Full range complex spectral domain optical coherence tomography without additional phase shifters

Abstract

We demonstrate a new full range complex spectral domain optical coherence tomography (FRC SD-OCT) method. Other than FRC SD-OCT systems reported in literature, which employed devices such as electro-/acousto optic modulators or piezo-driven mirrors providing the phase modulations necessary for retrieval of the complex-valued signal, the system presented works without any additional phase shifting device. The required phase shift is introduced by the galvanometer scanner used for transversally scanning the sample beam. By means of a slight displacement of the probe beam with respect to the scanning mirror's pivot axis, the sample arm length and thus the phase is continuously modulated as the beam is scanned in lateral direction. From such modulated spectral data, the complex-valued data yielding a twofold increase of accessible depth range can be calculated using an algorithm based on the Hilbert transform. To demonstrate the performance of our method quantitative measurements of the suppression of mirror images as a function of induced phase shift were performed. In order to validate the FRC SD-OCT technique for high-speed imaging of biological tissue, we present full-range images of the human anterior chamber in vivo.

Single-step method for fiber-optic probe-based full-range spectral domain optical coherence tomography

“…In an off-axis galvano scanner, when the maximum scanning angle θ is assumed small enough, the phase shift at the nth position in the lateral direction is calculated as [17] φ n 4πaθ Nλ n;…”

“…In this case, the complex-conjugate image can be eliminated without giving up the measurement time. Among the single-frame full-range methods, the Yasuno's BM scan [13] and Wang's Hilbert transform [14] methods in particular have been employed by many groups [16][17][18][19][20]. In practical realization, the phase-shifting method using an off-axis galvano scanner, without any phase shifting in the reference arm, was developed [16][17][18].…”

Complex Conjugate Resolved Retinal Imaging by One-micrometer Spectral Domain Optical Coherence Tomography Using an Electro-optical Phase Modulator

“…To eliminate these artifacts, several techniques including phase-shifting methods [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23], a polarization based demodulation method [24], and a 3 × 3 fiber coupler based method [25] have been proposed. By obtaining the full complex interferogram, the complex ambiguity problems of SD-OCT can be solved.…”

“…Thus the temporal response is quite poor in high speed SD-OCT applications. Another approach to perform phase modulation is based on transverse scanning by a scanner [19][20][21]. The advantage of this method is that the phase modulation can be performed without any additional components.…”

Artifact removal in Fourier-domain optical coherence tomography with a piezoelectric fiber stretcher

“…It came to our attention that three articles [14][15][16] that used a similar approach to ours to achieve fullrange complex FD-OCT imaging have been published during the reviewing process of this letter. However, these papers use the galvanometer scanning system to perform the transverse modulation and are applied to SD-OCT systems.…”