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akajester
Joined: 09 Jul 2008
Posts: 934
Location: Wisconsin
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| Posted: Thu Feb 24, 2011 4:30 pm Post subject: Barco 808s edge focus issues. |
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I have a few things that I'm trying to clear up with my bg808s.
On the screen the left edge of the blue and right edge of the red "flare" out, causing issues with convergence and focus. Also, I can't even see the difference when I try astig adjustments in the menu. The middle, top and bottom look pretty good.
I've searched and found Guy Kuo's post about focus and mechanical aim. He mentions this phenomena and says the following;
"Consider the off center red and blue guns. If you aim the actual center of the phosphor of those tubes to project at the center of the screen, you’ll note that the phosphor usage distribution is unequal left/right due to the throw angle. Graph it out and you will see that the farther half of the screen gets illuminated with a smaller area of phosphor. Ever notice how the side of the screen opposite the side of the gun is less well focused? This is part of the reason.
Centering a field pattern relative to the phosphor and then using those lit up edges to guide lens aim will actually place the red and blue guns so they are mechanically slightly off true center. The left lens ends up pointed slightly left of center and the right lens ends up slightly right of center. At first blush, this seems wrong, but this can actually be advantageous because it makes the raster usage, resolution, and illumination more uniform across the screen. Less horizontal linearity compensation and lens flapping are needed."
According to the second paragraph, if I use a white field and use the edges to adjust mechanical aim rather than the standard center cross hair, they'll actually be slightly offset from center. Would this help my issue somewhat? Or is their a better way to fix this?
I THINK this is the phenomena I'm seeing. I have the optical focus as good as I can get it. I'm just trying to tune up the focus and astig more and this is where I'm at.
Thanks!
Dale
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akajester
Joined: 09 Jul 2008
Posts: 934
Location: Wisconsin
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| Posted: Fri Feb 25, 2011 5:49 pm Post subject: |
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Hey, does anyone still talk about projectors on this forum? 
Dale
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zGman
Joined: 22 May 2006
Posts: 599
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| Posted: Fri Feb 25, 2011 9:24 pm Post subject: |
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A few pics would help...
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dturco
Joined: 06 Feb 2009
Posts: 3778
Location: Eastern Shore Maryland
TV/Projector: Runco DLP VX-3000i Marquee 9500 parts doner
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| Posted: Fri Feb 25, 2011 10:51 pm Post subject: |
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| akajester wrote: | Hey, does anyone still talk about projectors on this forum?
Dale |
No, not really. 
Anywhoo, I have just been using each color on a full field to roughly align the guns. I don't know how barco works, but the Marquee one uses the color button the just Green, just red, just blue.
After the full field is layed over I go to full white to check the edges, then onto each color.
On each color I project the DVE test pattern with the alphabet, adjust it to the edges, raster and flapping on each color, then on to the next color.
Then fully adjusted white from there.
Way too simple, but that's the way that works without pulling out my hair.
I can make it harder but those steps are what gets a good picture every time.
_________________
Firefly rules. Can't stop the signal.
http://www.hulu.com/firefly
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ChrisWiggles
Opinionated SOB
Joined: 12 Mar 2006
Posts: 2529
Location: Seattle
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| Posted: Fri Feb 25, 2011 11:05 pm Post subject: Re: Barco 808s edge focus issues. |
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| akajester wrote: | I have a few things that I'm trying to clear up with my bg808s.
On the screen the left edge of the blue and right edge of the red "flare" out, causing issues with convergence and focus. Also, I can't even see the difference when I try astig adjustments in the menu. The middle, top and bottom look pretty good.
I've searched and found Guy Kuo's post about focus and mechanical aim. He mentions this phenomena and says the following;
"Consider the off center red and blue guns. If you aim the actual center of the phosphor of those tubes to project at the center of the screen, you’ll note that the phosphor usage distribution is unequal left/right due to the throw angle. Graph it out and you will see that the farther half of the screen gets illuminated with a smaller area of phosphor. Ever notice how the side of the screen opposite the side of the gun is less well focused? This is part of the reason.
Centering a field pattern relative to the phosphor and then using those lit up edges to guide lens aim will actually place the red and blue guns so they are mechanically slightly off true center. The left lens ends up pointed slightly left of center and the right lens ends up slightly right of center. At first blush, this seems wrong, but this can actually be advantageous because it makes the raster usage, resolution, and illumination more uniform across the screen. Less horizontal linearity compensation and lens flapping are needed."
According to the second paragraph, if I use a white field and use the edges to adjust mechanical aim rather than the standard center cross hair, they'll actually be slightly offset from center. Would this help my issue somewhat? Or is their a better way to fix this?
I THINK this is the phenomena I'm seeing. I have the optical focus as good as I can get it. I'm just trying to tune up the focus and astig more and this is where I'm at.
Thanks!
Dale |
What do you mean by "flare out"? Have you ascertained that this is an optical focus issue, or a beam setup issue? That is to say, are the dots flared or blurry when you look into the lens too, or just at the screen (turn down contrast a bunch so you don't blind yourself!).
As far as the gun aim that Guy is discussing there, no that wouldn't really affect this per se, his aim there is to get more even illumination across the screen for the R and B guns which are off-center. However, you do still need to get the lens flapping right side-to-side so optical focus is correct across the screen. I highly recommend using the phosphor-grain technique and a small piece of paper or 3x5 card to isolate optical focus from beam setup. Otherwise "blurry" at the screen you don't really know what's causing it.
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