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Zero Pixel Inspection

AGDisplays Zero Pixel Inspection Service

This service is for customers who have a zero fail pixel standard. AGDisplays uses a meticulous objective visual verification process to ensure your quality standards are met and that LCD pixel defects are not present in your products. We receive panels from the OEM before they reach the customer and we verify that your zero-pixel specifications are being met. If the panel fails OEM specification grade, we perform an exchange for panels that are standard or above standard for your industry.

AGDisplays employs a comprehensive training program so your units are in the hands of Technicians who expertly handle units like yours every day. Our Technicians and Inspectors use best practices in managing testing and inspections.

Customers may send LCD panels directly to AGDisplays for inspection. We inspect panels for hot, stuck dead pixel and evaluate LCD quality standards. We confirm and document our findings for verification purposes.

Pixel Defects

There are thousands—if not millions—of pixels in every LCD panel. A panel with 1080x1920 contains 2,073,600 pixels. LCDs are found in a wide range of consumer and industrial applications. You will know these products as smart phones, tablets, high resolution computers, televisions and the like. Business applications range vastly from medical equipment, to airline entertainment systems and cockpit applications, to indoor and outdoor digital signage.

With so many pixels packed into the incredibly bright and colorful LCD technologies, there are bound to be a few dud pixels. Even turning on a brand new screen, a user may see a dead spot here or there. When an LCD is manufactured, it may not come off the production line with 100% pixel defect free.

There are a few different types of pixel defects: dead—hot and stuck pixels—which display differently on a panel. So what exactly are dead, hot and stuck pixels? Let’s break them down for a better understanding.

Dead pixels always appear black; these are caused by transistors in the electrodes that are stuck off. No light passes through the layer, causing the black appearance. Dead pixels are found by displays solid colors on the screen and meticulously inspecting the screen for holes or missing spots. These are usually caused by a manufacturing defect and are not able to be fixed.

Hot pixels appear as if they are “on,” they always look white; they are caused by transistors in the electrodes that are stuck to appear as if they are always on, shining bright on your display. A hot pixel might be referred to as a stuck pixel, since the underlying factor is that the pixel(s) are stuck on.

Stuck pixels are a generated when one or two of the sub pixels (red, blue, green) remain on or off. The look of a stuck pixel may vary, since it depends on which sub pixel is stuck. It appears as a bright dot of color and they are most noticeable when the screen is dark, or black. The good news is, stuck pixels are often able to be corrected. If stuck pixels aren’t corrected, eventually they turn into dead pixels.

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Display Manufacturer Standards

Dead pixel policies vary from manufacturer to manufacturer. Many have created a grading system to categorize the variations in pixel quality from LCD to LCD. Even ISO 13406-2 guidelines specify an acceptable amount of pixels by display category; and each industry has different standards in which pixel defects are acceptable. Many expect LCDs to have absolutely zero dead pixels.

ISO 13406-2 Pixel Fault Classes, as indicated from Wikipedia:

Definitions:

  • Type 1: hot pixel (always on, color is white)
  • Type 2: dead pixel (always off, color is black)
  • Type 3: stuck pixel (one or more sub pixels (red, blue or green) are always on or off).

Definition of Pixel Fault Classes – Maximum number of faults per million pixels

Class Type 1 Type 2 Type 3 Cluster with more than one type 1 or type 2 faults Cluster of type 3 faults
I 0 0 0 0 0
II 2 2 5 0 2
III 5 15 50 0 5
IV 50 150 500 5 50

LCD manufacturers have created their own grading system to distinguish between pixel quality per panel.

  • Brand new Z grade (AUO grading system)
    • Zero pixel defects- not even 1 pixel can be dead.
  • Brand New A grade (all other manufacturers)(P Grade for AUO)
    • (1,3,3)- 1 sub pixel can be out in 1 sector up to 3 pixels can be out (these are never noticeable to the naked eye)
  • Brand New A minus grade (N grade for AUO)
    • (3,3,5)- up to 3 sub pixels out in 1 sector
  • Brand New B grade
    • (3,5,7) Up to 7 bad sub pixels

What is Pixel Pitch?

Pixel pitch refers to the density of pixels on an LED screen. It is sometimes called dot pitch or pitch. Pixel pitch is measured in millimeter by the distance from the center of one pixel to the center of the pixel adjacent to it. The smaller the distance means there are more pixels in an LED cluster, thus, the higher the resolution of the display

Pixel pitch values influence the optimal viewing distance for a display. If you have a higher pixel pitch, and your viewer is too close, the picture will be grainy and individual pixels are (undesirably) viewable to the user.

With lower pixel pitch values, your display reaches a higher quality of picture display, allowing for smoother, crisper lines and finer details. Increased pixel density is not ideal for all applications; it is generally best for close viewing distance. The longer the viewing distance, the high pixel density does not have many visual benefits and might simply just increase the cost of the display.

By determining the best viewing distance for your display and application, you will be able to select the best value for your LED screen. The LED industry uses three methods to figure out a good viewing distance:

  1. 10x Rule—this is a shorthand method for calculating an approximate estimate of the Visual Acuity Distance. The calculation is: Pixel Pitch x 10 = Approximate Viewing Distance in Feet
  2. Visual Acuity Distance –also known as retina distance, this is a formulated calculation of the distance a person with 20/20 vision must move away from an LED screen to see a coherent image that is not pixelated. The calculation is: Pixel Pitch x 3438 = Visual Acuity in Feet.
  3. The Average Comfortable Viewing Distance – this is an estimate of what would be a comfortable viewing distance for most people. This is a subjective estimate and will take into account variables like a person’s eye sight, resolution of content and type of content.

It is also important to note pixels per inch (PPI), which is simply how many pixels you would find in a single square inch on a display. All pixels are not created equally, however; pixels are different sizes on different sized displays. PPI depends a lot on the resolution of your screen.

To find your display’s PPI, you will need your display’s diagonal size in inches and the resolution of the screen. Use the chart below to find your PPI already calculated for you; if it’s not on the chart, the equation is as follows:

ppi = (√(w²+h²))/d

ppi is the pixels per inch; w is the width from the resolution; h is the height from the resolution; d is the diagonal size of the screen in inches.

Size (in) 8K UHD (7680x4320) 4K UHD (3840x2160) Full HD (1920x1080)
145 60.770 30.385 15.192
110 80.106 40.053 20.026
85 103.666 51.833 25.917
84 104.900 52.450 26.225
80 110.145 55.073 27.536
75 117.488 58.744 29.372
70 125.880 62.940 31.470
65 135.564 67.782 33.891
64.5 136.614 68.307 34.154
60 146.860 73.430 36.715
58 151.925 75.962 37.981
56.2 156.791 78.395 39.198
55 160.211 80.106 40.053
50 176.233 88.116 44.058
46 191.557 95.779 47.889
43 204.922 102.461 51.230
42 209.801 104.900 52.450
40 220.291 110.145 55.073
39 225.939 112.970 56.485
37 238.152 119.076 59.538
32 275.363 137.682 68.841
31.5 279.734 139.867 69.934
30 293.721 146.860 73.430
27.8 316.965 158.483 79.241
27 326.357 163.178 81.589
24 367.151 183.576 91.788
23 383.114 191.557 95.779
21.5 409.843 204.922 102.461
17.3 509.343 254.671 127.336
15.4 572.184 286.092 143.046
13.3 662.528 331.264 165.632
11.6 759.623 379.812 189.906
10.6 831.286 415.643 207.821
9.6 917.878 458.939 229.469
5 1762.326 881.163 440.581
4.8 1835.756 917.878 458.939
4.7 1874.815 937.407 468.704
4.5 1958.140 979.070 489.535

What is Resolution?

In an LCD screen, resolution is the number of pixels contained in a display monitor. Resolution is represented as a pair of numbers indicating the number of pixels vertically and horizontally, such as 800x600. Image sharpness is determined by the resolution as well as the size of the display. A smaller monitor with a resolution of 800x600 will have a better resolution than a larger monitor with the same 800x600 resolution.

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Resolution Chart

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