# Digital Media Concepts/Commercial Head-up displays

A head-up display, or HUD, is a display that can be seen without lowering the eyes or looking away from where a person would usually look, typically by projecting onto a windshield or other piece of glass. HUDs are typically used in military aircraft, but more recently have seen use in civilian applications such as automobiles, glasses, and commercial airliner applications.

## Overview

A HUD is typically made up of three parts, the computer that creates the image, called the symbol generator, the projector unit, and the combiner, a semi transparent piece of glass which focuses the image so it can be viewed with refocusing a person's eyes.
The Symbol generator condenses information from a computer and converts it into quick easy to understand symbols to be projected to the consumer.
The projection unit is typically a display focused onto a lens or mirror so as to collimate the light, or change the focal point to infinity. This will help the user be able to focus on both the displayed image and the user's surroundings at the same time.
The combiner is a flat piece of angled see-through material, typically glass, which is positioned in such a way as to allow the user to view the information without moving their head from it's typical field of view.

### Head mounted displays

The other type of commonly available HUD is the head mounted display, or HMD, which features a display that moves with the user's head. This is the most common personal use HUD, while regular HUDs are mainly used in vehicles. HMDs that use the traditional HUD method of projecting a display are called optical see-through, but some HMDs use a method called video see-through, which will mix computer generated image with video of the real world, and display it to the user. These methods are usually called augmented reality or mixed reality.

### Generations

HUDs have 4 differing generations of technology.
* First generation. Uses a cathode ray tube display to project an image onto a screen coated in phosphor, which can degrade over time.
* Second generation. Uses an LCD screen to display an image, which uses far less electricity and doesn't degrade over time.
* Third generation. Uses optical waveguides, which guide waves in the optical spectrum to project an image directly into the combiner.
* Fourth generation. Uses a scanning laser, or a directed laser, to project images onto any clear medium.

## Automotive use

In automobiles head-up displays are typically used to present the driver with whatever information they might need on the road, such as speedometer, tachometer, and navigation. Pioneer has also released a more advanced version that projects traffic and weather conditions in front of the driver, using augmented reality to deliver information to the driver. These systems are becoming increasingly cheaper, however right now they are only cost effective enough to be provided as dealer installed options for most cars. Helmets with HUDs for use on motorcycles are also becoming increasingly common, falling under the head mounted display category

## Personal use

HMDs for regular use are becoming more common. HUDs for everyday use like the Google Glass or Vuzix Star 1200 can display crucial information such as the weather conditions and navigation, take pictures, and connect to a user's phone. More specialized things such as the Alpine MOD ski goggles are being developed, which will display information such as speed, elevation, and track people you are skiing with.

## Development

Many types of HUD systems are in development, from specialized applications such as a HMD integrated into a scuba mask, to more everyday applications, such as a more affordable personal HUD. Furthering of the technology itself is also being developed, with a system that displays the HUD directly onto the user's retina using virtual retina display technology being researched.