Knill D C, Field D, Kersten D
Department of Psychology, Brown University, Providence, Rhode Island 02912.
J Opt Soc Am A. 1990 Jun;7(6):1113-23. doi: 10.1364/josaa.7.001113.
In order to transmit information in images efficiently, the visual system should be tuned to the statistical structure of the ensemble of images that it sees. Several authors have suggested that the ensemble of natural images exhibits fractal behavior and, therefore, has a power spectrum that drops off proportionally to 1/f beta (2 less than beta less than 4). In this paper we investigate the question of which value of the exponent beta describes the power spectrum of the ensemble of images to which the visual system is optimally tuned. An experiment in which subjects were asked to discriminate randomly generated noise textures based on their spectral drop-off was used. Whereas the discrimination-threshold function of an ideal observer was flat for different spectral drop-offs, human observers showed a broad peak in sensitivity for 2.8 less than beta less than 3.6. The results are consistent with, but do not provide direct evidence for, the theory that the visual system is tuned to an ensemble of images with Markov statistics.
为了有效地在图像中传输信息，视觉系统应根据其所见图像集合的统计结构进行调整。几位作者提出，自然图像集合呈现分形行为，因此具有与1/fβ成比例下降的功率谱（2＜β＜4）。在本文中，我们研究了指数β取何值可描述视觉系统最优调整的图像集合的功率谱这一问题。我们进行了一项实验，要求受试者根据频谱下降情况区分随机生成的噪声纹理。理想观察者的辨别阈值函数对于不同的频谱下降情况是平坦的，而人类观察者在2.8＜β＜3.6时表现出灵敏度的宽峰。这些结果与视觉系统针对具有马尔可夫统计的图像集合进行调整的理论一致，但并未提供直接证据。
