Image-based distance and area measuring systems

Abstract

In this paper, a novel measuring system using a scancounter method via a CCD camera is proposed. The proposed measuring system is an easy-to-construct system to measure the distance between a CCD camera and an object, and to measure the projected area of the object. This measuring method needs not store huge amounts of image data nor use any pattern recognition approach. It quickly obtains the distance and the projected area using simple circuits and formulas. For distance measurement, two laser projectors are set on either side of a CCD camera and produce two parallel rays that project two bright spots on the object and, therefore, on the CCD. An external clock, which is generated by an extra oscillator, is used to measure the time interval between the two bright spots as the CCD scans the image. A circuit for counting the number of external clock pulses between the two bright spots is employed to calculate the interval between them in the video image. Due to the parallel setup of the distance measuring system, there is a linear relationship between the actual distance and the interval of the two bright spots. Therefore, the actual distance from the CCD camera to the object can be calculated from a simple formula. For area measurement, circuits count the number of external clock pulses of the horizontal scan lines covering the projected area of the object. Then, the projected area of the object is calculated from simple algebraic formulas. Finally, several experimental results demonstrate the effectiveness of the proposed system.