November 07, 2019

Ray trace faster using user-defined objects in OpticStudio

Ray trace faster using user-defined objects in OpticStudio

Get non-imaging optical systems to market in record time with simplified Bézier curve. 

At this year’s Envision, John Ellis from Optics for Hire, which helps clients research, design, prototype, and commercialize imaging and illumination optical devices, spoke about the benefits of user-defined optics for non-imaging optical systems design. Following are key points from the presentation which was based on the work of Lead Optical Engineer Anatoli Trafimuk.

The benefit of using user-defined objects when designing non-imaging optical systems

OpticStudio allows optical engineers to compile their own user-defined surfaces, objects, scattering functions, diffraction functions, and more into a Dynamic Link Library (DLL) for use in a lens file. These user-defined functions work just like built-in functions In OpticStudio. This allows for the design of complex objects using non-sequential mode without the need to import an external CAD file. 

According to Optics for Hire’s Ellis, “The use of user-defined objects provides a built-in, fully integrated, simple solution for efficient design of freeform-based illumination systems in non-sequential mode.” The company uses up to four simplified Bézier curves to create surfaces and solid objects—user-defined objects are an easy way to describe the lenses based on Bézier curves. Because the user-defined objects behave like built-in objects, engineers can perform fast ray tracing and comprehensive optimization on designs. 

What is a Bézier curve and why is it useful? 

The Bézier curve is named after Pierre Bézier, who used it for an automotive design in the 1970s. It’s since been used for the design of computer fonts and animation. 

Optics for Hire’s Trafimuk says the curve is simple to use. “It’s controlled by a control points set, which is simply a set of numbers. The points don’t lie on the curve except at the start and end, which works well for building freeform optical surfaces.” 

Following is the simplified Bézier curve parametric equation used by Optics for Hire: 

“With that curve representation, the X control points are equally spaced along the axis,” says Trafimuk. “So, we only use parametrization of the Y part of the curve, which allows us simpler calculations while we create complex object forms that curve. We’ve found that the ray trace for surfaces based on that curve is 30 percent faster than usual Bézier curves and up to 60 percent faster if we’re using a more general NURBS representation. And we retain almost all flexibility of freeform with use of fewer variables.”  The full presentation can be found here. 

The rise of freeform optics

Freeform optics are designs involving one or more freeform surface and are enabling optical engineers to push the boundaries of what they’ve been able to design in the past. Freeform optics are critical for the design of cutting-edge technologies such as lidar for autonomous vehicles and headsets for virtual and augmented reality.

Continuing to support innovative optical design, soon OpticStudio will include a new feature called TrueFreeForm, the latest method in designing freeform optics. 


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