Full-field optical coherence tomography by achromatic phase shifter with a rotating half-wave plate

In optical coherence tomography (OCT), broad-bandwidth optical sources are required to achieve high axial resolution. Introducing a variable phase shift achromatically between the probe and reference beams is required for phase-shifting algorithms implemented to extract the coherence signal. We propose a full-field OCT using an achromatic phase shifter based on wave plates. The phase shifter that is almost independent of the wavelength over a range of 240 nm, can provide a phase shift of eight times the rotating angle of the half-wave plate. The system is based on a Michelson interferometer, illuminated by a white light source, and has several advantages compared with previous implementation of full-field OCT based an achromatic phase shifter. Numerical simulation on phase shift error and amplitude ratio between orthogonal polarization components at nominal phase shifts required for two typical phase-stepping algorithms is conducted. Approach for extracting OCT signal by the revised Carre algorithm is presented.