I don`t know why you are so confident that the wiimote and the aimtrak use only 1 light to track their position, when they clearly track TWO, 2.
There even is a test program in the wii software that lets you check if all two light sources of the bar still work.
As for the aimtraks, if you take a look at their pcb-only bar, they also clearly have two independent light sources. There is no system out there that has only one light source.
I still don`t quite get what leaves you thinking that the GC3 has no ir camera in the gun.
I have EMS topguns and they clearly have ir cameras in them. they aren`t even covered or anything, just mounted in the nozzle.
Ill agree that an IR laser pointer should be the most cost effective AND accurate method at the same time, but expanding this system for two or more players is harder, since most people don`t like having multiple visible, colored dots on their screen most of the time.
I'm not confident on how any of them work internally beyond what I can see when I open them up and how they perform when used (for the ones I've tried). I'm not positioning myself as an expert. I don't read code like Howard or have any extra access to manufacturers designs. I can just see distinct hardware designs and therefore that they work differently but, for the most part, I don't understand the significance of the differences in hardware.
I currently own an Aimtrak, a Wii with Wii remotes, a Guncon 3 and a Sega type 2 gun set-up. What I know for sure (which ain't much) is that the Guncon 3 is noticeably more accurate than the Wii or Aimtrak and it uses two sensor cubes positioned at each screen edge with 3 LEDs in each, facing in different directions. The Wii and Aimtrak use one sensor bar with 2 or 4 LEDs all facing the same direction. Beyond that it's all just guesses.
The Sega Type 2 / Time Crisis 4 guns are the ones that have sensors instead of a traditional camera. It looks like some kind of photo diode with an IR filter. I'm going through the set up process now for my PC. I don't know how these work either. Just that it uses 10 or 12 led boards with two LEDs on each and that the order matters. I.e. If you mount sensor one in position nine you lose accuracy, Plus, it has 6 cables going in and out of each, which is more than is needed for power. My assumption is that there is a mechanism to sense which LED boards the gun is pointing at. Nothing else makes sense.
Someone here asked Andy at Ultimarc why there isn't a two sensor version of the Aimtrak to make it more accurate. The answer essentially said there was no mechanism for the gun to distinguish two sensor bars from each other so adding a second would make it less accurate. From that, I assume the Guncon 3 must be able to distinguish between the right and left sensor bars so it knows which one you are pointing at, or it would have the same issue.
As far as I know, nobody here has concrete info on how the various arcade IR guns work or, at least not enough to replicate the design for a diy version. If I'm wrong on this, it would make me happy and save me a fortune. I posted the info on the Raw Thrills guns as I thought it might help the guys here who are working on diy IR gun designs.
BTW, The Terminator Salvation method is not my info / guesswork. It's described in Raw Thrills manual. It's clearly a different design to the Sega, Namco, Aimtrak and Wii remote. It uses a simple camera module though so I thought maybe the design could be replicated.