Quantitative evaluation of a new gamma correction method for endoscopic image improvement

Abstract

Endoscopic illumination system designs are inherently space restricted resulting in non-uniform illumination patterns. Tubular tissues and organs have significant lengths relative to these fixed illumination patterns, resulting in dark areas further away from the imaging sensor and over-saturated areas closer to the sensor. Occlusions and obstructions in the illumination path can also result in significant shadowing. A gamma correction is normally applied to map luminance levels and adjust for the significant variations that can occur. During the process, the color information isn’t taken into consideration. In this paper, a new gamma correction method was proposed to increase image contrast and sharpness by utilizing pixel information from all color channels. Raw data was collected for various scenes and processed using the regular and proposed gamma correction method. Images were quantitatively compared using entropy and sharpness metrics. Both subjective interpretation and these statistics show that the proposed gamma correction method offers enhancement over the regular gamma correction method by increasing the entropy and maintaining the sharpness closer to the original image.