Technical Glossary
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Displaying 31 glossary terms found.


LED - Light Emitting Diode
A low-power, long life, light source, usually red, green or yellow in color. Some LEDs can produce two different colors. A network of LEDs can be arranged to form bar graphs or alphanumerics.

A unit of measure expressing the intensity of light reflected off an object. 1 Lambert = 0.318 Ft-c (foot-candles) per square centimeter. Expressed as foot-Lamberts or Ft-L.

Lambert's Law
That which governs the physical dynamics of light reflecting off a radiating surface, a screen. The radiant intensity emitted in any direction from a unit radiating surface falls off as the cosine of the angle between the normal to the surface and the direction of the radiation.

Light Amplification by Stimulated Emission of Radiation. A tightly focused beam of light used to play the signals stored on LaserDisc, CDs and DVDs.

System of audio/video recording on groveless discs. Laser light is reflected from the disc's microscopic pits and non-pitted areas, enabling the disc to be read by a laser-optical pickup.

LD. Optical laser-read home video format, in use since 1978. The LD is the video source of choice for many home theatre systems. The 425 horizontal line resolution (horizontal luminance or black and white detail) capability in NTSC is far superior to standard VHS at 260 lines, but not to DVD's 480 line potential. LaserDiscs feature two PCM digital audio channels, and stereo analog FM audio. Started as a brand-specific term but has now replaced earlier term, LaserVision, as generic format name.

LaserDisc Player
This key component in home theatre systems plays video and digital stereo audio from 12-, 8-, and 5-inch optical discs, plus DTS(r) Digital Surround LaserDiscs and CDs. Combi variations also plays 5-inch and 3-inch audio CDs.

Original name of LaserDisc format.

Late Reflection
Reflected energy that occurs a greater distance away from the source than an early reflection. Sometimes referred to as slap back or echo.

Law Of The First Wavefront
The first wavefront falling on the ear determines the perceived direction of the sound.

Liquid Crystal Diode Display. A panel that utilizes two transparent sheets of polarizing material with a liquid containing rod-shaped crystals between. When a current is applied to specific pixel-like areas, those crystals align to create dark images. The dark areas are combined with light areas to create text and images on the panel LCD panels do not emit light but are often back-lit or side-lit for better viewing.

LCD Panel
A device used to project video images through a Liquid Crystal Diode Display and an overhead projector onto a large screen. The panel is placed over the stage of an overhead projector, projecting the computer display onto a screen.

LCD Projector
Utilizing the LCD technique of putting together on a panel a number of elements which control the flow of light, these projectors separate the red, green and blue information to three different LCD panels. Since LCD panels do not produce color, the appropriate colored light is then passed through each panel and combined to exit through the projector lens and onto a viewing screen. If the individual LCD element size is large, there won't be much detail displayed on the screen. If the LCD element size is small, detail handling capability will be better, but reliability can become a problem. LCDs are not good about handling a lot of heat, something that comes along with a bright light bulb.

Learning Remote Control
A programmable remote control to operate other components by transferring infrared control codes from the original remotes to the learning remote.

Learning Remotes
Can be "taught" codes from other types of components, for example, A/V Receiver, Surround Processor, etc. When trying to tie all of your components together, a learning remote could be a better option. However, at best, they can only learn primary functions of each component. Normally, you cannot get into menus from other products to adjust say surround settings, for example. A learning remote from an A/V Receiver or an aftermarket Universal/Learning unit might be a better bet for trying to tie all of your components together. Mini remotes are found on some high-end sets. They are small and come in various shapes, for example, cigar-shaped, credit card-sized, shoe horn-like, etc. They provide basic functions, for example, Power On/Off, Channel Up/Down, and Volume Up/Down. A few Minis even provide access to on-screen menus.

Least Favored Viewer
The concept of the LFV really describes the proverbial "worst seat in the house."

Live end dead end. An optimal acoustical treatment plan for rooms in which one end is highly absorbent and the other end reflective and diffusive. In front of the listening position is the dead end, behind the listening position is the live end.

Lens Flare
Light reflections between adjacent lens surfaces in a compound lens, causing loss of contrast.

Lenticular Screen
A screen surface characterized by silvered or aluminized embossing, designed to reflect maximum light over wide horizontal and narrow vertical angles. Must be held very flat to avoid hot spots. A large series of parallel lenticulations cut vertically into the screen surface to improve horizontal dispersion.

A cylindrical lens which causes light passing through it to be dispersed perpendicular to its axis.

A term coined to describe the effect of watching films on video with an aspect ratio greater than 1.33.1 (1.37:1 video standard). The entire film frame is shown on screen, with black bars above and below to fill the video picture. The word "letterbox" was meant to assimilate the viewing of wide films on television to looking through a mailbox in a door.

The relative voltage intensity of an audio or video source.

Level Control
The level control on some interface products is similar to the contrast control on a data monitor. It can either increase or decrease the output voltage level of the interface to the connected data monitor or projector. This results in greater or less contrast in the picture.

Low frequency diffusion.

Low frequency effects or enhancement. Also known as the "boom" or "0.1" channel. A bandwidth limited channel for low frequency effects in film soundtracks played in 5.1-channel digital sound (Dolby® Digital, DTS® Digital Sound and DTS Digital Surround, and SDDS®). The frequency range is 5-120 Hz. The signal is reproduced with a subwoofer. The LFE channel has an additional 10dB of headroom in order to accommodate the required level of various types of special effects, such as explosions.

Light Emitting Diode
LED. A bright semi-conductor component often used in VCR and other equipment display panels.

Light Level
The intensity of a given lighting situation as measured in foot-candles (Ft-c).

Light Value Projection
The basic principle behind a Light Valve projection system is similar to a film projector. A light bulb is the source of light. A device that can control the color and intensity of the source light is placed between the bulb and the focusing lens. In the case of a film projector, the film is the light valve. In an electronic imaging system it can be any number of devices. There are several types of projectors that fit into this category. The LCD is one of the better known. The digital Micromirror, and Image Light Amplifier (ILA) are two other examples. Light Valve systems often have trouble with black level. It's hard to shut light completely off in an area adjacent to where it is on. Theoretical color capability is first limited by the light source itself. If it's good, then there is the filter network used to break it up into red, green and blue. Additional limitations may be imposed along the optical path, especially if the light is recombined before being projected. In theory, a Light Valve projector should have the capability of displaying better color quality, at much higher light levels than a CRT based projector.

Line Doubler
An Improved Definition Television (IDTV) feature that doubles the number of scan lines in a video picture to produce twice the apparent resolution of a normal video picture. It presents twice as many lines, in a fixed period of time, as would be displayed by the NTSC source. The process is accomplished by storing both video fields in digital memory and then displaying them both simultaneously. This fills the space between the original lines, making them less noticeable and increases the brightness of the picture. Line doubling requires that the display device be able to scan lines at twice the normal rate. For NTSC video, each field of 262.5 lines is doubled to create a 525-line non-interlaced screen scan. The same process applies to PAL, except that the field is 312.5 lines which becomes 625 when doubled. In the 525 line NTSC signal there are 262.5 lines; 240 active lines, traced on the picture in a 60th of a second. The other half of the lines making up a complete picture are traced onto the screen, in between the first set, in the next 60th of a second. NTSC is an interlaced system. The two halves are interlaced together to form a complete picture. In its simplest form, a line doubler is a line accumulator. It will store all 525 lines into a memory over a 30th of a second, then read all of them out in the next 60th of a second. Twice as many lines are presented for a given period of time. The horizontal line frequency is doubled. In the process the interlaced picture is converted to a progressively scanned image. All 480 active lines are presented with each pass of the beam from top to bottom of the picture. Under the right circumstances, vertical resolution is now 480 lines and doesn't change with vertical motion.

A term describing the output-amplitude versus input-amplitude characteristics of transducers and signal-processing device

The straightness of a frequency response curve as an indication of true or accurate sound reproduction. Describes the accuracy with which a component's output signal tracks the input signal.