August 26, 2016

Heads up! Here come the HUDs
By James Farell, Director of Mechanical, Display and Optical Engineering,
Visteon



Today’s travelers can feel more like pilots than drivers when they sit behind the wheel. They find themselves in a cockpit with an array of digital gauges and navigation systems, and increasingly they are enjoying the benefits of a head-up display, or HUD.

A HUD consists of a picture generation unit, a series of mirrors, and either a transparent combiner screen or the windshield itself to project information directly in front of the operator’s eyes. The first HUDs evolved from World War II-era reflector sights in fighter aircraft and the technology made its way to automobiles in the 1988 Oldsmobile Cutlass Supreme.

Today’s HUD displays information above the dashboard, such as speed, turn indicators, navigation data and the current radio station. It allows drivers to keep their eyes on the road without having to constantly shift their focus between the road and the instrument panel. HUDs project only the most important information that the driver needs at the time, thereby avoiding unnecessary distractions.

Early HUDs employed a monochrome vacuum fluorescent display that was not customizable. Today’s more advanced HUDs often use TFT (thin-film transistor) LCD (liquid crystal display) screens, like those found in some smartphones and flat-screen TVs, with an LED (light emitting diode) backlight to generate a very bright image.

HUD systems fall into two main classes: combiner and windshield.  A combiner HUD uses a screen to reflect an image to the driver, while a windshield HUD has images projected directly off the windshield. In both categories, a virtual image appears beyond the surface of the reflector, helping the eyes maintain focus on both the data and the roadway.

Head-up displays can be tailored for all markets, reflecting the variety and advancements that have been made with this technology.
  • The entry-level HUD, designed for emerging markets, uses a passive TFT LCD or vacuum fluorescent system and a combiner with extremely high-quality optics, but with a relatively narrow field of view. This HUD often uses a mechanical, manual tilting screen, rather than the automatic or motor-driven covers available in higher-level HUDs.
  • The next step up is the low-end HUD, which is considerably brighter and offers a 4.5 x 1.5 degree field of view. With an active-matrix TFT LCD screen for sharper colors, a wider field of view and faster response, it employs simplified kinematics with a combiner that rotates down to lie flat when not in use.
  • The mid-level HUD, for the midrange automotive sector, also has a 4.5-by-1.5 degree field of view but a more complex combiner that completely retracts with a flap that covers it, for a more seamless appearance. It is about 70 percent brighter than the low-end HUD.
  • The high-end HUD is even brighter, with a larger TFT screen that offers a very wide 6-by-2.5 degree field of view. Its complex kinematics system incorporates a two-piece flap for efficient packaging, and the combiner screen can both shift and rotate.
  • The windshield HUD system, which uses no separate combiner but projects data via virtual images in front of the windshield. Its optics are more complex and its cost is higher than the other systems. While the same combiner HUDs can be designed into different positions and locations in different types of vehicles, windshield HUDs must be designed for a specific windshield and are not as adaptable.





Drivers in Asia and Europe, and to a lesser degree in North America, have shown great interest in HUD systems. Sales are growing 30-40 percent annually, and their attraction is expected to increase now that as many as five types of HUDs are available for various levels of vehicles.

The next generation of HUD will offer an augmented reality system with a very wide field of view and an image that can seem to project right onto the roadway. Its information can overlay what the driver sees in the real world -- a pedestrian ready to cross the street, a stop sign or an exit ramp, for instance. Virtual reality HUDs are expected to begin appearing in 2021 vehicles.

When autonomous driving becomes the norm, occupants may be using HUD systems during automated driving periods for videoconferences, rather than phone calls. HUD technology has virtually no limits on what can be displayed. The task of the auto industry is to ensure that HUDs continue to add to safety by reducing driver distractions while also helping prepare for the day when eyes-off-the-road driving will transition to eyes-on-the-screen activities.


Jim Farell leads Visteon’s technology development for all display products, including head-up displays, center information displays, and optics for displays and instrument clusters. During his 24 years at Visteon and Ford, Jim has led teams delivering a diverse portfolio of electronics products including Visteon’s first commercial infotainment platform and first V2X platform. He has a bachelor’s degree from the GMI Engineering and Management Institute, and a master’s in electrical engineering from Stanford University.

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