Johnny Lee demonstrated various interesting ideas (detailed, e.g., in this video as well as this page) that take advantage of the Infrared camera from a Wii-Remote. The IR camera has 1024X768 resolution, and is designed to position-track the 4 brightest infrared-lit points in its view, at 100 Hz. Each of these 4 "points" could be a moving marker in the form of, e.g., an infrared LED -- the LED's emission is detected by the camera, which in turn outputs at 100 Hz, the position data of the IR "blob" observed. Which allows a fast and inexpensive DIY position-tracking system.
In the above setup, if each IR LED is not just powered on but also somehow made uniquely IDENTIFIABLE, it would give rise to many interesting possibilities. For example, this would allow continuously position-tracking each marker in space uniquely (i.e., with knowledge of which blob is which). In addition, having each IR LED marker being unique also means the setup could be extended to any number of points (say 50 markers) instead of just the 4 brightest points.
The question is: Assuming you start by connecting each IR LED marker to a microcontroller, what would be the most effective way to extend the above setup so that each IR LED marker is uniquely IDENTIFIED? I roughly describe one approach below -- is there some more versatile or simpler approach than it, or perhaps can improvements be made to it?
First, a method that is NOT promising: Since each infrared MarkerLED is connected to a microcontroller, you could have each MarkerLED blink in a unique pattern. But the IR camera has only 100 Hz refresh rate so if there were 50 LEDs, it would be difficult to fit in a unique pattern for each, without the camera's effective position tracking of the points becoming really slow.
Below is a rough idea I'm currently considering (tracks & identifies 50 IR LED markers):
Start by tagging on a simple IR-Detector next to the IR-Camera, both of whose ouputs are read/tracked in sync by a common microcontroller or computer.
Now, let's say there are 50 Markers. For each MarkerLED/Microcontroller circuit, you also add on a second IR LED, called the IdentifierLED, thus there is a pair of IR LEDs for each marker, both controlled by the microcontroller.
For a given marker, so that its position can be tracked, the MarkerLED is only turned ON for exactly a specific 20-millisecond-window out of each second (each marker has its own 20-msec window). During that same particular 20-msec-window, the corresponding IdentifierLED is pulsed in a specific manner by the microcontroller at a high frequency (e.g., 38 kHz), setting up a unique pattern/ID for that specific marker.
And the same for the remaining 49 Markers consecutively, each with its own different 20-millisecond-window and its own high-frequency identifying-pattern. That takes care of the markers' side of things.
Now, on the sensing side of things: For each consecutive 20-millisecond-window during a second, the IR-Camera detects the position of one specific marker (whose 20-millisecond-window it is) via the corresponding MarkerLed. At the same time, the IR-Detector identifies WHICH marker it is, from the detected pattern of the corresponding IdentifierLED.
And this position- and identification-tracking continues for all fifty of the 20-millisecond-windows within each second.
Thus, all 50 markers are tracked, with the tracking-side microcontroller able to update each marker's data once per second.