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Burst Dimming
Burst dimming is a method to control dimming of cold cathode fluorescent lamps (CCFLs) and LEDs by using pulse width modulation (PWM) at approximately 100-300 Hz which is supposed to be above the noticeable flicker limit for the human eye. {{cite web, title=Electrical Engineering Glossary Definition for Burst Dimming - Maxim/Dallas, url=http://www.maxim-ic.com/glossary/index.cfm/Ac/V/ID/998/Tm/Burst-Dimming 070925 maxim-ic.com This technique is sometimes used with TFT displays to control backlighting A backlight is a form of illumination used in liquid-crystal displays (LCDs) that provides light from the back or side of a display panel. LCDs do not produce light on their own, so they require illumination—either from ambient light or a de .... An alternative dimming method is to control lamp current. References Display technology Lighting Liquid crystal displays ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cold Cathode
A cold cathode is a cathode that is not electrically heated by a Electrical filament, filament.A negatively charged electrode emits electrons or is the positively charged terminal. For more, see field emission. A cathode may be considered "cold" if it emits more electrons than can be supplied by thermionic emission alone. It is used in Gas discharge lamp, gas-discharge lamps, such as neon lamps, discharge tubes, and some types of vacuum tube. The other type of cathode is a hot cathode, which is heated by electric current passing through a Electrical filament, filament. A cold cathode does not necessarily operate at a low temperature: it is often heated to its operating temperature by other methods, such as the current passing from the cathode into the gas. Cold-cathode devices A cold-cathode vacuum tube does not rely on external heating of an electrode to provide thermionic emission of electrons. Early cold-cathode devices included the Geissler tube and Julius Plücker, Plucker ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pulse-width Modulation
Pulse-width modulation (PWM), also known as pulse-duration modulation (PDM) or pulse-length modulation (PLM), is any method of representing a signal as a rectangular wave with a varying duty cycle (and for some methods also a varying period). PWM is useful for controlling the average power or amplitude delivered by an electrical signal. The average value of voltage (and current) fed to the load is controlled by switching the supply between 0 and 100% at a rate faster than it takes the load to change significantly. The longer the switch is on, the higher the total power supplied to the load. Along with maximum power point tracking (MPPT), it is one of the primary methods of controlling the output of solar panels to that which can be utilized by a battery. PWM is particularly suited for running inertial loads such as motors, which are not as easily affected by this discrete switching. The goal of PWM is to control a load; however, the PWM switching frequency must be sele ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hertz
The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or Cycle per second, cycle) per second. The hertz is an SI derived unit whose formal expression in terms of SI base units is 1/s or s−1, meaning that one hertz is one per second or the Inverse second, reciprocal of one second. It is used only in the case of periodic events. It is named after Heinrich Hertz, Heinrich Rudolf Hertz (1857–1894), the first person to provide conclusive proof of the existence of electromagnetic waves. For high frequencies, the unit is commonly expressed in metric prefix, multiples: kilohertz (kHz), megahertz (MHz), gigahertz (GHz), terahertz (THz). Some of the unit's most common uses are in the description of periodic waveforms and musical tones, particularly those used in radio- and audio-related applications. It is also used to describe the clock speeds at which computers and other electronics are driven. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flicker (screen)
Flicker is a visible change in brightness between cycles displayed on video displays. It applies to the refresh interval on cathode-ray tube (CRT) televisions and computer monitors, as well as plasma computer displays and televisions. Occurrence Flicker occurs on CRTs when they are driven at a low refresh rate, allowing the brightness to drop for time intervals sufficiently long to be noticed by a human eye – see persistence of vision and flicker fusion threshold. For most devices, the screen's phosphors quickly lose their excitation between sweeps of the electron gun, and the afterglow is unable to fill such gaps – see phosphor persistence. A refresh rate of 60 Hz on most screens will produce a visible "flickering" effect. Most people find that refresh rates of 70–90 Hz and above enable flicker-free viewing on CRTs. Use of refresh rates above 120 Hz is uncommon, as they provide little noticeable flicker reduction and limit available resolution. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Human Eye
The human eye is a sensory organ in the visual system that reacts to light, visible light allowing eyesight. Other functions include maintaining the circadian rhythm, and Balance (ability), keeping balance. The eye can be considered as a living optics, optical device. It is approximately spherical in shape, with its outer layers, such as the outermost, white part of the eye (the sclera) and one of its inner layers (the pigmented choroid) keeping the eye essentially stray light, light tight except on the eye's optic axis. In order, along the optic axis, the optical components consist of a first lens (the cornea, cornea—the clear part of the eye) that accounts for most of the optical power of the eye and accomplishes most of the Focus (optics), focusing of light from the outside world; then an aperture (the pupil) in a Diaphragm (optics), diaphragm (the Iris (anatomy), iris—the coloured part of the eye) that controls the amount of light entering the interior of the eye; then an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
TFT LCD
A thin-film-transistor liquid-crystal display (TFT LCD) is a type of liquid-crystal display that uses thin-film transistor, thin-film-transistor technology to improve image qualities such as addressability and contrast. A TFT LCD is an active matrix LCD, in contrast to passive matrix LCDs or simple, direct-driven (i.e. with segments directly connected to electronics outside the LCD) LCDs with a few segments. TFT LCDs are used in television sets, computer monitors, mobile phones, video game systems, personal digital assistants, navigation systems, video projector, projectors, and dashboards in some automobiles and in medium to high end motorcycles. History In February 1957, J. Torkel Wallmark, John Wallmark of RCA filed a patent for a thin film MOSFET. Paul K. Weimer, also of RCA, implemented Wallmark's ideas and developed the thin-film transistor (TFT) in 1962, a type of MOSFET distinct from the standard bulk MOSFET. It was made with thin films of cadmium selenide and cadmium s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Backlight
A backlight is a form of illumination used in liquid-crystal displays (LCDs) that provides light from the back or side of a display panel. LCDs do not produce light on their own, so they require illumination—either from available light, ambient light or a dedicated light source—to create a visible image. Backlights are commonly used in smartphones, computer monitors, and LCD televisions. They are also used in small displays, such as Watch, wristwatches, to enhance readability in low-light conditions. Typical light sources for backlights include light-emitting diodes (LEDs) and cold cathode fluorescent lamps (CCFLs). Simple types of LCDs, such as those used in pocket calculators, are built without an internal light source and rely on external light sources to make the display image visible to the user. However, most LCD screens are designed with an internal light source. These screens consist of multiple layers, with the backlight typically being the first layer from the bac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Display Technology
A display device is an output device for presentation of information in visual or tactile form (the latter used for example in tactile electronic displays for blind people). When the input information that is supplied has an electrical signal the display is called an '' electronic display''. Common applications for ''electronic visual displays'' are television sets or computer monitors. Types of electronic displays In use These are the technologies used to create the various displays in use today. * Liquid-crystal display (LCD) ** Light-emitting diode (LED) backlit LCD ** Thin-film transistor (TFT) LCD ** Quantum dot (QLED) display * Light-emitting diode (LED) display ** OLED display ** AMOLED display ** Super AMOLED display Segment displays Some displays can show only digits or alphanumeric characters. They are called segment displays, because they are composed of several segments that switch on and off to give appearance of desired glyph. The segments are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lighting
Lighting or illumination is the deliberate use of light to achieve practical or aesthetic effects. Lighting includes the use of both artificial light sources like lamps and light fixtures, as well as natural illumination by capturing daylight. Daylighting (architecture), Daylighting (using windows, skylights, or Architectural light shelf, light shelves) is sometimes used as the main source of light during daytime in buildings. This can save energy in place of using artificial lighting, which represents a major component of energy consumption in buildings. Proper lighting can enhance task performance, improve the appearance of an area, or have positive psychological effects on occupants. Indoor lighting is usually accomplished using light fixtures, and is a key part of interior design. Lighting can also be an intrinsic component of landscaping, landscape projects. History With the Control of fire by early humans, discovery of fire, the earliest form of artificial lighting used ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
