Polaris pixel shift problem
We have 3 Polaris XTV-S CTP in our production. All 3 CTP have pixel shift problem, not too often but we just can not fix it.
Is this problem cause by NewsDrive ? Interface card ?
It's hard to see from your photo, however, since it occurs in the same place and with fine lines that are inline with the rotation of the plate, what you might be seeing is what's called orthogonality correction.
Originally Posted by adatsui
When the plate rotates and is imaged by the laser, the laser moves horizontally across the width of the plate. Effectively the laser winds the image onto the plate just like a sewing thread is wound onto a spool. This means that lines that are inline with the rotation of the drum are actually at a very slight angle. Orthogonality correction causes a single pixel jump backwards once the line reaches a threshold length. This allows the device to image straight edges inline with plate rotation.
Usually this one pixel correction is masked by the Gaussian (softness) nature of the laser, and on press by the ink spreading onto and/or into the substrate making the correction invisible.
Last edited by gordo; 07-26-2012 at 02:46 PM.
Your statement is correct... but not for this case.
Polaris is a flatbed (a-la capstan) CTP for newspaper needs. The spinner has a multifacet prizm and very tricky principle of compensations for non-ideal facets, based on oscillating cryctal with a mirror glued to it.
I was trained and had very good experience for the first Polaris generations (green laser) and never had a deal with violet extra-speed versions.
I do not think anybody at forum will be able to help, and the only one way is possible - call AGFA Tech support which becomes weaker and weaker nowadays
The last hope: may be Mr STSTech or 28-yr-AGFA-SE know more about XTV-S?
Last edited by VladCanada; 07-27-2012 at 09:05 AM.
It doesn't look like pixel shift, is is single pixel size, have you put a microscope on it ? Can't see any jitter, doesn't seem to be spinner related. Lots of questions to be answered. Does the line replicate the image content at the beginning of plate ? Did it ever come up inside the image area, is there any image beyond that line, have you tried exposing anything to the edge ? You say it affects all three ctps (?), how many newsdrives do you have there ? Have you ruled out the plate ?
Hey Vlad, thanks for that! At least owners of drum CtP devices now know something about their imaging system that they may not have known before.
Originally Posted by VladCanada
I must agree with Maxon. The problem you are having does not appear to be pixel shifting. One question I have, is do you have a plate processor for eack plate setter, or do you have a line set up?
1. Not the pixel shift but an extra-pixel generation caused by tricky optics.
2. Remedy - regular optics calibration performed by FSE or trained personell.
Thans all for so many useful information.
I agree with VladCanada "Tech support which becomes weaker and weaker nowadays". All local support are my friends since we've computer typesetting/computer to film. I think they all do there best. They came many times and still can't fix this tricky problem.
>> have you put a microscope on it ?
Yes, Will take a photo and post it here.
>>have you put a microscope on it ?
Will take a photo and post it here.
>>Does the line replicate the image content at the beginning of plate ?
I'm going to check it now.
>> Did it ever come up inside the image area,
>> is there any image beyond that line,
>> have you tried exposing anything to the edge ?
Yes. control wedge, filename and some other information about that plate.
>> You say it affects all three ctps (?), how many newsdrives do you have there ?
3 NewsDrive for 3 Polaris + online processor VXP 85
>> Have you ruled out the plate ?
we just chuck it in the bin!
We got to ask ourself what is common to all three systems. There is only three things common to all.
1. Power: If it is the power, I think it would be more ramdom on the plate, and not always in the same place.
2. Plates: very possible.
3. A Work station: bad memory area or disk
When you send a job to the plate setter and you get the shifting, does the Rip have the ability to go bad to that job and do a preview of it? Does the pixel shifting show in prewiew?
Another thing we need to ask ourself, is when did this problem start. Did we install anything around the time we started to have this problem.
Hope this is some help to you.
Thanks again. Let's ignore power issue. We've ask Afga , N94-V plate is good. The last thing to check is work station issue.
Our Rip can preview, we check the 1bit tif that send to NewsDrive 's hot folder . The 1 bit tiff always good.
We do install few other program on those workstations. May be our IT can help.
I've take some photo over microscope .
please view in full size.