Comparative trial of diagnositic ability for colorectal tumor of Narrow band imaging (NBI), Blue laser imaging (BLaI) and Blue light imaging (BLiI)

Interventions: Diagnose colorectal tumor with NBI(Narrow band imaging) Diagnose colorectal tumor with BLaI(Blue laser imaging) Diagnose colorectal tumor with BLiI(Blue light imaging) Primary outcome(s): Precise diagnosis rate of NBI, BLaI and BLiI for colorectal polyps Study Design: Parallel Randomized