This study investigates the effectiveness of narrow-band illumination (NBI) in enhancing the visualization of vascular patterns in endoscopic imaging. The research aims to determine the optimal illumination parameters for improving the contrast of vascular patterns in the human tongue and other gastrointestinal tissues. The study compares narrow-band illumination (NBI) with broadband illumination, using five narrow-band filters and three broadband filters to evaluate the contrast of vascular patterns. The results show that NBI significantly improves the contrast of vascular patterns, particularly in the superficial layer of the tongue, compared to broadband illumination. The NBI filter set (415 ± 30 nm, 445 ± 30 nm, 500 ± 30 nm) was selected for its ability to enhance the appearance of vascular patterns for clinical use. Clinical tests in colonoscopy and esophagoscopy demonstrated that NBI is useful for detecting early-stage cancers by improving the visibility of vascular patterns and mucosal structures. The study also evaluated the appearance of capillary patterns on color images using CIE 1976 L*a*b* color difference and L* contrast. The results indicated that NBI provides better visualization of vascular patterns than conventional methods. The study concludes that NBI is a valuable tool for endoscopic imaging, particularly for detecting early-stage cancers in the gastrointestinal tract. The findings suggest that NBI can improve the accuracy of diagnosis by enhancing the visibility of vascular patterns and mucosal structures, making it a useful technique for clinical applications.This study investigates the effectiveness of narrow-band illumination (NBI) in enhancing the visualization of vascular patterns in endoscopic imaging. The research aims to determine the optimal illumination parameters for improving the contrast of vascular patterns in the human tongue and other gastrointestinal tissues. The study compares narrow-band illumination (NBI) with broadband illumination, using five narrow-band filters and three broadband filters to evaluate the contrast of vascular patterns. The results show that NBI significantly improves the contrast of vascular patterns, particularly in the superficial layer of the tongue, compared to broadband illumination. The NBI filter set (415 ± 30 nm, 445 ± 30 nm, 500 ± 30 nm) was selected for its ability to enhance the appearance of vascular patterns for clinical use. Clinical tests in colonoscopy and esophagoscopy demonstrated that NBI is useful for detecting early-stage cancers by improving the visibility of vascular patterns and mucosal structures. The study also evaluated the appearance of capillary patterns on color images using CIE 1976 L*a*b* color difference and L* contrast. The results indicated that NBI provides better visualization of vascular patterns than conventional methods. The study concludes that NBI is a valuable tool for endoscopic imaging, particularly for detecting early-stage cancers in the gastrointestinal tract. The findings suggest that NBI can improve the accuracy of diagnosis by enhancing the visibility of vascular patterns and mucosal structures, making it a useful technique for clinical applications.