Moving cutting-edge technologies in optics and photonics from incubation and prototyping to mainstream commercialization remains a challenge, and the pace of progress demands rapid innovation. A key element to developing systems for mainstream commercialization is manufacturability. Processes need to be in place for affordable production at scale, but products must also be designed with manufacturability in mind from the start. With a clear understanding of how a product will be fabricated, assembled, and packaged, engineers can effectively leverage simulation tools to design systems in which the impacts of manufacturing errors on product performance are minimized. 

Tolerancing is often used to determine how manufacturing errors impact optical system performance. Tolerances are generally categorized by surface and material perturbations and element perturbations. The impact of surface and material errors on optical system performance can of course be mitigated by designing products using geometries and materials that are inherently easier to manufacture.  A great example of this is showing up in the design of cell phone lenses. 

Last month I had the pleasure of participating on a panel with Jose Pozo (Director of Technology and Innovation at EPIC), Theodor Nielsen (CEO and Founder of NIL Technologies) and Oscar Fernandez (CTO of the PHABULOuS Pilot Line) in which we discussed the next generation of cell phone lens design. Part of the discussion centered on the increasingly important role that complex aspheres play in reducing size and improving performance for cell phone lenses. 

An asphere model gaining traction for usage in cell phone lens systems is the Q-Type Asphere described by Dr. Greg Forbes, as this model was constructed to inherently consider manufacturability as a part of the surface description^1-3. The Q-Type Asphere has been available in the sequential mode of OpticStudio for some time, but with the release of OpticStudio 21.2 the full 3D geometry of the aspheric lens can now be modeled in non-sequential mode. This addition allows the aspheric lens to be natively imported from OpticStudio into CAD using OpticsBuilder 21.2. With native import into CAD, lens edges can be customized and thus optimized for the tight space requirements of the camera.  

The addition of the Q-Type Asphere to the non-sequential mode of OpticStudio also enables full 3D simulation of stray light impacts on system performance. In general, the effects of stray light are critical to understanding the design and manufacturability of an optical system. However, determining the sources of stray light can be a challenge, as this assessment requires tracing a large number of rays followed by a detailed analysis of that ray data to identify the paths by which stray light can reach system sensors.

Architectural updates in OpticStudio 21.2 greatly simplify the detailed analysis of the ray data, by allowing path data to be stored during the ray trace itself, eliminating the need to construct this information from the detailed ray database. New filter strings have also been added for limiting the number of rays stored in the detailed ray database, providing an easy means to both query and visualize the results. 

As ray path analysis often indicates, the optomechanical components used to assemble and package the design are important sources of stray light that can degrade system performance. These components also introduce structural and thermal loads that can deform the optics and impact system performance. These deformations are characterized through finite element analysis (FEA) of the optics under load. 

The ability to directly assess the impact of the deformations on optical performance is critical to creating a robust design for manufacturability. This direct assessment has been greatly simplified in OpticStudio 21.2 with the release of the STAR module, which allows surface deformation and 3D temperature data generated by any FEA software package to be applied to nearly any sequential model. A great example of this workflow was recently presented by the ANSYS OptiSLang team at their annual optimization and design conference⁴, in which they demonstrated the ability to use OptiSLang to automate the workflow between ANSYS Mechanical, the STAR module, and OpticStudio⁵. 

As described above, the recent release of Zemax software tools added a series of new capabilities aimed at providing design engineers with the tools needed to design for manufacturability. As simulation tools advance, this continues to accelerate the already rapid pace of innovation within the optics and photonics industry! 

Author:

Sanjay Gangadhara
Chief Technology Officer
Zemax, LLC

References:

1 https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-18-19-19700&id=205478 
2 https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-15-8-5218&id=132268 
3 https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-19-10-9923&id=213662 
4 https://www.ansys.com/events/21-06-17-wost 
5 https://www.ansys.com/content/dam/events/event-pdfs/wost-conference-agenda-2021.pdf