Papers by Francisco Cuevas
Journal of The Optical Society of America A-optics Image Science and Vision, 2002
The fringe orientation angle provides useful information for many fringe-pattern-processing techn... more The fringe orientation angle provides useful information for many fringe-pattern-processing techniques. From a single normalized fringe pattern (background suppressed and modulation normalized), the fringe orientation angle can be obtained by computing the irradiance gradient and performing a further arctangent computation. Because of the 180 degrees ambiguity of the fringe direction, the orientation angle computed from the gradient of a single fringe pattern can be determined only modulo pi. Recently, several studies have shown that a reliable determination of the fringe orientation angle modulo 2pi is a key point for a robust demodulation of the phase from a single fringe pattern. We present an algorithm for the computation of the modulo 2pi fringe orientation angle by unwrapping the orientation angle obtained from the gradient computation with a regularized phase tracking method. Simulated as well as experimental results are presented.
Interferometry XII: Techniques and Analysis, 2004
ABSTRACT
Interferometry XII: Techniques and Analysis, 2004
ABSTRACT In this paper we are going to review two interferometric techniques to demodulate a sing... more ABSTRACT 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 [1]. 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 [2], 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.
Advances in Intelligent Systems and Computing, 2013
Lecture Notes in Computer Science, 2004
Abstract. In this paper we show how a binary memory can be used to recall gray-level patterns. Gi... more Abstract. In this paper we show how a binary memory can be used to recall gray-level patterns. Given a set of gray-level patterns to be first memorized: 1) Decompose each pattern into a set of binary patterns, and 2) Build a binary associative memory (one matrix for ...
Lecture Notes in Computer Science, 2004
A. Sanfeliu et al. (Eds.): CIARP 2004, LNCS 3287, pp. 187194, 2004. © Springer-Verlag Berlin Hei... more A. Sanfeliu et al. (Eds.): CIARP 2004, LNCS 3287, pp. 187194, 2004. © Springer-Verlag Berlin Heidelberg 2004 ... Extended Associative Memories for Recalling Gray Level Patterns ... Humberto Sossa1, Ricardo Barrón1, Francisco Cuevas2, Carlos Aguilar1, and Héctor Cortés1
Lecture Notes in Computer Science, 2014
Fifth Symposium Optics in Industry, 2006
Fifth Symposium Optics in Industry, 2006
Pattern Recognition Letters, 2003
A statistical approach based on the coordinated clusters representation of images is used for cla... more A statistical approach based on the coordinated clusters representation of images is used for classification and recognition of textured images. The ability of the descriptor to capture spatial statistical features of an image is exploited. A binarization needed for image preprocessing is done using, but not restricted to, a fuzzy clustering algorithm. A normalized spectrum histogram of the coordinated cluster
Pattern Recognition, 2014
A new chain code to represent 3D discrete curves is proposed. The method is based on a search for... more A new chain code to represent 3D discrete curves is proposed. The method is based on a search for relative changes in the 3D Euclidean space, composed of three main vectors: a reference vector, a support vector, and a change direction vector, utilized to obtain a directed simple path in a grid of 26 connected components. A set of rotation transformations is defined in the 3D Euclidean space, and despite encountering a complete set of 73 different basic pattern chains, an alphabet of only 25 symbols is required to represent any face, edge or vertex-connected discrete curve. Also, we used the code to represent trees, using parenthesis and a lexicographical order to be able to traverse each of their branches. Important properties of this code are found: independence under translation, rotation and mirror transformations, as well as high compression levels. Finally, a set of 3D curve-skeleton and digital elevation model data to study the terrain were utilized to prove the proposed code.
Journal of the Optical Society of America A, 2002
The fringe orientation angle provides useful information for many fringe-pattern-processing techn... more The fringe orientation angle provides useful information for many fringe-pattern-processing techniques. From a single normalized fringe pattern (background suppressed and modulation normalized), the fringe orientation angle can be obtained by computing the irradiance gradient and performing a further arctangent computation. Because of the 180 degrees ambiguity of the fringe direction, the orientation angle computed from the gradient of a single fringe pattern can be determined only modulo pi. Recently, several studies have shown that a reliable determination of the fringe orientation angle modulo 2pi is a key point for a robust demodulation of the phase from a single fringe pattern. We present an algorithm for the computation of the modulo 2pi fringe orientation angle by unwrapping the orientation angle obtained from the gradient computation with a regularized phase tracking method. Simulated as well as experimental results are presented.
Neural Processing Letters, 2005
In this note we show how a binary memory can be used to recall gray-level patterns. We take as ex... more In this note we show how a binary memory can be used to recall gray-level patterns. We take as example the αβ associative memories recently proposed in Yáñez, Associative Memories based on order Relations and Binary Operators(In Spanish), PhD Thesis, Center for computing Research, February of 2002, only useful in the binary case. Basically, the idea consists on that given a set of gray-level patterns to be first memorized: (1) Decompose them into their corresponding binary patterns, and (2) Build the corresponding binary associative memory (one memory for each binary layer) with each training pattern set (by layers). A given pattern or a distorted version of it, it is recalled in three steps: (1) Decomposition of the pattern by layers into its binary patterns, (2) Recalling of each one of its binary components, layer by layer also, and (3) Reconstruction of the pattern from the binary patterns already recalled in step 2. The proposed methodology operates at two phases: training and recalling. Conditions for perfect recall of a pattern either from the fundamental set or from a distorted version of one them are also given. Experiments where the efficiency of the proposal is tested are also given.
Applied Optics, 1998
We develop a regularized phase-tracking ͑RPT͒ technique to unwrap phase maps. The phase maps that... more We develop a regularized phase-tracking ͑RPT͒ technique to unwrap phase maps. The phase maps that can be unwrapped with this new method may be bounded by arbitrarily shaped boundaries. Moreover, the RPT unwrapper has a higher noise robustness than previously reported phase-unwrapping schemes.
Pattern Recognition Letters, 2003
A statistical approach based on the coordinated clusters representation of images is used for cla... more A statistical approach based on the coordinated clusters representation of images is used for classification and recognition of textured images. The ability of the descriptor to capture spatial statistical features of an image is exploited. A binarization needed for image preprocessing is done using, but not restricted to, a fuzzy clustering algorithm. A normalized spectrum histogram of the coordinated cluster representation is used as a unique feature vector, and a simple minimum distance classifier is used for classification purposes. Using the size and the number of subimages for prototype generation and the size of the test images as the parameters in the learning and recognition phases, we establish the regions of reliable classification in the space of subimage parameters. The results of classification tests show the high performance of the proposed method that may have industrial application for texture classification.
Applied Optics, 1999
Most interferogram demodulation techniques give the detected phase wrapped owing to the arctangen... more Most interferogram demodulation techniques give the detected phase wrapped owing to the arctangent function involved in the final step of the demodulation process. To obtain a continuous detected phase, an unwrapping process must be performed. Here we propose a phase-unwrapping technique based on a regularized phase-tracking ͑RPT͒ system. Phase unwrapping is achieved in two steps. First, we obtain two phase-shifted fringe patterns from the demodulated wrapped phase ͑the sine and the cosine͒, then demodulate them by using the RPT technique. In the RPT technique the unwrapping process is achieved simultaneously with the demodulation process so that the final goal of unwrapping is therefore achieved. The RPT method for unwrapping the phase is compared with the technique of least-squares integration of wrapped phase differences to outline the substantial noise robustness of the RPT technique.
Applied Optics, 1999
Most interferogram demodulation techniques give the detected phase wrapped owing to the arctangen... more Most interferogram demodulation techniques give the detected phase wrapped owing to the arctangent function involved in the final step of the demodulation process. To obtain a continuous detected phase, an unwrapping process must be performed. Here we propose a phase-unwrapping technique based on a regularized phase-tracking ͑RPT͒ system. Phase unwrapping is achieved in two steps. First, we obtain two phase-shifted fringe patterns from the demodulated wrapped phase ͑the sine and the cosine͒, then demodulate them by using the RPT technique. In the RPT technique the unwrapping process is achieved simultaneously with the demodulation process so that the final goal of unwrapping is therefore achieved. The RPT method for unwrapping the phase is compared with the technique of least-squares integration of wrapped phase differences to outline the substantial noise robustness of the RPT technique.
Applied Optics, 1998
We develop a regularized phase-tracking ͑RPT͒ technique to unwrap phase maps. The phase maps that... more We develop a regularized phase-tracking ͑RPT͒ technique to unwrap phase maps. The phase maps that can be unwrapped with this new method may be bounded by arbitrarily shaped boundaries. Moreover, the RPT unwrapper has a higher noise robustness than previously reported phase-unwrapping schemes.
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Papers by Francisco Cuevas