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  1. #1
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    TIR optics...

    Quote Originally Posted by rsilvers View Post
    I hope any of these lenses have AR coatings or else we are losing 7% right there.
    Quote Originally Posted by tigris99 View Post
    Sorry dude but alot of your information about lights is WAY OFF. First off tir optics dont have ar coatings, nor is it needed. And its not losses at all.

    I'll get more into details to clear up everything I read later

    Quote Originally Posted by rsilvers View Post
    Why is TIR exempt from the lens/air interface loss?

    There is still an input and an output surface and they are not exempt from the lens/air interface loss. It may cost more. It may not be worth it. But they would have less loss with AR.

    Better prisms have AR on the in/out:

    Right Angle Prism (AR Coated: Entry And Exit Faces) Uncoated Hypotenuse Face

    https://en.wikipedia.org/wiki/Schmidt–Pechan_prism
    Quote Originally Posted by tigris99 View Post
    Because that interface is what acts as the reflective edge. Where reflector with ar lens is up to about 85-90% at best, optics see 95% efficiency otf.

    This is why they are called TIR optics. Total internal reflection. Completely different than anything else for this purpose. Any ar coating will render the optics totally useless.

    Its also why your no supposed to handle them without nitrile/latex gloves. The oil from your fingers can damage them. And can only clean the front of them with water or rubbing alcohol.
    The is only true of the sides that the light reflects off of. If you get dirt/oil on the sides, then the light won't internally reflect as well.

    The light still has to exit the front, and an AR coating on the front would help, not hurt, light transmission. I gave links to a prism example - which also uses internal reflection and has AR coatings on the input and output surfaces.

  2. #2
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    Removed cause I wasnt fully awake yet.

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    I started a thread because I was asked to stay on topic in the Chinese lights thread.

    You still didn't answer anything or explain why you think that an AR coating would not help light exit a TIR lens with less reflection (loss) on the exit surface. It will. It costs more. That is why it is not done.


    Quote Originally Posted by tigris99 View Post
    Not going to dignify this with a response. Simply, your as wrong as it gets.


    Fyi: Prisms refract light which is why the AR coating, they DONT REFLECT LIGHT.

    Prisms certainly can reflect using the TIR principle:

    https://en.wikipedia.org/wiki/Prism#Reflective_prisms

    Total internal reflection

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    No its not done as you see it because the companies that design and manufacture optics have their reasons for not doing it. There is no benefit.



    Reason: All reflective surfaces are utilized to control the beam pattern to create desired viewing angle and pattern.



    Put a non ar lens in a flashlight, then an ar lens, look what happens, beam pattern changes.



    At coating will only serve to ruin desired beam pattern and the slight boost that may be gained in output is barely noticeable if at all to the human eye.

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    Quote Originally Posted by tigris99 View Post
    No its not done as you see it because the companies that design and manufacture optics have their reasons for not doing it. There is no benefit.
    The benefit would be more light emitted.

    Quote Originally Posted by tigris99 View Post
    Reason: All reflective surfaces are utilized to control the beam pattern to create desired viewing angle and pattern.
    True. I was not suggesting to coat the reflective surfaces.

    Quote Originally Posted by tigris99 View Post
    At coating will only serve to ruin desired beam pattern and the slight boost that may be gained in output is barely noticeable if at all to the human eye.
    It would not ruin the beam pattern.

    Ok. So now you agree it would allow for more light transmission. Fine. Not worth the cost. Fine. That is all I was trying to say.

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    Here's more food for thought:

    Emitters have a silicone dome. Remove that or as is now being released, what they call high intensity (has a thin silicone coating to protect the emitter phosphor)

    That changes the beam pattern, actually tightening it up. Decreases viewing angle and increases throw.

    Theirs alot of factors but AR coating remove the ability to have precision control of how the light behaves and is projected out the front.

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    Actually im not in agreement that it will allow more light transmission. I only agree that its possible.



    And YES IT DOES AFFECT BEAM PATTERN, BY ALOT. I have a massive amount of bike lights (yes im a light nerd ) and several flashlights. Some custom built/modded some not. 2 identical edc flashlights, one with and one without AR lens have different overall beam patterns. Im not just talking the spot, talking the entire amount of light out the front and how its projected.



    Even different versions of AR lenses change the overall pattern of light.

    It has NOTHING TO DO WITH COSTS. If it was beneficial then Carclo and/or LEDIL would utilize it. They don't currently.

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    Quote Originally Posted by tigris99 View Post
    And YES IT DOES AFFECT BEAM PATTERN, BY ALOT.
    I said it would not ruin the beam pattern. I know it effects the beam pattern.

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    It does "ruin" the beam pattern as every reflective surface is utilized to control the beam. Change those properties, desired effect is changed. Mostly what I see in flashlights is an AR lens creates a beam pattern more similar to optics.

    And you already said you dont like frosted optics..... That's what happens when you mess with the reflective surface. Not an AR coating, but same effect, front of lens is no longer effective at reflecting light. So you did say it ruins it basically

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    Coating the reflective surfaces with an AR coating can do no good. I am only speaking of coating the output surface where reflection is not desirable.

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    It is desirable, otherwise you end up with a similar effect as a frosted optic (which is basically coarse surface to remove a percentage of reflective properties)

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    I don't like frosted optics for two reasons. One is that they shoot light outside of the desired light cone. So even if you want a very wide cone that one may want for a bar light, 1/4 of the light could go outside of even that wide area. Two is that they absorb more light as heat.

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    I am curious where you read they absorb more light as heat???

    As for the effect on beam pattern, that's what AR coating does. The light isn't being reflected to control the pattern, so you end up with same effect.

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    Quote Originally Posted by tigris99 View Post
    I am curious where you read they absorb more light as heat???
    I didn't read it recently. If you look at the lumen rating of frosted home light bulbs, they are lower than their clear counterparts. There seems to be absorption going on and not just light redirection.

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    I can see diminished output and optics efficiency is a couple percent lower in frosted form. Im not a huge fan of frosted optics either except for the light on my fat bike that I built. I want the extra light into the spill area of the optics so I have a more wide viewing range all around. In the woods on singletrack I dont like it so much.

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    Quote Originally Posted by rsilvers View Post
    I didn't read it recently. If you look at the lumen rating of frosted home light bulbs, they are lower than their clear counterparts. There seems to be absorption going on and not just light redirection.
    What kind of bulbs do you mean? Soft white incandescents are frosted with a film of chalk (rather than being textured) so of course that is going to absorb light. Dunno how LED bulbs are frosted (because haven't broken any yet, whew!) but imagine it is done with some kind of internal coating that is translucent rather than clear, or the globes would not appear so white when the lamps are off. Though perhaps a similar effect could be achieved through texturing, be interesting to know what percentage of light is lost through the globes in either case.

    The anti reflective coatings on some computer screens and prescription glasses I've always found kinda problematic. They are difficult to maintain, smudging readily while easily ruined by the use of common cleansers. Two pairs of $400 glasses right down the drain, not to mention my old eMac.

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    Typical GE Soft White have some kind of coating, but there are also "frosted" bulbs, which seem to be just frosted glass. Glass is frosted via either blasting or acid etching.

    Here is an example of the same bulb - one frosted and one clear:

    75 Watt, 120 Volt T4 Frosted Halogen Mini Can Bulb | Q75FR/MC (Frosted) | Bulbs.com
    75 Watt, 120 Volt T4 Clear Halogen Mini Can Bulb | Q75CL/MC (120V) | Bulbs.com

    1050 vs 1350 lumens. So the frosting absorbs about 22% of the light and converts it to heat.

    You may be able to measure a difference of the heat on the BT-21 with an IR thermometer on the top, and then change the optics to clear, and redo the test.

  18. #18
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    Frosting on optics is a texture (or embedded coating) on the outside of the optics. I have polished it out of an optic as an experiment. Worked well.



    As for IR thermal readings based on optics changes, there isn't enough variance to notice, 1 deg variation in ambient temp, slight difference in air flow over the case etc changes results. Frosted versus not show no noticeable change in case temp. I read 1-2 deg F warmer but simply having the lighthead more perpendicular to my airflow generator can cause that.



    As I said, if the thermal effects are real, their minimal. No effect on performance.

    When I get my DIY sphere up and running ill be testing all kinds of things, ill add frosted vs not to the list.

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