Precision glass molding technology for the MODE lens telescope

Nick Brar, Yingying Zhang, Youngsik Kim, Allen Yi, Yuxin Cai, Geon Hee Kim, Thomas D. Milster

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Scopus citations


The primary lens of our multi-order diffractive engineered (MODE) lens telescope combines traditional lens design and a diffractive element to mitigate longitudinal chromatic aberration (LCA). This design uses a 24 cm diameter aperture. In order to make the primary in molded glass, the lens is constructed in 9 segments, 1 radially symmetric center segment, and 8 identical ring segments. A monolithic 24cm aperture MODE lens is not possible at this time, due to limitations of our 14 cm diameter molding cavity. The ring segments each subtend a 45° angular subtense of the ring around the center segment, combining to form a 360° ring around the center segment. Due to the irregular shape of the ring segments and the high precision diffractive surfaces within the design, the lenses are fabricated using precision glass molding (PGM). This presentation considers mold insert design, preform selection, and molding process development. Beyond the overall structure of the molds, the design of the mold insert requires considerations for thermal expansion of the mold and mitigation of adhesion between the mold and the lens using an antiadhesion coating. The preform selection considers both the thermal and optical properties of the glass to be molded and the proper shape of the preform for the easiest material flow during the mold cycle. The general molding process is summarized as heating the preform above the glass transition temperature, applying a force to the mold inserts, and cooling the mold assembly before release.

Original languageEnglish (US)
Title of host publicationOptical Manufacturing and Testing XIV
EditorsDaewook Kim, Heejoo Choi, Heidi Ottevaere, Rolf Rascher
ISBN (Electronic)9781510654266
StatePublished - 2022
EventOptical Manufacturing and Testing XIV 2022 - San Diego, United States
Duration: Aug 22 2022Aug 24 2022

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


ConferenceOptical Manufacturing and Testing XIV 2022
Country/TerritoryUnited States
CitySan Diego


  • Fresnel lens
  • Molded optics
  • diffractive optics
  • large diameter optics

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering

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