Combiner approach makes head-up displays affordable

June 12, 2014 // By Christoph Hammerschmidt
With a new automotive head-up display (HUD) type, Bosch departs from earlier implementation types: The 'Combiner' type is smaller and significantly more cost-effective than earlier solutions. Though the system has been developed along with BMW, it could soon appear in small cars from other manufacturers.

Bosch's new combiner HUD blends the data displayed with the scenery in a way that it appears as a virtual image in a distance of about 2 metres in front of the driver. In contrast to standard HUDs which project the virtual image to the windscreen, the combiner HUD utilises a small plastic screen between the steering wheel and the windscreen. Thus, the system is decoupled from the vehicle geometry which allows the tier one to offer it also to other manufacturers; it also enables the product to benefit from economies of scale: If the volume is higher, the average sales price can be lowered. This in turn could make it attractive for other manufacturers to integrate the system into compact and subcompact cars. "There is no contract that keeps us from selling it to other OEMs" a Bosch spokesperson said. "All the customer needs to do is to provide the space required in front of the cockpit".

In any case, the system has been co-developed with BMW. For this reason, it will first be available in vehicles of the Bavarian brand as well as in the new Mini Hatch.

The head-up display depicts navigation information and the vehicle's current speed. In addition, the driver sees current speed limits and other local traffic regulations, provided optionally by a camera-based traffic sign recognition system.

The challenge with designing a combiner HUD is that the tolerance of the front surface has to meet extraordinarily tight specifications. In particular, its edge is shaped in a way that it cannot be detected visually. Thus it creates the impression of seamlessly blending the information depicted with the background.

The light signal is deflected by a series of folding mirrors and projected to the combiner screen which in turn projects the image into the so-called eye box - the area where the eyes of the drivers are located. Implemented as a self-contained module, the HUD will