Advances and challenges in optical mold polishing technology

The manufacturing of optical components is typically carried out using direct machining or mold processing. Compared with direct machining, mold processing offers superior efficiency and shape consistency, providing irreplaceable advantages, particularly in the mass production of microlens arrays and complex shaped optical components. Materials such as silicon carbide and tungsten carbide are widely used in the fabrication of optical molds because of their excellent material properties, including high temperature resistance, exceptional wear resistance, and thermal shock resistance. To ensure that optical components meet high standards of shape accuracy, transparency, and ultrasmooth, nearly flawless surface quality, optical molds must meet extremely stringent demands, including nanometer level shape accuracy and surface roughness. However, these materials present significant challenges in processing because of their high hardness, brittleness, and chemical stability, making them a major challenge in both academia and industry. This study systematically reviews the development history of optical molds, the performance characteristics of commonly used materials, and the latest advancements in manufacturing technologies, with a particular focus on ultra-precision polishing techniques for optical molds. This paper classifies polishing techniques into three categories according to the machining method used: contact, non-contact, and composite ultra-precision polishing. It thoroughly explores their machining principles, equipment structures, material removal mechanisms, and improvements, while analyzing the advantages, disadvantages, and applicability of each technique. And then, the current technical bottlenecks in ultra-precision polishing technology for optical molds, including the limitations of improving machining accuracy, the feasibility of manufacturing complex structural molds, and the trade-offs between production efficiency and cost, are summarized. It also identifies key areas that need to be addressed in future research. • The background of optical molds is comprehensively investigated. • Ultra-precision polishing technologies for optical molds are categorized into contact, non-contact, and composite types. • The working principles of each technology are described in detail within each category, along with their polishing performance. • A comparative analysis of the advantages and disadvantages of each technology is made, and the application scenarios are indicated. • The future research directions of ultra-precision polishing for optical molds are summarized.