Needs Blanking

[steve-o]

Are you saying modulate the voltage to the driver board?

[The_Doctor]

The soft start circuit will use a slowly charged capacitor. If you find that capacitor, see what range that voltage changes through, and apply a similar deliberate change to whatever that voltage is input to. Take care not to exceed it under any circumstances, there's probably no protection. Take full care to avoid surges and static too, for same reason. Take full care also to avoid leaving a signal on that hacked input when the laser is switched off, unless you fully understand the circuit and can be sure it's safe. The easiest way is to remove the existing soft start voltage system and replace it with the modulator, and power the modulator from the laser's main PSU. Then all you have to do is wait till the laser has been switched on a minute or two before modulating it.

[steve-o]

Well, actually, I built the PS myself. The soft start is just (4) 10,000 uF caps and the current limit of the transformer itself. I'm not sure if the driver would like having 0-3.7 V pulsed to it..

[The_Doctor]

Nope, probably not...
If the driver has a series pass transistor or FET, you might be able to modulate that, but you'd have to make sure that couldn't make spikes of overcurrent that get through whatever protections exist.

Btw, with a low input voltage, you might be able to use a 5V 'memcap', for a soft start on a low-volt laser that isn't electrically modulated. Smaller. Panasonic 'Gold Caps' are a good one.

[steve-o]

Sounds good but I'm trying to leave the laser intact. It's basically a sealed-potted unit with the driver board unaccessable. I'm trying to modulate the beam itself.
Yeah , now that you mention it I could have used a 1F gold cap and saved some space..oh well.. its already built and installed. My hind-sight being 20/20 and all that...

[DZ]

An AOM would work just fine if you can stand the losses, which would exceed 10%. And they do require precise alignment to get the most out of them. I've used an old xerox AOM with a DPSS in a previous projector I built and it worked great! Take a look at this web site: http://74.71.13.129/optics_info/ligh...htshow_rgb.htm
Some pretty good info on using the AOM with some photos of it in use. You will want to build a good adjustable mount for it, building an interface is somewhat easy and it does great analog modulation. I sold my last two of these about a year ago for less than $50 each if I remember correctly. They show up on ebay from time to time.

David

[steve-o]

Thanks David, good info. I'm starting to get a clearer idea of all of the available options.
Thanks All.

Steve