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Retardation

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Yoshiaki Yasuno – One of the best experts on this subject based on the ideXlab platform.

Jing-fung Lin – One of the best experts on this subject based on the ideXlab platform.

Shuichi Makita – One of the best experts on this subject based on the ideXlab platform.

  • bayesian maximum likelihood estimator of phase Retardation for quantitative polarization sensitive optical coherence tomography
    Optics Express, 2014
    Co-Authors: Deepa Kasaragod, Shuichi Makita, Shinichi Fukuda, Simone Beheregaray, Tetsuro Oshika, Yoshiaki Yasuno
    Abstract:

    This paper presents the theory and numerical implementation of a maximum likelihood estimator for local phase Retardation (i.e., birefringence) measured using Jones-matrix-based polarization sensitive optical coherence tomography. Previous studies have shown conventional mean estimations of phase Retardation and birefringence are significantly biased in the presence of system noise. Our estimator design is based on a Bayes’ rule that relates the distributions of the measured birefringence under a particular true birefringence and the true birefringence under a particular measured birefringence. We used a Monte-Carlo method to calculate the likelihood function that describes the relationship between the distributions and numerically implement the estimator. Our numerical and experimental results show that the proposed estimator was asymptotically unbiased even with low signal-to-noise ratio and/or for the true phase Retardations close to the edge of the measurement range. The estimator revealed detailed clinical features when applied to the in vivo anterior human eye.

  • monte carlo based phase Retardation estimator for polarization sensitive optical coherence tomography
    Optics Express, 2011
    Co-Authors: Lian Duan, Masahiro Yamanari, Shuichi Makita, Yoshiaki Yasuno
    Abstract:

    A Monte-Carlo-based phase Retardation estimator is developed to correct the systematic error in phase Retardation measurement by polarization sensitive optical coherence tomography (PS-OCT). Recent research has revealed that the phase Retardation measured by PS-OCT has a distribution that is neither symmetric nor centered at the true value. Hence, a standard mean estimator gives us erroneous estimations of phase Retardation, and it degrades the performance of PS-OCT for quantitative assessment. In this paper, the noise property in phase Retardation is investigated in detail by Monte-Carlo simulation and experiments. A distribution transform function is designed to eliminate the systematic error by using the result of the Monte-Carlo simulation. This distribution transformation is followed by a mean estimator. This process provides a significantly better estimation of phase Retardation than a standard mean estimator. This method is validated both by numerical simulations and experiments. The application of this method to in vitro and in vivo biological samples is also demonstrated.

  • generalized jones matrix optical coherence tomography performance and local birefringence imaging
    Optics Express, 2010
    Co-Authors: Shuichi Makita, Masahiro Yamanari, Yoshiaki Yasuno
    Abstract:

    Phase Retardation imaging including local birefringence imaging of biological tissues is described by generalized Jones-matrix optical coherence tomography. The polarization properties of a local tissue can be obtained from two Jones matrices that are measured by backscattered lights from the front and back boundaries of the local tissue. The error in the phase Retardation measurement due to background noise is analyzed theoretically, numerically, and experimentally. The minimum detectable phase Retardation is estimated from numerical simulations. The theoretical analysis suggests that the measurements with two orthogonal input polarization states have the lowest Retardation error. Local birefringence imaging is applied to the human anterior eye chamber and skin in vivo.

Sen Yung Lee – One of the best experts on this subject based on the ideXlab platform.

  • measurements of phase Retardation and principal axis angle using an electro optic modulated mach zehnder interferometer
    Optics and Lasers in Engineering, 2005
    Co-Authors: Sen Yung Lee, Jing-fung Lin
    Abstract:

    Abstract This paper presents an electro-optic modulated circular heterodyne modified Mach–Zehnder interferometer and a convenient two-phase signal-processing algorithm for the measurement of variations in the magnitude of phase Retardation and the angle of principal axis in optical materials. The developed method solves the problems of normalized intensity jump and limited phase Retardation measurement range associated with the circular heterodyne interferometer proposed previously. The present method uses a saw-tooth wave signal to drive an electro-optic (EO) modulator, and employs a lock-in amplifier to demodulate the principal axis angle and the phase Retardation. Specifically, this paper considers two main sources of measurement errors, namely the misorientation of the EO modulator and the reflection phase Retardation of the beam splitter. Furthermore, the study develops calibration procedures and identifies a means to minimize measurement errors induced by the reflection phase Retardation of the beam splitter.

  • Measurements of phase Retardation and principal axis angle using an electro-optic modulated Mach–Zehnder interferometer
    Optics and Lasers in Engineering, 2005
    Co-Authors: Sen Yung Lee, Jing-fung Lin
    Abstract:

    Abstract This paper presents an electro-optic modulated circular heterodyne modified Mach–Zehnder interferometer and a convenient two-phase signal-processing algorithm for the measurement of variations in the magnitude of phase Retardation and the angle of principal axis in optical materials. The developed method solves the problems of normalized intensity jump and limited phase Retardation measurement range associated with the circular heterodyne interferometer proposed previously. The present method uses a saw-tooth wave signal to drive an electro-optic (EO) modulator, and employs a lock-in amplifier to demodulate the principal axis angle and the phase Retardation. Specifically, this paper considers two main sources of measurement errors, namely the misorientation of the EO modulator and the reflection phase Retardation of the beam splitter. Furthermore, the study develops calibration procedures and identifies a means to minimize measurement errors induced by the reflection phase Retardation of the beam splitter.

  • Polariscope for simultaneous measurement of the principal axis and the phase Retardation by use of two phase-locked extractions
    Applied Optics, 2004
    Co-Authors: Jing-fung Lin, Sen Yung Lee
    Abstract:

    A novel polariscope with electro-optic modulation that is capable of simultaneous measurement of the principal axis and the phase Retardation of an optical linear birefringent medium by means of two phase-locked extractions is described. A phase compensator is used to suppress the transmission phase-Retardation effect of the beam splitter, thereby enhancing the precision of the measuring performance. The validity of the proposed design is demonstrated by measurement of the principal axis and phase Retardation of a quarter-wave plate sample. There are absolute errors of 0.25° on average and 0.58° at maximum in the principal-axis measurement and of 0.75° (0.83%) on average and 3.11° at maximum in the phase-Retardation measurement. Meanwhile, the Retardation error lies within a 5% uncertainty range of a commercial wave plate. The root-mean-square resolutions for the principal-axis angle and phase-Retardation measurements are 0.042° and 0.081°, respectively. Finally, the dynamic ranges of the principal-axis angle measurement and the phase-Retardation measurement extend as far as 180°.

Masahiro Yamanari – One of the best experts on this subject based on the ideXlab platform.

  • monte carlo based phase Retardation estimator for polarization sensitive optical coherence tomography
    Optics Express, 2011
    Co-Authors: Lian Duan, Masahiro Yamanari, Shuichi Makita, Yoshiaki Yasuno
    Abstract:

    A Monte-Carlo-based phase Retardation estimator is developed to correct the systematic error in phase Retardation measurement by polarization sensitive optical coherence tomography (PS-OCT). Recent research has revealed that the phase Retardation measured by PS-OCT has a distribution that is neither symmetric nor centered at the true value. Hence, a standard mean estimator gives us erroneous estimations of phase Retardation, and it degrades the performance of PS-OCT for quantitative assessment. In this paper, the noise property in phase Retardation is investigated in detail by Monte-Carlo simulation and experiments. A distribution transform function is designed to eliminate the systematic error by using the result of the Monte-Carlo simulation. This distribution transformation is followed by a mean estimator. This process provides a significantly better estimation of phase Retardation than a standard mean estimator. This method is validated both by numerical simulations and experiments. The application of this method to in vitro and in vivo biological samples is also demonstrated.

  • generalized jones matrix optical coherence tomography performance and local birefringence imaging
    Optics Express, 2010
    Co-Authors: Shuichi Makita, Masahiro Yamanari, Yoshiaki Yasuno
    Abstract:

    Phase Retardation imaging including local birefringence imaging of biological tissues is described by generalized Jones-matrix optical coherence tomography. The polarization properties of a local tissue can be obtained from two Jones matrices that are measured by backscattered lights from the front and back boundaries of the local tissue. The error in the phase Retardation measurement due to background noise is analyzed theoretically, numerically, and experimentally. The minimum detectable phase Retardation is estimated from numerical simulations. The theoretical analysis suggests that the measurements with two orthogonal input polarization states have the lowest Retardation error. Local birefringence imaging is applied to the human anterior eye chamber and skin in vivo.

  • phase Retardation measurement of retinal nerve fiber layer by polarization sensitive spectral domain optical coherence tomography and scanning laser polarimetry
    Journal of Biomedical Optics, 2008
    Co-Authors: Masahiro Yamanari, Shuichi Makita, Masahiro Miura, Toyohiko Yatagai, Yoshiaki Yasuno
    Abstract:

    Phase Retardation of in vivo human retinal nerve fiber layer (RNFL) is quantitatively measured by two methods—polarization-sensitive spectral-domain optical coherence tomotomography (PS-SD-OCT) and scanning laser polarimetry (SLP). An en face cumulative phase Retardation map is calculated from the three-dimensional (3-D) phase Retardation volume of healthy and glaucomatous eyes measured by PS-SD-OCT. It is shown that the phase Retardation curves around the optic nerve head measured by PS-SD-OCT and SLP have similar values except near the retinal blood vessels. PS-SD-OCT can measure the cumulative phase Retardation of RNFL as well as SLP, which will allow the evaluation of RNFL for glaucomatous eyes.