Vertical blue reflection in polarized lenses

**Sleepy_Lab_Rat** · 11-02-2010, 12:37 PM

I have a problem I haven't encountered before and I'm stuck.

I work in a wholesale lab and one of our accounts contacted me about a patient of theirs who had a problem with a pair of polarized sunglasses we recently made. The patient was complaining of vertical blue 'lines' in the lenses when looking at the sun (meaning towards the sun, not at the sun of course).
Thinking there was a possible reflection off the lens edge or the frame I had the account send me the glasses. Sure enough, when I look through them towards the sun, there is a BRIGHT bluish/purple line running vertically through the approximate middle of each lens. I've never seen anything like it before.
I eliminated lens edge reflections and reflections from the frame as possible causes. I had an antireflective coating added to the lenses and that didn't help.
Finally, I completely remade the lenses (with AR) on the off chance that there was a defect in the polarization and/or lamination. Before the lenses were edged, I took the unuts outside to see if they had the same blue line. The left lens was line-free (very faint, only noticable if you look for it). The right lens still has a bright vertical line. It's obviously a reflection/refraction of some sort but I can't figure it out. I looked through the glasses with a baseball cap on to help block the sun from the top of the frame/lenses and that didn't eliminate the line. If I hold my hand out in front of me between the glasses and the sun, the line goes away. Panto helps (too much panto to adjust the frame that way). If I tilt the frame side-to-side (either wearing it or looking at it while holding it in front of me) the line moves with the frame/lens (stays parallel to the B measurement) until I've tipped the frame about 45 degrees when the line disappears.

Here is Rx in question:
OD -1.50 -0.75 x130
OS -1.50 -0.75 x030
3.00 add OU
CR-30 Polarized grey Comfort lenses. 4 base. Crizal Alize AR coating.

The patient has a pair of glasses with the exact same frame and almost identical Rx that does not exhibit the problem (the patient is not willing to give them up to compare them to the current pair). The biggest difference I can see between the old "good" pair and the current pair is that the add power increased from 2.25 to 3.00.

Sorry for the length of the post but I'm hoping I've included some detail in there somewhere that will make one you say, "I know exactly what that is!"

I've managed to solve some pretty strange "the patient sees x when they wear the glasses" problems before, but this one has me stumped.

Any ideas?

Thanks!

**Jeff Trail** · 11-02-2010, 04:37 PM

The first question to ask, did you check it BEFORE AR? .. was the "line" in an uncoated pair? and what was the CT on these lens? at the end of the day, changing the axis of the polar sheet, when you looked through an angle the problem is almost certianly in the polar sheet.. now you are going to have to figure is it due to warping during AR, (degas or ringing?) or possibly a bad batch...the lens did not all have the same lot number? ... If you verfied before and after AR, was not there, and than it was..well it elimanates being surfaced induced. Since you checked them "uncut" that also elimanates stress warp from mounting or chuck pressure waring the lens enough that you pick it up behind the polar shield..
As much as any lab rat hates to do it, I would check the CT and you may have to bump that a little, check it before AR is applied, and might as well check the boxes to see if they all happen to fall into the same lot, just to eliminate factory problem.

Jeff "understand your pain all to well" Trail

**Barry Santini** · 11-02-2010, 04:42 PM

The laminate and the AR are the potential sources of this problem. Put them on yourself and look near the sun. If its there, you'll figure it out

Barry

**braheem24** · 11-02-2010, 07:27 PM

What are the polarization angles on comfort polars? Switch to a lens with another angle.

**Sleepy_Lab_Rat** · 11-03-2010, 08:05 AM

Thanks for the replies!

The first pair I saw did not have AR on them and the line was there. I sent them to have AR added and the line didn't go away.
I had both lenses completely remade with AR and still got the line on the OD but not so much on the OS (very faint). This is the pair I checked as 'uncuts' (after AR but before edging). They looked the same before and after edging.
The CT on all 4 lenses is 2.4mm with a ET of 2.1mm. The boxes for the first pair are long gone and the 2nd pair was surfaced at the coating facility so I don't have those box tops either.

I was leaning towards some sort of lens defect myself considering that the line is almost completely gone in the newest left lens but is still there in the right. It seems possible that the good left lens was made with a different batch of polarization film or something.

I think I will try switching to a different lens altogether and see if that helps.

Thanks for the ideas! I'll be sure to post how things turn out.

**WFruit** · 11-03-2010, 08:10 AM

I would try running the same pair in a different polarized progressive. If it's a problem in your process somewhere, then those lenses will have the same problem. If it's a problem with the lenses, then you won't. I'm inclined to agree with Jeff that you probably have a bad lens batch. Given that Essilor ran out of polarized lenses and was scrambling to get more in this past summer, I'm willing to bet that some slid through QA that maybe shouldn't have.

**NCspecs** · 11-03-2010, 09:02 AM

Originally Posted by WFruit

I'm inclined to agree with Jeff that you probably have a bad lens batch. Given that Essilor ran out of polarized lenses and was scrambling to get more in this past summer, I'm willing to bet that some slid through QA that maybe shouldn't have.

Ooh, that is something to think about isn't it? i'm going to have to be even more on point with my inspections. I have no doubt you are right. I can't change who provides our lenses but I have control over the quality of the product I dispense to the pt.

**Darryl Meister** · 11-05-2010, 12:39 AM

When you rotate (not just tip) the lens, does the line rotate with the lens? Or does it remain vertical?

Best regards,
Darryl

**drk** · 11-05-2010, 01:07 PM

I've had this happen in a single lens.

The "line" is the sun (or a signficantly bright light source), and it is somehow diffracted or whatever by the polarization filter.

Has to be the polarization filter, since this never happens in non-polar.

I think bad batch.

**Darryl Meister** · 11-05-2010, 01:18 PM

Still, since the easiest way to produce a line image of a circular or point object is through cylinder power or a toric surface, it would be interesting to know whether the line twists when the lens is rotated.

The blue color is also interesting. Diffraction could create a dispersive spectrum, but other interference effects sound more likely, which could also form a linear band. Of course, simple absorption is also a possibility. Wish I could see the actual lens.

Best regards,
Darryl

**Dlls218** · 01-23-2011, 09:19 PM

I've seen this happen in SV also. I actually have a tray with lenses sitting in it right now with this problem. Ordered new lenses to see if they come in different. Glad to see someone else has experienced this also.