Ms. Katharina Brezing Profile

Katharina Brezing

at Hochschule Pforzheim

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Publications (2)

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Proceedings Article | 14 March 2023 Presentation + Paper

RGB LED matrix display for augmented driving for higher traffic safety

Karlheinz Blankenbach, M. Eisenhardt, K. Brezing, Steffen Reichel

Proceedings Volume 12443, 1244302 (2023) https://doi.org/10.1117/12.2648294

KEYWORDS: Diffusers, Light emitting diodes, Visualization, LED displays, Safety, Heads up displays, Autonomous driving, Prototyping

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Augmentation in manually driven vehicles can raise traffic safety significantly. The most ergonomic (eyes-on-the-road, no refocusing) solution is AR-HUD but the FOV is limited today to 10° by 5°. Transparent displays in the windshield (eyes-on-the-road, refocusing required) are costly (replacement) and hardly meet legal requirements for transparency. The cheapest solution is video-AR on dashboard displays (eyes-off-the-road, refocusing required). We report on a new approach for augmentation as compromise between ergonomics and cost: An eight-line RGB matrix display to be mounted on top of the dashboard at the bottom of the windshield. It spreads from pillar-to-pillar (150 cm, 150 x 8 pixel, RGB LED) and therefore enables augmented information along the whole windshield. In consequence, it needs less eyes-off-the road and refocusing and is a very ergonomic add-on for video-AR. We started with a single line pixelated light guide in a seating buck to measure and to evaluate the required luminance (⪆3,300 cd/m²), RGB luminance ratio (35:50:15) and perception of information from night to blinding sunlight. We optimized the RGB LED display by testing and measuring various diffusers at different distances to the LEDs for an optimum combination of sharpness and pixelation. Image quality and content such as the visualization of actual speed (including color-coding), warnings (e.g. slippery), navigation, and comfort functions (e.g. incoming call, beat mode) were evaluated by subjects via online survey and in our seating buck. The display was rated as being very helpful with significantly reduction in time for grasping the information.

Proceedings Article | 12 September 2021 Presentation + Paper

Evaluation of luminance vs. brightness for automotive RGB LED light guides in autonomous cars

Karlheinz Blankenbach, Katharina Brezing, Steffen Reichel

Proceedings Volume 11874, 1187406 (2021) https://doi.org/10.1117/12.2599859

KEYWORDS: RGB color model, Waveguides, Sun, Light emitting diodes, Light sources and illumination, Visualization, Color vision, LED displays, Calibration, Electronic filtering

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Colored light for visual communication in cars at daylight conditions has recently started: A light guide with RGB LEDs is placed at the bottom of the windshield. Usage is safe visualization of autonomous mode and warnings beside e.g. wayfinding support, directional highlighting and turn signals. Today’s white luminance of light guides is about 1,250 cd/m² for daylight with a RGB luminance ratio of typically 28:65:7. A new proposal from an OEM requires the same luminance just for blue. Therefore we started an evaluation with different aspects as basis: The luminance of blue is low due to V(λ) curve but its color perception is high by Color Matching Functions, the lightness L* (perceived brightness) is related to luminance L by L* ~ L^0.44 and the RGB luminance ratio of traffic signs (acc. EN12966) is 35:50:15. We designed our car mock-up for a white luminance of 13,000 cd/m² using a RGB LED stripe reaching 1,500 cd/m² for blue. The surrounding simulates night to sunlight conditions with additional 100,000 cd/m² blinding sun. We tested 18 subjects (pandemic restrictions). The luminance of blue for “annoying” (= safe recognition) reached 900 cd/m² (sunlight + blinding). Additionally, the subjects had to adjust two neighboring colors to the same brightness or judge (brighter, same, and darker) for different colors. Our survey resulted in a reasonable luminance of 500 cd/m² for blue (emphasized by blinking) and a RGB luminance ratio of 35:50:15. The portion of blue is nearly doubled which forces a redesign of today’s automotive RGB LEDs.

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