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A defective pixel or a dead pixel is a pixel on a liquid crystal display (LCD) that is not functioning properly. The ISO standard ISO 13406-2 distinguishes between three different types of defective pixels, [ 1 ] while hardware companies tend to have further distinguishing types.
The standard lists four classes of devices, where a device of a specified class may contain a certain maximum number of defective pixels. Three distinct types of defective pixels are described: Type 1 = a hot pixel (always on, being colour white) Type 2 = a dead pixel (always off, meaning black) Type 3 = a stuck pixel (one or more sub-pixels ...
A display with only a few defective pixels may be unacceptable if the defective pixels are near each other. LCD panels also commonly have a defect known as clouding, dirty screen effect, or, less commonly, mura, which involves uneven patches of luminance on the panel. It is most visible in dark or black areas of displayed scenes. [144]
The cause of LCD image retention is different from phosphor aging as in CRTs, but the visual phenomenon is the same: uneven use of display pixels. Slight LCD image retention can be recovered. When severe image retention occurs, the liquid crystal molecules have been polarized and cannot rotate in the electric field, so they cannot be recovered.
This results in extremely slow response times and poor voltage control. A voltage applied to one pixel can cause the liquid crystals at surrounding pixels to untwist undesirably, resulting in fuzziness and poor contrast in this area of the image. LCDs with high resolutions, such as large-screen LCD televisions, require an active-matrix structure.
This is generally the native resolution—with, therefore, square pixels—of standard 17" and 19" LCD monitors. It was often a recommended resolution for 17" and 19" CRTs also, though as they were usually produced in a 4:3 aspect ratio, it either gave non-square pixels or required adjustment to show small vertical borders at each side of the ...
LCD crosstalk is a visual defect in an LCD screen which occurs because of interference between adjacent pixels.. Owing to the way rows and columns in the display are addressed, and charge is pushed around, the data on one part of the display has the potential to influence what is displayed elsewhere. [1]
A TFT LCD is an active matrix LCD, in contrast to passive matrix LCDs or simple, direct-driven (i.e. with segments directly connected to electronics outside the LCD) LCDs with a few segments. TFT LCDs are used in television sets , computer monitors , mobile phones , video game systems, personal digital assistants , navigation systems ...