First Scanner (RGY)

[Mille]

Ok just a question: how can i set the scanning angle?
I need to make adjustment on scanner boards, or i do it simply reducing the image width in software's geometric correction?

[buffo]

Normally you do it in software. You would need to reduce the width and the height by the same amount, of course.

If you *can't* adjust it using your software, then you can try reducing the input gain on the scanner amps. (Note: not the servo gain!)

What software do you use?

Adam

[Mille]

Normally you do it in software. You would need to reduce the width and the height by the same amount, of course.

If you *can't* adjust it using your software, then you can try reducing the input gain on the scanner amps. (Note: not the servo gain!)

What software do you use?

Adam

Ok... when i got home i'll try to get some picture with a 8 degrees angle.
Im using the pangolin FB3 software: so the LAstudio ones and livequick.

[Mille]

Ok i did some shot of the ILDA test pattern and the Lasermedia pattern at a scan angle of 8 degrees (20k scanning).
Ehm... i forgot to do a test at 5 degrees...
I'll do it tomorrow.

[stanwax]

Those exact same scanners can do a nice ilda TP if tweaked
See image Looks a bit ropey but thats cos the screen is a towel! @ 20k & I think about 15 degrees (dont quote me on this)

Rob

[buffo]

Hi Millie;

OK - now we're getting somewhere! Those pictures are enough. As you can see, at 8 degrees, the circle is outside the square. But when you get beyond 8 degrees, at some point you reach the limits of the scanners. At that point, the circle stops getting larger (but the rest of the pattern continues to increase in size). So the reason your earlier pictures looked messed up is because you were trying to scan the ILDA test pattern at too-wide of an angle.

Ok - you need to tune, but you're close. You've got a little bit too much gain. (which is why the circle is outside the square) My suggestion would be to decrease the scan angle *just* a tad more from the 8 degree position. (Want to be sure you're not over-driving the scanners.) You can tune at 3 degrees if you want, but trying to tune at 12 degrees will give you problems.

Also, having a longer throw (distance from the scanners to the wall) will help you tune better, since you'll see subtle changes in the test pattern more easily. (Especially the over and undershoot on the corners of the inner square.)

On to the tuning: First you need to dial back on the servo gain on both amps just a bit. The circle should get a little smaller, and the overshoot you see on the center square should get smaller.

Now dial back on the HF damping. You want to bring it down until you see some undershoot, and then add just enough to bring it back to the dot on the corner.

Now dial back on the LF damping. Again, take it down until you have overshoot, then add just enough to bring it back to the dot on the corner.

Keep doing these three steps on *both* amps until you get the circle just touching the center square. Then check the LaserMedia test pattern and make sure that the two diagonal re-trace lines are right on top of one another.

Note: You may want to reduce the tuning a few extra steps to get the circle *smaller* than the center square, and then tune *UP* from that point. Some people find it easier to tune when they are increasing the gain first, then the LF damping, and finally the HF damping, in that order. If you find it's easier to remember what you're doing when you're going "up" like that, then by all means try it.

When you're done, you should end up with something that looks like this:



This pictures is from the set of ScanPro 20's that I reviewed earlier in the year. The wavy side of the outer square is caused by the projection screen (a black sheet) being blown around by the ceiling fan, and is not an artifact of the scanners.

One final observation - I'm very surprised that Rob was able to get 15 degrees out of his ScanPro20's. That seems really wide... I've gotten 11 degrees out of them, but that seemed to be the absolute limit - at least when scanning the ILDA test pattern. EDIT: Just noticed that Rob said "don't quote me on this", so maybe he was scanning at around 11 degrees after all.

Bottom line - if you get 8 degrees, you're fine. Anything you get beyond that is gravy.

Adam

[Mille]

Ok
first of all, thanks Adam for the kind help

I will tune galvos later when i have enough time to spend on it
I have another question about the scanning angle.
Galvo tuning is done at 8 degress then, but can i scan at a wider angle?
If i scan at around 20 degrees (if i don't do any geometric correction) the image will be just more flickering, or can i damage the galvos too?

What's the maximum angle and scanning rate i can achieve with my scanners?

[buffo]

Hi Millie;

The ILDA test pattern is one of the most demanding images you can scan. It's intentionally designed to push the scanners. Would you believe that the center circle is actually supposed to be a 12-sided polygon that lies completely outside the square? The scanners have no hope of ever reaching those points - they're just too far apart - but it makes it easy to tune them while they are under maximum acceleration.

You can normally scan images at around 20 to 30 degrees with no problems. If you start to see distortion in the image, then you need to back off your scan angle a bit. But when you TUNE your scanners, you need to be sure that you aren't scanning too wide, or you'll never get the tuning right.

As a general rule, flicker is a function of scan speed, not scan angle. So you probably won't notice any more flicker if you scan wider.

You *can* damage your scanners if you push them too hard. But it's not something that will happen in a matter of seconds. You'll know that you're pushing them right away, because the image will look terrible. Corners will be rounded off, circles will start to look skewed, and the whole image will just look bad. If you keep running the scanners like that, they will get hot, and in an extreme case they could fail. But you'll have time to lower your scan angle long before that happens.

Things to watch out for: If you hear your scanners making a screeching sound, that's bad. If you see the image waver and start to develop funny curves in otherwise straight lines, that's bad. If you start to notice funny curved tails on the ends of lines, that's bad. In all three cases, turn your scan angle down a bit and the problems should go away.

As for an absolute scan angle limit, that's hard to predict, because different files can be scanned at different angles. As a general rule, the more complex the graphic, the lower your scan angle should be. I've pushed those ScanPro 20's to beyond 40 degrees on simple images.

Also, if you plan to scan mostly fans, tunnels, and beam effects, then you can tune them for a lower speed (like 10K or 12K) and you'll be able to scan even wider. But of course, lower speed means things will flicker more. (Flicker isn't a problem with simple beams, but it becomes an issue with graphics.)

Bottom line - start at 20 degrees and then just watch the image and adjust your scan angle accordingly.

Adam

[Dr Laser]

Sorry for my language. Buffo actually pointed this issue and I agree.
Let me explain why I'm strongly against those type of laser mounts. If projector will stay in one place and will never be moved then thy are fine. But if you're planing to transport it you will run into realigning-everytime issue. The best way is to measure the height and get a blocks of aluminum little bit smaller then the measure and then get a very small sheets of aluminium to lift it to proper hight. This way it'll be solid and do better with cooling.

Cool... all that info would have been usefull some week ago when i asked some tips in building the scanner

Btw i took some pictures of the ilda test pattern.





How do you think is the galvos tuning?
I'm oriented to do beam shows more than graphics...
Theres some geometrical correction (the sides are little bent)

[Mille]

Ok i little update with some pics of the scanner in action
If i find a vodeocamera from my friend i'll post a video too