Reference Project

Developing optics for a rain light sensor

The French automotive supplier Vale was looking for a partner to develop the optics for a rain light sensor. The decisive factor in choosing Helbling was the range of competences we have in this area:

solid knowledge and experience in plastic optics for high-volume production (including concept, optics design, optical simulation, optical analyses down to advising on production questions)

experience with cost-down projects (cost reduction)

specific knowledge in the field of optics design
- customizing optical freeform surfaces for an extremely wide-  angle sensitivity    

- analysis and reduction of scattered light
- optical design with LightTools and high performance computing

optimizing suitability for injection moulding and mass production (several million/year), reducing reject rate

evaluation of optoelectronic components


Key Figures

  • The rain light sensor combines the following sensor functions:
    - rain sensor to identify raindrops on the windshield
    - ambient light sensor to measure ambient brightness
    - forward sensor to measure brightness ahead of the
    - solar sensor to measure sun position


  • The optics of all the sensors are integrated into a single component and are implemented with a total of 27 optical surfaces: 5 freeform surfaces, 4 toroidal surfaces, 8 aspherical surfaces, 10 prisms
  • The sensor is optimized for series production of several million units/year
  • The sensor can be used for all standard types of windshield with a thickness of 3-6 mm

Our Contribution

  • Concept development, feasibility analysis
  • Design, calculation and optimization of optical surfaces
  • Optical simulations, tolerance analysis, scattered light analyses
  • Production oriented design of optics in 3D CAD
  • The project was handled in several phases:
    - concept development
    - optical development and calculation
    - adaptation of optics to new customer specifications
    - industrialization


  • The sensor is produced in large volumes
  • The sensor is installed in Audi and VW vehicles, among others
  • A new generation is currently in development


Dr. Johannes Eckstein

Hubstrasse 24
9500 Wil

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