Re: LED Apparent Brightness

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

Hi Rich,
Actually, I think heat and power are the main reason. If you have a very bright LED, they tend to generate enough heat to need a little bit of heat sinking. As you try to get that many of them together, you don't have much room for the heat sink. At least the jumbotrons have room at the back for some fins, or even a little plumbing...

Also, adding up all those 20mA LEDs, that's a considerable amount of power!

Charlie
.

Relevant Pages

  • Re: LED Apparent Brightness
    ... illumination when multiplexing is not needed... ... if you are matching to a shuttered imager. ... By sync'ing these together, the IR illuminator could be the predominate light source, overpowering even daylight, while still maintaining eye safety. ... But, um, is it seriously unrealistic to contemplate a panel of RGB LEDs, ...
    (sci.electronics.design)
  • Re: LED Apparent Brightness
    ... illumination when multiplexing is not needed... ... if you are matching to a shuttered imager. ... Not many led's, lots of lcd pixels. ... Instead of having a pixel per color, each lcd pixel would handle all ...
    (sci.electronics.design)
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