Abstract: A rangefinding/autofocusing apparatus utilizes a joint transform correlator of a Fourier correlation optical system. A pair of imaging lens systems form a pair of object input images. A lens driving mechanism drives the imaging lens systems in a parallel manner. The pair of object input images are recorded for display. A reference input image is displayed concurrently along with the recorded object input images in an offset relation relative to each other. A photodetector disposed on the correlation plane of the Fourier correlation optical system detects correlation peaks corresponding to a correlation coefficient of the pair of displayed object input images to measure an interval between the detected correlation peaks. The photodetector also detects correlation peaks corresponding to a correlation coefficient of the reference input image and the object input images to determine a correlation between the reference image and the object.