can get:
>
> http://en.wikipedia.org/wiki/Steradian
>
> 73, Zack W9SZ
>
> On Thu, 31 Jul 2008, Paul Cianciolo wrote:
>
>> 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/
>>
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