Quote:
Originally Posted by JSWolf
I've not read of color patches with Readers that us IR touch. It's only capacitive touch where you get the color patches. I don't think it's the LEDs. I think it's the capacitive layer causing it.
|
It is either the light guide, or the bonding between layers. Refraction is a fun thing. The light guide is intentionally causing refraction to guide the light, and issues with that can certainly create things like shimmer. But you also get refraction at any point where two materials meet. Water and air, two different plastic layers, glass and whatever, etc. Things like adhesives when applied properly can alter this refraction, but if not applied correctly, or not fully cured will mean that the refraction effects from the adhesive aren’t even across the screen. That’s likely where the splotchy coloring comes from. In some cases it will get better as it cures, in others it won’t because it is because the layers weren’t evenly squashed together during manufacturing.
If Amazon could mount the capacitive layer behind the eInk display, that would help. But more because it would mean only one layer of adhesive between the light guide and the eInk screen, instead of the two they have on the Paperwhite.
As for the LED count, there’s two issues at play:
1) Underdriving the LEDs will get you more Lumens per watt. It is weird, but it works, to a point. More LEDs allows you to be more power efficient for the same amount of light. In exchange for a higher BOM.
2) LEDs are pretty directional. 120 degrees for bare LEDs. You need optics to reach 180 degrees, and those optics would have to be built into the light guide. But using more LEDs means you don’t have to work quite as hard to avoid cones, since you don’t need to push it to 180 degrees which is not easy to do with a light guide (probably not as relevant here, because long vs short edge makes it different too).
But there are other ways to address #2, such as moving the lights further from the exposed part of the screen, and unfortunately, I haven’t really looked at the tear downs of the Kobo and Amazon lighting to see why one works better than the other.