Multi-Wavelengths Michelson Interferometer Based Spatial Phase Shift Shearography with Color Camera

The paper describes the use of a color camera for spatial phase shift shearography according to the carrier frequency method, whereby the focus is on measurement stability and practical usability. The basics are derived from the simple and extremely robust Michelson interferometer setup with spatial aperture and quality criteria are formulated according to the achievable result quality. The state of research of Multi-Wavelengths application is shown in general as well as in a publication, which serves as a further basis for comparison. The use of three laser sources and a Bayer-Matrix RGB color camera is considered to be the most effective method for the following development. For this purpose, the 3 out-of-plane illumination arrangement is used, which provides the three separate results in the spatial directions in only one measurement (for shear direction in x). The conditions and the special features of the spatial phase shift with a color camera are discussed and theoretical comparisons to the classical application with a black and white camera are made. On an experimental test, the high-resolution quality and usability of the presented method (3 Out-of-Plane Multi-Wavelengths RGB Camera spatial phase shift shearography) is demonstrated and validated. Prospective considerations are the extension to dual-shear applications (shear direction in x and in y simultaneously).