Quote:
Originally Posted by drbroom
That makes sense, and presumably these IR beams sit in the bezel alongside/above the comfort light LEDs?
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Actually on some the IR LEDS and photo transistors are around the four sides on the main board. Shaped mouldings on the black (but transparent to infrared) bezel act as pipes or deflectors to catch or deliver the light vertically and put it on overlapping beams horizontally top/bottom and left/right. The relative reduction of multiple beams at right angles allows calculation of the touched position. It seems to only intermittently operate the transmitting LEDs (which are likely multiplexed) until a touch is detected and then the LEDs are continuously operated till touch ceases for a while. You'll see an initial lag on the drawing utility and then it tracks quite well. It's handy to see relationship between your finger and what the programming algorithm is deciding. Then maybe you can use text selection & keyboard more easily.
I increase margins and font size if I'm doing a lot of annotation. Speeds it up and makes it easier to select what you want.
Capacitive (low pressure, poor resolution) or resistive (more pressure, best resolution) both need two or more layers with transparent conductive traces. This significantly reduces light, twice as much for a reflective screen like eink compared to OLED or back lit LCD. All three technologies have been used since at least 1980s, sometimes on Plasma or CRT rather than LCD, OLED or eink.
Phones & PDAs used resistive before iPhone capacitive because then they were mostly having annotation or data input. The iPhone had bundled internet data so was mainly for content consumption. Apple bought in the Fingerworks GUI for that so was able to use the cheaper & lower accuracy capacitive screen. It was operator bundles that made iPhone a success, not any tech Apple developed.
The eink originally had no "front light", so quickly the oldest touch was updated (IR beams) and used to allow maximum screen brightness. The newer flush capacitive eink screens are very grey compared to earlier IR touch eink. I only read paper books in decent artificial light (to help glasses), so I deliberately bought a PW3 / PW2015 just after the PW4 / PW2018 came out. Both the PW3 and Kobo H2O original I have IMO have better (i.e. clearer and brighter) screens than the PW4 / PW2018 which a friend bought recently.
Other touch systems have been tried but don't work well.