Patent ID: 7489405

Claim:
An optical coherence tomography system comprising: an optical source to emit an optical beam; a sample space; a photodetector; an interferometer set-up including a reference reflector, and a beam splitter-combination arrangement to split, the optical beam into a reference beam to the reference reflector and a sample beam to the sample space, and to combine a reflected beam from the reference reflector with a returning beam from the sample space to form a combined beam, and provide the combined beam to a first port of the photodetector, and a further beam splitter which receives part of a radiation from the beam splitter-combination arrangement and couples out a reference signal to a second port of the photodetector, wherein the photodetector scales and subtracts the combined signal and the reference signal to form an output photodetector signal having a reduced noise for output from the photodetector; wherein the optical source has an emission wavelength in the range of 1.6 μm to 2.0 μm, associated with a transition between an upper energy level and a lower energy level, and the optical source comprises an excitation system which generates stimulated emission from a pump level to the upper energy level.