Simultaneous measurement of small birefringence magnitude and direction in real time
TL;DR: In this article, a method to simultaneously measure the small birefringence magnitude and direction in real time is proposed, where the laser light passes through a circular polarizer and the sample successively is split into two subbeams by a beam splitter.
About: This article is published in Optics and Lasers in Engineering.The article was published on 2014-02-01. It has received 6 citations till now. The article focuses on the topics: Photoelastic modulator & Birefringence.
Citations
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TL;DR: The recent progress in optical polarimetry pertaining to the characterization of myocardial pathologies is reviewed while describing the underlying biological rationales that give rise to the optical imaging contrast in various pathologies of the myocardium.
Abstract: Myocardial infarction (MI), a cause of significant morbidity and mortality, is typically followed by microstructural alterations where the necrotic myocardium is steadily replaced with a collagen scar. Engineered remodeling of the fibrotic scar via stem cell regeneration has been shown to improve/restore the myocardium function after MI. Nevertheless, the heterogeneous nature of the scar patch may impair the myocardial electrical integrity, leading to the formation of arrhythmogenesis. Radiofrequency ablation (RFA) offers an effective treatment for focal arrhythmias where local heating generated via electric current at specific spots in the myocardium ablate the arrhythmogenic foci. Characterization of these myocardial pathologies (i.e., infarcted, stem cell regenerated, and RFA-ablated myocardial tissues) is of potential clinical importance. Optical polarimetry, the use of light to map and characterize the polarization signatures of a sample, has emerged as a powerful imaging tool for structural characterization of myocardial tissues, exploiting the underlying highly fibrous tissue nature. This study aims to review the recent progress in optical polarimetry pertaining to the characterization of myocardial pathologies while describing the underlying biological rationales that give rise to the optical imaging contrast in various pathologies of the myocardium. Future possibilities of and challenges to optical polarimetry in cardiac imaging clinics are also discussed.
13 citations
Cites methods from "Simultaneous measurement of small b..."
...In the context of these fast imaging approaches, various proposed polarimetry methods to measure linear retardance, both magnitude and direction simultaneously, in real time, may also help shaping its roots in clinics of cardiac imaging.(44,45) Integrating polarimetry imaging with other optical modalities such as diffuse reflectance imaging is another convincingly emerging direction to potentially enhance signal strength, particularly for intraoperative tissue characterization....
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TL;DR: In this paper, a real-time measurement of retardation and fast axis azimuth of wave plates is proposed, where the light emitted from the laser passes through a circular polarizer and the sample successively diffracted to three sub-beams by a grating.
Abstract: Real-time measurement of retardation and fast axis azimuth of wave plates is proposed. The light emitted from the laser passes through a circular polarizer and the sample successively. Then the beam is diffracted to three sub-beams by a grating. One sub-beam passes through a standard quarter-wave plate and then is split and analyzed by a Wollaston prism. The other two sub-beams are all directly split and analyzed by Wollaston prisms. Six intensities are simultaneously detected to calculate the retardation and the fast axis azimuth. Experiments show that for the quarter-wave plate the average and standard deviation of the retardation are 89.78° and 0.14°, respectively, and the maximum deviation of the fast axis azimuth is 0.6°; for the eighth-wave plate, the average and standard deviation of the retardation are 45.15° and 0.15°, respectively, and the maximum deviation of the fast axis azimuth is 0.53.
5 citations
TL;DR: In this article, a zero-order vortex half-wave retarder was used to measure phase retardation and fast axis angle of a wave plate by utilizing a radially polarized symmetric light beam.
Abstract: An alternative method is proposed for simultaneously measuring the phase retardation and fast axis angle of a wave plate by utilizing a radially polarized symmetric light beam. A horizontal polarized laser is passed through a spatial filter, a zero-order vortex half-wave retarder, for measuring the light beam. An analyzer and a charge-coupled device are used for the measurement. The charge-coupled device captures two intensity variation patterns before and after a wave plate to be tested is rotated by 45° in any initial fast axis angle direction. Through analysis of the intensity values, the phase retardation and fast axis angle of the wave plate to be tested can be accurately determined using mean calculation. To validate the proposed method, half-wave and quarter-wave plates were measured experimentally. The measurement errors of phase retardation and fast axis angle were approximately 0.087° and 0.094°, respectively.
4 citations
TL;DR: In this article, an interferometric method was proposed for the simultaneous measurement of phase retardation and fast-axis azimuth angle of a wave plate by using a Mach-Zehnder interferometer.
Abstract: In this study, an interferometric method was proposed for the simultaneous measurement of phase retardation and fast-axis azimuth angle of a wave plate by using a Mach–Zehnder interferometer. The w...
4 citations
TL;DR: In this article , the authors proposed a new interferometric method to determine the birefringence effects by measuring the transmitted wavefronts of the large optics, which are considered as bire-ringent samples.
Abstract: The polarization based phase shifting method is an effective way for dynamic measurements. However, when this technique is applied to the measurements of large optics, the interferometric results are easily limited by the birefringence of large optics. The birefringence changes the polarization states of reference light and test light, and brings constant polarization aberrations into the measurement results independent of the phase shifting procedure. In this article, the detailed theoretical analysis on the mechanism of polarization aberration is presented. Afterwards, we propose a new interferometric method to determine the birefringence effects by measuring the transmitted wavefronts of the large optics, which are considered as birefringent samples. Theoretical analysis shows that the polarization error in the linearly polarized system can be corrected by two independent measurements with orthogonal polarization states. The phase retardance can be obtained from the wavefront difference of the transmitted wavefronts when switching the polarization states of the incident lights. The birefringence distribution obtained is used to calibrate the polarization aberrations in the measurement result of a homemade large aperture measurement platform and the correction result is compared with the result via the wavelength tuning phase shifting method. The elimination of the polarization aberrations can be observed in the final results.
References
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TL;DR: In this article, the authors proposed image processing algorithms for measuring two-dimensional distributions of linear birefringence using a pair of variable retarders and obtained the lowest noise level of 0.036 nm.
Abstract: We propose image processing algorithms for measuring two-dimensional distributions of linear birefringence using a pair of variable retarders. Several algorithms that use between two and five recorded frames allow us to optimize measurements for speed, sensitivity, and accuracy. We show images of asters, which consist of radial arrays of microtubule polymers recorded with a polarized light microscope equipped with a universal compensator. Our experimental results confirm our theoretical expectations. The lowest noise level of 0.036 nm was obtained when we used the five-frame technique and four-frame algorithm without extinction setting. The two-frame technique allows us to increase the speed of measurement with acceptable image quality.
398 citations
TL;DR: A new type of polarized light microscope for fast and orientation‐independent measurement of birefringent fine structure has been developed and incorporates a precision universal compensator made from two liquid crystal variable retarders.
Abstract: A new type of polarized light microscope ('new pol-scope') for fast and orientation-independent measurement of birefringent fine structure has been developed. The design of the new pol-scope incorporates a precision universal compensator made from two liquid crystal variable retarders. A video camera and digital image processing system provide fast measurements of specimen anisotropy (retardance magnitude and azimuth) at all points of the image forming the field of view. The images document fine structural and molecular organization within a thin optical section of the specimen. The sensitivity of the current instrument is 0.1 nm of specimen retardance, measured with data gathered in 0.43 s at all 640 x 480 image points. Examples of birefringence measurements in biological (microtubule arrays) and industrial (magneto-optical disc substrate) specimens are presented.
320 citations
Book•
01 Jan 2003TL;DR: Polarized Light, Second Edition explores polarized light, its production, and its use, facilitating self-study without prior knowledge of Maxwell's equations as mentioned in this paper, and includes more than 2500 thoroughly updated figures and equations.
Abstract: Polarized Light, Second Edition explores polarized light, its production, and its use, facilitating self-study without prior knowledge of Maxwell's equations. This comprehensive second edition includes more than 2500 thoroughly updated figures and equations for easier understanding and application across various industries. It features new chapters on polarization by refraction and reflection, polarization elements, anisotropic materials, Stokes polarimetry, Mueller matrix polarimetry, the mathematics of the Mueller matrix. This edition also offers updated and expanded material on the derivation of the Fresnel equations with plots of the magnitude and phase of the reflection coefficients.
121 citations
TL;DR: The experiments illustrate the application of a dynamical encoding and information recovery scheme that is robust to perturbations of the communication channel, a standard single mode fiber.
Abstract: The fast, irregular, fluctuations of the state of polarization of light output from an erbium doper fiber ring laser are used to communicate digital information. The experiments illustrate the application of a dynamical encoding and information recovery scheme that is robust to perturbations of the communication channel, a standard single mode fiber. A fiber-optic polarization analyzer was used to measure and visualize the polarization dynamics at nanosecond time scales on the Poincare sphere.
88 citations
TL;DR: The two-wave-plate compensator technique is introduced for single-point retardation measurements and enables the measurement of a sample retardation with as little as 0.13% error and thus is more accurate than either the Brace-Kohler or the Sénarmont method.
Abstract: The two-wave-plate compensator (TWC) technique is introduced for single-point retardation measurements. The TWC method uses a known wave plate together with a wave plate of unknown retardation and produces a linearly polarized output that allows a null of intensity to be detected. The TWC method is compared both theoretically and experimentally with the existing Brace–Kohler and Senarmont methods. The resolution of the TWC is shown to be 0.02 nm. TWC enables the measurement of a sample retardation with as little as 0.13% error and thus is more accurate than either the Brace–Kohler or the Senarmont method.
53 citations