有单眼线索与无单眼线索的深度信息处理方式

一般认为体视(相对深度知觉)主要是双眼的视觉功能,是由双眼视差产生的。根据刺激图像的性质,体视大体上可以分成两类:一类是有单眼线索的,另一类则无单眼线索。所谓单眼线索,可以是Helmholtz的轮廓图形Kaufman的亮度模式,也可以是Ramachandran的主观轮廓。在立体图对中,所有这些图形或模式一律可用单眼加以识别。而无单眼线索的立体图对——例如Julesz的随机点立体图对——则不含任何可供单眼识别的图形或模式。     

立体图对的尺寸变化对立体感可塑性的影响

为了解随机点立体图对(Random-Dot Stereogram简称RDS)空间参数的变化是否影响整体立体感的可塑性(Plasticity of global stereopsis),我们利用微机化的伪随机点立体图对发生器设计了三个心理物理实验.第一个实验,使RDS图对中两幅图中的一幅,在水平和垂直两个方向上改变尺寸,第二个实验,仅改变在水平方向的尺寸,第三个实验,只改变在垂直方向上的尺寸.立体视觉正常的十名被试在立体镜下观察这些图形,当达到双眼融合时,观测RDS图对左右两图之间尺寸差别的限度,结果表明,当在水平方向上尺寸变化时,尺寸差别的限度为最大,在垂直方向上尺寸变化时.尺寸差别的限度次于前者,当在水平和垂直双向变化尺寸时,尺寸差别的限度为最小,对不同视角的RDS图对,达到双眼融合时,视角本身的大小对尺寸差别的限度无显著性(?)(?).     

双眼立体视觉的信息加工

一、随机点的立体图对动物和人生活在三维空间中,由于生存上的需要——觅食和躲避敌害——必须具有深度知觉,这也是在生活环境中长期适应的结果。但是动物和人又是通过什么去感觉出三维空间的景物的呢?我们知道眼睛的网膜是可以感受光强的,但是眼睛网膜所感受到的光强是外界景物的三维投影,至于深度这方面的信息     

立体图对匹配基元的心理物理学实验的探讨

Marr和Poggio等人从视觉信息加工理论中提出零交叉(Zero-Crossing)是视觉早期加工过程中首先得到的最基本的信息。这在生理上有二个高斯分布叠加的感受野以及侧抑现象等可以作为依据,但在心理物理上仍缺乏佐证。我们利用不同密度的随机点,加上了不同百分比的反差噪声的立体图对,观察了各种条件下体视对噪声的耐受特性,得出了有利于说明黑白相间的边(零交叉)为匹配基元的结果。本文报导了这些实验结果并进行了讨论。     

生物组织显微结构三维重建的灰度阴影立体图对显示技术

本文描述了一种新的显示三维重建模型的方法—灰度阴影立体图对方法(shading-stereo-pair method).该方法根据连续切片三维重建的灰度阴影法和立体图对法的显示原理,导出了生成立体图对的视差公式.在灰度阴影法三维重建过程中,根据各切片所处的深度和其本身的厚度,按视差公式计算出它们在图对上的位移量并进行水平方向的移动,经过对各切片的叠加和重组,最后生成一幅具有视差信息的灰度阴影立体图对.在体视仪下观察,即可看到重建模型的三维实体图象.最后还讨论了进一步提高图象质量和改善观察效果所必须采取的措施.     

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。     

不同空间频率通道的深度知觉及其质地的影响

我们设计了四种不同质地的随机点立体图对(RDS),并按照Wilson的空间频率通道的频带,分别利用Butterworth滤波器及Gabor函数对之进行了数字滤波处理,然后进行各种左右眼配对观察.得结果如下:1、Gabor函数滤波后图对的匹配结果好于Butterworth滤波器滤波后的图对.2、滤波后图对的匹配效果与图象质地有关.3、不同滤波的图对匹配大多也能形成立体感.4、在体视不同通道图对的匹配中,右眼对图象的高频成分更为敏感.     

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     

空间频率通道中噪声对体视匹配的影响

本工作希望了解噪声在各空间频率通道中对体视的影响.产生从5%至35%每隔5%的七个等级的随机点噪声图象,参照Wilson四通道模型的频率分别用两种不同滤波器对随机点立体图对(RDS)及噪声图象进行滤波,然后在各通道图对中加入不同通道噪声进行匹配观察.得到:1.高频通道的体视抗干扰能力高于低频通道.2.Gabor函数滤波后图对的体视抗干扰能力高于Butterworth滤波器滤波后的,但均低于未滤波的.3.当噪声大于15%时,低频噪声对低频图对及高频噪声对高、低频图对的体视匹配有抑制作用,而低频噪声对高频图对则影响很小.4.未滤波及各通道图对的最大噪声容限均不超过25%.     

交替呈现随机点立体图对的时间特性

利用微机化的伪随机点立体图对发生器进行双眼体视的心理物理实验,研究交替呈现的随机点体图对(RDS)在达到双眼融合形成立体感知时信息输入的时间特性.实验结果表明,当RDS的交变频率达到4.8Hz以上时就能达到双眼的信息融合产生立体感知,但当交变频率低于62.5Hz时有图形的闪烁感.当交变频率等于62.5Hz时则产生稳定而清晰的立体感知.一幅RDS图对中的L(左)和R(右)图的呈现时间及其之间的交变时间的长短均对双眼的融合和立体感的形成有影响.L和R图的呈现时间和交变时间还存在一定的关系,以立体感形成为条件,如增大一定值的L和R图的呈现时间,则它们之间的交变时间必须相应减小,反之亦然.实验结果提示,双眼立体感知的形成不涉及单眼图象的长时记忆和短时记忆,仅有瞬时的视觉存储.     

Stereopsis measured by random-dot patterns--a new clinical test.

Comparative measures are presented of stereo-acuity by random-dot stereograms using a phase difference haploscope and a Titmus stereogram. Using two groups of fifteen subjects each, one with full binocular vision and the other of small-angle strabismic amblyopes, greater discrimination between subject groups was found with the random-dot stereograms. It is concluded that random-dot stereograms produced by crossed Polaroid would be a more effective clinical means of determining stereo-acuity.     

Vertical disparity nulling in random-dot stereograms

Vertical alignment of monocularly visible structures has profound influence on a binocular system's ability to fuse high spatial frequencies of a random-dot stereogram. We show that monocular objects capture the vertical alignment: often less than 5% of the total stereogram area determines the state of the vertical alignment and can prevent fusion of the fine scale detail. This suggests that the human binocular system uses a heuristic in which, when monocularly salient information is available, stereomatching is attempted only at vertical alignment settings determined by the monocular structures.     

双眼频差平行加工深度的模拟

我们过去的计算分析工作和心理物理实验证明双眼频差率和视差成正比,再根据目前已知的神经生理学研究结果,提出了一个从频差平行加工深度的方案.并在计算机上对三个不同倾斜锥线的立体图对进行了重建深度的模拟.结果满意.对这种平行加工的优点进行了讨论.     

Wolf-Hirschhorn (4P-) syndrome in adults

Wolf-Hirschhorn syndrome (WHS) or 4p-deletion syndrome has been extensively described in children. Knowledge on adult WHS patients is still limited due to the small number of published cases. We present 4 adults and review the literature. The phenotype of adult WHS is in general similar to that of childhood WHS. Growth retardation, microcephaly and mental retardation are the rule in both adults and children. Facial dysmorphism also remains similar. The main difference lies in the absence of serious internal (cardiac) abnormalities in adult WHS. Mental retardation ranges from moderate to severe. The nosological overlap between WHS and Pitt-Rogers-Danks syndrome (PRDS) is discussed. More extensive data on adult WHS are needed for appropriate counselling of families with affected young children.     

Stages in the construction of stereograms of molecular models

In this article an analysis is performed of the results of stereogram construction using computer programs that model chemical compounds. Considerations about how best to represent models of molecules and improve legibility of stereograms are presented. An original diagrammatic substitute for the picture of a sphere, suitable for application in stereoscopic models of molecules, is proposed.     

Interaction between pools of binocular disparity detectors tuned to different disparities

Unambiguous dots (having one binocular disparity) when inserted in an ambiguous random-dot stereogram (with multiple disparity values) could pull the ambiguous percept. The unambiguous bias carried that ambiguous depth percept whose disparity was nearest to the disparity of the bias. The closer the disparities were to each other, the stronger the pulling effect that was observed. Even a physical bias of 4% density was adequate to overcome the natural bias of most observers. The stimulus duration had to be over 50 msec to provide a strong pulling effect. In all experiments the stimulus duration was 160 msec or shorter, indicating that the pulling effect was a product of neural interactions, rather than convergence movement of the eyes. As a result of these findings a parallel model of stereopsis has been proposed, which extends the spring-coupled dipole model of Julesz (1971).     

Spatial frequency tuned channels: implications for structure and function from psychophysical and computational studies of stereopsis

Various psychophysical experiments investigating the role of spatial frequency tuned channels in stereopsis are reviewed and a computational model of stereopsis deriving from these studies is described. The distinctive features of the model are: (1) it identifies edge locations in each monocular field by searching for zero crossings in non-orientated centre-surround convolution profiles; (2) it selects among all possible binocular point-for-point combinations of edge locations only those which satisfy a (quasi-) collinear figural grouping rule; (3) it presents a concept of the orientated and spatial frequency tuned channel as a nonlinear grouping operator. The success of the model is demonstrated both on a stereo pair of a natural scene and on a random-dot stereogram.     

Does vertical disparity scale the perception of stereoscopic depth?

It has been suggested that a measure of the gradients of vertical disparity over a surface may scale the mapping between horizontal disparity and perceived depth. We have investigated this possibility by obtaining estimates of the depth within stereograms that simulated two apposed fronto-parallel planes placed at different distances from an observer. The gradients of vertical disparity in a stereogram were set to simulate those appropriate to a viewing distance of 12.5 cm, 25 cm, 50 cm or 100 cm, whereas the distance specified by vergence and accommodative cues was always fixed at 50 cm. Judgements of the perceived depth between the two planes were uninfluenced by changes in the gradients of vertical disparity. It thus seems that the human visual system does not employ vertical disparity as a scaling parameter in stereoscopic depth judgements.