How are polarization test cards created for proving polarized glasses?

LightningInAJar · Jul 23, 2023

I could swear I saw this topic in the forum in the past but haven't found it today. I was curious how polarization test cards are made to prove that a pair of glasses are polarized. Special ink or paint? What is that type of substance called or commonly used for? I'd love to use it for art. Does it require special paper medium? Anyone ever make printer ink cartridges with an ink invisible only without polarized glasses?

Baluncore · Jul 23, 2023

LightningInAJar said:

I was curious how polarization test cards are made to prove that a pair of glasses are polarized. Special ink or paint?

Chemistry could print a circular molecular polarizer, but how might you align a linearly polarized ink?

My guess is that a thin polarized film is laminated onto the test card, the same film as used to make polarized sunglasses.
https://en.wikipedia.org/wiki/Polarizer#Absorptive_polarizers
"Its current H-sheet form is made from polyvinyl alcohol (PVA) plastic with an iodine doping. Stretching of the sheet during manufacture causes the PVA chains to align in one particular direction".

LightningInAJar · Jul 23, 2023

I actually have a few small polarized sheets. Not sure if they're the right kind but will see.

hutchphd · Jul 23, 2023

LightningInAJar said:

I actually have a few small polarized sheets. Not sure if they're the right kind but will see.

The "right kind" to do what?

DennisN · Jul 24, 2023

LightningInAJar said:

I was curious how polarization test cards are made to prove that a pair of glasses are polarized.

I have no answer to your particular question, but in case you weren't aware of it, I just wanted to say that glasses can often be tested for polarization by looking with them at a screen (tv, computer etc) at different angles. I've noticed this since I often wear sunglasses

.

Regarding linear and circular polarization I just fetched two of of my polarizing filters (one linear, one circular) for camera lenses and tested them on my screen, and they both worked:

1. Linear polarizing filter (at different angles):

2. Circular polarizing filter (at different angles):

Baluncore · Jul 24, 2023

Screens are now often clad in a circularly polarized film. Incident light, say LHP entering, is absorbed on the first pass, so only RHP survives to be reflected. But the reflection reverses the CP hand, to make the RHP reflect as LHP, which is absorbed on the second pass through the filter. That process of reversal, also operates on multiple internal reflections, which is why you no longer see your reflection in your computer monitor.

Direct reflection from the front surface of the CP film is also reduced by a multi-layer coating of that surface, with quarter-wave thicknesses of impedance matching materials.

Vanadium 50 · Jul 25, 2023

It's done with polarizing film. How do I know? I asked Google. "how are polarized cards made" Zillions of hits,

You really should try Google sometime.

LightningInAJar · Jul 29, 2023

Vanadium 50 said:

It's done with polarizing film. How do I know? I asked Google. "how are polarized cards made" Zillions of hits,

You really should try Google sometime.

I did. I even asked a company that sells them. The sales guy had no idea.

Vanadium 50 · Jul 30, 2023

I guess Google just deliberately refused to give you the answer. Bad Google! Bad, naughty Google!

How are polarization test cards created for proving polarized glasses?

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