Full-field optical coherence tomography using tunable-path-difference source for three-dimensional multi-layered imaging with enhanced signal-to-noise ratio

•Novel scheme of full-field optical coherence tomography (FF-OCT) is demonstrated using a tunable-path-difference source (TPDS).•TPDS-OCT employs dual-input Mach–Zehnder type to apply full-field interferometry.•Compared with comb-spacing-swept source OCT, TPDS-OCT is superior in terms of signal-to-noise ratio and total optical intensity into the camera.•Though improved performance, TPDS-OCT is possible to acquire images at the micron scale and multi-layered tomographic images with fine detail. We demonstrate a novel scheme for a full-field optical coherence tomography (FF-OCT) system using a tunable-path-difference source (TPDS). Recently, the comb-spacing-swept source (CSWS) method, including TPDS, has been successfully applied to improve the stability of three-dimensional (3D) time-domain (TD)-FF-OCT imaging by eliminating the mechanical scanning of the reference path, which has been the main source of undesirable noise in general TD-OCT. However, CSWS-OCT has the drawback of a degraded signal-to-noise ratio (SNR) from a duplicated interferometer structure. In this study, we improve the configuration of the TPDS so that it can be connected directly to the measurement interferometer, including the sample and reference paths of the OCT system. In our novel TPDS-OCT, a propagating optical path through only a single interferometer was critically helpful in enhancing the SNR while retaining the benefits of CSWS-OCT, and a free-space full-field interferometer of dual-input Mach–Zehnder type also has an even higher imaging performance owing to the simultaneous exposure of optical intensity into the camera and the short image acquisition time laterally. We theoretically and experimentally demonstrated the benefits of TPDS-OCT compared with CSWS-OCT in terms of SNR. We also demonstrated 3D multi-layered imaging, which CSWS-OCT cannot achieve owing to its limited SNR.