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Military aircraft specific applications[edit]
FA-18 HUD while engaged in a mock dogfight
In addition to the generic information described above, military applications include weapons system and sensor data such as:
target designation (TD) indicator—places a cue over an air or ground target (which is typically derived from radar or inertial navigation system data).
Vc—closing velocity with target.
Range—to target, waypoint, etc.
Launch Acceptability Region (LAR)—displays when an air-to-air or air-to-ground weapon can be successfully launched to reach a specified target.
weapon seeker or sensor line of sight—shows where a seeker or sensor is pointing.
weapon status—includes type and number of weapons selected, available, arming, etc.
VTOL/STOL approaches and landings[edit]
During the 1980s, the military tested the use of HUDs in vertical take off and landings (VTOL) and short take off and landing (STOL) aircraft. A HUD format was developed at NASA Ames Research Center to provide pilots of V/STOL aircraft with complete flight guidance and control information for Category III C terminal-area flight operations. This includes a large variety of flight operations, from STOL flights on land-based runways to VTOL operations on aircraft carriers. The principal features of this display format are the integration of the flightpath and pursuit guidance information into a narrow field of view, easily assimilated by the pilot with a single glance, and the superposition of vertical and horizontal situation information. The display is a derivative of a successful design developed for conventional transport aircraft.[14]
Civil aircraft specific applications[edit]
The cockpit of NASA's Gulfstream GV with a synthetic vision system display. The HUD combiner is in front of the pilot (with a projector mounted above it). This combiner uses a curved surface to focus the image.
The use of head-up displays allows commercial aircraft substantial flexibility in their operations. Systems have been approved which allow reduced-visibility takeoffs, and landings, as well as full Category III A landings and roll-outs.[15][16][17] Studies have shown that the use of a HUD during landings decreases the lateral deviation from centerline in all landing conditions, although the touchdown point along the centerline is not changed.[18]
Enhanced flight vision systems[edit]
In more advanced systems, such as the FAA-labeled Enhanced Flight Vision System,[19] a real-world visual image can be overlaid onto the combiner. Typically an infrared camera (either single or multi-band) is installed in the nose of the aircraft to display a conformed image to the pilot. EVS Enhanced Vision System is an industry accepted term which the FAA decided not to use because "the FAA believes [it] could be confused with the system definition and operational concept found in 91.175(l) and (m)"[19] In one EVS installation, the camera is actually installed at the top of the vertical stabilizer rather than "as close as practical to the pilots eye position". When used with a HUD however, the camera must be mounted as close as possible to the pilots eye point as the image is expected to "overlay" the real world as the pilot looks through the combiner.
"Registration," or the accurate overlay of the EVS image with the real world image, is one feature closely examined by authorities prior to approval of a HUD based EVS. This is because of the importance of the HUD matching the real world.
While the EVS display can greatly help, the FAA has only relaxed operating regulations[20] so an aircraft with EVS can perform a CATEGORY I approach to CATEGORY II minimums. In all other cases the flight crew must comply with all "unaided" visual restrictions. (For example if the runway visibility is restricted because of fog, even though EVS may provide a clear visual image it is not appropriate (or actually legal) to maneuver the aircraft using only the EVS below 100' agl.)
Synthetic vision systems[edit]
A synthetic vision system display
HUD systems are also being designed to display a synthetic vision system (SVS) graphic image, which uses high precision navigation, attitude, altitude and terrain databases to create realistic and intuitive views of the outside world.[21][22][23]
In the SVS head down image shown on the right, immediately visible indicators include the airspeed tape on the left, altitude tape on the right, and turn/bank/slip/skid displays at the top center. The boresight symbol (-v-) is in the center and directly below that is the flight path vector symbol (the circle with short wings and a vertical stabilizer). The horizon line is visible running across the display with a break at the center, and directly to the left are numbers at ±10 degrees with a short line at ±5 degrees (the +5 degree line is easier to see) which, along with the horizon line, show the pitch of the aircraft. Unlike this color depiction of SVS on a head down primary flight display, the SVS displayed on a HUD is monochrome – that is, typically, in shades of green.
The image indicates a wings level aircraft (i.e. the flight path vector symbol is flat relative to the horizon line and there is zero roll on the turn/bank indicator). Airspeed is 140 knots, altitude is 9450 feet, heading is 343 degrees (the number below the turn/bank indicator). Close inspection of the image shows |
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A head-up display or heads-up display[1]—also known as a HUD—is any transparent display that presents data without requiring users to look away from their usual viewpoints. The origin of the name stems from a pilot being able to view information with the head positioned "up" and looking forward, instead of angled down looking at lower instruments.
Although they were initially developed for military aviation, HUDs are now used in commercial aircraft, automobiles, computer gaming, and other applications.
Contents [hide]
1 Overview
1.1 Types
1.2 Generations
2 History
3 Design factors
4 Aircraft
4.1 Displayed data
4.2 Military aircraft specific applications
4.3 VTOL/STOL approaches and landings
4.4 Civil aircraft specific applications
4.5 Enhanced flight vision systems
4.6 Synthetic vision systems
5 Automobiles
6 Developmental / experimental uses
7 See also
8 References
9 External links
Overview[edit]
HUD mounted in a PZL TS-11 Iskra jet trainer aircraft with a glass plate combiner and a convex collimating lens just below it
A typical HUD contains three primary components: a projector unit, a combiner, and a video generation computer.[2]
The projection unit in a typical HUD is an optical collimator setup: a convex lens or concave mirror with a Cathode Ray Tube, light emitting diode, or liquid crystal display at its focus. This setup (a design that has been around since the invention of the reflector sight in 1900) produces an image where the light is parallel i.e. perceived to be at infinity.
The combiner is typically an angled flat piece of glass (a beam splitter) located directly in front of the viewer, that redirects the projected image from projector in such a way as to see the field of view and the projected infinity image at the same time. Combiners may have special coatings that reflect the monochromatic light projected onto it from the projector unit while allowing all other wavelengths of light to pass through. In some optical layouts combiners may also have a curved surface to refocus the image from the projector.
The computer provides the interface between the HUD (i.e. the projection unit) and the systems/data to be displayed and generates the imagery and symbology to be displayed by the projection unit .
Types[edit]
Other than fixed mounted HUDs, there are also head-mounted displays (HMDs). Including helmet mounted displays (both abbreviated HMD), forms of HUD that fea |
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A vector monitor or vector display is a display device used for computer graphics up through the 1970s. It is a type of CRT, similar to the oscilloscope. In a vector display, the image is composed of drawn lines rather than a grid of glowing pixels as in raster graphics. The electron beam follows an arbitrary path tracing the connected sloped lines, rather than following the same horizontal raster path for all images. The beam skips over dark areas of the image without visiting their points.
Some refresh vector displays use a normal phosphor that fades rapidly and needs constant refreshing 30-40 times per second to show a stable image. These displays such as the Imlac PDS-1 require some local refresh memory to hold the vector endpoint data. Other storage tube displays such as the popular Tektronix 4010 use a special phosphor that continues glowing for many minutes. Storage displays do not require any local memory. In the 1970s, both types of vector displays were much more affordable than bitmap raster graphics displays when a megapixel computer memory was still very expensive. Now, raster displays have displaced nearly all uses of vector displays.
Vector displays do not suffer from the display artifacts of aliasing and pixelation. But they are limited in that they can display only a shape's outline (advanced vector systems could provide a limited amount of shading). Text is crudely drawn from short strokes. Refresh vector displays are limited in how many lines or how much text can be shown without refresh flicker. Irregular beam motion is slower than steady beam motion of raster displays. Beam deflections are typically driven by magnetic coils, and those coils fight against rapid changes to their current.
Notable among vector displays were Tektronix large-screen computer terminals that used direct-view storage CRTs. Storage meant that the display, once written, would persist for several minutes. (The CRT had at least one flood gun, and a special type of display screen, more complicated in principle than a simple phosphor.) But that permanent image could not be easily changed. Like an Etch-a-Sketch, any deletion or movement required erasing the entire screen with a bright green flash, and then slowly redrawing the entire image. Animation was not practical.
Vector displays were used for head-up displays in fighter aircraft, because of the brighter displays that can be achieved by moving the electron beam more slowly across the phosphors. Brightness is critical in this application because the display must be clearly visible to the pilot in direct sunlight.
A free software Asteroids-like video game played on an oscillograph configured in X-Y mode
Vector monitors were also used by some late-1970s to mid-1980s arcade games such as Asteroids.[1] Atari used the term Quadrascan to describe the technology when used in their video game arcades.
Hewlett-Packard made a large-screen fast vector monitor, which they called an X-Y display. It used a wide-angle electrostatically-deflected CRT that was about as compact as a magnetic-deflection CRT. Instead of the deflection plates of a typical CRT, it had a unique structure they called an electrostatic deflection yoke, with metallized electrodes inside a glass cylinder.
Color displays[edit]
Some vector monitors are capable of displaying multiple colors, using either a typical shadow mask RGB CRT, or two phosphor layers (so-called "penetration color").
Atari used the term Color Qu |
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