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Posted by Rita Berkowitz on 11/06/07 22:35
Bob Myers wrote:
>>>> And you think the MTBF of a CRT monitor is...what?
>>
>> It's irrelevant.
>
> It's completely relevant. You claimed that the "longevity"
> of LCD monitors was poorer than that of CRTs - therefore
> the MTBF of the CRT technology is most definitely part of
> that equation.
Not from an end-user's perspective when the LCD monitor dies quicker than
the stated MTBF. Most unsuspecting consumers are falsely lead to believe
that the whole unit has a chance of lasting the stated MTBF.
>> Stated MTBF of LCDs would have you believe the 50K-100K
>> hours.
>
> And the MTBF of the panel itself DOES reach and/or exceed this
> point. The weak point is the backlight; replaceable-backlight designs
> have been produced (although few customers are willing to pay the
> incremental cost), and it's a lot simpler to replace an LCD backlight
> tube than to replace the CRT itself in a monitor (which has a
> comparable lifetime to the BLU). LED backlighting, now coming to
> market, will change this situation for the better as well.
This sounds like one of them hairs that is to thin to split. The bottom
line is that pretty much any other part than a blown fuse in an LCD monitor
makes it uneconomical to repair. As for CRT itself, that is a very robust
component and has less chance of failure provided it wasn't dropped. Most
of the time it's the surrounding components that need fixing/replacing.
>>> The spectrum of even "full-spectrum" fluorescents is rather
>>> a significant compromise over reference sources such as
>>> tungsten lamps. Traditional fluorescent tubes have a giant
>>> green spike (or two). We used to use magenta-color plastic
>>> tubes over the fluorescent lamps to try to knock down the green
>>> to allow us to shoot film or video. Some professional video
>>> cameras (particularly those used by news videographers)
>>> have special settings to compensate for fluorescent illumination.
>>
>> You got it.
>
> But, as I noted, the concerns re fluorescents for illumination are
> utterly irrelevant re their performance as LCD backlights. What
> you care about in the backlight situation, from a performance
> standpoint, are the primary chromaticities and white point you
> can achieve, and the peak brightness. (Black level is more a
> function of the LCD itself.)
And no matter how hard we try with today's technology we still haven't got
it right.
>> No, they are using basic "gel" type filters between the backlight
>> and LCD.
>
> No, they're not. First, the color filters are NOT "between the
> backlight and the LCD." The color filter layer is produced on
> what is most often the "top" substrate (glass panel) that forms
> the LCD panel itself. The filters themselves are created via a
> photolithographic process and are basically a specially-made
> colored photoresist material.
Interesting. I've split apart many LCD panels and I've found the color
correction filters in between. This even holds true with the design of the
light engine in LCD projection TVs. It's more practical and efficient to
correct the light source before it hits the LCD than it is to try to correct
everything after it has passed through the LCD. The surface filters you are
referring to are there for antiglare.
>> No special technology here. Bust a few dead LCDs apart and you
>> learn more in 5-minutes than could be learned from most internet
>> sites.
>
> Actually visit a few LCD fabs, and you might learn even more.
It would be nice, but some of us only have the luxury of reverse
engineering.
Rita
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