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.

            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.

                    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.

                            hpst

                            From what I understand it is not possible to unpolarise polarised light, or atleast deeply impractical. Turning linear into circular is the best I have seen so far. If you know of such a filter please let me know. Ideally, I want to try an oled without any polarisation.

                            Regarding circular light, remember light is both photons and waves at the same time. Light doesn't need any driving force to oscillate, it just does. As for the circular bit, two orthogonal sine waves draw circles over time, I don't know how to attach images, but there are few good ones on google images.

                            • hpst replied to this.

                                Seagull If you cannot unpolarize it then how is the plastic sheeting making a polarized display visible with polarized glasses 360deg? I had assumed it was twisting some of the light and diffusing it somehow.

                                    tfouto

                                    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!

                                        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.

                                          hpst

                                          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.

                                              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?

                                                  hpst

                                                  I can't, I have no idea either. Optics are weird.

                                                    Seagull With Polaroid glasses i can see HTC is vertical or horizontal polarized, in on position i can see anything, altough in the diagonal i still see that colored shape also presented on circular polarized.

                                                      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/

                                                              ryans

                                                              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.

                                                                  dev