Smears on a VA LCD Screen
Intro
I was working on a Huawei MateView GT(ZQE-CBA) LCD monitor in school library when I noticed some smears on the screen when scrolling, shown in Figure 1.
After searching I got to know that this phenomenon originates from the drawbacks of vertical alignment LCD screens.
Theory
In VA LCD screens, liquid cryscal molecules are aligned vertical to the surface, as suggested in the name; brightness of pixels can be changed by changing the tiltness of molecules, which is done by applying different voltages of electric fields to the molecules. This results in a very high contrast ratio, thanks to its low residual retardation in the field-off state.
To increase response speed, manufacturers tend to “overdrive”(OD) by applying higher voltages. However, this solution results in another defect that molecules will turn more than desired angle, resulting in smears when displayed images are changed rapidly.
Solution
An official support article of Huawei points out that it’s generally best to set image > OD to Level 2 to reduce this effect. It’s indeed better after adjusting it from 4 to 2.
