抄録
Border detection between the two monochromatic stimuli (we called them, test and reference) was investigated for a wide range of reference luminance in various surround luminance conditions. Luminance contrast for the border detection shows U shaped curve for each level of surround luminance when plotted against the luminance of reference stimulus. As the surround luminance increases, the U shaped curve shifts toward higher luminance direction, and the lowest contrast value decreases indicating the increase of sensitivity for border detection. Results are discussed in relation to the physiological property of human visual system.