A heads-up display (HUD) is a transparent or miniaturized display technology that does not require users to shift their gaze from where they are naturally looking.
A HUD should not obstruct the user's view. This is typically achieved by the use of projected or reflected transparent displays in line-of-sight. However, with display miniaturization, non-transparent but unobtrusive screens can provide similar functions.
Some of the earliest HUDs were used in military vehicles to assist in navigation and targeting. The first generation of that type of HUD used reflected CRT display. The second generation used solid-state light sources like LED to back-light LCD projection – this is the technology commonly used in commercial aircraft. The third generation uses wave-guided optics. The forth uses scanning lasers to project all types of images and video.
Google Glass is the first widely-available consumer-market personal HUD. Glass enables one to perform computing, communication and navigational tasks with a voice interface. In voice search, for example, the user asks Glass verbally for whatever he would type into Google.
In its tiny form factor, Google Glass features a 640 x 360 display, a camera that takes 5MP stills and has 720p video capability, bone-conducting audio speakers and 16GB of flash memory. The device's battery reportedly provides about a day of life. Like many other personal HUDs, Glass is made to work paired with a smartphone which may conduct some of the more intense computations and communication.
Taiwan-based Oculon Optoelectronic is developing a similar product, Oculon Smart Glasses, with a more powerful CPU, a high-definition display and longer battery life. Apple, Vuzix and Baidu also have patents for similar devices filed.
Other HUDs with similar features and wireless abilities exist. Recon Instrument's Mod, Snow and Jet glasses and Oakley's Airwave, for example, are optimized for various activities including sports and medical care. These HUDs include GPS, multiple-axis sensors, altitude and barometric pressure measurement. Sports-optimized HUDs display relevant information like speed, altitude, jump height, athletic power output and heart rate. Other functions include things like range finding and displaying a preview of a race or golf course.
Garmin has released a $130 car-based HUD that works in conjunction with a smartphone for a projected display on the windshield.
See a demo of Oakley's Airwave HUD: