Fourier optics analysis of phase-mask-based path-length-multiplexed optical coherence tomography

Abstract

Optical coherence tomography (OCT) is an imaging technique that constructs a depth-resolved image by measuring the optical path-length difference between broadband light backscattered from a sample and a reference surface. For many OCT sample arm optical configurations, sample illumination and backscattered light detection share a common path. When a phase mask is placed in the sample path, features in the detected signal are observed, which suggests that an analysis of a generic common path OCT imaging system is warranted. In this study, we present a Fourier optics analysis using a Fresnel diffraction approximation of an OCT system with a path-length-multiplexing element (PME) inserted in the sample arm optics. The analysis may be generalized for most phase-mask-based OCT systems. A radial-angle-diverse PME is analyzed in detail, and the point spread function, coherent transfer function, sensitivity of backscattering angular diversity detection, and signal formation in terms of sample spatial frequency are simulated and discussed. The analysis reveals important imaging features and application limitations of OCT imaging systems with a phase mask in the sample path optics.

Scattering-Angle-Resolved Optical Coherence Tomography of a Hypoxic Mouse Retina Model

“…An integral component of the SAR-OCT system is a path length multiplexing element (PME), described in detail by Yin et al, 25 Wang et al, 11 and Gardner et al 13 The PME provides additional contrast to standard OCT images by separating sample path light into 3 different path lengths, each corresponding to a different angular range. Path length 1 ( L ; “Low”) is light that has scattered at generally low angles, whereas path lengths 2 ( H 2 ; “High 2”) and 3 ( H 3 ; “High 3”) contain light that has scattered at generally higher angles (Figure 2A).…”

μOCT imaging using depth of focus extension by self-imaging wavefront division in a common-path fiber optic probe

“…At each mode's focal plane, other modes present as a potential side-lobe or out-of-focus artifacts that could blur the in-focus mode. But since the SMF core spatially filters the backscattered light, off-axis scattering centers are strongly attenuated [20] and no significant side-lobe artifacts are observed as shown in Fig. 4 and Fig.…”

Design Considerations for Murine Retinal Imaging Using Scattering Angle Resolved Optical Coherence Tomography

“…Thus, each sub image in the OCT interferogram is separated vertically by 2.5 mm. A more rigorous Fourier optical analysis of the PME operation for imaging was previously published [33]. A Monte Carlo model was developed to determine the effect of PME center aperture size on the intensity of light in each pathlength.…”