E-ink readers (like a Kindle) has been out for years, but even now after several generations of the products, all of them still does a full-screen refresh to remove the ghosting.
I can't find the answer on the official e-ink website, however this question: Why does "flashing" prevent ghosting on E-Ink displays? does explained how E-ink works but still not anwsering my question:
Why is it necessary to refresh the whole screen?
Wouldn't it be enough to just refresh the part that wasn't empty (white) plus some "padding" (since a answer in the linked question mentioned that "However, each cell might be influenced by its neighbors as well as the applied charge.")
For example, when we read a book, it's very likely that some part of the screen will be always empty (like page margin, line margin, etc…) why can't those reigons be left out (like when you use the "Page Flip" function in Kindle PW2, only the small preview window gets refreshed and the rest part of the screen stays still)
EDIT:
@CL. reminds me in the comment section that no matter how much "padding" is added, the boundary between refreshed and unrefreshed parts is always there… So as long as a cell could be influenced by it's neighbors, this won't work – duh!
- But still, I think it would be nice to add a few padding to keep the ghosting away from interfering with new texts to keep readability without doing a full-screen refresh which I really, really hate.
So what's the technical difficulty to prevent this influencing between the cells? The latest generation of E-ink is "Carta" is introduced in CES 2013, no upgrade for two years already.
Best Answer
The simplest answer is also the most obvious. When issuing new information for the screen, deciding whether each and every pixel needs to change takes longer than issuing a complete refresh, and twice the memory. Both frames would have to be available simultaneously for comparison. This could be done in hardware with a purpose built buffer, but it's still additional hardware. Since it is not capable of real time video, and is so power efficient anyway, we can skip the step of making that decision, pass in the new image inverted, and then invert it again to make sure all the bistable elements were in the correct state.
Edit: I should also point out, that the book file itself stores the sheet as an entire image - the whole image being displayed is different, and thus would require the special handling noted above.