Marco,
I will try to answer your questions.
> May be I've asked to much, but I'm intrigued how the LED can couple in
> the light sufficiently to be distributed equally all over the whole
> display.
It is channeled using fiber optics.
> And then the LED power supply should provide about 20mA to
> guarantee enough "pumping" UV light to the UV-to-visible
> light converter inside the LED. But these current of 20mA can be chopped
by
> e.g. a duty cycle of 5% (1:20), resulting in only 1mA average current
consumption.
> Then could we have the backlight always on, if the MP is on.
You have fallen into a mathematical trap!
On the surface, it would appear that there is a great saving by having a
small duty cycle.
Indeed, if you turn the lamp on for only 5% of the time, the average current
is 1mA.
But wait! You can't get something for nothing. For the same average light
output, you
would need to increase the current through the LED 20 times!!
This is the same principle that a TV remote works. The LED is pulsed at a
low duty cycle.
The reason for this is not battery life, but Tx range.
The area under the curve has to be the same in all cases for the same light
output.
Sorry.
>
> May be Apple didn't do that because white LED's where not available at
> that time.
I would guess that is true.
> --
>
> Regards / Viele Gruesse
>
> Marco Mailand
>
Regards,
David Humphreys
PCB Designer
Honeywell Inc.
mailto:david.humphreys@honeywell.com
******************************************
This NewtonTalk Message brought to you by:
EVOTE.COM, the ESPN of Politics on the
Internet. Visit EVOTE.COM for all the latest
news on Campaign 2000!
Visit http://www.evote.com today!
******************************************
Need Subscribe/Unsubscribe Info?
visit http://www.planetnewton.com
******************************************
This archive was generated by hypermail 2b29 : Wed May 03 2000 - 09:41:22 EDT