Global Home
About Optoma News Products ProScene Solutions Service Partners Where to buy Reviews
Glossary   Home Theater Guide   Contact us  
Our comprehensive glossary explains the essentials of projector and home entertainment system.
< A | B | C | D | F | G | H | I | J | K | L | M | N | O | P | R | S | T | U | V | W | X | Z >

Active Matrix TFT
The most common type of LCD used in most LCD projection panels and projectors. A display in which each pixel is driven by a thin film transistor allowing a larger viewing angle, quicker response time and more color saturation.

It is a non-crystalline silicon. In amorphous TFTs, the electron mobility is low. This means the transistor must be large, making it difficult to pack pixels densely in a panel. Thus, amorphous TFTs are most suitable for relatively large LCD panels and single panel projector.


American National Standards Institute.

ANSI Lumen

The standard of measuring brightness of a display device made by American National Standards Institute. The measurement represents the average value of 9 points on the projected screen image.

Aperture Ratio
Transmission rate of light passing through pixels contained within a TFT. The higher the number the brighter the image.

Aspect Ratio

The ratio between the width and the height of a frame or a screen. The aspect ratio for NTSC video is 4:3; HDTV is 16:9.

Audio in (Stereo Input)

The jack or jacks (typically standard RCA jacks) to plug in sound coming from a computer or video source.

Audio out (Stereo Out)

The jack or jacks to hook up external (powered) speakers or a PA system.

Transmission capacity of a computer or communications channel, the greater the bandwidth, the more information or picture detail will be displayed. In video system, this value is expressed in megahertz (MHz).

The amount of light emitting from a display or projection device. The brightness of projector is measured by ANSI lumens.

Component Video
The original elements of a color picture, including the red, green, blue, and sync information. Regarded as visually superior to composite video.

Composite Video
The complete color television picture information including luminance, chrominance, blanking, and sync signals encoded into one signal.

Compression Mode
A method to reduce the resolution of the display image.

Contrast Ratio
The ratio of the brightest and darkest images a display can reproduce.

Converting from interlaced to progressive scan.

A measurement of display size. It measures from one corner to the opposite corner.

Dichroic Mirror
To separate the light into Red, Green, and Blue three primary colors for the LCD panels.

Dichroic Prism
To combine the Red, Green, and Blue lights for the projection display.

"Digital Light Processing," reflective display technology developed by Texas Instruments, using small digital-controlled mirrors. Light passes through a color filter and is sent to the DLP chip, which arranges the RGB colors into a picture projected onto a screen. Also known as DMD.

Dye Filter Optics
Dye filter optics are where each pixel on an LCD has a red, green and blue color filter that adjusts the amount of each of these colors to produce an accurate image on the screen.

Field Lens
To collimate the illumination of LCD panels and to match it with projection lens.

Defines number of cycles during a time period. Hertz (Hz) used to express the frequency of an electrical signal.

Front Surface Mirror
It is the same as the mirror function for folding the illumination lights.

Gray Scale
Special monochrome monitor capable of displaying different shades of gray.

Halogen Lamp
Low color temperature (yellow light). The lifetime is short but the light output is steady.

An analog TV signal in the U.S. has 525 scan lines for the image, and each image is refreshed every 30th of a second (half of the scan lines are painted every 60th of a second in what is called an interlaced display). 480 of 525 scan lines are used to hold the picture. We can also call it 480i.
The formats used in HDTV are as followed:
480i - 640 x 480 pixels interlaced
480p - 640 x 480 pixels progressive
720p - 1280 x 720 pixels progressive
1080p - 1920 x 1080 pixels progressive

Hertz (Hz)
Cycles per second. It is a measurement of frequency. 1 Hz=1 cycle per second.

Hot Mirror
Rejects the unneeded infrared rays that will heat the LCD panel and let visible light pass through.

Input /Output (I/O)
The process of transferring data to and from a computer-controlled system using communication channels, operator interface devices, data acquisition devices, or control interfaces.

Integrator Lens
To make the display image more uniform.

Integrator Lens Interlaced
Every other line is scanned during each total vertical (full) screen refresh.

A rapid, small shift in image positions.

A type of distortion in which the displayed image is smaller at Top (or Bottom) of the screen than at the Bottom (or Top). Normally it is caused by improper projector-to-screen angle. Named for its similarity in shape to the keystone used in constructing an arch.

Keystone Correction
A device that will correct an image that has a keystone effect (wide-top and narrow-bottom problem).

Integrator Lens Interlaced
Every other line is scanned during each total vertical (full) screen refresh.

Liquid Crystal Display. Liquid crystals are activated by electric fields to produce the display image.

Line Doubler
A device intended to synthesize a picture with twice as many scan lines with or without interlacing in the final result.

Loop Through
An input signal that bypassed most of the internal circuitry and loops through the signal; is buffered and sent back out to make it available to be displayed by another display device.

It is a measurement of illumination on a screen or other surface. 1 Lumen/m2 = 1 Foot-candle.

It is a Metric measurement of light quantity. Taken from the reflection off the object illuminated. 1 Foot-candles = 10.76 lux.

Metal Halide Lamp
The lamp has high color temperature (white light). The lifetime is about 1000 hours. Type of lamp used as a light source in audio/visual equipment. Brightness steadily decreases during its life span.

Manufacture's Suggested Retail Price.

"National Television Standards Committee". The television standard for the US, administered by the Federal Communication Committee (FCC). The number of scanning lines in the luminance signal (Y) is set at 525, and the field frequency is 60 Hz. 30 frames are transmitted per second. Set in 1953.

"On Screen Display," menu displayed on the screen with different options that users could easily use to adjust the display's picture.

Output Fresnel Lens
To coordinate with illumination system, the image from arc of lamp will be projected to projection lens.

"Phase Alternative by Line". The PAL system uses 625 scanning lines and a field frequency of 50 Hz., 25 frames are transmitted per second. The standard color system used throughout England, Western Europe, Scandinavia, South Africa and Australia. PAL-M is the standard system in Brazil.

When you display a higher resolution image by moving your picture or image left, right, up, or down to see parts not shown in the display area.

Passive Matrix

A display by which each row and column are overlapped or addressed in turn. Passive matrix has a smaller viewing angle, slower response time and pseudo color compared to active matrix.


A unique position on a display that consists of a single dot or group of three dots (red, green and blue). Total display pixels are usually expressed in horizontal x vertical dimension (e.g., 640x480).

Type of TFT material for high-density displays. Has greater electron mobility than other common TFT materials.

Polysilicon TFT

It is a type of LCD technology that allows more light at high temperatures through the LCD.

Progressive Scan

Progressive scan means drawing the odd and even scan lines in order without interlacing. Progressive scan by itself does not improve resolution. We still have the same 480 (for NTSC) illuminated scan lines' worth of picture detail. One reason for progressive scan is to reduce flicker.

Pseudo Stereo

Creates a stereo like sound from a mono source in the EzPro projector.

The spherical reflector is used to reflect the divergent visible light beams from the lamp.

Refresh Rate
It is the number of times per second, during which a displayed image is regenerated, expressed in Hz. A low vertical refresh rate produces visible flicker.

Relay Lens

To relay the blue light to the LCD panel so that the illumination condition of it could be the same as the other two color.


The number of pixels per image area expressed by Horizontal number of pixels x Vertical number of pixels (e.g., 640x480). The more pixels the display systems can address the higher-quality image with more detail.

Response Time
The time it takes for a pixel to turn on and off. Response time is a good indication of how fast motion such as video or computer animation will appear on the projected image.


"Red, Green, Blue," primary colors used to make color spectrum.

The spherical reflector is used to reflect the divergent visible light beams from the lamp.

Serial Port
A data I/O port on the computer enabling other devices or computers to link with the computer. Also referred to as RS-232C or COM port.


The apparent image resolution.

Spatial Stereo

Surround sound quality mode in the EzPro projector.

SVGA Resolution
"Super Video Graphics Array" which represents 800 x 600 pixels.


A video signal that separates luminance (Y) and chrominance (C) signals. Generic name is Y/C, applied to S-VHS or Beta ED.

"Super Extra Graphics Array" represents 1280 x 1024 pixels.


The synchronization or timing signals of a video signal that ensure accurate picture scanning in both the horizontal and vertical planes.

The spherical reflector is used to reflect the divergent visible light beams from the lamp.

Throw Distance
Length of the projection beam needed for a projector to produce image of a particular size.

Throw Ratio

It represents the ratio between projection distance to the width of projected image.


The percent of the light that is transmitted off the LCD panel.

"Triple Super Twist Nematic". It is a technology used to make Active Matrix LCD panels wherein each pixel has its own transistor switch.

UHP lamp
Ultra High Performance projector lamp proved up to three times longer lamp life than traditional metal halide bulb.

"Video Electronics Standards Association". A non-profit group of companies organized to define and improve computer graphics standards. It set the standardized refresh rate of 72Hz for SVGA (800x600) and VGA (640x480).

VESA Standard
A set of display specifications agreed upon by the VESA organization, usually referred to resolution and vertical refresh rate.

VGA Resolution

"Video Graphics Array" represents 640x480 pixels.

Viewing Angle

The angle, looking from the left, right, above and below the display, over which a display can be seen.

Wide Angle Lens
A lens that will project a larger image on a screen at a closer distance than a standard lens will project.

XGA Resolution
"Extended Graphics Array" represents 1024 x 768 pixels

Zoom Lens
The lens allows the user to make his display images smaller or larger.

back to top