The research of relay lens coupling in image intensified camera

Abstract

Image Intensified CCD (ICCD) camera is widely used in the field of low-light-level image detection. The crucial part of ICCD, coupling component, which realizes the image transmitting between the image intensifier and detector, affects the final performance of the ICCD camera significantly. There are two means of coupling: relay lens and optical fiber taper (OFT). OFT has the merits of small volume and relatively high coupling efficiency, therefore it is commonly used in the portable devices or applications with less precision demands. However, relay lens turns out to be a better solution other than OFT for the applications with no volume and weight restrictions, since it provides higher resolution, perfect image plane uniformity and manufacture flexibility. In this paper, we discuss a methodology of high performance relay lens design and based on the method a solid design is proposed. There are three major merits of the lens design. Firstly, the lens has large object space numerical aperture and thus the coupling efficiency reaches 5% at the magnification of 0.25. Secondly, the lens is telecentric in both sides of object space and image space, this feature guarantees uniform light collection over the field of view and uniform light receiving on the detector plane. Finally, the design can be conveniently optimized to meet the needs of different type of image intensifier. Moreover, the paper presents a prototype ICCD camera and a series of imaging experiment as well. The experiment results prove the validity of the foregoing analysis and optical design.