基于双目立体视觉测距的浮选槽液位检测系统

提出一种基于双目立体视觉测距的浮选槽液位检测系统;采用两台工业摄像机采集图像,通过多种图像处理技术实现液面上的特征点匹配,再利用矩阵变换知识求出世界坐标系与摄像机坐标系的相对变换。实验结果表明该系统能有效控制液面测量偏差于±5 mm之内,达到了浮选槽液位检测的目的,有效提高了钾盐浮选过程的自动化水平。     

On the binocular summation of chromatic contrast

The binocular summation of chromatic contrast was investigated under a variety of stimulus conditions. Binocular and monocular contrast detection thresholds were measured using 0.5 cpd Gabor patches. It was found that, using stimuli which contained combinations of chromatic and luminance contrast, binocular detection could take place independently in luminance-contrast- and chromatic-contrast-sensitive mechanisms. It was also found that, with chromatic stimuli, levels of binocular summation were above those expected from probability summation between the eyes, and thus showed evidence for binocular neural summation within chromatic detection mechanisms. The implications of these results for (a) the binocularity of chromatic detection mechanisms, and (b) the suggested link between stereopsis and binocular neural summation, are discussed.     

Asymmetrical vertical phorias indicating dissociated vertical deviation in subjects with normal binocular vision

We measured the symmetry of phoria angles in six normal subjects. Subjects were selected on the basis of good visual acuity and stereopsis, normal binocular eye alignment and, apart from mild refraction errors, absence of ocular abnormalities. They were instructed to look at a word on a reading chart at 2 m distance. Each measurement consisted of five subsequent intervals of 5 s duration. During these five intervals viewing was binocular, with the right eye only, binocular, with the left eye only, and binocular, respectively. Each experiment consisted of twelve measurements. Eye movements were measured with scleral coils suited for measuring in horizontal, vertical and torsional directions. Five out of six subjects displayed an asymmetrical vertical phoria; one subject showed an alternating hyperphoria; four displayed a left over right vertical phoria that was largest for left eye occlusion. Only one subject showed a symmetrical vertical phoria. Both the size of the vertical phorias and the size of the asymmetries in these vertical phorias were very small: on average 0.16 +/- 0.01 and 0.17 +/- 0.01 degree, respectively. The direction of the vertical phoria asymmetries (the largest left over right was found with left eye occlusion) and the fact that asymmetries were found more often in vertical than horizontal and torsional phorias suggest that these asymmetries are related to dissociated vertical deviation. These results suggest that dissociated vertical deviation, often observed in subjects with a disruption of binocular vision early in life, reflects the enhancement of a phenomenon that is present in normal subjects as well.     

Contrast vision and contrast sensitivity after binocular implantation of multifocal or monofocal intraocular lenses

BACKGROUND: Multifocal intraocular lenses show a reduction of contrast due to the simultaneous projection of different images to the retina. In this study we examined if there is also a loss of contrast in bilateral implantation of multifocal lenses. MATERIAL AND METHODS: We examined 22 patients with bilateral AMO ARRAY multifocal intraocular lens and compared these to 20 patients with bilateral monofocal intraocular lens. We performed a monocular and binocular examination of contrast acuify by means of Regan's contrast charts and contrast sensitivity by means of B-VAT-II-SG-Video-acuity-tester. RESULTS: Monocular examination of contrast acuity showed significant superiority of the monofocal intraocular lens at the lowest contrast. Bilateral examination of contrast acuity did not show any significant difference. Monocular contrast sensitivity of the monofocal intraocular lens was significantly superior to the multifocal intraocular lens at two spatial frequencies, but under the bilateral condition there was only a significant difference between the two lenses at the highest spatial frequency. CONCLUSIONS: Bilateral implantation of multifocal intraocular lenses enables contrast acuity and contrast sensitivity that comes very close to the performance of the monofocal intraocular lenses.     

HALcon软件在宝钢连铸机浇铸机器人中的应用

机器人作为智能制造最具代表性的装备,在宝钢连铸机上已经实施。连铸机浇铸机器人在进行大包滑动水口油缸安装、大包介质管线连接和大包长水口更换等作业时,工件和机器人相对位置姿态会发生改变,而双目视觉定位系统可以引导机器人重新定位。介绍了双目视觉定位系统的基本原理,以及如何利用HALcon机器视觉软件开发宝钢连铸机浇铸机器人双目视觉定位系统。实践表明,双目视觉定位系统可有效计算出大包坐包和回转过程中的偏移,实现机器人精确定位。     

Reversible modification of the Goldmann perimeter for the assessment of the field of binocular single vision

Sixty eight Neisseria gonorrhoeae strains were isolated from endocervical and urethral discharge of 233 patients attending health centres for sexually transmitted diseases (STDs) in Addis Ababa, were identified following conventional procedures and tested for susceptibility to penicillin, ampicillin, trimethoprim-sulphamethoxazole (bactrim), chloramphenicol, erythromycin and kanamycin by the agar disc diffusion technique. Penicillinase producing N. gonorrhoeae (PPNG) were identified using the chromogenic cephalosporin method and comprised 70% of the isolates. Seventy seven per cent, 73%, 64% and 17% of the isolates were found to be resistant to penicillin, ampicillin, bactrim and kanamycin, respectively. However, no resistance to erythromycin and chloramphenicol was observed. Multiple drug resistance was found to be 67%. This is a cause for concern in the control and treatment of gonococci.     

On the geometry of fatigue crack closure

Long fatigue cracks frequently grow at a much lower rate than short cracks because they are closed during part of the stress cycle. The critical crack length for the transition from “short” to “long” depends on the amplitude of stress intensity ΔK and on the stress ratio R. This dependence is explained using a numerical study of the crack flank contour.     

Physiological computation of binocular disparity

We previously proposed a physiologically realistic model for stereo vision based on the quantitative binocular receptive field profiles mapped by Freeman and coworkers. Here we present several new results about the model that shed light on the physiological processes involved in disparity computation. First, we show that our model can be extended to a much more general class of receptive field profiles than the commonly used Gabor functions. Second, we demonstrate that there is, however, an advantage of using the Gabor filters: similar to our perception, the stereo algorithm with the Gabor filters has a small bias towards zero disparity. Third, we prove that the complex cells as described by Freeman et al. compute disparity by effectively summing up two related cross products between the band-pass filtered left and right retinal image patches. This operation is related to cross-correlation but it overcomes some major problems with the standard correlator. Fourth, we demonstrate that as few as two complex cells at each spatial location are sufficient for a reasonable estimation of binocular disparity. Fifth, we find that our model can be significantly improved by considering the fact that complex cell receptive field are, on average, larger than those of simple cells. This fact is incorporated into the model by averaging over several quadrature pairs of simple cells with nearby and overlapping receptive fields to construct a model complex cell. The disparity tuning curve of the resulting complex cell is much more reliable than the constructed from a single quadrature pair of simple cells used previously, and the computed disparity maps for random dot stereograms with the new algorithm are very similar to human perception, with sharp transitions at disparity boundaries. Finally, we show that under most circumstances our algorithm works equally well with either of the two well-known receptive field models in the literature.     

On vision, values, and cushy management.

Contends that the August 1996 archival issue of the American Psychologist , which focuses on the state of APA's management and governance, sends mixed, incomplete, and disturbing messages about that state. Horai asserts that the 1995 annual report of Chief Executive Officer R. D. Fowler (see record 83-38233) does not provide a sense of what happened during the year related to where APA is, where it is going, and what challenges and opportunities are ahead. She also contends that APA's management team is unresponsive to membership and indifferent toward the Council of Representatives and its work. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Is binocular correspondence and disparity still a dominant factor in binocular depth perception?

Laws of binocular correspondence and disparity are regarded as bases for explanation of most of the phenomena of binocular depth perception in the near field of vision. Abnormal phenomena such as differences in astigmatism of the 2 eyes, differences in acuity, cases of natural aniseikonia, investigated by the author, confirm the validity of the laws of correspondence and disparity and also of the law of intersection of visual directional lines. The inadequacies of other theories of binocular depth perception are pointed out and the author concludes that they cannot supplant the laws of binocular correspondence and disparity for the great majority of cases of binocular perception of depth in the near field of vision. (46 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A hierarchical model of binocular rivalry

Binocular rivalry is the alternating percept that can result when the two eyes see different scenes. Recent psychophysical evidence supports the notion that some aspects of binocular rivalry bear functional similarities to other bistable percepts. We build a model based on the hypothesis (Logothetis & Schall, 1989; Leopold & Logothetis, 1996; Logothetis, Leopold & Sheinberg, 1996) that alternation can be generated by competition between top-down cortical explanations for the inputs, rather than by direct competition between the inputs. Recent neurophysiological evidence shows that some binocular neurons are modulated with the changing percept; others are not, even if they are selective between the stimuli presented to the eyes. We extend our model to a hierarchy to address these effects.     

Visual-motor optimization in binocular control

When we view objects at various depths, the 3-D rotations of our two eyes are neurally yoked in accordance with a recently discovered geometric rule, here called the binocular extension of Listing's law; or L2. This paper examines the visual and motor consequences of this rule. Although L2 is a generalization of Listing's original, monocular law, it does not follow from current theories of the latter's function, which involve minimizing muscle work or optimizing certain aspects of retinal image flow. This study shows that a new optimization strategy that combines stereo vision with motor efficiency does explain L2, and describes the predictions of this new theory. Contrary to recent suggestions in the literature, L2 does not ensure vision of lines orthogonal to the visual plane, but rather reduces cyclodisparity of the visual plane itself; and L2 does not arise because a single, conjugate angular velocity command is sent to both eyes, but actually requires that the two eyes rotate with different speeds and axes when scanning an isovergence surface. This study shows that L2 is compatible with a 1-D control system for vergence alone (because horizontal and torsional vergence are yoked) and a 3-D system for combined, head-fixed saccades and vergence.     

Stereopsis and binocular rivalry.

Proposes that (1) rivalry and stereopsis involve independent and parallel pathways through the early stages of visual processing, (2) rivalry occurs when visual stimuli are present, and (3) binocular perception is a simple combination (probably a weighted average) of the output of the pathways mediating stereopsis and rivalry. Evidence from previous research and from 2 experiments, involving a total of 12 Ss, indicates that (a) the pathways mediating stereopsis are separable from those mediating rivalry; (b) stereopsis and rivalry can coexist at the same point in space and time; (c) rivalry occurs inevitably, whenever visual stimuli are present, even if identical stimuli are presented to both eyes; and (d) stereopsis can be disrupted without disrupting rivalry and vice versa (termed double dissociation). It is concluded that the human visual system has evolved with 2 parallel pathways that between them extract the needed information from the input; binocular single vision arises from the outputs of these 2 pathways. (84 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial interactions in binocular rivalry.

Observers tracked binocular rivalry between a pair of small, foveally viewed gratings whose orientation differed between the 2 eyes. In Exp 1, a textured annulus surrounding 1 eye's grating increased the total duration of exclusive visibility of the grating only when the grating-annulus separation was less than 0.5°. In Exp 2, observers tracked the visibility of a monocular annulus that surrounded a foveally viewed grating that was either engaged in rivalry or fused with a grating alone viewed by the other eye. The visibility of the annulus was greater when the grating it surrounded was not undergoing rivalry fluctuations. In Exp 3, the predominance of a rival grating was greater when the contours in the surrounding annulus were orthogonal to those of the rival grating. In Exp 4, total exclusive visibility of a given grating-annulus target was greater when the grating and the annulus contained the same orientation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A neural theory of binocular rivalry.

When the two eyes view discrepant monocular stimuli, stable single vision gives way to alternating periods of monocular dominance; this is the well-known but little understood phenomenon of binocular rivalry. This article develops a neural theory of binocular rivalry that treats the phenomenon as the default outcome when binocular correspondence cannot be established. The theory posits the existence of monocular and binocular neurons arrayed within a functional processing module, with monocular neurons playing a crucial role in signaling the stimulus conditions instigating rivalry and generating inhibitory signals to implement suppression. Suppression is conceived as a local process happening in parallel over the entire cortical representation of the binocular visual field. The strength of inhibition causing suppression is related to the size of the pool of monocular neurons innervated by the suppressed eye, and the duration of a suppression phase is attributed to the strength of excitation generated by the suppressed stimulus. The theory is compared with three other contemporary theories of binocular rivalry. The article closes with a discussion of some of the unresolved problems related to the theory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fine-scale processing in human binocular stereopsis

Many studies have demonstrated that the human visual system is sensitive to very small differences in relative binocular disparity. It is not known over what monocular regions information is spatially integrated to mediate performance in such tasks. In this study we present psychophysical observations that define the smallest spatial scale involved in disparity processing, and we indicate the nature of the computations performed by the units mediating that disparity discrimination. We show that human observers can identify the sign of disparity of a single target dot when it is embedded in a row of identical dots, with these noise dots presented either in the fixation plane or with a proportion binocularly uncorrelated. In conjunction with the psychophysical data, we explore how a class of simple correlator models of stereopsis must be constrained in order to account for human performance for the same fine-scale tasks. Such models can perform the task only when the correlation is carried out over a very small region of the image, for a very small range of disparities. Our results demonstrate that there is a fine-scale input to the stereo system, mediated by foveal mechanisms that spatially integrate visual signals over a region as small as 4-6 arcmin in diameter.