Patent ID: 7133188

Claim:
A method for enhancing beam positioning control and from an AOM suited for positioning along a beam path between a laser and a workpiece, the AOM having a beam entrance surface, a beam exit surface, and a first transducer modulation zone that traverses the beam path and affects deflection of the beam path along a first workpiece axis with respect to a surface of the workpiece, comprising: generating a laser beam along a beam path that impinges a workpiece at a nominal beam position; propagating the laser beam through the entrance surface of the AOM positioned along the beam path, the beam path impinging the AOM at an entrance angle that is at or in proximity to a Bragg angle with respect to the beam entrance surface of the AOM and the beam path exiting the AOM at an exit angle with respect to the beam exit surface, wherein diverting the beam path from the Bragg angle reduces Bragg efficiency to a lower Bragg efficiency as a function of the degree of shift in the exit angle from the Bragg angle and wherein a large angle shift results in an undesirable low Bragg efficiency; controlling a first frequency of a first RF signal applied to a first transducer positioned on a first transducer surface of the AOM, the first transducer surface being transverse to the beam entrance surface, and the first transducer modulating within the first transducer modulation zone to shift with the AOM the beam path from the Bragg angle; controlling a Bragg adjustment device upstream of the AOM to shift the entrance angle at the beam entrance surface of the AOM to reduce loss of Bragg efficiency resulting from the shift of the exit angle; and coordinating the shift of the entrance angle and the first frequency of the first RF signal to divert the beam path from a nominal beam position on the workpiece to impinge the workpiece at a desired beam position resulting from a cooperative deflection angle imparted by the Bragg adjustment device and the AOM with an overall Bragg efficiency that is greater than the undesirable low Bragg efficiency.