Full-depth spectral domain optical coherence tomography technology insensitive to phase disturbance

Abstract

To achieve full-depth spectral domain optical coherence tomography in the case of strong environmental disturbance, the iterative phase-shifting (IPS) method and modified dispersion-coded (MDC) method are proposed in this work. In IPS, the precise amount of phase shift is retrieved by iteration, and the direction of the phase shift is determined by dispersion compensation. Conjugate mirror items and noise can be simultaneously eliminated by two captured interferograms, whereas only one of them can be removed in the traditional phase-shift method with two interferograms. In MDC, they are removed through dispersion compensation and signal extraction with a single interferogram. Full-depth images of a glass slide, an onion, and a live fish eye are obtained by the two methods. The advantages and disadvantages of each method are analyzed and compared. IPS is found to be more effective for removing conjugate artifacts, whereas MDC is more conducive to real-time imaging. For a 2 mm × 3.6 mm image of a fish eye (200 depth scans and 1200 spectral sampling points per depth scan), the mirror image artifact is reduced by 28.55 dB in MDC and 41.53 dB in IPS. Processing times are 5.1 seconds (20 iterations) for the IPS method and 0.91 seconds for MDC.

Dual-Channel Spectral Domain Optical Coherence Tomography Based on a Single Spectrometer Using Compressive Sensing

“…The feasibility of the method of combining dual-channel SD-OCT with CS is demonstrated based on the results for a mirror, as shown in Figure 4. The dispersion compensation coefficients are obtained [30]: a2=7680×10−30,a3=376×10−45.…”

“…Figure 2a shows the position relationship between the two channels in imaging mode 1, and the intensity of backscattered signal from the out-of-focus scatters within the red dotted box are substantially suppressed by the confocal gate [33]. We assume the coordinate origin along the depth direction is at the focal spot for simplicity, and then the optical fields of the two reference lights can be expressed as [15] E1r=Rexpfalse[i2kdfalse]expfalse(iφfalse(kfalse)false)E2r=Rexpfalse[−i2kdfalse]expfalse(iφfalse(kfalse)false) where R is the reflectance of reference arm, k is the wave number, and phase φfalse(kfalse) is introduced due to dispersion in order to remove conjugated image [23,30]. The signals of two sample arms are E1s=true∫S1(z)exp[i2kz]dzE2s=true∫S2(z)exp[i2kz]dz in which S (z) is the amplitude of backscattered light field at a depth of z in sample.…”

“…In this paper, the CS algorithm is used to reconstruct the undersampled data. This is because the conjugate image is removed in this work by a dispersion encoding (DE) method that requires iteration [23,29,30], so it can be combined with the CS iterative algorithm. The method of combining DE and CS was described in our published work [23], in which full depth images can be reconstructed from undersampled data by only a few iterations, thereby greatly reducing processing time.…”

Structural and Functional Sensing of Bio-Tissues Based on Compressive Sensing Spectral Domain Optical Coherence Tomography

“…In order to reduce the data processing time, and to remove the conjugate images (another important factor affecting the imaging depth) [17,18], we propose to add the dispersion coding (DE) method to the recovery of under-sampled A-scan data in 2D CS-SDOCT in this work. DE is an effective technique for removing conjugated images present in standard SD-OCT systems [19,20,21,22]. Compared to other methods of removing conjugate images, such as phase shifting methods [17,23], modulation methods [24,25], etc., DE requires only one measurement and has inherent phase stability [19,20,21,22].…”

“…DE is an effective technique for removing conjugated images present in standard SD-OCT systems [19,20,21,22]. Compared to other methods of removing conjugate images, such as phase shifting methods [17,23], modulation methods [24,25], etc., DE requires only one measurement and has inherent phase stability [19,20,21,22]. The combination of DE and 1D CS-SDOCT has been described in our previous work [26], where under-sampling was only implemented in the A-scan, which results in the data not being completely compressed.…”