Viewing Geometry and Stereoscopic Vision

PI：班克斯，马丁。这项被提议的研究将调查我们通过双目视觉看到三维世界的方法。研究将集中在两个问题上：1)人类视觉系统如何解决双目视觉中的“匹配问题”；2)视觉系统如何根据双目深度线索表示表面形状和方向。双目视觉中的匹配问题已经被研究了几十年。我们仍然不完全明白这个问题是如何解决的。匹配问题简单地说就是：对于左眼的每一个图像点，视觉系统必须在另一只眼睛中找到合适的点与之匹配。对于N个可能的点，理论上可能的匹配数量为N4，因此当N较大时，匹配过程在计算上可能变得难以管理。视觉系统可以通过使用所谓的极缘约束来大量减少可能匹配的数量。对于一只眼睛中的图像点，其匹配点必须位于另一只眼睛中相应的极线上。利用极极约束，可以将匹配问题简化为一维搜索。然而，当眼睛的位置发生变化时（例如从远注视到近注视），视网膜上相应的极外线的位置和方向也会发生变化。因此，为了实现极外约束，视觉系统必须考虑眼睛的位置。我们已经开发了一种实验程序，它将允许我们确定视觉系统是否使用极外约束，如果是，系统使用什么信号来计算当眼睛移动时，极外线应该如何移动。我们还将研究在视觉系统中表示表面形状的方法。表面形状的一个重要线索是到达两只眼睛的水平差异的模式，但这些差异本身不能产生对形状的真实估计。其他信号，如垂直差异或眼睛位置信号也必须使用。我们在之前的研究中已经表明，即使视网膜差异完全不变，眼睛的聚光变化也会导致感知形状的显著变化。我们还知道，长时间观看曲面会导致随后观看的平面呈现相反方向的弯曲。像这样的后效被称为“视差后效”，因为提供的解释只涉及视差编码。在提议的研究中，我们将研究曲率的后效。通过独立操纵眼位信号和视网膜差异，我们可以确定后效是由差异编码机制之间的适应引起的（这是主流理论），还是由更高层次的形状编码机制的适应引起的。初步测量表明，后一种假设更能预测数据。我们还将确定在不同的观看条件下所涉及的各种信号（例如，眼肌信号和垂直差异）是如何加权的。所提出的工作将使人们更好地了解双眼视觉的这些方面，从而可能对改进视觉辅助工具（如双目显微镜、头戴式显示器和头盔显示器以及其他现实显示器）产生见解。

PI: Banks, MartinThe proposed research will investigate the means by which we see 3-dimensionally via binocular vision. The research will focus on two issues: 1) how the human visual system solves the "matching problem" in binocular vision and 2) how the visual system represents surface shape and orientation from binocular depth cues.The matching problem in binocular vision has been actively researched for decades. We still do not fully understand how the problem is solved. The matching problem is simply stated in the following way: For every image point in the left eye, the visual system must find the appropriate point in the other eye to match with it. With N possible points, the number of theoretically possible matches is N4 so with large N the matching process can become computationally unmanageable. The visual system can massively reduce the number of possible matches by using what is termed the epipolar constraint. For an image point in one eye, its match must lie on the corresponding epipolar line in the other eye. By using the epipolar constraint, the matching problem can be reduced to a one-dimensional search. However, when the eyes' positions change (e.g., fixating from far to near), the positions and orientations of corresponding epipolar lines change on the retina. Thus, to implement the epipolar constraint, the visual system must take the eyes' positions into account. We have developed an experimental procedure that will allow us to determine whether the visual system uses the epipolar constraint and, if so, what signals the system uses in order to calculate how epipolar lines ought to move when the eyes move.We will also examine the means by which surface shape is represented in the visual system. An important cue to surface shape is the pattern of horizontal disparities arriving at the two eyes, but those disparities by themselves cannot yield a veridical estimate of shape. Other signals such as vertical disparities or eye-position signals must be used as well. We have shown in the previous grant period that changes in the eyes' vergence can cause a compelling change in perceived shape even when the retinal disparities are completely constant. We also know that prolonged viewing of a curved surface causes a subsequently viewed flat surface to appear curved in the opposite direction. Aftereffects like this have been called "disparity aftereffects" because the explanations offered refer to disparity encoding alone. In the proposed research, we will examine the curvature aftereffect. By manipulating eye-position signals and retinal disparities independently, we can determine whether the aftereffect is caused by adaptation among disparity-encoding mechanisms (which is the prevailing theory) or whether it is caused by adaptation in higher-level, shape-encoding mechanisms. Preliminary measurements suggest that the latter hypothesis is a better predictor of the data. We will also determine how the various signals involved (e.g., eye-muscle signals and vertical disparities) are weighted under different viewing conditions.The proposed work will yield a better understanding of these aspects of binocular vision and, consequently, may yield insights into improvements in visual aids such as binocular microscopes, head- and helmet-mounted displays, and other realistic displays.