We present the development of a single shot interferometric system based on polarization and diffractive elements recovered from spare computers. The use of salvaged lenses, beam splitter cubes and linear polarizers lower the cost of our system in comparison with those already reported. Our system is also capable of dynamic phase measurements with an accuracy comparable to similar implementations with high end manufactured optics. We report here our results obtained from four simultaneous interference patterns. The presented interferometer can be easily implemented for various applications in single shot polarizing phase shifting interferometry.
In optical metrology, the phase-shifting technique is used to retrieve the phase information from interferograms. Such displacement can be performed by mirrors attached to electromechanical devices (such as piezoelectric or moving mounts), gratings, or polarizing components, which need to be calibrated to associate the displacement of the device with respect to the induced phase shift. For this purpose, we present a closed-form formula to calculate of the original phase step between two randomly shifted fringe patterns by extending the Gram–Schmidt orthonormalization algorithm. To demonstrate its feasibility, we perform an evaluation that consists of three cases that represent different fringe pattern conditions. First, we evaluate the accuracy of the method in the orthonormalization process by estimating the test step using synthetic normalized fringe patterns with no background, a constant amplitude, and different noise levels. Second, we evaluate the formula with a variable amplitude function on the fringe patterns and a constant background. Third, we evaluate non-normalized noisy fringe patterns in which we include the comparison of prefiltering processes such as the Gabor filters bank, Hilbert–Huang transform, and isotropic normalization process and a high-pass filter to emphasize how they affect the calculation of the phase step.
In this work, we present a novel Panoramic Fringe Projection system (PFP) to retrieve the three-dimensional topography of quasi-cylindrical objects along their full length and around the entire circumference. The proposed procedure uses a 45° concave conical mirror to project a circular sinusoidal fringe pattern onto a specimen placed coaxially to the mirror and at the same time to image the modulated fringe pattern diffused from the object surface. In order to obtain the required sensitivity, an axicon is used to create a divergent fringe pattern with constant pitch. By processing the phase map, information on the radius over the full 360° surface of the sample can be obtained by using a single-view series of images captured from a single camera. To verify the feasibility of the PFP technique, a tubular sample with shape discontinuities has been tested. The proposed method demonstrated to be able to retrieve the accurate topography of quasi-axial-symmetric samples with complex geometries for a large variety of applications.
Stereo Vision is a powerful tool used to make a 360° scan of an object in order to obtain topography details
or getting the spatial position of interest points, but the process could be slow due to the computing time. In this
work we present the alternative of using high reflective markers, which are used as reference points to track an
object movement. The advantage of these markers is that their detection is faster than a full scene correlation and it
is done by comparing the position of the centroids of each marker without using pixel-pixel analysis.