181,757 research outputs found
Optimum Gabor filter design and local binary patterns for texture segmentation
No full textWe present a novel approach to multi-texture image segmentation based on the formation of an effective texture feature vector. Texture sub-features are derived from the output of an optimized Gabor filter. The filter's parameters are selected by an immune genetic algorithm, which aims at maximizing the discrimination between the multi-textured regions. Next the texture features are integrated with a local binary pattern, to form an effective texture descriptor with low computational cost, which overcomes the weakness of the single frequency output component of the filter. Finally, a K-nearest neighbor classifier is used to effect the multi-texture segmentation. The integration of the optimum Gabor filter and local binary pattern methods provide a novel solution to the task. Experimental results demonstrate the effectiveness of the proposed approach
Gabor frames with trigonometric spline dual windows
No full textA Gabor system is a collection of modulated and translated copies of a window function. If we have a signal in , it can be analyzed with a Gabor system generated by a certain window and then synthesized with a Gabor system generated by another window . If this leads us to a perfect reconstruction, we say that and are dual Gabor windows.
Few explicit examples of dual window pairs are known. This thesis constructs explicit examples of Gabor dual windows with trigonometric form. The windows have fixed support and have an arbitrary smoothness.
Also, in the discrete time domain, the trigonometric form allows us to evaluate the Gabor coefficients efficiently using the Discrete Fourier Transform.
For the higher dimensional cases, we find window examples for a large class of modulation parameter lattices, including shear lattices. Also, a sufficient condition on the norm of the modulation lattice to have explicit dual Gabor windows is presented, for every dimension.Item withdrawn by Mark Zulauf ([email protected]) on 2011-07-01T20:21:55Z
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Swept source optical coherence tomography Gabor fusion splicing technique for microscopy of thick samples using a deformable mirror
No full textWe present a swept source optical coherence tomography (OCT) system at 1060 nm equipped with a wavefront sensor at 830 nm and a deformable mirror in a closed-loop adaptive optics (AO) system. Due to the AO correction, the confocal profile of the interface optics becomes narrower than the OCT axial range, restricting the part of the B-scan (cross section) with good contrast. By actuating on the deformable mirror, the depth of the focus is changed and the system is used to demonstrate Gabor filtering in order to produce B-scan OCT images with enhanced sensitivity throughout the axial range from a Drosophila larvae. The focus adjustment is achieved by manipulating the curvature of the deformable mirror between two user-defined limits. Particularities of controlling the focus for Gabor filtering using the deformable mirror are presented. © 2015 Society of Photo-Optical Instrumentation Engineers
Orbits of bounded bijective operators and Gabor frames
No full textThis paper is a contribution to frame theory. Frames in a Hilbert space are
generalizations of orthonormal bases. In particular, Gabor frames of
, which are made of translations and modulations of one or
more windows, are often used in applications. More precisely, the paper deals
with a question posed in the last years by Christensen and Hasannasab about the
existence of overcomplete Gabor frames, with some ordering over ,
which are orbits of bounded operators on . Two classes of
overcomplete Gabor frames which cannot be ordered over and
represented by orbits of operators in are given. Some
results about operator representation are stated in a general context for
arbitrary frames, covering also certain wavelet frames.Comment: 12 page
On R-Duals and the Duality Principle in Gabor Analysis
No full textThe concept of R-duals of a frame was introduced by Casazza, Kutyniok and Lammers in 2004, with the motivation to obtain a general version of the duality principle in Gabor analysis. For tight Gabor frames and Gabor Riesz bases the three authors were actually able to show that the duality principle is a special case of general results for R-duals. In this paper we introduce various alternative R-duals, with focus on what we call R-duals of type II and III. We show how they are related and provide characterizations of the R-duals of type II and III. In particular, we prove that for tight frames these classes coincide with the R-duals by Casazza et al., which is desirable in the sense that the motivating case of tight Gabor frames already is well covered by these R-duals. On the other hand, all the introduced types of R-duals generalize the duality principle for larger classes of Gabor frames than just the tight frames and the Riesz bases; in particular, the R-duals of type III cover the duality principle for all Gabor frames
Limitations for change detection in multiple Gabor targets
No full textWe investigate the limitations on the ability to detect when a target has changed, using Gabor targets as simple quantifiable stimuli. Using a partial report technique to equalise response variables, we show that the log of the Weber fraction for detecting a spatial frequency change is proportional to the log of the number of targets, with a set-size effect that is greater than that reported for visual search. This is not a simple perceptual limitation, because pre-cueing a single target out of four restores performance to the level found when only one target is present. It is argued that the primary limitation on performance is the division of attention across multiple targets, rather than decay within visual memory. However in a simplified change detection experiment without cueing, where only one target of the set changed, not only was the set size effect still larger, but it was greater at 2000 msec ISI than at 250 msec ISI, indicating a possible memory component. The steepness of the set size effects obtained suggests that even moderate complexity of a stimulus in terms of number of component objects can overload attentional processes, suggesting a possible low-level mechanism for change blindness
Characterizations of weak R-duality and its application to Gabor frames
No full textWeak R-duals, a generalization of R-duals, were recently introduced; for which duality relations were established. In this paper, we consider the problem of characterizing a given frame sequence to be a weak R-dual of a given frame. Further, we apply these characterization results to the Gabor frame setting and prove that the weak R-duality of the adjoint Gabor system leads to the R-duality of the same, thereby indicating an approach to answer the famous problem of the adjoint Gabor system being an R-dual of a given Gabor frame.27 Page
A fast learning algorithm for Gabor transformation
No full textAn adaptive learning approach for the computation of the coefficients of the generalized nonorthogonal 2-D Gabor transform representation is introduced in this correspondence. The algorithm uses a recursive least squares (RLS) type algorithm. The aim is to achieve minimum mean squared error for the reconstructed image from the set of the Gabor coefficients. The proposed RLS learning offers better accuracy and faster convergence behavior when compared with the least mean squares (LMS)-based algorithms. Applications of this scheme in image data reduction are also demonstrated
Automatic image processing using the Ateb-Gabor method
No full textThis article describes an image filtration using an Ateb-Gabor method. Proposed
method allows to expend a Gabor filter performance because it contains much more
combinations. There was an Ateb-Gabor filtration provided to the one case of
images and to the one periodic Ateb-function
Gabor orthonormal bases, tiling and periodicity
No full textWe show that if the Gabor system , is an orthonormal basis in and if the window function is compactly supported, then both the time shift set and the frequency shift set must be periodic. To prove this we establish a necessary functional tiling type condition for Gabor orthonormal bases which may be of independent interest.publishe
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