A complex dielectric lens in slab shape which is made of electromagnetic-induction materials (cage-shaped granules of conductor materials) and polymethyl methacrylate materials is proposed. Active millimeter wave imaging on focal plane with compound lens which consists of two complex dielectric lenses is investigated. The imaging system is introduced. The parameters of the millimeter wave source, the compound lens and the scanning imaging system are given. Millimeter wave imaging of a metal target covered by different materials is conducted. The quality of the images is acceptable, which suggests that the imaging system is feasible in detecting hidden metal targets.