In the context of displays, OLEDs have certain advantages over traditional liquid crystal displays (LCDs)

An organic light emitting diode (OLED), also organic electro luminescent device (OELD), is a light-emitting diode (LED) whose emissive electroluminescent layer is composed of a film of organic compounds. This layer of organic semiconductor material is formed between two electrodes, where at least one of the electrodes is transparent.

Such devices can be used in television screens, computer monitors, small, portable system screens such as cell phones and PDAs, watches, advertising, information and indication. OLEDs can also be used in light sources for general space illumination, and large-area light-emitting elements. Due to the younger stage of development, OLEDs typically emit less light per area than inorganic solid-state based LEDs which are usually designed for use as point-light sources.

In the context of displays, OLEDs have certain advantages over traditional liquid crystal displays (LCDs). OLED displays do not require a backlight to function. Thus, they can display deep black levels and can be thinner and lighter than LCD panels. OLED displays also naturally achieve higher contrast ratios than either LCD screens using cold cathode fluorescent lamps (CCFLs) or the more recently developed LED backlights in conditions of low ambient light such as dark rooms.

light-emitting diode (LED) is a semiconductor light source. LEDs are used as indicator lamps in many devices, and are increasingly used for lighting. Introduced as a practical electronic component in 1962, early LEDs emitted low-intensity red light, but modern versions are available across the visible, ultraviolet and infrared wavelengths, with very high brightness.

The LED is based on the semiconductor diode. When a diode is forward biased (switched on), electrons are able to recombine with holes within the device, releasing energy in the form of photons. This effect is called electroluminescence and the color of the light (corresponding to the energy of the photon) is determined by the energy gap of the semiconductor. An LED is usually small in area (less than 1 mm2), and integrated optical components are used to shape its radiation pattern and assist in reflection. LEDs present many advantages over incandescent light sources including lower energy consumption, longer lifetime, improved robustness, smaller size, faster switching, and greater durability and reliability. However, they are relatively expensive and require more precise current and heat management than traditional light sources. Current LED products for general lighting are more expensive to buy than fluorescent lamp sources of comparable output.

They also enjoy use in applications as diverse as replacements for traditional light sources in automotive lighting (particularly indicators) and in traffic signals. The compact size of LEDs has allowed new text and video displays and sensors to be developed, while their high switching rates are useful in advanced communications technology.

A semiconductor is a material that has an electrical conductivity between that of a conductor and an insulator, that is, generally in the range 10³ Siemens/cm to 10⁻⁸ S/cm. Devices made from semiconductor materials are the foundation of modern electronics, including radio, computers, telephones, and many other devices. Semiconductor devices include the various types of transistor, solar cells, many kinds of diodes including the light-emitting diode, the silicon controlled rectifier, and digital and analog integrated circuits. Solar photovoltaic panels are large semiconductor devices that directly convert light energy into electrical energy. An external electrical field may change a semiconductor's resistivity. In a metallic conductor, current is carried by the flow of electrons. In semiconductors, current can be carried either by the flow of electrons or by the flow of positively-charged "holes" in the electron structure of the material.

Common semiconducting materials are crystalline solids but amorphous and liquid semiconductors are known, such as mixtures of arsenic, selenium and tellurium in a variety of proportions. They share with better known semiconductors intermediate conductivity and a rapid variation of conductivity with temperature but lack the rigid crystalline structure of conventional semiconductors such as silicon and so are relatively insensitive to impurities and radiation damage.

Silicon is used to create most semiconductors commercially. Dozens of other materials are used, including germanium, gallium arsenide, and silicon carbide. A pure semiconductor is often called an “intrinsic” semiconductor. The conductivity, or ability to conduct, of common semiconductor materials can be drastically changed by adding other elements, called “impurities” to the melted intrinsic material and then allowing the melt to solidify into a new and different crystal. This process is called "doping"

The visible spectrum is the portion of the electromagnetic spectrum that is visible to (can be detected by) the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light. A typical human eye will respond to wavelengths from about 380 to 750 nm.[1] In terms of frequency, this corresponds to a band in the vicinity of 790–400 terahertz. A light-adapted eye generally has its maximum sensitivity at around 555 nm (540 THz), in the green region of the optical spectrum (see: luminosity function). The spectrum does not, however, contain all the colors that the human eyes and brain can distinguish. Unsaturated colors such as pink, or purple variations such as magenta, are absent, for example, because they can only be made by a mix of multiple wavelengths.

Visible wavelengths also pass through the "optical window", the region of the electromagnetic spectrum that passes largely unattenuated through the Earth's atmosphere. Clean air scatters blue light more than wavelengths toward the red, which is why the mid-day sky appears blue. The human eye's response is defined by subjective testing (see CIE), but atmospheric windows are defined by physical measurement.

The "visible window" is so called because it overlaps the human visible response spectrum. The near infrared (NIR) windows lie just out of human response window, and the Medium Wavelength IR (MWIR) and Long Wavelength or Far Infrared (LWIR or FIR) are far beyond the human response region.

Many species can see wavelengths that fall outside the "visible spectrum". Bees and many other insects can see light in the ultraviolet, which helps them find nectar in flowers. Plant species that depend on insect pollination may owe reproductive success to their appearance in ultraviolet light, rather than how colorful they appear to us. Birds too can see into the ultraviolet (300–400 nm), and some have sex-dependent markings on their plumage, which are only visible in the ultraviolet range.

Ultraviolet (UV) light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than x-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV. It is so named because the spectrum consists of electromagnetic waves with frequencies higher than those that humans identify as the color violet.

UV light is found in sunlight and is emitted by electric arcs and specialized lights such as black lights. As an ionizing radiation it can cause chemical reactions, and causes many substances to glow or fluoresce. Most people are aware of the effects of UV through the painful condition of sunburn, but the UV spectrum has many other effects, both beneficial and damaging, on human health.

The emission spectrum of a chemical element or chemical compound is the relative intensity of each frequency of electromagnetic radiation emitted by the element's atoms or the compound's molecules when they are returned to a ground state.

Each element's emission spectrum is unique. Therefore, spectroscopy can be used to the identify the elements in matter of unknown composition. Similarly, the emission spectra of molecules can be used in chemical analysis of substances.

In physics, emission is the process by which the energy of a photon is released by another entity, for example, by an atom whose electrons make a transition between two electronic energy levels. The emitted energy is in the form of a photon. The emittance of an object quantifies how much light is emitted by it. This may be related to other properties of the object through the Stefan–Boltzmann law. For most substances, the amount of emission varies with the temperature and the spectroscopic composition of the object, leading to the appearance of color temperature and emission lines. Precise measurements at many wavelengths allow the identification of a substance via emission spectroscopy.

Important factors to consider when evaluating an LCD monitor:
Resolution: The horizontal and vertical screen size expressed in pixels (e.g., 1,024×768). Unlike CRT monitors, LCD monitors have a native-supported resolution for best display effect.
Dot pitch: The distance between the centers of two adjacent pixels. The smaller the dot pitch size, the less granularity is present, resulting in a sharper image. Dot pitch may be the same both vertically and horizontally, or different (less common).
Viewable size: The size of an LCD panel measured on the diagonal (more specifically known as active display area).
Response time: The minimum time necessary to change a pixel's color or brightness. Response time is also divided into rise and fall time. For LCD monitors, this is measured in btb (black to black) or gtg (gray to gray). These different types of measurements make comparison difficult. LCD Monitor Parameters: Objective and Subjective Analysis
Input lag - a delay between the moment monitor receives the image over display link and the moment the image is displayed. Input lag is caused by internal digital processing such as image scaling, noise reduction and details enhancement, as well as advanced techniques like frame interpolation. Input lag can measure as high as 3-4 frames (in excess of 67 ms for a 60p/60i signal). Some monitors and TV sets feature a special "gaming mode" which disables most internal processing and sets the display to its native resolution.
Refresh rate: The number of times per second in which the monitor draws the data it is being given. Since activated LCD pixels do not flash on/off between frames, LCD monitors exhibit no refresh-induced flicker, no matter how low the refresh rate.[3] High-end LCD televisions now feature up to 240 Hz refresh rate, which allows advanced digital processing to insert additional interpolated frames to smooth up motion, especially with lower-framerate 24p material like the Blu-ray disc. However, such high refresh rates may not be supported by pixel response times, and additional processing can introduce considerable input lag.
Matrix type: Active TFT or Passive.
Color support: How many types of colors are supported (coll., more specifically known as color gamut).
Viewing angle: (coll., more specifically known as viewing direction).
Brightness: The amount of light emitted from the display (coll., more specifically known as luminance).
Contrast ratio: The ratio of the intensity of the brightest bright to the darkest dark.
Aspect ratio: The ratio of the width to the height (for example, 4:3, 5:4, 16:9 or 16:10).
Input ports (e.g., DVI, VGA, LVDS, DisplayPort, or even S-Video and HDMI).
Gamma correction

Gamma compression, also known as gamma encoding, is used to encode linear luminance or RGB values into video signals or digital video file values; gamma expansion is the inverse, or decoding, process, and occurs largely in the nonlinearity of the electron-gun current–voltage curve in cathode ray tube (CRT) monitor systems, which acts as a kind of spontaneous decoder. Gamma encoding helps to map data (both analog and digital) into a more perceptually uniform domain.

The following figure shows the behavior of a typical display when image signals are sent linearly (γ = 1.0) and gamma-encoded (gamma compressed with γ = 1 / 2.2 for a γ = 2.2 standard display). In the first case, the resulting image over the CRT is notably darker and contrastier than the original, whereas it is shown with high fidelity in the second case. Digital cameras produce, and TV stations broadcast, signals in gamma-encoded form, anticipating the standardized gamma of the reproducing device, so that the overall system will be linear, as shown on the bottom; if cameras were linear, as on the top, the overall system would be nonlinear. Similarly, image files are almost always stored on computers and communicated across the Internet with gamma encoding.

The cathode ray tube (CRT) is a vacuum tube containing an electron gun (a source of electrons) and a fluorescent screen, with internal or external means to accelerate and deflect the electron beam, used to create images in the form of light emitted from the fluorescent screen. The image may represent electrical waveforms (oscilloscope), pictures (television, computer monitor), radar targets and others.

The CRT uses an evacuated glass envelope which is large, deep, heavy, and relatively fragile. Display technologies without these disadvantages, such as flat plasma displays, liquid crystal displays, DLP, OLED displays have replaced CRTs in many applications and are becoming increasingly common as costs decline.

While the pixel response time of the display is usually listed in the monitor's specifications, no manufacturers advertise the input lag of their displays, likely because the trend has been to increase input lag as manufacturers find more ways to process input at the display level before it is shown. Possible culprits are the processing overhead of HDCP, DRM, and also DSP techniques employed to reduce the effects of ghosting - and the cause may vary depending on the model of display. Investigations have been performed by several technology related websites; some of which are listed at the bottom of this article.

LCD, plasma, and DLP displays, unlike CRTs, have a native resolution. That is, they have a fixed grid of pixels on the screen that show the image sharpest when running at the native resolution (so nothing has to be scaled full-size which blurs the image). In order to display non-native resolutions, such displays must use video scalers, which are built into most modern monitors. As an example, a display that has a native resolution of 1600x1200 being provided a signal of 640x480 must scale width and height by 2.5x in order to display the image provided by the computer on the native pixels. In order to do this while producing as few artifacts as possible, advanced signal processing is required, which can be a source of introduced latency. Anecdotally, input lag is significantly less when displays operate in native resolutions for a given LCD screen. External devices have also been shown to reduce overall latency by providing faster image-space resizing algorithms than those present in the LCD screen.

Many LCDs also use a technology called “overdrive” which “reads” what is being sent to the display several frames ahead and processes the image to reduce blurring and streaks left by ghosting. The effect is that anything displayed on the screen is several frames behind which makes anything, even mouse movements, feel delayed as explained in the introduction of the article.