Precision glass molding: Toward an optimal fabrication of optical lenses

Abstract

It is costly and time consuming to use machining processes, such as grinding, polishing and lapping, to produce optical glass lenses with complex features. Precision glass molding (PGM) has thus been developed to realize an efficient manufacture of such optical components in a single step. However, PGM faces various technical challenges. For example, a PGM process must be carried out within the super-cooled region of optical glass above its glass transition temperature, in which the material has an unstable non-equilibrium structure. Within a narrow window of allowable temperature variation, the glass viscosity can change from 10 5 to 10 12 Pa$s due to the kinetic fragility of the super-cooled liquid. This makes a PGM process sensitive to its molding temperature. In addition, because of the structural relaxation in this temperature window, the atomic structure that governs the material properties is strongly dependent on time and thermal history. Such complexity often leads to residual stresses and shape distortion in a lens molded, causing unexpected changes in density and refractive index. This review will discuss some of the central issues in PGM processes and provide a method based on a manufacturing chain consideration from mold material selection, property and deformation characterization of optical glass to process optimization. The realization of such optimization is a necessary step for the Industry 4.0 of PGM.

A Comprehensive Review of Micro/Nano Precision Glass Molding Molds and Their Fabrication Methods

“…To date, several comprehensive reviews have been reported that summarize the key issues associated with the precision glass molding process [ 29 ], which are issues related to the replication of non-spherical glass lenses [ 30 ], theoretical and technological advancement of current glass molding [ 31 ], chalcogenide glass for infrared (IR) optics [ 32 ], and the manufacturing of optical micro-components via glass molding [ 33 ]. However, despite the mold being an indispensable component of micro/nano glass molding, there has been no review of the fabrication of these molds.…”

Tribological Analysis of Contacts Between Glass and Tungsten Carbide Near the Glass Transition Temperature

“…Measuring friction of contacts formed between solids and glasses at temperatures close to the glass transition is a problem of both fundamental scientific interest and technological relevance. Concerning technological applications, understanding the tribological mechanisms is particularly relevant for precision glass molding (PGM) [1][2][3][4], where optical components are formed in a one-step process from heated glass by using molds made typically from tungsten carbide (WC) with a precisely machined and smooth surface. Since the production of the pressing tools, i.e., the molds, is an expensive and complex process, their lifetime ultimately determines the economic viability of the method.…”

Moldless Printing of Silicone Lenses with Embedded Nanostructured Optical Filters

“…Three thousand years after its first appearance, commercial optical lenses are still prepared by either mechanical polishing or molding of rigid materials, such as glass [6] or plastics [7], and optical microscopes still rely on the use of lenses as a light collection element (for reflected, emitted, and/or diffracted light) and discrete optical filters for light manipulation (e.g. wavelength selection and/or intensity modulation) [8].…”