HEAD-UP DISPLAYS

1. INTRODUCTION

The head-up display (HUD) creates a new form of presenting information by enabling

a user to simultaneously view a real scene and superimposed information without large

movements of the head or eye scans. HUDs have been used for various applications such as

flight manipulation, vehicle driving, machine maintenance, and sports, so that the users

improve situational comprehension with the real-time information. Recent downsizing of the

display devices will expand the HUD utilization into more new areas.

The head-mounted display (HMD) has been used as a head-mounted type of HUDs

for wearable computing that gives user situational information by wearing a portable

computer like clothes, a bag, and a wristwatch. A computer has come to interact intelligently

with people based on the context of the situation with sensing and wireless communication

systems.

1.1 HISTORY

The first HUDs were derived from static gun sight technology for military fighter aircraft.

Rudimentary HUDs projected a "pipper" to aid aircraft gun aiming. As HUDs advanced,

more (and more complex) information was added. HUDs soon displayed computed gunnery

solutions, using aircraft information such as airspeed and angle of attack, thus greatly

increasing the accuracy pilots could achieve in air to air battles.

HUD technology was next advanced in the Buccaneer, the prototype of which first flew on

30 April 1958. The aircraft's design called for an attack sight that would provide navigation

and weapon release information for the low level attack mode.

There was fierce competition between supporters of the new HUD design and supporters of

the old electro-mechanical gun sight, with the HUD being described as a radical, even

foolhardy option. The Air Arm branch of the Ministry sponsored the development of a

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Strike Sight. The Royal Aircraft Establishment (RAE) designed the equipment, it was built

by Cintel, and the system was first integrated in 1958. The Cintel HUD business was taken

over by Elliott Flight Automation and the Buccaneer HUD was manufactured and further

developed continuing up to a Mark III version with a total of 375 systems made; it was

given a `fit and forget' title by the Royal Navy and it was still in service nearly 25 years

later. BAE Systems thus has a claim to the world's first Head Up Display in operational

service.[2]

In the United Kingdom, it was soon noted that pilots flying with the new gun-sights were

becoming better at piloting their aircraft.[citation needed] At this point, the HUD expanded

its purpose beyond weapon aiming to general piloting. In the 1960s, French test-pilot

Gilbert Klopfstein created the first modern HUD and a standardized system of HUD

symbols so that pilots would only have to learn one system and could more easily transition

between aircraft. The modern HUD used in instrument flight rules approaches to landing

was developed in 1975.[3] Klopfstein pioneered HUD technology in military fighter jets

and helicopters, aiming to centralize critical flight data within the pilot's field of vision.

This approach sought to increase the pilot's scan efficiency and reduce "task saturation" and

information overload.

Use of HUDs then expanded beyond military aircraft. In the 1970s, the HUD was

introduced to commercial aviation,[4] and in 1988, the Oldsmobile Cutlass Supreme

became the first production car with a head-up display.[5]

Until a few years ago, the Embraer 190 and Boeing 737 New Generation Aircraft (737-

600,700,800, and 900 series) were the only commercial passenger aircraft available with

HUDs. However, the technology is becoming more common with aircraft such as the

Canadair RJ, Airbus A318 and several business jets featuring the displays. HUDs have

become standard equipment on the Boeing 787.[6] Furthermore, the Airbus A320, A330,

A340 and A380 families are currently undergoing the certification process for a HUD.[7]

HUDs are also added to the Space Shuttle orbiter.

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2. PRINCIPLE

Head-up display have now become so compact and lightweight that an emerging

use is for displaying information to workers on site locations such as power stations,

airports and events. A new breed monocular head up displays (HUD) cater for this

application. These displays are discreet and easy to use and are being used in the field by

engineers, security and police forces. Head-up display utilizes a low powered laser device

to literally project a laser image onto the viewer's retina. We are aware of the harmful

effects of the laser and may be wondering about the safety of aiming laser light directly

into the eye. To ensure that its device is safe, Micro vision applied rigorous safety

standards from the American National Standards Institute, Washington, D.C., and the

International Electro technical Commission, Geneva, derived from years of studying the

effects of light on the eye. Laser light can be harmful because its beam is intense, capable

of concentrating its power in a tiny area of incidence. This could be a problem if a fixed

beam-as opposed to a scanned beam-were allowed to dwell on just one spot. We ensure

that the retina is never overwhelmed by limiting the power of the laser light entering the

eye to about a thousandth of a watt and using a high-reliability interlock circuit that turns

on the laser only when the beam is scanning. Furthermore, because this very low-power

light is continuously scanned onto the retina, its energy is dispersed over an area hundreds

of thousands, of times larger than a single spot of an incident beam. Head-Up Display,

also known as a Heads-Up Display or simply HUD, is any type of display that presents data

without blocking the user's view. In civil aviation the HUD is known as a Head-Up

Guidance System (HGS).

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2.1 TYPES

• Fixed- In which the user looks through a display element attached to the

airframe or vehicle chassis. Commercial aircraft and motor vehicle HUDs are of this

type. The system determines the image to be presented depending on the orientation of

the vehicle. The size and weight of the display system can be much greater than in the

other type which is:

• Helmet-mounted, or head-mounted-In which the display element moves

with the user's head. This requires a system to precisely monitor the user's direction of

gaze and determine the appropriate image to be presented. The user must wear a helmet

or other headgear which is securely fixed to the user's head so that the display element

does not move with respect to the user's eye. Such systems are often monocular. One

use of this type of HUD is in the AH-64 Apache and in the Norwegian F-16 Fighting

Falcons.

2.2 CHARACTERISTICS

• The display element is largely transparent, meaning the information is

displayed in contrasting superposition over the user's normal environment

• The information is projected with its focus at infinity. Doing this means

that a user does not need to refocus his eyes (which takes several tenths of a second)

when changing his attention between the instrument and the outside world.

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The company uses microelectromechanical system (MEMS) devices to scan the

beams back and forth and, where appropriate, to mix different colors to produce white

light. Because the beam sweeps over the retina instead of dotting it, lines need not be

serrated and images need not be grainy. Bright as the picture will seem to the naked eye,

it will consume barely a microwatt, potentially saving hugely on battery power. And, by

sending light only where it's needed, the system can keep nosy neighbors in adjacent

airline seats from snooping on your work (or play). With a sufficiently inconspicuous

eyepiece, one might even feign attention to a speech or lecture while, in fact, watching

television.

2.3 RESOLUTION, COLOUR DEPTH AND BRIGHTNESS

The overriding design factor for these type of Head-up display is their

compactness which means that the resolution of these models is not yet as high as some

of the virtual reality Head-up display. Older HUD's offers resolutions starting from

320x240 (qVGA) up to 640 x 480 (VGA) and includes true color models. They are also

available in binocular configurations to give twice the display area. Micro vision’s

Nomad has a resolution of 800 x 600 and is red monochrome. Color is not important for

many applications where content is mainly technical data and text. Micro vision’s

displays use red laser light. One of their strong points is that they are very bright and

can easily be viewed in strong sunlight Field of view (FOV) Average human vision

covers an area of about 200 degrees horizontally by 150 degrees vertically. FWD FOV

figures are typically given as diagonal FOV. That is the perceived angle from one corner

of the screen to the opposite corner.

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(a)Approx. human horizontal field-of-view (b) Approx. human vertical field-of-

view

One of the most important factors for head-up information display is that any text

or technical diagrams are clearly legible. These Head-up display are currently not

designed to immerse the user with wrap-around images but instead to provide the

equivalent of a 'floating monitor' taking up part of the user's field of view

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3. DESIGN FACTORS

There are several factors that engineers must consider when designing a HUD:

Field of vision—because the human eyes are separated, each eye receives a different

image. To prevent pilots' eyes from having to change focus between the outside world

and the display of the HUD, the display is collimated (focused at infinity). In automobiles

the display is generally focused near the distance to the bumper.

Eye box—displays can only be viewed while the viewers' eyes are within a three-

dimensional area called the head motion box or eye box. Modern HUD eye boxes are

usually about 5 by 3 by 6 inches. This allows viewers some freedom of head movement.

It also allows pilots the ability to view the entire display as long as one of their eyes is

inside the eye box.

Luminance/contrast—displays must be adjustable in luminance and contrast to account

for ambient lighting, which can vary widely (e.g., from the glare of bright clouds to

moonless night approaches to minimally lit fields).

Display accuracy—aircraft HUD components must be very accurately aligned with the

aircraft's three axes – a process called bore sighting – so that displayed data conforms to

reality typically with an accuracy of ±7.0 mill radians. In this case the word "conform"

means, "When an object is projected on the combiner and the actual object is visible, they

will be aligned". This allows the display to show the pilot exactly where the

artificial horizon is, as well as the aircraft's projected path with great accuracy. When

Enhanced Vision is used, for example, the display of runway lights must be aligned with

the actual runway lights when the real lights become visible. Bore sighting is done during

the aircraft's building process and can also be performed in the field on many aircraft.[3]

Compatibility—HUD components must be compatible with other avionics, displays, etc.

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4. WORKING

A typical HUD contains three primary components: a combiner, projector unit, and video

generation computer.

The combiner is the part of the unit located directly in front of the pilot, providing the surface

onto which the information is projected for view. Combiners can be concave or flat, and have

a special coating that reflects the monochromatic light projected onto it from the projector

unit while allowing all other wavelengths of light to pass through. On some aircraft the

combiners are easily removable (or can be rotated out of the way) by aircrew.[3]

The projection unit projects the image onto the combiner for the pilot to view. In early HUDs,

this was done using refraction, although modern HUDs use reflection. Projection units

use Tubes, light, or liquid crystal displays to project the image. Projection units can be either

below (as with most fighter aircraft) or above (as with transport/commercial aircraft)

combiners.

The computer is usually located with the other avionics equipment and provides the interface

between the HUD (i.e. the projection unit) and the systems/data to be displayed. On aircraft,

these computers are typically dual independent redundant systems. They receive input

directly from the sensors (pitot-static, gyroscopic, navigation, etc.) aboard the aircraft and

perform their own computations rather than receiving previously computed data from the

flight computers. Computers are integrated with the aircraft's systems and allow connectivity

onto several different data buses such as the ARINC 429, ARINC 629, and MIL-STD-1553.[3]

4.1 PROJECTION METHODS

The most common means by which current HUDs are implemented is to project the image

onto a clear glass optical element ('combiner'). Traditionally, the source for the projected

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image has been a Cathode Ray Tube (CRT), however newer image sources based on micro-

display technologies are now being introduced. Micro-display technologies that have been

demonstrated include Liquid Crystal Display (LCD), Liquid Crystal On Silicon (LCOS),

Digital Micro Mirrors (DMDs), Organic Light-Emitting Diode (OLED) and Laser.

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Depending on the application and cost and size requirements, we can use single

color or multiple low-power solid-state lasers, laser diodes, or LEDs as the light source.

In the case of a full-color electronic viewfinder display on a camera where low cost and

power consumption are critical, I modulated red, green, and blue LEDs produce color

pixels of varied intensities to generate a complete palette of colors and shades.

If the light source is the paint, Micro vision’s proprietary

microelectromechanical systems (MEMS) biaxial scanner is the brush that applies the

image to the retina. The scanner's main component is a minor 1.5 millimeters in

diameter that rapidly sweeps the light beam horizontally to position the pixels in a row,

also moving the beam downward, to draw successive rows of pixels. This process

continues until an entire field of rows has been placed and a full image appears to the

user-quite similar to the process in a regular cathode-ray television, in which the

magnetic deflection coils direct the electron beam to scan the phosphor-coated screen.

But while a conventional display can create jagged edges on images because the pixels

are fixed onto screen hardware, a scanned-beam display has no hard pixels: the

continuously scanning beam creates a much smoother image.

For applications in which the scanned-beam display is to be worn on the head or held

closely to the eye, we need to deliver the light beam into what is basically a moving

target: the human eye. Constantly darting around in its socket, the eye has a range of

motion that covers some 10 to 15min. One way to hit this target is to focus the scanned

beam onto an optical element called an exit pupil expander. When light from the

expander is collected by a lens, and guided by a mirror and a see-through monocle to the

eye, it covers the entire area over which the pupil may roam. For applications that require

better image quality using less power, we can dispense with the exit pupil expander

altogether either by using a larger scan mirror to make a larger exit pupil or by actively

tracking the pupil to steer light into it.

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Display using CRT

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5. ADVANTAGES

The head-up display is highly efficient with respect to power consumption,

requiring far less power than the postage-stamp LCD screens used commonly in today's

mobile devices. A head-up display uses about a microwatt of power. Since head-up

display displays project images directly onto the retina, they provide a sharp, clear

image regardless of external lighting conditions. Head-up displays require a fraction of

the hardware of conventional display devices, allowing for lighter and more elegant

mobile devices, in high demand for today's electronics market. Head-up display shows

strong potential to replace LCD screens in cell phones, handheld computers, handheld

gaming systems, and eventually even larger computers such as laptops

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6. APPLICATIONS

Head-Up displays were pioneered for fighter jets and later for low-flying military helicopter

pilots, for whom information overload was a significant issue, and for whom changing their

view to look at the aircraft's instruments could prove to be a fatal distraction.

HGSs have been in use in commercial aviation since the 1970s, and are now in regular use,

notably with Alaska Airlines.

Heads up displays have also been incorporated into automobiles, usually as a secondary

display for the most important information from the gauges. General Motors was the first to

put the Heads up Display into cars in 1988. These early HUD units were made by Hughes

Aircraft Corporation, a GM subsidiary. One of the first vehicles to receive a HUD was the

May 1988 Indianapolis 500's 1988 Cutlass Supreme Pacecar, as well as 50 custom

convertible pacecar replicas commissioned by GM.

Since 1988 General Motors offered the Heads Up Displays as an option on the 1989-1994

Oldsmobile Cutlass Supreme, 1989 to present Pontiac Grand Prix, and 1993 to present

Pontiac Bonneville, and more recently the Buick LeSabre, Park Avenue and Rendezvous.

During the 90's, Heads Up Displays were an option offered in Nissan models including the

Silvia family of cars.

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In 1999, Automotive HUD technology made a big quality leap with the Chevrolet

Corvette. The new Corvette, which uses a HUD to display vehicle speed, engine RPM,

Navigation and more, has proven the HUD to be one of its most popular options.

In 2000 Cadillac Premiered an optional night vision driving system as a secondary aid for

drivers. It utilizes a monitor set in the dash that displays a generated night vision image of

the road, using an infrared camera

As of 2006 BMW now features the head-up display as an option on their 5 and 7 series

vehicles, with more HUDs being anticipated from other European and Japanese OEMs.

As the doctors operate the patient, the surgeons are viewing vital patient data,

including blood pressure and heart rate. And in such procedures as the placement of a

catheter stent, overlaid images prepared from previously obtained magnetic resonance

imaging or computed tomography scans assist in surgical navigation.

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Several military units, including the U.S. Army's Stryker Brigade, are using

adaptations of the system. The commander of a Stryker, an eight wheel light-armored

vehicle, can view its onboard battlefield computer with a helmet-mounted daylight-

readable display. This enhances the commander's ability to observe the surroundings,

choose the

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Optimum path, command the vehicle, and use tactical information advantageously.

Other military applications include a series of prototype helmet-mounted displays

developed with the U.S. Army and Boeing Co. of Chicago. Currently in the initial stages

of flight-testing, the system could be a relatively inexpensive way to provide utility- and

attack-helicopter pilots with a digital display of the battle space.

Displays from both MicroOptical and 1Vlicrovision are suitable for outdoor usage

and both are capable of connecting to handheld PCs and PDAs. Microvision's Expert

Technician System includes a wearable running Windows CE.NET and is tough enough

to be used in industrial environments. MicroOptical's displays are often used with

wearable computing system. They are also available with video inputs allowing use with

DVD players or Camcorders.

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7. FUTURE PROJECTS

Fighter pilots have had it for years but Formula One drivers have only just

begun experimenting with heads-up displays, Motion Research Corporation is

developing consumer heads-up display for motorcycle and bicycle helmets

The SportVue heads-up display for motorcycles and other motion sports is on

the leading-edge of a wave of new technology for sports enthusiasts and has the

potential to change the way motion sports users acquire and benefit from

information.

Detroit - General Motors is working on a new generation of Head-Up display, with an

enhanced vision system on the entire car's windscreen that would provide drivers with

information on obstacles, even in bad weather conditions. Described as an enhanced-

vision system, the display uses sensors and cameras to detect the shape and edge of

the road and objects ahead, 'magically' projecting them onto the windscreen. Current

Head- Up display systems use only a small portion of the windscreen.

DARPA is working on glasses that will endow the user with zoom vision, various

forms of night sight, and act as a heads-up display besides. Perhaps best of all, the

proposed kit would also offer "full sphere awareness" – that is, eyes in the back of

your head. It is the goals of the DARPA Soldier Centric Imaging via Computational

Cameras (SCENICC) project.

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8. CONCLUSION

The HUD technology increases the opportunities for information presentation. Information

can not only be presented nearer to the line of sight, but also in a larger focal distance. Both

factors reduce the time for information perception. Available HUDs still have a presentation

area too small for AR, but future development might enable large scale HUDs that are fully

capable of presenting information embedded into the environment. The HUD extends the

presentation space by an additional dimension. Information now can be presented in three

dimensions. Information objects can not only be rendered in a 3D perspective shape, but also

can be placed in di erent focal depths. The fact that the information can be spatially relatedff

to the object of concern introduces new opportunities for fast and e cient informationffi

presentation but also generates new issues. Design principles from classic 2D displays are no

longer applicable in their full extend. The main reason lies in the altered motion behavior of

visualized objects. Compared to in-car display, a HUD has no static background. Instead, it

image plane lies in the outside environment which makes it moving when the car moves. As a

matter of fact, the frame of reference of objects in the HUD is di erent. An object shown in aff

way that is appears to be standing still on the ground at a certain position moves over the

HUD display.

Mapping will take on a new leash of life with augmented reality and GPS

technology. Users will be able to see a map of their current location displayed right on

top of the real thing. This will aid navigation in cities and the countryside, allowing

street names to appear on every road and virtual sign-posts to lead you to your

destination. Local information such as the nearest police or tube station could be

overlayed onto your view along with directions to the nearest cash point or taxi rank.

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9. REFERENCES

List of journals:

[1] Doshi, A.;   Shinko Yuanhsien Cheng;   Trivedi, M.M.; Lab. for Intell. & Safe

Automobiles, Univ. of California, La Jolla, CA A Novel Active “Heads-Up Display for

Driver Assistance” Systems, Man, and Cybernetics, Part B: Cybernetics, IEEE

Transactions, Feb. 2009, Volume 39, Issue 1, Pages 85 – 93.

[2] Pope, Stephen "The Future of Head-Up Display Technology". Aviation International

News, Jan. 2006.

[3] Zhang Weiguang, Li Jianchao, Lei Xinye, "Automatic Parallax Measurement Method

for Head-Up Display System" ICICTA Second International Conference on Intelligent

Computation Technology and Automation, 2009, Vol. 2, Pages 321-324.

[4] Newman, R. L. (1995). Head up displays: designing the way ahead, Avebury Aviation

[5] Weintraub, D. J., Ensing, M. (1992). Human factors issues in head-up display design:

the book of HUD (CSERIAC State-of-the-art Report), Wright-Patterson AFB, Dayton,

OH: Crew System Ergonomics Information Analysis Center

Web sites:

[6] En.wikipedia.org

[7] http://www.autoevolution.com

[8] http://www.gizmag.com

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