OPTICAL SYSTEM DESIGN

Software environment creates coherent workflow for optical system design

GIACOMO VACCA, SEAN MURPHY, TAPIO KARRAS, and HANNU LEHTIMÄKI

Bidirectional interfacing with other ends with detailed speci- long using tools intended for detailed optical tools, real-time visualization, fications for vendors and simulations. and interactive altering of designs all mechanical and manu- A new design environment, called facturing engineers. But BeamWise, has been developed to ad- spur optical design creativity. getting from the sketch dress these longstanding problems. The Optical system design feels like the step- to a detailed spec is painful, time-con- software is intended to be an intuitive child of the digital revolution. While suming, and requires using many dis- system design environment. It does not powerful, intuitive, fast computer-based parate and disjointed tools. Existing replace CAD systems or detailed opti- tools are available to engineers in fields optical-simulation tools, while effective cal modeling tools—rather, it integrates from integrated-circuit layout to aircraft for specialized applications, take signif- these tools into a coherent workflow design and architecture, designers of op- icant amounts of time to provide an- for optical system design (see Fig. 1). tical systems are coping, for the most swers and often lack interfaces for com- Each tool thus can perform efficiently part, with antiquated software. Optical municating with other tools. Designers systems have numerous complex con- struggle with suboptimal tools, espe- straints and requirements—their chal- cially during the earlier, iterative stag- FIGURE 1. BeamWise integrates lenges go beyond designing the perfect es of the design process. For example, the entire optical design workflow. After interactively creating a rough lens or excellent components. when simulating and evaluating the optical layout, the functional design The design process typically starts “rough draft” of a functional layout, is verified and tweaked using optical with rough, hand-drawn layouts, and the time involved can be impractically ray-tracing or full-propagation modeling tools (middle row, left) called directly from BeamWise. Optomechanical components are then added to the model using either linked databases from catalog suppliers (top row) or one’s own custom/proprietary parts. The resulting optomechanical design is checked in BeamWise for physical conflicts and adjusted as needed. To run final checks, the design is exported as a 3D file to CAD tools (middle row, right) and/or as a Zemax file. Final design files (2D drawings, bill of materials, 3D model) are generated for documentation and transfer to manufacturing (bottom row). (Courtesy of BeamWise)

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at what it does best for the benefit of the conflicts, efficient design reuse, and trans- 2. Perform high-level verification. entire design process. parent capture of design intent. Real-world Through bidirectional interfaces built The BeamWise 3D Model, a “virtu- projects with the National Cancer Institute into BeamWise, send the optical sys- al optical bench,” can be seamlessly im- and other research groups have illustrat- tem prescription to simulation and op- ported into CAD environments. Because ed the power of this approach. tical modeling software such as Zemax it allows bidirectional interfacing with the OpticStudio or Optica. By focusing only other tools, designers can have real-time An improved design workflow on the essential elements, this stage can visualization, interactive change man- Using the software as a design tool for verify in real time that the design archi- agement, instant addressing of physical a complex optical system, engineers can tecture is sound. quickly create a lay- 3. Iterate. Automatically import any out, verify the op- modifications back into BeamWise and System design workow Tools used tical and mechan- repeat the verification process as needed. ical aspects of the 4. Add optomechanical fixturing. Use Create rough-draft BeamWise Adjust design optical design design interactively, off-the-shelf components from catalogs as needed and iterate to gener- such as those from Thorlabs, Newport, in real time BeamWise Perform Functional modeling tools ate a near-final de- Edmund, and Qioptiq to support and in- high-level verication (e.g., Zemax, Optica) sign for prototyping tegrate all the optical components, or in- or production. The corporate custom parts from proprietary Add optomechanics, BeamWise procedure provides design files. custom xtures the most useful feed- 5. Analyze physical conflicts. Use back at the appropri- BeamWise to identify and resolve any is- Identify, resolve BeamWise ate stage of the design sues caused by mounting. physical conicts process. Here is a typ- 6. Export the system to design tools. ical workflow, which Transmit the resulting complete system Optics (Zemax), 3D CAD Export Fig. 2 summarizes: (optics and optomechanics) as a 3D file design (e.g., SolidWorks, AutoCAD) 1. Rough out a de- to CAD tools such as SolidWorks or sign. In the BeamWise AutoCAD for mechanical and manufac- Run detailed System-level optical simulations, optical simulation tools environment, cre- turing engineers to use. BeamWise can nalize design (e.g., LensMechanix, FRED) ate a virtual optical also generate 2D engineering drawings bench in real time. and bills of materials. Design completed The system concept, 7. Analyze optical performance (op- the equivalent of a tional). As the final step, export the re- FIGURE 2. A step-by-step design workflow is shown for a complex hand-drawn sketch, sults to optical analysis software such as optical system. It is more efficient to iterate at a high level first, and is translated into a LensMechanix, Code V, or FRED to run refine later. With BeamWise, designers create a rough design layout, verify the design in real time, implement optomechanical supports, functional layout of detailed simulations and perform stray- and export to specialized tools for final checks. optical components. light analysis. Note that these simula- tions take a long time and cannot be iterat- a) b) ed quickly.

Advantages of an integrated approach As a system design tool, the software al- lows designers to vi- sualize the entire op- tical and mechanical FIGURE 3. This example of the rough-draft stage of optical design (a) is drawn from a customized Potomac flow system before commit- cytometer designed by Kinetic River for the National Cancer Institute. All the optical components are instantiated ting to specific hard- interactively with BeamWise, leaving refinements such as supports, precise component distances, and detailed specifications to a later stage. This allows real-time iterations and rapid verification of design intent without being ware, cutting metal, bogged down by full, computationally intensive simulations of optical propagation; the finished, assembled instrument or buying parts. This for the National Cancer Institute is shown (b). (Courtesy of BeamWise) reduces redesign and

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rework, and eliminates the inconvenience considerations. The model was then ex- of the project, with only few and minor and expense of parts returns and scrap- ported as 3D file to a CAD environment tweaks introduced in the later stages of ping. The software provides an intelligent to implement additional supports, verify design and manufacture. link to the optical layer, allowing bidi- the overall structure, and provide blue- rectional transfer of information to spe- prints for assembly. Giacomo Vacca is chief science officer, Sean Murphy is vice president of business cialized optical modeling tools. Designers The software enabled the design process development, Tapio Karras is vice presi- can take advantage of the capabilities of to proceed rapidly and efficiently through dent of R&D, and Hannu Lehtimäki is pres- these tools knowing that no information the early “what-if” stages. The resulting ident, all at BeamWise, San Jose, CA; e-mail: has fallen through the cracks. design remained stable through the rest [email protected]; www.beamwise.com. This approach also enables design- ers to reuse and recycle existing designs. Because components are anchored to the NOW local optical axis, altering the baseline AVAILABLE design to generate a derivative system is much faster than starting from scratch. The revised model still incorporates the intelligent optical path definitions used for bidirectional interfacing to special- ized modeling tools.

Case studies Professor John Nolan, then at La Jolla Bioengineering Institute (La Jolla, CA), wanted to reduce the risk of physical interference conflicts between optical components in a prototype instrument. BeamWise modeled the system to detect problems and provide recommendations for next steps, enabling the designers to scope and prioritize refinements to im- prove performance, robustness, and cost of the system. Next, the instrument’s schematics and parts were incorporated into the software, which generated a beam-anchored CAD model of the mechanical components. The output further guided the design of a man- ufacturable version of the instrument. In addition to the improvements to the de- sign, the engineers concluded that using BeamWise would make future design re- visions more efficient. Designing a custom flow cytometer for the National Cancer Institute involved creating an optical system design from scratch. Using BeamWise, designers at Kinetic River started by rapidly devel- oping a layout of the functional optical components. They created a virtual op- tical bench (see Fig. 3) to visualize the ar- chitecture and identify potential issues early in the process, quickly iterating lay- out choices for functional and ergonomic

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