Based on the half wave belt, we discussed the Fresnel zone plates’ diffraction, its multiple focus and light intensity of focuses.

The most popular detection methods both at home and aboard are introduced,and a method on the position control system for beam focus is presented during laser beam cutting process based on CCD,which can accurate detect and control the laser focus position during laser beam cutting process by using the laser triangulation and CCD imaging system coordination digital image proce.

Clinical research on treatment of macula edema with focal argon laser;