Using a Savart plate in optical metrology

in Proceedings of SPIE (2010, August), 7791

Non-contact optical measurement methods are essential tools in many industrial and research domains. A family of new non-contact optical measurement methods based on the polarization states splitting ... [more ▼]

Non-contact optical measurement methods are essential tools in many industrial and research domains. A family of new non-contact optical measurement methods based on the polarization states splitting technique and monochromatic light projection as a way to overcome ambient lighting for in-situ measurement has been developed1,2. Recent works3 on a birefringent element, a Savart plate, allow to build a more flexible and robust interferometer. This interferometer is a multipurpose metrological device. On one hand, the interferometer can be set in front of a CCD camera. This optical measurement system is called a shearography interferometer and allows to measure micro displacement between two states of the studied object under coherent lighting. On the other hand, by producing and shifting multiple sinusoidal Young’s interference patterns with this interferometer, and using a CCD camera, it is possible to build a 3D structured light profilometer. After giving the behavior of the Savart plate, an overview of the two devices will be given as well as their specifications and some applications. [less ▲]

Non destructive testing by digital shearography using a Savart plate

Poster (2009)

Shearography is a growing optical technique in the field of non-destructive testing (NDT). Hololab developed an out of plane, in line and almost common path interferometer based on polarization states ... [more ▼]

Shearography is a growing optical technique in the field of non-destructive testing (NDT). Hololab developed an out of plane, in line and almost common path interferometer based on polarization states separation using a coated prism for digital phase-shifting shearography. This setup is efficient but does not allow varying the shearing direction, that is an important parameter for defects detection and quantification. To overcome this disadvantage, the coated prism is substituted by a Savart plate device that allows scanning several shearing directions by rotating the device around the light propagation axis. Many advantages of the prism substitution are discussed. The behaviour of the Savart plate as a shearing device is experimentally analyzed to optimize its integration within the interferometer. Recorded phasemaps in NDT for different shearing directions are presented. [less ▲]

Out-of-plane displacement derivative measurement: comparison of results obtained by a shearographic interferometer using the separation of the polarization states and the finite element method

in Mathieu, P. (Ed.) Proceedings of Photonics North Conference 2006 (2006)

An original experimental setup for shearography with metrological applications is presented herein. The simplicity and the efficiency of the setup are provided by a shearing device, a prism that separates ... [more ▼]

An original experimental setup for shearography with metrological applications is presented herein. The simplicity and the efficiency of the setup are provided by a shearing device, a prism that separates the TE and TM polarization modes with a coating and a thin glass plate attached on its face. The temporal phase shifting method is applied through the use of a liquid crystal variable retarder. The use of this shearing device enables an in-line and almost-common path configuration for the shearing interferometer, a path that leads to high stability of the interferometer and a low sensitivity to external disturbances. In order to prove the efficiency and the accuracy of this speckle shearing interferometer, the out-of-plane displacement derivative relative to the shearing interferometry direction of a centrally loaded steel plate has been measured by the shearographic interferometer and then compared with the out-of-plane displacement derivative computed from the displacement field provided by the finite element method. The results are in good agreement. [less ▲]

Développement et première application d'une installation de shearographie

Master of advanced studies dissertation (2005)