Patent ID: 8831054

Claim:
An optical system comprising: a laser device operable to output a divergent light beam is centered about an optical axis; an etalon device arranged to receive and filter a first uncollimated portion of the divergent light beam; a first monitor photodetector positioned to substantially exclude any fringe pattern of the light beam transmitted through the etalon device and to detect only a central portion of the first uncollimated portion of the divergent light beam, following filtering by the etalon device and to generate a wavelength-dependent detection signal, wherein the first monitor photodetector is tilted at an angle to the optical axis; and a second monitor photodetector operable to detect a second uncollimated portion of the divergent light beam, said second uncollimated portion travelling from the laser device to the second monitor photodetector without passing through the etalon device and to generate a wavelength-independent detection signal.