Optical software programs provide optical designers with the means to predict and analyze performance characteristics of optical systems without experimental prototyping. Looking ahead into 2007, optical software will continue to enhance optical design capabilities in several ways. Optical software developers are concentrating their efforts on improving communication channels between engineers in disparate fields who are asked to collaborate. In a word, the direction is “inter-operability.”

Figure 1. Geometrical structure defined with array wizard (forthcoming in ASAP).
In addition to interoperability, optical software developers are steadfastly committed to program enhancements that accelerate and simplify the process of modeling and analyzing optical systems. These enhancements include libraries (of all types), ray-path analysis tools, tolerancing and optimization features, and application-specific enhancements that are taking optical software into new research and development arenas. Here’s an overview of what optical software users can expect in coming releases.

CAD Interoperability

Every optical system simulation begins with an accurate geometrical model. Leading programs currently offer a multitude of options for creating system geometry, each with its own benefits — scripting, spreadsheet builders, computer-aided-design (CAD) import, and embedded CAD-like user interfaces, to name a few.

When optical software programs first became available, geometrical entities were entered in script form. That is, system geometry was defined by commands with adjustable parameters — far from the point-and-click, drag-and-drop user interfaces of CAD environments. However, this non-visual geometry creation method has its advantages.

Scripted geometry has the benefit of being amenable to full parameterization, which can automate analysis steps. Designers often are faced with the tradeoff of parameterization flexibility for convenient geometry definition. For instance, native file-interoperability features and universal translation formats such as IGES, STEP, and XML are available in some programs, but they typically result in “static” imports, requiring that geometry changes are made back in the CAD program where the geometry originated. This limits parameterization options.

Scripted geometry is also optimized for ray tracing, whereas software packages powered by embedded solid modeling engines, or coupled directly to CAD programs, often produce geometry elements that are not optimized for ray tracing engines. In the latter, ray tracing speeds can suffer to the point where thorough analyses are too time-consuming — even on modern PCs.

With all of this in mind, it’s clear that optical software developers are headed in a direction that combines the best aspects of scripted geometry — ray-tracing compatibility and parameterization — with the ease-of-use of highly visual CAD environments. The result will be an increasing number of optical software programs with embedded CAD interfaces and a new class of programs that exist as plug-ins to various CAD packages.

The key difference between these programs and those currently available will be the manner in which geometrical entities are defined for ray tracing engines. User interfaces will look and function like elite CAD programs but will produce sensible geometry characterizations that trace quickly and afford users extensive parameterization flexibility.

Optical Software Interoperability

The core engines of today’s optical software programs generally fit into one of three categories: sequential ray tracing, non-sequential ray tracing, or finite-difference time-domain (FDTD) simulation. The interoperability emerging among these categories of optical software programs is particularly interesting, and one development direction that is ushering in new areas of research and development activity.

Figure 2. Graphical and tabular CIE data output with enhanced functionality (forthcoming in ASAP).
In July of 2005, Tucson-based Breault Research Organization, Inc. (BRO) and Vancouver-based Lumerical Solutions, Inc. announced a partnership to provide comprehensive optical modeling capabilities bridging the gap between microscale and macroscale optical design. BRO’s ASAP Optical Software, a nonsequential ray-tracing program, coupled with Lumerical’s FDTD Solutions, a finite-difference time-domain code, benefits engineers and scientists who work to integrate micro- and nano-optical components within larger optical systems.

Figure 3. Ray trace through realistic human skin model (forthcoming in ASAP).
Together, ASAP and FDTD Solutions are able to model systems with both macro and microstructures working in concert in the optical path, enabling optical designers to address a whole range of problems that were previously inaccessible.

Examples of systems requiring this expanded modeling capability include display backlight units, imaging systems relying on microlenses, CD and DVD data-reading systems, and telecommunications devices. Additional interoperability enhancements will follow, as new applications for the marriage of non-sequential ray tracing and FDTD simulation are uncovered.

Libraries

Following geometrical system characterization, optical designers must define material properties and sources to complete their system models. To save time, software developers are expanding the ready-to-use libraries that come with their releases.

Material properties are the boundary conditions telling the analysis engine how to treat optical interactions at system interfaces: optical transmission, absorption, diffraction, and scattering. Comprehensive material libraries describing these boundary conditions for a variety of materials accelerate system setup and eliminate the burden of creating custom interface models based on lab measurements. Similarly, developers are expanding source model libraries to include sources such as incandescent bulbs, arc sources, LEDs, and cold-cathode fluorescent lamps, which save users hours and ensure accurate system characterization.

Specific Enhancements

Near-term enhancements to BRO’s ASAP Optical Software will include features that simplify system characterization and make new types of analyses possible. Here’s a preview:

  • Expanded features for ray-path analysis will help users quickly visualize system behavior in ways not possible in laboratory settings and new to optical software tools.
  • Enhanced system tolerancing routines will allow users to explore manufacturing tolerances and optimize their designs using figures of merit and compensators.
  • Array definition wizards will simplify the creation of complex geometry arrays seen in backlighting systems and other applications without sacrificing ray trace speed.
  • Expanded features for numerical and graphical CIE/chromaticity analyses will allow users to better visualize color characteristics of optical systems.
  • Interactive plug-ins for modeling complex volumetric scattering in biological systems will be released.

This article was written by Michael Stevenson, director of marketing, at Breault Research Organization, Tucson, AZ. For more information, contact Mr. Stevenson at This email address is being protected from spambots. You need JavaScript enabled to view it..


Photonics Tech Briefs Magazine

This article first appeared in the November, 2006 issue of Photonics Tech Briefs Magazine.

Read more articles from the archives here.