Thread: K4 Screensaver Hack
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Old 05-26-2012, 10:07 AM   #15
geekmaster
Всё гениальное просто.
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Arrow WHY eink burn-in cannot occur

Quote:
Originally Posted by LLM View Post
(Don't know if the Kindle screen actually burns in, but that would be a screen burner, rather than a screen saver.)
There is no "burn in". It may appear so after the kindle has been stored for some time, or stored in a cool location, but this is "fixed" by doing mulitple "full flash clears". On the K5(touch), you can do two or three "eips -f -c" commands. On older kindles it is just "eips -c".

WHY eink burn-in cannot occur:
Spoiler:
Every pixel of the eink screen is made of many tiny beads. These beads are filled with oil. Inside this oil are many tiny particles that hold a permanent electric charge. Half of the particles hold a positive charge, and the other half hold a negative charge (depending on whether they are black or white particles). The eink screen has a grid of fine wires that control the electric field. When an electric field is applied to a pair of row and column wires, the electric field is much stronger at (and to a lesser degree, near) the intersection of the wires, and it causes the black and white charged particles to move to the front and back surfaces of the beads.

Because some particles near the intersection also move, there is a complex interaction that can cause ghosting artifacts. The eink uses a complex alternating current waverform to "shake" the particles in a way that gets them where they need to be. There are different waveforms for different temperatures, and different waverforms for different production runs of the eink screens (adapted to the statistical median characteristics of that batch of eink screens). Screens that are a "statistical outlier" (far from the mean waveform prototype for that batch, but within quality control limits), may have less contrast and more ghosting artifacts than screens closer to the statistical mean for that batch.

When the oil in the beads is at a temperature lower than the waveform can tolerate, the oil viscosity is increased, slowing down the colored charged particle movements. This can leave some particles behind, stuck to the bead surfaces, causing ghosting. If you wait for the oil to warm up (ideally to 25C/78F), then do multiple full flash clears, it will electrically "rip" the stuck particles from the bead surface, giving a cleaner looking display.

If you display an image on the eink, then remove the display from the kindle (and from the rigid protective backing plate behind it), you will see a silvery negative image on the back of the eink display. That is because wherever the black or white particles were pulled to the front, the oppositely colored (and oppositely charged) particles were pulled to the back.

So, the SHORT answer to your question is "NO, the display cannot burn-in", but to those who do not understand the technology, it can APPEAR that burn-in does occur.

Last edited by geekmaster; 05-26-2012 at 10:17 AM.
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