Abstract: A position encoder system is disclosed for determining the position of an object. The system includes a camera, a ruled scale, and a control system. The system first obtains a pixel brightness image of the ruled scale attached to the object and downloads this data image to a computer. The computer, running a fast position determination, determines the fundamental frequency of the image through the use of a Fourier transform of the pixel brightness variations in the image. The phase difference between the fundamental frequency and a reference is then converted into an actual position of the object since the spacing of the individual rulings on the scale is known and one cycle of the fundamental frequency corresponds to one spacing interval on the rulings. With this measurement of the actual position, the control system compares it to the desired position and, if necessary, corrects the position of the object.