Richards W
Biol Cybern. 1979 Aug 1;33(3):125-35. doi: 10.1007/BF00337290.
A key problem in vision is to normalize one's lightness scale so that surface reflectances are always assigned the same gray value regardless of the illumination level. The solution requires an assessment of the relation between the strength of the illuminant and the strength of the image signal-information that is not available in the image alone. However, the level of scattered light in the optical system does provide an independent measure of the illuminant strength, and can be used to solve the lightness scale normalization problem. To do this requires a comparison between two imaging systems, each of which respond differently to the internal optical scatter. The rod and cone systems have properties that are ideally suited for such a role.
视觉中的一个关键问题是对自身的亮度尺度进行归一化，以便无论光照水平如何，表面反射率总是被赋予相同的灰度值。解决这个问题需要评估光源强度与图像信号强度之间的关系——而这种信息仅从图像本身是无法获得的。然而，光学系统中的散射光水平确实提供了一种独立的光源强度测量方法，并且可用于解决亮度尺度归一化问题。要做到这一点，需要比较两个成像系统，每个系统对内部光学散射的响应都不同。视杆和视锥系统具有非常适合这一作用的特性。
