The Fraen 30-degree beamwidth collimators arrived today. These work with the Luxeon LEDs.
The illumination they provide is totally free of mottling and patterning, but brightness of "the spot" does vary from the center outwards. The "spot" at 7" working distance is somewhat larger than my field of view of a bit more than 2" dia so the brightness variation within the field of view is probably acceptable.
I then got sidetracked, wondering how these might work as a head-mounted worklight as opposed to available head lights intended for camping, hikeing, caving, cycling, etc. I'm thinking worklight as in working on things within arm's reach. Under hoods, under sinks, working on machinery and computers, I'll skip deilvering babies in the field.
They work OK, better than the LED head lights I've tried and vastly better than incandescant bulb head lights or a 2AA mini Maglight. The light from these sources is not as bright, not white, and it's full of mottling and patterning artifacts that confuse the issue.
Then came the surprise. I tried a BAL (bareass Luxeon) smack up against a lens I got at Ax Man surplus for 35 cents. The lens is .910 dia (real close to the OD of the Luxeon Star), focal length of about
1.8 inches by very crude quick-a-minnit measure. It weighs 4 grams.I think that combo might make one hell of a worklight. When pointed at the wall, it makes a large "spot" that looks like a white disc cut out of paper. More interestingly, when directed at a workbench from a distance of about 20 inches (forehead height while seated in front of the bench), it evenly illuminates at least as large an area as I would be likely to be working in and most of the region I could reach. It isn't as bright as the spot from other head lights, but it's bright enough to read the finest print on an AA cell, see the threads on a
4-40 screw -- and find the damned screw if I drop it and it rolls away from a brighter but smaller spot.Photo at
The photo was taken from somewhat further than arm's reach of the bench. You can see my arm holding the light above the bench. That height is a bit above where my forehead would be if I were seated and working at that bench.
A shorter focal-length lens would work better for an array of lights for use on a microscope -- but it's real hard to beat Ax Man's price of 35 cents per lens and with 4 or more lights I'm quite sure that full brightness would be ample to uncomfortable at the short (6 to 7") light-to-subject distance for microscope use.
The 1-watt Luxeon Stars are down to $6.50 ea in onesies now.