Abstract
This paper presents the new technique for auto-focusing of a TV camera.
An image blur caused by defocusing produces an easy gradient of video signal. The gradient is measured by crossing frequency of a detecting signal over the video signal. This detecting signal is made by superposing a test signal on a threshold level. Using this technique, an efficient blur detection is fully possible with an appropriate selection of three parameters: the threshold level, the frequency of the test signal and the amplitude of the test signal.
By this method, a blur detector is made, the practical parameters are fixed and the range of application is shown. Then, the blur detector and the servo-controlled focus ring are connected, and an auto-focusing experiment is tried.
The results show that this technique is applicable enough to detect the focus inappropriateness of almost all objects.
