Detect defects in liquid crystal displays in recent years，liquid crystal display technology，has been a qualitative leap Liquid crystal displays are larger desktop computer monitors and high-resolution，high brightness，large screen color LCD projection television sets，the direction of rapid development．However，the difficulty of its production has exceeded VLSI。Its maximum yield only 60% ~ 70%．TFT-AMLCD screen for defects in repair and use of laser redundancy technology to improve their yields are an important means，and to repair defects，first of all to identify deficiencies in the type and precise location，which requires the corresponding defect detection technology．