Analysis of the Focusing Characteristics of Double Negative Binary Diffractive Lens

For a compact millimeter wave imaging system it is very important to design every component into small size, for the components in a millimeter wave system are usually much larger than those in an optical imaging system due to relatively long wave lengths. In this paper, we suggest a kind of binary diffractive lens (BDL) designed using double negative materials (DNG) as the objective lens for a millimeter wave imaging system. The DNG-BDL has not only the advantage of low profile but also small f number, which will be benefit for constructing a compact millimeter wave imaging system. Several DNG-BDL are designed and analyzed using the FDTD method. The numerical results of the focal plane field of the DNG-BDL are presented, which show that the DNG-BDL with small f number has relatively better focusing characteristic than that of a double positive BDL with same f number.