Quote:
Originally Posted by DuckieTigger
I would be interested to know which company and model uses rgb leds for their front lit eink devices. Unless you merely say it is possible, in theory.
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I thought I read about a model (1) mentioned on this site that didn't just dim the white LEDs and brighten orange ones, but had adjustable colour? But maybe the comment was about colour temperature.
Certainly the only reasons not to have real RGB LEDs are:
- Cost of the LEDs.
- Maybe controller cost is slightly more.
- Space and losses of the diffuser. Cheap ones without a diffuser change colour with view angle as it's three chips. Perhaps not a problem with clever combined lightpipe diffuser design.
- Extra wiring and controller complexity.
My background is in Electronics design and programming, even two CE handheld devices. So I know what real colours of LEDs there are (basic doping / materials) which all are monochromatic. White appearance LEDs are using a phosphor or a mix of phosphors on blue, violet or near UV, just like CFL, CCFL etc.
The thickness of the phosphor affects the colour and the brightness. Decent quality ones from the same batch look the same. The colour of any actual real LED does shift a little with temperature and current drive, not significant. It doesn't change with production has that's set by the physics, the bandgap voltage, which is why single chip IR LEDs have the lowest voltage and near UV LEDs the highest voltage. Green typically have a voltage nearly halfway between red and blue types, about 2.2V. High Intensity red are a different physics to older red and thus a higher voltage.