Based on my experiences, i suspect polarisation may be a component of the eyestrain I experience. Namely, my good tolerance of plasma tvs, and poor tolerance of LCD and OLED screens, both of which use polarisation filters. I have devised two experiments, I have not yet decided which to try first. Firstly, I have discovered that the polarisation layer in OLED phones can be removed without damaging the OLED component. The polarisation layer is not necessary for OLED screens to work, but improves contrast. Removing the polarisation layer seems to be a skilled process that may take time and equipment to master, in addition to a few practise phones. It is also not clear just how bad OLED screen contrast is without the polarisation layer - the screen may be unusable in well lit areas. The second experiment is to buy a quarter-wave film. This polymer sheet when positioned correctly on a screen, like a normal screen protector, will convert linear polarised light into circular polarised light. I do not know if circular polarised light is better than linear. The filters are available here: https://www.edmundoptics.com/f/polymer-retarder-film/14827/ though there may be cheaper alternatives. I will keep you updated on progress.

Seagull how many kinds of polarization there are?

Seagull To make sure we are all on the same page re polarization on LCDs. Simplified (maybe...hope so)...in an LCD panel the backlight shines through the rear polarizer which "polarizes" the light so is all oriented on one plane like slits in window shades. Let's say vertical shades for this case so all light comes out in vertical planes. The liquid crystals are in the middle...then the colored pixels. In front of those is an opposite polarizer that blocks all light from coming through since the slits are horizontal and no vertical light can get past. Even with the backlight on this appears black as no planes of light can pass. The liquid crystals are turned by current to twist the light from vertical to horizontal to selectively let light through to the right colored pixels to make the images/colors/letters whatever and then out horizontally through the front polarizer's slits. Without the polarization layers the screen would be all white as everything would be fully lit. Some good visuals and maybe better explanations here: https://www.androidauthority.com/amoled-vs-lcd-differences-572859/ I have noticed no difference re strain on a painful device between horizontally or vertically polarized IPS displays (LG for example are horizontally polarized in front thus letting only horizontal waves through, and if you look at them with polarized glasses on they appear black since the glasses block horizontal waves so as to block light bouncing off a road in horizontal sheets causing glare, most others are vertically polarized and thus visible with said glasses on but black if you turn your head 90deg )...and TN panels which are polarized on a 45/135 angle which as I understand it is due to how they are made and not an intentional choice. I tried all sorts of panels in a Thinkpad and all of them hurt. I even had some pinkish film that came on one panel that seemed to cancel out the polarization which I don't understand since it if were simply an opposite polarizing film then it would have rotated the black area under glasses back to vertical as I understand it, but it did nothing to help strain regardless. I have noticed some LCD panel phones and tablets don't go fully black if you rotate the device around with polarized glasses on, just dim or change to some colorful moire so don't know what that's about and how some light is getting through the glasses at all at the opposite angles. On an intuitive note I ask myself why it would even matter if light coming from a display was polarized or not? The eyes can see light coming in from any angle and everything we see in life is because photons bounced off it and ended up in our eyes, and driving with polarized glasses isn't straining in general and they just eliminate glare, so why would polarized light from a display cause trouble? *Nevermind about my OLED questions, missed your explanation and also found this https://technology.ihs.com/509943/why-all-amoled-is-applying-polarizer-suppliers-of-amoled-polarizer-and-compensation-film-for-polarizer-technology-trend-of-amoled-use-polarizer

tfouto There are effectively three types. Linear polarisation is when light waves oscillate over one axis only. Picture an X-Y graph. Linear polarised light coming towards you will oscillate over 1 axis only, say the x-axis. Circular polarised lights oscillates over 2 axes, say the X and the Y axis, drawing a circle as it oscillates. Unpolarised light oscillates all over the X-Y graph. hpst Those are some interesting observations. I personally cannot use any IPS screens without developing migraines, but can happily use a few specific TN screens. So I am intrigued to hear they have different linear polarisation angles. Though, if polarisation angle were the only cause of my problems I might expect to get headaches whenever I tilt my head whilst using a TN. Your observations that some screens do not go entirely black when rotating a polarising film: I think this implies they have some level of circular polarisation already. From what I understand, this may be a natural property of some plastic sheets - I skimmed a paper outlining how a specific brand of overhead projector transparency was found to have some quarter/half wave plate activity. Or perhaps it was a design choice by using wave plate film. As I explained in the OP, OLED screens use polarisation to improve contrast against other light sources - ie to stop the screen looking washed out in sunlight. Turning up the brightness of an OLED screen to counter that is not ideal due to how rapidly OLEDs degrade. Hence the polariser solution. https://technology.ihs.com/509943/why-all-amoled-is-applying-polarizer-suppliers-of-amoled-polarizer-and-compensation-film-for-polarizer-technology-trend-of-amoled-use-polarizer This link explains the science of it. Reading it, it seems that OLEDs use circular polarising filters already. I will have to look out for a linear polarisation filter as first step to explore the polaristion of the devices I can and cannot use.

Seagull So the vertical or horizontal is when the device becomes completely black? The circular is when they changes hues? Like this: https://www.youtube.com/watch?v=tl_9Mj--tKk&feature=youtu.be And about this one? https://www.youtube.com/watch?v=lTzU4aXYgw0&feature=youtu.be

hpst As to why polarisation is a problem? no idea. I don't know of any reason why it would be an issue. It is simply the strongest common link between the devices I can and cannot use. We can hypothesise all day about what causes our problems, but its evidence that counts. If I can take an OLED phone that hurts my eyes, remove the polarising filter, and find it still hurts my eyes I will know with sufficient certainty that I am looking in the wrong place.

tfouto I don't know enough to say really, don't be deceived by my authoritative language style! I am writing up my doctoral thesis at the moment, so naturally everything else I write ends up in the same style. if you rotate a linear polarisation filter against linearly polarised light at some angle it will go black as your filter blocks out more or less of the polarised light. The colour effect in your first video, I don't know what is going there. The second video is unavailable for me. I'm buying some different polarisation films, so perhaps I will understand more what's going on in your first video if I can reproduce it.

Seagull You should have access now.

tfouto Do those phones have oled or lcd screens? do you know what the deal with the glasses is? I just bought both a linear and a circular polarising filter from ebay, so unless your glasses have some wave plate effect I should be able to reproduce what you are seeing.

Seagull Wouldn't using an opposing filter to cancel it out prove the same? Might be easier than tearing a phone down properly. I am fairly sure from reading that all LCD panel types are linearly polarized. Even a TN panel being at 45/135 is just how they position the polarizing layers as far as I can tell and isn't a result of the polarization coming our circular. Frankly I am having a hard time understanding circular polarization in relation to light, as it seems it needs a constant em field to keep it rotating? Linear just comes out the slits and that's that as it travels on in a plane. I'm old and physics courses were a long time ago. Your comment about plastic sheets bending the waves would make sense for my "pink sheet" example and why some screen protectors seem to alter polarization.

Seagull LCD's 1st video is Sony XZ 2 IPS LCD 2 video is HTC one M7 SLCD

Polarisation experiments

Seagull

tfouto

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.

tfouto

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.

tfouto

https://en.wikipedia.org/wiki/Retinal_birefringence_scanning

Retinal birefringence scanning
From Wikipedia, the free encyclopedia
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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)

Seagull

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.

tfouto

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

Seagull

tfouto

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.

tfouto

Seagull It also depends on the filter itself. With some sunglasses it almost dim everything, with other dim less. So it depends on the filter itself, the strenght of filter.

Where did you bought your polarisation filter?

Seagull

tfouto

I bought camera filter lenses from ebay. Both a linear and circular filter, though I only have the linear at the moment.

Using my LCD computer monitor as a reference, it doesn't quite block all the light, instead reducing the transmitted to a very dark blue

Quad43

Did polarisation work for anyone? If so, how? I notice iPhone 8 and polarised sunglasses are way better than without

Quad43

When I wear polarised Raybans, or even non polarised and used iPhone, it's certainly better

Mrak0020

Quad43 yep me too, slightly better.
Everything that have a capacity to scatter the light slightly helps. Like tpu screen protector, mentioned somewhere on this forum.

Mrak0020

Hi! To bring some new info to this thread, there's a post below from russian-speaking hardware forum ixbt.com
It is google translated so sorry for readability.
This guy wrote a post about specific monitor model.

There is a clever way of sharpening, patent WO1996007115A1 - Improved polarizer (improved polarizer). The polarizer consists of many small waveguide cones. Which allows you to improve viewing angles, contrast and sharpness!. The light from the monitor is not solid (scattered, as in real life), but thin rays (10-40% of the size of the subpixel). The brain is not able to distinguish these rays, but the eyes catch, which leads to their tension. Such cone polarizers in various configurations are now commonly used. I changed the polarizer from "improved" to normal - the eyes get tired much less. Without sharpening, the text looks unusual, you need to look a little closer, but the text itself looks like in a book, without unnatural clarity. But with an improved polarizer I can read from a meter, I see everything, although I shouldn't, it's too far and shallow. The eyes have to pay for such clarity. Oddly enough, in some people, their eyes react to increased clarity the other way around. I showed 2 monitors to my friend, the first one with a very sharp polarizer, the second one with a moderate one, so he said that the first one had a normal text washed in the second one. The Ya. Market is full of reviews about fuzzy text, I think that's why. In monitors where there is no sharpness adjustment in the menu, it remains intact. And the differences in clarity are due to different polarizers. Patent citations:
The present invention is advantageous to use because viewability around the normal to the plane of the liquid crystal device is improved and when viewed at high angle, the quality of the image is improved in that it exhibits better contrast and sharpness
One advantage of placing the polarizer element and the array of tapered waveguides in close proximity is that the distance between the liquid crystal display device elements (pixels) and the array of tapered waveguides is minimized which results in an image with greater sharpness, contrast, and color purity

Clokwork

This is extremely intriguing. I haven’t tried any form of polarized overlays or glasses with panels. I will be keeping an eye on this.

Mrak0020

Clokwork I tried a real polarizing film from another phone above the screeen (and then a different one, and then two together), and the difference is present but very subtle, less than with polaroids or at the same ĺevel.
I have my doubts whether another polarizing film can redirect enough already directed light.
I would try overlays that can drastically scatter the light or try few different polirizers instead of original one

Seagull

Not sure if I posted above, but I found gluing tracing paper to a screen protector, and then using it would both remove all polarisation and improve my tolerance of bad screens. Unfortunately though, it only improved my tolerance, never actually made a bad screen good.

Mrak0020

Seagull
Thank you for interesting idea!
I immediately tried tracing paper and have to say its effect is weak, sonewhere near or even less than my current set of screen filters, and I even don't see screen clearly but still feel its brightness.
But I have huge doubts about whether any tracing paper can depolarize the light completely when the slightest details of screen are visible.
Have you ever seen the screen without polarizing film? I suppose every screen is completely white, including oled's. No film means no image.
Below is what i found about the topic in some textbook. It is google translated from russian, again.
I believe you can get some depolarizing effect but not a total removal. This is why it makes sense to try different screen overlays or better to repolarize the light completely.

"Multiple light scattering by wax paper can be demonstrated as follows. Place the paper on the page of the book. With this, you can easily see black letters. If the paper is lifted one or two centimeters above the page, the letters will blur and become practically indistinguishable. To understand this example, assume that black light is falling on your eye from the letter, which is scattered by wax paper. Here is another experiment illustrating the scattering of light by wax paper. Take a flashlight and direct its beam through the wax paper to a surface. Gradually removing the fountain from the paper, observe the size of the light spot formed by the light that has passed through the paper."

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