Analog vs Digital - When the video signal information is sent from the computer CPU to the computer video card it is sent in digital. Because CRT monitors were analog based devices, the CRT monitors needed something to convert the video signal to analog so it could process the information. It became the job of the video card inside the computer to take the digital information being sent from the computer and turn the digital information coming into analog. Once the video card converts the digital information into analog it then sends the video signal to the monitor.

LCD displays on the other hand are digital devices and are capable of operating using video information in digital. In order to be compatible with todays video cards that send out analog signalling, LCD displays have circuitry built into them that takes the analog signal coming in from the video card and converts the signal to digital. So what we have is a signal that originates at the CPU as digital then is converted to analog by the video card inside the computer, sent through the video card as analog, and then converted back to digital by a controller card inside the LCD.

Enter DVI (digital visualization interface)- DVI is the standard for processing the video signal all the way from the CPU to the LCD in ts original digital format without converting it to analog and back to digital. The result is a much simpler and cleaner way to process the information. The video signal was, and still is in most cases, sent to the monitor as an analog signal where the CRT monitor would take that signal and process it.

Pixel Pitch - is the equivelant of the dot pitch of the CRT monitor. The smaller this number, the closer together each pixel is.

Pixel redraw - Each pixel in an LCD is given a signal by the control circuitry to turn on and offf each rescreen refresh, which happens between 60 and 120 times per second. The most sophisiticated the circuitry and design th efaster the LCD is able to turn its pixels on an doff. In the LCD world this on and off cycle is call "rise" and "fall". The samaller the number, the faster the pixel is able to rise and fall so that it is ready for the next cycle. In the most recent generation of LCD screens the rise and fall rates were about 40ms to 50ms (milliseconds). Our digital screens have pixel rise and fall rates of 25ms and some even are at 19ms.

Where the fast pixel redraw becomes especially critical is in motion video where every pixel needs to change its color on every screen refresh. Screns with the faster pixel refresh speeds are going to be able to return to their static state faster so that they can be ready to deliver the next screen. Because motion video is always moving a screen with a faster pixel refresh speed is going to deliver a more natural If the pixels are very fast, the pixel is able to rise and fall in time to be ready for the next image the amount of time it takes for each pixel to turn off and back on. The smaller the number the more quickly the screen is able to draw a new image on the screen. As you can see in our specifications, most of our screens feature 25ms redraw times. The benefit of this feature is a more solid pricture and is especially apprecitated in motion video applications which require fast screen redraw.

Brightness - most higher quality screens achieve a level of 235 or greater. Flat panel LCDs with low brightness levels will typically look weak and will not stand out in high ambient light enviroments.

Contrast ratio - is one of the very key specifications of any LCD display and is what is needed to deliver a brilliant color.

Viewable angle - this is extremely important in multi monitor computing in that it enables you to view a screen from an angle without it fading and appearing weak. Most screens feature 170 degree viewing from both up and down and well as left and right directions and at a minim are 160 degrees.


absolute white – In theory, a material that perfectly reflects all light energy at every visible wavelength. In practice, a solid white (with known spectral data) that is used as the "reference white" for all measurements of absolute reflectance.

achromatic – A neutral color (white, gray, or black) that has no hue. See hue.

ACR/NEMA – American College of Radiology/National Electrical Manufacturers Association.

active matrix – A liquid crystal display structure in which switching transistors or diodes are attached to each pixel to control the on/off voltage. It produces a brighter and sharper display with a broader viewing angle than a passive matrix display. Also known as AMLCD (active matrix liquid crystal display). See TFT (thin film transistor).

additive primaries – In color reproduction, red, green, and blue. When lights in these colors are combined in equal amounts, they produce the visual sensation of white light. When these are combined at varying intensities, a range of different colors is produced. Combining two primaries at 100% produces a subtractive primary, either cyan, magenta, or yellow. See subtractive primaries.

alignment layer – A thin film layer that is applied by spin coating. This thin film is then treated to impart a desired direction at which the liquid crystal molecules will attach and align. See buffing.

amorphous silicon (a-Si) – A semiconductor material that is used to make the thin film transistors (TFTs) layer of an active matrix LCD.

aperture ratio – The ratio between the transmissive portion of the pixel and its surrounding electronics, also known as fill factor. Generally, this is a limiting factor for luminance, the higher the aperture ratio; the brighter the luminance.

aspect ratio – The width-to-height ratio of the active area of a display. Standard U.S. video has an aspect ratio of 4:3.

backlight – The light source for a transmissive LCD. Basically, two techniques are used in transmissive LCD designs, direct lighting and side lighting. Direct-lit backlights use CCFTs (cold cathode fluorescent tubes) and a diffuser panel directly in back of the LC (liquid crystal) layer. Side-lit backlights use CCFTs and a light pipe on one or more of the edges of the display.

black – Ideally, the complete absorption of incident light; the absence of any reflection. In the practical sense, any color which is close to this ideal in a relative viewing situation, i.e., a color of very low saturation and of low luminance.

brightness – The dimension of color that is referred to an achromatic scale, ranging from black to white, also called lightness or luminous reflectance. Because of confusion with saturation, the use of this term should be discouraged.

buffing - A technique where the alignment layer on the LCD substrate is rubbed in one or more directions. This process aligns the liquid crystal molecules parallel to the buffing direction. See alignment layer.

Candelas (cd/m2) – An international unit of luminous intensity per projected area normal to the line of observation. Luminance may be described in units of Candelas per square meter, or nits.

CCFTs (cold cathode fluorescent tubes) – These are the fluorescent tubes that provide the light for the LCD unit. These tubes are generally very thin, approximately 2 mm in diameter. See fluorescent lamp.

chromatic – Perceived as having a hue; not white, gray, or black.

chromaticity – That part of color specification, which does not involve illuminance. Chromaticity is two-dimensional and specified by pairs of numbers such as dominant wavelength and purity.

chromaticity coordinates, CIE – The ratios of each of the three tristimulus values X, Y, and Z in relation to the sum of the three: designated as x, y, and z respectively. They are sometimes referred to as the trichromatic coefficients. When written without subscripts they are assumed to have been calculated for Illuminant C and the 2° (1931) standard observer unless specified otherwise. If they have been obtained for other illuminants or observers, a subscript describing the observer or illuminant should be used. For example, x10 and y10 are chromaticity coordinates for the 10° observer and Illuminant C.

chromaticity diagram, CIE x,y – A two-dimensional graph of the chromaticity coordinates, x as the abscissa and y as the ordinate, which shows the spectrum locus (chromaticity coordinates of monochromatic light, 380 nm-770 nm). It has many useful properties for comparing colors of both luminous and non–luminous materials.

CIE (Commission Internationale de l'Eclairage) – The International Commission on Illumination, the primary international organization concerned with color and color measurement.

CIE chromaticity coordinates – The ratios of each of the tristimulus values of a color to the sum of the tristimulus values. In the CIE systems they are designated by x, y, and z.

CIE standard observer – A hypothetical observer having the tristimulus color-mixture data recommended in 1931 by the CIE for a 2° viewing angle. A supplementary observer for a larger angle of 10° was adopted in 1964. If not specified, the 2° standard observer should be assumed. If the field of view is larger than 4°, the 10° standard observer should be used.

column driver – Small electronic circuits that provide voltages to the individual sub-pixel through the source lines. These are generally 8-bit driver circuits that provide 256 unique values per sub-pixel.

color temperature – A measurement of the color of light radiated by an object while it is being heated. This measurement is express in terms of absolute scale, or degrees Kelvin. Lower Kelvin temperatures such as 2400° K are red; higher temperatures such as 9300° K are blue. Neutral temperature is white, at 6504° K.

contrast – The level of variation between light and dark areas in an image.

contrast ratio – The ratio of intensity between the brightest white and the darkest black of a particular device or a particular environment.

convergence – Alignment of the vertical and horizontal lines in an image.

DICOM – (Digital Imaging and Communications in Medicine). The DICOM standard contains a display function standard.

digital driving level (DDL) – A digital value which given as input to a display system produces a luminance. The set of DDLs of a display system is all the possible discrete values that can produce luminance values on the display system. The mapping of DDLs to luminance values for a display system produces the characteristic curve of that display system. The actual output for a given DDL is specific to the display system and is not corrected for the grayscale standard display function.

double-domain – A technique used to improve the viewing angle where multiple alignment directions are produced on the same sub–pixel.

fluorescent lamp – A glass tube filled with mercury gas and coated on its inner surface with phosphors. When the gas is charged with an electrical current, radiation is produced which in turn energizes the phosphors, causing the phosphors to glow.

foot Lamberts (fL) – A unit of luminance. One foot Lambert is equal to 10.76/? (approximately 3.426) Candelas per square meter.

gamma – Screen luminance as a function of video voltage approximately follows a mathematical power function of the input video signal, the exponent of which is called gamma.

gate electrode – The "row" electrode in an active matrix LCD that controls whether a voltage is applied to a sub-pixel.

grayscale – An achromatic scale ranging from black through a series of successively lighter grays to white. Such a series may be made up of steps, which appear to be equally distant from one another or may be arranged according to some other criteria such as a geometric progression based on lightness.

hue – The main attribute of a color that distinguishes it from other colors. For example, a color may have a green, yellow, or purple hue. Colors defined as having hue are known as chromatic colors. White, black, and grays possess no hue.

IPS (In Plane Switching) – A technique of improving the viewing angle of an LCD where the liquid crystal molecules are switched in the plane of the LCD layer rather than vertical to it.

JND (Just Noticeable Difference) – The luminance difference of a given target under given viewing conditions that the average human observer can just perceive.

landscape - A page or screen orientation that is wider than it is tall.

LCD (liquid crystal display) – A display composed of liquid crystal suspended between two transparent sheets. The display is composed of pixels or other shapes which can be turned on or off with electrical stimulation. Typically, a light is passed through the LCD to illuminate the pixels.

liquid crystal – The compound found in liquid crystal displays. Liquid crystal reacts predictably when electrically stimulated. This makes it the ideal compound to turn LCD pixels "on" or "off." Liquid crystal is sometimes abbreviated as LC.

luminance – A measure of the brightness or luminous intensity of light, usually expressed in units of Candelas per square meter (cd/m2) or foot Lamberts. 1 fL = 3.426 cd/m2.

nanometer (nm) – A unit of length equal to 10-9 meter. In light measurement, the wavelength of light is measured in nanometers. The portion of the spectrum that we perceive as visible light includes wavelengths from about 380 nm to 770 nm.

nit – A unit of luminance equal to 1 cd/m2 or 0.292 ftL.

normally black – A twisted nematic LCD design where the backlight is blocked when pixels are in the unselected state. Therefore, when no voltage is applied, the screen is black.

normally white – A twisted nematic LCD design where light is transmitted when pixels are in the unselected state. Therefore, when no voltage is applied, the screen is white.