Development of a rapid manufacturing process for concave and convex lens arrays

This paper reports a rapid manufacturing process for the production of concave and convex lens arrays on the polymer substrate. In this method, many small steel balls with highly polished surfaces were placed in a rectangular cavity to form a closely packed small steel ball array. Then, a polymer substrate (PMMA sheet) was placed on top of the small steel ball array, and the stack of the PMMA sheet and the small steel ball array was placed in a hot embossing machine. During the hot embossing process operation, a concave lens array pattern is directly fabricated onto a polymer substrate. In addition, the diameter and depth of the concave lens array can be changed and controlled by adjusting the processing conditions of the hot embossing process. Thus, concave lens arrays with different dimension can be fabricated. Next, the polymer substrate with concave lens array pattern can be used as a mold for rapid replication of polymer convex lens array using vacuum-assisted UV molding process. In this way, various concave and convex lens arrays can be rapid fabricated with high throughput and low cost