Contouring by electronic speckle pattern interferometry employing dual beam illumination

Abstract

In this paper we extend and study the method for generating contours of diffuse objects employing a dual beam illumination coupled with electronic speckle pattern interferometry. The sensitivity and the orientation of the contour planes are analyzed. A novel method for tilting the planes of contours and experimental results incorporating phase shifting and fringe analysis are also presented. The theoretical and the experimental results show good agreement.

Measurement of strain distributions in mouse femora with 3D-digital speckle pattern interferometry

“…The phase change due to the movement of mirrors M1 and M2 is linked to a surface contour of the sample. Similar to deformation measurements, the phase change is quantified by the temporal phase shift method [29][30][31][32].…”

Geometry for contouring by electronic speckle pattern interferometry based on shifting illumination beams

“…The contour interval is d = A 12 , where A 12 is the equivalent wavelength of the two wavelengths, and the fringe sensitivity can be varied by altering the difference between the two wavelengths. 2 Another method involves deformation of the test object and using dual-beam illumination 3 to obtain correlation fringes. The contour interval in this case is d = X/(24t sin 0), where X is the wavelength of the illumination, t is the tilt of the object, and 0 is the illumination angle.…”

Contouring by electronic speckle pattern interferometry with quadruple-beam illumination

“…[1][2][3][4][5] Correlatio n fringes ar e shown afte r th e subtractio n o r addition o f the video signal s fro m tw o speckl e patterns. On e ca n obtai n the contou r dat a fro m th e correlatio n fringe s b y usin g a phase-shifting metho d an d algorithm.…”

“…On e ca n obtai n the contou r dat a fro m th e correlatio n fringe s b y usin g a phase-shifting metho d an d algorithm. 6 Th e existing contouring methods by ESPI consist o f using two-wavelengt h illumination 1 or altering the object illumination beam 2,3 in a conventiona l ESP I syste m wit h a smoot h interferenc e reference bea m an d alterin g th e object 4 o r shiftin g th e illumination beams 5 in a dual-beam system. We presen t a n inexpensiv e ESP I arrangemen t wher e nothing i s move d t o obtai n contou r fringes .…”

“…Thre e interferograms with a shifted phas e o f ττ/2 with respect to one othe r were used fo r evaluating the phases. 4 A 30 × 2 9 samplin g array wit h a gra y leve l o f 1 0 was employe d t o digitiz e th e interferograms; 3 × 3 and 5 × 5 convolution filterin g wa s used sequentiall y t o smoot h th e speckle s i n the interferograms. A naturall y supplementa l resul t i s show n b y a simila r arrangement wit h thre e illuminatio n beams .…”