对交替呈现的立体图对的双眼立体视觉的探讨

本实验用APPLE Ⅱ微机控制的同视机,选用医用三级检查图片中的彩色和黑白两种立体图对,对30名被试进行实验。结果表明:(1)在同视机条件下,当双眼图象交替闪烁相位的交替频率平均在7Hz以上时,双眼立体视觉形成。(2)双眼刺激交替呈现时,彩色图对的立体感闪烁融合阈值约为33Hz,黑白图对的立体感闪烁融合阈值约为25Hz,两者差异十分显著(P<0.0001)。     

不同背景照明光下正确辨认颜色灯光信号的亮度对比阈

本研究的目的是考察辨认颜色灯光信号的亮度对比阈与背景亮度的关系。实验采用了色温3100k和5000k两种照明光,信号灯的颜色分红、橙、绿三种。实验结果表明:(1)随着背景亮度的提高,亮度对比阈以递减速度下降;当背景亮度达到100cd/m~2以上时,亮度对比阈渐趋稳定。(2)在两种不同色温照明光下,色灯信号的辨认效果无明显差异。     

正常和弱视者立体和形状视觉感知时间的差异

在速示器,以随机点立体图对为刺激,测量了正常和弱视者的立体视和形状视感知时间。实验表明:正常被试需要大约100ms感知深度,110ms或更长时间感知形状。这二种感知时间与刺激视差的种类和大小无关。弱视者需要比正常人较长的时间达到立体和形状的视感知。这二种感知时间的差别,弱视者也大于正常人。视锐度和立体视范围均恢复到正常的弱视者,以上二种感知时间,可以达到正常人范围,也可能显著地大于正常人。     

与立体视觉相关的视诱发电位研究

在微机上编制能产生动态随机点立体图（ＤＲＤＳ）,亮暗类棋盘格和随机点背景三种图形刺激的软件．记录了３４例正常人在这三种刺激下的ＶＢＰ．其结果为：（１）ＤＲＤＳ刺激下的ＶＥＰＮ１波潜伏期为２６５±２５ｍｓ,基波能量占总交流能量的６３．２±１８．９％．（２）亮暗类棋盘格刺激下的ＶＥＰＮ１波的潜伏期为１９０±２２ｍｓ,基波能量占总交流能量的３９．２±１９．６％．（３）随机点背景刺激下的ＶＥＰ波则为一些杂乱的小波．结果提示：动态ＲＤＳ刺激下的ＶＥＰ除在潜伏期方面具有特异性外,并在谐波的能量分布上也具有特异性,且客观性更强．根据这些特征有助于对立体视觉功能进行客观性评价．     

附加点作用下两点距离的触觉辨别

在被动触觉的距离知觉实验中,被试的右手保持不动,将各种三点型式的刺激轻轻接触食指腹侧或以一定速度通过其表面,要求被试判定外侧两点的直线距离并在一根量尺上复现出来．结果发现：（１）当刺激快速通过皮肤表面时,外侧两点距离表现出低估,其知觉距离显著地小于刺激静止或慢速运动条件下的知觉距离;（２）当中间附加点偏离外侧两点间想象连线较大时,外侧两点的知觉距离显著地小于中间附加点偏离较小时的知觉距离,偏离较大的中间附加点似乎将外侧两点拉近了,缩短了其知觉距离,出现知觉亲和现象．这种现象与刺激是否运动无关．     

基于双眼视差的立体视觉去掩蔽效应

基于双眼视差的立体视觉不改变目标与掩蔽刺激之间的信噪比, 但能使不同的刺激被知觉在不同的深度位置上以降低目标信号所受到的掩蔽作用。本综述在总结前人双眼去掩蔽研究的基础上, 强调深度维度上的视觉注意在这种主观空间分离去掩蔽过程中所起的重要作用, 并介绍了双眼去掩蔽在现代科技领域中的典型性应用。最后, 结合听觉主观空间分离去掩蔽的研究进展, 本综述认为主观空间分离去掩蔽是大脑处理复杂刺激场景的一个基本功能。     

亮度对空间-数字反应编码联合效应的影响

本研究探讨亮度对空间-数字反应编码联合效应（Spatial-Numerical Association of Response Codes,简称SNARC效应）的影响及其机制。通过三个实验设计不同的亮度对比水平,要求被试对阿拉伯数字1~9（5除外）进行奇偶判断。实验一将数字亮度设为最高值255时,结果出现了数字的SNARC效应。实验二将数字的亮度值分别设为255和213时,结果仍存在SNARC效应。实验三将亮度值分别设置为213和42时,数字的SNARC效应却消失了。这些结果表明亮度会激活或抑制数字的空间表征,可能与亮度对比值的高低及所消耗认知资源的多少有关。     

短时距知觉中的面积效应

初步探讨了短时距（１─５ｓ）下时距刺激的面积大小和立体框架大小对时距知觉的影响及其成因。结果表明：刺激的面积大小对短时距知觉的影响极其显著;存在两种不同反应类型的被试─－大小依存者与非大小依存者,在不同反应类型的被试中刺激的立体框架大小对短时距知觉的影响不同,刺激的立体框架大小对大小依存者的短时距知觉的影响极其显著,但对非大小依存者的影响不显著。     

沃尔夫假说的新证据:范畴内和范畴间颜色辨别难度相同时语言范畴也会影响注意前颜色知觉

该研究探讨了当范畴内和范畴间颜色的辨别难度相同时,语言范畴是否会影响注意前颜色知觉。实验中,采用渐变且相邻者差别阈限数相当的A、B、C、D四种颜色（前两者为绿色,后两者为蓝色）为刺激材料,并让被试接受视觉Oddball脑电测试。脑电测试分视野给被试呈现标准刺激,以及与标准刺激属同一语言范畴（即颜色词绿色或蓝色）或不同语言范畴的偏差刺激。结果发现：在左视野呈现时,范畴内偏差刺激比范畴间偏差刺激诱发了边缘显著更大的视觉失匹配负波（vMMN）,在右视野呈现时,两类偏差刺激诱发的vMMN无显著差异;范畴内偏差刺激在不同视野呈现时诱发的vMMN无显著差异,范畴间偏差刺激则在右视野呈现时诱发了显著更大的vMMN。这一结果表明,当范畴内和范畴间颜色的辨别难度相同时,语言范畴也会影响早期的、注意前颜色知觉,支持了沃尔夫假说。     

周边视觉的知觉学习

知觉学习是指知觉能力随着知觉训练或经验逐渐改变的现象。它具有特异性-迁移性,可以根据时程划分为快速学习和慢速学习。知觉学习意味着与知觉直接对应的脑区神经元激活方式的变化,并且与注意有着一定的联系。目前周边视觉的知觉学习研究已有一些成果：对于非语词刺激,随着练习,判断目标刺激（例如刺激朝向、游标视敏度）的能力,有很大的提升;对于语词刺激,周边视觉的知觉学习可以帮助提高阅读速度。可以通过提高视觉广度来提高周边视觉的阅读速度。周边视觉的知觉学习还有着重大应用价值,可以帮助中央凹视觉缺损的人们提高周边视觉能力,帮助恢复阅读能力。     

Perceiving surfaces in depth beyond the fusion limit of their elements

An isolated dot appears double outside a small disparity range called Panum's fusional area. In random-dot stereograms (RDSs), however, this doubling, or diplopia of dot elements is not evident at any disparity. Nevertheless, depth is perceived up to disparities that greatly exceed Panum's fusional limit. Either one is unaware of dot diplopia at disparities exceeding Panum's fusional limit or the fusion limit is extended. To examine these possibilities, we developed a novel RDS in which dichoptically color-coded dots have a distinctive color when fused, and return to their intrinsic colors when diplopic. We measured the fusion limit of dots in this RDS, and compared it to the patent stereopsis limit of the perceived surface in similar RDSs. We found that the fusional area of dots in the RDS was comparable to Panum's fusional area. Furthermore, there was clear dissociation between the fusion limit and the patent stereopsis limit in the RDS. We conclude that the elements composing a surface are not necessarily fused when a large disparity surface is perceived in depth.     

复杂图形的双眼视差敏感性

该研究用心理物理学实验方法,以能正确分辨图形在深度上起伏周期数的多少作为判据,检测了七名被试的体视性能。实验结果表明,被试者观看复杂图形的视差敏感性是和图形在深度上变化的复杂程度有关。如果以视差作纵坐标,以图形在深度起伏频率为横坐标,则其深度感知的范围是一个区域,该区域的频率变化范围是从０．１周／度到４周／度,当深度变化频率大于４周／度,则无深度感知。七名被试的双眼深度敏感区有个体差异,但其区域的形状是相似的。     

Suprathreshold stereo-depth matches as a function of contrast and spatial frequency

Thresholds for stereoscopic-depth perception increase with decreasing spatial frequency below 2.5 cycles deg-1. Despite this variation of stereo threshold, suprathreshold stereoscopic-depth perception is independent of spatial frequency down to 0.5 cycle deg-1. Below this frequency the perceived depth of crossed disparities is less than that stimulated by higher spatial frequencies which subtend the same disparities. We have investigated the effects of contrast fading upon this breakdown of stereo-depth invariance at low spatial frequencies. Suprathreshold stereopsis was investigated with spatially filtered vertical bars (difference of Gaussian luminance distribution, or DOG functions) tuned narrowly over a broad range of spatial frequencies (0.15-9.6 cycles deg-1). Disparity subtended by variable width DOGs whose physical contrast ranged from 10-100% was adjusted to match the perceived depth of a standard suprathreshold disparity (5 min visual angle) subtended by a thin black line. Greater amounts of crossed disparity were required to match broad than narrow DOGs to the apparent depth of the standard black line. The matched disparity was greater at low than at high contrast levels. When perceived contrast of all the DOGs was matched to standard contrasts ranging from 5-72%, disparity for depth matches became similar for narrow and broad DOGs. 200 ms pulsed presentations of DOGs with equal perceived contrast further reduced the disparity of low-contrast broad DOGs needed to match the standard depth. A perceived-depth bias in the uncrossed direction at low spatial frequencies was noted in these experiments. This was most pronounced for low-contrast low-spatial-frequency targets, which actually needed crossed disparities to make a depth match to an uncrossed standard. This bias was investigated further by making depth matches to a zero-disparity standard (ie the apparent fronto-parallel plane). Broad DOGs, which are composed of low spatial frequencies, were perceived behind the fixation plane when they actually subtended zero disparity. The magnitude of this low-frequency depth bias increased as contrast was reduced. The distal depth bias was also perceived monocularly, however, it was always greater when viewed binocularly. This investigation indicates that contrast fading of low-spatial-frequency stimuli changes their perceived depth and enhances a depth bias in the uncrossed direction. The depth bias has both a monocular and a binocular component.     

Accuracy of stereomotion speed perception with persisting and dynamic textures

It has been established that the motion in depth of stimuli visible to both eyes may be signalled binocularly either by a change of disparity over time or by the difference in the velocity of the images projected on each retina, known as an interocular velocity difference. A two-interval forced-choice stereomotion speed discrimination experiment was performed on four participants to ascertain the relative speed of a persistent random dot stereogram (RDS) and a dynamic RDS undergoing directly approaching or receding motion in depth. While the persistent RDS pattern involved identical dot patterns translating in opposite directions in each eye, and hence included both changing disparity and interocular velocity difference cues, the dynamic RDS pattern (which contains no coherent monocular motion signals) specified motion in depth through changing disparity, but no motion through interocular velocity difference. Despite an interocular velocity difference speed signal of zero motion in depth, the dynamic RDS stimulus appeared to move more rapidly. These observations are consistent with a scheme in which cues that rely on coherent monocular motion signals (such as looming and the interocular velocity difference cue) are less influential in dynamic stimuli due to their lack of reliability (i.e., increased noise). While dynamic RDS stimuli may be relatively unaffected by the contributions of such cues when they signal that the stimulus did not move in depth, the persistent RDS stimulus may retain a significant and conflicting contribution from the looming cue, resulting in a lower perceived speed.     

How is motion disparity integrated with binocular disparity in depth perception?

Two experiments presented motion disparity conflicting with binocular disparity to examine how these cues determined apparent depth order (convex, concave) and depth magnitude. In each experiment, 8 subjects estimated the depth order and depth magnitude. The first experiment showed the following. (1) The visual system used one of these cues exclusively in selecting a depth order for each display. (2) The visual system integrated the depth magnitude information from these cues by a weighted additive fashion if it selected the binocular disparity in depth order perception and if the depth magnitude specified by motion disparity was small relative to that specified by binocular disparity. (3) The visual system ignored the depth magnitude information of binocular disparity if it selected the motion disparity in depth order perception. The second experiment showed that these three points were consistent whether the subject’s head movement or object movement generated motion disparity.     

三维空间中不同视野深度位置上的返回抑制

通过虚拟现实构建虚拟三维场景,将二维平面视觉空间返回抑制范式应用到三维空间,通过两个实验操纵了目标深度、线索有效性以及视野位置三个变量,考察注意在三维空间不同视野深度位置上进行定向/重定向产生的返回抑制效应。结果发现,(1)二次线索化位于固定的中央视野时,不论目标出现在近处空间还是出现在远处空间,外周视野条件下的返回抑制大于中央视野条件下的返回抑制;(2)二次线索化位于非固定的中央视野时,近处空间和远处空间的返回抑制存在分离,表现为当目标出现在远处空间时,外周视野条件下的返回抑制效应减小。研究表明,三维空间中外周视野深度位置上的返回抑制与中央视野深度位置上的返回抑制存在差异。     

The minimum contrast requirements for stereopsis.

A number of researchers have compared the contrast requirements for stereopsis with those for detection of the stereoscopic stimulus, but they have generally failed to allow for the fact that stereopsis requires a detectable stimulus in both eyes at the same time. It is argued that the most appropriate detection threshold for this comparison is that for simultaneous monocular detection (SMD) of the stereoscopic half images. Experiments in which this comparison threshold has been used are summarised and the hypothesis generated that, on using stimuli that are localised in both space and spatial frequency (e.g. Gabor patches or differences of Gaussians), a range of disparities can always be found over which contrast thresholds for depth identification are less than or equal to this SMD threshold (the SMD hypothesis). It is argued that the success of this hypothesis in describing data obtained with these stimuli is consistent with the notions of labelled lines for disparity sign and the size--disparity correlation. Last, experiments are reported in which contrast thresholds for stereoscopic depth identification (front/back) were measured with interocular differences in contrast. The data obtained are consistent with the presence of both inhibitory and excitatory interactions between the eyes when unequal monocular contrasts are presented. The implications of these results and the SMD hypothesis for theories of stereopsis and binocular function are discussed.     

Depth capture by kinetic depth and by stereopsis

The perceived depth of regions within a stereogram lacking explicit disparity information can be captured by the surface structure of regions where disparity is explicit: stereo capture. In two experiments, observers estimated surface curvature/depth of an untextured object (a 'ribbon') superimposed on a cylinder textured with dots, the cylinder curvature being defined by disparity (stereo depth) or by motion parallax (kinetic depth: KD). With the stereo-defined cylinder, depth capture was obtained under conditions where the disparity of the ribbon was ambiguous; with the KD, cylinder depth capture was obtained under conditions where the motion flow of the cylinder was in a direction parallel to that of the ribbon. These results demonstrate yet another similarity between KD and stereopsis.     

Perception of depth: Different processing times for simple and relative positional disparity

Summary When judging in stereoscopic vision whether an object is lying in front of or behind the point of momentary fixation, the visual system extracts depth information by using retinal disparity; in this case it computes one angular difference between retinal images (simple positional disparity). But if the task is to discriminate two or more objects in their depth (relative to the point of fixation) and the relative distances between them, two or more such angular differences have to be determined (relative positional disparity). An investigation was carried out to determine whether depth extraction is more complex for relative distances than for object positions and therefore demands a longer processing time. For this purpose stimuli with simple and relative positional disparity were foveally and parafoveally presented (each followed by a masking stimulus). It was shown that the duration threshold for the detection of stimuli with relative disparity was about 2.5 times larger than that for stimuli with simple disparity (Exp. 1). This difference could not be attributed to differences in stimulus configuration between simple and relative disparity (Exp. 2). The results are discussed in terms of a serial, hierarchically structured, disparity processing.     

What is the diplopia threshold?

The magnitude and nature of the diplopia threshold, that is, the value of the retinal disparity at which binocular single vision ends, were studied in four experiments. The results show that the magnitude of the diplopia threshold is highly dependent on the subject tested (differences up to a factor of 6), the amount of training the subject has received (differences up to a factor of 2.5), the criterion used for diplopia (limits for unequivocal singleness of vision were up to a factor of 3 lower than those for unequivocal doubleness of vision), and the conspicuousness of disparity that can be influenced both by the surrounding stimuli (differences up to a factor of 3.5) and stereoscopic depth (differences up to a factor of 4.5). Our data do not confirm previous findings of interference effects associated with the initial appearance of binocular disparity when test stimuli are presented tachistoscopically. A remarkable finding was that the magnitude of the diplopia threshold seems to be determined by the amount of intrinsic noise in the disparity domain, as revealed by the standard deviations of the thresholds for tachistoscopically presented test stimuli. The overall results suggest that the diplopia threshold is, in essence, not the rigid boundary of a dead zone, but, rather, a disparity level corresponding to a lenient criterion for singleness of vision which leads touseful interpretation of the percept of the stimulus without disparity, given the variability of this percept due to intrinsic noise in the disparity domain.