Layla 24, by Event/Echo Audio.
There might be others.
Pros:
8 outputs
Very easy DC capacitor removal/bypass.
Freely variable sample rates when driven by the WDM driver (won't work in W9X though, only the wave driver works there).
High linearity and accuracy.
Sample rates up to 96 KHz, meaning point rates faster than any current galvo.
Output voltage can be up to +/- 10V or more, and set by software, so no hardware level matching required.
VERY nice rack mount unit, free of induced noise that could degrade a scanned image.
Cons:
None that I can think of, bar cost, but lasers cost anyway, the real problem with these things is their rarity. They're damn cool, people usually keep them instead of selling them...
M-Audio and other firms make similar tools, but try to get schematics for I/O before shelling out for one cos most use a 2.5V ref voltage to centre the signal on zero, and while Layla 24 does this in a way that leaves the DC offset at zero BEFORE the output cap, allowing the easy modification, the Layla 20 (earlier model) does not, and many other units won't either.
So, given that these things are an ideal way to get hardware control to scan drivers and such, shouldn't there be more support for wave drivers in Windows and other OS's for sound cards? Pro audio firms have to be good at their drivers, so why not leave it to them, and make the laser scan software output as wave data? LaserBoy does this, but as far as I know, few if any others do. They all seem to need expensive dedicated hardware, with all the interfacing problems that can cause. I think taking advantage of audio multichannel capability, something most computers have in the OS, is a good basis for standardisation. It's just a matter of testing a few pro audio multichannel rack units for easy modification. A lot of new ones have rates to 192 KHz too, with specs way beyond most custom built DAC's, and at far less cost.