# Inverted conical frustum mini-reflectors: optimizing plano-convex/aspheric light sources

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Barkuti
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Inverted conical frustum mini-reflectors: optimizing plano-convex/aspheric light sources

0K, I had this idea in my mind through conical thinking . It is after optimizing the light throughput for the, sometimes disregarded (but loved), zoom flashlights.
My idea is to use an inverted conical frustum to enclose the emitter. In this way, all of the light rays being emitted at wider angles than the cone's angle would be redirected forward in proportion to the colliding angle differential, right?
Let's make an example with a lens I was discussing about in another thread: a ∅35/32mm OD/ID plano-convex 17mm focal distance glass unit. Let's say that, with these parameters, at maximum focus distance, we would only be capturing a 2 × arctan(16/17) = 86,528590822143°, whereas “16” is the lens radius and 17 the focal distance. This would be the required conical frustum angle in this case; anything higher and we start losing light (not hitting inside the lens surface), and anything lower means we'd get less convergence at the lens, and a narrower flood. General expression: θ = 2arctan(r/f).
In our example, let's say we have an XHP70, with a maximum dome width of ≈0'3" (≈7'62mm) and 4mm of frustum height:

• r1 is our small radius at the base, equal to 3'81mm.
• h is 4mm.
• r2 = r1 + h(r/f), being 7,574705882353mm for this example.

I'd like to hear your two cents.

Regards,

Mr Efficiency

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The human mind, and its programming, is at the forefront of a particular battle of The Light vs evil dark forces. Nearly every human being on this beautiful planet “Earth” has some sort of negative mind programming in its mind. And you better take care of your mind programming, or someone else will in this wicked world.

Edited by: Barkuti on 10/04/2016 - 11:25
keltex78
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You mean a waiven collar?

http://budgetlightforum.com/search?q_as=waiven%20collar

It shouldn’t be a cone, it should be semi-spherical.

Keepin’ the “B” in BLF

Don wrote:
It sounds like the XM LEDs won’t really be suitable for flashlight use. Pity…

pilotdog68
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keltex78 wrote:
You mean a waiven collar?

http://budgetlightforum.com/search?q_as=waiven%20collar

It shouldn’t be a cone, it should be semi-spherical.

I think he is thinking of something different

He is saying redirect light that goes out the side straight forward (I think?) while the “waiven collar” (I forget what MEM calls his) actually directs it back down on the die, creating a more intense spot. It’s only really useful for throw, not flood.

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keltex78
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Hmmm… after re-reading? Directing the light emitted from the side FORWARD from the emitter (based on the artwork, I was thinking reflecting back…) so it is projected to hit the lens? Not sure how that might work, since aspheric-style lights work better as the emitted source becomes a point. With the waiven working so well because it is reflecting the light back onto the same emitter source, thereby increasing intensity :?: :?:

I would think that a cone projecting forward would effectively widen the light source, making the beam have a wider spill around the central hotspot? But optics aren’t my strong point, and they aren’t always intuitive…

Keepin’ the “B” in BLF

Don wrote:
It sounds like the XM LEDs won’t really be suitable for flashlight use. Pity…

ImA4Wheelr
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I would think the reflector would need to be shaped and oriented more like a traditional reflector.  But instead of directing the light straight out, it would aim the light to the center of the aspheric lens.

Picture the light rays reflecting of the conical wall in the OP at the same angle they hit the wall.  The light would be reflected to the sides and not towards the lens.

EasyB
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Can you draw another picture complete with emitter and lens? I am not understanding what you mean.

Barkuti
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After some toying with a convex lens, it is clear to me that, at focal distance from the die, if the lens is observed from a distance the emitter will be seen “filling” the entire lens surface. An inverted conical frustum reflector collar is meant to be of short height in order to allow zoom game (flood). Of course, ample flood will only be possible with big lenses/short focal distance combinations, because if we use smaller/longer focal distance ones we'd be forced to use a narrow angle ICFRC.

Wavien collar? Sounds like an inefficient, patented PoS

Cheers

Please avoid fully quoting lenghty posts, namely with nested quotes. Trim quotes down to the essential. Helps with neatness and legibility. Thanks.

The human mind, and its programming, is at the forefront of a particular battle of The Light vs evil dark forces. Nearly every human being on this beautiful planet “Earth” has some sort of negative mind programming in its mind. And you better take care of your mind programming, or someone else will in this wicked world.

pilotdog68
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Try also searching for BLF “reflective aperture” Patented? Yes, though the company is defunct now. POS? nope. People got crazy high throw numbers with them, when focused properly. Maybe you already knew that and were just being cheeky.

Sounds like you are trying to do something different, than the wavien, though your concept isn’t making any sense to me.

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Barkuti
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That would be the “zoomed in” lens position. The collar would be made shorter, it doesn't needs to be that tall, about the dome's height I'd say. It's just a quick pic.

Cheers

Please avoid fully quoting lenghty posts, namely with nested quotes. Trim quotes down to the essential. Helps with neatness and legibility. Thanks.

The human mind, and its programming, is at the forefront of a particular battle of The Light vs evil dark forces. Nearly every human being on this beautiful planet “Earth” has some sort of negative mind programming in its mind. And you better take care of your mind programming, or someone else will in this wicked world.

pilotdog68
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Definitely not what I though you were illustrating with your first picture.

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EasyB
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The light from the reflector would not be collected into the hot spot, but I suppose it could be engineered to add a sort of corona around the hot spot. Is this what you are after?

Barkuti
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My idea is just to capture all of the emitter's light which wouldn't hit the lens directly without it, being lost thus. In this way we could still have both nice flood and efficient throw, but please bear in mind I wasn't thinking in pencil beams but in increasing the output efficiency, chiefly.

This could be easily tested I think, it shouldn't be hard to make/machine one of these pieces and try out. A lathe, a drill inserting a milling bit at an angle… or sort of that. Then some way of making the surface mirror finish. Of course, others may think different.

Cheers

Please avoid fully quoting lenghty posts, namely with nested quotes. Trim quotes down to the essential. Helps with neatness and legibility. Thanks.

The human mind, and its programming, is at the forefront of a particular battle of The Light vs evil dark forces. Nearly every human being on this beautiful planet “Earth” has some sort of negative mind programming in its mind. And you better take care of your mind programming, or someone else will in this wicked world.

pilotdog68
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I think you’ll find it makes the beam ugly.

Why not just start with a Convoy S2 reflector and chop it off really short?

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Barkuti
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pilotdog68 wrote:
I think you'll find it makes the beam ugly.

Why not just start with a Convoy S2 reflector and chop it off really short?

Maybe a good idea.

Will it fit an XHP70? My guess is that the appropiate gear for it would be that of 7090 footprint (XR-C/XR-E) emitters, right?

Cheers

Please avoid fully quoting lenghty posts, namely with nested quotes. Trim quotes down to the essential. Helps with neatness and legibility. Thanks.

The human mind, and its programming, is at the forefront of a particular battle of The Light vs evil dark forces. Nearly every human being on this beautiful planet “Earth” has some sort of negative mind programming in its mind. And you better take care of your mind programming, or someone else will in this wicked world.

scianiac
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If I’m understanding what you are saying it would in a way work but you would just end up with a larger spot, or probably a square hotspot and spill around it. You do get more light out the front and in some ways I guess this could be useful but it would not increase throw.

The light from the reflector can not be collimated into the same beam, it will always be either a beam in a different direction like in the case of shifting the light source parallel to the lens or it will become divergent in the case of moving it towards or away from the lens. And both in this case since you will be moving the apparent source in both directions.

I did once put a reflector in a aspheric light to make some flood and it did work but it can get very messy (beam wise) very quickly. I have considered doing it again but in a much less hacked together fashion to make an aspheric with spill but it’s kinda pointless if you end up with just a mess of rings instead of spill.

Co-owner/Engineer at STO Flashlights.

EasyB
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You can get an idea of what it would look like by shining a reflector light into a lens so the die is in focus. The lens will just make an image of whatever is near the focal point. The beam will be the image of the square die surrounded by a dark area then an image of the reflector.

The Miller
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What I take from that was that bouncing back light otherwise lost would get the phosphor light up brighter

Another thing that could happen is a round beam and zoomed image.

Interesting indeed!

djburkes
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Thanks man, got me looking into the big “W” again. Makes me want to butcher a few lights and reflectors to see what I can make.