I'm at work and I'm looking at one right now. Almost every LCD on ebay says "no dead pixels". So what causes these? Are they manufacturing flaws? Are they caused by abuse, such as heat, cold, rapid motion, or what? Or are they just some type of random phenomenon? Anybody know? I'm about to invest in a very nice panel and I'm a little concerned.
A dead pixel occurs due to the failure of a transistor that controls the amount of backlight shining through a given pixel.
There are a number of possible visible defects this results in; "lit" pixels that appear as white, red, green, or blue (or combination thereof) pixels on an all-black background, or a missing or dead pixel that appears on an all white background.
Lit pixels occur more commonly then missing/dead pixels - they occur when a transistor shorts.
The reason LCDs are so expensive, relative to CRTs is because due to their operation it is impossible to test for dead pixels until the display is completely constructed. Also, considering the number of dead pixels in a typical LCD, they exhibit superb defect rate: for a 15" LCD there are 2,259,296 pixels (1024x768x3). If twenty of these pixels fail, the defect rate is only 0.0008%.
There are a number of possible visible defects this results in; "lit" pixels that appear as white, red, green, or blue (or combination thereof) pixels on an all-black background, or a missing or dead pixel that appears on an all white background.
Lit pixels occur more commonly then missing/dead pixels - they occur when a transistor shorts.
The reason LCDs are so expensive, relative to CRTs is because due to their operation it is impossible to test for dead pixels until the display is completely constructed. Also, considering the number of dead pixels in a typical LCD, they exhibit superb defect rate: for a 15" LCD there are 2,259,296 pixels (1024x768x3). If twenty of these pixels fail, the defect rate is only 0.0008%.
I'm pretty sure that it cannot be fixed.
It is not that big of a deal though.. my panel has about 4 dead pixels on it that I can see.
I think there are 2 that are stuck on and 2 that are stuck off... it is hardly noticeable though. If anything it is harder to see it on the projection than it is on the screen.. granted I do not have a screen yet but against the wall you cannot see it.
As long as the dead pixels are not clustered together that is.
It is not that big of a deal though.. my panel has about 4 dead pixels on it that I can see.
I think there are 2 that are stuck on and 2 that are stuck off... it is hardly noticeable though. If anything it is harder to see it on the projection than it is on the screen.. granted I do not have a screen yet but against the wall you cannot see it.
As long as the dead pixels are not clustered together that is.
Thanks qeoffwa.
I'm making a $1200 projector, so a dead pixel or two is not something I'd be happy living with.
I'm making a $1200 projector, so a dead pixel or two is not something I'd be happy living with.
Pixels that are stuck on can be "fixed" by burning the transistor with a laser, thus turning them rather pemanently off. Instead of getting a permanent white pixel you can get a permanent black pixel basically.
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