Brainard D H, Wandell B A, Cowan W B
IEEE Trans Biomed Eng. 1989 Jan;36(1):140-9. doi: 10.1109/10.16459.
Visual sensor responses may be used to classify objects on the basis of their surface reflectance functions. In a color image, the image data are represented as a vector of sensor responses at each point in the image. This vector depends both on the surface reflectance function and on the spectral power distribution of the ambient illumination. Algorithms designed to classify objects on the basis of their surface reflectance functions typically attempt to overcome the dependence of the sensor responses on the illuminant by integrating sensor data collected from multiple surfaces. In machine vision applications, we show that it is often possible to design the sensor spectral responsivities so that the vector direction of the sensor responses does not depend upon the illuminant. We state the conditions under which this is possible and perform an illustrative calculation. In biological systems, where the sensor responsivities are fixed, we show that some changes in the illumination cause no change in the sensor responses. We call such changes in illuminant black illuminants. It is possible to express any illuminant as the sum of two unique components. One component is a black illuminant. We call the second component the visible component. The visible component of an illuminant completely characterizes the effect of the illuminant on the vector of sensor responses.
视觉传感器响应可用于根据物体的表面反射函数对物体进行分类。在彩色图像中，图像数据表示为图像中每个点处传感器响应的向量。该向量既取决于表面反射函数，也取决于环境光照的光谱功率分布。旨在根据物体表面反射函数对物体进行分类的算法通常试图通过整合从多个表面收集的传感器数据来克服传感器响应对照明光源的依赖性。在机器视觉应用中，我们表明通常可以设计传感器光谱响应度，使得传感器响应的向量方向不依赖于照明光源。我们阐述了实现这一点的条件并进行了一个说明性计算。在生物系统中，传感器响应度是固定的，我们表明光照的某些变化不会导致传感器响应发生变化。我们将这种光照变化称为黑色光源。可以将任何光源表示为两个独特分量的总和。一个分量是黑色光源。我们将第二个分量称为可见分量。光源的可见分量完全表征了光源对传感器响应向量的影响。
