Re: LED Apparent Brightness

On Wed, 11 May 2005 06:46:09 GMT, Robert Baer
<robertbaer@xxxxxxxxxxxxx> wrote:

>Rich Grise wrote:
>
>> On Mon, 09 May 2005 15:05:21 -0700, John Larkin wrote:
>>
>>>On Mon, 09 May 2005 14:13:16 -0700, Charlie Edmondson
>>>
>>>>There is only one good reason to pulse a light source to get brighter
>>>>illumination when multiplexing is not needed... if you are matching to a
>>>>shuttered imager. I had an application that I was developing, in which
>>>>we were going to use an IR filter in front of a standard CMOS imager,
>>>>adn then use a pulsed IR source with a short pulsewidth matched to an
>>>>equally short shutter time on the camera. By sync'ing these together,
>>>>the IR illuminator could be the predominate light source, overpowering
>>>>even daylight, while still maintaining eye safety.
>>>
>>>Too bad LCDs are so slow. The ideal backlight would be sequentially
>>>pulsed R-G-B led's.
>>
>>
>> But, um, is it seriously unrealistic to contemplate a panel of RGB LEDs,
>> say, 640 x 480, all by themselves, being pixels? Like a micro-jumbotron?
>> Frankly, I've been wondering about that ever since I started reading about
>> the various technologies that have been studied for making flat-screen
>> displays. Is it just that it would be so prohibitively expensive?
>>
>> Thanks,
>> Rich
>>
> In downtown Portland OR there is a billboard right by a major road
>that is made with an array of R, G, B *bright* LEDs.
> It has been in use for over a year (maybe longer) and was replaced
>and/or refurbished - it is brighter now than before.
> So, "prohibitively" expensive would not seem to be a factor..

Yes, I believe the one on/near 6th avenue just south of Portland State
University, on the road going between there and Oregon Health Sciences
University.

Jon
.