Polarisation experiments
So those are 3d glasses? given your phones are LCD, your glasses must be circular polarised. If they were linear you'd probably see blackness on the phone screens at the appropriate angle.
The way they help you see 3d, is that the 3d screen projects two different images, one left circular polarised, the other right circular polarised. One side of those glasses filters left but keeps right, the other vice versa, to create the 3d effect.
I still don't understand why they are creating that interesting light show though!
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Seagull Looking at a Moto G4 with polarized glasses shows it's vertically polarized. But with a tempered glass screen protector on it looking with the glasses shows a rainbow moire as I rotate but no blackness or brightness change...just color changes. Looking at an iPhone 6 with no protector dims as you rotate to 90deg but only about 50% and never blacks out. Weird.
if the plastic sheeting has converted the linear polarisation of the LCD to circular, then a linear filter cannot filter all the light. Circular light is oscillating along both the X & Y axis. Your linear filter can only block one of those axes at a time. You can block the X, but you'll still see the Y. You block the Y, you can still see the X.
Those screen protectors are doing something interesting to the light, makes me wonder if that's why some people find screen protectors help. Can't remember the user name, but there's the chap who swears by his skinomi matte protector, but doesn't benefit from any other.
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Seagull Help me understand how a clear, flat film can circularly polarize? I get how slits can make something linearly polarized. I don't get how a flat sheet could start light into a spiral. In my mind even if the slits were arcs or spirals the sheets would just come out in those shapes linearly like an old PlayDoh shape maker as tubes or arcs...not spinning. What makes the light start in a spiral?
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Seagull but there's the chap who swears by his skinomi matte protector, but doesn't benefit from any other.
That's ensete
Also, I see you use Galaxy S3 Mini Seagull that has OLED display? Do you suspect polarization has changed in OLED panels recently?
Interesting is the Essential Phone which someone reported usable on here might not have this polarization? https://old.reddit.com/r/essential/comments/74nkbz/type_of_polarizer_the_screen_uses_can_you_see_the/
Someone here says matte screen protector "cancels out" the polarization: https://old.reddit.com/r/Android/comments/4h7qwj/for_those_curious_how_the_htc_10_looks_through/
My experiences with OLEDs has been quite inconsistent. But I do not think the polarisation has changed. It seems that PWM in OLEDS affects me a lot, despite not affecting me in other devices (I have an LED LCD TN laptop which uses low frequency PWM that I can use ok).
I think the reason I could use the S3 mini was its small size, and favourable PWM (not tested though), but I still can only look at it for a few minutes before pain develops. All the other samsung devices have been much worse, older or newer, I assume due to their aggressive PWM.
One reason I suspect polarisation is a problem for me in general, is that even completely PWM free OLED phones like the LG Flex 2, and Lumina 650 cause me discomfort. But to a much lesser extent than the others.
I create this highly speculative theory.
Polarization even if is not the main reason of eye strain can have influence to some people.
To our eyes:
No polarization > 45° polarization > 1 axis polarization > circular polarization.
Maybe for people with eye convergence circular polarization might be the worst. Or even vertical/horizontal polarization.
Or has nothing to with. The most modern displays are using circular polarization and polarization might just be a form that goes along the development of new displays. 45 degree was older tech, so better. But the main factor here is the old tech not polarization.
hpst
"A waveplate or retarder is an optical device that alters the polarization state of a light wave travelling through it. Two common types of waveplates are the half-wave plate, which shifts the polarization direction of linearly polarized light, and the quarter-wave plate, which converts linearly polarized light into circularly polarized light and vice versa.[1] A quarter-wave plate can be used to produce elliptical polarization as well."
I am not sure your 3d glasses are appropriate to test whether something is linear to circular polarsied, as they themselves are circular polarised. Might be wrong, but I think its a lot easier to interpret what you see with a linear polarised filter.
With a linear filter, if rotating makes the screen go black, the screen is linear polarised. If the screen dims but does not blacken, its circular polarised.
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Seagull It's the same thing. Sunglasses are usually linear polarized. 3D glasses just react with rotational polarization. With vertical or horizontal dont do anything.
I have both glasses, 3D and linear polarized. They only react to their specific polarization.
There is also eclipse polarization, altough i dont know if it's used in displays.
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https://en.wikipedia.org/wiki/Retinal_birefringence_scanning
Retinal birefringence scanning
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Retinal birefringence scanning
Medical diagnostics
Purpose detect central fixation of the eye
Retinal birefringence scanning (RBS) is a method for detection the central fixation of the eye. The method can be used in pediatric ophthalmology for screening purposes. By simultaneously measuring the central fixation of both eyes, small- and large-angle strabismus can be detected. The method is non-invasive and requires little cooperation by the patient, so that it can be used for detecting strabismus in young children. The method provides a reliable detection of strabismus[1] and has also been used for detecting certain kinds of amblyopia.
Retinal birefringence scanning uses the human eye's birefringent properties to identify the position of the fovea and the direction of gaze, and thereby to measure any binocular misalignment.
Principle
Birefringent material has a refractive index that depends on the polarization state and propagation direction of light.[2][3] The main contribution to the birefringence of the eye stems from the Henle fibers. These fibers (named after Friedrich Gustav Jakob Henle) are photoreceptor axons that are arranged in a radially symmetric pattern, extending outward from the fovea, which is the most sensitive part of the retina. When polarized light strikes the fovea, the layer of Henle fibers produces a characteristic pattern, and the strength and contrast of this pattern as well as the orientation of its bright parts depend on the polarization of the light that reaches the retina.[4] An analysis of this pattern allows the position of the fovea and the direction of gaze to be determined.
Binocular retinal birefringence has been used for diagnosing strabismus (including micro-strabismus) in young children, and has also been proposed for diagnosing amblyopia by detecting strabismus and by detecting a reduced fixation accuracy.[5]
Limitations
However, also birefringent properties of the cornea and the retinal nerve fiber layer (RNFL) are sources of birefringence.[6] Corneal birefringence varies widely from one individual to another, as well as from one location to another for the same individual,[7] and can thus confound measurements.
http://grantome.com/grant/NIH/R01-EY012883-02
The fovea of the eye is surrounded by a distinctive pattern of birefrefringent fibers that change the polarization state of transmitted light.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4528539/
The fovea is the specialized, most sensitive region of the
retina that is aimed at the object of regard during fixation. It
is surrounded by a radial pattern of birefringent Henle fibers,
fibers that change the polarization state of light that passes
through them.
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.818.1110&rep=rep1&type=pdf
We suggest that when Fresnel’s laws are applied to the unguided oblique rays, that the cylindrical geometry of the blue cones in the fovea along with their distribution induces an extrinsic dichroism and could explain why the human eye is sensitive to polarization.
We have also found that, surprisingly, the rotating pattern is more regular and symmetrical with one of our two eyes around a more circular blue cone-free area, the dominant eye. Our results suggest that the polarization sense can provide important information in many areas that remain to be explored.
The short-wavelength sensitive blue cones seem to play a crucial role. We will perform most of our in vivo tests with only blue light, leading to contrasted blue-dark brushes appearing in place of the blue–yellow brushes observed in the presence of white light, as confirmed later by our model.
https://www.sciencedirect.com/science/article/pii/S0042698910003433
There seems to exist a triangulation between Blue light-polarization-strabismus (Convergence)
So I got my first polarisation filter today. Linear polariser camera lens and have been playing around with it.
I have found that all the smartphones I have which use glass screens are linear. Those which use plastic screens are elliptically polarised. The application of a cheap plastic screen protector on a glass screen produces elliptical polarisation.
Been buying tools for phone surgery, so hopefully in a few days/weeks I might be able to remove the polarisation layer from an OLED phone and see if I find it more tolerable.
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Seagull How do you know is it eclipse polarized? How can you diferentiate between circular and eclipse?
http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/polclas.html
If it dims but does not blacken whilst rotating a linear filter, its elliptical. Its difficult to explain why without giving a trig lesson.
Linear polarised light is light which only oscillates on one axis.
Circular polarised light oscillates on two axes 90degrees apart.
If you plot that on an X-Y graph over time it draws a circle.
Now if one of the two waves comprising circular polarised light is bigger than the other it won't draw a circle, it will instead draw an ellipse. Producing true circular polarised light is actually quite tricky because the separated waves have to be at the exact same magnitude.
Bringing this back to using a linear polarising filter to detect elliptical polarisation. At some angle it will block the smaller wave, 90degrees later it will block the larger wave but let the smaller one through. So as you rotate the filter it will dim a bit but never blacken for elliptical polarisation as one the waves is always passing through.