A laser peening method and system allows the work piece to be fixed, while moving and directing the laser beam. A laser energy delivery system includes a relay imaging system. Input optics arranged to receive the laser energy, a transmitting mirror having adjustable angle of incidence relative to the input optics, and a robot mounted processing head including an optical assembly are configured to direct laser energy toward the movable target image plane. The laser energy follows an optical path including an essentially straight segment from the transmitting mirror to the receiving mirror, having a variable length and a variable angle relative to the input optics. Diagnostics on the processing head facilitate operation.