Speckle imaging

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

Measurement of three-dimensional deformations using digital holography with radial sensitivity

Abstract: A measurement system based on digital holography for the simultaneous measurement of out-of-plane and radial in-plane displacement fields for the assessment of residual stress is presented. Two holograms are recorded at the same time with a single image taken by a digital camera, allowing the separate evaluation of in-plane and out-of-plane movement. An axis-symmetrical diffractive optical element is used for the illumination of the object, which causes radial sensitivity vectors. By the addition and, respectively, the subtraction, of the four phase maps calculated from two camera frames, the in-plane and out-of-plane deformation of an object can be calculated separately. The device presented is suitable for high-speed, high-resolution measurement of residual stress. In addition to the setup, first measurement results and a short comparison to a mature digital speckle pattern interferometry setup are shown.

Generalized Yamaguchi correlation factor for coherent quadratic phase speckle metrology systems with an aperture

Abstract: In speckle-based metrology systems, a finite range of possible motion or deformation can be measured. When coherent imaging systems with a single limiting aperture are used in speckle metrology, the observed decorrelation effects that ultimately define this range are described by the well-known Yamaguchi correlation factor. We extend this result to all coherent quadratic phase paraxial optical systems with a single aperture and provide experimental results to support our theoretical conclusions.

In-plane displacement and strain measurement by speckle interferometry and moire derivation

Abstract: The notion of the coefficient of correlation between two interfering wave fronts is applied to the study of fringe formation and visibility in speckle interferometry. The parameters affecting the visibility of the in-plane displacement fringes are analyzed in the case of an arbitrary displacement and deformation of the object surface. The influence of strain as well as defocusing on the visibility is explicated. Physical significance of the results is discussed. The work is partly backed by experimental investigation.

Experimental Analysis of Thermo‐mechanical Behaviour of Electronic Components with Speckle Interferometry

Abstract: Experimental investigations of thermo-mechanical behaviour of electronic components may help to prevent catastrophic in-service failures. Non-contact optical techniques such as speckle and moire interferometry are naturally suited for carrying out measurements on electronic equipment as they are non-invasive techniques and provide high-resolution full-field information on displacements. In spite of its inherent ability to measure deformations at the nanometer level, there are few examples of application of speckle interferometry to true monitoring of thermo-mechanical behaviour of electronic components in real time. For this reason, the paper presents a phase shifting electronic speckle pattern interferometry (PSESPI) experimental set-up developed in order to monitor the time evolution of thermal deformations in electronic components for aerospace applications submitted to normal or anomalous working conditions. Cyclic loads are also analysed to assess fatigue behaviour. Experimental results obtained for whole electronic boards and single components mounted on board fully demonstrate the capability of PSESPI to detect even small differences in thermo-mechanical response between normal and anomalous functioning.