Topic
Speckle imaging
About: Speckle imaging is a research topic. Over the lifetime, 3730 publications have been published within this topic receiving 62354 citations.
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TL;DR: In this paper, the statistical properties of dynamic speckles produced by a moving diffuse object were reviewed by providing the space-time correlation function and the power spectrum of speckle-intensity fluctuation for five combined cases of both the optical configuration and the illumination light.
Abstract: The statistical properties of dynamic speckles produced by a moving diffuse object were reviewed by providing the space–time correlation function and the power spectrum of speckle-intensity fluctuation for five combined cases of both the optical configuration and the illumination light. In the optical configuration, three kinds of geometry (free-space, single-lens, and double-lens) were taken, and three kinds of illumination light (a Gaussian beam, a plane-wave beam, and a Gaussian Schell-model beam) were used. Consequently, it was shown that the cross-correlation function and the power spectrum are both Gaussian under some assumptions. From the dynamic properties, two types of speckle motion, boiling and translation, were also evaluated for various conditions of object motion, optical configuration, and illumination light.
209 citations
TL;DR: In this paper, a new technique of high-resolution imaging through atmospheric turbulence is described, where short-exposure images are recorded, but in addition the associated wave fronts are measured by a Hartmann-Shack wave-front sensor.
Abstract: A new technique of high-resolution imaging through atmospheric turbulence is described. As in speckle interferometry, short-exposure images are recorded, but in addition the associated wave fronts are measured by a Hartmann–Shack wave-front sensor. The wave front is used to calculate the point-spread function. The object is then estimated from the correlation of images and point-spread functions by a deconvolution process. An experimental setup is described, and the first laboratory results, which prove the capabilities of the method, are presented. A signal-to-noise-ratio calculation, permitting a first comparison with the speckle interferometry, is also presented.
206 citations
TL;DR: In this paper, the maximum speckle contrast reduction for a given system was derived, and two novel approaches to achieve the maximum reduction were introduced, and the Hadamard diffuser was applied to the GLV TM.
Abstract: Speckle arises when coherent light scattered from a rough surface is detected by an intensity detector that has a finite aperture, such as an observer. In a laser projection display, the presence of speckle tends to mask the image information and therefore its reduction is highly desirable. Speckle contrast reduction is based on averaging a number of speckle configurations within the spatio-temporal resolution of the detector through diversification of the light parameters - angle, polarization, and wavelength. The maximum speckle contrast reduction for a given system will be derived, and two novel approaches to achieve the maximum reduction will be introduced. Application to the Grating Light Valve (GLV TM) laser projection system using the Hadamard diffuser has resulted in a suppression to 8% residual speckle contrast.
202 citations
TL;DR: Digital speckle-pattern interferometry systems for automatic measurement of deformations of a diffuse object are presented, which are based on a fringe scanning method with phase-shifted Speckle interferograms.
Abstract: Digital speckle-pattern interferometry systems for automatic measurement of deformations of a diffuse object are presented, which are based on a fringe scanning method with phase-shifted speckle interferograms. A digital speckle pattern before deformation of an object is recorded in the mass storage device of a computer facility. After deformation, four digital speckle patterns are recorded as changing the phase of reference light such as 0, π/2, π, and 3π/2, respectively. Four speckle interferograms, whose phases are shifted by 0, π/2, π, and 3π/2, are generated by calculating the square of the differences between speckle patterns before and after deformation. These interferograms are low-pass filtered to reduce speckle noise. The calculation of the arctangent with four phase-shifted speckle interferograms gives the optical path difference which is proportional to the deformation. A correction of the discontinuity of the calculated phase gives the numerical data of the deformation in the whole object area. Some experimental results for the measurement of out-of-plane, in-plane, and 3-D deformations are presented.
201 citations
TL;DR: A new image-shearing camera which focuses two laterally sheared images at the film plane and becomes a shearing interferometer, which directly measures the derivatives of the surface displacements.
Abstract: This paper describes a new image-shearing camera which focuses two laterally sheared images at the film plane. With coherent illumination, this camera becomes a shearing interferometer, which directly measures the derivatives of the surface displacements. This strain measuring tool enjoys several advantages over the conventional, holographic, and speckle interferometry, namely, (1) better fringe quality (than speckle interferometry); (2) does not require special vibration isolation; (3) very simple optical setup; (4) direct determination of strains; and (5) extended controllable range of sensitivity.
201 citations