Questions about LCD's and refreshing

[Frosteh]

OK so just wondering how LCD's work, do they refresh the whole screen at once, every single pixel changing colour at the same time, or do they scan a single line at a time like a CRT refreshing each pixel in turn. Or do they refresh in blocks or in some other manner.

I ask because we still get tearing on LCD's and most have a common refresh rate of 60Hz.

I understand we dont get the flicker like CRT's because they're constantly backlit, where as CRT pixels are only bright for a fraction of a second when being hit by the cathode ray and then tends towards black very fast giving a noticeable flicker at low refresh speeds.

It seems with time to change colour as low as 2ms in the case of some TN panels that refresh speeds of upto (1000/2 = 500 times a second) should theoretically be possible (if all pixels change at the same time)

Presumably they still actually scan across like CRT's do when refreshing.

 

[ToastyX]

They refresh like CRT monitors, from top to bottom. I was able to confirm this while doing lag tests. Here is a picture I took before:

 

[Frosteh]

Thats very interesting, thanks

I guess it's the only real explination, if they refresh all pixels at once we would not see image tearing.

I suppose that makes my next question: What component limits refresh rate in a LCD? It's not the response time of the pixels. Even with no flicker a refresh rate of more than 60hz is still desireable for various reasons.