Constrained polynomial fit-based k-domain interpolation in swept-source optical coherence tomography

Abstract

We propose a [Formula: see text]-domain spline interpolation method with constrained polynomial fit based on spectral phase in swept-source optical coherence tomography (SS-OCT). A Mach–Zehnder interferometer (MZI) unit is connected to the swept-source of the SS-OCT system to generate calibration signal in sync with the fetching of interference spectra. The spectral phase of the calibration signal is extracted by Hilbert transformation. The fitted phase–time relationship is obtained by polynomial fitting with the constraint of passing through the central spectral phase. The fitting curve is then adopted for [Formula: see text]-domain uniform interpolation based on evenly spaced phase. In comparison with conventional [Formula: see text]-domain spline interpolation, the proposed method leads to improved axial resolution and peak response of the axial point spread function (PSF) of the SS-OCT system. Enhanced performance resulting from the proposed method is further verified by OCT imaging of a home-constructed microspheres-agar sample and a fresh lemon. Besides SS-OCT, the proposed method is believed to be applicable to spectral domain OCT as well.

Effects of different interpolation methods on imaging quality of (SS-OCT) system

“…The NDFT methods can get good image, but this algorithm is relatively complex, so that it is more suitable for post-processing of OCT images. Another kind of methods are data resampling based on the phase of spectral signal, including time-domain interpolation method 14 and direct k-domain interpolation method 15,16 , which is widely used in data processing due to higher time efficiency [17][18][19] .…”