We present a method to fully reconstruct real objects acquired by any means of digitalization and where many scans
from different views of point have been made. The current problem is modeled as an optimization problem and solved
with a Genetic Algorithm (GA) using a custom fitness function based in regular squared distance minimization (SDM).
We present examples to show the applicability of our method to reconstruct full objects as well as a possible application
in reverse engineering.
We present a new threshold technique based on the character grey level percentage. The method is used in the binary segmentation process of characters in a license plate recognition problem. In this case, image contrast problems (i.e. shadows) are found due to variations in the illumination. These image contrast problems generate bad character segmentation such that a binary threshold adaptive algorithm is required. The grey level percentage is calculated from the image histogram. This percentage is used to find the threshold value. Results of the binary threshold process over real license plate images are presented.
In the last years, Soft computing techniques, such as Genetic Algorithms, Neural Networks and Fuzzy systems, have been applied in different science areas. In this work, two applications of Genetic Algorithms in engineering and optics are presented. The Genetic Algorithms are optimization, search and learning machine techniques, which work in a random way. To achieve the problem solution by using of Genetic Algorithms, an iterative process should be developed. First, the problem to solve is modelled in a mathematical way by establishing of a fitness or objective function. After, a random initial population of strings (chromosomes) codifying problem solutions is generated, which samples the search solution space of the fitness function. Then, offspring populations are generated from previous one by using genetic operators: selection, crossover and mutation. In the selection process, possible solutions are chosen depending on their fitness function value. Then, in the crossover procedure, string segments of pairs of solutions are exchanged to generate the next population. Finally, some parameters in the offspring population are changed by mutation with a low probability. Results of the application of Genetic Algorithms to solve fringe analysis and nesting in finite materials problems are presented.
A fringe normalization procedure is presented in this paper. The main idea of the computer algorithm is to normalize the fringe pattern using spline interpolation functions. To achieve this, two splines are fitted using the maximum and minimum irradiance peaks detected over each fringe image line. Then, each pixel in the fringe image is interpolated and normalized by using of the values of the max and min splines. The fringe contrast is enhanced with an error around 1%. Preliminary results are presented.
In this paper we are going to review two interferometric techniques to demodulate a single fringe pattern containing closed fringes. It is well known that analyzing a single interferogram with spatial carrier is relatively easy . That is, whenever the modulating phase of the interferogram contains a linear component large enough to guarantee that the total modulating phase would remain an increasing function in a given direction of the two dimensional space. Why it is interesting to demodulate a single or a series of interferograms in which there is no spatial or temporal carrier ?, knowing that this is a substantially more difficult task ?. The answer is that although one always tries to obtain a single or a series of interferograms with spatial and/or temporal carrier , sometimes the very nature of the experimental set-up do not permit to obtain them. One reason could be that one is studying fast transient phenomena where there is no time to introduce a carrier. In these cases one still wants to demodulate the interferograms to evaluate quantitatively the physical variable under study.
In this paper, a set of polynomials are calculated to approximate the phase from a single closed fringe pattern image or interferogram. A scanning window is used to carry out the demodulation process. A polynomial function is fitted over the sub-image obtained from each scanning window. Then, the scanning window is moved on an overlapped neighbourhood of the previous one and the process is repeated. The coefficient polynomial optimization is achieved by multiple application of a genetic algorithm (GA). The GA optimizes a cost function which considers the irradiance similitude between original interferogram and fringes generated by the polynomial obtained from chromosome decodification, the smoothness of the phase being demodulated, and the phase similitude between the overlapped area of actual and previous scanning window. Closed fringe patterns with broad bandwidth can be demodulated. Preliminary results are presented.
In this paper, a new and useful technique is presented to recover the object surface shape that contains discontinuities and additionally a wrinkled texture. In conventional photometric and fringe projection methods it is difficult to recover discontinuities and wrinkled texture, simultaneously. For carrying out the proposed technique, it is necessary to have the projection of a cosenuidal ruling with low and high frequencies. The technique recovers the discontinuities by filtering out low frequency in the Fourier spectrum. On the other hand, the wrinkled texture is detected by using the high frequency of the ruling spectrum. Finally, we use a joining algorithm to get the global object shape.
The topic is wildly off-axis reflecting systems (Schiefspiegler) which consist of a pair of confocal prolate spheroids. That they are reflecting makes them appropriate for use in the infrared. By wildly off-axis I mean that the angle between the major axes of the two spheroids may be arbitrarily large, a property that makes them particularly useful in the cramped quarters on a satellite. In this construction two foci, one from each of the spheroids, are made to coincide. The remaining two, belonging to each spheroid, are taken as the systems entrance and exit pupils. Thus a chief ray will pass through each of these three points. In previous papers we have defined the pseudo axis as on e of the chief rays about which all other chief rays are symmetric and the conditions for its existence had been derived. Conditions for the formation of particular types of imaging forming systems, or for afocal systems, also have been derived. In this paper we present specific examples of these systems together with analyses of their properties as determined by generalized ray tracing.
A recently developed technique for fringe analysis based on a digital phase-locked loop is applied to detect the ray aberration of modulated Ronchi rulings. The Ronchi ruling is placed outside the caustic, and the shadow of the ruling is imaged directly into a two-dimensional CCD video array for further processing. The CCD array is placed at a distance of a few centimeters behind the Ronchi ruling; therefore, reasonably well-defined modulated fringes are obtained into the CCD sensor. Moreover, for small wave aberrations and coherent illumination, the first Talbot image of the ruling may be imaged over the CCD to increase the sensitivity of the test. By means of the experimental setup suggested herein, we obtain slightly modulated fringes. These fringes are demodulated using a highly sensitive digital phase-locked loop. Consequently, the transversal aberration along the direction perpendicular to the grating is found continuously across the entire image; that is, no unwrapping process is required, given that it is implicit within the phase-locked loop technique. Additionally, the same scheme with minor modifications may be used for null testing of aspheres.