立体视觉中视差信息在视觉系统中的编码方式——位置差？相位差？

视差是形成双眼立体视觉的主要机制,由于双眼的水平分布,导致空间物体在双眼视网膜上的投影的位置产生视差,但是图象的视差怎样由皮以眼性细胞来进行编码？早期曾推测是由双眼性细胞左右感受野的位置差异来对应,并有一些心理物理和生理实验的证据。最近的一些研究表明,感受野的相位差是视差编码的主要方式,感受野位置差则在某种程度上是一种补充。     

用于立体视检测的微机软件包的设计

为了快速、方便、准确地检测人的立体视功能,根据双眼视差原理,设计了用于立体视检测的微机软件包称为立体视检测(SVT).利用该软件可在彩色屏幕(VGA)上产生静态等视差图(图中各部分的视差不随空间位置的变化而改变)、变视差图、以及在深度上的正弦波状起伏图形.叙述了设计原理和程序框图;报导了用SVT软件包对视力正常和异常儿童的立体视检测结果并讨论了其临床应用价值．     

视差检测：简单细胞、复杂细胞及能量模型

立体视觉信息的处理在于皮层双眼性细胞的活动.皮层中简单细胞对视差的编码方式被认为有两种：位置差（position shift）和相位差（phase shift）,但简单细胞并不适合作为视差检测器.对一些复杂细胞的视差响应特性的生理研究,发现复杂细胞是一种比较适合的视差检测器.模型的研究提出基于这类简单细胞的复杂细胞能量模型,可以很好的检测视差,并可以较好的解释一些生理现象.     

立体视锐度的测量

视差只在一定大小范围内才能产生体视感觉。对５名体视感觉正常者和一名体视感觉欠缺者做心理物理试验并记录视觉诱发电位（ＶＥＰ）。结论如下：（１）交叉视差产生体视感觉的视差下限阈值约为２５秒;非交叉视差产生体视感觉的视差下限阈值约为３５秒。（２）改变视差大小的方法不同对这个阈值有影响。视差由大到小改变比由小到大改变,这个视差下限阈值要小,两者差别约为１０秒至２０秒。（３）体视欠缺者产生体视感觉的视差下限阈值约为６０秒。（４）使用不同形式的立体图对这个阈值不同,对于随机点立体图对,产生体视感觉下限阈值约为６０秒。（５）当视差大于１２０秒时的ＶＥＰ呈现规律变化。（６）体视欠缺者的ＶＥＰ与正常者比较呈现较大的差别。     

半孔径立体显微镜

本文介绍一种半孔径立体显微摄影的插件,使能以一般光学显微镜观察细胞或组织结构的立体图象。一、半孔径立体显微摄影插件的结构及使用方法单眼观察物体时只知其大小而不能决定其空间位置,只有双眼才可以看出立体,因为双眼观察时具有视差。为了使在只有单眼视觉结构的普通光学显微镜上能实现双眼视觉的效应,我们设计了半孔径立体显微摄影插件,结     

两种视觉刺激状态VEP的源定位分析

有关诱发电位的源定位问题是近年来受到关注的脑研究前沿领域之一。我们采用了两种视觉刺激来对这个问题作了初步探讨。用棋盘格来对双眼的全视网膜以及上、下半视网膜进行刺激。并对这三种大面积皮层活动状态的诱发电位中最稳定的成分Ｐ１００进行了偶极子源定位分析。我们还对５＇和１０＇的交叉视差、非交叉视差的红绿随机点立体图诱发的ＶＥＰ中较稳定的成分Ｐ１００和Ｐ２００进行了偶极子源定位。作者认为大脑对于视差的加工是由人脑内的一个功能性网络来完成的。对于所用的源定位模型作了进一步的讨论     

频差在立体视觉信息加工中的作用 Ⅱ、频差“克服”视差

双眼立体视觉机制至今不很清楚,存在不少争论,研究它具有深远意义。我们的兴趣是从心理物理、电生理和理论模型三方面开展工作,最终目标是试图搞清楚视觉立体信息处理类机制。本文主要利用心理物理学方法研究频差克差视差的问题。我们利用自己研制的一种多功能立体图形发生器产生左边为非均匀条纹、右边为均匀条纹的一系列具有不同视差的立体图对。在感知到“阶梯”后,用三种方法使得“阶梯”感变平:①改变均匀条纹的频率,②改变均匀条纹与被试的距离,③改变非均匀条纹与被试者的距离。从而实现了频差“克服”视差。我们的结果支持用频差来解释双眼倾斜现象,它使我们相信频差是视差在初级视系统中的表象形式。     

频差在立体视觉信息加工中的作用 Ⅱ、频差“克服”视差

双眼立体视觉机制至今不很清楚,存在不少争论,研究它具有深远意义。我们的兴趣是从心理物理、电生理和理论模型三方面开展工作,最终目标是试图搞清楚视觉立体信息处理类机制。本文主要利用心理物理学方法研究频差克差视差的问题。我们利用自己研制的一种多功能立体图形发生器产生左边为非均匀条纹、右边为均匀条纹的一系列具有不同视差的立体图对。在感知到“阶梯”后,用三种方法使得“阶梯”感变平:①改变均匀条纹的频率,②改变均匀条纹与被试的距离,③改变非均匀条纹与被试者的距离。从而实现了频差“克服”视差。我们的结果支持用频差来解释双眼倾斜现象,它使我们相信频差是视差在初级视系统中的表象形式。     

看东西有立体感是怎么一回事?

答:所说的立体感就是立体视觉,是人对三维空间各种物体远近、前后、高低、深浅和凹凸的感知能力,是人在进化发展历程中获得的一项特有的双眼高级视觉功能。人在用双眼看同一物体时,这一物体的影象就分别落在了两眼的视网膜上,形成基本相同的两个影象。由于左右两眼有一定的距离,这样物体的每一点在两眼视网膜上的投影的对应点就不完全相同,而是有一个微小的位置差移,这个差移称为视差。当眼睛将视差传到大脑,经加工后,大脑就可把两眼传入的两个平面影象合成一个完整的立体影象,即立体视觉。     

三种广翅蜡蝉前翅形态数值特征提取与分析

【目的】广翅蜡蝉科昆虫是果园、茶园和园艺植物上的重要害虫之一,对其种类进行自动判别是实现其种群自动监测的基础。本研究拟通过获取3种广翅蜡蝉前翅轮廓特征探讨在其种类和性别鉴定中的作用。【方法】采用图像处理与分析技术,对3种广翅蜡蝉前翅轮廓形态特征进行提取和分析,并使用SPSS v22.0对数据进行分析。【结果】同一种广翅蜡蝉左右翅在轮廓形态上无显著差异,雌雄间各参数在不同种类广翅蜡蝉中差异性不同,其中5个实际测量参数在雌雄间差异达到显著或极显著水平,只有透明广翅蜡蝉的周长不显著。除周长和雄虫圆形度外,其它各类参数在种间的差异达到显著或极显著水平。通过典型判别分析,认为所选用的3种广翅蜡蝉,通过其前翅轮廓特征可以进行种间判别,其原始判别和交叉验证判别的正确率均超过90%。【结论】通过提取前翅轮廓特征可以实现3种广翅蜡蝉种类的识别,为此类昆虫的自动鉴定和种群监测提供了重要的参考依据。     

Brain damage and global stereopsis.

When a single object lies in front of or beyond the plane of fixation its retinal image lies on disparate positions in the two eyes. This 'local' retinal disparity is an excellent cue to depth, and retinal disparties of a few seconds of arc are detectable by people and monkeys. However, most visual scenes produce a complex array of contours in each eye and we can detect the disparity in the arrays despite the ambiguous nature of the disparities, i.e. each contour in one eye could be related to any of several similar contours in the other eye. This ability, known as 'global' stereopsis, may be selectively impaired following brain damage in man. Global stereopsis was measured in rhesus monkeys before and after removing a different cortical visual area in different groups of animals. Only removal of the inferotemporal cortex impaired global stereopsis. The result is related to the findings with human patients and to receptive field properties of neurons in the inferotemporal cortex of monkeys.     

Simulation of the effect of local adaption with nonlinear spatial filters

The visual system of vertebrates is capable of processing pattern signals over a wide range of intensity reaching from nearly absolute darkness to very bright sunlight. Typically the visual system of humans extracts fine contours of patterns of sufficiently high intensity or at high background intensity level, showing signal processing properties which can be explained by a bandpass system. Conversely, at very low intensity levels that system shows low-pass response: only coarse contours of patterns are recognized, however, the amplification of the signals has increased. The effect is called local adaption. A model is shown on the basis of a one-stage nonlinear spatial filter which, controlled by the local distribution of pattern intensity, can alter its frequency characteristic between low-pass response and bandpass response. Results are stated for computer-modelled filters. The investigation is restricted to one-dimensional filters, however, the results can be used to explain the function of two-dimensional filters qualitatively.     

The role of vergence in the perception of distance: a fair test of Bishop Berkeley's claim

Binocular eye movements were measured while subjects perceived the wallpaper illusion in order to test the claim made by Bishop Berkeley in 1709 that we perceive the distance of nearby objects by evaluating the vergence angles of our eyes. Four subjects looked through a nearby fronto-parallel array of vertical rods (28-35 cm away) as they binocularly fixated a point about 1 meter away. The wallpaper illusion was perceived under these conditions, i.e. the rods appeared farther away than their physical location. We found that although binocular fixation at an appropriate distance was needed to begin perceiving the wallpaper illusion (at least for naive observers), once established, the illusion was quite robust in the sense that it was not affected by changing vergence. No connection between the apparent localization of the rods and vergence was observed. We conclude that it is unlikely that vergence, itself, is responsible for the perceived distance shift in the wallpaper illusion, making it unlikely that vergence contributes to the perception of distance as Bishop Berkeley suggested. We found this to be true even when vergence angles were relatively large (more than 2 deg), the region in which the control of vergence eye movements has been shown to be both fast and effective.     

Methods of analysis of neural nets

The properties of isotropy, smoothness, minimum curvature and locality suggest the shape of filled-in contours between two boundary edges. The contours are composed of the arcs of two circles tangent to the given edges, meeting smoothly, and minimizing the total curvature. It is shown that shapes meeting all the above requirement can be generated by a network which performs simple, local computations. It is suggested that the filling-in process plays an important role in the early processing of visual information.     

桃小食心虫卵收集方法的改进

本文介绍了一种用绒面壁纸作为卵卡收集桃小食心虫Carposina sasakii Matsumura卵的方法。利用显微镜测试了绒面的绒毛高度和密度,并从落卵量和卵的孵化率两方面对这种卵卡和传统的滤纸卵卡进行了比较。结果表明,滤纸卵卡和绒面卵卡上的总落卵量无显著差异,平均为(303.77±51.03)粒和(330.23±44.85)粒,其中成虫交尾后48 h内的落卵量平均为(303.77±51.03)粒和(330.23±44.85)粒,其中成虫交尾后48 h内的落卵量为(176.31±38.96)粒和(223.92±30.69)粒(P<0.001)。成虫交尾后48 h内产下的卵平均孵化率为93.97%和94.56%,48 h后产下的卵平均孵化率为83.87%和83.58%,即成虫交尾后48 h后产下的卵的孵化率显著低于交尾后48 h内产下的卵(P<0.001),但同期落于两种卵卡上的卵孵化率差异不大。因此,使用绒面卵卡能显著提高初孵幼虫的数量,在得到相同虫量的情况下,显著降低成本。且相对于人工刮制的传统卵卡,使用绒面卵卡,很好的避免了因手工制作导致的一致性差、耗时长、人工费昂贵的问题,为收集桃小食心虫卵提供了一种较为理想的方法。     

Muscle Plasticity During Sprouting and Reinnervation

SYNOPSIS. When peripheral nerves are cut, the axotomized nervesand denervated muscles undergo atrophic changes which are reversedonly when functional connections are remade in the periphery.The restored interaction completely reverses the effects ofaxotomy and denervation and leads to rematching of the sizeof the motoneuron, muscle unit force, speed and histochemicalproperties, according to the size principle. Differences inunit force and fatigue characteristics between motor unit typesare not fully restored in reinnervated muscles but do not obscuresize relationships between the motoneurons and their muscleunits. Although intact motoneurons will supply increased numbers ofmuscle fibers after partial nerve injuries, regenerating axonsappear to be limited in their ability to enlarge their muscleunits. Increased motor unit force in reinnervated slow motorunits is accounted for primarily by an increase in fiber diameter;fast motor units do not increase their mean force output. As a result of the rematching of muscle unit properties withthe size of the motoneurons that reinnervate them, motor unitproperties are appropriate for fine control of movement aftercomplete or partial nerve injuries. However, regenerating axonsdo not reinnervate their original muscle fibers and unless thefibers are injured close to the muscles, they often fail toreinnervate their original muscles. The mismatching of motorpools with inappropriate target muscles is probably the mainfactor responsible for poor recovery of motor function aftercomplete nerve injuries.     

Non-Bayesian contour synthesis

Recent research has witnessed an explosive increase in models that treat percepts as optimal probabilistic inference. The ubiquity of partial camouflage and occlusion in natural scenes, and the demonstrated capacity of the visual system to synthesize coherent contours and surfaces from fragmented image data, has inspired numerous attempts to model visual interpolation processes as rational inference. Here, we report striking new forms of visual interpolation that generate highly improbable percepts. We present motion displays depicting simple occlusion sequences that elicit vivid percepts of illusory contours (ICs) in displays for which they play no necessary explanatory role. These ICs define a second, redundant occluding surface, even though all of the image data can be fully explained by an occluding surface that is clearly visible. The formation of ICs in these images therefore entails an extraordinarily improbable co-occurrence of two occluding surfaces that arise from the same local occlusion events. The perceived strength of the ICs depends on simple low-level image properties, which suggests that they emerge as the outputs of mechanisms that automatically synthesize contours from the pattern of occlusion and disocclusion of local contour segments. These percepts challenge attempts to model visual interpolation as a form of rational inference and suggest the need to consider a broader space of computational problems and/or implementation level constraints to understand their genesis.     

The effect of contour closure on shape perception

We studied psychophysically whether 'contour closure' enhances the accuracy of shape perception. Stimulus configurations (presented on a blank background) always consisted of identical pattern elements, but the positions of the local elements were varied: the global contour shape either contained closure or not. In the first two stimulus conditions (Closure), the oriented pattern elements (Gabor patches) formed a 'closed' rectangular shape composed of either four long lines or four corners. In the third condition (No closure), the global shape was composed of the four corners, but they were outward oriented, and hence they did not form the outline of a closed contour. We measured the precision of shape perception using a discrimination task in which observers judged the aspect ratio of the outline shape i.e. whether the rectangular shape was tall or wide. We found that: (i) shape discrimination was better (more precise) for Closed contours than for Non-closed contours, i.e. the aspect ratio discrimination thresholds were lower for the Closed than Non-closed configurations. The improved performance could not be explained by differences in visibility of the local elements in the two conditions. (ii) For closed contours, shape discrimination was more precise when the local elements were aligned with the global shape, than when the local elements were orthogonal to it.     

A hierarchical polar coordinate model for epimorphic regeneration

In the framework of polar coordinates three rules are postulated which can describe epimorphic regeneration in amphibian limbs. The rules can be seen as an extension of the polar coordinate model. When cells with different positional values are confronted, cell proliferation at the junction restores the continuity of positional values. Reestablishment of continuity is associated with the eventual congruence of the intercalating cell sequence with the host or graft, or both. The intercalating contours can be simple or twisted. The possible contours are graded within a plausible hierarchical scheme where congruent paths are favored versus non-congruent paths and simple contours are favored versus twisted contours. The model correctly predicts the multiplicity, position and different structures of supernumerary outgrowths resulting from both contralateral graftings and 180 degrees ipsilateral limb rotations. Development and regeneration of mirror-symmetric limbs are also accounted for. Several other experimental results are in agreement with the model. Many model predictions and correlations still remain to be tested.