Glossary of Terms

Augmented Reality refers to a display in which simulated imagery, graphics, or symbology is superimposed on a view of the surrounding environment

Brightness refers to the attribute of a visual sensation by which a stimulus appears more or less intense or appears to emit more or less light.

cd/m2 - candelas per square meter. See "Luminance".

CRT (Cathode Ray Tube) refers to a vacuum tube display in which electrons from a heated cathode (an electron gun) are focused on a screen and moved by electrostatic or magnetic fields to create an image. CRTs are the main display technology used throughout the world from televisions to computer monitors.

CMOS (Complementary Metal-Oxide Semiconductor) is a major class of integrated circuits. CMOS chips include microprocessor, microcontroller, static RAM, and other digital logic circuits. The central characteristic of the technology is that it only uses significant power when its transistors are switching between on and off states. Consequently, CMOS devices use little power and do not produce as much heat as other forms of logic. CMOS also allows a high density of logic functions on a chip.

Chromatic Distortion refers to an aberration is caused by the dispersion of the lens material, the variation of its refractive index n with the wavelength of light.

Contrast refers to the ratio of the brightest part of an image versus the darkest part of an image (for example, 100:1).

Direct view display refers to a display viewed without aid of additional optics or magnification by the unaided eye of the user. The size of the image produced by the display is the actual size viewed by the user.

Display format refers to display addressability (e.g., 640 x 480), aspect ratio (e.g., 4:3), or video standard (e.g. VGA).

Emissive displays refer to a broad category of display technologies which generates its own light. Emissive display technologies include electroluminescent, field emission, plasma, vacuum fluorescent, and polymeric. In contrast non-emissive displays require a separate, external source of light (such as the backlight of a liquid crystal display).

Flat-panel display refers to video displays used in lap top computers and other devices where the monitor is desired to be as thin as possible.

HMD (Head-Mounted Display or Helmet Mounted Display) or HWD (Head-Worn Display) refers to a diverse family of viewing systems where one or more displays and sets of optics are attached to the head (head-mount display) or an accessory. For example, they can be designed into helmets, hardhats, or eyeglasses. Images can be projected into one eye (monocular) or both eyes (binocular).

Image quality refers to an objective measurement or subjective rating of the quality of a display system.

LCD (Liquid crystal display) a flat display device made up of any number of color or monochrome pixels arrayed in front of a light source or reflector. Each pixel (picture element) consists of a column of liquid crystal molecules suspended between two transparent electrodes, and two polarizing filters, the axes of polarity of which are perpendicular to each other.

LED (Light Emitting Diodes) refers to a semiconductor device which emits light when current flows through the device. These devices have a preferred current direction.

Lambertian reflectance refers to the amount of light an observer will see from the surface. The surface brightness, is the same no matter what angle they look

Luminance refers to the amount of visually effective light emitted by an extended source. Typically expressed in nits, footlamberts (fL) or candelas per square meter (cd/m2). 

Miniature display refers to those displays which are magnified by optics to enlarge the image viewed by the user. For example, a miniature display smaller than 2 inches in size may be magnified to provide a 14 inch viewing area.

Microdisplay refers to a very small electronic display device that can be suspended near the eye and viewed through magnifying optics or used with higher magnification optics to project an image.

Monochrome refers to a display that emits a single hue but may vary in intensity and saturation. For example, monochrome miniature displays used in many HMDs are typically green and are used to display symbology or sensor imagery.

Non-emissive displays refers to a broad category of displays which absorb or block light from a separate light source. Liquid crystal, electrochromatic, electrophoretic, ferroelectric, and micro-mirror displays fall in this category.

OEM is an acronym for "Original Equipment Manufacturer." OEMs manufacture components and sub-assemblies which are purchased by companies which integrate the components and sub-assemblies into final products.

OLED is an acronym for "Organic Light-Emitting Diode", a type of display which uses organic material as a diode type light emitting material.

Pixel is a contraction of "picture element" and refers to a single dot of light that is the smallest individually addressable unit of an image that can be displayed. Pixels are generally thought of as the smallest complete sample of an image.

Resolution refers to pixel density or dot pitch (measured in micrometers or millimeters). Resolution is typically referenced by Rows x Columns. Commonly used resolutions include

  • Quarter video graphics array(QVGA, 320 x 240)
  • Video graphics array(VGA, 640 x 480)
  • Super video graphics array(SVGA, 800 x 600)
  • Extended video graphics array(XGA , 1024 x 768)
  • Super extended video graphics array(SXGA , 1280 x 1024)
  • Ultra extended video graphics array (UXGA, 1600 x 1200)

USB is an acronym for "Universal Serial Bus," a serial bus standard for connecting devices.

Virtual image refers to an image that appears to be suspended in front of the eye, that is, a representation of an actual object (source) formed by diverging rays of light which seem to originate from the image, but in reality do not cross at that position.

Virtual reality ("VR") or artificial reality refers to an electronic system which is designed to create a simulated environment around the viewer. Such as system must be interactive with the user to be considered true VR.