Breault Research Organization (United States)

PURPOSE: To present a commercially available optical modeling software tool to assist the development of optical instrumentation and systems that utilize and/or integrate with the human eye. METHODS: A commercially available flexible eye modeling system is presented, the Advanced Human Eye Model (AHEM). AHEM is a module that the engineer can use to perform rapid development and test scenarios on systems that integrate with the eye. Methods include merging modeled systems initially developed outside of AHEM and performing a series of wizard-type operations that relieve the user from requiring an optometric or ophthalmic background to produce a complete eye inclusive system. Scenarios consist of retinal imaging of targets and sources through integrated systems. Uses include, but are not limited to, optimization, telescopes, microscopes, spectacles, contact and intraocular lenses, ocular aberrations, cataract simulation and scattering, and twin eye model (binocular) systems. RESULTS: Metrics, graphical data, and exportable CAD geometry are generated from the various modeling scenarios.

To insure that an optical system performs to specifications, the optical engineer needs to fully consider several aspects of the design process. Each of these tasks can be aided with the use of software tools. The optical engineer needs to understand the strengths and limitations of the available software tools and how to best apply these programs to each design. There are several distinct steps in the implementation of an optical system: the first order optical layout, optimized design of the optical system, performing stray, scattered and ghost analysis, performing a tolerance analysis of the optical system and performing manufacturing analysis. Although each of these steps are often considered separately, and often require the use of several different software tools, it is imperative for the engineer to consider the entire process during each phase of system development so that issues arising from stray light or manufacturing tolerances do not force a redesign of the system. A thorough understanding of the optical design and analysis process as well as the proper use of available optical software tools are necessary to insure the optimum optical design for each specific application.

Sequential and non-sequential optical codes can be used for much more than the initial design and analysis of idealized optical and illumination systems. The design process usually assumes ideal components, ignoring realistic properties such as surface and volume scatter, Fresnel reflections, and polarization aberrations. These codes can also be used to perform tolerance analysis on these designs to help determine manufacturability limits. An important extension in the use of these programs is to create simulations based on the as-built components which include realistic optical surface and scatter scenarios. For example, modeling the measured optical quality of a fabricated primary mirror surface provides the opportunity to modify other optical or mechanical parameters to compensate for any surface errors, which in turn, can relieve critical tolerance limits. Optical analysis codes can also be used to model the performance of an optical system during assembly and testing to isolate defects and perturbations which cause the system performance to be out of specification. Interferometric or polarimetric data measured at several locations across the field of view can be used in the optical program to help identify out of tolerance components. These capabilities are of particular importance in eccentric systems as well as in polarization critical systems, provided the optical code can realistically model data in this form.

Illumination systems suffer from a lack of optimization research. Optimization is typically done based on intuition and experience. I will review research to date, especially with respect to imaging system optimization. I will show examples with the Simplex method; highlighting the end and start games, performance increase, and convergence improvement.

The superconic surface description has been around since 1986 and more recently implemented in commercial design software. A simpler version dubbed the 'subconic' is proposed and appears to work well in applications requiring steep aspherics.

In illumination systems the look and feel are often more important than objective criterion, such as uniformity and efficiency. The reason for this is two fold: the lit appearance often sells an item and substantial variation in the illumination distribution (up to 50%) over a broad region is not noticeable to an observer. Therefore, subjective criterion, such as the lit appearance, typically plays a crucial role in the development of an illumination system. Additionally, by using computer models to ascertain the lit appearance before manufacture of the system, it allows the designer to modify the system while not demanding investment to produce prototypes. I discuss methods of determining the lit appearance for illumination systems. This modeling includes the inclusion of material and surface properties, such as surface finish, spectral transmission, and internal scattering; the response of the human eye; and the amount of rays that must be traced. By archiving the ray data, animations as a function of position and angle can be developed. Examples are developed to highlight the utility of this technique. These examples include taillights for the automotive industry and a backlit LCD screen for a laptop. Animations of these models demonstrate their luminance.

We present the concept of principal sections of a lightpipe to analyze the propagation of light through the lightpipe by total internal reflection. Only the principal sections determine the acceptance angle and thus help in the identification of regions where the leakage occurs first. Use of principal sections for analysis leads to a significant reduction in the design effort. We present an analysis of several commonly used lightpipe configurations, e.g., straight and single circular bend, and different cross sections, e.g., elliptical and rectangular. This analysis leads to the maximization of throughput and transfer efficiency. The uniformity characteristics of elementary configurations and scaling factors for a lightpipe with a single circular bend are also discussed.

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text BILL CASSARLY, DAVID JENKINS, ANURAG GUPTA, and R. JOHN KOSHEL, "Hidden Devices that Light Our World: Lightpipes," Optics & Photonics News 12(8), 34-39 (2001) Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

This paper will summarize the stray-light study commissioned by USRA from BRO (Breault Research Organization) to estimate the level of dynamic background that might be observable at SOFIA's focal plane. This dynamic background is due to cavity and aircraft motions with respect to the inertially fixed telescope. BRO used their ASAP program to trace rays emitted from the Earth, aircraft engines, and telescope cavity to the focal plane through reflection and scatter off a number of surfaces (including Level 500 contaminated optics).

Ghost reflections are a major consideration in the optical design of the National Ignition Facility (NIF). The first-order layout (e.g., spacing between components), the lens shape, and the dimensions of the building are strongly affected.