Precision Optic lens AKA aspherical for incandescent flash lights?

Have received several inquires regarding the use of precision optic lens in flash lights. Well, opened this thread first for modders who have used them to share their expectations, experience, set backs, opinions.

The asphere's more complex surface profile can eliminate spherical aberration and reduce other optical aberrations compared to a simple lens. A single aspheric lens can often replace a much more complex multi-lens system. The resulting device is smaller and lighter, and possibly cheaper than the multi-lens design.

LED modders have used aspherical lens and familiar with the critical distance set up of lens to LED and curvature of lens relationship. Often have head asphericals are for LEDs, they don't work with incandescents. Radical asphericals like fish eye types project the image of a incan. filiment and look fairly sick.

Hook's law helps classify glass types by sorting according to Young's moduli. BK7 is 82. This relates to amount of heat stress capability or specific thermal tension exist when a heat gradiant exist causing internal stress.

So much for the technical, perhaps someone with an understanding of glass properties will contribute.

This lens I found has more heat resistance than current usage borofloat or UCL windows an advantage with 100+ watt mods. Also, it focuses visible light into a culminated stream in a way I have not seen before. See pic below. The beam is a perfect circle, has more throw than with boro or UCL lens, and has usable side spill.

2/22/08 See post #29 for ongoing evaluations of lens and recommendations in post #29. jim

Re: Precision Optic lens for flash lights?

Interesting, what are you using, and can it be used to focus a ROP?

AlexGT

Re: Precision Optic lens for flash lights?

Well, I'd like to know more. I've seen a lot of mag mods with aspherical lenses, but I wonder why they are more spherical than lenticular.

Re: Precision Optic lens for flash lights?

AlexGT said:

Interesting, what are you using, and can it be used to focus a ROP?

AlexGT[/quot

haven't used with ROP but think would work with any incan. bulb once have the proper distance between lens and bulb. That is a important measurement in LED mods using Aspherical lens and they have indept threads of discussion.

here is link describing it. I got it from surplusshed.com and they have a wide selection.

https://www.candlepowerforums.com/threads/179620

Found that with a camless reflector focused using a boro lens the precision optic lens could also be focused with slight adjustment of the head up or down.

The lens I use is not aspherical in the sense used around here, big fisheye type, but it is aspherical by definition.

My motivation and interest comes from developing mods with extreme heat, ruined reflectors, and need for thermal management. And along the way found a beam pattern generated I really like.

The physics involved is beyond my scope of interest but the application is interesting.

I went through 4 different lens wavelengths, focal lengths, and optical coatings and each may have some use in flash light mods. Of the 4 one I really like and just sold with the mod.

Hopefully, others here will become interested and continue

Click to expand...

Re: Precision Optic lens for flash lights?

lenticular is a term for the lens effect that creates a convex perspective of multiple images or light sources. That fits the fisheye looking aspherical lens I have seen used with LED mods.

Can you tell me the difference?

greenlight said:

Well, I'd like to know more. I've seen a lot of mag mods with aspherical lenses, but I wonder why they are more spherical than lenticular.

Click to expand...

Re: Precision Optic lens for flash lights?

Jim, thanks very much for starting this thread. I had sent you a PM with this link, and some in the 50.8mm size had some measurements that were close to what you posted in your sales thread...but I'm not understanding all of their chart measurements as compared to the top line drawing.

Edit: After some more reading, I now see the diagram in this link has the following correlation.

EFL - Effective Focal Length column = diagram letter "f"
BFL - Back Focal Length = diagram letter "fb"
te - Edge Thickness
tc - Center Thickness

Can you give the Surplus Shed part number of the one you found best of the four? Thanks!

Edit: So now I'm guessing this one in your sales thread, because I'm not seeing any with a 3.8" edge thickness as you listed. What is hard to figure out is this one has a 254mm focal length, which is 10 inches, and must result in the lamp being way forward of the focal length origin. The closest to that on my first link to BrightenOptics is their lens #[FONT=Verdana, Arial, Helvetica, sans-serif]BOPX-S50.8-250. It's just hard to figure out using the focal length in an incand bulb....and basically because I don't know squat about how to identify lenses. Maybe I'll call these guys.
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Re: Precision Optic lens for flash lights?

Lux, as in my reply to your pm the last link in your post here is the lens I used. I doubt it is the only one that could work.

Lux in your post here your trying to figure this out from a scientific point of view. I did not know squat about aspherical lens until read some of the threads in LED section.

What I understood is there is a relationship between curvature of the lens and distance between lens and bulb.

Therefore, since that lens worked best with LEDS, as oppossed to one a few mm different reason leads to the conclusion with an incan. bulb given the correct wavelength it would be stunning.

Bought several blindly so to speak having only a theory based on logic instead of facts based on physics.

Motivated out of need for lens, reflectors, switchs which can withstand the extreme heat of current mods one might say alot of things but I'm sticking with logic as why this particular lens works.

jim

LuxLuthor said:

Jim, thanks very much for starting this thread. I had sent you a PM with this link, and some in the 50.8mm size had some measurements that were close to what you posted in your sales thread...but I'm not understanding all of their chart measurements as compared to the top line drawing.

Edit: After some more reading, I now see the diagram in this link has the following correlation.

EFL - Effective Focal Length column = diagram letter "f"
BFL - Back Focal Length = diagram letter "fb"
te - Edge Thickness
tc - Center Thickness

Can you give the Surplus Shed part number of the one you found best of the four? Thanks!

Edit: So now I'm guessing this one in your sales thread, because I'm not seeing any with a 3.8" edge thickness as you listed. What is hard to figure out is this one has a 254mm focal length, which is 10 inches, and must result in the lamp being way forward of the focal length origin. The closest to that on my first link to BrightenOptics is their lens #[FONT=Verdana, Arial, Helvetica, sans-serif]BOPX-S50.8-250. It's just hard to figure out using the focal length in an incand bulb....and basically because I don't know squat about how to identify lenses. Maybe I'll call these guys.[/FONT]

Click to expand...

Re: Precision Optic lens for flash lights?

can someone tell me where moved to?

Thanks,jim

Re: Precision Optic lens for flash lights?

There was a previous thread where someone actually used an aspheric lens with an incan, but I can't find it. In the same way as with the LED pattern, there was a clear projection of the actual shape of the filament.

An aspheric lens is designed to work best with a point source of light. The principle is similar to using an accurate reflector – it will work best with small sources of light, which is why the best-throwing pencil-beam lights are those with short-arc bulbs (for example, the Maxa Beam).

Because of the critical importance of focus, it would be necessary to use an incan bulb with as small a filament as possible, and more importantly a horizontal filament rather than a vertical one. The more powerful hotwires, with longer/vertical filaments, would not be suitable.

Just looking at the WA 1111 & 1185, these are both fairly small and horizontal and would probably work OK. The 5761 is small-ish and horizontal, but the coil of the filament is larger, ~1.5 mm in diameter, and focus needs to be very accurate with an aspheric – 1.5 mm might sound small, but with this application it might be too large.

With an incan, you would get an enlarged and fairly precise projection of the filament's shape, which would look quite weird and because of the artifacts it would have a pretty limited use, apart from wowing people who saw it.

LEDs are also very much more directional than incans. Even the widest-angle LED doesn't emit light behind it, so it will throw at least 2x as much of its output forward compared to an incan bulb, where the beam is pretty well omni-directional (spherical) until directed by a reflector.

A reflector is in fact useless when used with an aspherical lens, as the lens only works with a point source. Any light hitting the lens via a reflector will still come out, but this will be in a random direction as spill.

Depending on the diameter of the lens and its distance from the light source (a factor of its focal length) the useful focused light from an incan might be as little as ~15% of its output, while with a LED which threw most of its light forward in a fairly tight cone anyway, like a Cree XR-E, the figure might be even better than the ~66% you get with a reflector.

I think for these reasons, LEDs will have a significant edge over incans with aspheric lenses.

Re: Precision Optic lens for flash lights?

David,

Of course you points are true when using that size\curature of aspherical LED moders use.

Some people who use that type of aspherical I've read over and over in different threads their conclusion is as yours aspherical are better suited for LEDS and not incan.

The current wisdom (current amps) small joke, is won't work with incan and will work less well with vertical filament.

Proof is in the pics, have a look. The 62138 with its vertical filament looks far better than 64625, which have not posted pics of 64625 but will. Look at the 62138 pic not a trace of filament shadow in that beam.

The mind set, current wisdom among modders somehow got locked into beliving something was not possible, something did not work and drew a conclusion based on experience rather than logic.

Why it works with incans. is the same reason aspherical lens work with LEDS. And that is there is a relationship between curvature\wavelength of lens, and distance of lens to bulb. Therefore, since one aspherical lens worked best with LEDS (forget which now) as oppossed to one a few mm different reason leads to the conclusion that with an incan. bulb given the correct wavelength and distance of lens to bulb it would be stunning.

I can not explain the physics of why it works you have more ability along those lines. What is apparent is in the pic at top of this thread.

I am going to bed.
Cheers, jim

DM51 said:

There was a previous thread where someone actually used an aspheric lens with an incan, but I can't find it. In the same way as with the LED pattern, there was a clear projection of the actual shape of the filament.

An aspheric lens is designed to work best with a point source of light. The principle is similar to using an accurate reflector – it will work best with small sources of light, which is why the best-throwing pencil-beam lights are those with short-arc bulbs (for example, the Maxa Beam).

Because of the critical importance of focus, it would be necessary to use an incan bulb with as small a filament as possible, and more importantly a horizontal filament rather than a vertical one. The more powerful hotwires, with longer/vertical filaments, would not be suitable.

Just looking at the WA 1111 & 1185, these are both fairly small and horizontal and would probably work OK. The 5761 is small-ish and horizontal, but the coil of the filament is larger, ~1.5 mm in diameter, and focus needs to be very accurate with an aspheric – 1.5 mm might sound small, but with this application it might be too large.

With an incan, you would get an enlarged and fairly precise projection of the filament's shape, which would look quite weird and because of the artifacts it would have a pretty limited use, apart from wowing people who saw it.

LEDs are also very much more directional than incans. Even the widest-angle LED doesn't emit light behind it, so it will throw at least 2x as much of its output forward compared to an incan bulb, where the beam is pretty well omni-directional (spherical) until directed by a reflector.

A reflector is in fact useless when used with an aspherical lens, as the lens only works with a point source. Any light hitting the lens via a reflector will still come out, but this will be in a random direction as spill.

Depending on the diameter of the lens and its distance from the light source (a factor of its focal length) the useful focused light from an incan might be as little as ~15% of its output, while with a LED which threw most of its light forward in a fairly tight cone anyway, like a Cree XR-E, the figure might be even better than the ~66% you get with a reflector.

I think for these reasons, LEDs will have a significant edge over incans with aspheric lenses.

Click to expand...

Re: Precision Optic lens for incandescent flash lights?

64625 with its horizontal filament may have just as culmenated a beam as the 62138 given proper lens wavelength and lens to bulb distance.
62138


64625 doesn't show as well in pic but some filament shadow noted.

Re: Precision Optic lens for flash lights?

Thanks, Jim - I completely missed that link in your post #4. That is a very impressive light!

It is also a very interesting result. I would guess that the vertical filament, by being partly defocused, has the beneficial side-effect of eliminating the artifacts. Whatever the case, it clearly works, and I'm glad to have been proved wrong.

What is the ratio of hotspot diameter to distance? With my LED + 52 mm aspheric the ratio is about 1:40, so for example at 100 feet the projected LED image is ~2½ feet across. If the figure for your incan is anything approaching that 1:40, it should be an absolutely astounding thrower.

Re: Precision Optic lens for incandescent flash lights?

I'm guessing what is happening to give a good result, is JJ used a lens with a focal length of 250mm (10") which would mean that a light point 10" behind the center of the lens would be in perfect focus (think the LED Aspherical projects).

The fact that the filament light source is in the forward part of the cone, may still look like a "point light source 'blob'" The lens cannot tell if the light source is back 10" or back a couple inches. The less thickness and convex surface as compared to the LED Aspherical 1D/1C projects, likely has this incan filament appear in effect as a larger, less well defined light source as if a smaller source would have been placed back 250mm.

The light does not get as sharply/acutely refracted in JJ's 250mm focal length as it would in the short 37mm focal length distance used for the LED's. Here is my crude drawing to illustrate the idea, and finding the focal length of each lens.

Re: Precision Optic lens for incandescent flash lights?

I may be missing something here - I didn't see any mention of a 250 mm focal length.

From my (rudimentary) knowledge of physics, your idea in that diagram wouldn't work. If the object isn't at the focal length, it won't be in focus. If the bulb filament was where you put it, i.e. at a shorter distance to the lens, the light will pass through the lens but would then keep on diverging (spreading out).

The lens would have a refractive effect, but the beams would hit the lens at too wide an angle and there would not be enough refraction to bring them parallel. If on the other hand the filament was at a further distance than the focal length, the beams would strike the lens at too narrow an angle, and they would be over-refracted. This would mean they would cross over after they had passed through the lens – and then after crossing over, they would again diverge.

It is only at the focal length that you will achieve parallel beams. If you are slightly under (in front) or slight over (behind) the focal length, there will be divergence, and therefore some blurring. The further away from the focal length, the worse the blurring.

Caveat to ALL the above – I may possibly be talking TOTAL nonsense, lol. I'm very ready to be corrected if I'm wrong!

But what Jim seems to have managed is to harness a slight blurring effect by using a vertical filament, so part of the filament (half-way down) is in focus and the rest (nearer and further) very slightly out of focus, and therefore slightly blurred. He has used this very slight blurring to eliminate the artifacts you would otherwise expect to see, but at the same time without losing too much through blurring.

It's a very effective result, and I'd love to know what the spot size to distance ratio is. I guess we'll have to wait till he's had a night's sleep!

Re: Precision Optic lens for incandescent flash lights?

DM51 said:

It's a very effective result, and I'd love to know what the spot size to distance ratio is.

Click to expand...

me too, and i also would like to know more about any use of the Reflector in this application or in the led applications.
people have mentioned having or not having the reflectors in, and were the light from the reflector comes out. but i cant grasp it. here i put a reflector in, and a bit more light moves foreward, but its all over the place.

i can defocus the cree led pattern easily for an 18" beam at 15feet with the lens everyone liked most. even go to very wide beam, but its not a lazer untill its a projection of the emitter.

he told us that there is still minor artifact, but the picture is to Blazingly bright to see any artifacts in the sun center there.

Re: Precision Optic lens for incandescent flash lights?

VidPro said:

people have mentioned having or not having the reflectors in, and were the light from the reflector comes out. but i cant grasp it. here i put a reflector in, and a bit more light moves foreward, but its all over the place.

Click to expand...

Light coming off the reflector will go through the lens, but because it is not coming directly from the focal point, it will be spread out by the lens and you will see it as spill. So the reflector isn't any use for concentrating the light when you've got an aspheric, but it does add spill. I hope that makes sense - it's the best way I can describe it.

Re: Precision Optic lens for flash lights?

David,
thanks for helping me learn something. Don't know what the ratio is but will measure it tonight and let you know.

Jim

DM51 said:

Thanks, Jim - I completely missed that link in your post #4. That is a very impressive light!

It is also a very interesting result. I would guess that the vertical filament, by being partly defocused, has the beneficial side-effect of eliminating the artifacts. Whatever the case, it clearly works, and I'm glad to have been proved wrong.

What is the ratio of hotspot diameter to distance? With my LED + 52 mm aspheric the ratio is about 1:40, so for example at 100 feet the projected LED image is ~2½ feet across. If the figure for your incan is anything approaching that 1:40, it should be an absolutely astounding thrower.

Click to expand...

Re: Precision Optic lens for incandescent flash lights?

VidPro,
The reflector is in as usual, it's a smo camless. Reading your post got an idea. Took the lens and placed it in 2"deep reflector hotwire with 8xNiMh and 1164. lens went from 12mm distance to bulb with usual reflector to 45mm distance to bulb in deep reflector. Hot shot on wall 5" rough circle to 38" perfect circle in 2" deep reflector at 21feet distance from light to wall.

One night while working up this lens project, don't recall which lens but one of aspherical samples here, was foggy a bit and could see in front of flashlight about 12-18 inch the beams cross over and then ran parrallel

David distance outside from flash light to side of house 33ft. Hot spot about 48".

those aritfact you reference below I only saw when using 64625 which did not quite have the fit as the reflector was drilled for 62138 which is tight fit 64625 is larger diameter.
jim

VidPro said:

me too, and i also would like to know more about any use of the Reflector in this application or in the led applications.
people have mentioned having or not having the reflectors in, and were the light from the reflector comes out. but i cant grasp it. here i put a reflector in, and a bit more light moves foreward, but its all over the place.

i can defocus the cree led pattern easily for an 18" beam at 15feet with the lens everyone liked most. even go to very wide beam, but its not a lazer untill its a projection of the emitter.

he told us that there is still minor artifact, but the picture is to Blazingly bright to see any artifacts in the sun center there.

Click to expand...

Re: Precision Optic lens for incandescent flash lights?

got locked into beliving something was not possible, something did not work and drew a conclusion based on experience rather than logic.

we were just waiting for you to show us how to do it
just like i am hoping that more Fresnel lenses are tested for the low heat applications, and as a "snap-on" changer
Quickbeam and Nereus have tested some stuff
https://www.candlepowerforums.com/threads/176821

---- a bit off topic---
did you ever notice , that when newton "invented" gravity, defined it or theorised about it, that sorta after that moment, the idea of it being a mystery to explore, exploit, or understand its corelation to and with other things was lost.
it is entered into the calculations, put on the charts, understood to the aspect of what is thought to be known about it, and stymied. everything we know about gravity is stuffed in "the book" , and any out of box thought is discarded. somewhere out there is a gravity beyond Newton. It will only take a Apple to land on someones head before we know what it is. then THAT will become old school passive knowledge again.

Re: Precision Optic lens for incandescent flash lights?

So for let's say a FM 2.5 inch throw master, what would be a good focal length to buy? I see surplusshed have a wide variety in sizes that would be drop in replacements.

AlexGT