[3] Bally G V, Schmidthaus W, Sakowski H, et al. Gradient-index optical system in holographic endoscopy[J]. Appl. Opt, 1984, 23(11):1725-1729.

[4] Nishi H, Ichikawa H, Toyama M, et al. Gradient-index objective for the compact disk system[J]. Appl. Opt, 1986, 25(19):3340-3344.

[5] Krishna K S R, Sharma A. Chromatic aberrations of radial gradient-index lenses[J]. I. Theory. Appl. Opt, 1996, 35(7):1032-1036.

[6] Mitsuhashi Y. Selfoc lenses: applications in DWDM and optical data links[J]. SPIE 1999, 3666: 246-251.

[7] Koizumi K. Gradient-index micro-optic glasses based on ion-exchange techniques[J]. SPIE, 1989, 1128: 74-79.

[8] Fujii K, Ogi S, Akazawa N. Gradient-index rod lens with a high acceptance angle for color use by Na+ for Li+ exchange[J].Appl. Opt, 1994,33(34):8087-8093.

[9] Stepien R, Kociszewski L, Pysz D. Technological problems in manufacturing glass for GRIN rod lens[J]. SPIE, 1996, 2943: 60-68.