Toshitaka Wakayama

Two-dimensional measurement of birefringence dispersion using spectroscopic polarized light

This paper describes a method and system for the measuring the two-dimensional distribution of birefringence dispersion. An optical arrangement consists of a white light source, parallel polarizers, a CCD camera, and an acousto-optic tunable filter for selecting wavelength of the incident light. The intensity of spectroscopic polarized light changes sinusoidally as a function of wave number, and its period changes slightly because of birefringence dispersion. The fast Fourier transform method is used to analyze the birefringence dispersion from the spectroscopic polarized light. One hundred twenty-eight captured images are used for the analysis. Some experimental results on 2-D birefringence dispersion distributions are shown for the demonstration of this method.

Birefringence dispersion measurement based on achromatic four points of geometric phase

Abstract. A measurement method for birefringence dispersion is pro-posed using geometric phase. The optical arrangement consists of awhite light source, polarizer, sample, quarter-wave plate, rotating ana-lyzer, such as in a Senarmont setup, and a spectrometer for the visiblespectrum from 450 to 750 nm. The experimental setup achieves a phaseshift via the geometric phase produced by a cyclic change of polarizationstate on a Poincare sphere. We can select four points of geometricphase when the analyzer is set at −45, 0, 45, and 90 deg. It is math-ematically demonstrated that these points of geometric phase are inde-pendent of wavelength from the calculation of spherical trigonometrydrawn on the Poincare sphere. The phase shifting technique using thesefour geometric phases is applied to measure birefringence dispersion.Polymer films and optical crystals as samples are experimentally dem-onstrated, and it is shown that the experimental results agree well withthe known quantities of retardation in the visible spectrum.

Real-time measurement for birefringence dispersion using double retarder

A real-time measurement method for both birefringence dispersion and azimuthal angle is described. An optical set-up of this measurement consists of a white light source, two polarizers and two reterders without any rotation. A spectroscopic intensity is detected by a spectrometer. It is modulated with two different frequencies along wave number. Only the single spectroscopic intensity is sufficient to determine the retardation and the azimuthal angle with wavelength-dependence using two amplitude spectrum and phase by the fast Fourier transform method. A birefringence measurement of a Babinet-Soleil compensator as a sample is demonstrated experimentally.

Birefringence dispersion measurement by geometric phase

A measurement method of birefringence dispersion by geometric phase is described. The measurement system consists of a polarizer, a quarter wave plate, a rotating analyzer and a spectrometer. The detected intensity by a spectrometer changes sinusoidaly along wave number. A phase shifting method is applied to analyze birefringence dispersion. The total amounts of phase change in all of wavelengths are same, because geometric phase produces by cyclic changes of a state of polarization on the Poincaré sphere. The birefringence dispersion of Babinet-Soleil compensator, polymer films and a liquid crystal phase modulator is measured. Compared measured these results with literature values of birefringence dispersion, measured data agrees well. The measurement results shown the birefringence dispersion measurement by geometric phase is available to practical applications.

Two-dimensional measurement of birefringence disperion using spectroscopic polarized light

This paper describes a method and system for two-dimensional measurement of birefringence dispersion with high-order and azimuthal direction. The system consists of a white light source, crossed polarizers and a detector carrying out the spectroscopic polarized light. A spectroscopic interferogram shows sinusoidaly in accordance with wave number change, and its period changes slightly because of dispersion of birefringence. The fast Fourier transform method is used to analyze the birefringence from the spectroscopic interferogram. One hundred and twenty-eight sets of images are used for birefringence analysis. Some results of 2-D birefringence dispersion distribution are shown for the demonstration of this method.

High-order birefringence and dispersion measurement using spectroscopy of polarized light

This paper describes a method and device for measurement of two-dimensional retardance and dispersion with high-order and azimuthal direction. The system consists of a white light source, crossed polarizers and a detector for spectroscopic polarized light. A spectroscopic interferogram shows sinusoidal to wave number change, and its period changes slightly because of dispersion of birefringence. Fourier transform method is used to analyze the birefringence from the spectroscopic interferogram. One hundred and twenty-eight sets of images are used for birefringence analysis. Some results of 2D birefringence distribution with dispersion are shown for the demonstration.

Displacement measurement by spectro-polarization modulator

We propose a novel spectro-polarization modulator which generates radial liner polarized light sorted along wavelength concentrically. It consists of a polarizer, a retarder with high order retardation, and a quarter wave plate. If we set the radial polarizer after the spectro-polarization modulator, we can observe spectroscopic color concentrically. A displacement measurement method is proposed using chromatic aberration method.