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So there's no way to get fast analog current control without bleeding off extra power as heat? I guess standard methods to do it (buck circuit?) has inductances and properties which make it too slow to keep up?
So I got an email saying my order from Nautilus Integration has been cancelled. I guess DrLava doesn't have any more laserboy PCB's. I think my digikey order is in, though. I guess it's breadboard time.
The dimming circuits for many bucking topology circuits simply have a bypass transistor in parallel with the laser for PWM. It ends up using the same amount of power no matter what.
PWM is ultimately what you'd have to use to reduce the brightness without (much) heating. The problem is, of course, that you need a PWM base period that is far smaller than what you intend to have projected or you'll see those nasty dashes. At even a lowly 20kpps, you're looking at a very fast PWM.
Another thing to try would be using an acousto-optic modulator or something of that nature. It still may not be fast enough.