rectangular reflector?

[rumbler]

I was looking at the halogen worklights at work and started wondering......
They are rectangular, with a v-shaped reflector and a halogen tube centered in the v.
This would be an ideal configuration for a flashlight. Most "targets" rarely exceed 6-8' tall. Any light from a round beam above the target is simply wasted. Half of the spill beam illuminates the floor and surrounding area, the other(upper) half is lost is space-the sky.
I thing the perfect beam should have a sharp cutoff above the target, a beam that is maybe 3-4 times wider than height and some spill on the floor. A rectangular reflector. It would be great for multi emitter setups, like 4-6 led's in a row. For example, you could illuminate the WHOLE side of a house, car or boat but not waste light by trying to illuminate the moon.
Any comments?
Rumbler

 

[TorchBoy]

This would be an ideal configuration for a flashlight. ... Any comments?

I don't actually think it's ideal to have to hold a torch at a particular angle for it to illuminate its target. That's a hassle that the average user just wouldn't want. For a bike light maybe, because it's held in place at one fixed angle. I tried an elliptical optic on a caving light once and definitely didn't like it.

 

[uk_caver]

I use an unusual optical arrangement in a caving light, but I'm not sure a flashlight equivalent of it would be great.

The arrangement gives a decent spot beam with virtually zero light above the spot, minimal spill outside the spot but with good downthrow, by firing an LED vertically downwards into the lower half of a parabolic reflector, with the reflector having its axis horizontal.

Light hitting the reflector gives a pretty good spot beam - not perfectly smooth or circular, but absolutely fine for practical use. It's just a case of fine alignment to get the 'best' beam.

Light missing the front of the reflector gives local downspill which is brightest close to the user, since that is closest to the downwards LED axis, but which fades away going forwards.

For cave use, that's a decent outcome, since I have a good spot, decent lighting for my feet, and a beam that doesn't dazzle other people as long as I keep the top of the spot aimed below their eyes.
Usually it's mixed with a flood beam, but even without that, it is usable for both distance lighting and local movement without having to point the light downwards.

I can see an elliptical optic being awkward - with the main illuminated area changing with both pitch and roll of the beam. With my setup, even though it's not rotationally symmetric, it's only really the downspill which moves with a roll of the beam, and not with drastic effects on what is lit, at typical angles of roll for a head-mounted light.

 

[Chrontius]

Host something based on that in an Everready Dolphin, maybe.

 

[TorchBoy]

I can see an elliptical optic being awkward - with the main illuminated area changing with both pitch and roll of the beam.

That was it with the one I used, especially in tight spots. I reverted to using a narrow spot beam half way through the first cave I tried it in - it was simply nicer to use, even with very little spill.

Your headlamp arrangement sounds interesting. Is it just half a reflector you use? Or a full reflector but trimmed back at the bottom?

 

[uk_caver]

I use a reflector with most of the top half chopped out (with the reflector axis being taken as horizontal), as below.

I still use the reflector front rim for mounting in the headset, so I don't remove the entire top half, just the back section. Given the reflector is ~50mm diameter, I have enough room in the empty top half for a couple of controller boards (one per LED) mounted on a right-angle aluminium plate that acts as a heat spreader for the spot & flood LEDs.

 

[Gryffin]

I use a reflector with most of the top half chopped out (with the reflector axis being taken as horizontal), as below.

I still use the reflector front rim for mounting in the headset, so I don't remove the entire top half, just the back section. Given the reflector is ~50mm diameter, I have enough room in the empty top half for a couple of controller boards (one per LED) mounted on a right-angle aluminium plate that acts as a heat spreader for the spot & flood LEDs.

Ingenious!! :bow:

I don't suppose you have any beamshots?

 

[uk_caver]

The 'spot' part of the beam does vary with LED used, and precise positioning.

Lux Is/IIIs could give a fairly circular beam, but were sensitive to alignment.

Cree XR-Es were a pain - being very centre-weighted, they tend to light one section of the half-reflector particularly brightly, and are difficult to get anything better than a 'stubby keyhole' beam from.

Seoul P4s seem fairly forgiving about placement (though I was probably getting a bit more practised), and tend to give a spot with a softer edge.

Cree XP-E/XP-Gs are somewhat like the Seoul, almost as easy to position, but with a harder edge to the beam - it's possible to get something close to circular, but there's still an element of the keyhole shape, though much less than with an XR-E.

I just took some very rough beamshots (ignore the colours) of the spot beam centre with an XP-G

And a Seoul P4

Apart from the downspill (which is pretty hard to photograph), that's about it - there's nothing much outside the spot beam where it falls off, since unlike a forward-facing LED in a reflector, only the very edge of the LED is pointing forwards, so there's minimal spill around the spot.