AbstractsEngineering

Design and Fabrication of Nonconventional Optical Components by Precision Glass Molding

by Peng He




Institution: The Ohio State University
Department: Industrial and Systems Engineering
Degree: PhD
Year: 2014
Keywords: Engineering; Experiments; Materials Science; Mechanical Engineering; Industrial Engineering; Precision glass molding; Optical fabrication; Mold material; Optical design; Infrared glass molding; Graphene; Coating; Lens fabrication; Micro lens array; Diffractive lens
Record ID: 2036525
Full text PDF: http://rave.ohiolink.edu/etdc/view?acc_num=osu1408548156


Abstract

Precision glass molding is a net-shaping process to fabricate glass optics by replicating optical features from precision molds to glass at elevated temperature. The advantages of precision glass molding over traditional glass lens fabrication methods make it especially suitable for the production of optical components with complicated geometries, such as aspherical lenses, diffractive hybrid lenses, microlens arrays, etc. Despite of these advantages, a number of problems must be solved before this process can be used in industrial applications. The primary goal of this research is to determine the feasibility and performance of nonconventional optical components formed by precision glass molding. This research aimed to investigate glass molding by combing experiments and finite element method (FEM) based numerical simulations. The first step was to develop an integrated compensation solution for both surface deviation and refractive index drop of glass optics. An FEM simulation based on Tool-Narayanaswamy-Moynihan (TNM) model was applied to predict index drop of the molded optical glass. The predicted index value was then used to compensate for the optical design of the lens. Using commercially available general purpose software, ABAQUS, the entire process of glass molding was simulated to calculate the surface deviation from the adjusted lens geometry, which was applied to final mold shape modification. A case study on molding of an aspherical lens was conducted, demonstrating reductions in both geometry and wavefront error by more than 60%.In addition, mold materials and mold fabrications were explored as molds are crucial for fabrication of different freeform optics. The research for the first time demonstrated the use of graphene-coated silicon as an effective and high-performance mold material for precision glass molding. It was shown experimentally that Si-glass adhesion could be completely avoided by using the carbide-bonded graphene coating on Si molds. A glass Fresnel lens and a micro lens arrays using graphene-coated Si molds were molded and tested. Two other novel mold materials, i.e., bulk material glass and copper nickel alloy, were also investigated. Prototypes of optical components were molded using these two materials. The molded lens glass samples were measured by 3D profiler, and the optical performance of the molded lens was also evaluated by lab optical setup. The applications of both of the mold materials were also discussed. Finally, precision glass molding techniques are discussed for two different applications, a diffractive hybrid lens molded by a visible optical glass and a micro lens array molded by infrared (IR) glass. The diffractive hybrid lens was designed to compensate for chromatic aberration. The diffractive efficiency and achromatic focal shift of the molded lens were measured using lab setup, demonstrating a match between the molded lens and optical design. On the other hand, an infrared glass micro lens array and optical gratings were also molded and evaluated using similar…