Phase-Type Diffractive Imaging Lens with High Diffraction Efficiency and High Error Tolerance

Diffractive lens can realize high-resolution imaging with large aperture and light weight. Conventional amplitude-tpye diffractive lens has extremely low diffraction efficiency, and therefore, it can only work in the situation under extremely strong illumination, such as observation of the sun. Binary diffractive lens has low diffraction efficiency and high sensitivity to fabrication error, which significantly limits its applications in practice. Here, a phase-type diffractive lens with continuous parabolic ring-shaped microstructures (PDLCPRM) is designed. The surface of PDLCPRM is continuous parabolic ring-shaped microstructures, which makes its diffraction efficiency extremely high. Experimental fabrication of the proposed PDLCPRM was performed using the laser direct writing of grey-scale patterns for a PDLCPRM of diameter of 10 mm, a focal length of 100 mm. Experimental results show that the imaging quality of the PDLCPRM close to the diffraction limit and the diffraction efficiency of the PDLCPRM reaches 82%, which are in significant contrast to the conventional amplitude-tpye diffractive lens and binary diffractive lens. Furthermore, the PDLCPRM has high tolerance of height error, which reduces significantly the difficulty of fabrication. PDLCPRM has great potentials in applications of large space telescope and other imaging systems.