Single-shot wavelength-independent phase-shifting method for full-field optical coherence tomography

One limitation of a piezoelectric translator-based phase-shifting method in full-field optical coherence tomography (FF-OCT) is that there exist interference residuals because a light source with broadband is used. In this work, an achromatic phase-shifting method was proposed in which a linear polarizer and a quarter-wave plate were employed to generate the circularly polarized light in the reference arm of a basic Linnik interferometer. The light field reflected from the reference arm is supposed with the unpolarized light backscattered from the sample when the path difference is within the coherence length of the light source. A first phase difference of π/2 can be generated on the propagation of superposed light beams through the polarized beam splitter. An additional phase difference of π/2 can be obtained by the proposed numerical method, thus producing the similar effects as the four-frame phase-shifting way. An en face tomographic image can be obtained with a single-shot in this new FF-OCT system. The axial and lateral resolutions of the system are around 1.4 μm and 0.8 μm, respectively. The system offers a dynamic range of ∼56  dB and an imaging rate of 30 fps. Tomographic images of Intel microchip, onion cells, and microcracks in the glass were displayed with clear substructures. This article aims at producing fringe-free OCT images in a single shot.