Computational Optics

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Annika Völl

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Annika Völl

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+49 241 8906 8369

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Computer-based models and simulations enable an economic and fast insight into the functionality of optical systems as well as a fast prototyping thereof. Thus, complex design problems and analyses can be treated efficiently and with high precision while accounting for the relevant physical properties.

The Computational Optics group performs research on various numerical approaches in photonics. Among others, these are the design of freeform optics, the computation of application specific intensity distributions in laser materials processing as well as the algorithmic based increase in imaging resolution through ptychography. To this end, numerous software IDEs and strategies are used, while several high-performance computers are available.

 
 

Design of highly efficient freeform optics

Compact freeform lens for an automotive fog lamp Copyright: © Fraunhofer ILT Compact freeform lens for an automotive fog lamp

Refracting and reflecting surfaces that strongly depart from spherical and aspherical shapes are referred to as freeform optics. Here, the techniques of classical optics design can no longer be applied, and new algorithms need to be developed, focusing on the efficient redistribution of energy to tailor irradiance or intensity distributions. This principally enables the generation of very complex illuminance distributions, which is only constrained through physical limitations as e.g. high etendue or low beam quality. Freeform optics are used in high-efficiency luminaires, to reduce energy consumption and operating costs for a given illumination setup. A novel application area of freeform optics is the realization of application specific intensity distributions for laser materials processing.

The Computational Optics group develops freeform optics tailored to non-imaging applications for industrial and research customers. Current research topics include the development of design algorithms for various types of light sources as well as the Fresnelization of freeform optics for space reduction. In the development of such design algorithms, we benefit from research in the fields of differential geometry, computer graphics as well as nonlinear optics.

Collaborating with local manufacturers, we provide virtual prototypes with a production-ready design, and we perform the characterization of the manufactured optics.

 
 

Solution of the Inverse Heat Conduction Problem in Laser Materials Processing

False color representation of a simulated intensity distribution Copyright: © RWTH TOS Application adapted intensity distribution for laser hardening

In the numerous methods of laser materials processing, the applied laser beam induces a temporal and spatial varying temperature profile within the treated material, which in the end determines the processing quality as well as efficiency. As this temperature profile is influenced significantly by the laser beam’s intensity distributions, the purposeful realization of temperature profiles is enabled by an application specific beam shaping. To this end, it is necessary to deduce the intensity (i.e. the cause) from the prescribed temperature (i.e. the effect) which constitutes an inverse heat conduction problem that is a mathematically ill-posed problem.

The group Computational Optics develops efficient numerical algorithms for the solution of this inverse heat conduction problem, which enables the calculation of specific intensity distributions for a broad range of application. Especially temperature dependent thermophysical and optical material properties as well as complex geometries are taken into account.

Our close cooperation with the Fraunhofer Institute for Laser Technology guarantees a application-oriented realization. Thus, the developed methods have already been validated experimentally for the applications of laser hardening or laser-based softening of high-strength steels.

 
 

Further research interests

Wave-optical simulation of an illumination scenery with two CDs Copyright: © RWTH TOS Result of a wave-optical simulation of an illumination scenery with two CDs

Additional research topics of the Computational Optics group are:

  • the realization of an algorithmic resolution increase in imaging applications through ptychography.
  • the potential analysis of optical neural networks for process monitoring and beam shaping.
  • the development of wave-optical simulation tools.
  • t he evaluation of quantum algorithms for problems in optics design and photonic production.