How-to identify LED, for tracking

Hi !
I’m working on a IR LED tracking system, with few IR LED (less than 10) and a modified webcam,
and my problem is to identify which LED is which.

Kalman filter is not robust enough because each IR LED is not always visible, and I want to be sure that LED ‘x’ stays LED ‘x’ all the time.

I found few solutions:

  • let the receiver ask each led separately to emit light, turn-by-turn
  • blink each led at different frequency
  • the last but my favorite one, is to make some light variation specific to each LED, and then recognize the pattern to identify the led. In this way, I think tracking will be ore efficient because LEDs never stop shining.

Do you know other methods ? which do you think is the best one ?
Considering the third solution, I don’t know what kind of algorithm to use, any clue please ?

Here are some articles I found on the Internet that helped me:
http://electronics.stackexchange.com/questions/38809/any-ideas-to-make-ir-leds-identifiable-during-position-tracking
http://www.mtbs3d.com/phpbb/viewtopic.php?f=138&t=15901

Thanks in advance for interesting.
Guillaume