Luminous Landscape Forum

The Art of Photography => The Coffee Corner => Topic started by: Michael West on February 23, 2021, 01:37:33 pm

Title: Optical Questions I cant Fathom arise
Post by: Michael West on February 23, 2021, 01:37:33 pm: I noticed this optical anomaly in passing

The two layers of Glass...the side and rear windows of this automobile somehow distorted series of straight lines in a wave like fashion that i can not fathom.

Any Doctor Of Optics people in this building?

(https://i.ibb.co/QXgFqNk/optical-questions-arise-6213.jpg)
Title: Re: Optical Questions I cant Fathom arise
Post by: Eric Myrvaagnes on February 23, 2021, 07:53:23 pm: I suspect it's just wiggly glass, since it is curved. The windshield is probably much better optically, since it is used for almost all navigation, which the side and rear windows aren't.
Title: Re: Optical Questions I cant Fathom arise
Post by: Michael West on February 23, 2021, 08:42:14 pm: Quote from: Eric Myrvaagnes on February 23, 2021, 07:53:23 pm
I suspect it's just wiggly glass, since it is curved. The windshield is probably much better optically, since it is used for almost all navigation, which the side and rear windows aren't.

Thanks.
Title: Re: Optical Questions I cant Fathom arise
Post by: wcarlew on February 23, 2021, 10:56:14 pm: How old is the car, does it have a rear window defrost with the thin wires laminated to the glass?
Title: Re: Optical Questions I cant Fathom arise
Post by: degrub on February 24, 2021, 09:23:06 am: two possibilities - 1) a plastic layer for the heating element in the glass interior or 2) two layers of thermally annealed glass making up the glass-PVB-glass windshield. The thermal annealing is done in an oven with rollers for support. This causes slight waves that changes the refraction direction through the glass. Basically can create an visually disturbing image and cause people to get seasick when they look through while moving.

The image is also shot through two windows, thus 4 layers of annealed glass.
Title: Re: Optical Questions I cant Fathom arise
Post by: Michael West on February 24, 2021, 11:01:10 am: Quote from: degrub on February 24, 2021, 09:23:06 am
two possibilities - 1) a plastic layer for the heating element in the glass interior or 2) two layers of thermally annealed glass making up the glass-PVB-glass windshield. The thermal annealing is done in an oven with rollers for support. This causes slight waves that changes the refraction direction through the glass. Basically can create an visually disturbing image and cause people to get seasick when they look through while moving.

The image is also shot through two windows, thus 4 layers of annealed glass.
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Thank you, The regularly spaced horizontal lines to the right of the window are likely shadows produced by a heating element.
Title: Re: Optical Questions I cant Fathom arise
Post by: rabanito on February 24, 2021, 11:35:30 am: I was not aware that car windows are made of annealed glass.
Isn't it that annealed glass can break inconveniently?
Admitedly, I have no idea of car glasses
Title: Re: Optical Questions I cant Fathom arise
Post by: degrub on February 24, 2021, 01:57:18 pm: the PVB = polyvinylbuteral interlayer holds the glass fragments together to prevent flying shards.
Tempered glass will break into small cubes when impacted due to the capture of compression stress during manufacture.
It can be used for the side and back windows. Some use laminated glass instead.

The glass used for the windshield is likely annealed grade also called float glass. There is usually an etched grade mark on each piece of glass - AG = annealed, TG=tempered . if not there will be the several standards the glass is designed to meet indicated. AGC is a large OEM producer in the US.

here is a good overview for anyone interested -
https://auto.howstuffworks.com/car-driving-safety/safety-regulatory-devices/auto-glass.htm
Title: Re: Optical Questions I cant Fathom arise
Post by: rabanito on February 24, 2021, 02:57:41 pm: Thank you Degrub, I had very little idea :-)
BTW, then there are 6 layers of material in that photo between the camera and the straight lines?
BTW in my humble experience my car was broken in once in France, a side window.
There were small cubes everywhere, as you say it would occur with tempered glass.
Title: Re: Optical Questions I cant Fathom arise
Post by: degrub on February 24, 2021, 03:04:25 pm: it would depend. If they used tempered for the side and rear, then only 2 and the ripples are likely from the heater on the inside surface.
If they embedded the heater between the layers, then it would be AG glass with ripples possible on the glass surface from the roller support during fusion heating.
My guess it is the heater film causing the ripples that are showing up at the odd angle.

We preferred the TG grade laminated safety glass for the windows of our site guard shacks. However, when you combine two sets of laminated TG glass, you get the enhanced rippling effect and our guards were getting motion sickness when they stood up to look outside. We had to go back to the AG which has less of that issue.
Title: Re: Optical Questions I cant Fathom arise
Post by: rabanito on February 24, 2021, 06:07:52 pm: Quote from: degrub on February 24, 2021, 03:04:25 pm
We preferred the TG grade laminated safety glass for the windows of our site guard shacks. However, when you combine two sets of laminated TG glass, you get the enhanced rippling effect and our guards were getting motion sickness when they stood up to look outside. We had to go back to the AG which has less of that issue.

Haha! I remember some time ago one person got seasick while sitting in the rear while I was driving.
Everybody blamed my driving style. Maybe that was the issue. ???

:)
Title: Re: Optical Questions I cant Fathom arise
Post by: degrub on February 24, 2021, 08:40:32 pm: Some roads were just meant for manual shift ! ;D