Generic real-time uniform K-space sampling method for high-speed swept-Source optical coherence tomography

Abstract

We developed a universal, real-time uniform K-space sampling (Rt-UKSS) method for high-speed swept-source optical coherence tomography (SS-OCT). An external clock uniform in K-space was generated. The clock was synchronized with the zero-crossing time of an interferometric calibration signal and used as triggers for a high-speed data acquisition system in a point-by-point fashion, hence enabling uniform data sampling in K-space. Different from the numerical calibration algorithm commonly used in an SS-OCT system, the method reported here does not require over-sampling, thus greatly reducing the demand for digitization, data processing and storage speed. The Rt-UKSS method is adaptive and applicable to a generic SS-OCT system of a wide range of A-scan rates without special adjustment. We successfully implemented the Rt-UKSS method in an SS-OCT system based on a Fourier-domain mode-locked laser (FDML) of a 40-kHz scanning rate. Real-time imaging of biological tissues using such a system was demonstrated with a measured axial resolution of 9.3 μm and detection sensitivity greater than 120dB.

Depth-encoded all-fiber swept source polarization sensitive OCT

“…After further high-pass filtering (SHP-400 + , 395-3200MHz, Mini-circuits) and amplifying (ZFL-1000 + , Mini-circuits), the doubled clock was connected to an electric switch (ZYSWA-2-50DR, Mini-circuits) and mixed with a fixed frequency dummy clock generated by a Voltage Controlled Oscillator (ZX95-2500W-S + , Mini-circuits). The dummy clock was required by the DAQ in order to continuously acquire the data [65]. The combined RF output from the switch was further high-pass filtered (SHP 100 + , 90-2000MHz, Minicircuits) and used as the final clock input to the DAQ.…”

Fiber-based polarization-sensitive OCT for birefringence imaging of the anterior eye segment

“…If the frequency-swept laser has high nonlinearity of the optical frequency sweep, the multiplied clock can be distorted. In the case of frequency multiplexing with an electric 90-degree phase shifter [34], the applicability is also limited by frequency dependence of the electric phase shifter.…”

Swept source optical coherence microscopy using a 1310 nm VCSEL light source

“…The optical path lengths and electrical cable and circuit delays in the imaging arm were carefully matched to that of the MZI clock arm to ensure that the clock timing was correct. The SS-OCM fringes were sampled linear in wavenumber, thus eliminating the need for computationally intensive time to wavenumber resampling and interpolation in postprocessing [28]. Furthermore, optical clocking provides stable acquisition of fringes and is insensitive to slow drift or sweep-to-sweep variations of the light source.…”