Galvo for Blanking

[planters]

When selecting a galvo for blanking are there certain features to look for?

Is it best if the blanking galvo has the same rated speed as the scanning galvos in the same system?

Is there a guide to sizing and spacing the retro reflectors (if used)?

How do you tune the blanking galvo.

[danielbriggs]

I remember Steve (mixedgas) writing some time on here about tuning to square wave.

Myself and Rob designed and built a similar blanking system for a LSCP a while back.
I would use whatever spare galvo you have lying around; I can't think of a reason why it would be necessary to match them with the scanning pair.
What are you trying to blank?

[planters]

I have an LS pumped dye head converted to 575nm and the existing spacing would allow the blanking mirror to sit within the dye cavity. This would allow me to forgo the retro reflectors and minimize the tails as well as the need for a beam dump and the heat. Alternatively, I could just conventionally blank the output anywhere from the sub mm output beam up to the collimated (4-5 mm) beam. This two color projector will modulate the blue electronically and the same Beyond FB-3 has to run both. I ask about the galvo speed because I'm not sure what the week link is for performance and want it to not be limited by the blanker, but don't want to overspend either.

[mixedgas]

"How do you solve a problem called Maria... How do you keep a wave upon the sand... And how do you make her stay... And listen to all you say."

OK, enough fun from the Sound Of Music...

For a dye laser.... um.. no problem.

0. Get a oscope and a nice signal generator.

1, Does this flag take any heat? If it does not have to block pump beam, its a intracavity shutter and it stays cool in most cases. Then any ole galvo will do. If the flag is going to get hot, that is a issue. Even a tinsy 150 mW 60 X heats a tiny black anodized flag HOT. So in some cases the flag needs to be reflective or transflective. For a hot shaft, we go with a few General Scanning products that have big metal bearings instead of ceramics. For a cold shaft, eh... whatever.

In your case it sounds like you just need to spoil lasing. Thats not so hard.

2. Its not a fast scanner, often. Your at 1/5 or 1/10 the point rate if your doing beams. For graphics, you may need faster. If you want fast, you put it at a focal point using relay lenses or a gaussian point intracavity

Retroreflector blanking is not in the scope of this post.

Usually I just mount a 1 mm wide by 4 mm long flag on a normal scanner mirror mount.

You tune by looking at the scanner feedback signal on a scope. Square waves and triangle waves help. A 50 Hz sqaure wave at 50% duty cycle and a low to medium deflection lets you see the ringing at the leading edge of the wave on the scope. Make a sharp edge and get the ringing to less then 3-4 decaying cycles. Its a log decay, and its right after the shock excitation at the leading edge.

Often if we were using mirror based scanner blanking, we would substitute the scanner into the x-y mount and align using a horizontal linear ramp frame to make a fake scope, and then the vertical would be a set of square waves or triangle waves of decreasing amplitude.
Watch on screen and tune. (Matt's method. Matt reads here, but does not post here. Hi Matt. Miss our discussions, Did you save the entirely OAK wooden projector that we did that on?) This does not help much if its a anodized flag.

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

Skywise hosts that for me, bless em...
Part of it is from something Cambridge used to hand out on scope based initial tuning at ILDA conferences. The other half is for a Laser Media 12K product that is LONG dead. But I have one. I do not have the BBST frame set. If you look, its a modified Rose of Bernuli from the math books(Spelling?)

Chapter 10, tuning strats...

http://www.camtech.com/archive/742-7...I_Manual_A.pdf

Minisax is not a modern P-I-I no D Asian amp, its a true P.I.D amp.
So no HF damping, and just LF damping, but the concepts are similar.


If this is for regular graphics, and not some high power monster.

Scanner blanking can work VERY well with small flags and two equal focal length lenses.
just for normal laser use. From the six simple lens cases: Case III, Source at 2F, image at 2F, so two lenses in series with a intersecting focal point, place the scanner flag at the focal point between the lenses. The first lens focuses it to a point, the second lens recollimates it. Some even used back to back microscope objectives. (Michael's technique)

Where do I send the consulting bill?

Steve

[planters]

Holy S**t

Be careful what you ask for. I'm going to have to re read this many times. But, thanks.

Near the mid point of the cavity and the dye cell the beam waist is aprox 150 um so a flag sans lens might work.

I have a nice scope, but I'm going to have to look for a signal generator. I should have one anyway.

Send the bill to my mountain top lair. Be aware, I only pay in Scotch.

[mixedgas]

quote:
Send the bill to my mountain top lair. Be aware, I only pay in Scotch.[/QUOTE]

Do you own a all white cat? Have a shark pool in the lair?

Have a Lemniscate of Bernoulli (google it) on all your Evil Henchmen's hats yet?

Send me that email with your email adress again, I have something else for you, file wise

I once had a software vendor demand payment in a case of a every expensive candy bar, after doing a mod to his freeware. Think Wonka grade cocao.
Purchasing said, no, we will only pay him by check. He delivered the software by email before I could say no deal.
The lawyers of the fine state institution I worked for, said send the chocolate immediately, or risk serious treble damages under some wierd copyright law.
He got his case of candybars. I got a repremand for a un-authorized verbal software contract under state law. It was worth it when the custom code worked.

A 555 timer driving a HC or AC cmos filp flop swings close to rail to rail at 5V with a sharp edge. Thats good for a 50% duty cycle start. The rest you can create in Pangolin or LSX.


I'm not supposed to have alcohol according to my Doc, but I'll settle for a Mike's Hard Lemonade at Selem. Oh wait, the Artists Inn at SELEM didnt have hard lemonade. Vodka neat, please. One and only one ping please, Vasily...

Steve

[planters]

At the end of the world Ayn Rand or Bible you choose...there will be a few left to guide us. In the mean time....isn't this fun

[mixedgas]

Bible for me! The lim curve thing gets the galvo back into the test at the right velocity and checks for symmetry where the braking points live and overlap on the ancient blanking test pattern.

Steve

[dnar]

I was looking for the English speaking laser forum.

Say you know, I knew I should a made a left turn at Albecorkey...