Rebuilding blue polarizers - can it be done?

I should like to know the answer to this question also. But more fundamentally, how did you know that polarizers must be mounted in the correct rotation position, but not laterially? I just recently opened up a projector of mine to clean the panels, only to have to re-converge the panels. However, now my uniformity is way off, do you think that this could be my polarizer orientation? Thanks, keep us posted.

J

That's how polarizers work, they pass light differently depending upon the azimuth, (rotational orientation).

Consider a "Circular Polarizer" for a camera lens, you rotate it to give the desired effect.

One will notice that questions of this nature never get answered properly. Its almost as if this knowledge was being kept purposefully sacrosanct.

In other words this forum is full of people who have the ability do do things themselves without resorting to "This is a complicated operation and shouldn't be attempted by yadayadayada. I sometimes think that some information is not shared or tacitly discouraged from being shared, if not overtly than by association with servicemen etc. I have noted that parts are hard to come by and dealers won't sell "you must be an authorized blah blah" Please forgive me but I find this sort of protectionism a bit offensive. I admit to frequenting forums such as this because I often find that there are many people such as I who willingly share "inside" tips. I have found that my sharing leads not to a loss of business but to an increase in good will and therefore it is conducive..I think this inability to find polarizing filters for older projectors fall squarely in this realm.

I'll try to get time to try this next week. In theory it would work, though the color might not be quite as good due to having non-matching components. The rotation is critical as was stated above. Thats why it has to be adjusted.

Yes, you can use ANY good quality polarizer as long as it fits and you rotate it for optimal result. I did this a long time ago on an old Sony LCD projector with a bad blue polarizer.
As is typical, that part is never available. Would be too easy, right?

Well, this was a dumpster find anyway, so I took a plastic polarizer from a calculator and cut it to size and stuffed it in there. With the projector on, I rotated the polarizer until I got the best "black".
Taped the damn thing in place and used the projector for quite a while before I upgraded to a CRT.

It worked just fine. Using a glass polarizer would be better, but any GOOD polarizer will indeed work just fine. The polarizer doesn't make the color. The Dichroic mirrors in the light path do.

It's not rocket science at all. The manufacturers just like to make it difficult, so we just buy a new product.

I'm not sure what the difference is, but the different color polarizers are different. If you look at the three from a projector the color of them is slightly different. Shrug. I might also try swapping two of the colors to see what impact that has on the image.

Wow! You guys are great! This is the first straight answer I have gotten on this here! Thanks please share more if possible!

The dicronic lens and mirrors are part of the color separation process but there ARE different colored Polarizers. The one I'm guessing you are looking for is the yellow colored one that blocks the most UV light. Its generally the one that cooks followed by the LCD Panel itself. if you can get one that blocks the path of the light before the panel it doesn't really matter what shape it is .. You will need one made of glass since the plastic ones will cook. You can fool around with one from a cheap pair of UV blocking (sunblockers type) sunglasses that you pick up for cheap at a dollar type store. The ones that the projector makers use are generally fitted to the projectors light path. but if you can get one off another projector as long as you get it to block the light between the light path and the actual panel you should be good to go. If you can get one made out of Glass and can cut it down without cracking it. Make sure to put the coated part of the glass polarize facing the LCD panel.

Good Luck

Bohanna

BTW If you are just using the projector for data you can swap out a panel and polarozer from a matching projector that has the same style panels and polarizers in it but you will not get accurate colors like you would with factory panels. For example If you take two matching projectors that have burnt out blue panels which is common you can replace the Blue ones with green or red panels and polarizers and you will get a decent picture. its best to start with the green panel. I'm pretty sure since you have the yellow spot already you will also have replace the LCD panel.

ALSO NEVER take the panels off the optical block if you don't have to or you will have a alignment nightmare. Just take out the burnt out one and alighn it to the factory set panels

What I have are some truly workhorse NEC Vt units running 24-7 using a custom I have driver written in powers trip to give me 576 x 1024 picture is sharp and remarkable for blu rays other than an even slow skew toward yellow green over about a year. Of course this will be the blue pol. If I could fix this I would be overjoyed with these units

I won't argue that the polarizers in projectors are different and "tuned" for each color to achieve the optimum levels for each. The point was that any polarizer WILL work, for the sake of experimentation.
I got surprisingly good results from my own tinkering, but the color balance, in particular BLACK, was a bit off. Not a lot, though, and it made the projector perfectly watchable again if you don't go probing
with a color analyzer.

So if you have a doorstop, you really have nothing to loose by trying.

Amazing. I have just put all of this to test. So basically 1000s of projectors have been thown away completely wasted for no good reason at all. I wonder if we could find a source of bulk material and put this nasty little bit of secrecy to bed once and for all. I find this sort of thing offensive and wasteful.

And here are all the clues needed to find and perfect this from the perfectly acceptable but bakable blue block sunglass lens I tried via advice.......http://www.lhup.edu/~dsimanek/14/polaroid.htm

So really all the yellow tint for is optimization. Any of them would probably work well albeit with reduced efficiency require calibration of three colors? Ie...less lumens or black level but good color still?

So basically cut to size, this is the multi hundred dollar repair
http://shop.mobileweb.ebay.com/searchresults?cmd=SREF&catid=&kw=New+Polarized+Glare+Block+Sunglasses+UV400+New+Polarized+Glare+Block+Sunglasses+UV400
Disgusting.

Obviously plastic, as noted by others here will melt. Therefore a source for yellow tint polarized glass filters that can simply by anyone other than a gorrilla, be cut to size. Hundreds of projectors saved, a few less than forthcoming techs drive Kia's instead of Mercedes?

Here is another responce from NEC


Unfortunately, internal parts are not available to end-users. Only authorized

NEC servicers have access to these parts. Because of this we can not sell any

internal parts to you. Sorry for any inconvenience this may cause.


Thank you,

Keslie.

Total
BS

The sad thing is I have some freinds who are missionaries in Haiti and I can fix all of their machines in the schools but Kelsie at NEC wont sell us parts. Some times you don't want anything but to pay for a part.

There has got to be a source.

Been tied up that last couple of days. Fading fast!! The blue LCD screen and polariser are the weak link in the LCD technology. the Color wheel and the DLP chips are the weak links in DLP technology. choose your poison. Like said you can salvage projectors by using other panels even though the colors will be a bit off. But for schoolchildren in under developed countries it could be a perfect solution if they have a zero budget,

Bohanna

Well if that's the best we can do its the best. Really do appreciate your help.