Patent ID: 7432668

Claim:
A light source control apparatus comprising: a plurality of light sources, each light source emitting both a light signal at a discrete frequency and a reference signal at the discrete frequency, each light source having a different discrete frequency; a photodetector optically coupled to the plurality of light sources, the photodetector designed to receive the light signals from the plurality of light sources and to produce a received light signal based on the light signals from the plurality of light sources; and a plurality of lock-in systems coupled to the photodetector to receive the received light signal, each lock-in system further being coupled to and associated with one of the plurality of light sources to receive the reference signal from the associated one of the plurality of light sources; wherein each lock-in system produces an intensity value for the associated one of the plurality of light sources based on the received light signal and the reference signal from the associated one of the plurality of light sources.