What do display industry acronyms actually mean?

Just when I think I’ve mastered the nuances of OLED, WOLED, QLED, and the rest of the X-OLED family of display technologies, I attend a conference such as SID Display Week and encounter a whole slew of new acronyms. Every industry propagates its own insider jargon and shorthand, and the display industry is particularly adept at this—it can be like alphabet soup. Here’s a quick reference guide to some of the more common display-related acronyms:

A

• AlInGaP – Aluminum Indium Gallium Phosphide. A semiconducting chemical alloy commonly used to create LEDs, typically pronounced “allan-gap”. A related acronym is AlInGaN, where the N = nitride. 

• AMOLED – Active-Matrix OLED. The most prevalent type of OLED display technology today, made using a TFT driver, which includes a storage capacitor, enabling AMOLED displays to produce high-resolution images and large display screens. See also PMOLED.

• AOI – Automated Optical Inspection. Use of optical systems such as machine vision cameras or imaging photometers to perform visual quality inspection of products such as display devices in the manufacturing process.

• AR, also AR/MR/VR – Augmented, Mixed, and Virtual Reality. AR and MR devices typically project images onto a transparent display surface allowing the user’s surrounding environment to remain visible. Virtual reality devices have opaque displays and completely enclose the user’s field of view, providing an immersive experience. See also MR, XR.

B

• BLU – Backlight unit. A light source used in common display architectures where a screen (such as an LCD) is illuminated from behind by an array of lights (such as LEDs).

C

• CCD – Charge Coupled Device. A CCD sensor is a semiconductor chip with multiple photo-sensitive sites (pixels) that are used in some cameras and vision systems to capture light (photons) and convert them to electrons, which can then be read digitally. In CCDs, electrons are collected for row of sensor pixels and read out to an amplifier at the end of the row, which converts the electrons to voltage. See also CMOS.

• CIE – The International Commission on Illumination (Commission Internationale de l’Eclairage). The organization that in 1931 developed the first mathematical system to quantify human visual perception of color. https://cie.co.at

• CIELAB – or CIE L*a*b* is a three-dimensional color space defined by the CIE in 1976. It enables accurate measurement and comparison of the color performance of different display devices. It is based on three values: L* for perceptual lightness, and a* and b* for the four unique colors of human vision: red, green, blue, and yellow.

• CMOS – Complementary Metal-Oxide Semiconductor. A CMOS sensor is a semiconductor chip with multiple photo-sensitive sites (pixels) that are used in some cameras and vision systems to capture light (photons) and convert them to electrons, which can then be read digitally. In CMOS, each sensor pixel has its own readout circuit with an amplifier that converts that pixel’s electrons to voltage.  See also CCD.

• CRT – Cathode Ray Tube. First discovered in the late 19th century, “cathode rays” are electron beams that produce an image when the electrons strike a phosphorescent surface, all encased within a glass vacuum tube. CRT displays were first commercialized in the 1930s and used for all televisions, computers, and other displays until they were overtaken by LCD display technology in the 21st century.

D

• DCI-P3 – Digital Cinema Initiatives Protocol 3. Also referred to as P3, a color space used to standardize colors used in the film industry. Advanced displays such as those use for gaming reference this color space, which is larger than sRGB.

• DLP / DLPT – Digital Light Processing Technology. A type of projection display that uses tiny mirrors to reflect light toward (an “on” pixel) or away (an “off” pixel) from a screen. 

• DPI – Dots Per Inch. A metric indicating the resolution—or point density—of a printed image. The number of dots of ink in one inch of a printed image. See also: PPI (Pixels Per Inch).

• DVST – Direct View Storage Tube. An early graphics display type based on firing electrons at a panel, similar to a CRT. It retained an image on screen, requiring a full refresh to change the image.

E

• ELD – Electroluminescent Display. Electroluminescent materials emit visible light when electrical current passes through them. An ELD is a flat-panel display (FPD) with electroluminescent material sandwiched between two conductive layers.

• EOTF – Electro-Optical Transfer Function. A mathematical function used to describe the conversion (transfer) of an electrical signal into an optical signal with a specific brightness.

• EPD – Electrophoretic Display. An electromechanical display type, commonly referred to as e-paper,. Images are created by tiny particles in microcapsules of various colors, which move in response to electrical signals. No electricity is needed to maintain an image on screen because illumination comes from purely reflected light.

F

• Fab – Fabricator. Refers to a fabrication facility where display panels are made. See Gen.

• FED – Field Emission Display. A combination of LCD and CRT technology, with electrons fired at a phosphor panel. Because it uses an LCD, an FED can be much thinner than traditional CRT displays.

• FOV – Field of View. FOV refers to (1) a human’s range of vision (measured in degrees), (2) the visual range of images presented by an XR device, and (3) the solid angle that can be measured by an optical device. For example, an average non-binocular human FOV is roughly 200-220 degrees (±100-110°) horizontal while binocular FOV covers an average of around 130° (±60-65°) horizontal. Radiant’s new XRE Lens can measure the FOV within an AR/VR/MR headset to 70° (± 35°) horizontal.

• FPD – Flat panel display. Display devices with images shown on a flat viewing surface, first introduced in the 1950s. Until 2013, all displays were flat panels due to the rigidity of CRT, LCD, and other screen technologies.

• FPS – Frames per second. A measure of how many image frames can be captured by a camera or shown on a display within one second. A higher frame rate generally yields a more dynamic image, but this also depends on the related metric of refresh rate (measured in frequency, Hz). 

G

• Gen – Generation. Display fabrication facilities (Fabs) are identified by their “generation” such as Gen 8, Gen 8.5, Gen 9, etc. Each generation is defined by the size and resolution of display panels it can build. For example, the newest Gen 10+ fabs can produce 65” screens with 8K resolution.

H

• HDR – High Dynamic Range. Dynamic range refers the ratio between maximum and minimum light intensities—describing the number of measurable values of lightness and darkness—shown by a display. High dynamic range means there is a large difference between the luminance values of the lightest and darkest parts of an image.  

• HDTV – High-Definition Television. A typical HDTV has 720 or 1080 rows of pixels. A “Full HDTV” indicates 1080 rows x 1920 columns of pixels, also called 1080P displays. Learn more…

• HMD – Head-Mounted Device. Any display device that is worn on the user’s head, such as a helmet, VR goggles, or AR smartglasses.

• HUD – Head-Up Display. A display where images (such as text or symbols) are shown on a transparent screen directly in front of the user (for example, on the interior surface of a car windshield, or on the display screen of an AR/MR headset). The display enables the user to receive information without having to turn their head or remove their visual attention from the real-world environment visible through the screen. Learn more…

I

• ICDM – International Committee for Display Metrology. A committee within SID (the Society for Information Display) that provides guidance on the test and measurement of displays.www.sid.org/Standards/ICDM

• IEEE – Institute of Electrical and Electronics Engineers. A large global organization that issues standards, publications, and holds conferences on a wide range of technology topics including displays. www.ieee.org

• InGaN – Indium gallium nitride. A semiconducting chemical alloy that is used to make many microLEDs, typically pronounced “in-gan”. See also AlInGaP.

• IoT – Internet of Things. The vast ecosystem of devices and systems that are connected to the internet such as smart home devices, factory robotic systems, and industrial sensors. 

J

• JOLED – JOLED, Inc. Not a type of OLED technology, but a Japan-based company that fabricates OLED displays using inkjet printing methods.

L

• LCD – Liquid Crystal Display. The workhorse display panel for the last 30 years, LCDs still make up more than half of all displays produced today across all industries including consumer electronics, automotive, medical, and industrial. LCDs have two layers of polarized glass that encase a layer of liquid crystals, often nematic crystals, which are in a twisted shape (called twisted nematic, or TN). Each crystal is one pixel. When electricity is applied, the crystals un-twist themselves to varying degrees, allowing light to pass through (from a backlight layer; See BLU). The alignment and degree of twist of the crystals determines the color seen by a viewer. Most LCD displays are active matrix using a TFT layer. 

• LCoS –Liquid Crystal on Silicon. A microdisplay technology using a liquid crystal layer on top of a silicon backplane. Learn more…

• LED – Light emitting diode. Technically, a semiconductor that emits light when electricity passes through it. Different chemical compounds create diodes in different colors. Broadly speaking, LEDs are one of the most revolutionary inventions of modern time, with a wealth of applications in multiple industries due to their brightness, small size, and power efficiency.

• LMD – Light Measurement Device. For example, a spectrometer or imaging photometer used for display metrology, capable of measuring relative or absolute values of light such as luminance and chromaticity. For example, Radiant’s line of ProMetric® Imaging Photometers and Colorimeters.

• LPD – Laser Phosphor Display. A display that uses mirrors to direct UV light beams from multiple lasers to a screen surface that is coated with phosphor. The light excites the phosphor, which emits light.

M

• MEMS – Microelectromechanical Systems. MEMS-based displays use projectors and mirrors to generate an image. Originally tried for FPDs but abandoned, MEMS offer brightness in sunlight and low energy consumption, so are now being considered for NED and HUD displays. Learn more…

• MicroLED – Microscopic LEDs. Nanoscale LEDs that are generally defined as being <100 μm in size. Some are as small as 5-10μ. Learn more…

• MiniLED – Miniature LEDs. Generally considered to be LED diodes sized between roughly 100μm to 1mm. Learn more…

• MLED – Miniature LED display. A display that uses miniLEDs as the backlight (See BLU) for an LCD screen.

• MR – Mixed Reality or Merged Reality, because it merges virtual and real-world elements together. While AR devices simply display images on a transparent screen, MR takes this a step further enabling user interaction with both virtual and physical elements.

• MTF – Modulation Transfer Function. A measure used to characterize “the ability of an optical system to transfer various levels of detail from object to image. Performance is measured in terms of contrast (degrees of gray), or of modulation, produced for a perfect source of that detail level.”1Learn more…

• μLED – MicroLED. Using the Greek letter (mu), which is the symbol for “micro”.

• μm – Micrometer. Often called a micron, one μm is equal to one-millionth of a meter, or 1 x 106. For reference, a human hair is roughly 50-90 microns in diameter.

N

• NED – Near-Eye-Display or near-to-eye display. Any display that is located directly in front of the user’s eye(s), for example mounted into a helmet, within VR goggles, or in a pair of AR smartglasses.

• NIST – National Institute of Standards and Technology. www.nist.gov. 

• Nits – Units of brightness. Nits is shorthand for candelas per meter squared (cd/m2), the scientific unit for measuring  the brightness (luminance) of a light source or display. One nit is roughly 3.246 lumens. Fun fact: the word nit is derived from the Latin nitere which means “to shine.”

O

• OLED – Organic Light Emitting Diode. OLEDs are LEDs that are made using organic (carbon-based) materials. When excited electrically, OLEDs emit light, thus OLED displays do not require a backlight.

P

• PDP – Plasma Display Panel. A plasma display consists of tiny cells of inert gas sandwiched between two layers of gas. When electricity is applied, the gas turns to plasma that excites phosphors to emit light. Monochrome PDPs first came into use in the 1970s. In the 1990s, full-color PDP televisions were sold to consumers, and they remained popular until the advent of LCD displays. Learn more…

• PHOLED – Phosphorescent OLED. An emerging display technology that relies on phosphorescent particles (in place of the fluorescent particles used in standard OLEDs). PHOLED displays also have better quantum efficiency (see EQE), thus use relatively little power.

• PMOLED – Passive-Matrix OLED. An early type of OLED display where each line of pixels is controlled as one, with no storage capacitor needed. While simpler to fabricate and less costly than AMOLED displays, PMOLEDs require more voltage and have a shorter lifespan. See also AMOLED.

• PPI – Pixels per inch. A metric indicating the resolution—or pixel density—of a display. Refers to the number of individual pixels that fit in a one-inch section of a display panel. Expressed as both horizontal and vertical metrics, for example 200 x 200 PPI. More PPI = a higher-resolution image.

Q

• QD – Quantum Dot. QDs are semiconductor particles that measure only a few nanometers (nm) in diameter. They have unique optoelectronic properties—for example, when excited with electrical current they emit very bright light in a wide range of colors. The color emitted by each QD is determined by the size of the particle.

• QE – Quantum Efficiency. A ratio of the number of electrons supplied to an external circuit compared to the number incident photons collected on a sensor. For example, in a camera, photons (light particles) of an image land on a sensor within the camera when the aperture is open. Those photons are then converted to electrons, which can be read as a digital signal by the camera system recreating the image as a photograph. Ideal QE would be 1 (100% conversion of photons to electrons). 

• QD-LED – Quantum Dot LED (but not the same thing as QLED). Samsung Display's terminology for its televisions with 100% blue emissive pixels that use QD phosphors to convert some of the blue pixels to red and green. 

• QD-OLED – Quantum Dot OLED. An OLED television that uses quantum dots as a top layer to either filter or convert light that shines through from a backplane array (See BLU) of OLEDs. Using QDs produces a more vivid array of colors and can increase efficiency. This is especially true when the OLED backplane consists of all blue diodes (that require less power) to excite the QDs, rather than using a typical RGB backlight array.

• QLED – Quantum Dot LED (but not the same thing as QD-LED). Samsung Display’s terminology for its televisions that use an LED backlight with a QD layer:. “quantum-dot phosphors convert blue light to a combined white in a backlight for an otherwise conventional TFT-LCD display.”2  

R

• Rec. 2020 – ITU-R Recommendation BT.2020. Also called BT.2020, Rec. 2020 is a set of display parameters defined by the International Telecommunication Union (ITU) in 2012 and subsequently updated. It includes specifications for high-definition displays, color gamut, resolution, frame rate, etc. Learn more…

• RGB – Red, Green, Blue. RGB can refer to the colors of display elements (pixels or subpixels) such as individual LED diodes. Displays made up of individual red, green, and blue pixels or pixel elements may be called RGB displays.CIE RGB refers to a color space (mathematical model) used to describe the relative color performance characteristics of a display device. 

• RGBW – Red, Green, Blue, White. Refers specifically to LED/OLED displays that use diodes of red, green, blue, and white.

• RLCD – Reflective Liquid Crystal Displays. LCDs where the illumination source is reflected ambient light, often using mirrors to amplify the light. RLCD technology is used for many ePaper displays.

• RoHS – Reduction of Hazardous Substances Directive. A set of rules in the European Union related to the use of hazardous substances within electronic devices. Learn more…

S

• SID – Society for Information Display. An industry organization for displays, generally electronic displays including televisions, smartphones, XR devices, digital signage, automotive displays, and computer monitors. www.sid.org

• SiOLED – Silicon OLED. An emerging type of microdisplay made of OLEDs fabricated on a silicon wafer.

T

• TFT – Thin film transistor. A transistor layer often used in displays such as LCDs. TFT displays have one transistor for each pixel that actively turns it on and off, enabling a very fast image response time. The transistors are typically arranged in a matrix, thus displays with this technology are called “active matrix” (AM) displays. TFTs are typically made “of metal-oxide-semiconductor field-effect transistor (MOSFETs) fabricated by coating a layer of an active semiconductor layer, metallic contacts, and the dielectric layer over an insulating substrate.”23

• TOLED – Transparent OLED. OLED displays that use transparent display materials (anode and cathode) deposited on a transparent substrate surface such as glass. Because OLED pixels are semi-transparent (up to 85%) and self-emitting (emit their own light thus do not require a backlight layer), they can display images that are viewable from either side, while still enabling viewers to see through the glass.

U

• UHD – Ultra-High Definition. Originally referred to televisions with 3849x2160 pixels, but now generally used for any television with resolution at or above that level, such as 4K and 8K displays. Learn more…

V

• VESA – Video Electronics Standards Association. A standards and certification body for computer displays. www.vesa.org

• VFD – Vacuum Fluorescent Display. A type of display technology with high brightness and contrast, but with limited ability to show anything other than pre-set shapes or patterns (such as letters and numerals). Commonly used for simple display panels such as digital clocks and electrical appliances.

• VR – Virtual Reality. Devices and applications that provide an immersive visual experience (encompassing a user’s full visual FOV), for example for gameplay or training simulations. A VR headset displays images to the wearer on an opaque surface and blocks out the surrounding environment and ambient light. See also AR, MR, XR.

W

• WOLED – White OLED. Different colors of OLEDs can be created by varying the material mixture used to form the diode crystals. White OLEDs are typically brighter and emit a more uniform light than RGB OLED arrays. They can be used with color filters to produce display images. They also have applications in the lighting industry, such as in color-tunable light fixtures.

X

• XR – Extended Reality. The all-encompassing term for virtual, augmented, and merged/mixed-reality displays and applications. See also AR, MR, and VR.

• XYZ – CIE XYZ is one of two types of mathematical models and color spaces defined by the CIE for calculating values of color (chromaticity). X, Y, and Z are coordinates in the 3D CIE color space, a measurement of the absolute, device-independent chromaticity of a light source or display pixel. See also RGB.

Numeric Acronyms

• 4K and 8K – Types of ultra-high-resolution displays. 4K screens have 3,840 x 2,160 pixels and 8K screens boast 7,680 x 4,320 pixels. Learn more…

This list is just the tip of the iceberg. If I’ve left out some of your favorite, least favorite, or unidentified mystery acronyms, never fear: PC Magazine has compiled an entire encyclopedia of technology terms!

Who else thinks the “Twisted Crystals” is a great name for a band (see LCD)? 

This article was originally published on the website of Radiant Vision Systems and is only reproduced here with their kind permission.