The best way is to use a dedicated laser driver IC such as the iC-WKL from Global Laser.
This will take care of the careful regulation needed. It expects a laser diode with an inbuilt monitor diode for optical regulation.
Other less ideal ways to drive them are:
Laser diodes are usually very sensitive to variations in current/voltage (the lasing threshold is quite close to the maximum threshold so not a lot of room for error) so check your datasheet to see how much "play" you have.
This page has some good info on laser diodes.
1) Is it really as simple as grabbing a laser drive chip and a
three-terminal diode from digikey and hooking them up according to the
datasheet? Should the laser drive chip be able to handle all
protection mechanisms necessary, or is there typically another device
that's needed to handle some other form of protection?
The laser drive chips I'm familiar with are more about applying rapid modulation to the laser than providing DC power. Usually there's an additional power circuit required; and that power circuit is where the protection is normally implemented.
If you have a different type of drive chip in mind, please link the datasheet in your question.
2) Is there a central regulatory body that does any testing to
determine what class of laser you have, and whether your product
follows all the necessary regulations?
In the US, it's up to the laser manufacturer to self-certify their product. You may be able to find a consultant to assist you with that process if you don't have the expertise.
3) Are there any known issues using lasers with 1mm core plastic
optical fiber? I know that POF has very different transmission windows
vs. glass fiber, and I know that one of these optimal windows is
650nm.
Would the beam stay narrow inside the fiber, or would it begin
to disperse?
The fiber is a waveguide, and the laser power will remain confined within the fiber core. It will attenuate (lose power over distance). There is also a process called dispersion which means different components of the laser power taking different amounts of time to traverse the fiber---but if you're not switching the signal quickly that's not likely to affect you.
Edit: A major difference between POF and glass fiber is that even in its transmission window, POF has much higher attenuation than glass. Attenuation in glass fiber is measured in tenths of dB per km. Attenuation in POF (last time I worked with it, several years ago) is measured in tenths or whole dB per meter.
Would it still be coherent and collimated after going through, say, 15 meters > of POF?
The signal will still be coherent, but the dispersion effect I mentioned above may reduce the coherence length if you've gone through a very long fiber.
The output beam will diverge at a substantial angle (not strictly collimated) when it exits the fiber. The divergence is a diffraction effect and the angle is inversely related to the fiber core diameter --- meaning POF will have a lower divergence angle than smaller-core fibers. In multi-mode fiber like POF the output divergence angle also depends on details of the fiber construction. In general the output divergence angle will be similar to the input acceptance angle.
I am investigating the laser approach, because it seems like most LEDs aren't even capable of 500 uW.
It doesn't matter much what most LEDs can do --- if you can find one LED that meets your needs, that is enough. And I think you should be able to find an LED to produce 1 mW and couple into POF, if you look long enough. But a laser should be able to do it more efficiently (but maybe more expensively).
Edit: Be aware that using an LED does not reduce your safety concerns. 1 mW is still 1 mW and can still be dangerous. You will want the same safety precautions (you mentioned open-fiber control) whether you use a laser or LED. Regulations have not all kept up with the improved capabilities of LEDs in recent years, but that doesn't mean you shouldn't protect yourself and your users.
Best Answer
A quick Google search turns up a few guides to wiring up that board, or at least one that looks just like it. I suggest taking a look at one of those. But in general, assuming that is actually a polygonal scanner and not a galvo, it is going to take a DC voltage (probably 12, 15 or 24v), and a clock signal, which the driver will use to synchronize the motor rotation rate to. The clock signal is used to let you synchronize the beam scanning to another axis (for 2D scanning) or to a power modulator (if you are drawing something with the beam). There is probably a feedback signal as well that indicates the true phase of the mirror so you can figure out if it is locked to the clock and/or detect error conditions.
Since you don't know how many clock edges corresponds to one revolution, I would start by trying to get the motor spinning at a relatively low speed and then use a laser and a photodiode to measure how many times per second the beam scans. Since the mirror scans 720 degrees per revolution and looks to have 4 faces, from that you can calculate how many clock cycles there are per revolution.