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RE: filmscanners: LED Illumination for Film Scanners
On Fri, 22 Jun 2001, Julian Robinson wrote:
> Hey let's keep this clean and vaguely accurate even if it is OT...
Austin went just a bit over the edge with that 1000
hour MTBF figure.
Having designed many circuits and systems around HP
LED displays, optocouplers, fiberoptic transceivers,
etc., I was troubled by that number.
HP is now Agilent. Check out
and do a quick search using the search phrase
The first PDF I found cites a particular type
of LED, used in highway warning signs, with
a MTBF of 1.5 million hours (before catastrophic
failure). For simple aging, the paper cites
100,000 hours of operation before a 25%
reduction in light output.
A second paper gives mildly contradictory
data. This one (discussing LEDs for
instrument cluster lighting) gives 10 million
hours MTFB (catastrophic failure) and 50,000
hours of operation before a 75% reduction in
Either way, I think most of us won't have
to worry much about LEDs failing in our
Nikon scanners. The scanners will be long
obsolete before the LEDs die.
2000 hours is roughly a year's worth of work-
days (weekdays) at 8 hours per day.
I suppose if you figure in hard mechanical
shock (like in Austin's Land Rover) the
numbers might go down a bit. Time to fix
the potholes in your driveway, Austin,
or get new shock absorbers for that beast.