An axicon structured lens is designed and its properties of long focal depth is demonstrated. The phase function of the axicon structured lens is constructed according to the properties of nondiffractive Bessel beam with uniform-intensity. Based on the relationship of the side length of the square hole and the phase retardation, the required phase distribution of the axicon structured lens with a long focal depth in a metallic film can be determined. To verify the feasibility of the method, an axicon structured lens with focal length 1000 mm, a focal depth larger than 20 mm was designed and the intensity distribution of far field was calculated. The results show that the focal depth is 25 mm which is nearly 7 times extended with nearly diffraction-limited image quality. (C) 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.3590723]
