Application of semiconductor laser range finder to position control of lens in auto-focus camera

It is proposed to use an infrared semiconductor laser rangefinder to get a just-focusing signal, for the auto-focus (AF) system of a camera. Using both a measured distance to a moving object and its speed, the lens position of a single-lens reflex (SLR) camera is controlled. The range measurement error when installed in the AF system of an SLR camera is within 1% in a range of 0.3 m to 0.6 m. The error of 1% is below the normalized depth of field of 1.5-4.0% of the camera lens, which is consistent with the fact that some clear photographs are obtained from a moving object.<>