Self-spectral calibration for spectral domain optical coherence tomography

Xianling Zhang,Wanrong Gao,Chaoliang Chen,Jiuling Liao,Haiyi Bian

doi:10.1117/1.oe.52.6.063603

Abstract

A different real-time self-wavelength calibration method for spectral domain optical coherence tomography is presented in which inter- ference spectra measured from two arbitrary points on the tissue surface are used for calibration. The method takes advantages of two favorable conditions of optical coherence tomography (OCT) signal. First, the signal back-scattered from the tissue surface is generally much stronger than that from positions in the tissue interior, so the spectral component of the surface interference could be extracted from the measured spectrum. Second, the tissue surface is not a plane and a phase difference exists between the light reflected from two different points on the surface. Compared with the zero-crossing automatic method, the introduced method has the advantage of removing the error due to dispersion mis- match or the common phase error. The method is tested experimentally to demonstrate the improved signal-to-noise ratio, higher axial resolution, and slower sensitivity degradation with depth when compared to the use of the zero-crossing method and applied to two-dimensional cross-sectional images of human finger skin. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI. (DOI:

Highlights

Spectral domain optical coherence tomography (SDOCT) is a noninvasive, noncontact imaging modality,[1,2,3,4] in which the depth profile of the tissue is retrieved by performing inverse Fourier transform of the interference signal generated by the light back-scattered from the interior of the sample
One limitation of SDOCT is that the spectrum is sampled uniformly in wavelength and unevenly sampled in wavenumber space (k-space) which leads to variations of the axial resolution and the image quality along with the axial or A-scan direction
The algorithm used in Ref. 16 is effective and simple and can achieve calibration with high precision. This method is inherently unreliable in the cases where there are some large phase errors that arise from a large polarization mode dispersion mismatch between the reference arm and the sample arm, or when the phases of the calibration spectrum are contaminated by noises

Summary

Introduction

Spectral domain optical coherence tomography (SDOCT) is a noninvasive, noncontact imaging modality,[1,2,3,4] in which the depth profile of the tissue is retrieved by performing inverse Fourier transform of the interference signal generated by the light back-scattered from the interior of the sample. 13 and 14, calibration methods without the need of external devices were proposed In these methods, the wavelength assignments are obtained with the help of the linear relationship between phase or phase difference of interference spectra and the wavenumber on CCD. They need separate measurement steps which may cause errors in calibration data because of environmental temperature fluctuation effects on the system or poor stability of handling practices. The algorithm used in Ref. 16 is effective and simple and can achieve calibration with high precision This method is inherently unreliable in the cases where there are some large phase errors that arise from a large polarization mode dispersion mismatch between the reference arm and the sample arm, or when the phases of the calibration spectrum are contaminated by noises. The tissue surface is not a plane, so there is phase difference between the light reflected from two arbitrary transverse points on the surface

Principle

System SNR and Axial Resolution Improvement

Comparison with Zero-Crossing Method

Conclusions