Enhancing infrared color reproducibility through multispectral image processing using RGB and three infrared channels

Abstract

Various techniques for image color reproducibility under low-light conditions have been proposed, such as high sensitivity, a combination of visible (VIS) and infrared (IR) light, and coloring monochromatic images. However, when the illuminance falls below a certain level, color images cannot be obtained without prior color information. Previously, the exclusive use of IR without VIS illumination was proposed to achieve a pseudocolor image (basic IR color). It improved visibility compared with conventional monochrome images. However, there are cases, depending on the objects, when basic IR light cannot reproduce the correct color. An image processing method for enhancing color reproducibility is proposed, particularly for objects that are not suitable for the basic IR color (enhanced IR color). Moreover, we developed an algorithm to combine the advantages of both VIS and IR colors by utilizing signals of six wavelengths: three wavelengths each of VIS and IR. The proposed method includes an automatic transition between the optimal combination of VIS and IR colors when the illumination level changes, thus providing images with superior color reproducibility under various illumination levels compared with basic IR color.