Applications of Circular Array Sensors

Abstract

The application of the Reticon RO-64 annular photo-diode array to the task of optical tracking of special targets, direct optical focusing, and automatic printed circuit board inspection were studied. In order to facilitate this work, a digital camera unit incorporating the array was designed and constructed. Of the three applications investigated, the tracking task proved to be the most successful, since multiple targets were tracked in real time using the array. In the focusing application, the digital approach was found to be too slow for real-time use, and suggestions were made for the analog implementation of a focusing algorithm using the array. The printed circuit board inspection algorithm detected errors successfully, but the inefficiency of image acquisition with the array is a serious drawback, leading to the conclusion that linear arrays of similar design would provide faster and less expensive inspection. Thus the annular geometry is best suited to the onetime sampling of points on a circle in an image, as in the case of the tracking and focusing tasks. The focusing task suffers mainly from the amount of computation required to achieve focus, and from its competition with more established indirect focusing techniques.