Polarization ray tracing in anisotropic optically active media

Polarization ray tracing, which consist of several extensions to geometrical ray tracing, calculates the evolution of polarization states along ray paths and determines the intrinsic polarization properties, such as diattenuation and retardance, associated with ray paths. This paper compares the suitability of the Jones, Mueller, and a three-dimensional polarization ray tracing calculi, examining the issues of local versus global coordinates, amplitude versus phase representations, inclusion of the wavefront aberration function, partially polarized light, measurements of images by polarimeters, and diffraction image formation by low and high numerical aperture beams.

A polarization analysis capability based upon polarization raytracing is described. The polarization ray trace can model the effects of various interface types including metallic reflectors and multilayer coatings. Idealized retarders and linear polarizers can also be incorporated into the model of an optical system. Information obtained during the polarization ray trace is used to compute image quality metrics such as the point-spread function and the modulation transfer function. In addition, the polarization state of the electric field at any point along a ray path can be found. The utility of the polarization raytracing approach is demonstrated by using the CODE V optical design program, which incorporates the modeling features described here, to perform an analysis of selected optical systems, including a corner-cube reflector, a folded beam expander, an imaging radiometer and a high numerical aperture objective. 1. INTRODUCTION The ability to accurately model the polarization effects in optical systems can be an important tool for assessing the performance of certain optical systems. From the standpoint of the optical designer who needs to determine whether or not a design meets specifications, the ideal tool for such an analysis task should provide information about how polarization effects can alter those performance metrics that he is familiar with, i.e. those that are typically used to specify design requirements for an optical system. Furthermore, such an analysis capability is most useful when it is integrated into the optical design/analysis software that he is using.This paper will describe a polarization analysis capability that enables the optical designer to model most of the effects that lead to polarization dependent behavior in conventional optical systems. The capability is primarily intended for analysis tasks rather than synthesis (i.e. design) tasks. At this time, though design techniques for reducing polarization effects do exist,1 they have not yet been fully integrated into optical design programs.

Modern optical design and simulation software, while both powerful and feature-rich, requires significant training investment for effective use, even for simple optical design tasks. By contrast, software for two-dimensional (2D) non-sequential raytracing, while sufficient for many optical design tasks and popular for educational purposes, has remained without the benefit of mature computer-aided design (CAD) technologies that are now a key feature of software dedicated to three-dimensional (3D) optical design. To overcome this limitation, we introduce M-TRACE—an open source toolkit for non-sequential 2D raytracing with scripting-based customization and animation capabilities implemented in MATLAB. This toolkit allows users to specify optical designs using tools compatible with free-form 2D illustration via scalable vector graphics (SVG), analogous to the integration of 3D CAD technologies with enterprise optical design software. The intuitive and precise drawing features of SVG illustration software (e.g., Adobe Illustrator, Inkscape) allow for a straightforward means for the creation of system designs. We intend M-TRACE to complement the spectrum of available optical design software for research, development, and education, specifically targeting design cases requiring rich visualization and/or rapid exploration.

3D imaging of solid targets using plenoptic cameras has been extensively explored and optimized over the years. Unfortunately, these imaging techniques, typically making use of triangulation methods and contrast recognition for depth estimation, lose their validity when imaging translucent media. For these cases, tomographic reconstruction has been shown to be a promising avenue for recovering the 3D shape of a translucent volume. Apart from the tomographic reconstruction algorithm itself, the accuracy of a reconstructed solution depends on the set of measured projections and on the system matrix. A proper determination of the system matrix is key as its elements describe the weighted contribution of a voxel in object space to one in image space; however, computing the matrix elements can consist of an arduous task as it requires a priori knowledge of the imaging system and precise modeling of the physical properties of the acquisition process. In this work, we present how an optical design software can be used to generate such system matrices. Compared with approximation methods involving paraxial ray tracing, the proposed method offers the main advantage of real ray tracing, in which the computed weighted contributions intrinsically account for optical aberrations in the imaging system. Physical properties of light propagation within the translucent medium can also be taken into account when using non-sequential modes. Using a ray tracing software thus offers great flexibility in designing plenoptic imaging systems used with 3D tomographic reconstruction techniques.

New polarization methods allow the ray tracing simulation of polarization critical components, including multilayer biaxial films, anisotropic and gyrotropic crystals, electro-optical, and magneto-optical materials bring many new challenges.

Classical triangulation sensors exhibit an orientation depend signal if the scattering properties of the work-piece are not symmetrical like at curved surface locations. This problem is avoided by rotational symmetric triangulation sensors. Due to this attractive property in a lot of applications such a sensor was introduced very recently on the market. This sensor is based on refractive optics and a special PSD detector, both custom made resulting in high costs. Additionally, the existing optical design approach does not offer an optical layout to start with, thus a good amount of trial and error is required and non-optimal solutions are probable. Therefore, there is great interest for a clear optical design strategy that results in layouts that are suitable also to use low cost commercial available detectors, such as CCD or CMOS image detectors. In this paper such a design procedure is presented for optical designs that use reflecting optical surfaces. Several solutions are depicted and discussed. The designs are not only attractive from the optical point of view and from detector considerations, but also from opto-mechanical design issues. For example designs with only one opto-mechanical part are possible. The resulting optical designs consist of aspherical surfaces which are obtained directly by using only some new relations of first order optics for off-axis objects. The designs are validated by exact ray tracing. These ray tracing results show already very good performance. Nevertheless, it was possible to further optimize the optical designs very efficiently using ray tracing software, thus yielding improved optical properties.

A comprehensive education of optical engineers is of paramount importance to the development of the industry. While optical sciences and engineering curricula are set up to teach theoretical concepts comprehensively, there appears to be a lack of required coursework that teaches students how to use industry-standard software that they will inevitably use in their careers. The Practical Optics Workshop (POW) is an initiative at the University of Arizona’s Wyant College of Optical Sciences to support the education of students that use optical design software. POW’s aim is to bridge the gap between the theory of optical system design and the problems the optical engineers of the future will face daily. POW has principally engaged students through short workshop sessions and optical design problems through inquiry-based learning activities. However, during the COVID-19 pandemic new activities have been designed to support self-paced and virtual learning to ensure the accessibility of Optical Design software education. We present the status of POW’s current initiatives and how they have impacted student learning, as well as the design of future initiatives that POW is developing for a self-paced curriculum.

The traditional method of designing the initial configuration of off-axis reflective optical system is to first obtain the initial configuration of coaxial reflective optical system, and then achieve the unobscured design with an offset aperture stop or a biased input field, or both. Because the aberration distribution of coaxial reflective optical system is not applicable to the off-axis reflective optical system, the obtained unobscured off-axis reflective optical system has large aberration, and the unobscured design process is complicated. In this paper we present a method of designing an initial configuration of off-axis reflective optical system based on vector aberration theory. With this design method, a good unobscured initial configuration of off-axis reflective optical system can be directly obtained by using an offset aperture stop or a biased input field, or both. Based on the vector aberration theory and gaussian brackets, the third-order aberration coefficient is derived for off-axis reflective optical system. Initial configuration performance is important for optical design, especially for the complicated optical system design. The selection of initial configuration highly affects the final system imaging performance, fabrication difficulty and alignment difficulty. An error function is established to evaluate the performance of off-axis reflective optical system, and it consists of aberration coefficients and other constraints. The genetic algorithm is a highly parallel, random and adaptive global optimization algorithm. To obtain a good initial configuration for the off-axis reflective optical system, the genetic algorithm is used to search for the initial configuration with minimum residual aberration. This method can obtain a good initial configuration of off-axis reflective optical system for further optimization. The benefit of this design method is demonstrated by designing an off-axis three-mirror optical system. For the focal plane array, a long-wave infrared off-axis three-mirror optical system is designed. A good initial configuration is obtained with the proposed method, which achieves the unobscured design by using an offset aperture stop and a biased input field. To improve the performance of initial configuration, the obtained initial configuration is optimized with the optical design software. The designed optical system has good imaging quality. As the mirrors are free from the tilts and decenters, the designed optical system is aligned easily.

This chapter will introduce the reader to the process of lens design and image evaluation. While not everyone working in the field of optical engineering will be called on to execute detailed lens designs, a basic understanding of the procedures involved and their limitations will be helpful to all. In the area of image evaluation, some degree of familiarity with the various methods employed will allow the optical engineer to more effectively specify required performance, and later, to determine whether those levels of performance have been met by the designer. This chapter is particularly relevant when we consider the state of the computer and optical software field today. The days when access to these tools of lens design was limited to a very carefully chosen few are gone forever. In Chapter 5 we introduced the OSLO and OSLO-EDU optical design software packages, pointing out their ready availability and ease of use in generating and evaluating certain (relatively simple) optical systems. This chapter will expand into the use of a more sophisticated software package (OSLO Premium Edition, Rev. 6.1), outlining its use in generating detailed lens design solutions for a variety of specific problems. The field of optical design software is broad and very dynamic. There are a number of very fine software packages to choose from and they are all (including OSLO) constantly updated to reflect the state of the art.

Zernike polynomials are universal in optical modeling and testing of wavefronts; however, their polynomial behavior can cause a misinterpretation of individual aberrations. Wavefront profiles described by Zernike polynomials contain multiple terms with different orders of pupil radius (ρ). Zernike polynomials are a sum of high and low orders of ρ to minimize the RMS wavefront error and to preserve orthogonality. Since the low-order polynomials are still contained in the net Zernike sum, there is redundancy in individual monomials. Monomial aberrations, also known as Seidel or primary aberrations, are useful in studying an optical design's complexity, alignment, and field behavior. Zernike polynomial aberrations reported by optical design software are not indicative of individual (monomial) aberrations in wide field of view designs since the low-order polynomials are contaminated by higher order terms. An aberration node is the field location where an individual (monomial) aberration is zero. In this paper, a matrix method is shown to calculate the individual monomial aberrations given the set of Zernike polynomials. Monomial aberrations plotted as a function of field angle (H) indicate the field order (Hn) and the location of true aberration nodes. Contrarily, Zernike polynomial versus field (ZvF) plots can indicate false aberration nodes, due to the polynomial mixing of high- and low-order terms. Accurate knowledge of the monomial aberration nodes, converted from Zernike polynomials, provides the link between a ray-trace model or lab wavefront measurement and nodal aberration theory (NAT). This method is applied to two different optical designs: (1) 120° circular FOV fish-eye lens and (2) 120∘×4∘ rectangular FOV, off-axis, freeform four-mirror design.

Polarization aberrations exist in almost all astronomical telescopes. Polarization aberrations would bring about asymmetric apodization in the exit pupil, leading to asymmetric PSFs. The shape of PSFs is critical to telescopes that are used to detect weak gravitational lensing (WGL) in the universe. In this paper, polarization aberrations and their connections with PSF ellipticity in an unobscured off-axis space telescope are analyzed. Together with the Jones pupil, cumulative diattenuation and retardance maps of the telescope are obtained via polarization ray tracing. Due to asymmetric apodization caused by polarization aberrations, the ellipticities of all four PSF components are found to be greater than zero. The PSF ellipticity of the telescope over the full FOV is obtained. Results show that polarization aberrations change PSF ellipticity in different degrees at different FOVs. The maximum variance of PSF ellipticity induced by polarization aberrations is 7.5e-3 and the average value is 2.7e-3. In addition, interpolation errors of PSF ellipticity would also be affected by polarization aberrations. It is found that there are 405 FOV points (about 4% of all FOV points involved in the calculations) whose variances of interpolation errors caused by polarization aberrations are greater than 1.4e-4. According to the results shown in this paper, polarization aberrations of telescopes play a significant role in WGL measurements.

Cellular automata ray tracing in flow field near the optical window of the optical dome

Temperature variation not only results in changes in refractive index, radius, thickness, and air space, but also leads to surface deformation due to the mismatch in thermal expansion coefficients between glass and mechanical materials. However, existing passive athermal optical design methods cannot optimize thermal-induced surface deformation, and optimization methods usually focus on structural optimization or thermal control rather than optical optimization. Here, we investigate the deterioration in image quality caused by thermal-induced surface deformation and propose a passive athermal optical design method to reduce deterioration. To this end, MATLAB was utilized to jointly call finite element analysis (FEA) software (COMSOL) and optical design software (Code V) to realize the data exchange of an optical–mechanical–thermal integrated analysis for iterative optical optimization. This process makes automatic iterative optimization possible by transforming parametric FEA results into Zernike coefficients in each iteration of optimization. The theoretical and design examples indicate that our method can effectively reduce the degradation in image quality with surface deformation. Our method provides an optical optimization approach for optical designers to work on a passive athermal optical design by considering thermal-induced surface deformation.

Road luminaries are required to provide the luminance specified in the standards according to the road characteristics. For this reason, the light from the light source should be directed according to the desired conditions. While the range of minimum average road surface luminance recommended for different classes of road are provided; at the same time, it is desirable to be economical. In this study, a freeform lens and LED luminaire design with high luminous efficacy, low glare and uniform luminance distribution with a height of 1.5 m and a distance of 7 m between poles were designed for M3 road standards. First of all, lens design was made by using optical and illumination design software. Also, lens manufacturing and luminaire production were made as a result of the success of the design simulation test. The success of the LED luminaire in providing CIE standards has been measured on the designed road. In addition, the advantages and disadvantages have been determined by comparing with High Pressure Sodium Vapor (HPS) lamps.

We present an overview of the pros and cons of using GPUs in optical design software. While GPUs can run multiple calculations in parallel, that parallelization comes with a price. We will discuss the trade-offs that allow GPUs to run up to thousands of cores in parallel and how those trade-offs effect the use of GPUs in optical design software. In particular, we review the use of GPUs in several steps of design calculations, including ray-tracing and computationally expensive steps such as calculating Huygens integrals.