Refractive Index Measurements of Liquids Using Moiré Pattern
01 Jan 2020-pp 157-163
TL;DR: In this article, a novel technique for measurement of refractive index of different materials using moire pattern is proposed, which uses incoherent moire patterns that forms due to mechanical superposition of two periodic structures such as gratings or repetitive lines.
Abstract: In this chapter, a novel technique for measurement of refractive index of different materials using moire pattern is proposed. This method uses incoherent moire pattern that forms due to mechanical superposition of two periodic structures such as gratings or repetitive lines. The resultant low-frequency moire pattern, consisting of alternating bright and dark lines called ‘fringes’, are dependent on the refractive index of the intercepted medium between the periodic structures. It has been noticed that these fringes shift due to changes in refractive indices. Consequently, by measuring this shift, refractive indices of liquids, kept suitably within a designed optical set-up, can be calculated in the proposed technique. The technique is highly sensitive, so these measurements of refractive indices of different liquids can be used for measuring adulteration or other characterizations. Here only transparent liquid samples have been considered for this measurement and an accuracy of 10−2 after decimal in Refractive Index (R.I.) has been achieved.
References
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TL;DR: The moire fringes are generated by superimposing the Fourier image of the first grating on the second one in the interferometer to examine the deflection of light by the phase objects.
Abstract: In this paper, we describe deflection mapping of phase objects using a Talbot interferometer. To examine the deflection of light by the phase objects, the moire fringes are generated by superimposing the Fourier image of the first grating on the second one in the interferometer. The phase object is placed in front of the first grating. The light passing through the objects and impinging on the first grating produces the shifted Fourier image, and the resultant moire fringes give the deflection mapping, which depends on the distribution of the refractive index of the phase object. The experiments show deflection mapping of a piece of plastic plate and a candle flame. This technique is used for measuring the focal length of a lens.
88 citations
TL;DR: A novel method for measuring refractive index of gases and liquids is presented based on moire deflectometry by measuring the refractive Index of diluted sucrose solutions and of air at atmospheric pressure.
Abstract: A novel method for measuring refractive index of gases and liquids is presented based on moire deflectometry. We demonstrate this technique by measuring the refractive index of diluted sucrose solutions and of air at atmospheric pressure.
52 citations
TL;DR: In this paper, a small-angle measuring device utilizing moire fringe has been constructed for the absolute measurement of angular displacements smaller than 0.1 µrad using an optical filtering technique.
Abstract: A small-angle measuring device utilizing moire fringe has been constructed for the absolute measurement of angular displacements smaller than 0.1 µrad. Applying an optical filtering technique, the intensity of the moire fringe changes sinusoidally as a measuring mirror rotates; the apparatus is self-calibrated with an accuracy of 1%. A light emitting diode is used as the light source in order to reduce heat generation in the apparatus. The electrical noise in the output of the apparatus is about 10 µV which corresponds to an angular displacement of 60 prad. The short-term stability is about 0.6 nrad when the temperature changes are within 0.01°C, and the drift is 3 nrad/h. The measuring range is 4.5 µrad with an accuray of 1%.
6 citations
TL;DR: In this article, a simple and versatile, but also sensitive and accurate method of determining vibration amplitudes is presented, which consists of observing the slow motion of a moire pattern formed by the image of a signal grating projected on to an identical reference grating, illuminated by stroboscopic light.
Abstract: A simple and versatile, but also sensitive and accurate method of determining vibration amplitudes is presented. The method consists of observing the slow motion of a moire pattern formed by the image of a signal grating projected on to an identical reference grating, illuminated by stroboscopic light. The pitch of the image of the signal grating can be suitably adjusted to yield an optimum relation between line frequencies of the two gratings. Full control over the sensitivity of the system is therefore possible. The accuracy and resolution of the method are comparable with those of other known methods based on sophisticated vibration measuring equipment.
6 citations