A feedback control system for controlling a laser source. The feedback control system includes a laser source outputting laser energy and an optical sensor detecting the laser energy. The optical sensor outputs a measured signal in response to a measured amount of the laser energy. The system further includes an optical device receiving the laser energy and directing the laser energy to a predetermined location. The optical device reflects a first portion of the laser energy toward the optical sensor. A controller receives the measured signal from the optical sensor and calculates the amount of the first portion of the laser energy. The controller then adjusts the laser source to correct for the losses associated with the first portion of the laser energy reflecting from the optical device to obtain a predetermined amount of laser energy at the predetermined location.