Adaptive Disparity Research Articles

Regularized Stereo Matching Scheme using Adaptive Disparity Estimation

In this paper, a regularized stereo matching scheme using adaptive disparity estimation is proposed. That is, by adaptively predicting the mutual correlation between stereo image pair using the proposed algorithm, the bandwidth of an input stereo image pair can be compressed to the level of a conventional two-dimensional (2D) image and a predicted image can also be effectively reconstructed using a reference image and disparity vectors. In the adaptive disparity estimation method, feature values are extracted from an input stereo image pair and a matching window for stereo matching is adaptively selected depending on the magnitude of the feature values. Accordingly, this adaptive window matching algorithm (AMA) could improve the overall performance of stereo matching by reducing the mismatch of disparity vectors, which occurs in the conventional dense disparity estimation with a small matching window, and also by reducing a blocking effect, which occurs in the coarse disparity estimation with a large matching window. However, it still has problems of overlap and disallocation of matching windows. Therefore, to alleviate those problems, a new regularized adaptive disparity estimation method is proposed in this paper. That is, the estimated disparity vector is regularized with the neighboring disparity vectors; as a result, the predicted stereo image is found to be more effectively reconstructed. Some experiments with stereo sequences of “Man”, “Hoon”, “Yong”, and “Car” reveal that the proposed algorithm improves the peak signal-to-noise ratios (PSNRs) of the reconstructed images by 8.47 and 1.53 dB, on average, compared with those in the cases of feature and pixel-based window matching algorithm (FPMA) and AMA, respectively.

Rapid lineage accumulation in a non-adaptive radiation: phylogenetic analysis of diversification rates in eastern North American woodland salamanders (Plethodontidae: Plethodon).

Adaptive radiations have served as model systems for quantifying the build-up of species richness. Few studies have quantified the tempo of diversification in species-rich clades that contain negligible adaptive disparity, making the macroevolutionary consequences of different modes of evolutionary radiation difficult to assess. We use mitochondrial-DNA sequence data and recently developed phylogenetic methodologies to explore the tempo of diversification of eastern North American Plethodon, a species-rich clade of woodland salamanders exhibiting only limited phenotypic disparity. Lineage-through-time analysis reveals a high rate of lineage accumulation, 0.8 species per million years, occurring 11-8 million years ago in the P. glutinosus species group, followed by decreasing rates. This high rate of lineage accumulation is exceptional, comparable to the most rapid of adaptive radiations. In contrast to classic models of adaptive radiation where ecological niche divergence is linked to the origin of species, we propose that phylogenetic niche conservatism contributes to the rapid accumulation of P. glutinosus-group lineages by promoting vicariant isolation and multiplication of species across a spatially and temporally fluctuating environment. These closely related and ecologically similar lineages persist through long-periods of evolutionary time and form strong barriers to the geographic spread of their neighbours, producing a subsequent decline in lineage accumulation. Rapid diversification among lineages exhibiting long-term maintenance of their bioclimatic niche requirements is an under-appreciated phenomenon driving the build-up of species richness.

Effective reconstruction of stereoscopic image pair by using regularized adaptive window matching algorithm

In this paper, an effective method for reconstruction of stereoscopic image pair through the regularized adaptive disparity estimation is proposed. Although the conventional adaptive disparity window matching can sharply improve the PSNR of a reconstructed stereo image, but there still exist some problems of overlapping between the matching windows and disallocation of the matching windows, because the size of the matching window tend to changes adaptively in accordance with the magnitude of the feature values. In the proposed method, the problems relating to the conventional adaptive disparity estimation scheme can be solved and the predicted stereo image can be more effectively reconstructed by regularizing the extimated disparity vector with the neighboring disparity vectors. From the experimental results, it is found that the proposed algorithm show improvements the PSNR of the reconstructed right image by about 2.36 ∼ 2.76 dB, on average, compared with that of conventional algorithms.

New disparity estimation scheme based on adaptive matching windows for intermediate view reconstruction

A new intermediate view reconstruction technique based on the adaptive disparity estimation algorithm is proposed. First, the feature values indicating the local image complexity are extracted from the input stereo image pair by using edge detection and matching algorithms. Then, the matching window size for disparity estimation is adaptively selected depending on the magnitude of these feature values. That is, for the region having larger feature values, the smaller matching window size is selected, while for the opposite case, the larger matching window size is selected by comparison with a predetermined threshold value. This new approach is not only able to reduce the mismatch of the disparity vector, which occurs in conventional fine disparity estimation with a small matching window size, but also can reduce the blocking effect, which occurs in coarse disparity estimation with a large matching window size. Some experimental results show that the proposed algorithm improves the peak signal-to-noise of the reconstructed intermediate view up to 2.93 to 4.09 dB and reduces the execution time to 39.34 to 65.62% on average in comparison with those of conventional algorithms.

Adaptation to vertical disparity induced-depth: implications for disparity processing

Depth aftereffects produced by prolonged inspection of an object in depth can be mediated by monocular and binocular depth cues. The adapting mechanisms responsible for such effects have not yet been fully determined. Theories of binocular depth aftereffects typically posit a role of an adaptive horizontal disparity sensitive mechanism, implying multiple cue-specific mechanisms for depth aftereffects. Here we examined whether binocular depth aftereffects can be attributed to such a cue-specific mechanism. In Experiment 1 we did so using a technique allowing us to maintain horizontal disparities and vergence constant for our adaptation stimuli, whilst manipulating simulated depth by virtue of a vertical disparity induced-depth effect. We found that depth aftereffects were almost identical to those produced by adaptation to stimuli of equivalent depth produced by conventional horizontal disparity modulations. In Experiment 2, we examined depth aftereffects following adaptation to apparently frontal surfaces produced by different combinations of horizontal and vertical disparity modulations. Aftereffects were close to zero. These results suggest that binocular depth aftereffects are not due to adaptation of a horizontal disparity sensitive mechanism, and we argue that adaptation occurs at the level of a 3D shape sensitive mechanism derived from multiple cues. Experiment 3 was a control to examine whether the two types of adaptation stimuli in Experiment 1 were indeed perceptually the same, since in theory they may differ if vertical disparities influenced metric depth scaling. We found no evidence of this, and concluded that the two classes of stimuli used in Experiment 1, though consisting of very different patterns of disparity, were perceptually equivalent.

Testing the Hypothesis That a Clade Has Adaptively Radiated: Iguanid Lizard Clades as a Case Study

The study of adaptive radiations has played a fundamental role in understanding mechanisms of evolution. A recent resurgence in the study of adaptive radiations highlights a gap in our knowledge about determining whether a clade constitutes adaptive diversification. Specifically, no objective criteria exist to judge whether a clade constitutes an adaptive radiation. Most clades, given enough time, will diversify adaptively to some extent; therefore, we argue that the term "adaptive radiation" should be reserved for those clades that are exceptionally diverse in terms of the range of habitats occupied and attendant morphological adaptations. Making such a definition operational, however, requires a comparative analysis of many clades. Only by comparing clades can one distinguish those that are exceptionally diverse (or nondiverse) from those exhibiting a normal degree of adaptive disparity. We propose such a test, focusing on disparity in the ecological morphology of monophyletic groups within the lizard family Iguanidae. We find that two clades, the Polychrotinae and Phrynosomatinae, are exceptionally diverse and that two others, the Crotaphytinae and Oplurinae, are exceptionally nondiverse. Potential explanations for differences in diversity are discussed, as are caveats and future extensions of our approach.

Testing the Hypothesis That a Clade Has Adaptively Radiated: Iguanid Lizard Clades as a Case Study

The study of adaptive radiations has played a fundamental role in understanding mechanisms of evolution. A recent resurgence in the study of adaptive radiations highlights a gap in our knowledge about determining whether a clade constitutes adaptive diversification. Specifically, no objective criteria exist to judge whether a clade constitutes an adaptive radiation. Most clades, given enough time, will diversify adaptively to some extent; therefore, we argue that the term “adaptive radiation” should be reserved for those clades that are exceptionally diverse in terms of the range of habitats occupied and attendant morphological adaptations. Making such a definition operational, however, requires a comparative analysis of many clades. Only by comparing clades can one distinguish those that are exceptionally diverse (or nondiverse) from those exhibiting a normal degree of adaptive disparity. We propose such a test, focusing on disparity in the ecological morphology of monophyletic groups within the lizard family Iguanidae. We find that two clades, the Polychrotinae and Phrynosomatinae, are exceptionally diverse and that two others, the Crotaphytinae and Oplurinae, are exceptionally nondiverse. Potential explanations for differences in diversity are discussed, as are caveats and future extensions of our approach.

Disparity map coding based on adaptive triangular surface modelling

The paper proposes an adaptive disparity map modelling and coding method based on Delaunay triangulation. It provides an efficient and progressive format to represent disparity map information. Experiments showed that the method is promising and extendable. A hierarchical and adaptive disparity estimation algorithm which can obtain satisfactory disparity estimation results with less computational cost is also presented.

Reappraising adaptive radiation

Reappraising adaptive radiation

両眼立体視における適応的視差検出法

Binocular Vision has been considered to be a method of three dimensional measurement, and this leads to lack of discussing how to decide the size of region that apply physical restriction, the reliability of disparities. These missing issues are quite important for robots when they use it as a method of percepting depth information. In this paper, we propose an adaptive algorithm to compute reliable disparities fast. It is composed of two processes. One is the process that compute disparities with the uniform radius of the correlation window. It can compute disparities with high reliability by eliminating false disparities sequencially. Another is the process that compute disparities with the adaptive radius of the correlation window. Since this process automaticaly selects the minimum radius of the correlation window in which reliable disparities can be detected, fast computation of disparities is realizable. It is shown that the algorithm of Adaptive Disparity Detection is effective for various images.