Couple basic questions

[Bradfo69]

I should know these but...

1) What is meant by "fast axis", "slow axis" as it pertains to diodes?


2) I asked Tim Walsh this weekend and he confimed that in theory, any scanner can be tuned perfectly with enough patience. I forgot to ask him, what pattern do you use if you know the scanners are only rated for 25k? I only have/know of the ILDA 12k and 30k patterns.

[StarryEyed]

Hey,

what pattern do you use if you know the scanners are only rated for 25k? I only have/know of the ILDA 12k and 30k patterns.

I would decrease the scansize to a smaller angle that allows higher speed.So it should be possible to go 30k with the 25k galvos.
Or Increase the scansize to do it with the 12k Ilda-Testframe.

StarryEyed

[dsli_jon]

What is meant by "fast axis", "slow axis" as it pertains to diodes?

http://www.rp-photonics.com/broad_ar...er_diodes.html ...pretty 'technical', but complete-answer... better than something not-so... See if you can distill the answer, and explain it back...

2) I asked Tim Walsh this weekend and he confimed that in theory, any scanner can be tuned perfectly with enough patience.

Yeah, but whether or not said galvos were manufactured with decent-enough materials, tolerances, etc to remain stable, etc is more the-issue... ie: just about anybody can balance a sword on the tip of their nose... for a time...

I forgot to ask him, what pattern do you use if you know the scanners are only rated for 25k? I only have/know of the ILDA 12k and 30k patterns.

Shouldn't see all-that much 'difference' with 25K vs 30K's, mostly, you'll end-up seeing a difference in how 'circular' the center-circle is... and you can still use the ILDA-test pattern, it will simply be a matter of how much 'flicker' and / or 'rounding' you experience if you're running the galvos beyond their designed-speed..

..But, it seems the best way to really 'eval' galvos is to use a variety of test-patterns, ILDA, Aura, LaserMedia, Grid, Square-Circle-Triangle, and I always like to put-in at least one frame, with a 'squarish outline-font' ...actually - using the word "TEXT" is a good 'word' to use, since you have verticals, horizontals, and both-axes of 'angles'... I also found (ironically.. "AVA" to be useful...

I'm sure Sirs DZ, Buffo, P'fessor Steve and other-such tuning-Pros, here, can add their tips / tricks / tester-goodies, too....

ttyl..
j

[White-Light]

Shouldn't see all-that much 'difference' with 25K vs 30K's, mostly, you'll end-up seeing a difference in how 'circular' the center-circle is... and you can still use the ILDA-test pattern, it will simply be a matter of how much 'flicker' and / or 'rounding' you experience if you're running the galvos beyond their designed-speed..

Don't know what Galvo's you have there (OP), I have the 25K LM's (Kvant) and the test pattern looks pretty much perfect. I can't spot any errors at the angle I'm testing them at except as Jon suggests, on the patterns containing a lot of small circles, the circles don't quite meet perfectly. (The large circle in the main test pattern looks ok funnily enough). The slightest of tails is visible on the small ones though.

In use with graphics, at 30K, the same can be seen, the circles don't quite meet but its very slight. A reduction in scan speed to 25K makes them perfect.

So you should be fine using the 30K pattern provided you realise that the circles, may have slight tails even when perfectly tuned.

[steve-o]

1) What is meant by "fast axis", "slow axis" as it pertains to diodes?

If you take a raw laser diode with no corrective optics attached and shine it at a wall a few feet away, you'll see a rectangular pattern of light, much longer than it is wide. This longer area of the rectangle is the fast axis.

[Bradfo69]

Thanks! While Jon's link was informative, made sense, and if you want me to explain it back, I now can (rather scarey that this stuff is sinking in) but, steve-o put it in the simple terms I was wondering about. I knew it had to do something with the stripe but didn't know if the length or width of the rectangle was referred to as the fast or slow.

The attempt at tweaking and tuning will commence shortly. Currently, the circle while still the shape of a circle is extending outside the box on one PJ so, I want to begin by double checking everything and tweaking that one. It's a 40k but, I've also got a couple 25k's I want to check. Too much knowledge is a dangerous thing and maybe I should leave well enough alone but, after studying it at TEXLEM, I'm itching to give it a go and get the best out of my gear that I can.

[mixedgas]

Use the 30K pattern, set the angle to whatever angle your galvos are rated at, and set the SCAN SPEED in software to 25K PPS or less.

Beware of the 30K pattern with the BIG extra box around it.

Steve

[Bradfo69]

Beware of the 30K pattern with the BIG extra box around it.

That IS in fact, the one I have. (LD2000) Aside from what it might accidentally reflect off of, what else should I beware of with that pattern? Is there a source for the one without the big extra box? I know I've seen reference to it.

Thanks!

[mixedgas]

Basic Answers:

http://www.laserfx.com/Backstage.Las...Scanning1.html

http://www.laserfx.com/Backstage.Las...Scanning3.html

http://lasershowparts.com/files/Arti...20Tutorial.pdf

Skywise is kind enough to host this for me, its a combination of two unique older manuals that contain most of the basics and then some:

http://www.skywise711.com/lasers/scanner/scanner.html

It is geared for those with more of a analog electronics background.

If you read it, dont touch the 'scale factor' on Asian amps unless they are badly misadjusted.

If you can, borrow a oscilloscope and look at the feedback signal coming out of the amplifiers.
Its there for scan fail and factory adjustment. On my "Chivos" it is a pair of unterminated white wires just hanging off a connector.



Steve

[Bradfo69]

Thank you Steve. The pages from laserfx I have seen before but forgot about where they were located. Adams I had read again this afternoon. The sky wise I hadn't seen and looks to be good reading I'll try and get to tomorrow.

~Brad