Pixel Fault Classes

[#1]

Pixel Fault Classes

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Definition

The production of high-quality TFT displays is a complex process. Displays with zero pixel error are very rare. Single defective pixels often do not catch the eye, especially if the pixels are not a total fade-out.

Because of this technological complexity in the manufacturing process, the manufacturers do not guarantee fault-free TFT panels, but expect the acceptance of a certain fault tolerance. That means approximately 1 pixel per million (1 ppm) can be displayed on the display brighter or darker. This does not affect the device performance. Therefore, the produced TFT panels are distinguished in pixel error classes.
These defect classes are subject to the ISO 9241-307 standard.

The table below shows the maximum number of allowed defects (per type) per 1 million pixels.

Error class ISO 9341-307	Old error class ISO 13406-2	Error type I Constant shining pixel	Error type 2 Constant black pixel	Error type 3 one defect sub pixel, constant shining	Error type 3 one defect sub pixel, constant black
0	I	0	0	0	0
I		1	1	2-n n ∈ [0;2]	2*n+1 n ∈ [0;2]
II	II	2	2	5-n n ∈ [0;5]	2*n n ∈ [0;5]
III	III	5	15	up to 50	up to 50
IV	IV	50	150	up to 150	up to 150

The ISO 13406-2:2001 standard has been withdrawn and revised by the ISO 9241-302, 303, 305 and 307:2008 standards.

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References

1. Wikipedia: https://en.wikipedia.org/wiki/ISO_9241#ISO-9241-302,_303,_305,_307:2008_pixel_defects
2. Wikipedia: https://en.wikipedia.org/wiki/ISO_13406-2