What can you do to prevent or fix LCD Image Retention
First a few terms need to be defined.
Burn-In: With phosphor-based electronic displays non-uniform use of specific areas, such as prolonged display of non-moving images (text or graphics), can create a permanent ghost-like image of these objects or otherwise degrade image quality. This is because the phosphor compounds which emit light to produce images lose their luminance with use. This wear results in uneven light output over time, and in severe cases can create a ghost image of previous content.
Image Persistence / Retention: is similar in appearance to CRT burn-in. Unlike screen burn, the effects are usually temporary and often not visible without close inspection.
To create images, Liquid crystals bend in various ways to guide light to specific areas of the screen. If the image does not change for a period of time, the liquid crystals develop a memory and do not rapidly re-bend to another location. The result is a persistence or ghosting image. It is important to realize this this persistence is not permanent.
Pixel shifting: MicroTouch LCDs employ Pixel shifting as a way to combat persistence. Pixel shifting moves the entire image one pixel after a screen has been left static for any length of time. If the image remains static, the image is shifted back. This process repeats itself as long as the image remains static.
Pixel shifting does help, however, this process has it limitations and cannot prevent retention under all situations / conditions.
How to correct: Persistence will dissipate with time once the displayed image has changed; however this can be a slow process 36 to 48 hours. To speed up the recovery, alternating between full white and full black screens will exercise the liquid crystals and speed the recovery. Many screen savers allow you to alternate between such images. Also, many diagnostic tools have full color alternating patterns.