Area measurement at long-distance using a circular Dammann grating.
We describe a novel method of noncontact mode area measurement at long distance of 11.25 m by borrowing the concept of a circular Dammann grating (CDG). The area of objects can be determined accurately by measuring the circular spectrum diameter of the CDG. This noncontact mode measurement requires neither a large amount of image data nor any pattern recognition approach. The spectrum diameter is derived from simple lens formulas. From the fractional Fourier transform, we find that there exists a linear relationship between the spectrum diameter and the distance traveled by the CDG. Compared with the conventional methods, this technique has the advantages of a simple design with good accuracy of better than 3%, low cost, noncontact mode, and a more compact design. Finally, we present several experimental results demonstrating the effectiveness of this system.
Wen
Fung Jacky
FJ
Department of Electronic Engineering, City University of Hong Kong, 83, Tat Chee Avenue, Kowloon Tong, Hong Kong, China.
Chen
Zhongyu
Z
Chung
Po Sheun
PS