Digital speckle technique uses a laser, a CCD camera, and digital processing to generate interference fringes at the television framing rate. Its most obvious advantage is that neither darkroom facilities nor photogra...Digital speckle technique uses a laser, a CCD camera, and digital processing to generate interference fringes at the television framing rate. Its most obvious advantage is that neither darkroom facilities nor photographic wet chemical processing is required. In addition, it can be used in harsh engineering environments. This paper discusses the strengths and weaknesses of three digital speckle methodologies. (1) Digital speckle pattern interferometry (DSPI) uses an optical polarization phase shifter for visualization and measurement of the density field in a flow field. (2) Digital shearing speckle interferometry (DSSI) utilizes speckle\|shearing interferometry in addition to optical polarization phase shifting. (3) Digital speckle photography (DSP) with computer reconstruction. The discussion describes the concepts, the principles and the experimental arrangements with some experimental results. The investigation shows that these three digital speckle techniques provide an excellent method for visualizing flow fields and for measuring density distributions in fluid mechanics and thermal flows. 展开更多
Two speckle patterns are recorded using a video cameracorresponding to undisplaced and displaced states into the memory ofa computer. After one pattern is added to another, the displacementof the measured points can b...Two speckle patterns are recorded using a video cameracorresponding to undisplaced and displaced states into the memory ofa computer. After one pattern is added to another, the displacementof the measured points can be calculated by using the Fouriertransform. The expression of displacement field is deduced fornon-uniform displacement, and as an example, a rotatanle disc istested for illustration. The re- sults prove that the present methodis promising.展开更多
The refractive index of a liquid medium is an important optical parameter since it exhibits the optical properties of the liquid. Its values are often required to interpret various types of spectroscopic data. The int...The refractive index of a liquid medium is an important optical parameter since it exhibits the optical properties of the liquid. Its values are often required to interpret various types of spectroscopic data. The intensity distribution and contrast of image speckle patterns obtained for Zamzam, bottled drinking and distilled waters are investigated on a computer as a function of six discrete wavelengths across the visible spectrum. The present novel computer simulation speckle photography using Fourier transform study and the new theoretical background have been confirmed with previous experimental results. Uncertainty of refractive index measurements was studied on a wide range of discrete wavelengths using the computer simulation and the new theoretical formulae.展开更多
In this work, an experimental approach of speckle photography was used for measuring birefringence of thermotropic liquid crystals mixtures at different wavelengths in the visible region. Also the dispersion relations...In this work, an experimental approach of speckle photography was used for measuring birefringence of thermotropic liquid crystals mixtures at different wavelengths in the visible region. Also the dispersion relations were investigated. The values of the refractive indices were measured for these mixtures of thermotropic liquid crystals in isotropic and liquid crystal phase at different wavelengths. The effect of the end group of these LCs used on the values of birefringence was investigated and discussed.展开更多
In this work, an experimental approach was used for measuring birefringence of thermotropic liquid crystal materials at different wavelengths in the visible region by using speckle interferometry. Also the values of t...In this work, an experimental approach was used for measuring birefringence of thermotropic liquid crystal materials at different wavelengths in the visible region by using speckle interferometry. Also the values of the refractive indices were measured for these thermotropic liquid crystal materials in isotropic and liquid crystal phases at different wave-lengths. Temperature dependency of the refractive indices for each LC sample at certain wavelengths was investigated in the isotropic and in LC phases.展开更多
文摘Digital speckle technique uses a laser, a CCD camera, and digital processing to generate interference fringes at the television framing rate. Its most obvious advantage is that neither darkroom facilities nor photographic wet chemical processing is required. In addition, it can be used in harsh engineering environments. This paper discusses the strengths and weaknesses of three digital speckle methodologies. (1) Digital speckle pattern interferometry (DSPI) uses an optical polarization phase shifter for visualization and measurement of the density field in a flow field. (2) Digital shearing speckle interferometry (DSSI) utilizes speckle\|shearing interferometry in addition to optical polarization phase shifting. (3) Digital speckle photography (DSP) with computer reconstruction. The discussion describes the concepts, the principles and the experimental arrangements with some experimental results. The investigation shows that these three digital speckle techniques provide an excellent method for visualizing flow fields and for measuring density distributions in fluid mechanics and thermal flows.
文摘Two speckle patterns are recorded using a video cameracorresponding to undisplaced and displaced states into the memory ofa computer. After one pattern is added to another, the displacementof the measured points can be calculated by using the Fouriertransform. The expression of displacement field is deduced fornon-uniform displacement, and as an example, a rotatanle disc istested for illustration. The re- sults prove that the present methodis promising.
文摘The refractive index of a liquid medium is an important optical parameter since it exhibits the optical properties of the liquid. Its values are often required to interpret various types of spectroscopic data. The intensity distribution and contrast of image speckle patterns obtained for Zamzam, bottled drinking and distilled waters are investigated on a computer as a function of six discrete wavelengths across the visible spectrum. The present novel computer simulation speckle photography using Fourier transform study and the new theoretical background have been confirmed with previous experimental results. Uncertainty of refractive index measurements was studied on a wide range of discrete wavelengths using the computer simulation and the new theoretical formulae.
文摘In this work, an experimental approach of speckle photography was used for measuring birefringence of thermotropic liquid crystals mixtures at different wavelengths in the visible region. Also the dispersion relations were investigated. The values of the refractive indices were measured for these mixtures of thermotropic liquid crystals in isotropic and liquid crystal phase at different wavelengths. The effect of the end group of these LCs used on the values of birefringence was investigated and discussed.
文摘In this work, an experimental approach was used for measuring birefringence of thermotropic liquid crystal materials at different wavelengths in the visible region by using speckle interferometry. Also the values of the refractive indices were measured for these thermotropic liquid crystal materials in isotropic and liquid crystal phases at different wave-lengths. Temperature dependency of the refractive indices for each LC sample at certain wavelengths was investigated in the isotropic and in LC phases.
