Full-field optical microextensometer based on waveguide grating interferometry

Several versions of grating interferometers (GI) with conjugated wavefronts, specially adopted for in-plane displacement measurements of microelements or microregions at larger specimens, have been proposed including four-beam three mirror GI, Czamek's interferometer or fiber optics based GI. Recently the grating interferometers based on the concept of guiding the light in a waveguide (block of glass) have been developed. Such design is especially useful to combine the measurement module with optical microscope. In the paper, we propose two versions of new compact, sensor-like optical microextensometers based on the waveguide grating interferometry. The microextensometers consist of the interferometer head integrated with illumination and detection modules, so that it can work without any microscope. The compact and portable design (using the wire-less CCD camera) enables to use it outside the laboratory, e.g. directly on the engineering objects under test. The two GI versions are devoted to: periodical measurements and constant monitoring of a reference (DOE) structure attached to an object. In the paper the concept and design of both sensors is presented together with selected numerical simulations of waveguide plate.