Patent ID: 6980297

Claim:
A wavelength monitor comprising: a Michelson interferometer optical system comprising: an optical element for collimating an incident light beam from a light input section to generate a collimated light beam; a first beam splitter for splitting the collimated light beam from the optical element into two split beams; a first reflector and a second reflector each for reflecting the respective split beams from the first beam splitter; and an interference pattern generating means for inclining the wavefront of the reflected beam from at least one of the first reflector and the second reflector to generate an interference light beam having an interference pattern in the light intensity distribution in a plane of the interference light beam, wherein the wavefronts of the beams that are combined to generate the interference pattern have optical axes inclined with respect to one another; a second beam splitter for splitting the interference light beam received from the first beam splitter in a different direction from the incident direction of the interference light beam; a first photo-detector and a second photo-detector for receiving the respective beams of the interference light split by the second beam splitter; a first slit provided in front of the first photo-detector; a second slit provided in front of the second photo-detector; and a signal processor for counting intensity changes of the light beams based on signals from the first photo-detector and the second photo-detector wherein the first slit and the second slit are positioned to adjust a phase difference of signals from the first photo-detector and the second photo-detector.