Speckle imaging

About: Speckle imaging is a research topic. Over the lifetime, 3730 publications have been published within this topic receiving 62354 citations.

Phase-shifting algorithms for electronic speckle pattern interferometry.

Abstract: A set of innovative phase-shifting algorithms developed to facilitate metrology based on electronic speckle pattern interferometry (ESPI) are presented. The theory of a phase-shifting algorithm, called a (5,1) algorithm, that takes five phase-shifted intensity maps before a specimen is deformed and one intensity map after a specimen is deformed is presented first. Because a high-speed camera can be used to record the dynamic image of the specimen, this newly developed algorithm has the potential to retain the phase-shifting capability for ESPI in dynamic measurements. Also shown is an algorithm called a (1,5) algorithm that takes five phase-shifted intensity maps after the specimen is deformed. In addition, a direct-correlation algorithm was integrated with these newly developed (5,1) or (1,5) algorithms to form DC-(5,1) and DC-(1,5) algorithms, which are shown to improve significantly the quality of the phase maps. The theoretical and experimental aspects of these two newly developed techniques, which can extend ESPI to areas such as high-speed dynamic measurements, are examined in detail.

Predicting Creep Failure from Cracks in a Heterogeneous Material using Acoustic Emission and Speckle Imaging

Abstract: Powered by TCPDF (www.tcpdf.org) This material is protected by copyright and other intellectual property rights, and duplication or sale of all or part of any of the repository collections is not permitted, except that material may be duplicated by you for your research use or educational purposes in electronic or print form. You must obtain permission for any other use. Electronic or print copies may not be offered, whether for sale or otherwise to anyone who is not an authorised user. Viitanen, Leevi; Ovaska, Markus; Ram, Sumit Kumar; Alava, Mikko J.; Karppinen, Pasi

A Review of Speckle Photography and Interferometry

Abstract: Since its discovery in 1969, speckle interferometry has be-come a very active area of research, so much so that there now exists quite a collection of techniques that are applicable to a wide variety of problems. Because of the surprising versatility offered by such a wide range of techniques, the potential user of such technology may become con-fused as to what can and cannot be done, and, further, what process is suitable for what task. This review is provided, therefore, to set the various techniques into context, point out their similarities, and delineate their differences.

Automatic deformation analysis by a TV speckle interferometer using a laser diode.

Abstract: A phase-shifting TV speckle interferometer is developed by using the frequency modulation capability of a laser diode and is applied to automatic deformation measurements. Temperature modulation is used for generating the frequency shift of a laser diode. We store four speckle interferograms with relative phase differences of π/2 in a frame grabber by monitoring a phase-shift signal, which is obtained by integrating the fringe intensity over a local window. The optimum size of the local window is examined experimentally. Then, the optimum processing conditions for reducing the speckle noise in interferograms, including an averaging window size, are found. Experimental results of the automatic deformation analysis indicate a displacement accuracy of better than λ/30.

Reconstruction of sequential cardiac in-plane displacement patterns on the chest wall by laser speckle interferometry

Abstract: Time-average speckle interferometry has been applied to obtain displacement patterns on the chest wall produced by cardiac action, in the absence of breathing, during various phases of the cardiac cycle. This has been achieved by an electronic shutter, controlled by the electrocardiogram of the subject. The recorded holographic plates processed under identical conditions are scanned by the pointwise method to obtain the absolute displacements at various locations corresponding to the activities of the various cardiac chambers and valves. These data are transformed to a 40*30 matrix by an interpolation method and, from this, three-dimensional displacement plots are reconstructed by an IBM PC/AT computer. These patterns show the displacements over the entire cardiac area corresponding to the activities of various regions during the cardiac cycle. The apex and aortic valve areas show the maximum displacements during the systolic phase. During the diastolic phase the activities over the low-pressure atrial regions are also observed. The results obtained outline the functional details of the normal heart and the activities over various areas are in agreement with those obtained by other noncontact techniques. >