Modulation of Moiré pattern using birefringent sample
15 Jun 2015-Vol. 9654, pp 120-123
TL;DR: In this paper, a birefringent lens was used to generate coherent and incoherent Moire patterns with and without analyzer, and mica sheets with opposite crystal axis to that of the lens were used to demonstrate the effect of thickness on phase retardation.
Abstract: Moire pattern, produced by the overlapping of two radially sheared beams emerging from two longitudinally shifted
focal points of a birefringent lens has been experimentally demonstrated. Coherent and incoherent Moire patterns are
generated with and without analyzer. Birefringent samples like mica sheets with opposite crystal axis to that of the
birefringent lens modulate the Moire pattern. Mica sheet of different thicknesses have been used to demonstrate the
effect of thickness on phase retardation, hence on fringe pattern. Experimentally birefringence has been calculated by
fringe analysis and compared with theoretically simulated birefringence.
References
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TL;DR: In this paper, a general mathematical technique for the solution of moire patterns produced by the overlapping of two figures is presented, applied to combinations of figures involving parallel lines, radial lines, and concentric circles including those in which the spacing is variable.
Abstract: A general mathematical technique for the solution of moire patterns produced by the overlapping of two figures is presented. The technique is applied to combinations of figures involving parallel lines, radial lines, and concentric circles including those in which the spacing is variable. When an equispaced parallel line figure is overlapped on a parallel line figure whose spacing is variable, the resultant moire pattern reveals the functional form of the variation.The theory of the measurement of refractive index gradients by the moire technique is presented. Three arrangements of the positions of the figures with respect to the sample are analyzed. One compact arrangement gives exclusively the refractive index gradient. The interpretation of moire patterns distorted by lenses is considered in terms of the properties of the lenses.The mathematical solutions of moire patterns are, in many cases, identical with those arising in physical problems. Examples are given for a number of phenomena arising in physical optics, hydrodynamics, and electrostatics.
222 citations
TL;DR: In this article, the general theory of moire patterns obtained from parallel rulings and concentric circles is presented, and the technique is demonstrated for the case of a constant refractive index gradient.
Abstract: The general theory of moire patterns obtained from parallel rulings and concentric circles is presented. Near superposition of a regular ruling on to parallel rulings of variable spacings results in a curved moire pattern which is functionally related to the deviation in spacings. When two figures consisting of uniformly spaced concentric circles are overlapped, the resulting moire patterns are hyperbolas defined by the center-to-center distance of the figures and the inter-ring spacing.Since very small relative displacements of the figures result in large changes in the moire pattern, this technique can be a sensitive detector of minute changes in refractive index and in refractive index gradient which bring about apparent relative displacement of the figures. The technique is demonstrated for the case of a constant refractive index gradient and for a variable refractive index gradient as encountered in diffusion measurements. Birefringence and dispersion can also be determined utilizing the moire method. Demonstration of the use of the moire technique for the evaluation of lenses is also presented.
123 citations
Additional excerpts
...Moreover, the sum moiré is given by ( ) n m 2 f 2 s 2 2 2 + = + + λ Δ η ζ (6)...
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TL;DR: In this paper, a channelled spectrum resulting from two-beam interference fringes is formed by illuminating an anisotropic material, placed between two crossed polarizers in front of a spectrograph, with a parallel beam of white light.
36 citations
TL;DR: In this article, the authors proposed two optical sensor structures based on Fabry-Perot resonator and fringes of equal thickness structure, which have high sensitivity to changes in the refractive index of the sample.
24 citations
TL;DR: Moire ray deflection analysis techniques can provide fast, simple, and sensitive quantitative methods for direct measurement of optical birefringence.
Abstract: Moire ray deflection analysis techniques can provide fast, simple, and sensitive quantitative methods for direct measurement of optical birefringence. Two of these techniques are described, analyzed, and demonstrated.
23 citations