Polarization-sensitive spectral-domain optical coherence tomography using a single line scan camera

Abstract

Polarization-sensitive optical coherence tomography can be used to measure the birefringence of biological tissue such as the human retina. Previous measurements with a time-domain polarization-sensitive optical coherence tomography system revealed that the birefringence of the human retinal nerve fiber layer is not constant, but varies as a function of location around the optic nerve head. Here we present a spectral-domain polarization-sensitive optical coherence tomography system that uses a spectrometer configuration with a single line scan camera and a Wollaston prism in the detection arm. Since only one camera has to be synchronized with other components in the system, the design is simplified considerably. This system is 60 times faster than a time-domain polarization-sensitive optical coherence tomography system. Data was acquired using concentric circular scans around the optic nerve head of a young healthy volunteer and the acquisition time for 12 circular scans was reduced from 72 s to 1.2 s.The acquired data sets demonstrate variations in retinal thickness and double pass phase retardation per unit depth that were similar to data from the same volunteer taken with a time-domain polarization-sensitive system. The double pass phase retardation per unit depth of the retinal nerve fiber layer varied between 0.18 and 0.40 degrees/μm, equivalent to a birefringence of 2.2 ⋅ 10 -4 and 4.8 ⋅ 10 -4 respectively, measured at 840 nm.

Henle fiber layer phase retardation measured with polarization-sensitive optical coherence tomography

“…Phase retardation measurements were performed with a spectral-domain PS-OCT system with a Wollaston prism in the spectrometer, designed after Cense et al [9]. In comparison to the previous design, the Wollaston prism was positioned between the collimator and the grating, so that a smaller sized and therefore less expensive Wollaston prism could be used [15].…”

“…In our previous PS-OCT work, we determined DPPR per unit depth of the retinal nerve fiber layer (RNFL) by fitting spatially averaged DPPR data with least squares [6][7][8][9]. A similar analysis was followed by Yamanari et al [10].…”

Single camera spectral domain polarization-sensitive optical coherence tomography using offset B-scan modulation

“…By utilizing the offset B-scan method [16][17][18], we eliminated the additional modulation devices in a previous implementation [15]. Because a common path was used in the detection arm for the two polarization channels, system alignment was much simplified than those required when splitting the two channels in the detection arm [13,14]. This simple system was demonstrated to be capable of acquiring in vivo 3D polarizationsensitive images at a speed of the 50k lines/sec, limited only by the camera speed.…”

“…PSOCT has been successfully applied in a variety of biomedical applications such as burn depth estimation in skin [6,7] and ophthalmology [8][9][10]. The recent development of PSOCT has been shifted to spectral domain implementation [11][12][13][14]11,15] due to its superior speed and sensitivity that are critical for in vivo three dimensional applications.…”

“…Baumann et al [13] used a polarization-sensitive beam splitter to direct the horizontal-and vertical-polarized components to two adjacent halves of a single spectrometer camera. Cense et al [14] reported a similar system where a Wollaston prism in the detection arm was used to direct the two polarization components to a single camera. Fan et al [15] later reported a different configuration that separated the two orthogonal polarization components in the reference arm instead of the detection arm.…”