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Exploring Continental's AR-HUD

Posted: 07 Aug 2014     Print Version  Bookmark and Share

Keywords:Augmented Reality Head-up Display  AR-HUD  Continental AG  human machine interface  Adaptive Cruise Control 

The Augmented Reality Head-up Display (AR-HUD) is aimed at facilitating a new form of dialogue between the vehicle and the driver. It is currently being developed by automotive supplier Continental AG. The reality of the traffic conditions as seen by the driver is extended (augmented) in the display system graphic images placed precisely into the exterior view. This is achieved through optical projection that embeds information directly into the traffic situation. This makes the Augmented Reality Head-up Display a significant enhancement of the human machine interface (HMI) in vehicles.

The AR-HUD has now reached an advanced stage of pre-production development. The demo vehicle is used on one hand to show feasibility, and on the other, it provides valuable insights for series development. Continental is planning to achieve production readiness in 2017.

Figure 1: System overview of the Augmented Reality Head-up Display.

AR-HUD: Seeing is understanding
The AR-HUD optical system enables the driver to see an augmented display of the status of driver assistance systems and the significance of this information in their direct field of view. As a new part of the human machine interface, the current, pre-production AR-HUD is already closely connected with the environmental sensors of driver assistance systems, as well as GPS data, map material, and vehicle dynamics data.

Radar sensors are integrated behind the front bumper and a CMOS mono-camera is integrated on the base of the rear view mirror. The Advanced Driver Assistance Systems (ADAS) selected as relevant for the first AR-HUD applications include Adaptive Cruise Control (ACC), route information from the navigation system, and Lane Departure Warning (LDW).

If one of the driver assistance systems detects a relevant situation, virtual graphical information in the AR-HUD makes the driver aware of this. In addition to the direct increase in safety, this form of dialogue is also a key technology for automated driving. The augmentation makes it easier for the person driving to build up trust in the new driving functions.

Two picture levels with clearly different projection distances based on two different picture generation units
In Continental's AR-HUD, two image levels are possible over different projection distances, also called the 'near' or 'status' level and the 'remote' or 'augmentation' level. The 'near' status level appears to move at the end of the engine hood in front of the driver and shows the driver selected status information such as the current speed, applicable distance restrictions like no passing zones and speed limits, or the current settings of the Adaptive Cruise Control (ACC). To be able to read this information, the driver only has to lower his eyes by about 6. The status information appears in a field of vision of size 5x 1 (corresponding to 210 mm x 42 mm) with a projection distance of 2.4 m.

Figure 2: Schematic of the projection path.

This corresponds to the virtual picture of a "conventional" head-up display, and is based on mirror optics and a picture generating unit (PGU). The latter is made up of a thin film transistor (TFT) display, the content of which is backlit using LEDs. This unit has been integrated in a compact design in the upper section of the AR-HUD module. The mirror optics enlarge the content of the display for the virtual representation. This is achieved using a curved mirror. Continental uses a carefully chosen optical design to implement two picture levels over different projection distances in the AR-HUD. Here, the respective optical paths of both levels slightly overlap internally. The optical path of the near level only uses the upper edge zone of the large AR-HUD mirror (the large asphere) without another "folding mirror." This part of the AR-HUD system resembles the state of the art technology currently integrated by Continental as a second generation HUD in factory-built vehicles.

Augmentation with cinema technology in the car
The augmentation level naturally plays the main role in the AR-HUD. It provides for the augmented representation of display symbols directly on the road at a projection distance of 7.5 m in front of the driver. The content is adapted to current traffic conditions. The contents of this remote level are generated using a new picture generating unit that Continental first presented at the IAA 2013. The graphical elements are generated with a digital micromirror device (DMD) in the same manner as digital cinema projectors. The core of the PGU is an optical semiconductor with a matrix of several hundred thousand tiny mirrors, which can be tilted individually using electrostatic fields.

The micromirror matrix is alternately lit by three coloured LEDs (red, blue, and green) in quick succession and in a time-sequential manner. The collimation (parallel direction) of the three-colour light takes place through a tilted mirror with a colour-filter function ('dichroic mirror'). These particular mirrors either allow the light to pass through or reflect it, depending on the colour. All micromirrors of this respective colour are tilted synchronously with the colour currently lit, so that they reflect the incoming light through a lens and thus depict this colour on a subsequent focusing screen as individual pixels. This happens at the same time for all three colours. The human eye "averages" all three colour pictures on the focusing screen and gives the impression of a fully coloured picture.

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