Help blocking Plano polarized lenses

[s-man-optiker]

Hey guys, gotta question... when blocking my plano polarized lenses I'm viewing an lcd screen and turning each lens until the screen appears black then blocking on that axis. Is that the correct way?

[IC-UC]

No. You should be seeing clear through both. If the screen is black it means the palarising is off between the 2 substrates.

If you want to make sure that your LCD screen has the polarising in the right direction (which I hope and believe it should be) then try using a pair of plano polarised sunglasses as reference.
If you put the sunglasses on and you can see the screen, then you should mark up every lens only when the 2 axis give you a clear image.

Hope this helps.

[LilKim]

Most plano polarized lenses come with little clear spots at the sides, where the polarized layer is missing, which indicates the correct axis you're supposed to be blocking at.

[Ginster]

Most plano polarized lenses come with little clear spots at the sides, where the polarized layer is missing, which indicates the correct axis you're supposed to be blocking at.

Yes, they are called witness marks all polarized lenses have then with or without power. When you have cyl. power and an axis, and spot the lens, the axis should always be in reference to the witness marks.

Great Question, Hope I helped. Ginster:)

[Judy Canty]

Many polarized lenses have engraved circles like the ones found on PAL's to find the 180 axis.

[chip anderson]

If you have no reference marks one can find a level flat reflective surface, as a white or glass table top, put a light behind it and turn and mark the polarized lens where the glare disappears.

Next method find a polarized lens with the axis marked, turn the unmarked one in front or behind it until the light disappears, now you have the unmarked one exactly 90 degrees from the marked one. Mark axis accordingly.

Chip

[Leo Hadley Jr]

If you have no reference marks one can find a level flat reflective surface, as a white or glass table top, put a light behind it and turn and mark the polarized lens where the glare disappears.

Chip

Yep, thats what I used to do, except I used the glare off the tile floor.

[Wes]

tend to be polarized at 135 degrees. If your polarized lens is blocking the light from the lcd while held horizontally, then your polarizing lens filter is at 45 degrees. th polarization filters need to both be oriented at 90 to effectively block reflected glare from horizontal surfaces. If you're using some other type lcd, all bets are off.
Wes