Abstract
Fresnel lens is well known as a low-weight and thin-structure. In order to use Fresnel lens for passive millimeter-wave imaging, it is necessary to evaluate degradation of focusing property by zoning. In this paper, fundermental characteristics of Fresnel lens such as focusing point and electric field intensity around focal point are numerically analyzed by using two-dimmensional FDTD (Finite-Difference Time-Domain) analysis and compared with the case of aspheric lens. Detailed study of effect of the base thickness of lens on fundermental characteristics is performed, and structure parameters of Fresnel lens having mechanical strength and high electric field intensity are obtained. It is observed that electric field intensity of Fresnel lens around focal point is only 0.5dB less than that of aspheric lens. Fresnel lens designed by FDTD analysis is fabricated and its characteristics are measured confirming the validity of the design based on FDTD method.
