As manufacturing capabilities have developed, the potential to create complex geometries for optical elements of a variety of materials has become a reality. Under these conditions, freeform optical components have become more prevalent in the industry, and have allowed a new class of optical systems to be engineered. In the past, freeforms have commonly been described parametrically for optimization, which in some cases limits their flexibility and utility. In this paper we demonstrate a novel freeform design methodology which uses a grid-based sag definition to serve as an alternative to polynomial coefficient optimization. The OpticStudio TrueFreeForm model allows direct optimization of sag values at grid points across the surface to enable spatially-selective surface sag optimization. Here, a case study is presented on the effectiveness of TrueFreeForm optimization in the design of freeform optical surfaces for use in modern augmented reality/virtual reality (AR/VR) optical systems. We demonstrate the flexibility and advantages of grid sag optimization and discuss key implementation considerations in the context of a freeform wedge prism system as might be found in an AR headset. In particular we demonstrate, via sub-aperture grid sag optimization, the integration of an eye-tracking subsystem into the AR wedge prism. An average MTF of 0.446 at 40 lp/mm is achieved in the user pupil imaging portion of the eye-tracking system, while introducing no degradation in the nominal performance of the AR visual display system.
In this work, we discuss grid-based surface optimization in the OpticStudio lens design software. This new approach allows flexibility in designing freeform optical components that is not possible with traditional surface types. The system we focus on is a corrector plate with the rear surface specified by a variable grid sag surface. The goal of the corrector plate is to correct for wavefront error introduced by a Zernike phase surface. We optimize the sag values of the grid points to correct for this wavefront error and study the resulting behavior as the number of grid points are varied. We test grids from 5x5 to 25x25 and report the scaling of total computation time and improvement in wavefront error. We describe several findings, such as the importance of constraints on the grid variables and techniques that improve the calculation efficiency.
Our new Contrast Optimization technique allows for robust and efficient optimization on the system MTF at a given spatial frequency. The method minimizes the wavefront differences between pairs of rays separated by a pupil shift corresponding to the targeted spatial frequency, which maximizes the MTF. Further computational efficiency is achieved by using Gaussian Quadrature to determine the pattern of rays sampled. Examples are given to demonstrate the advantages of the technique.
Zemax has developed an XML schema for the distribution of singlet lens specifications based on the ISO 10110 standard. In OpticStudio 15, this kind of XML data can be exported from the ISO Element Drawing analysis. The data file is then used in a feature that automates exchange of lens data between designer and manufacturer, the Cost Estimator. This Cost Estimator feature submits the XML data to various manufacturers to obtain cost estimates for prototype lens production. The workflow centered on the XML data exchange facilitates rapid cost estimate retrieval and eliminates the need for redundant manual data entry. <p> </p>The XML Schema Definition (XSD) for the XML format can be used with Microsoft developer tools to automatically create .NET classes to serialize and deserialize the singlet lens data to/from XML files. The format provides flexible unit specification for most parameters. Choosing XML as the basis for the file format has provided several benefits, such as the above mentioned automated serialization capabilities in .NET, a human-readable text-based format, and ready support for consumption by web services.