FPGA implementation of an algorithm for coding illumination-independent color information

Abstract

Coding illumination-independent color information is an important feature for robotic vision because the apparent color of objects is strongly affected by the illumination condition. In this study, we developed a sensor system with color constancy that consists of a CMOS image-sensor and a field-programmable gate array (FPGA). To achieve color constancy, we designed a digital circuit that offers color constancy based on the center / surround retinex model, and the circuit was implemented on the FPGA. The digital circuit contains the following functions: integration of multiple exposure images, logarithmic transformation, and difference-of-Gaussian spatial filtering. The system was tested by presenting Mondrian under varying color of illumination. As a result, the system successfully reduced the influence of the color of the illumination.