Re: LED Apparent Brightness

John Larkin wrote:

On Tue, 10 May 2005 20:37:46 GMT, Rich Grise <richgrise@xxxxxxxxxxx>
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



Um, I suggested using sequential RGB led's as a *backlight* for an
LCD... didn't I? Not many led's, lots of lcd pixels.

Instead of having a pixel per color, each lcd pixel would handle all
three colors, sequentially, so you get a 3x improvement in pixel
density for free. And there would be no color filters, so light usage
efficiency goes up at least 3:1. The only bug is that most lcd's are
too slow to switch at the required speed, say 150 Hz or so.

There's an article in EDN (?) this month; some projection displays are
indeed using fast lcd's illuminated through spinning color wheels.
Still wastes light.

John


Spinning color wheel? Is that by CBS? Does RCA have something different? Do i add that to my brand new black and white television for color?
.

Relevant Pages

  • Re: LED Apparent Brightness
    ... >>>illumination when multiplexing is not needed... ... >>>the IR illuminator could be the predominate light source, ... Not many led's, lots of lcd pixels. ... Instead of having a pixel per color, each lcd pixel would handle all ...
    (sci.electronics.design)
  • 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. ... But, um, is it seriously unrealistic to contemplate a panel of RGB LEDs, ... I think heat and power are the main reason. ...
    (sci.electronics.design)
  • Re: How to extract color?
    ... calculate the color of each pixel, and then, to detect ... RGB values of, however if the illumination is ... but might fail your colour discrimination test. ...
    (comp.soft-sys.matlab)
Loading