A

ANSI Lumens A standard for measuring light output, used for comparing projectors. Unfortunately, there are enough variables, that the eye will often disagree radically with the ANSI rating. At best, ANSI lumens do fairly well comparing "apples" to "apples". If however one projector uses halogen lamps and another metal-halide, the halogen projector will seem noticeably dimmer even if the two units rate the same. Other variables will affect the end result, including type of LCD technology (active matrix TFT, Poly-Si, passive), the type of overall technology (LCD vs.DLP vs. CRT), contrast ratios etc.

Aspect Ratio The most popular aspect ratio is 4:3 (4 by 3). Early television and computer video formats are in a 4:3 aspect ratio, which means that the width of the image is 4/3 times the height. Examples: A 15 inch monitor is 12 inches wide by 9 inches high (9 x 4/3 = 12). A resolution of 640x480 is a 4:3 format (480 x 4/3 = 640). Other formats are 5:4 used by the 1280x1024 SXGA resolution, 16:9 is used by HDTV, and 3:2 for 35mm slides.

B

Back Room Projector A projector with a "long-throw" lens designed to be used from the far back of the room, often in a projection booth, balcony, or back of an auditorium. Panasonic have lenses available for "long-throw" applications.

Backlit Refers to a remote control, or on-projector control panel that has buttons and controls that are illuminated. This is a major asset when using the projector in a darkened or semi-darkened room. As projectors have become brighter, room lights tend to stay on, so backlit controls are no longer so important to many users.

Built-in loop through The image being shown can be duplicated on another projector or monitor screen. Also known as ?Monitor Redrive?.

C

Carry-on Case Refers to a projector with carrying case that fits into the overhead bin or under the passenger seat of an airline. A projector case that does not fit these conditions will need to be checked in as luggage, and ride in the cargo area of the aircraft. Make sure you have a good hard case when checking a projector in as luggage. A projector is a delicate device that can have its LCDs misaligned when not handled properly.

Composite Video Signal The combined video picture signal, including vertical and horizontal blanking and synchronizing signals.

Compressed Resolution A method of reducing data from a higher resolution to enable images to be projected by a projector with lower true resolution. Most SVGA (800x600) projectors offer compression capabilities for handling images from XGA (1024x768 pixels)
i.e. a higher resolution than their true (or native) resolution.
Compressed SXGA Found on XGA projectors, compressed SXGA handling allows these projectors to handle up to 1280x1024 SXGA resolution. Most owners of XGA projectors that use the compressed SXGA are workstation users (SUN; SGI; IBM; HP)

Compressed XGA Found on SVGA projectors, compressed XGA handling allows these projectors to handle 1024x768 XGA resolution.

Contrast Ratio The ratio between the whitest and blackest portions of an image. The greater the contrast ratio the greater the ability of a projector to show subtle colour details and tolerate extraneous room light.

D

Diagonal A method of measuring and describing the size of a screen or a projected image - from one corner to the diagonally opposite corner. A 9ft high, 12ft wide screen has a diagonal of 15ft.

DLP Digital Light Processing, a method of transmitting computer and video signals through a projector, invented by Texas Instruments Ltd. The technology uses a Digital Mirror Device (DMD) mounted on a hinge between two posts, which can be turned 'on' by charging an electrode. By arranging over a million mirrors on a chip the size of a postage stamp and combining a lamp system, it is used to create the DLP system - replacing the three TFT-panel system in LCD projectors. With a mirror 'on', the light is reflected out through the lens; when 'off' it is diverted to a light absorber. The result is brighter pictures and simpler optics, enabling projectors to be smaller and lighter than LCD equivalents.

F

Focal Length The 'length' of a lens - usually measured from the image (slide, film or TFT panel) to the front surface of a lens. This is directly related to the image size and the projection distance.

H

High Gain Screen A screen that uses one of many methods to collect light and reflect it back to the audience, to increase the brightness or 'gain' of the image over that produced by a white wall or semi-matt screen.

I

Infra-red Remote Cordless remote control, commonly supplied with LCD projectors, TV, video and audio equipment. It transmits an infra-red signal which needs a clear 'line of sight' to the receiver on the equipment. Doesn't interfere with radio frequency transmissions.

Invert Image 'Invert image' flips the image to enable a projector to be ceiling-mounted upside down.

K

Keystoning 'Keystone' distortion is caused when the projected image is not perpendicular to the screen. If the top of the screen is further from the projector lens than the bottom, the image takes on a distracting 'wedge' or keystone shape. Many LCD projectors provide built-in electronic keystone correction to ensure a correct rectangular image. With an OHP, it can be avoided by tilting the screen so it is perpendicular to the projected beam.

L

Laser Pointer A hand-held pointer containing a battery-powered laser, which can project a small, red (typically), high intensity point of light that is immediately very visible on the screen. Excellent for highlighting objects or text, to make a point. Some LCD and slide projectors are supplied with an integral laser pointer in their remote control.

LCD LCD stands for liquid crystal display and comes in many forms, sizes, and resolutions. Its primary purpose is to present a digital image for viewing. A common use of LCDs is as a display on a notebook computer.

LCD Projector A device that integrates a light source, an optical system, electronics and an array of transparent LCD 'panels' to project an image generated by a computer or video device onto a wall or screen for large image viewing.

Long Throw Lens A lens designed for projection from the back of a room, or rather the back of a long room. Long throw lenses would be used a projection booth in the back of a theatre, etc. A typical long throw lens might have to be 50 to 100 FT back to project a 10FT diagonal image.

M

Maximum Image Size The largest image a projector can throw in a darkened room. This is usually limited by focal range of the optics.

Menu-Driven Refers to the type of controls on a projector. A typical menu-driven system, will first offer a menu of major categories such as Computer, Video, Audio, Display, Options. After selecting Computer, you will get another menu of choices with items like brightness, contrast, number of colors, color balance, sync. Select one of those and you can then adjust it. Many projectors which are menu driven, also offer the most widely used functions in a non-menu fashion, such as have separate buttons on the remote for volume, brightness, and contrast, as well as switching between channels/sources.

Metal Halide Lamp The type of lamp used in many medium and all high-end portable projectors. These lamps typically have a "half-life" of 1000-2000 hours. That is they slowly lose intensity (brightness) as they are used, and at the "half-life" point, they are half as bright as when new. These lamps output a very "hot" temperature light, similar to mercury vapour lamps used in street lights. Their whites are extremely white (with slight bluish cast) and make halogen lamp whites look yellowish by comparison.

Mid-Room Projector Designed to sit not too close or far from the screen, for a 10ft screen, typical placement is 12.5 to 25ft away. Most mid-room projectors have zoom lenses.

Minimum Distance The closest position that a projector can focus an image onto a screen.

N

NTSC The United States broadcast standard for video and broadcasting. An older standard and lower resolution than systems used in most of the world.

O

OHP The common abbreviation for overhead projector.

Overhead Projector (OHP) A device consisting of a light source, a transmissive or reflective platform and a focusable lens assembly. An OHP is designed to project images from transparencies up to 12" x 12" (usually A4) onto a screen. Although regarded by many as 'old technology,' the simplicity and ease of use of the OHP offers numerous benefits. It allows pre-prepared transparencies to be used and enables a presenter to command attention by writing or annotating in colour on to sheets of clear film in real time.

In many cases it the OHP is being replaced by the video visualiser (electronic OHP) which transmits images of solid objects, documents and written notes to an electronic projector or monitor screen via a fixed CCD video camera.

P

PAL A European and international broadcast colour standard for video and TV broadcasting. Higher resolution than NTSC.

Panel Also known as a projection panel, LCD projection panel, or plate. The panel is the predecessor of today's projectors. It is slightly larger and heavier than a notebook computer and the LCD it uses to produce an image is very similar to that of the notebook computer. Because panels lack their own light source, they are designed to sit on top of a overhead projector (OHP)

Passive Matrix LCD The original LCDs, these are controlled by a single processing system for the whole screen, unlike active and poly-si, which have discrete circuits for each pixel. This results in a panel with inferior colour dynamics and contrast (typically 15:1). They are also slow to react to changing signals. On passive laptop computers, the cursor (or anything else) moving on the screen, becomes invisible until you stop moving it (submarining). Very few projectors use any type of passive matrix display.

Plasma Screen A plasma screen is a 'sandwich' of tiny gas cells between two special glass sheets. When activated by an electronic signal the cells illuminate to produce vivid pinpoints of coloured light (pixels). These create sharp, evenly-illuminated pictures which retain their brightness and contrast across a very wide viewing angle.

Power Zoom A motorised lens with the zoom 'in' and 'out' controlled by a built-in motor, usually adjusted from the projector's control panel or from the remote control.

Projection Distance (or 'Throw') The distance from the front surface of a projector lens to the centre (focal point) of the screen. The greater the distance, the larger the image.

Q

QXGA QXGA is used to define a specific display resolution. Resolution is defined by the number of individual dots that a display uses to create an image. These dots are called pixels. A QXGA display has 2048 horizontal pixels and 1536 vertical pixels giving a total display resolution of 3,145,728 individual pixels that are used to compose the image delivered by a projector. A QXGA display has 4 times the resolution of an XGA display.

R

Rear Screen Projection Projection on to an opaque screen, with the projector placed behind the screen, invisible to the audience. A wide choice of rigid and flexible screen materials are available - plus a range of folding, portable rear-projection screens. As the image is not 'reflected' off the screen surface, but viewed through the screen, images are subjectively much brighter than those from front-projected screens. Where space behind the screen is limited, a projector with a short throw lens can installed. In very confined areas, a surface-silvered mirror can be used to artificially increase the projection distance.

Resolution The first specification to look for in selecting a projector is the resolution. The figure is given in horizontal pixels x vertical pixels. The popular standards are: VGA (640x480), SVGA (800x600), XGA (1024x768) and SXGA (1280x1024).

Reverse Image Reverse image is a feature found on most projectors which flips the image horizontally. When used in a normal forward projection environment text, graphics, etc, are backwards. Reverse image is used for rear projection.

RGB Red, Green, Blue; the normal type of monitor used with computers, examples of usage: RGB input or output often referred to as Computer input or output.

S

S-Video (Also referred to as Super-VHS and S-VHS) A video transmission standard that uses a 4 pin mini-DIN connector to send video information on two signal wires called luminance (brightness; Y) and chrominance (colour; C). S-Video is also referred to as Y/C. A composite signal on standard VCRs has the Y and C information combined into one signal. The advantage of having luminance and chrominance separated is that a comb filter is not needed inside the video projector to separate the signal into the luminance and chrominance components. The result is much improved picture resolution when compared to playback from standard VHS.

Short Throw Lens A lens designed to project the largest possible image from short distance.

SMARTBoard Electronic writing boards which can be linked direct to a computer. Using special pens, everything written on the board can be captured and saved on the computer. When used as a screen for an LCD projector, the board becomes an interactive monitor, allowing computer applications to be controlled live by touching the surface of the board and using your finger as the 'mouse'.

SVGA SVGA is used to define a specific display resolution. Resolution is defined by the number of individual dots that a display uses to create an image. These dots are called pixels. An SVGA display has 800 horizontal pixels and 600 vertical pixels giving a total display resolution of 480,000 individual pixels that are used to compose the image delivered by a projector.

SXGA SXGA is used to define a specific display resolution. Resolution is defined by the number of individual dots that a display uses to create an image. These dots are called pixels. An SXGA display has 1280 horizontal pixels and 1024 vertical pixels giving a total display resolution of 1,310,720 individual pixels that are used to compose the image delivered by a projector.

T

TFT Thin Film Transistor

U

UXGA A UXGA display has 1600 horizontal pixels and 1200 vertical pixels giving a total display resolution of 1,920,000 individual pixels that are used to compose the image delivered by a projector

V

Video Visualiser (Visual Presenter) An electronic OHP which transmits images of solid objects, documents and written notes (or transparencies) to an electronic projector or monitor screen via a fixed CCD video camera. Usually portable, with integral lighting and frequently integrated in bespoke presentation room systems - also ideal for the live transmission of images via videoconferencing.

A VGA display has 640 horizontal pixels and 480 vertical pixels giving a total display resolution of 307,200 individual pixels that are used to compose the image delivered by a projector. (see SVGA)

X

XGA A XGA display has 1020 horizontal pixels and 768 vertical pixels giving a total display resolution of 783,360 individual pixels that are used to compose the image delivered by a projector. (see SVGA)

Z

Zoom Lens: A lens with a variable focal length providing the ability to adjust the size of the image on a screen by adjusting the zoom lens, instead of having to move the projector closer or further.

Zoom Lens Ratio The ratio between the smallest and largest image a lens can projector from a fixed distance. For example, a 1.4:1 zoom lens ratio means that a 10 foot image without zoom would be a 14 foot image with full zoom.