Circuit Negma

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NOTES ::Terms

Posted by Circuit Negma on September 11, 2008

Create By: Hussein Nosair



Term (Acronym) [units]: Definition

Acoustic Pulse Recognition (APR): A new touch screen technology that works by sensing the sound made when a touch screen is touched and comparing it with a stored table of sounds in order to locate the user’s contact point within the active area.

Active Area: The dimensions of the area in a display that contains pixels.

Active Matrix (AM): A display backplane structure in which switching transistors control the voltage or current for each pixel. It produces a brighter, sharper and faster display with a broader viewing angle than a passive matrix display. Used in reference to both LCDs and OLEDs; used synonymously with TFT (thin-film transistor).

Active Matrix Liquid Crystal Display (AMLCD): An LCD display in which each pixel has its own transistor on/off switch rather than being activated by its address within a passive matrix of rows and columns. This is the most common type of LCD; it’s also called “TFT-LCD”.

Active Matrix Organic Light-Emitting Display (AMOLED): An OLED display in which each pixel has its own transistor on/off switch (see TFT and Active Matrix) rather than being activated by its address within a passive matrix of rows and columns. This type of OLED is just entering initial production in mid-2006; most current OLED displays are passive matrix.

Additive Primaries: In color reproduction, the colors of red, green and blue. When lights in these colors are combined (e.g., from an LCD backlight and color filter combination), they produce the visual sensation of white light. When these three colors are combined at varying intensities, a range of different colors is produced. Combining two primaries at 100% produces a subtractive primary, called cyan, magenta or yellow.

Alignment Layer: A thin-film layer in an LCD display that’s used to line up liquid crystal molecules in a uniform direction. The thin film is typically applied by spin coating, and then treated to impart a desired direction in which the liquid crystal molecules will attach and align. (See Rubbing.)

Ambient Light: Whatever lighting exists in any situation. In a living room at home, ambient lighting could be the light from two incandescent lights; on the beach it could be direct sun plus all the light reflected from the sand and water.

Ambient Light Sensor: A light-sensitive electronic component used to adjust the brightness of an LCD display’s backlight so that the display remains comfortably readable over a range of ambient light conditions.

Amorphous Silicon (a-Si): A semiconductor material that has no definite or regular crystal structure and is used to make the thin-film transistors (TFTs) in an active-matrix LCD or OLED.

Amorphous Silicon Thin-Film Transistor (a-Si TFT): Thin-film transistors made with amorphous silicon, typically used in the active matrix backplane of an LCD or OLED display. However, since AMOLEDs haven’t reached the mainstream yet, the term “a-Si TFT” is often used as a shorthand way of referring just to AMLCDs.

Analog: In analog technology, a wave is recorded or used in its original form, as opposed to being digitized and reduced to a stream of ones and zeros (digital data).

Analog Resistive Touch Screen: See Resistive Touch.

Analog-to-Digital Converter (ADC): A device that converts analog (continuously varying) input signals into digital output signals. An LCD monitor with an analog interface (e.g., a VGA connector) uses an analog-to-digital converter to convert the analog signal into a digital signal that the LCD panel can display. LCD monitors with only a digital interface (e.g., a DVI connector) require that the analog-to-digital conversion take place before the signal arrives at the monitor.

Anti-Aliasing: The technique of minimizing aliasing (jagged or blocky appearance) when representing a high-resolution signal at a lower resolution. Used in sub-pixel rendering.

Anti-Glare (AG): A physical treatment on the top surface of a display that changes light reflected from the display into a diffuse reflection rather than a specular reflection. The treatment can be produced by mechanical or chemical etching. Anti-glare doesn’t reduce the amount of light reflected from the surface; it only changes its characteristics. You can tell if a display has anti-glare treatment by looking at the reflected image of a bright light such as a light bulb or the sun. If the reflected image is clear and sharp like a mirror, there’s no AG. If the reflected image is a generalized area of light with no sharp boundaries, AG is present.

Anti-Reflection (AR): A thin-film coating that reduces the reflection of light from a surface via the use of refractive-index matching and destructive interference techniques.

Aperture Ratio: The ratio between the transmissive portion of a pixel and its surrounding opaque electronics (e.g., the thin-film transistors), expressed as a percentage. Aperture ratio, also known as “fill factor”, is the limiting factor for luminance. Higher aperture-ratio designs enable brighter displays (more light for the same amount of power) or lower-power displays (less power to produce the same amount of light).

Array: The term used to describe either the back substrate (TFT array) or front substrate (color filter array) of an LCD display during manufacture.

Array Process: The process of fabricating thin-film transistors on a glass substrate. This is the first major process group in manufacturing an LCD.

Aspect Ratio: The width-to-height ratio of the active area of a display. The standard PC display aspect ratio has been 4:3 since 1981; the standard is now migrating to 16:10 (“widescreen” displays). Similarly, the standard TV aspect ratio has been 4:3 for 50+ years; now it’s migrating to the HDTV standard of 16:9.

Average Selling Price (ASP): The average price at which a product (e.g., 15″ LCDs) sells across multiple distribution channels.


Term (Acronym) [units]: Definition

Backlight: The light source for a transmissive LCD, located directly behind the LCD (for small or very large LCDs), or at the side of the LCD (for small or medium LCDs). The light from the backlight is either blocked (black) or passed (white) by the LCD cell. LEDs or EL panels are used for most backlights smaller than five inches in diagonal size; fluorescent lamps are used for most backlights larger than five inches.

Backlight Unit (BLU): The complete backlight assembly for an LCD display, typically consisting of the light source, a light guide, reflectors, brightness enhancement films or prism sheets (if used), a diffuser and a housing.

Backplane: The portion of a display that controls the pixels located in the frontplane. In an AMLCD or AMOLED display, the backplane contains the thin-film transistors (TFTs).

Bezel: A metal or plastic frame that surrounds the active area of a display. The bezel protects the edges of the display and any circuitry that may be located there.

Bill Of Materials (BOM): A detailed list of materials and components that make up an assembly. The BOM is a building block of the manufacturing information system and is often used in cost accounting.

Birefringence: Birefringence, also called double-refraction, is the decomposition of a single light ray into two light rays when it passes through certain types of material, depending on the polarization of the light. Birefringent materials are used in many devices that manipulate the polarization of light, such as retardation films and polarizing prisms.

Bit Depth: See Color Depth .

Black Luminance: The amount of light that a display emits when every pixel is set to black. Ideally this is zero, but LCDs (in particular) have problems with leakage of light from the backlight. Emissive displays such as PDPs and OLEDs typically have much lower black luminance levels.

Black Matrix (BM): A patterned layer in an LCD’s color filter assembly whose purpose is to prevent light leakage and improve contrast.

Blu-ray: One of two next-generation (post-DVD) optical disc formats designed for storage of high-definition video and data. Developed by Sony. The name is derived from the blue-violet laser used to read and write the disc.

Brightness: The dimension of color that is referred to on an achromatic scale ranging from black to white; also called luminous intensity or lightness.

Brightness Enhancement Film (BEF): A prism film that increases a display’s brightness. 3M is the dominant supplier of BEF, although because of recent patent expirations, many new suppliers are entering the market.


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