Topic
Speckle imaging
About: Speckle imaging is a research topic. Over the lifetime, 3730 publications have been published within this topic receiving 62354 citations.
Papers published on a yearly basis
Papers
More filters
TL;DR: In this article, the phase and gradient of displacement amplitude of a vibrating object using continuous wave illumination in a path length imbalanced speckle shearing interferometer was measured using laser diode emission wavelength modulation.
Abstract: Laser diode emission wavelength modulation is demonstrated as a technique for measuring the phase and gradient of displacement amplitude of a vibrating object using continuous wave illumination in a path length imbalanced speckle shearing interferometer The unwanted mismatch in the magnification of the two images in the shearing interferometer and sensitivity to radial shear introduced by a path length imbalance is overcome by the use of a transparent block of high refractive index in one path in the interferometer
20 citations
TL;DR: A phase-measuring fiber optic electronic speckle pattern in-terferometer (ESPI) was recently constructed and demonstrated as mentioned in this paper, where phase stepping is introduced by stretching the fiber wrapped around a piezoelectric transducer.
Abstract: . A phase-measuring fiber optic electronic speckle pattern in- terferometer (ESPI) was recently constructed and demonstrated. In thisarrangement, phase stepping is introduced by stretching the fiber wrappedaround a piezoelectric transducer. Calibration of the phase step is criticalin phase measurement techniques for obtaining good phase plots. Meth-ods used for calibrating the stretcher are outlined and the drifts in thephase caused by fluctuations in temperature and mechanical stressesare discussed. Ways to minimize this drift are also presented. Subject terms: speckle interferometry; electronic speckle pattern interferometry.Optical Engineering 31(2), 315-321 (February 1992).phase step calibration is important in order to obtain error- free phase maps. Different methods for calibrating the piezoelectric transducer (PZT) in an interferometric arrangement13 as well as in a fiber optic interferometric sensor arrangement14 have been developed. Methods suchas phase-lock, sinusoidal extrema sensing, and employingsoftware routines to evaluate the phase from equations andintensity values are successful with specular interferometricfringes. On the other hand, the ESPI fringes are speckled.Even though good calibration can be obtained with phase-lock and sensing methods ,
20 citations
TL;DR: In this paper, the authors describe the speckle interferometer of the BTA 6m telescope of the SAO RAS based on a new detector with an electron multiplication CCD.
Abstract: The description is given for the speckle interferometer of the BTA 6-m telescope of the SAO RAS based on a new detector with an electron multiplication CCD. The main components of the instrument are microscope objectives, interference filters and atmospheric dispersion correction prisms. The PhotonMAX-512B CCD camera using a back-illuminated CCD97 allows up to 20 speckle images (with 512$\times$512 pix resolution) per second storage on the hard drive. Due to high quantum efficiency (93% in the maximum at 550 nm), and high transmission of its optical elements, the new camera can be used for diffraction-limited (0.02$''$) image reconstruction of $15^{m}$ stars under good seeing conditions. The main advantages of the new system over the previous generation BTA speckle interferometer are examined.
20 citations
TL;DR: An imaging technique to measure static surface displacements of electronic components using a setup based on a Michelson interferometer to avoid the phenomenon of speckle and the drawbacks inherent to it is presented.
Abstract: We present an imaging technique to measure static surface displacements of electronic components. A device is supplied by a transient current that creates a variation of temperature, thus a surface displacement. To measure the latter, a setup that is based on a Michelson interferometer is used. To avoid the phenomenon of speckle and the drawbacks inherent to it, we use a light emitting diode as the light source for the interferometer. The detector is a visible CCD camera that analyzes the optical signal containing the information of surface displacement of the device. Combining images, we extract the amplitude of the surface displacement. Out-of-plane surface-displacement images of a thermoelectric device are presented.
20 citations
TL;DR: Improved quality of phase maps in pulsed digital holographic interferometry is demonstrated by finding the right reconstruction distance, which resulted in a significant improvement of the visual appearance of the phase maps.
Abstract: Improved quality of phase maps in pulsed digital holographic interferometry is demonstrated by finding the right reconstruction distance. The objective is to improve the optical phase information when the object under study is a phase object and when it is out of focus, leading to low contrast fringes in the phase map. A numerical refocusing is performed by introducing an ideal lens as a multiplication by a phase field in the Fourier domain, and then a region of maximum speckle correlation is found by comparing undisturbed and disturbed subimages in different refocused imaging planes. After finding the right reconstruction distance, a phase map of high visibility is constructed. By this technique a 30% reduction of the phase error for a flow of helium gas and a 50% reduction of the phase error for a weak thin lens were obtained, which resulted in a significant improvement of the visual appearance of the phase maps.
20 citations