This PDF file contains the front matter associated with SPIE Proceedings Volume 12219, including the Title Page, Copyright information, Table of Contents, and Conference Committee Page.

Design for manufacturing (DFM) for precision glass molding (PGM) requires a detailed understanding of the molding process and the process used to manufacture the molds. PGM lenses and molds require a transition segment between the optical surface and the flat or flange of the lens/mold. These blend radii provide tool relief, reduce high stress concentrations, reduce load requirements, extend mold life, and improve overall moldability. The methods for designing these radii are reviewed and guidance for proper DFM for PGM is provided.

Precision Glass Molding (PGM) is a replicative technology to manufacture glass lenses with complex geometries such as aspheres, freeform-optics or lens arrays. During the PGM process, a glass preform is heated until the viscous state and afterwards pressed into the desired shape using two high-precise molds. This process enables the direct and efficient manufacture of high shape accuracy and surface quality optics without any mechanic post-processing step. The efficiency of the PGM process depends primarily on the lifetime of the high-precision molds made of cemented tungsten carbide. During each molding cycle, the molds have to withstand severe thermo-chemical and thermo-mechanical loads. Using protective coatings, the lifetime of the molds can be increased. In this study, the performances of a diamond-like carbon (DLC) and a precious metal alloy coating, namely PtIr, were evaluated in an industrial glass molding machine. The degradation mechanisms of the coatings were analyzed using surface characterization such as scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). At this, phenomena such as glass adhesion and coating disintegration were observed.

Glass press molding of optical lenses is a time-consuming process due to the time to heat and cool the glass material. Cycle times can range from 15 to 30 minutes with over 80% of the cycle time consumed in heating and cooling. The heating process is limited by the heater capacity, while the cooling process is limited by the maximum cooling rate required to achieve the desired minimum residual stress or birefringence. Typically, glass press molding machines utilize radiant heating elements; therefore, the heating power is limited by the exposure of the mold and glass to the heating elements. Also, temperature gradients in the mirror are difficult to control by radiant heating. This paper presents a new glass press molding machine design that utilizes two heating element types with several independently controlled zones, allowing for higher heating capacity and better control of thermal gradients. The cooling rate during gradual cooling is also controlled to a finer tolerance through nitrogen gas cooling combined with the independently controlled heating zones. Glass lenses pressed with the new process exhibit a shorter cycle time and reduced birefringence.

Manufacturing technology is driven by ever increasing demands of costs, quality and lead time. For many existing industries, digitization is key to obtain these goals in the future. In terms of optics production, it is rather a research topic. Meanwhile, the so called »Biological Transformation« is said to be the subsequent industrial revolution. This paper will explain this development and translate it to the optics production. Two examples of biologically transformed production scenarios will be presented. The presentation concludes with an assessment, whether »Biological Transformation« can deliver a substantial innovation push to optics manufacturing and glass molding in particular.

Tungsten carbide is a material of interest to the optical molding industry because of its suitable thermal properties in molding at higher temperatures. Tungsten carbide is typically ground and polished as tool wear from conventional machining is too high to be feasible. Laser assisted machining developed through Micro-LAM has allowed direct machinability of this material. A machinability study was performed on five grades of tungsten carbide that have been specially developed for glass lens molds. The primary difference between the grades studied is the grain size. With advances in material technology, there is an ability to provide finer grain structures in binderless alloys of tungsten carbide. Standardized trials were then performed across the different grades to evaluate machinability and surface roughness using Laser Assisted Machining (LAM) on a Single Point Diamond Turning (SPDT) platform. The trials proved that there is a strong dependence and correlation of grain size versus final achievable surface finish after LAM turning. Larger grain materials have larger voids and gaps which may cause larger pull outs. These voids then must be polished in post-processing to get beneath the sub-surface damage which is a function of the void depth. Laser assisted machining of fine grain tungsten carbide can achieve a mirror-like surface finish suitable for optical molding applications with minimal post-polishing. Using this technology allows for producing tungsten carbide molds through a more deterministic process. Also, given the range of diamond tool sizes, this method is suitable for complex geometries such as those used in the molding of collimation optics for 5G applications or biomedical applications such as endoscopes.

Maintaining the fidelity during mass production of nanostructures over large surface areas poses several challenges. Thin polymer optic components are susceptible to warping, birefringence, and errors in nanostructure form and periodicity. These issues can vary across the entirety of the surface, much more than in smaller injection molded parts. We discuss some of these challenges, their effects on the performance of the nanostructures, and some methods for mitigation.

Transparent polymers play a major role as materials for precision optics and optoelectronics. Transmissive optical surfaces need antireflection properties to avoid reflection losses and ghost images. As an alternative to common AR interference coatings, AR-nanostructures can be etched directly into the polymer surfaces and another structure can be added on top. The double-nanostructured surfaces provide low reflectance in a broad wavelength range for normal and oblique light incidence. Excellent AR-properties combined with a high thermal stability are demonstrated on imprinted epoxy-based micro-lenses.

A compact spectrometer is designed for volume production using a monomer material. The design exemplifies the strengths of polymer optics, such as low cost, low weight, high volume production, and integration of functional mechanical features. The challenges of the design using polymer optics for spectrometer applications will be discussed.

The additive manufacture of polymer optical elements has the promise of reducing component weight, providing new design capabilities, and enhanced performance for a wide variety of military and commercial optical systems. This paper reviews progress in the development of 3d printed Gradient Index (GRIN) lenses and optical phase masks. The 3d printing process uses a modified commercial inkjet printer and UV curable polymers that have specific nanoparticles added to them to modulate the index of refraction. Complex optical phase masks for the generation of Airy laser beams and polymer GRIN lenses to replace conventional glass lenses used in a telescope or riflescope are created. The generation and propagation of Airy beams using these polymer generated optical phase masks has been investigated and analyzed through experimentation, simulations, and comparison with recent theoretical predictions. Airy beams have been generated using the conventional approach using a spatial light modulator and compared to the 3d printed optical phase masks. The maximum non-diffracting propagation distance of an aperture truncated Airy beam was experimentally measured. The results show that the maximum non-diffracting propagation distance of a laboratory generated Airy beam is proportional to x0 2, the Airy beam waist size squared. The size of the Gaussian envelope beam has a weaker effect on the Airy beam propagation distance. The experimental results were compared with current theoretical models. A set of 1 inch diameter 100 mm focal length polymer GRIN lenses have been made using 3d printing. Transmission and modulation transfer function (MTF) results for the lenses is reported.

We propose and experimentally demonstrate an optical fiber-based Fabry-Perot (FP) sensor for acetone vapor sensing. The FP cavity is formed with Polystyrene (PS) deposited at the end facet of a cleaved fiber. The interference spectrum is generated due to reflections from the fiber-polystyrene and polystyrene-air interfaces. The sensing mechanism of the sensor relies on the change in optical path length due to the interaction of acetone with the sensing cavity which ultimately changes the phase-matching condition of interference. Pronounced change in the interferometer spectral response is observed with respect to the change in concentration of acetone vapor. The developed sensor can be used in the application of breath VOC monitoring.

Improvements in the design and manufacture of polymer layered gradient index optics (LGRIN) are described. As a demonstration of the manufacturing improvements, the design and performance of a 22 mm diameter, 80 mm focal length f/4 achromatic LGRIN singlet is presented. This lens demonstrates a step-change in LGRIN quality. For the first time, radially asymmetric aberrations within a curved LGRIN interface geometry are not the leading-order contribution to the performance gap between as-designed and as-manufactured performance.

The growing demands of optical systems lead to increasingly complex aspheres and freeforms. When measuring those, one not only has to consider the form error of single optical surfaces but also the geometrical relation of front and backside to each other, as well as of mechanical references to the optical axis. A suitable metrology solution to cover all those features is crucial to improve overall performance of molded optics. An established measurement system in asphere production, which is a promising approach in high precision freeform manufacturing as-well, is given by a scanning point interferometer basing on a multi-wavelength approach. The scanning principle enables for a great flexibility, reduces setup time and costs, and has almost no limitations in spherical departure. Due to the absolute measurement capability, it is beneficial for segmented and interrupted surfaces, which are common apertures of modern application’s optical elements. Basing on the before-mentioned multi-wavelength scanning approach, several new measurement options are available that enable relational measurements which correlate the lens front surface to its backside, as well as several fiducials. These new measurement options can be applied to molds as well as lenses of different diameters, materials, surface forms, and center thicknesses. A new feature even allows measurements through the lens which helps to increases throughput. This contribution gives a general overview of challenges when measuring complex surfaces, with a special focus on relational datum parameters and correlation of both sides of a lens.

Latest advancements in XR devices or the application of autonomous driving technology, the number of complicated freeform optical design components are increasing. And the demand for accurate measurement and evaluation is invaluable. In addition to standard form evaluation, there is an increasing demand for surface to surface decenter evaluation for optical characteristics, I.E.: bi-aspherical surfaces. We believe a standardized evaluation solution is lacking in the market. We are proposing a method for axial center evaluation between lens surfaces by synthesizing coordinate system using three reference spheres.In this research, we have developed decenter and rotational misalignment evaluation method for freeform bi-aspheric optical components by the Ultrahigh Accurate 3-D Profilometer (UA3P) and by coordinate system synthesis method. Using a fixture that can evaluate both bi-aspheric surfaces, the rotational deviation was calculated between outline standard and the actual surfaces measurements from the UA3P. The result of regression line inter free-form rotational deviation against the mechanical rotational deviation has a slope of 0.9737 and a coefficient of determination of 0.9995.

Today’s high-power illumination is mainly based on LED technology. Continuing trends are increased luminous power on decreasing emitting surfaces. This leads to growing technical requirements of optics that are useable for modern LED systems: Firstly, the increasing power densities require transparent materials that are durable when exposed to high temperatures or luminous fluxes. Here, polymeric materials as polycarbonate, PMMA or silicone quickly exceed their material limits when used in such conditions. Secondly, the smaller LED size allow for the design of smaller optical solutions. This means, the size of luminaires can be shrunk without any disadvantage for the optical performance. This comes with increasing requirements for system accuracy and geometrical deviations of the optics. Glass, shaped with modern manufacturing techniques, is a promising solution for these requirements. In this paper, we show two different approaches for automotive front lights. The first is non-isothermal glass molding of aspherical lenses. This method allows for the fast manufacturing of precision glass lenses including all structures needed for accurate mounting. These lenses can be used in imaging systems for modern front lights. The second method covers glass injection molding of complex 3D-optics. Here, tiny light guide optics are used for typical automotive front light distributions.

An introduction to controlled viscosity molding, a low stress process that enables high precision molding well suited for the demanding surface form and optical performance requirements of modern polymer optics.

Several types of polymer viewing screens for imaging thermal infrared scenes have been studied, both experimentally and theoretically. The best candidates will be used to evaluate the quality of polymer thermal imaging optics in a subsequent paper.

We demonstrated optical elements based on the sulfur copolymers (poly(S-r-NBD2) termed Polycalc) for the IR optics applications. The high refractive index, excellent transparency in the IR wavelength region, and good moldability enable compact lens packaging and freeform designs. The advantages of organic-based polymers such as the lightweight, ease of fabrication, and cost-effectiveness are suitable for high volume commercialization. The chemical stability, water resistance and CTE of Polycalc are superior to conventional optical polymers. The demonstrated heat resistance after cycling to typical solder reflow temperatures shows that the Polycalc lens is feasible for wafer-level IR optics module including image sensors integrated with IC packaging.