Aspheric good for a strap-on dual beam

I used to like aspheric lenses, but now, armed with lux meter, 100 percent diffuser, I am measuring, like, only %70 otfl (out the front lumens), aspheric in wide mode and %30 narrow beam otfl. I suppose photons emitted to side are lost. The loss is unacceptable to eye and meter. Moreover, I am now seeing most my latest aspherics shifting color to cold bluish light.

However, I imagine one place for them (My Hypothesis): Making a reflector's corona go on steriods; aiding a reflector; as part of a dual LED setup (headlamp or fl): one traditional reflector plus one zoomable aspheric.


Yeah, the Fenix hp25 kinda does this (I like its flood, fair on xpe r4 reflector side). But no zoom. The wide hp25 does fine for reading, cloths folding, and navigating. But a 30 degree rocks when aiding a smo throwy on white wall hunting. Also, the ability to zoom might really help out in biking or any other far viewing situation.


So, alone, single emitter ashperics may only have usefulness in lights aspiring to be small and unobtrusive to campsites or shared bedrooms (no spill to bother other person). But they could rock (esp. zoomable) in a dual emitter light, when yoked with a smooth throwy reflector. Weight is important.

My vision:
I was thinking of making a 30 degree xml elastic strap-on (to the barrel) aspheric pill for my single xml (2x18650) or xpg headlamps, with cord leading to some necklace battery pack. Probably, a 30 deg aspheric (white wall hunting) with xml on a 2x3cm spikey heat sink, cording twisty to rear and down to necklace. Some velcro/elastic strap (that wouldn't hurt heat emission of main led lamp) to strap around main headlamp barrel....But boy, I would need to keep it small and lightweight... Smaller means the harder to shed heat; the larger, the heavier and less practical...I have no idea how to make zoomable, but perhaps could make the optic swappable for wide or narrow.

Thoughts?

In the UK, the term "strap-on" has other non-flashlight connected connotations.

easilyled said:

In the UK, the term "strap-on" has other non-flashlight connected connotations.

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I would expect as much from someone in "Middlesex".

degarb said:

I would expect as much from someone in "Middlesex".

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LOL! :touche:

Ok, back to Aspherics. In my opinion, they are best used for one purpose only and that is to throw an led beam as far as possible.

In order to try to prevent lumen loss to the sides, there are two measures that can help:-

1) to choose an emitter with a narrow beam angle. The old XR-Es had the narrowest beam angles of all. Dedoming emitters helps to reduce the beam angle too.

2) to choose an emitter with high surface brightness (like the XR-E) or to enhance the surface brightness by using a Waivien collar. I have mash.m's Black Bullet which uses a dedomed XP-G2 and a Waivien collar and achieves over a million lux per meter.


I have my doubts whether Aspheric lenses are really good for other applications such as "zoomable" lights because of the large lumen loss that this would lead to in their selection for this purpose. The zoom can be achieved by moving a reflectored head up and down, with far less lumen loss (as in Maglites)

I wonder how many patents entangle an acrylic optic (TIR) with a moveable aspheric element in the middle? LEDLenser has a patent on a unibody optic with aspheric center and TIR outside.

AnAppleSnail said:

I wonder how many patents entangle an acrylic optic (TIR) with a moveable aspheric element in the middle? LEDLenser has a patent on a unibody optic with aspheric center and TIR outside.

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Any chance you could link to the patent and save those of us interested in doing the search? I'm curious....

Harold_B said:

Any chance you could link to the patent and save those of us interested in doing the search? I'm curious....

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If someone cranked out 100 lights, violating some patent, due to ignorance. What would be the consequence? Back payment?

AnAppleSnail said:

I wonder how many patents entangle an acrylic optic (TIR) with a moveable aspheric element in the middle? LEDLenser has a patent on a unibody optic with aspheric center and TIR outside.

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I am confused, or at least not clear, in my understanding of certain important optic points and facts.

Okay, I am just now seriously getting into trying to mate led on star with reflector. In past, not much luck getting what I wanted and just abandoned trying to brew up from scratch, in favor of modding a light that had a beam pattern that I liked.

With my latest wrist light build, I am still waiting on reflector shipment of several sizes. Reading now, I see if not aluminum, you get loss through plastic. And aluminum oxidizes over time.

I just assumed a TIR was a fancy aspheric. I am now thinking it may be using something similar to fiber optics? The TIR characteristic, I am guessing (none in hand) is that the plastic surrounds the led better collecting side emission with channels to lead the light out the front. Maybe, the loss isn't so bad. Aspheric may need some overpriced waiverly collar to channel side light up. Is my vision deluded?

Then, I wonder if most the lights lens light like http://www.cndirect.com/1600lm-18650...cus-black.html are just aspheric (it has just a moveable plastic lens). So maybe I don't hate TIR. Then again, I am betting my Browning Phantom 70 and RayoVac 4AA were TIR (of whom I judged fair otf loss, per my gut feeling). I am betting the Browning Nitro headlamp was asheric? But then again, it's beam pattern was square or rectangular ( I don't recall if it zoomed, but think it did.)

Sorry for my ignorance, but I am not getting clear googled answers here. I got a carclo pdf promoting its TIR open here, but it is vague (not directly answering my questions) and mostly just selling idea of lux over lumen output.

Harold_B said:

Any chance you could link to the patent and save those of us interested in doing the search? I'm curious....

Click to expand...

My patent mojo is pretty weak, but that is one. It might be 'the' one. Fraen holds many of the "200 patents" claimed by LEDLenser.

degarb said:

I am confused, or at least not clear, in my understanding of certain important optic points and facts.

Okay, I am just now seriously getting into trying to mate led on star with reflector. In past, not much luck getting what I wanted and just abandoned trying to brew up from scratch, in favor of modding a light that had a beam pattern that I liked.

With my latest wrist light build, I am still waiting on reflector shipment of several sizes. Reading now, I see if not aluminum, you get loss through plastic. And aluminum oxidizes over time.

I just assumed a TIR was a fancy aspheric. I am now thinking it may be using something similar to fiber optics? The TIR characteristic, I am guessing (none in hand) is that the plastic surrounds the led better collecting side emission with channels to lead the light out the front. Maybe, the loss isn't so bad. Aspheric may need some overpriced waiverly collar to channel side light up. Is my vision deluded?

Then, I wonder if most the lights lens light like http://www.cndirect.com/1600lm-1865...-flashlight-torch-adjustable-focus-black.html are just aspheric (it has just a moveable plastic lens). So maybe I don't hate TIR. Then again, I am betting my Browning Phantom 70 and RayoVac 4AA were TIR (of whom I judged fair otf loss, per my gut feeling). I am betting the Browning Nitro headlamp was asheric? But then again, it's beam pattern was square or rectangular ( I don't recall if it zoomed, but think it did.)

Sorry for my ignorance, but I am not getting clear googled answers here. I got a carclo pdf promoting its TIR open here, but it is vague (not directly answering my questions) and mostly just selling idea of lux over lumen output.

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All light-shaping (Non-mule) LED optics/reflectors are pretty sensitive to the LED position. For a great demo, try a focusing LED mag lite. You can see the strange patterns created with a nearly-level LED moved forwards and backwards from the focus point.

There are two ways to make the path of light change: Reflection (Shiny stuff) And refraction (A change in medium). If you jump into a swimming pool, and relax at the bottom (Pockets full of lights, right?), you can see Total Internal Refraction. You can see the sky directly above you, and maybe a few trees, but as you look towards the other end of the pool, the water/air interface reflects the bottom of the pool.

For reasons I don't understand, TIR is used for Reflection and Refraction. http://en.wikipedia.org/wiki/Total_internal_reflection


When light goes from a medium with "x" speed of light, and goes to a medium with "x+1" speed, it bends back towards the denser medium. Light goes fastest in vacuum, slower in air, and even slower in water/glass/acrylic. If you have a shaped piece of acrylic, glass, etc... You can control the final path of the light. It will leave the LED, pass into the bottom of the parabolic acrylic bit, and skitter off the sides of the parabola. It then passes through the flat front of the optic in a shaped beam.

Flat front, curved back: TIR
Flat back, curved front: Aspheric
Flat front, flat back: Window

You always need your LED to be perfectly flat, very centered, and shimmed to the right height. Then you can get pretty beams.

Thanks for the link. Not that patents are all that fun to read but I'm looking forward to this.

Incase it adds to the conversation on TIR, collimation, etc, these are some links to some silicone optics from Dow Corning that give a brief explanation:

https://www.dowcorning.com/content/publishedlit/11-3371-01_Insert_b.pdf
https://www.dowcorning.com/content/publishedlit/11-3371-01_Insert_c.pdf
https://www.dowcorning.com/content/publishedlit/11-3371-01_Insert_d.pdf

There are aspherics, then there are aspherics.

Many of the cheap ones you see on DX, etc, have a fairly long focal distance (I know that isn't exactly technically correct, but it gets the idea across). This means that to get good focus, the LED is quite a ways from the lens, compared to the diameter of the lens. This means that most of the light coming out of the LED never even hits the lens.

In an aspheric like aHorton or jspeybro offer on CPF, the focal distance is much shorter and much more of the light is gathered by the lens. So there is a HUGE difference in the performance of lenses based on the LED beam angle and the lens focal distance.

I don't know if you've tried an aHorton or jspeybro lens, but before you give up on aspherics, please do. I'd love to know if your evaluation of aspherics includes them, or if either of them alters your opinion of aspherics.

Oh, I meant to mention that you can kind of tell the focal length of an aspheric just by looking at it. If it's thick compared to it's diameter, it has a short focal length.

This doesn't apply to Fresnel lenses like jspeybro offers. Instead you have to look at the slope of the outer rings. A steeper slope indicates shorter focal length.

In the original post, you mentioned that it should be lightweight. If you're after lightweight, fresnel lenses are perfect since they only weigh a few grams.

Note that the shorter the focal length, the more light it captures (for the same lens diameter). On the other hand, the shorter the focal length, the larger the magnification of the LED die. It is a challenge to find the best optimum between focal length and magnification. You may end up with a more intense (more lux) beam with a bigger focal length (due to smaller magnification), even if you capture less light.

Wouldn't a small, circular Fresnel in the central 'column' of a TIR do the job?

I've seen a lens/TIR hybrid used in non-LED-lenser lights, so the patent might only be specific to their 'special zooming system'.

P.S; the title was somewhat off-putting. :naughty:

agnelucio said:

Wouldn't a small, circular Fresnel in the central 'column' of a TIR do the job?

I've seen a lens/TIR hybrid used in non-LED-lenser lights, so the patent might only be specific to their 'special zooming system'.

P.S; the title was somewhat off-putting. :naughty:

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Every TIR I've seen already has a condenser lens either inside at the top of the refraction column, or on the output face of the TIR, above the refraction column. I think it is a big part of the magic of why TIR is quoted as being a more efficient optical system

I've seen an LED/reflector hybrid used in a cheap energizer light, could it be this sort of system that the original poster is considering? Either that, or they are simply looking for a TIR.

DIWdiver said:

There are aspherics, then there are aspherics.

Many of the cheap ones you see on DX, etc, have a fairly long focal distance (I know that isn't exactly technically correct, but it gets the idea across). This means that to get good focus, the LED is quite a ways from the lens, compared to the diameter of the lens. This means that most of the light coming out of the LED never even hits the lens.

In an aspheric like aHorton or jspeybro offer on CPF, the focal distance is much shorter and much more of the light is gathered by the lens. So there is a HUGE difference in the performance of lenses based on the LED beam angle and the lens focal distance.

I don't know if you've tried an aHorton or jspeybro lens, but before you give up on aspherics, please do. I'd love to know if your evaluation of aspherics includes them, or if either of them alters your opinion of aspherics.

Click to expand...

My understanding is that with a short focal length aspheric you end up with a much wider spot than with a long focal length. The spot isn't any brighter... it's just wider so you see more stuff illuminated in it.

To get a brighter spot with higher lux, you need a wider aspheric lens.... which means a larger flashlight head.

I suppose high quality custom aspherics might also use coated glass lenses that transmit more light than the cheap plastic ones in budget lights.

Regarding loss of lumens in flood mode: This is caused by light hitting the sides of the pill or bezel and not going out the front. In many cheap budget lights when the lens is retracted in flood mode there is still a large gap between the top of the emitter and the bottom of the lens. In order to have the widest flood possible (and thus least lumen loss in flood mode), the light should be modified to minimize this gap. This can often be done by adding spacers around the top of the pill, or filing down part of the bezel or body.

bshanahan14rulz said:

Every TIR I've seen already has a condenser lens either inside at the top of the refraction column, or on the output face of the TIR, above the refraction column. I think it is a big part of the magic of why TIR is quoted as being a more efficient optical system

I've seen an LED/reflector hybrid used in a cheap energizer light, could it be this sort of system that the original poster is considering? Either that, or they are simply looking for a TIR.

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TIR is more efficient because the process is similar to a reflector, but the best reflector's surface reflects approximately 80% of the light, whereas a TIR reflects up to 95% of the light. Also, a TIR collects more of the emitter's output to start with, which also helps.

And yeah, I think the OP is basically describing a TIR when they say what they want.