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RE: filmscanners: LED Illumination for Film Scanners



Austin,

> Yeah, me too, that's why I have that info.  The one I have in front of me
is
> VCC, and it's called the "ClipLite" and the "CubeLite".  Red, amber,
green,
> blue, yellow and clear.  For 3mm and 5mm LEDs.

>>
>> What company made those filters? - I'd like to look up the details (I
have
>> an extensive electronics data library going back about thirty years that
>> includes a very large amount of optoelectronics).
>>

I'm familiar with VCC, having spec'd their products many times over the
years. The early blue (and green) lenses were intended for use with small
incandescent bulbs with the same T1-3/4 form-factor that was adopted by LED
manufacturers, not for use with LEDs. Here's the type:

http://www.abclights.com/midflant134.html

> My guess is you are not an electrical engineer, or you would know that
LEDs
> do have a life span.  Because you haven't heard of them burning out,
doesn't
> mean they don't burn out.  In fact, their typical MTBF is rated for 1000
> hours.  Incandescent light bulbs are rated for 1000 hours.  Aside from
> having written and reviewed quite a few MTBF and MTTR studies on designs
> that included LEDS, I recently replaced 4 of the 6 LEDs in my
> radio/CD/Cassette in my 1989 Range Rover, so I DO know they do burn out.

Some of your recent statements of technical "fact" seem to be casting a bit
of a shadow on your own credentials as an engineer; once again here are
sites with valid data:

http://ftp.agilent.com/pub/semiconductor/led_lamps/abi018.pdf

http://www.uniroyalopto.com/aenmlife.html

http://www.wch.com/led.htm

http://www.safe.no/various/ledline.html

MTBF of an LED is wholly dependent upon power dissipation, current (in pulse
applications) and/or operating temperature. An MTBF figure of 100,000 hours
is more the norm for LEDs operated within their specified limits, with many
times that possible when the LED is run below rated power or pulse maximums.

Cliff Ober




 




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