We use quite a lot of A/R and recently we have been getting our 1.6 index back with a rather "bright" purple back reflection. Has anyone out there found this to be the case with the 1.6 index product they use. We do about 85 to 90% A/R and about 45 to 50% 1.6. All the other product looks really good. I was told by the lab that the back reflection on 1.6 has always been this way. Well, the experience that I have had with A/R over the years does not prove this to be the case.
Sorry to be the one to break this to you, but your lab just doesn't know what they are talking about. Maybe the lenses THEY produce always have looked that way, but that just means that they have always made them wrong. The color difference comes from mis-matched materials: 1.60 lens material, who-knows-what-kind of front scratch coat, probably ultra optics' UVNV backside coat, and an A/R coat that is generic (and probably not any good).
When done properly, in a controlled environment, you will have color consistency, like I do.
Whats wrong with Ultraoptics Back side coating?
As far as I know lens index and material does not effect A/R reflex color. Thats a result of how many layers the coating may have in addition to thier index and thickness. The mix-matching of the indices can create more of an oil slick look. Could be wrong though...:)
You can not judge good AR from bad AR by the look. Is green AR better than blue AR. The brightness appearence is just that how they appear to you. To check the AR performance you need a spectrophotometer.
You can have the same amount of light transmittence with a green AR and a blue AR. If both AR coatings are designed to give the same light transmission.
One side note: Most AR for optical lenses is green. Have you ever noticed that almost all camera lenses are blue, purple or red toned? Why not green for camera if it is the best color for AR? I think this is the result of what we are used to seeing. Green was used first and green is the standard in the optical industry.
Yep, in Canada we get the Crizal D Alize as a choice versus regular Alize. D Alize is blue. It is much nicer, as the lenses do disappear more. Crizal also advertises (I said advertises) that D Alize has a light transmission of 99.6 percent versus the Alize with 99.2 percent.Originally Posted by AWTECH
Perhaps the residual green worked better under incandescent lights but now that fluorescents are so prevalent the blue is a little more accepted? Just a thought, but I'm sure there's some marketing guru out there with an answer!
What about Zeiss Gold? I can remember seminars and sales reps telling me that the gold residual color was better for night time driving. I always asked why and never really got the answer. Food for thought.
Fezz
:cheers:
Remember the purpose of AR, it is to increase light transmission and the color of the AR is cosmetic. There maybe some reason that an AR produced near the blue spectrum is better for this or that, but I believe that whatever benefit is claimed this benefit is so small that it would be very difficult for someone to receive any real noticable benefit.
Answer:
Nothing, unless you want to put a good A/R on it. Look at the number of returns for scratching you get back, and you will find that what you see as scratches is on the back side (mostly), a closer investigation will show that it is not scratches you see, but really coating delamination. The greater majority of A/R coatings produced today are designed for hard-coats, not scratch coats- and yes, ther's a BIG difference.
You are a bit correct, but also wrong. The residual reflection you see is the design of the given coating formula. Green is easiest to maintain (particularly the yellow-green that the empire uses) because you will not notice variations unless you are part machine. In this, you are correct, optidonn. However, the formula is designed for a known substrate and scratch coating combination. When you mix materials, the result of the formula is thrown off on the variable side, which is the side with the uv-cured scratch coat. This effect is not seen except in cases where the difference is great- like high index lenses. The front will likely be mostly green, the back will vary between red, purple, and rainbow. If you're really lucky, the back will be green in the middle, red/purple on the edges, and you can cut most of the varying color out, and feel like you did a service to the end user. However- I think that most people in this business don't look that closely at the lenses when finished, so there are many out there saying "what's HE going on about?". The end user (customer/patient/wearer) doesn't know enough to notice, and doesn't even clean the glasses, anyway, so why does it even matter? You'll send them back to the lab for a warranty redo FOR FREE, complain that the lab didn't do a good job, but keep on using that lab. In the end, none of this really matters. You made money, who cares about anything else?(sarcasm)
(Except where specifically mentioning you, optidonn, the other "you" is general, not specific; but you probably knew that, I hope.)
Tired of reading.........................
Attack...................Attack
The color hue of an AR lens has to do with different metal oxydes applied during the coating. Only any other coating applied OVER it may change that hue slightly. What's underneath has nothing to do with it.
I am tired of reading that nothing else but your Essilor and Zeiss coatings are the only superb and usable ones under gods sun.
The machnies for applications are all the same in principle and so are the products that are applied and used to produce the coatings.
:hammer: :finger:
We have been using Ultra Optics scratch coat on all materials W/AR for 5 years (alot of lenses) without a problem.
Joseph Felker
AllentownOptical.com
hipoptical. You are also some right and some wrong. I'm not an A/R engineer but I'll quote an expert: "Not least because if the surface layer is not of precisley equal thickness, and refractive index of the coating does not match that of the lens, then 'interference colours' can be seen, as on a thin film of oil. This can sometimes be seen on materials such as polycarbonate when a 1.5 index hard coat is applied to the 1.586 substrate material. This effect may become more obvious if an antireflection coating is applied on top of a non-matching index hard coat." Mo Jalie. I kinda trust him;) . If anything I've seen budget lenses that have a coating that could be considered not a true 'Broad Band' coating. Meaning they don't cover much of the visible spectrum. Meaning they have less layers and can give a more intense relfex color. If you were to compare one of these budget coatings to any modern multi layer A/R it would look almost as if the budget coating were a flash mirror compared to most of the coatings we currently use. You can check out more here.
Last edited by OPTIDONN; 08-23-2006 at 09:22 AM.
My original question was has anyone seen a purplish back reflection on 1.6 index a/r coated lenses. all other materials are what i would consider to be within a normal range for a premium a/r. light greenish blue.
I've seen a few from our lab that were like that. It's like a more intense color that is more reflective and therefore less effective. I sent them back for redo and they came out fine after that. Definitely any time the residual becomes more noticeable, you have a problem.
thank you iocana. i apprieciate your input.
I have never seen this occur. I do a lot of 1.60w/ar and I have never seen this so I would question your lab again.
Try another lab for your high index ar and see if it's better. Your present lab may be trying a cheaper AR system (maybe the $50,000 chemat system. )
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