A method for gauging the distance from a video camera to an object of interest is described. By using a
calibrated camera-lens system, range was related to focus of a selected object. Optimum focus of the image was
determined by maximizing the high-frequency content of the Fourier transform of the object image. The Walsh-
Hadamard transform was investigated as an alternative focusing function. Software was developed to determine
optimum image focus and control a motorized camera lens. Range values from the video camera to target objects
were calculated by the system. Calculated values were compared with measured distances. For any given distance,
the difference between calculated and actual distance averaged less than 1.2%. Distance values calculated using
the Walsh-Hadamard transform differed from values calculated with the Fourier transform by less than 1%.