What exactly is the "correction amp" for??

[James Lehman]

Well, you are kind-of breaking new ground there. So, don't expect it to be easy. You've got it going on though!

James.

[Things]

OK, well, here is where I am at. If I get the ILDA test pattern looking good, the media test goes off slightly. So I tune the media test pattern till it is good, then switch back to ILDA. THen the ILDA pattern is outof whack again. I get the media test pattern good, and I get serious overshoot on the square. Any tips on how to stop it doing that??

Anyway, here are some pics:

Blanking working, "YOM". Anyone know wether the missing spots at the bottom are due to tuning or blanking? I am thinking blanking ...



"DISK" logo displaying fine, but the blank area on the d?



Perfect media test pattern (But also has the little blank spot)



the ILDA test pattern, with those same settings as above (Whats going on down in the left bottom corner tho?)



Square with those same settings (If I try remove the overshoot, it screws up other stuff )



All were at the same scan speed of about 17 - 22K

Any idea's?

What about the blanking? How do I fix that?

Cheers

[carmangary]

Blanking is generally a matter of software. Which software are you using? If you are using Spaghetti, adjust the blanking optimization. If I were tuning, I would probably tune to make the ILDA test pattern look correct instead of the other ones. Don't know what to say about the overshoot.

Anyway, glad you got it sorted out for the most part. Contact me in PM if you want some Spaghetti shows.

[Things]

hey Carmangary, I am using Spaghetti, yes. I will take another look at the blanking optimization.

THanks

[carmangary]

Yea, play with both enabling and disabling optimization as well as changing all the settings.

[buffo]

Things;

From the pictures you've posted, it looks to me like you're pushing your scanners too hard.

The phenomenon where you can only get the ILDA test pattern to look good at the expense of the LaserMedia test pattern showing diverging lines on the diagonal retraces is a classic sign that you're either tuning with the scan speed set too fast, or with the scan angle set too wide.

Try reducing your scan angle some more. You can sucessfully tune your scanners even if you're only scanning at 4 or 5 degrees. You don't need to be right at the edge of the performance window. (Tuning with a larger scan angle just makes it easier because the pattern is larger so you can see the details of the pattern. But if you get too large, you'll never get the tuning right. Better to use a smaller angle and a longer throw in your case.)

Bottom line, your 20K scanners may be giving you all they can. But if you have to make a compromise, get the lasermedia test pattern looking good first, and then get rid of the overshoots on the ILDA pattern. If, after doing these two things, your center circle looks a little distorted, then you're just going to have to live with that. But you're better off with a distorted circle than with the overshoots! (The scanners are ballistic when scanning the circle. It's rare for scanners to be ballistic when scanning normal ILDA artwork, however.)

I still think you can get it to look better though. Like I said, back off on the scan angle some more and then re-tune. Once you get your scanners dialed in, you'll find that for *most* patterns you can scan them wider. But the ILDA test pattern is a very demanding file, and you're not going to get more than 8 degrees out of it. (Have you measured your scan angle, by the way?)

Adam

[Things]

What is the formula to calculate the scan angle? Would the best way to test it, be to project a square as big as I can, and thats my max scan angle?

So your saying, mediatest > ILDA test pattern in this case? Right now, I have the media test pattern going OK, and the ILDA test pattern isnt too bad, but yeah I could get it better.

[buffo]

What is the formula to calculate the scan angle?

Have a look at this page on the Pangolin website. It tells you all you need to know about calculating scan angle.

Personally, I just use the look-up table at the bottom of the page. It's a lot easier than going through the calculations!

Would the best way to test it, be to project a square as big as I can, and thats my max scan angle?

That would be your max scan angle, yes. But max scan angle isn't really what you're looking for when you tune your amps.

You need to project the ILDA test pattern and then measure your scan angle. If you're above 8 degrees, you're too wide. In fact, given that you're running 20K scanners (and especially because you're having trouble getting them tuned), I'd recommend that you dial the size back until you're displaying the test pattern at around 5 degrees. *Then* see if you can tune the amps correctly.

So your saying, mediatest > ILDA test pattern in this case?

Yes. Absolutely.

Right now, I have the media test pattern going OK, and the ILDA test pattern isnt too bad, but yeah I could get it better.

You probably can... I've gotten remarkable results out of both the Scan Pro 20's and the Scan Eco 20's. But you need to be sure you're not over-driving the scanners first.

And if you have to choose between a perfect circle or a perfect lasermedia test pattern, go with the tuning that gives you the perfect lasermedia test pattern. Your scanned images will look better that way.

Adam

[Things]

Bah, even with the scan angle right down, I cant get both the square and the mediatest pattern perfect

I can get either the mediatest pattern good, but have overshoot on the square, or have the square perfect, and the mediatest starts getting distorted.

[carmangary]

I wouldn't worry too much about it. Just do the best you can. Maybe send them to Pangolin some day for them to tune them.