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shutter stobing

jupiter8

jupiter8

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I'm trying to think of a cheap and effective way to hook up a shutter for cutting off the beam in my current laser projector project. How are people doing this? I need it able to be controlled electrically - will be computer controlled eventually.
 





Don't Laze Me Bro

Don't Laze Me Bro

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Well you could use a servo that would slide a thick pice of metal or something in front of the beam.
 
jupiter8

jupiter8

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Funny your should say that Dustin! I'm currently trying to get a servo controller up and running. Spent hours last night mucking around with the circuit, it's a bit meta-stable (read: retarded) at present. :whistle: I'll get it working tonight hopefully. I'm not sure if servos will be fast enough for this application though.... hmm... not sure.
 
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ElektroFreak

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For laser projector use you'll need a laser with blanking which means the driver circuit contains the ability to turn the laser on and off when electrical signals are applied to it, or (highly complex in comparison) an accousto-optic modulator (AOM) which is mounted outside the laser and alters the trajectory of the beam when an electrical signal is applied to it. An AOM is used in conjunction with an aperture and beam dump so that when signal is applied the beam travels through the aperture, but when no signal is applied the beam is shifted to a slightly different angle so that it misses the aperture and gets terminated into a dump. The beam traveling through the aperture goes on to the scanner mirrors and out of the projector. The system running at high speed gives the effect of a laser beam being turned on and off rapidly with the incoming electrical signals.
 
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jupiter8

jupiter8

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Thanks for that info ElektroFreak - exactlythe type of thing I'm after. My question is this - with laser blanking is that detrimental to the life of the laser, constantly pulsing it on and off like that? I'm thinking the second option (AOM) would be better. How do I make one from scratch? :)

Hmm... current bid $50 and rising. What do these things normally go for I wonder... There must be an easier (read: cheaper) way to do it.
 
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ElektroFreak

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Laser blanking has not been shown to reduce the lifetime of lasers, so I would recommend trying a laser with built in blanking first since it's very much simpler. You as a single person cannot build an AOM from scratch without a few advanced degrees and a some VERY pricey equipment.
 
HIMNL9

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Uhm, i can imagine some relatively cheap ways ..... a solenoid (cheap but not extremely fast, and noisy) ..... a motor (require some mechanical adapting work) ..... an old hard disk head assembly (more work required, but faster at the end) ..... a piezoelectric actuator (super fast, but not too much cheap, and can require at least a + and - 90V driving) .....
 
jupiter8

jupiter8

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HIMNL9 - now you're talking my language!
Solenoid - thought about it, out.. too noisy and slow.
Motor - I have a disc cut out of black plastic with holes in the rim, which I have spinning on a motor speed controlled by a simple pulse width modulation circuit. This works but there's no way to say, have it off and then give a short burst of flashes... then one flash, then another burst, then full on, for example.
Old hard disk head - hmmm. never played with these, not sure how to control it or how it would take modification. I could have a looksee.
piezoelectric actuator - I'll take your word for it!
 
HIMNL9

HIMNL9

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A pair of examples about piezoelectric actuator plates:

PI Datasheet | Details: PL112 · PL140 PICMA&reg Bender Actuators Multilayer Piezo Bender Actuators with High Travel and Low Operating Voltage ;     PI: Ultra Precision Motion Control

Piezoelectric ultrasonic sensors,ultrasonic sensors,china ultrasonic sensors,Piezo-ceramic ultrasonic sensors,Piezo-ceramic Buzzer,Piezoelectric ceramic Buzzer,china Piezo-ceramic Buzzer,WAC Data Piezo-ceramic Plate,Piezo-ceramic Plate,Lonati Plate,W

These ones "bend" the plate when you power them, and reversing the direction, they bend in the opposite sense ..... the WAC "knitting machines" types, have also plastic parts that can be used for build some mechanical assembly relatively easily ..... i can sketch and post a pair of ideas i had about that, if you want.
 
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ElektroFreak

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@theOP: You said you're planning on using this system for laser show use, right?

I've already explained the way it's done in the real world by professionals. If you're making a pattern or image, the on-off pulses will usually not be the same length, so electromechanical methods can be difficult. The only electromechanical device I know of that can handle the speed necessary for any kind of pattern generation or graphics is to use another scanning galvo and mirror to alter the beam path in a similar fashion to an AOM, but a galvo and it's driver can cost as much as a used AOM and since there are better options the electromechanical method is rarely used. HIMNL's piezo idea might work since I can't say I've heard of that one being researched for laser show use before.. Not trying to discourage innovation at all, but most of the methods mentioned here have been tried and rejected for true show use. Of course, it all depends what you want from your projector.
 
HIMNL9

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I also never seen the piezo actuators used in laser shows ..... i just made some research, about these "knitting machines actuators" like the WAC ones, that they say are the better ones, and found that they are used for "shift" needles in and out from wire path (ok, not directly, through something called "jacks", but the principle is this one), and that on rotating machines, they can be used on 400RPM cylinders with 20 or similar "arrays" of needles, so each turn the actuator must be able to reposition itself at least 20 times each turn (but probably more) ..... it means approximatively each 1/8000 of second, or at 8 KHz ..... is this too slow for a normal laser show assembly ?

Also, need to considerate how much can be influenced the speed, if they have to shift a plate for open and close the beam path ..... maybe i can get one of these units from a guy that i know, the next days .....
 
jupiter8

jupiter8

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Thanks everyone. Good info there. I'm leaning towards blanking, or the flexmod driver that KGB has suggested. I have a lot to learn...

I haven't actually built a driver yet... I have the electronics know-how. My soldering is pretty neat. I need a few new tools, a clamp of some kind for holding things steady, bits and pieces... looking forward to my first project. It's got to be more economical to buy laser diodes and build them into modules yourself, not to mention fun.
 
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jupiter8

jupiter8

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Another question on this subject... if one built an ordinary driver (regulator) circuit for a laser diode, and pulsed the power to that circuit through a power transistor, would that be in any way detrimental to the life of the diode? This seams an easy way to pulse a laser to me, and I could switch the transistor with an external circuit, like a simple 555 timer, astable circuit. Any comments?
 
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