Advanced optical supervision of automotive displays for highest safety levels

Camera-Monitor-Systems (CMS) for mirror replacements such as rear-view are becoming increasingly important for vehicles. Such systems must meet high safety requirements like non-erroneous reproduction and short latency. Supervision today only covers interface data and power supply. It is assumed that the display convert the digital data properly to optical output without any failure. This was our motivation to go further: We have successfully developed and evaluated advanced optical safeguarding methods of displays using photodiodes or a camera. Several photodiodes are mounted below the cover glass and acquire the light emission of the display through waveguide effect. The photodiodes measure the weighted integral of many pixels, so a "sensitivity map" was created using reference images. A target value for each photodiode is calculated from the RGB input data and correlated with the actual measurement. The ultimate method is to capture the display output using a camera and to compare the reproduced image with the target content. The camera image must be corrected for various effects such as distortions, Moiré, gamma and reflections of ambient light. As the reproduced GUI is known, several ROIs are defined and supervised modularly e.g. the video image is segmented and its histograms are compared with the original CMS camera data. Our methods provide a significant step towards "light-to-light" monitoring of CMS from camera input to display output. This enables functional safety for commercial monitors of remote operators for Level 5 autonomous cars in case of failures.