Selective imaging with a frequency-modulated laser-diode interferometer

It is shown that selective extraction of an image from multiple interferograms can be performed by electronic processing of interference beat signals. The frequencies of beat signals generated by ramping the laser-diode (LD) current are proportional to the optical path differences between the reference and the object arms in a LD interferometer. A beat signal with a frequency corresponding to an object-assigned interferometric arm can be extracted by electronic tuning. An interference pattern detected by a dissector camera is sampled in synchronism with the beat signal, which permits two-dimensional selective imaging.