Development of a low cost high precision fabrication process for glass hybrid aspherical diffractive lenses

Abstract

The hybrid aspherical diffractive singlet achromat design can be used to reduce chromatic aberration in compact optical systems. In this paper, the development of a compression molded, low cost and high precision hybrid diffractive glass lens is described. Specifically, an aspherical diffractive lens designed to compensate for chromatic aberration was fabricated by precision glass molding. The diffractive features are integrated on the aspherical surface to avoid mold alignment during fabrication. As part of the effort to lower manufacturing cost, the diffractive profiles were directly fabricated by single-point diamond turning without polishing. A thin layer of platinum-iridium coating was applied to the mold surfaces to protect the mold inserts from degradation during the molding process. In order to reduce thermal shrinkage error, the hybrid lens was fabricated using a two-step precision molding process on a commercial glass molding machine. The geometry of the molded hybrid aspherical diffractive lens was measured using an optical profilometer and the results demonstrated a match to the design mold profile with a replication error of 0.16% in the radial direction and 6.3% in the axial direction. In addition, an optical metrology system to evaluate the diffraction efficiency and chromatic focal shift was constructed and the measured results showed that the hybrid lenses indeed function as designed.

Measurement and Analysis of the Stepwise Curved Surface of Diffractive Optical Elements by a Constant Speed Confocal Probe

“…Although the surface roughness and tooth height of a DOE can be obtained by measuring with a WLI, the complete and accurate tooth pitch cannot be obtained because of the limitations of the measuring field of view. Therefore, the method of multi-aperture stitching is used to measure the local structural feature information of a DOE, but there is a certain error in measurement data splicing and the efficiency is low [11]. The confocal microscopic measurement method has the ability to perform axial chromatography, which can measure the 3D morphology of the measured sample combined with transverse scanning.…”

Transient microscopic testing method based on deflectometry

“…With the rapid development of optical fabrication, the measurement of surface shape and roughness is required in many fields, including precision engineering [1], micro-manufacturing [2], quality testing and biotechnology [3], etc. Either the contact or non-contact methods can be applied to measure the microscopic surface information.…”

Localized rapid heating process for precision chalcogenide glass molding

“…As early as in the 1980s, precision glass molding was first proposed for fabricating glass optical components with complicated surface geometries [9]. Since its introduction, micro scale glass molding has become a very important manufacturing technology for its low cost as well as high repeatability and reliability of the fabricated parts [4]. Conventional micro glass molding process also requires the heating of entire bulk glass blank above glass transition temperature (T g ) where the glass behaves like a viscoelastic material.…”