abvgdee
Newly Enlightened
- Joined
- Jun 25, 2014
- Messages
- 49
Problem. Large emitter size smudges the pattern. Better make it smaller. But then you loose in power/lumen/lux.
Reasoning. The central reflector's stripe (the one right below the LED) is flat, i.e. is a part of a cylinder (of special shape). So the pattern is determined in 2D. Making light source a line along cylinder's axis won't change the pattern, and the cutoff sharpness. It's reasonable to assume/hope that similar is close for other stripes. This gives idea if you want more lumens/lux (for the same given area of light source), or you want to sharpen the cutoff: make light source a segment, not a square. So instead of using a single square LED, use 3 (or more) in a row, as close to each other as possible.
A picture as example (not in proportion). A copper pad with a cut - to allow wires to the LED's contact pads below its body. Two such copper heatsinks (and 3*2 LEDs) of course for the SR80.
The thinner the segment - the sharper the cutoff - good. Probably also - the more distinct the upper and lower pattern shapes will be - bad. May be this could be improved by making the segment curved a bit.
It looks that the Philips Luxeon Z ES are precisely for such purposes. They are small, and without the dome (makes it appear smaller than domed), still delivering (pretty) high lumen/watt. They also seem to have a similar angular distribution as Rebels (unlike the Cree XML). So they look like a good choice for replacement the stock Rebels. 3 Luxeon Z can give 1000+ lumens, just like 1 Cree XML.
(I borrowed the idea from Altilons LEDs - 4 or 2 small crystals in a row)
Comments?
Addition: On the above picture light is assumed to be reflected up. Shifting LED down (on the picture) will move its light also down (on the wall). Also, compared with other 2 LEDs, the LED that's closer to the center contributes (a bit) more light to the side of the pattern. So, I'd choose that one LED to blur the transition between the upper/lower beam pattern halves (the main pattern - not the LED spill), like this:
Reasoning. The central reflector's stripe (the one right below the LED) is flat, i.e. is a part of a cylinder (of special shape). So the pattern is determined in 2D. Making light source a line along cylinder's axis won't change the pattern, and the cutoff sharpness. It's reasonable to assume/hope that similar is close for other stripes. This gives idea if you want more lumens/lux (for the same given area of light source), or you want to sharpen the cutoff: make light source a segment, not a square. So instead of using a single square LED, use 3 (or more) in a row, as close to each other as possible.
A picture as example (not in proportion). A copper pad with a cut - to allow wires to the LED's contact pads below its body. Two such copper heatsinks (and 3*2 LEDs) of course for the SR80.
The thinner the segment - the sharper the cutoff - good. Probably also - the more distinct the upper and lower pattern shapes will be - bad. May be this could be improved by making the segment curved a bit.
It looks that the Philips Luxeon Z ES are precisely for such purposes. They are small, and without the dome (makes it appear smaller than domed), still delivering (pretty) high lumen/watt. They also seem to have a similar angular distribution as Rebels (unlike the Cree XML). So they look like a good choice for replacement the stock Rebels. 3 Luxeon Z can give 1000+ lumens, just like 1 Cree XML.
(I borrowed the idea from Altilons LEDs - 4 or 2 small crystals in a row)
Comments?
Addition: On the above picture light is assumed to be reflected up. Shifting LED down (on the picture) will move its light also down (on the wall). Also, compared with other 2 LEDs, the LED that's closer to the center contributes (a bit) more light to the side of the pattern. So, I'd choose that one LED to blur the transition between the upper/lower beam pattern halves (the main pattern - not the LED spill), like this:
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