an apparatus and method are provided for optimizing ion implantation uniformity in a workpiece , such as a semiconductor wafer , which includes an ion beam generator for generating an ion beam , a beam scanning mechanism for diverging the ion beam and generating substantially parallel ion beam trajectories towards the workpiece , and an ion beam detector for measuring the ion beam current of the parallel ion beam trajectories as a function of the position of the ion beam detector . a uniformity controller filters the ion beam current measured by the ion beam detector to at least one predetermined resolution range and generates a uniformity signal to the beam scanning mechanism in response to the filtered ion beam current so that the workpiece is uniformly implanted . the uniformity controller determines a controllable frequency range for optimizing ion implantation uniformity control by making controllable frequencies observable and uncontrollable frequencies unobservable . as a result , the uniformity controller observes and controls spacially distributed components of the profiled beam current for optimizing the implantation of doses to the workpiece in a time and cost efficient manner .