Post-tuning of Sample Position in Common-path Swept-source Optical Coherence Tomography

Abstract

Common-path interferometers are widely used for endoscopic optical coherence tomography (OCT) because an arbitrary arm length can be chosen for the endoscopic imaging probe. However, the scheme suffers from the limited range of the sample position distance from the end of the imaging probe because the position between the reference reflector and the sample is limited by the optical path-length difference (OPD) to induce an interference signal. In this study, we developed a novel method for compensating the arbitrary sample position in common-path swept-source OCT by adding an extra Mach-Zehnder interferometer in the post-path of the interfered optical signal. Theoretical analysis and an experimental demonstration of imaging depth tuning for the flexible sample position of an endoscopic OCT image are discussed. After post-tuning of sample position distance, the positioning limitation between the reference reflector and the sample can be solved for various sample positions over a range of 26 mm for the cross-sectional images of a fish eye sample.

Double common-path interferometer for flexible optical probe of optical coherence tomography

“…2 . Although the extra delay distance, d 2 , may be implemented by other interferometers of Mach-Zehnder or Michelson type instead of common-path 2, the common-path interferometer with an identical objective lens has the advantage of enhanced environmental stability [ 5 ].…”

“…For achieving improved stability for the OCT imaging, same kind of an objective lens and a partial reflector were used in common-paths 1 and 2 because the similar optical beam condition of the objective lens and partial reflector between the two common-paths will reduce the mismatch of length, polarization, and dispersion condition of the interfered optical signal [ 5 ]. To reduce environmental vibration, the partial reflector and sample in common-path 1 were mounted on one stage.…”

“…Considering the reflectivity of mirror, R M is 1 in common-path 2, we can obtain the optimally enhanced sensitivity when the reflectivity of the partial reflector R P in common-path 2 is around 0.33 [ 4 ]. By using an additional coated reflector, we expect to enhance the sensitivity of the present method The location of the partial reflector along the focal beam also helped to control the reflected signal intensity from the partial reflector [ 5 ].…”

Wavelength-Swept Cascaded Raman Fiber Laser around 1300 nm for OCT Imaging

“…Around 1024 depth points were acquired for the series of images, and each image was composed of 512 (axial) × 256 (transverse) pixels. Figure 6 (a) shows a depth-encoded signal obtained using the discrete Fourier transform (DFT) for a sample comprising three cover glasses (4science, thickness of 160 µm) [22]. The measured thickness was 159.9 μm for the first cover glass.…”