Global Surgical cuts product development time with Zemax Virtual Prototyping

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1 CUSTOMER SPOTLIGHT Global Surgical cuts product development time with Zemax Virtual Prototyping Learn how Global Surgical streamlined workflows and produced a successful physical prototype months ahead of schedule using modern virtual prototyping.

2 Abstract In mid-2016, Global Surgical Corporation set out to redesign a set of symmetric eyepieces for its A-Series dental microscope. Their goals were to increase the field of view and enhance usability, while maintaining or reducing costs. Global used Zemax Virtual Prototyping tools OpticStudio and LensMechanix to redesign the eyepieces. This paper details the challenges of the project and the impact on the design process, workflow, and schedule.

3 Figure 1: The A-Series dental microscope. Introduction Global Surgical Corporation has been manufacturing medical equipment for dental and otolaryngology specialists for more than 80 years. A partnership in 1965 led to the launch of surgical microscopes and accessories. As microscopes became more widely accepted in the medical field, they have become an indispensable tool for diagnostics, treatment, and surgery applications. The increased visibility through magnification enables practitioners to do less invasive treatments. One of the first companies to focus on the newly emerging dental microscopy market, Global is now a world leader. The St. Louis, Missouri-based company s A-Series dental microscope, unveiled in 2015, raised the bar for the industry. The A-Series (shown in Figure 1) delivers high-resolution, color-correct images that are fully integrated in a compact optical head with superior ergonomics, maneuverability, and stability. Design challenges in improving a pupil eyepiece To maintain industry leadership and increase customer satisfaction, Global Surgical set out to redesign a set of symmetric eyepieces for the A-Series microscope in mid The goals for this project were to increase the field of view and enhance usability, while maintaining or reducing costs. One of the main challenges was to improve the optical performance of the system within a highly constrained design envelope, including eye-limited optics and packaging with adjustment mechanisms. To achieve the desired result, the size of the optics increased, leaving less space for mechanics and ergonomic fit and comfort. Real estate was in short supply but in high demand. Robert Mentzer, optical engineer and project lead, determined that the optics could be adjusted to increase the field of view and still meet the size restraints. However, this discovery required changing nearly all the mechanical components, which increased the mechanical design work required. The eyepieces had to be intuitive. "Eyepieces can be uncomfortable, especially for people who wear glasses. We needed an always fits solution, something straightforward and inviting," said Robert Mentzer, optical engineer and project lead. Robert was joined on the project by mechanical engineer Tim Stiefferman, who explained, "Improving usability meant simplifying the mechanical operation for our users, to create something that doesn t interrupt or distract from their work." From experience, Mentzer and Stiefferman knew that designing the optomechanical system was a big challenge. Small errors in the optomechanical design can cause serious optical performance issues. Zemax Customer Spotlight 2

4 Figure 2: On the left is an example of an eyepiece using a Plossl design. On the right is a 2D drawing of a Plossl design created in OpticStudio. Working with a sensitive system The Plossl design used in the eyepiece, shown in Figure 2, consists of two achromatic doublets with very small air spaces. The objective lens collects light and brings it to focus to create an image. This type of optical design is also used in telescopes, cameras, and many other devices. Plossl optical designs rely on maintaining consistent airspace between the two doublets over the entire surface of the lens. To reduce the size of the optics train, Mentzer and Stiefferman needed to minimize the air space between lenses. Careful tolerancing of the optical and mechanical components was essential for success. If the air space between the two doublets was inadequate given the tolerance stack-up, the air space could vary over the surface of the lens or worse, the lenses could come into contact with a mechanical or glass component, which could cause ghost reflections and fringing, resulting in a bullseye appearing at the image plane. Mentzer and Stiefferman had to weigh the tradeoff between the product s performance and the increased costs of using tighter tolerances to achieve the desired outcomes. High-quality initial design using Zemax Virtual Prototyping Mentzer created the optical model for the eyepieces in OpticStudio, the industry-leading optical design software by Zemax. He then sent the design file to Stiefferman, who loaded it into LensMechanix, the SOLIDWORKS Certified Gold Partner add-in for optomechanical development, also developed by Zemax. LensMechanix is the first software specifically designed for mechanical engineers to package, analyze, and validate optomechanical designs in SOLIDWORKS. The OpticStudio design file loaded into LensMechanix included all the data needed to design the mechanical packaging. Previously, Stiefferman had to work with frustrating STEP files and manually add the dimensions, tolerances, materials, and finishes. Eliminating that manual work meant he could begin building mechanical geometry immediately. 3 Zemax Customer Spotlight

5 "By using OpticStudio and LensMechanix, we honed in very quickly on one design. We had a high-quality optical and mechanical design candidate in one week," said Mentzer. "We could then turn our attention to things like color, feel, and exterior cosmetics." The Zemax Virtual Prototyping tools, OpticStudio and LensMechanix (shown in Figure 3), helped Global get to a high-confidence design more quickly by streamlining the workflow and communication between the engineers. "In one short meeting, I explained the critical elements of the model, including the location of the field stop, eyeball, and range of travel," said Mentzer. "Tim and I weren t poring over drawings. We weren t running back and forth between our offices." Mentzer and Stiefferman passed the design between OpticStudio and SOLIDWORKS without losing critical design data. "The communication piece with the mechanical engineer became much easier," said Mentzer. "It let me stay on an optics bench and in OpticStudio, and it let Tim stay in SOLIDWORKS with LensMechanix and on his CNC machine." Figure 3: The Zemax Virtual Prototyping solution helps optical and mechanical engineers get to a qualified design more quickly by streamlining the workflow and communication between engineers. They can see the impact of each other s work while working in their preferred environments. Outdated workflows before Zemax Virtual Prototyping For years, optical and mechanical engineers have struggled to collaborate due to incompatibility between optical design and mechanical computer-aided design (CAD) software. Through trial and tribulation, a workflow evolved. Engineers and designers cobbled together a solution that involves the import and export of files, manually reconstructing geometry, and approximating the light path using a small sample of rays. Preserving the integrity of optical data when transitioning from optical to mechanical designs often poses a challenge for companies. Mentzer explained, "As we prepare an optical design for packaging, we have mechanical engineers in mind. Even so, during handoff we encountered challenges in communication." Although the toolbox for optical engineers has expanded, mechanical engineers have lacked tools to analyze and validate the impact of mechanical geometry on optical performance. The common practice is for mechanical engineers to import optical systems into SOLIDWORKS as STEP, IGES, or STL files, and to rely on ray bundles to approximate light propagation. These file formats degrade the accuracy of designs. They also strip out the optical tolerances, coatings, and material data during file conversion. Without a quick or accurate way to check that the mechanical geometry does not impact optical performance, mechanical engineers rely on optical engineers or build physical prototypes to validate problems. When mechanical engineers send STEP files back to the optical engineer for validation, the optical engineer must deal with inconsistent global coordinate systems and lost design fidelity. They also must manually locate mechanical components to recreate the assembly that the mechanical engineer created in SOLIDWORKS. To avoid this hassle and extra work, many engineering teams use screenshots, pen and paper, or physical prototypes to validate the design. Although these techniques may seem simpler, their imprecision can introduce errors and quickly drive up costs and affect schedules. Zemax Customer Spotlight 4

6 Figure 4: The left image shows ray trace results in OpticStudio for a doublet optical design like Global s pupil eyepiece project. On the right, the same design is packaged in LensMechanix and then analyzed by running a ray trace. Mechanical design issues discovered early using LensMechanix LensMechanix changes all this. Instead of using STEP, IGES, or STL files to represent optical components, LensMechanix loads lens data from OpticStudio into a SOLIDWORKS assembly. With immediate access to all the optical component data in native SOLIDWORKS format, Stiefferman exposed the optical component construction geometry in LensMechanix and within minutes began designing the optomechanical system. After roughing out the mechanical design, Stiefferman used LensMechanix to run a ray trace through the entire system in SOLIDWORKS to view how light travels through the system, as shown in Figure 4. He could then assess the impact of the mechanical geometry on optical performance to ensure that it did not clip the light path, cause stray light, or cause other problems. Additionally, he was able to reduce the number of mechanical components and minimize the overall package dimensions with complete confidence. "Before LensMechanix, it was difficult to get all the design data we needed," explained Stiefferman. "With paper and STEP files, the full design was not communicated. On previous projects, some errors could only be found after making a physical prototype and testing the product in the lab. Catching errors this late in the product development cycle often increases time to market and project costs." LensMechanix enabled Stiefferman to catch and correct errors early in the design process, when changes were cheaper and easier. "LensMechanix gave me clarity on how my designs impacted the optical performance. We had the exact optical design in SOLIDWORKS. I could quickly expose the dimensions I needed, such as the optical axis or clear aperture, and know exactly where the mechanical components needed to be." "There are a lot of sensitive parts in an eyepiece, which made it a great project for LensMechanix. But until now we didn t have the mechanical engineering design tools we needed," said Mentzer. "By bringing all the data into SOLIDWORKS and seeing how rays interact with both the optical and mechanical components, I can determine what I can and cannot do," said Stiefferman. "Now, optics are speaking my language in my design environment. The package of data I can have in a single design file is far superior to the 20 plus drawings I had to rely on before LensMechanix." 5 Zemax Customer Spotlight

7 " With LensMechanix, optics are speaking my language in my design environment. The package of data I can have in a single design file is far superior to the 20+ drawings I had to rely on before LensMechanix." - Tim Stiefferman, Mechanical Engineer

8 Projected vs. Actual timeline of A-Series Project 1-Oct 1-Nov 2-Dec 2-Jan 2-Feb 5-Mar 5-Apr Projected candidate design Projected marketing prototype Projected design completion Candidate design Marketing prototype Design completion Projected schedule Actual schedule Time savings 106 days cut from project Time saved Figure 5: The original project was expected to take six months. Instead, the first prototypes were completed three months ahead of the initial target date, improving the overall project timeline. Simplified information exchange reduced product development time After analyzing and validating the optomechanical system, Stiefferman created an OpticStudio output file in LensMechanix that includes the original optical design and the new mechanical components. He sent the output file to Mentzer to load into OpticStudio and perform further analysis as needed. This native OpticStudio file of the integrated design helped Mentzer and Stiefferman get to a complete model early in the design process. As a result, they were able to prototype the eyepiece and hold design reviews with the marketing team months ahead of schedule. "We had a fully functional physical prototype in the hands of marketing for evaluation three months ahead of schedule," said Mentzer. "In time savings, we knocked this project out of the park. A seamless optomechanical exchange cut two months out of the project in the back and forth in the modeling piece the concepting, development, and prototype period. Using 3D printing technology and in-house CNC machining, we cut another month from the development cycle, completing the prototypes in December instead of March. That enabled us to work on other product development projects sooner than anticipated." 7 Zemax Customer Spotlight

9 " In time savings, we knocked this project out of the park. Zemax tools enabled us to complete prototypes before our CAD time budget was spent. We got to start working on the next design project early." - Robert Mentzer, Optical Engineer Zemax Customer Spotlight 8

10 Figure 6: An early prototype of the new Plossl eyepiece. First physical prototype a big success To prototype the eyepiece, Stiefferman created multiple pieces of each part. From this set, the engineers showed the marketing team a side-by-side comparison with the original A-Series eyepiece. Figure 6 shows an early physical prototype. The first prototype was well received by the marketing team. Their feedback was mostly cosmetic. For example, they wanted softer materials for the eyecups, and they wanted the eyepiece to be closer to the eyes. "Not only did the project come in early, the things that prototypes are normally criticized for such as the optical design, the diopters, or vignetting were absent," said Mentzer. "The first physical prototype was a big success." By visualizing how light travels through the complete optomechanical system and by identifying potential impacts on optical performance, LensMechanix gave the engineers confidence to build critical components in metal for marketing, rather than in plastic. "Plastic models are fragile and constantly break during design reviews," explained Stiefferman. "Because of LensMechanix, we were able to minimize 3D printing and go straight to metal, which is much more durable and gets us to a high-fidelity prototype." Correcting problems using Zemax Virtual Prototyping offers a significant advantage because many performance problems can t be found using 3D printed or rapid CNC-machined prototypes due to the limitations of materials and the production process. Additionally, metal prototypes are expensive and time-consuming to produce. "Not only did the project come in early, the things that prototypes are normally criticized for were absent. The first physical prototype was a big success. The final product we ship in a few months won t vary much from that first prototype." - Robert Mentzer "The handoff from OpticStudio to LensMechanix is clearly superior," said Stiefferman. "Not just for drawings and line work, it significantly sped up the mechanical design. I already had a mechanical head start by having all the optics locked in space. I did not have to redraw the lenses in SOLIDWORKS or pull data from the spec sheet." "The acceleration is fantastic," said Mentzer. "No paper, no STEP files or ray bundle objects. I don t hum drum with these horrible question loops. No endless back and forth with the mechanical engineer." "LensMechanix gives a great understanding of the impact on the optics. We headed off several potential issues. We can now go down a more deliberate path." Tim Stiefferman "LensMechanix was very easy to use," added Stiefferman. "We re now able to move from an optical concept to a dentist s office more quickly." 9 Zemax Customer Spotlight

11 Standardizing on Zemax Virtual Prototyping Finding a faster, more efficient way to interface between SOLIDWORKS and optical software has been Global s dream for a long time. Based on the accurate design and accelerated schedule achieved on the A-Series eyepiece project, Global is using OpticStudio and LensMechanix to design future optical systems. "OpticStudio and LensMechanix will be the standard way we execute projects from now on," said Mentzer. "They enabled us to achieve a much more complete software model. By that, I mean we were able to design with accuracy. It s another step on the confidence path in development." Mentzer has become a big fan of OpticStudio since he began using it three years prior. "I prefer OpticStudio to its competitors. I ve used two other design software packages. Both were clunky and required encyclopedic knowledge of command scripts; it felt like I was using someone else s secret language. I really like the OpticStudio user interface. To me, the new tool ribbon in OpticStudio is the selling point. I spend a lot less time inside a user manual and more time doing the human piece of lens design." "For tolerancing an optomechanical system, OpticStudio plays very nicely with CAD. OpticStudio tolerances translate directly to SOLIDWORKS. For example, I quickly discovered two surfaces that crashed into each other where I got sloppy with my tolerances," said Mentzer. "Zemax gives me the tools I need to get to other projects faster. In my role, good designs are value added, but failed designs are a waste of resources," said Mentzer. " LensMechanix is going to help us give our customers better products faster, and drive growth for Global Surgical. We ve just scratched the surface of what it can do," said Stiefferman.

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