The paper describes a monolithically integrated planar microlens array and its applications. An ion exchange technology is applied to realize the microlens array with diameters of 10 - 1000 pm and N.A. of 0.25. Applications to optical fiber communications, combinations with CCD arrays and optical computing are demonstrated.
"Integrated Planar Microlens And Its Applications", Proc. SPIE 0898, Miniature Optics and Lasers, (2 June 1988); doi: 10.1117/12.944554; https://doi.org/10.1117/12.944554