Nyman G, Greenlee M W, Laurinen P
Department of General Psychology, University of Helsinki, Finland.
J Opt Soc Am A. 1988 Apr;5(4):628-35. doi: 10.1364/josaa.5.000628.
We explored the human observer's ability to detect and discriminate sine-wave and square-wave gratings that were sampled at intervals varying from 4.7 to 9.4 arcmin. To study the effect of sampling irregularity on visual performance, we varied the position of each line sample on the basis of a Gaussian probability distribution, the standard deviation of which varied from 0 (regular sampling) to 4.7 arcmin (highly irregular sampling). The results indicate that irregular sampling has no systematic effect on the observer's ability merely to detect the presence of a sine- or square-wave grating. In contrast, sampling irregularity strongly impairs the subject's ability to discriminate between these waveforms. A model based on the convolution of difference-of-Gaussians-type weighting profiles predicted that sampling irregularity should have little to no effect on the output of a channel tuned to the third harmonic of the square-wave grating. The findings thus suggest the existence of a sampling scheme in the visual system. This scheme is based on local feature-selective mechanisms, probably edge detectors, that are highly sensitive to the relative position of the sample points in the space domain.
我们探究了人类观察者检测和区分正弦波光栅与方波光栅的能力，这些光栅以4.7至9.4角分不等的间隔进行采样。为了研究采样不规则性对视觉性能的影响，我们根据高斯概率分布改变每个线条样本的位置，其标准差从0（规则采样）变化到4.7角分（高度不规则采样）。结果表明，不规则采样对观察者仅仅检测正弦波或方波光栅存在的能力没有系统性影响。相比之下，采样不规则性严重损害了受试者区分这些波形的能力。基于高斯差分类型加权轮廓卷积的模型预测，采样不规则性对方波光栅三次谐波调谐通道的输出应该几乎没有影响。这些发现因此表明视觉系统中存在一种采样方案。该方案基于局部特征选择机制，可能是边缘检测器，它们对空间域中采样点的相对位置高度敏感。
