Influences on the Fabrication of Diffractive Optical Elements by Injection Compression Molding

Abstract

Abstract:Polymer optics are widely used in various applications, replacing traditional glass lenses. The ability to create free-form and micro-structured optics, as well as fast replication, gives them major advantages over traditional glass lenses. However, the fabrication of complex optical components requires full process control and understanding of influencing factors on the quality of the polymer optical parts. In this work, a curved diffractive optical element (DOE) is fabricated using injection compression molding. Different gate designs were evaluated and the movement of the compression stamper was optimized to obtain good filling behavior. The process stability was analyzed and improved by controlling the melt temperature precisely. Finally, the molding parameters were optimized, focusing on the mold temperature, melt temperature and compression force. Curved diffractive optical elements were replicated with feature sizes of 1.6 µm. The experiments showed that all aspects of the molding process have to be controlled perfectly to produce complex polymer optics. High mold temperatures and compression force are necessary to replicate micro-structured features. The work presents a broad investigation and description of the fabrication process and their influences.

Manufacturing Signatures of Injection Molding and Injection Compression Molding for Micro-Structured Polymer Fresnel Lens Production

“…In the case of micro- or nano-structures replicated by ICM, a significant effect on the replication is also given by the mold temperature, as proved by Rytka et al, Nagato et al, and Chuan-Zhen et al [25,26,27]. The effective local mold temperature also supports different replication quality conditions in dependence on the cavity design and the polymer melt flow [28,29,30]. Understanding the effective replication behavior of surface grooves is of paramount importance, to ensure the designed functionality of polymer optics, such as Fresnel lenses.…”

High Concentration Photovoltaics (HCPV) with Diffractive Secondary Optical Elements

“…Typically, the zone depth of the diffractive profile is twice that of the wavelength, and setting a minimum zone width constraint ensures an aspect ratio of about 1:1, to ensure manufacturability. Sub-micron features have been demonstrated with glass etching or replication of optical plastics [27][28][29]. The POE lens was modeled as an ideal refractive Fresnel lens, and this is a valid approximation for lenses with fine grooves.…”

Review on Fabrication Technologies for Optical Mold Inserts

“…The combination of lenses with micro-structured features can be used to increase their performance, reduce the weight of optical systems, correct aberrations, and shape beams. Examples of micro-structures used in polymer optics are micro-lens arrays [5], diffractive optical elements [6], Fresnel lenses [7], prism arrays [8] and blazed structures [9]. Examples of applications of micro-structured optical components are concentration structures for solar panels using micro-lens arrays [10] or Fresnel lenses [11], beam shaping and homogenization [12,13], measurement systems [14] and sensors [15,16].…”