General Overview

[iamausername]

Please feel free to correct me where i'm wrong, I'm just starting out.
Please also don't get too technical as i'm trying to keep it simple.

From what I can piece together..

Galvanometers
A galvo works basically like a speaker driver, except it adjust the angle of a mirror instead of moving a speaker cone.
It has a maximum rating for how many times it can alternate per second at a given angle.
Galvos can be open or closed, closed galvos return a signal indicating the current position of the galvo.

Galvanometer Drivers
A galvo driver is essentially the amp for the galvo, it sends power to the galvo and for closed galvos, reads the current position.
The driver has a bunch of controls on it for fine adjustments to affect how the galvos move and therefore the image that is displayed.
The driver combined with the galvos have ratings which determine how many points per second they can move at particular angles.
Essentially, the higher the points per second at a particular angle, the smoother the laser animation is.
In order to do 2d images, two galvo drivers are used together, one for the X axis and one for the Y axis.

Laser Diodes
A laser diode actually produces the laser light, it has a rated power output as well as a light frequency.
Because humans perceive different colors at different intensities, different color lasers at the same power rating will appear brighter or darker.
A 532nm green laser will generally appear twice as bright as a 473nm blue laser and three times as bright as a 650nm red laser.

Laser Drivers
Laser drivers control the voltage sent to each laser, they can either be TTL or Analog.
TTL drivers can only control if the laser is on or off, Analog drivers can control the voltage and therefore brightness of the laser

Show Cards
A "show card" interprets digital signals from either its internal memory, or from an external source via ILDA.
It then converts these digital signals to analog voltages to pass to each galvo driver as well as either a TTL or analog signal to pass to each laser driver.
Show cards can have preset vector images or animations in its internal memory, these can be activated and adjusted via DMX from an external DMX controller.

Light Flow for RGB Laser Projectors
A typical laser projector is setup like the following:
The light from a green laser passes through dichroic glass which lets green light pass through, while reflecting red light
The light from a red laser reflects off the same glass, combining with the green light to produce yellow.
The combined yellow light then passes through a second dichroic glass, which lets green and red (yellow) light through and reflects blue.
The light from a blue laser then reflects off this second glass and combines with the yellow light to produce white.
This light then hits the first galvanometer, which angles the light towards the second galvanometer, which sends the light out the projector.
The combination of adjusting the voltage or turning on or off the different lasers produces the full range of available colors (7 for TTL, or the full range for analog)
The angles set from the galvanometers combine to produce a 2d image.

[colouredmirrorball]

Open or closed galvo signals refer to how the signal from the DAC is being sent, not on if there is a feedback system. An open galvo system is wired as XGY, while a closed loop system is wired as X+GX- Y+GY-. The same signal is sent over X+ and X-, and Y+ and Y-, and is compared in the galvo drivers. This is to minimalize noise. So in a open loop system you have three wires (X, Y and ground) going from the DAC/Show card/breakout board, while in a closed loop system you have six in total.
Feedback has nothing to do with this. Normally this is another connector on the driver.

I hope that's correct, I'm not an expert :P

[laserist]

Open or closed galvo signals refer to how the signal from the DAC is being sent, not on if there is a feedback system. An open galvo system is wired as XGY, while a closed loop system is wired as X+GX- Y+GY-. The same signal is sent over X+ and X-, and Y+ and Y-, and is compared in the galvo drivers. This is to minimalize noise. So in a open loop system you have three wires (X, Y and ground) going from the DAC/Show card/breakout board, while in a closed loop system you have six in total.
Feedback has nothing to do with this. Normally this is another connector on the driver.

I hope that's correct, I'm not an expert :P

It's not. Open loop and closed loop refer to the galvo. Torsion bar scanners could be run with or without feedback, but today's scanners have to run in a closed loop to function.

[taggalucci]

An open galvo system is wired as XGY, while a closed loop system is wired as X+GX- Y+GY-. The same signal is sent over X+ and X-, and Y+ and Y-, and is compared in the galvo drivers. This is to minimalize noise.

You are referring to the difference between Differential (3-wires: +,Ground,-) and Single-Ended (2-wires: Signal/+, Ground) galvo drivers. This relates to the method of analogue signal transmission accepted from the source by the receiver (amp/driver).

The Open/Closed concept refers to whether the galvos provide feedback to the amps for position detection to ensure positional accuracy, and the full terms are Open Or Closed Loop.

[colouredmirrorball]

Oh, I got my terminology wrong. Apologies!

[j4cbo]

Laser Diodes
A laser diode actually produces the laser light, it has a rated power output as well as a light frequency.
Because humans perceive different colors at different intensities, different color lasers at the same power rating will appear brighter or darker.
A 532nm green laser will generally appear twice as bright as a 473nm blue laser and three times as bright as a 650nm red laser.

Laser Drivers
Laser drivers control the voltage sent to each laser, they can either be TTL or Analog.
TTL drivers can only control if the laser is on or off, Analog drivers can control the voltage and therefore brightness of the laser

Not all lasers are laser diodes. (Some, like most greens these days, have diodes as a component, but there's a lot more going on under the hood.) It's not really accurate to say that the driver controls voltage; it controls power by some means. You said you're trying to avoid getting too technical, so I'd sum it up as this:

The lasers we use in laser shows usually have two parts: the laser head and the power supply. The laser head is where the delicate optical bits are. The power supply takes power input in some standard form (usually either 120v AC, or 5 or 12 or 24v DC) and a modulation signal (which can be analog, adjustable brightness, or TTL, fully-on or fully-off only), and converts it to be exactly what the laser head needs. The power supply may also be responsible for regulating the temperature of the laser head.

Show Cards
A "show card" interprets digital signals from either its internal memory, or from an external source via ILDA.
It then converts these digital signals to analog voltages to pass to each galvo driver as well as either a TTL or analog signal to pass to each laser driver.
Show cards can have preset vector images or animations in its internal memory, these can be activated and adjusted via DMX from an external DMX controller.

ILDA is an analog signal, not digital. A projector might only have an ILDA input; if so, it has to be fed from an external DAC, which connects or is built in to a computer somehow. Show cards are often found in Chinese projectors and they let the projector run without an external DAC. (The show card is basically a crappy built-in DAC). As you said, they have a few preset images and animations and are usually controlled by DMX; they sometimes also have a sound-reactive mode. Show cards usually also have an ILDA input so you can override them with an outside DAC.

Light Flow for RGB Laser Projectors
A typical laser projector is setup like the following:
The light from a green laser passes through dichroic glass which lets green light pass through, while reflecting red light
The light from a red laser reflects off the same glass, combining with the green light to produce yellow.
The combined yellow light then passes through a second dichroic glass, which lets green and red (yellow) light through and reflects blue.
The light from a blue laser then reflects off this second glass and combines with the yellow light to produce white.
This light then hits the first galvanometer, which angles the light towards the second galvanometer, which sends the light out the projector.
The combination of adjusting the voltage or turning on or off the different lasers produces the full range of available colors (7 for TTL, or the full range for analog)
The angles set from the galvanometers combine to produce a 2d image.

Pretty much, yep. That ordering of colors is one way it might work, but any order is possible with the right kind of dichroic filters.

[iamausername]

Thanks for all the input