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

An achromatic phase shifter with a rotating half-wave plate (HWP) and a full-field optical coherence tomography (FF-OCT) system based on it are presented. The novel configuration of this phase shifter in the FF-OCT system can achromatically provide a phase shift of eight times the rotation angle of the HWP. The theoretical calculation of the phase shift and numerical analysis of the phase shift error, as well as the amplitude ratio, are conducted by means of Jones matrices. The actual phase shift has also been measured to confirm the validity of the '8 theta phase shift-HWP rotation angle theta' relation. The coherent image of a mirror has been obtained by using the Hariharan algorithm to verify the phase shifter's feasibility. Using traditional phase shifting algorithms, en-face images of a coin have been measured at different depths to illustrate the tomographic capability of this FF-OCT system. In comparison with other current systems, our design has several advantages, and high-resolution high-speed FF-OCT imaging can be envisioned. The phase shifter can be used for common path setups and is very suitable for implementing the phase shifting of a broad-spectrum light source.