Is it possible to get 100% polarization in 1.67? Checking this job from the lab with a polarized demo at 90 degrees off axis and still getting a fair amount of light transmission. Lab says this is normal. Rx is -500 DS and -600 DS with about 9 base.
Is it possible to get 100% polarization in 1.67? Checking this job from the lab with a polarized demo at 90 degrees off axis and still getting a fair amount of light transmission. Lab says this is normal. Rx is -500 DS and -600 DS with about 9 base.
Sounds like a case of REDO AVOIDANCE to me. Send it back.
Do you see a cross when you hold another polarized lens 90 degrees to the glasses? Sometimes you may not fully block out light checking this way; you may have to try checking them either front to front or back to back @ 90 degrees before you will totally block out all light.Originally Posted by AEOC
-Tony
No, no cross is visible. Transmission does vary depending on how I position the test lens. It's darkest at 90 degrees on one lens and about 45 degrees on the other. The range between most and least transmission between the two sides is the same. Lab manager is absolutely sure these are polarized lenses. Said he checked some blanks and he's not getting complete cross polarization on those either. Maybe the manufacturer sent them a bad batch?
Make sure they're Younger NuPolar.
DragonlensmanWV N.A.O.L.
"There is nothing patriotic about hating your government or pretending you can hate your government but love your country."
I believe they are from Younger. Lab is supposed to call and get their thoughts.
Use your own polarized glasses, not the demo.
Put your own polarized on, and see if the 1.67 are equal darkness right/left at the window.
Harry
@AEOC:
I find that the best polarization check method is to have a polarized plano mounted in a occluder loupe. The lens is scribed with the 90 and 180 axis and can be held close to the lens surface where the theoretical black-out will occur. If trhe cover polarized lens is too far away from the lens being tested light leakage will occur. The scribe lines allow me to dot the 180 of the lenses being tested. Then the sunglasses are checked on any lens aligner.
You stated the the darkest blank out on one lens is at 90ish and one is at 45ish??? Sounds like someone rotated the lens(45ish) at layup before edging(to cut out) because it was a sphere, forgetting that polarized lenses have an AXIS.
Send it back.
P.S. You won't see a cross or shouldn't, if you do that is a stress pattern and it means, for a plastic lens that it is too tight, IMO.
It was surfaced off axis via the polarization!
We do mucho polarized and the film used in the 1.67 is very nice; we have never had any issue with the lens blank used in this material. If you are getting light transmission as you described, it was surfaced incorrectly.
We use the Younger polarization card to check all jobs. We use all free form and the first time we had a pair of progressives made with the polarization off axis it took us a while to figure out why the patient hated the glasses. We now check all lenses as they come in and they are certainly surfaced off axis some times.
You can check with the card to see how off axis the lenses are and by wearing them to look at a color polarized demo the colors will appear different if the polartization is off at all.
Hope it helps.
Craig
Okay. Just got a handful of blanks from the lab, a couple NuPolar and a couple Essilor and they all show the same thing. Cannot get complete cross polarization with any of them, although the Essilor lenses seem to have a slightly larger area around the optical center that is polarized. I've attached pictures of what the lenses look like in front of my LCD screen.
In any case, both these blanks are significantly better than the finished pair so I think I'll send it back for a redo.
Where would one obtain a polarized color demo card?? Would our labs maybe be able to get us these?
Yes, your lab should be able to get one for you.
Hello moderator(s)
Would it be possible to move this thread to the ophthalmic optics section? I'd like a little more information on this issue (and I'm predicting that this well educated patient is going to also). Thanks.
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