The benefits of head-up displays (HUD) are proven for various applications. Today’s automotive HUDs 
show mostly operational data. This paper discusses requirements of augmented reality (AR) HUDs

Blankenbach, K.

Belarusian State University of Informatics and Radioelectronics Repository

0-13Augmented reality head-up displays: from requirements to solutionsK. Blankenbach Pforzheim University, GermanyAbstractThe benefits of head-up displays (HUD) are proven for various applications. Today’s automotive HUDs show mostly operational data. This paper discusses requirements of augmented reality (AR) HUDs.1. IntroductionMany modern cars are equipped with HUDs visualizing mostly speed and directions (Fig. 1 left). Those HUDs have typically a field of view (FOV) of about 8° by 3° (h x v). They base on a projection system using small displays, curved mirrors and a combiner in the windshield [1]. AR-HUDs (Fig. 1 right) will provide more benefits for manual (wayfinding) and autonomous driving (building trust). They require new techniques due to large FOV.Today's HUD Future: AR-HUDFigure 1: From today’s HUD with small field of view (FOV, left) towards AR-HUDs (right) with large FOV. Sources: BMW, MERCEDES, PIONEER2. Considerations on AR-HUD Field of ViewThe useful AR distance and FOV depends on the “amount” of augmentation and the traffic scenario. The basic parameters for the vertical FOVv and the distance d are visualized in Fig. 2 top:- Calculation of angles by tan(a) = h/d, where h is the height of the eye, distance d as object to eye- Minimum distance for urban traffic: d™ ~ 5 m- Maximum distance for highways: drrm ~ 80 m With these assumptions, we can calculate the vertical FOVv values from av according to Fig. 2 top:- FOVv for look-down from av™ - avmax «15°- 1° to 2° have to be added system performance.- Framing cars and annotated information require a look-up angle aviu of at least 5°. This results in a total FOVv of about 20° for highway use cases.- AR augmentation of close objects like shops and traffic signs require at first approach 20° for look­up angle aviu. This results in 40° for vertical FOV.Corresponding considerations are made for the horizontal FOVh for different scenarios, Fig. 2 bottom:- Passing a caron highway: ан» 20°, Fig. 1 right- Urban wayfinding: ан *  40°- Annotated information in cities: ан » 60°This raises the FOV (h x v) by more than one order of magnitude compared to present HUDs in series production. So new technologies are required.Vertical FOVlo o k -u p  ang le  fo r tra ffic  s ig n s . ... « v u T  L ook-dow n sn g fs= 80 m Horizontal FOVD is ta nce  d{n o t to  sca le )■ 4J‘:... i . 5  m  S tanoa rd  H U D,* f t '  -  0 FO V.§1111 0 "  F Q V H1 b  m  s s c u m y  « г д о ю е  ■ i 13 .65  mFigure 2: Visualization of geometrical conditions for AR- HUDs: Vertical (top) and horizontal (bottom) FOV and real object distance d3. Requirements and SolutionsThe optical power output rises with the FOV in approximately linear relation. Expanding from 8° to 60° (h) and 3° to 40° (v) results in 100x. The luminance of the HUD’s is calculated by^Lightsourcel HU D( 1)Tx represents transmission in the optical path and Rx for reflectance. The reflectance of holographic combiners is significantly higher (about 85%) thus enabling AR-HUDs, holographic waveguides [2] reduce their volume. The contrast ratio must exceed on bright roads:LHUPCR = ■+ 1 3:1 (2)4. SummaryAR-HUDs with a FOV larger than 40° by 10° require holographic methods and highest light output fa  readability for augmented data on bright background.5. References[1] Sako, Ketal, “Development of New Head-Up Display System Utilizing RGBW LCD and Local Dimming Backlight,” SID Symposium Digest of Technical Papers, Vol. 47, p. 680-683 (2016).[2] Richter, Petal, “Volume Optimized and Mirror- less Holographic Waveguide Augmented Reality Head-up Display, “ SID Symposium Digest of Technical Papers, Vol. 49, p. 725-728 (2018).J 1 (*t33

Augmented reality head-up displays: from requirements to solutions

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Augmented reality head-up displays: from requirements to solutions

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