Effects of the retina-inspired light intensity encoding on color discrimination performance

TL;DR

This study explores how different light intensity encoding functions, inspired by retinal responses, affect color discrimination performance in a retinex model, highlighting the Naka-Rushton function's advantages.

Contribution

It introduces the use of the Naka-Rushton function in a retinex model and demonstrates its effectiveness in improving color discrimination performance.

Findings

Naka-Rushton function improves color discrimination.

Double opponent color plane enhances performance.

N-R function outperforms logarithmic encoding.

Abstract

Color is an important source of information for visual functions such as object recognition, but it is greatly affected by the color of illumination. The ability to perceive the color of a visual target independent of illumination color is called color constancy (CC), and is an important feature for vision systems that use color information. In this study, we investigated the effects of the light intensity encoding function on the performance of CC of the center/surround (C/S) retinex model, which is a well-known model inspired by CC of the visual nervous system. The functions used to encode light intensity are the logarithmic function used in the original C/S retinex model and the Naka-Rushton (N-R) function, which is a model of retinal photoreceptor response. Color-variable LEDs were used to illuminate visual targets with various lighting colors, and color information computed by each model was used to evaluate the degree to which the color of visual targets illuminated with different lighting colors could be discriminated. Color information was represented using the HSV color space and a color plane based on the classical opponent color theory. The results showed that the combination of the N-R function and the double opponent color plane representation provided superior discrimination performance.