Doughnuts anyone?

There was a thread in this section about the SF L2 and doughnut holes in the beam, a classic 5W LED problem. I just got a KL4 head which is a 5W but has no hole in the beam.

I have a McLux PR 5W which has a hole in it's beam. Maybe I don't know for sure what the poster meant by "dougnut hole" in the beam but mine looked more like a MagLite with a unfocused beam or the reflector was too far back.

I removed the lens cap, slipped the reflector out a bit and turned the light ON. The hole was gone!

I used some 1/32" gasket paper to make a shim and installed it under the reflector. I like the results much better.

I bought this head from a fellow CPF'r here. I've never built a head yet. Is the position of the LED to reflector preset, different by LEDs, something overlooked, etc?

The donut hole is normal with a 5 watt in a PR. The shim you used is the correct answer. You might try shims with different thickness to find the best focus for a 5 watt Luxeon.

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Hoghead said:
The donut hole is normal with a 5 watt in a PR. The shim you used is the correct answer. You might try shims with different thickness to find the best focus for a 5 watt Luxeon.

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Interesting that PDFs about assembling a PR/T head don't mention anything about focusing the beam at all. The beam is improved a lot by doing so.

This doesn't happen with a 1W I assume? I wonder why?

The 1 watt and the Luxeon III don't have donut holes.

The "point of light" is larger for a 5 watt than a 1 watt or a Lux3.

If you shine your 5 watt PR at a wall and move it closer you will find that there is still a hole there. Mine have a hole at about 6 inches, but it disappears at 8 inches. If you use shims of different thickness this distance will change.

The 5w is actually uses four 1w dies, so there are four light sources instead of one (as in a 1w or Lux3). This means each is slightly off center and can focus/defocus into the doughnut pattern mentioned bout.

That's one of the nice things about the PM6/McModule mods - the reflector can be adjusted without using shims - just turn the head a bit! /ubbthreads/images/graemlins/smile.gif

Jon

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StoneDog said:
The 5w is actually uses four 1w dies, so there are four light sources instead of one (as in a 1w or Lux3). This means each is slightly off center and can focus/defocus into the doughnut pattern mentioned bout.

That's one of the nice things about the PM6/McModule mods - the reflector can be adjusted without using shims - just turn the head a bit! /ubbthreads/images/graemlins/smile.gif

Jon

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If you shine it close to a wall you see four lobes like you mentioned. I see now! I also still see a spot from looking at a bright spot on the wall too long. /ubbthreads/images/graemlins/grin.gif

my new L4 has no doughnut hole like my first one had. im really stoked.