Abstract

ABSTRACT We present a phase-resolved optical Doppler tomography (ODT) sys tem at 1310 nm using frequency domain method. Frequency domain phase-resolved ODT potentially allows for an increased longitudinal imaging range, signal-to-noise ratio and imaging acquisition rates, which can dramatically increase the measurable velocity dynamic range. A detailed derivation of phase-resolved frequency domain ODT and a measurement of flow through micro channel are presented. This technique can be used to quantify flow in integrated microfluidic devices in which complex three-dimensional structures and a wide velocity range are present. Keywords : Optical Doppler Tomography, Flowmetry INTRODUCTION Optical Doppler tomography (ODT) is a noninvasive diagnostic technique for imaging sample structure and the cross sectional velocity distribution of moving scattering media [1]. Early ODT systems were unable to achieve simultaneously both high imaging speed and high velocity sensitivity. Phase-resolved ODT [2,3] provides information on flow velocity and variance in this velocity and several clinical applications of phase-resolved ODT have been reported [3]. We have also applied this noninvasive imaging technique to quantify micro flow and the result is comparable to those obtained by conventional testing method [4]. Recently, frequency domain optical coherence tomography (OCT) has attracted great attention due to its intrinsic advantage in signal-to-noise ratio. Several research groups have shown that frequency domain OCT has a signal-to-noise ratio approximately 20 dB higher than that of time domain OCT [9-11]. In addition, frequency domain OCT does not require any axial scanning and the imaging speed is determined by either the electronic detection system or the tuning rate of a tunable laser [5-15]. Because parallel data acquisition can be implemented in frequency domain, high speed A-line data rate is possible. This provides phase-resolved ODT a better signal-to-noise ratio since the phase noise (caused by

Highlights

  • Optical Doppler tomography (ODT) is a noninvasive diagnostic technique for imaging sample structure and the cross sectional velocity distribution of moving scattering media [1]

  • We present phase-resolved optical Doppler tomography (ODT) images using frequency domain method at 1310 nm

  • To increase the signal-to-noise ratio in the ODT images, 30 sequential A-lines were used for the calculation of the phase shift of each A-line pixel

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Summary

INTRODUCTION

Optical Doppler tomography (ODT) is a noninvasive diagnostic technique for imaging sample structure and the cross sectional velocity distribution of moving scattering media [1]. Because parallel data acquisition can be implemented in frequency domain, high speed A-line data rate is possible This provides phase-resolved ODT a better signal-to-noise ratio since the phase noise Frequency domain ODT has advantages in applications where imaging speed and velocity dynamic range is important. We present phase-resolved ODT images using frequency domain method at 1310 nm At this wavelength, bigger penetration depth is expected in biological sample. The optical time delay is extracted by comparing the average phase change between two sequential complex time domain reflective signals ( i(t) ). Using the phase-resolved method, the phase change is determined by calculating the cross correlation function of two sequential complex spatial reflective signals [2,3], as described by equation (5). To increase the signal-to-noise ratio in the ODT images, 30 sequential A-lines were used for the calculation of the phase shift of each A-line pixel

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