On Fri, Feb 5, 2010 at 12:22 AM, YES NOPE9 wrote: > A Xenon bulb is not a focused point source. =A0It radiates more or less > in a sphere and projector optics sort that out to produce a forward > beam. =A0So I still wonder if a 1500 lumen CREE is viable as a projector > light source. The fact something radiates in a sphere doesn't mean it's not a point source - anything but. Whilst a Xenon bulb isn't a perfect point source, it's not bad relatively - certainly a lot better than LEDs. The whole point of it being a point source is that it does make it easy to focus the light using very simple optics, whereas with something bigger you'll always tend to be projecting an image of the light source. On Fri, Feb 5, 2010 at 7:38 AM, William "Chops" Westfield wrote: > I dunno. =A0The Cree fits all those emitters onto a package of about 1cm > on a side, so it's got a pretty high brightness density, or whatever > you want to call it. That many lumens in something 1cm on a side is rubbish surface brightness. In fact looking at the datasheet it appears to have 24 dies, which are presumably standard cree 1mm square dies so the die area is rather smaller, but that's still not good. Even the other LEDs I mention do far better - 300lm LED die is 1mm a side, so 20% of the lumen output on 4% of the area. > If this goes on, I'd predict that someone comes out with an LED-based > projector whose optics correct for the non-point-ness of the > lightsource. =A0Fancy optics can pretty much be cast, these days, nearly > as cheaply as less fancy optics? Well there's fancy optics and fundamental laws of physics. Essentially the larger your light source the larger optic you need to focus it. That LED will need a huge optic to produce anything like a decently focussed beam. It really is not at all suitable for use in a projector - intended application is general illumination. Chris -- = http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist