Previous work has demonstrated the optimization of spatial distribution, angular pointing, angular widths, and design efficiency of light guide luminaires using prismatic light extraction elements. See, for instance, [1]-[4]. Increasingly, in the automotive industry—and for signal lighting in particular—light guide luminaires that use secondary arrays of micro-optics are becoming more common. Typically, these secondary micro-optics are used either to scatter light selectively (micro partially scattering arrays), or to steer light (for example, micro prism arrays). In this work, we focus on the latter type of secondary optic arrays: micro prism arrays. As in previous studies, for this work, all geometrical elements were created in, and optical simulations were performed in, a CATIA V5 Based environment [5]. We build on previous optimization techniques to create signal lamps; used in conjunction with arrays of prismatic elements that are part of secondary lenses. The secondary lenses are used to refine the angular distributions further. These modifications help to meet intensity test point specifications while at the same time preserving quality visual appearance. Typical sizes of the arrays studied are 0.25mm to 1mm pitch, with tens of elements to tens of thousands of elements.
The emergence of OEM and industry benchmarks [1-6] raised the expectation regarding automotive headlamps performance in the last decade, resulting in growing benefits regarding traffic safety. Concomitantly, designing headlamps has grown in complexity, especially for low beam and high beam applications. Fulfilling all requirements concurrently is challenging, not merely due to the large number of requirements to keep track off during development, but predominantly due to the simultaneous inclusion of lamp- (luminous intensity) and vehicle-based (illuminance) metrics in the design. In this paper we propose and demonstrate an alternative design methodology for the development of forward lighting systems with the goal of reducing development time, providing superior photometry, and providing more structure to the development process. Instead of iteratively adjusting optical surfaces and running subsequent simulations to validate each design step, checking whether the change could achieve the respective design objective, we are subdividing the overall design problem into multiple steps and solve multiple inverse problems instead. Specifically, we compile all requirements into a unified set of luminous intensity requirements. Subsequently, we create analytical light distributions that meet this total set of requirements. Once validated, the resulting target light distribution is fragmented into multiple light distributions, which are then used as individual design targets for the creation of freeform surfaces in support of each optical sub-component. The total light distribution is obtained by superposition of all partial light distributions.
Freeform optics is poised to revolutionize the optical systems of our collective future, including high precision imaging systems. In this tribute paper to Roland Victor Shack, we tell the story of how Nodal Aberration Theory (NAT), invented by Shack and developed to 5th order by Kevin Paul Thompson, took on an incredible journey to become the foundation for the aberrations of freeform optics. Nodal Aberration Theory was conceived initially to understand the aberrations of misaligned optical systems. Nodal aberration theory is beautiful, as is any mathematical construct that reduces complex problems into simple formulations. The impact of moving from 100 years of design with rotationally symmetric surfaces (or sections of) into freeform optics is tremendous and opens the design space towards higher performance, more aggressive specifications in the field of view and F/#, more compact solutions, broadband solutions, and distortion-free or distortion-tailored designs.
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