Cross like pattern in LCD display, what is it?

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D3Pixel
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Cross like pattern in LCD display, what is it?

Post by D3Pixel » 06 Oct 2018, 07:30

Hi

First post here, hopefully this forum looks like it has some clever bods in it. so can anybody explain this strange pattern, In the red box you can see a faint repeating pattern of + like marks. Nobody has yet figured out why it is there.

Image

The only info we have on this panel is as follows:
We use customized low persistence liquid (CLPL) display.
CLPL is a new patented display tech we developed with our partner for VR specifically.
CLPL display featured with less liquid respond time and higher refresh rate. We have completely eliminated ghosting and improved brightness with the CLPL display. CLPL tech is on the same level with OLED in VR era. There are only minor differences in color contrast/temperature between CLPL and OLED. Also, CLPL can reach higher PPI/PPD with the same cost.
Our co-founders have over 20 years experience in display era, including many years in VR. Some of the core team members come from display industry and maintain close relationships with display suppliers. That's one of the reasons why we care about visual so much.
This LCD panel is used on the Pimax 5K+ VR headset, the same artifact is not visible in their different 8K panel. Apparently this pattern is most visible when watching movies where there is little camera movement and red/orange backgrounds make it more visible. A bit like a 2nd SDE :/

Many thanks for any help.

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Re: Cross like pattern in LCD display, what is it?

Post by Chief Blur Buster » 07 Oct 2018, 15:25

I think it is simply aliasing effects -- nyquist factors of very sharp non-anti-aliased imagery.
There might be a case of too-little antialiasing versus too-much antialiasing.

I notice that for the right hand image, they're not doing any subpixel rendering, which would make the clarity even better. So, they're currently shortchanging the image clarity (At the moment). Hopefully better firmware/drivers will allow a good subpixel-scaling algorithm to fully utilize the 8K

I haven't looked closely as I don't have the headsets, but from a YouTube freezeframe, that is the impression I got.

Further tuning (and firmware/driver upgrades) could enable fine-tuneable scaling algoirthms that properly takes advantage of subpixel mapping that also sharpens things a bit while decreasing the color-fringing artifact (yellow, cyan, magenta around the circle on the right-hand image).

You know, like fine-tuning Microsoft ClearType to be as sharp as possible, but without creating color fringing. This is often done for de-bayering RAW images (from camera sensors) into regular displays. But the exact same thing can be done to non-standard pixel matrixes. The exact same thing is already done by smartphone manufacturers on high-quality PenTile displays, but Pimax appears to have not properly sub-optimized their subpixel scaling algorithm. So the Pimax could be twice as sharp with some optimizations and a very good scaling algorithm.

The workflow should be:

GPU processing -> GPU antidistortion (barrel/fisheye pre-compensation, chromatic aberration pre-compensation) -> Subpixel scaling/remap algorithm -> Perfect 1:1 map to the odd subpixel layout

But what seems to be done is currently crappy-looking non-subpixel-aware scaling. Even if GPU is rendered at a lower resolution, it could be done even better than what I see in that freezeframe above. Perhaps it's just a configuration issue, but sometimes display makers b0rk a missed opportunity of "sharper-by-good-subpixel-scaling-algorithm".
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D3Pixel
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Re: Cross like pattern in LCD display, what is it?

Post by D3Pixel » 07 Oct 2018, 15:39

Hi there

Many thanks for taking the time to reply!

Yeah they seem to be improving the algorithm's in each firmware release.
The main thread about this on their forum is here: http://forum.pimaxvr.com/t/dots-on-the- ... en/8730/80
Which may show the problem better than the image I linked?

Also it seems a Pimax employee has responded with a slightly confusing answer now...
these dots on panel aim to enhance the contrast of colors. but they're invisible in 99% scenarios. I think it can be improved by some color/gamma/brightness fine tuning. Maybe someone is more sensitive to this than others, but we do hear rare complaint about this. I even don't recognize this dots when I play the Pimax 5K+ hundreds of hours. Anyway, we're beware of this, and will try some improvement solutions later on.
But I have no idea how markers in the panel or whatever they are adding can be used to increase color contrast (assuming they mean saturation). There is always the chance of a language barrier at play when talking to Pimax.

With the new info, do you still think it is aliasing related?

It looks like this kind of pattern:

Code: Select all

............+........................+........................+........................
........................+........................+........................+............
And thanks again.

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Re: Cross like pattern in LCD display, what is it?

Post by Chief Blur Buster » 07 Oct 2018, 21:47

Oh!
Now I understand.

Image
(contrast enhanced and enlarged)

You're talking about those instead of the other artifacts I see at the objects.

Sorry, was not seeing the correct tree in the forest of trees...

Unfortunately, I think those are probably manufacturing related -- it looks as if they may be some kind of attachment points for the LCD color filters to the LCD panel. That particular defect looks mechanical/physical. Maybe, maybe not -- I'm not 100% sure but that part is definitely not aliasing/antialiasing related. Ultra-high-DPI displays are very prone to microscopic defects that becomes macroscopic with magnification lens (e.g. VR headsets).

(Nontheless my earlier posts stand about different artifacts such as color-fringing artifacts at the curves of the circles -- these can be massively sharper if using subpixel-geometry-aware subpixel scaling algorithms like modern OLED smartphone screens now do -- aka a screen-panel version of a camera-sensor debayering algorithm for nonstandard screen subpixel geometries -- to scale very sharply without color fringe or fuzzing artifacts -- basically you're remapping an RGB framebuffer of a GPU to a subpixel geometry, maximizing luma sharpness and removing aliasing effects. There's does not seem to be any of that occuring in the Pimax scaling)
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D3Pixel
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Re: Cross like pattern in LCD display, what is it?

Post by D3Pixel » 08 Oct 2018, 03:30

I did wonder :)

Ok thanks for the help. I hope I can not see those + during normal use. One of the testers can see them which is worrying.

The other issues, as the Pimax is already reported to be very good in comparison to whats out there now, this means it can only get better I guess :D

Thanks

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Re: Cross like pattern in LCD display, what is it?

Post by Chief Blur Buster » 18 May 2022, 15:31

carlosboyd wrote:
18 May 2022, 15:17
Hey guys I am noticing a strange artifact on my Asus 1080p LED-LCD

it is like a screen door effect, but it is more like a diamond crosshatch pattern, and it only reveals itself when there is either slight motion of the element on the screen, or

and this is the strange part...

when I move my head from side to side in front of my monitor at a distance of about 12 inches, I can clearly see a diagonal crosshatch grid pattern.

what am I seeing, is it a problem with my monitor or something inherent to LED-LCDs?

it seems to be connected to some kind of motion blur, for example when I play Diablo 3, if there is some gold on the ground and the screen is panning, the "150 gold" or whatever becomes very blurry, its not like traditional ghosting, it's more like distortion, and it's coming from the same diamond crosshatch pattern.

Does anybody have any idea what this could be
See viewtopic.php?t=3629

I think it's an "inversion artifact".

Image

This is not the same thing as the issue in this thread.
I may split this thread to a new thread.
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Forum Rules wrote:  1. Rule #1: Be Nice. This is published forum rule #1. Even To Newbies & People You Disagree With!
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  3. ALWAYS respect indie testers here. See how indies are bootstrapping Blur Busters research!

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