What is e-ink on e-readers like kindle? How does the technology compare to a regular screen?
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So it is made of little capsules containing positively and negatively charged ink of two different colours, usually white and black, sandwiched between transparent conductors. Unlike with an LCD, the ink stays where it is put, so a picture driven to it stays driven. The pixel can occupy states between white and black, and because the amount of ink in a capsule is well controlled and static, these are predictable, letting you drive greyscale images.
The backplane is a lot like an LCD – each pixel is a capacitor that’s charged to a positive or a negative voltage by one or more transistors.
To drive the e-ink you connect the counter-electrode on the top side, then drive a rapid series of black and white pixelated images that *add up* to the image you want to end up with, when *added to* the image you started with. Then you disconnect the counter-electrode and the image stays.
The way these images are calculated, the ‘waveform’, is complicated and proprietary. My first job in industrial science was doing another more senior scientist’s job while he invented a new way to do this. It’s surprisingly hard, and makes a huge difference!
Why don’t you just drive the one image you want the first time? Because the grey level is determined by the product of applied voltage and time applied, and it’s *hugely* easier to drive either black or white to your pixel than to drive, like, 50% of the black voltage.
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