Liquid crystal glossary

Below you can find a list with the explanation of a large number of terms related to liquid crystals, display, projectors and optics in general.

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Active Area/Effective Area: In the viewing area of the LCD glass, the dimensions of the perimeter of the conductive area.

Active center: Location of the unpaired electron on a free radical where reactions take place.

Active Matrix: Term used to describe LCD Displays which have micro-transistors that "open" and "close" each pixel.

Active Matrix TFT: A common type of LCD used in laptops, cameras, and LCD projection panels that were produced in the late 1980s to early 1990s. A typical active matrix TFT display is a single panel of LCD glass that controls all three primary colors. TFT displays are noted for their quick response time and their ability to display full motion video and animations without image ghosting.

Alignment layer: A layer and/or surface treatment applied to the boundary of a liquid crystal cell to induce a particular director orientation. For example, a layer of polyimid buffed in one direction induces alignment parallel to the buffing direction, or a surfactant may be polymerized on a boundary surface to induce perpendicular alignment.

Amorphous: Irregular; having no discernible order or shape. In the context of solids, the molecules are randomly arranged, as in glass, rather than periodically arranged, as in a crystalline material.

Amorphous polymers: A glass-like structure with tangled chains and no long-range order.

Amphiphilic: A molecule with a hydrophilic head and a hydrophobic tail. That is, a molecule that has one end which attracts water and one end which repels water.

Anamorphic Lens: An anamorphic lens is a lens that has different optical magnification along mutually perpendicular radii. This provides the ability to project a source image of one aspect ratio, such as 4:3, into a different aspect ratio, such as 16:9, by using different magnifications for the horizontal and the vertical dimensions of the projected image.

Anisotropic: Having properties which vary depending on the direction of measurement. In liquid crystals, this is due to the alignment and the shape of the molecules. See also isotropic.

ANSI Contrast: See contrast ratio

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, including type of LCD technology (active matrix TFT, Poly-Si, passive), type of overall technology (LCD vs.DLP vs. CRT), contrast ratios, etc. all effect the end result.

Aperture: In television optics, it is the effective diameter of the lens that controls the amount of light reaching the photoconductive or photo emitting image pickup sensor.

Aperture Correction: Compensation for the loss in sharpness of detail because of the finite dimensions of the image elements or the dot-pitch of the monitor.

Aromatic: A compound containing a series of benzene (6 Carbon) rings; so named because many have a distinctive odor.

a-Si: "Amorphous Silicon"

Aspect Ratio: Aspect ratio is the ratio of the width of an image to its height. For example, a projector with a 16:9 aspect ratio will produce an image that is 16 units wide for every 9 units high. This is also referred to as 1.78:1 meaning the width is 1.78 times the height. For example, if you want an image 40 inches high then you need a screen that is at least 40 * 1.78 inches wide or 71 inches. Other common aspect ratios are 3:2, 4:3 and 5:4.
Native aspect ratio refers to the aspect ratio of the physical displays built into the projector. For example, a 1280 x 720 pixel display has a 16:9 native aspect ratio. A display that is 640 x 360 pixels is also a 16:9 aspect ratio, but with a fourth of the resolution of the other display.
Nearly every projector today will support multiple aspect ratios; however each manufacturer must decide who their intended audience is and optimize the projector for that audience. This means each projector has a native aspect ratio that is optimized for specific viewing material. Images shown in native aspect ratio will utilize the entire resolution of the display and achieve maximum brightness. Images shown in other than native aspect ratio will always have less resolution and less brightness than images shown in native aspect ratio.

Atactic polymer: See stereoregular polymer

ATA Rated Case: A case rated strong enough to be shipped by common carrier; freight lines, UPS, FedEx, etc. Most cases of this type are easily recognized by their metal reinforced corners and handles. These cases are often referred to as "Anvil cases" bearing the name of one of the manufacturers.

Auto Balance: A system for detecting errors in color balance in white and black areas of the picture and automatically adjusting the white and black levels of both the red and blue signals as needed for correction.

Axial ratio: The ratio of the length of the molecule to the diameter of the molecule.

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Backbone: The main structure of a polymer onto which substituents are attached.

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. Many typical projectors have third party 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. Many projectors have backlit remote controls, while the number of projectors with backlit control panels is much smaller. As projectors have gotten brighter, room lights tend to stay on, so while nice, having backlit controls is no longer important to many users.

Bandwidth: The number of cycles per second (Hertz) expressing the difference between the lower and upper limiting frequencies of a frequency band; also, the width of a band of frequencies.

Bezel: A frame of plastic or metal, fitting around the LCD glass, to protect the edges of the glass.

Biaxial: Possess two directions along which monochromatic light vibrating in any plane will travel with the same velocity. The optic axis lies just between these directions.

Bilayer: A double layer of amphiphilic molecules, arranged such that either the nonpolar ends are on the inside screened by the polar ends or the polar ends are on the inside screened by the nonpolar ends, depending on whether the solvent is polar or nonpolar.

Birefringence: Also called double refraction. The property of uniaxial anisotropic materials in which light propagates at different velocities, depending on its direction of polarization relative to the optic axis. A wave with polarization perpendicular to the optic axis will exhibit an "ordinary" index of refraction, no (this is often referred to as the ordinary ray). In contrast, a wave with polarization parallel to the optic axis exhibits an "extraordinary" index, ne (the extraordinary ray). The ordinary index, no, is isotropic with respect to direction of propagation while the extraordinary, ne, varies depending on the direction of propagation with a maximum value for light traveling perpendicular to the optic axis and, of course, polarized parallel to it. The difference Δn = ne - no is also referred to as the birefringence or the optical anisotropy.

Block polymers: Polymers composed of two or more connected sequences (blocks) of homopolymers. In the simplest case, the AB diblock consists of two homopolymers, A and B, joined together.

Bond orientational order: Describes a line joining the centers of nearest-neighbor molecules without requiring a regular spacing along that line. Thus, a relatively long-range order with respect to the line of centers but only short range positional order along that line.

Branched polymer: A polymer with a chemical side chain extending from the main backbone.

Brightness: The attribute of visual perception in accordance with which an area appears to emit more of less light. (Luminance is the recommended name for the photo-electric quantity which has also been called brightness.)

Buffing: To give the inner glass surfaces of a liquid crystal cell a texture so as to align the liquid crystal molecules in a certain direction parallel to the surfaces.

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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 as luggage, and ride in the cargo area of the airline. Make sure you have a good hard case when checking a projector as luggage. A projector is a delicate device that can have its LCDs misaligned when not handled properly.

Cell: See subpixel.

Cell Gap: The space containing liquid crystal fluid between the two pieces of glass.

Chain polymer: A polymer in which the repetition of units is linear. The monomers are linked end to end forming a single straight polymer.

Chain axis: The straight line parallel to the directions of chain extension, connecting the centers of mass of successive blocks of chain units, each of which is contained within an identity period.

Chain polymerization: A chain reaction in which the growth of a polymer chain proceeds exclusively by reaction(s) between monomer(s) and reactive site(s) on the polymer chain, with regeneration of the reactive site(s) at the end of each growth step.

Chiral molecule: A molecule that is not identical to its mirror image. This gives a chiral substance its characteristic twisted shape, due to the fact that its molecules do not line up when combined.

Cholesteric liquid crystals: Also known as Chiral Nematic. Similar to the nematic phase, however, in the cholesteric phase, molecules in the different layers orient at a slight angle relative to each other (rather than parallel as in the nematic). Each consecutive molecule is rotated slightly relative to the one before it. Therefore, instead of the constant director of the nematic, the cholesteric director rotates helically throughout the sample. Many cholesterol esters exhibit this phase, hence the name cholesteric. See also chiral.

Cholesteric mesophase: Nematic liquid crystals with chiral centers form in two dimensional nematic-like layers with directors in each layer twisted with respect to those above and below so that the directors form a continuous helix about the layer normal. Many cholesteric esters exhibit this phase, hence the name cholesteric. This mesophase exhibits circular dichroism and is optically active.

Chromatic Aberration: An optical defect of a lens which causes different colors or wave lengths of light to be focused at different distances from the lens. It is seen as color fringes or halos along edges and around every point in the image.

Chromaticity: The color quality of light that is defined by the wavelength (hue) and saturation. Chromaticity defines all the qualities of color except its brightness.

Chrominance: A color term defining the hue and saturation of a color. Does not refer to brightness.

Chromophoric groups: Chemical groups which have distinctive colors.

Circular dichroism: See dichroism.

Circular polarization: A condition caused by two waves whose electric field components are 90 degrees out of phase, causing an effective rotation of the electric field about an axis in direction of propagation.

Cis (configuration): A polymer configuration in which adjacent bonds are coplanar and on the same side of the carbon-carbon double bond.

Coated Optics: A variety of materials are put on to high quality lenses for several reasons. One of the key reasons is to minimize the amount of light reflected back to the lamp, and the amount of ambient light that mingles with the focused light leaving t he lens. Generally good coatings can add 15% or more to the lenses brightness. Other coatings are used for filtering colors/

Cold Cathode Backlight (CCFL): In LCD graphic modules, a type of fluorescent backlighting or edge lighting. One or more fluorescent lamps behind the LCD panel that provides the light that is either blocked (black) or passed (white) by the LCD cell.

Columnar phase: A liquid crystal phase characterized by disc-shaped molecules that tend to align themselves in vertical columns.

Colligative properties: Are those that depend on the number of species present rather than their kind.

Color Dynamics: "The whitest whites, reddest reds, etc." High color dynamics are a result of dynamic range/contrast ratio's. When we describe a unit as having excellent color dynamics, the practical description might be "rich colors, excellent definition, high contrast".

Color Temperature: A method of measuring the "whiteness" of a light source. Metal halide lamps have very high temperatures compared to halogen or incandescent lights.

Combination: A type of termination reaction which involves a free radical joining with an active growing polymer to form a stable chain and end the growth.

Component Video: Component Video is a method of delivering quality video (RGB) in a format that contains all the components of the original image. These components are referred to as luma and chroma and are defined as Y'Pb'Pr' for analog component and Y'Cb'Cr' for digital component. Component video is available on some DVD players and projectors.

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

Compressed Resolution: Most projectors automatically accept images that are of greater resolution than the native (true) resolution of the projector. The resulting image is scaled to fit the native resolution of the projector using a variety of scaling algorithms. Not all projectors use the same compression algorithms; therefore, the quality of compression can vary. The nature of compression in a digital device means that some image content is lost.

Compressed SVGA: Unlike CRT based monitors, LCD and DLP projectors only have one "true" resolution. Most projectors out there are VGA (640x480) resolution. To project an 800x600 image to a VGA projector, the original 800x600 signal must be compressed down to VGA. This is done by interpolating the data, and trying to best display all the information with only two thirds of the pixels (307,000 vs 480,000). The resulting image gives you the SVGA page size, but some sacrifice of image quality. For the vast majority of people with SVGA laptops or desktops, they will have more satisfying results, outputting VGA to a VGA projector.

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...) The typical uses f or these workstations are medical, life sciences, engineering and so on.

Compressed XGA: Found on SVGA projectors, compressed XGA handling allows these projectors to handle 1024x768 XGA resolution. How good the compressed XGA is on a given model is a key factor in the decision process for most people choosing an SVGA projector. This is true as the market shifts from SVGA laptops to those with XGA screens.

Configuration: The geometrical arrangement in polymers arising from the order of atoms determined by chemical bonds.

Configurational unit: A constitutional unit having one or more sites of defined stereisomerism.

Configurational base unit: A constitutional repeating unit, the configuration of which is defined at one or more sites of stereoisomerism in the main chain of a polymer chain.

Configurational repeating unit: The smallest set of one, two or more successive configurational base units that prescribes configurational repetition at one or more sites of stereoisomerism in the main chain of a polymer molecule.

Conformation: The geometrical arrangement in polymers arising from rotation about adjacent carbon-carbon single bonds.

Conformation repeating unit: The smallest unit of a polymer chain with a given conformation that is repeated along that chain through symmetry operations.

Contour length: The maximum end-to-end distance of a linear polymer chain. For a single-strand polymer molecule, this usually means the end-to end distance of the chain extended to the all-trans conformation. For chains with complex structure, only an approximate value of the contour length may be accessible.

Contrast Ratio: The ratio of the luminance in a white square centered on the screen and the black surrounding area. The larger the contrast ratio the greater the ability of a projector or display to show subtle color details and tolerate extraneous room light. There are two methods used by the projection industry:

Full On/Off contrast: measures the ratio of the light output of an all white image (full on) and the light output of an all black (full off) image.

ANSI contrast: is measured with a pattern of 16 alternating black and white rectangles. The average light output from the white rectangles is divided by the average light output of the black rectangles to determine the ANSI contrast ratio. When comparing the contrast ratio of projectors make sure you are comparing the same type of contrast.

Full On/Off contrast will always be a larger number than ANSI contrast for the same projector.

Copolymer: Polymers that are derived from more than one species of monomer. Polymers having monomeric units differing in constitutional or configurational features but derived from a single monomer, are not regarded as copolymers.

Statistical copolymers: Are copolymers in which the sequential distribution of the monomeric units obeys known statistical laws; e.g., the monomer sequence distribution may follow Markovian statistics of zeroth (Bernoullian), first, second, or a higher order. Statistical copolymers are named: poly (A-stat-B)

Random copolymers: Is a special case of a statistical copolymer. It is a statistical copolymer in which the probability of finding a given monomeric unit at any given site in the chain is independent of the nature of the neighboring units at that position (Bernoullian distribution). Random copolymers are named: poly(A-ran-B)

Alternating copolymers: A copolymer comprising two species of monomeric units distributed in alternating sequence: the arrangement -ABABABAB- or (AB)n represents an alternating copolymer. Alternating copolymers are named:poly(A-alt-B)

Periodic copolymers: Copolymers where the monomeric units appear in an ordered (for example, ABC) sequence. Periodic copolymers are named: poly(A-per-B-per-C)

Block copolymers: A polymer comprising molecules in which there is a linear arrangement of blocks, a block being defined as a portion of a polymer molecule in which the monomeric units have at least one constitutional or configurational feature absent from the adjacent portions. Block copolymers are named: polyA-block-polyB.

Graft copolymers: A polymer comprising molecules with one or more species of block connected to the main chain as side chains, these side chains having constitutional or configurational features that differ from those in the main chain. In a graft copolymer, the distinguishing feature of the side chains is constitutional, i.e., the side chains comprise units derived from at least one species of monomer different from those which supply the units of the main chain. An example: -AAAAAAAXAAAAAAAAA-BBBB and the corresponding name is polyA-graft-polyB where the monomer named first (A in this case) is the backbone (main chain, while that named second (B) is the side chains.

Cross-linking: A process in which bonds are formed joining adjacent molecules. At low density, these bonds add to the elasticity of the polymer and at higher densities, eventually produce rigidity in the polymers.

Crystallinity: The presence of three-dimensional order on the level of atomic dimensions. In polymers, the range of order may be as small as about 2 nm in one (or more) crystallographic direction(s) and is usually below 50 nm in at least one direction. Polymer crystals frequently do not display the perfection that is usual for low-molecular mass substances. Polymer crystals that can be manipulated individually are often called polymer single crystals.

Crystallization: The process of forming crystals from the melt or solution.

Primary crystallization: The first stage of crystallization, considered to be ended when most of the spherulite surfaces impinge on each other. In isothermal crystallization, primary crystallization is often described by the Avrami equation.

Secondary crystallization: Crystallization occurring after primary crystallization, usually proceeding at a lower rate.

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dB: dB or decibel, is a measure of the power ratio of two signals. In system use, a measure of the voltage ratio of two signals, provided they are measured across a common impedance.

Defects: A local break in the translational or orientational symmetry of the material.

Deformation: The condition where the director in a liquid crystalline material changes its orientation from one molecule to the next.

Degree of polymerization: The number of monomeric units in a molecule of a polymer. The DP determines many physical characteristics of the system.

Dendrimers: Highly branched molecules that have several layers of branching. These molecules exhibit a characteristic spherical shape.

Diagonal Screen: The diagonal of a screen can be computed by squaring the width, squaring the height, adding them together and taking the square root.

Diastereomers: Stereoisomers that are not mirror images of each other. They have similar chemical properties but may have vastly different physical properties.

Dichroic: A mirror or lens that reflects or refracts selective wavelengths of light. Typically used in projector light engines to separate the lamps "white" light into red, green, and blue light.

Dichroism: Refers to the selective difference in absorption between the two orthogonal components of the polarization state of light propagating in a given direction in an anisotropic medium. Generally applied to linearly polarized light. This is how a sheet polarizer works with one direction of polarization transmitted and the perpendicular directions absorbed. Circular dichroism describes the corresponding effect for circularly polarized light where one "handedness" of circularly polarized light is absorbed more strongly than the opposite "handedness." Solutions of chiral molecules will produce this effect as will cholesteric liquid crystals for wavelengths well removed from the pitch value.

Dielectric anisotropy: A condition arising when the dielectric constant parallel to the length of a mesogen, e//, is different from that perpendicular to it, e_|_. This occurs when the charge distribution along the molecule responds differently to the parallel component of the local electric field than the distribution perpendicular to the length does to the perpendicular component, yielding a difference in dielectric constants. Positive anisotropy is defined as the case where e// > e_|_, while a negative anisotropy corresponds to e_|_ > e//.

Digital Controls: High-tech SoftTouch digital controls electronically sense the slightest touch for easy adjustments of size, position and tuning at all resolutions.

Digital Light Processing (DLP): The commercial name for this technology from Texas Instruments (TI): The technology inside is often referred to as either "micro-mirrors", or DMD: It works this way: build a few hundred thousand tiny mirrors, and line them up in 800 rows of 600 mirrors each. Now attach a hinge to each of those 480,000 mirrors. Attach each of those 480,000 hinges to its own very tiny motor! Power each motor with electrostatic energy! The motors tilt their mirrors up to 20 degrees at incredible speeds. This allows the mirrors to modulate light from a lamp, and send the "modulated signal" out through a lens, on to a screen. The most amazing part of DLP micro mirrors, is the scale of size. The 480,000 mirrors (actually 580,000 are used), hinges and motors are packed onto a "wafer" a bit larger than your thumbnail.

Dipole: Two equal electric or magnetic charges of opposite sign, separated by a small distance. In the electric case, the dipole moment is given by the product of one charge and the distance of separation. Applies to charge and current distributions as well. In the electric case, a displacement of charge distribution produces a dipole moment, as in a molecule.

Director: The molecular direction of preferred orientation in liquid crystalline mesophases.

Disclination: Line defects arising from singularities in orientational order in a director field.

Discotic liquid crystal: The component disc-shaped molecules self-assemble in a way that resembles stacks of coins. The discs are stacked on top of each other to form columns, which in turn are packed on a two-dimensional, usually hexagonal, lattice.

Dislocations: Line defects arising from singularities in translational order in a crystalline lattice.

Disproportionation: Disproportionation is a method of terminating chain polymerization which involves a free radical stripping a hydrogen atom from another free radical, so that one chain stabilizes with the hydrogen, and the other with a double bond.

Distribution Amplifier: An amplifier used to maintain a clean noise free signal to the projector over significant distances. Even with good heavily shielded cables, range of video and computer signals is limited to a few dozen feet before noticeable degradation. In ceiling mount situations, where the wiring may pass along side or across electrical conduits, etc. a distribution amp may be needed with shorter distances. Many distribution amps can also split the signal into 2 or more amplified signals for driving multiple projectors, projectors and monitors.

Dot/Pixel (Picture Element): The smallest active element that forms all text and graphics on the LCD screen.

Double refraction: See birefringence.

DTV: DTV refers to the three types of digital television including Standard Definition Television (SDTV), Enhanced Definition TV (EDTV), Nad High Definition Television (HDTV).

Dual Scan Passive Matrix: Newer version of the original passive matrix technology, where the screen is controlled by two processing systems. A bit faster than "single scan," response is still horrendously slow, they cannot do multimedia or video either. Contrast remains terrible. Dual scan is used in the least expensive LCD panels.

DVI: DVI means Digital Visual Interface. DVI is a standard that defines the digital interface between digital devices such as projectors and personal computers. For devices that support DVI, a digital to digital connection can be made that eliminates the conversion to analog and thereby delivers an unblemished image. Specifications on DVI are available at

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EDTV: EDTV stands for extended definition television and is a class of digital television (DTV) that refers to the 480p format. 480p is a progressive scan video format that produces a full frame of 480 lines of video.

Elastomers: A class of polymers that have some degree of cross linking and are rubbery. Elastomers possess memory, that is, they return to their original shape after a stress is applied.

Electro-optical materials: Materials whose optical properties are changed under the application of an electric field.

Emulsion: A mixture of two mutually insoluble liquids such that one is dispersed in the other in droplets which often cause the solution to be cloudy or translucent.

Enantiomers: Molecules which exist in two nonsuperimposable mirror images, analogous to human hands. Chiral molecules are perfect physical and chemical models of each other with the exception of their rotation of polarized light and those interactions that involve other chiral systems, such as chiral molecular recognition. A racemic mixture contains equal amounts of two enantiomers and thus produces no rotation of the plane of polarization of light.

Enantiotropic liquid crystal: Exhibit the liquid crystal state both when the temperature rises from the solid state side or when it falls from the liquid state. Monotropic liquid crystals exhibit the liquid crystalline state only when the temperature changes in one direction.

Entanglement: A crossing of polymer chains, which, when subjected to a strain, remains intact and hence mechanically active.

Enthalpy: A measure of the heat energy in a system; thermodynamic systems tend to react in ways that decrease their enthalpy

Entropy: A measure of the disorder in a system; thermodynamic systems tend to react in ways that increase their entropy.

Epitaxial growth: An ordered growth of material as it is deposited on an ordered substrate, in registry with the substrate (for example, preserving elements of the crystalline order of the substrate).

Extraordinary ray: See birefringence

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Fader: The control on a projector, that allows you to control the balance of sound between the projectors internal speakers and the external speakers (PA, powered speakers). Only a couple of projectors offer this convenient feature.

Ferroelectric material: One that produces domains of spontaneous polarization whose polar axis can be reversed in an electric field directed opposite to the total dipole moment of the lattice.

Freedericksz transition: The point at which a liquid crystal changes from an aligned to a deformed state under the influence of an external electric or magnetic field.

Fibers: Characterized by having a high length to diameter ratio, that is, the length is enormously greater than the diameter. As a result of the spinning process, most of the polymer molecules are oriented along the fiber axis. In regions where polymer molecules are perfectly oriented along the axis, crystals will be formed. Nearly perfect uniaxial orientation of the macromolecules represents the basic requirement for the preparation of strong polymer fibers.

Field: One half of a video frame consisting of either all of the even-numbered scanlines or all of the odd-numbered scanlines in a frame.

FM Based Remote: A remote control that broadcasts its instructions with an FM transmitter, normally required in large rooms, thanks to long range, and no line of site requirement.

Focal Length: The distance from the surface of a lens to its focal point.

Form Factor: A general description, a major feature, or features that identify a type of projector or
category of capabilities. Example: The Epson's form factor is considered the classic road warrior machine; weight under 17 lbs, zoom lens for easy placement, enough brightness to handle a darkened auditorium, and small enough to be moved easily and qualify as carry-on luggage, even in its hard case.

Free radical: A molecule with an unpaired electron, making it highly reactive.

Free radical polymerization: The synthesis of a polymer involving the chain reaction of free radicals with monomers.

Fringed-micelle model: A model of crystallinity in which the crystallized segments of a macromolecule belong predominantly to different crystals.

Front Room Projector or Position: A unit that sits close to the screen, its short throw lens projects an image size that is about the same as the distance to the screen. 6FT diag. screen = 6FT distance. Generally the unit might be as close as 3/4 the screen size or as far as 1.2 times image size.

Full On/Off Contrast: See contrast ratio

FXL: The most popular halogen lamp in use in lower cost projectors and overhead projectors. The lamps typically last about 40 hours, however for convenience, most projectors using halogen lamps carry a spare, and a quick method of going to the backup lamp. Metal halide lamps and UHP lamps are used in most of the medium and higher priced, more powerful portables.

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Gauche: A carbon-carbon bond in the main chain of a polymer that is rotated 120 degrees out of the plane. gauche(+) denotes a rotation of +120 degrees and gauche(-) denotes a rotation of -120 degrees--both as defined by the "right hand" rule.

Ghosting: A phenomenon occurring when voltage from an energized element leaks to an adjacent OFF element and turns the adjacent element partially ON. Also, the temporary trail left by a moving object on a "slow" LCD panel.

Glass transition temperature: Tg, can be defined as the temperature at which the specific volume vs temperature plot has a change in slope. Chain motion and other local molecular motions are greatly reduced below this temperature, which is also dependant on the rate of cooling.

Grandjean texture: A specific pattern of defects found in chiral nematic liquid crystals that is caused by the chiral nature of the crystal. Named for the French scientist F. Grandjean who worked with chiral nematic liquid crystals.

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Halogen Lamps: Used in most low and medium priced projectors, these lamps last about 40 hours, with
consistent output throughout their life. Although halogens look very white compared to a normal
incandescent lamp, they are not as white as metal halide unit s. Cost of operation: Under $0.50 per hour. Most projectors using halogen lamps carry a spare lamp inside.

Hard Wired Remote: Generally a remote control is wireless, and uses infra-red transmitter. There are situations where this is not practical: Large rooms where the speaker is 35 ft or more from the projector. Rear projection, where the screen will pass some signal, but normally has the presenter pretty much tied down. Also, the presenter has to point the remote "at" the projector which often means turning away from the audience. A couple of projectors (Epson for one) offer wireless remotes that will accept a cable (hard wiring) back to the projector, assuring range and signal getting though.

HDCP: HDCP (High-bandwidth Digital Content Protection) is a method for protecting copyrighted digital content that uses the DVI (Digital Visual Interface) or HDMI (High-Definition Multimedia Interface, previously known as DVI-CE) by encrypting its transmission between the video source such as a set-top box, DVD player, or computer and the digital display device such as a projector, monitor or television. To view digital HDCP protected content, both the sending and receiving device must support HDCP.

HDMI: HDMI (High Definition Multimedia Interface) is an uncompressed, all-digital audio/video interface that supports audio/video sources such as a set-top box, DVD player, A/V receiver, and video monitors such as a digital projector or digital television (DTV). HDMI is backward compatible with DVI 1.0 specification and supports HDCP.
HDMI supports standard, enhanced, or high-definition video, plus multi-channel digital audio, and interactive controls on a single cable. It transmits all ATSC (Advanced Television Systems Committe) HDTV standards and supports 8-channel digital audio. First product releases using HDMI occurred in 2003.

Helix: The molecular conformation of a spiral nature, generated by regularly repeating rotations around the backbone bonds of a macromolecule.

Helix residue: The smallest set of one or more successive configurational base units that generates the whole chain through helical symmetry.

High Gain Screen: A screen that uses one of many methods to collect light and reflect it back to the audience, which dramatically increase the brightness of the image over a white wall or semi-matte screen. Technologies used include curved screens, special metal foil screens (some polarized), and certain glass bead screens. Prices and performance vary tremendously.

Homeotropic texture: A mesogen configuration in which the molecules are aligned normal to the boundary surfaces, as at the faces of a liquid crystal cell, as illustrated. Consequently the director will be normal to the surface. This orientation is generally obtained by the application of an electric field normal to the surface but can be achieved through surface treatment.

Homogeneous: An uniform structure or composition throughout. Having or possessing the same properties.

Homogeneous (planar) texture: A mesogen configuration in which the molecules are aligned parallel to the boundary surfaces, as at the faces of a liquid crystal cell.

Homopolymer: A polymer that is constructed of identical monomers.

Hybridization: The combination of atomic orbitals on the same atom. (Example: sp2, the composite of the "s" and two "p" orbitals.)

Hydrophilic: "Water loving"; describes a molecule which is attracted to water.

Hydrophobic: "Water fearing"; describes a molecule which is repelled by water.

Hypertext: Text that includes pointers to other text, pictures, movies, etc. "Clicking" on these links takes the reader to the object that it is pointed to. Links may point to documents on other computers connected on the Internet.

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Indentity period: The shortest distance along the chain axis for translation repetition of the chain structure. The chain identity period is usually denoted by c.

Index of refraction: Ratio of the phase velocity of electromagnetic radiation in free space divided by the phase velocity in a given medium. It is greater than one except for rather special cases.

Initiation reaction: The first step in chain polymerization. Initiation involves the formation of a free radical.

Initiator: A relatively unstable molecule that decomposes into a free radical. Used to "initiate" a polymer growth reaction.

Infra-red Remote: The traditional remote control, it transmits infra-red, like a television remote. Typical range is limited to 30 or 35 feet. Infra-red requires line of site or a bounce off of a hard surface. The presenter must pay attention to where the remote is pointed. Some projectors have a IR sensor in both the front and rear of the projector, which can help a bit. When working at or near the maximum distance pointing right at the receiver is necessary. Remember "line of sight" - a person's head, directly between your remote and the projector may be enough to render it unusable. FM (radio frequency remote mousing systems, by comparison, have two distinct advantages, no line of sight requirement, and longer range.

In-Plane Switching (IPS): A liquid crystal technology in which the alignment field is generated from electrodes located on a single substrate rather than on opposite sides like more conventional (TN) panels. The main advantages IPS are greater viewing angles and greater contrast ratio.

Interlaced Video: Video systems in which each frame of video consists of two video fields. The odd numbered lines are contained in the first field and the even numbered lines are contained in the second field. When the image is delivered to a video device such as a television, the odd and even fields are delivered at 50 or 60 fields per second and your eye sees an integrated image.

International Power Supply: A unit that can operate under a international selection of power requirements. The specs of units vary widely, but the minimum is 105-230 volts, and 50-60 cycles AC (alternating current). If you see a specification like 110v, 220v instead of a range, those ratings are usually +/- a given percent such as 10%. Some units are "self-switching" they will automatically switch to whatever power source you plug it into. Others will have to be switched (internally or externally to accommodate a difference volt age or cycle range.

Invert Image: Invert image flips the image from top to bottom, to compensate for ceiling mounting a projector upside down. Projectors typically ceiling-mount upside down, because most have "keystone" correction built in to compensate for the distortion created by "pointing up" from the table to the screen. Usual positioning has the projector about even with the bottom of the screen in a "table top position," or, even with the top of the screen when ceiling mounted.

IR Communication Standard: Many new laptops have an Infra-Red transceiver that follow a recent standard for wireless communicating with peripherals (new laser printers complying with the standard) and networks or desktop systems. If you have a laptop like this, you know the pleasure of walking into a room with a configured laser printer, and printing out documents without having to "plug-in." Only a couple of projectors are now shipping that follow this standard. This allows their remote controls to talk directly to your laptop for remote mousing. A tremendous new capability, as you are normally much closer to your computer than the projector in medium or large rooms.

Isomer: A molecule which has an identical molecular formula to another molecule, but has a different structure.

Isomorphism: Statistical co-crystallization of units having different repeating constituents, which may either belong to the same copolymer chains (copolymer isomorphism) or originate from different homopolymer chains (homopolymer isomorphism). Isomorphism is a general term; in the strict sense, the crystal structure is essentially the same throughout the range of compositions.

Isotactic polymer: See stereoregular polymer

Isotropic: Having properties that are the same regardless of the direction of measurement. In the isotropic state, all directions are indistinguishable from each other. See also anisotropic.

ITO: Indium Tin Oxide (indium oxide doped with tin). A transparent conductive material very commonly used for electrodes in displays or other applications which require conductivity along with light transmission.

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Keystone: Keystoning occurs when the projector is not perpendicular to the screen, thereby creating an image that is not rectangular.

Keystone Correction: Keystone correction makes a projected image rectangular. This can be accomplished by positioning the projector to be perpendicular to the screen. Since this is not always possible, most projectors are equipped with keystone correction that allows the image to be keystone corrected (made rectangular) by adjusting optics, making mechanical adjustments, or applying digital correction to the image. Keystone correction can be one or two dimensional and manual or automatic depending on the projector and the manufacturer.

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Laser Pointer: A small pen or cigar sized pointer, that contains a small battery powered laser, which can project a small, red (typically), high intensity beam of light that is immediately very visible on the screen. Excellent for pointing to objects or text, to make a point.

Latency: See ghosting.

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.

Lens Shift: The Lens Shift feature of a projector allows the optical lens to be physically shifted up and down (Vertical) or left and right (Horizontal). Most all lens shift mechanisms are motorized with vertical lens shift being the most popular. With a projector that has lens shift you can optically correct for keystone distorted images. It is also used to help geometrically align images when stacking projectors.

Lipophilic: Describes a molecule which is attracted to hydrocarbons.

Liquid crystal: A thermodynamic stable phase characterized by anisotropy of properties without the existence of a three-dimensional crystal lattice, generally lying in the temperature range between the solid and isotropic liquid phase, hence the term mesophase.

Living polymerization: Chain growth polymerizations proceeding in the absence of chain breaking terminations. This process can be used to produce essentially monodisperse polymers.

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 theater, etc. A typical long throw lens might have to be 50 to 100 FT back to project a 10FT diagonal image.

Lux: A standard for measuring light, numbers provided by manufacturers usually do not provide necessary additional information to compare one product to another.

Lyotropic: Materials in which liquid crystalline properties appear induced by the presence of a solvent, with mesophases depending on solvent concentration, as well as temperature. See also thermotropic

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Macromolecule: A very large molecule. Many polymers are composed of hundreds of thousands of atoms, and are thus characterized as macromolecules.

Macroscopic molecular orientation: The property that allows the orientation of liquid crystals to be seen only on a large scale and cannot seen if a single layer is compared to any other single layer.

Main-chain polymer liquid crystals: Polymer liquid crystals in which the mesogenic cores are a part of the main chain or backbone of the polymer.

Maximum Distance: Sometimes, rarely, the distance from the screen that a projector can focus the image. Most of the time, it is the manufacturer's opinion of how far from a screen the projector can be to cast an image that is useable (bright enough) in a fully darkened room. Generally this is very subjective. One projector might quote a distance that allows them to produce a 25FT diagonal image, while another, brighter projector might quote a distance that only equates to a 20FT image. Beware!

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

Maximum Resolution: Maximum Resolution refers to the highest resolution that a given projector can display. If the Maximum Resolution exceeds the Native Resolution, the image is usually scaled to match or approximate the Native Resolution of the projector. Scaling reduces the image resolution and produces some artifacts in the image that are more apparent when viewing text than graphics or video.

Melting transition temperature: The temperature at which the substance loses its translational and orientational order, changing from a solid phase to a liquid phase.

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.

Mesogen: Rigid rodlike or disclike molecules which are components of liquid crystalline materials.

Mesogenic cores: The mesogenic core is the primitive structural unit of a polymer having the requisite anisotropic shape and attractive interactions to establish long range intermolecular order in its liquid phase. That is, it is what gives a polymer liquid crystal its liquid crystal properties.

Mesomorphic substance: Another term for a liquid crystal material.

Mesophase: Equilibrium liquid crystalline phases formed with order less than three dimensional(like crystals) and mobility less than that of an isotropic liquid. Parallel orientation of the longitudinal molecular axes is common to all mesophases (long-range orientational order)

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 vapor lamps used in street lights. Their whites are "extremely" white (with slight bluish cast.) and make Halogen lamp's whites look very yellowish by comparison.

Micelle: A spherical formation caused by an amphiphilic substance in a solution. The lyophilic end of the molecule tends to orient itself toward the outside of the sphere while the lyophobic end tends to orient itself toward the inside of the sphere.

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.

Module: An LCD glass connected to a PCB with drivers on board. It may also have controllers, temperature compensation circuits, or other features.

Molar mass: M, is the mass divided by the amount of the substance. Molar mass is usually expressed in g/mol or kg/mol units. The g/mol unit is recommended in polymer science.

Molecular weight: The ratio of the average mass per formula unit of a substance to 1/12 of the mass of an atom of nuclide 12C.

Molecular weight distribution: Represents the distribution of number of polymer chains with a given length and molecular weight M.

Monochromatic light: Light composed of only one specific wavelength.

Monolayer: A layer of amphiphilic molecules on the surface of a solvent, arranged such that the ends attracted to the solvent are in contact with it and the other ends point into the air.

Monomer: The simple chemical unit which, when many are joined together, form a polymer.

Monotropic: A type of material which exhibits the liquid crystalline state only when the temperature changes in one direction. This is generally a result of the liquid crystal phase being below the melting temperature of the solid, where the liquid crystal phase is only observed if the liquid is supercooled below the melting point. See also enantiotropic liquid crystal.

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Native Resolution: Native Resolution refers to the number of physical pixels in a display device. For example, an SVGA projector has 800 physical pixels of resolution horizontally and 600 pixels vertically or 480,000 total pixels. This is the native resolution of the projector. Projectors are capable of projecting greater or smaller resolution images into the same physical resolution through scaling. Scaling reduces the resolution of larger images and increases the resolution of smaller images to match the native resolution of the display device. This type of digital scaling always produces some artifacts in the image that are more apparent when viewing text than graphics or video. Maximum Resolution, as mentioned in the projector specs at ProjectorCentral, refers to the largest resolution that the projector can scale to fit the Native Resolution.

Nematic mesophase: Liquid crystals are characterized by long-range orientational order and the random disposition of the centers of gravity in individual molecules. Nematics may be characterized as the simplest spontaneously anisotropic liquids. Nematic phases are composed of rod-shaped molecular aggregates that are arranged with parallel but not lateral order.

Number-average molecular weight: The number of molecules of length i, multiplied by the molecular weight of an ith unit divided by the total number of molecules present. See also weight average

Nit: A measure of luminance equal to 1 candela per square meter. Higher numbers indicate brighter displays.

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

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OHP: The common abbreviation for Overhead Projector.

Optical activity: The plane of vibration of linearly polarized light rotates as it propagates through a medium. This rotation can occur in either a right or left handed direction. Since linearly polarized light can be regarded as the sum of right and left hand circularly polarized components, this optical activity corresponds to different indices of refraction for the two circular components (circular birefringence).

Optic axis: In a uniaxial material, a single direction of propagation along which double refraction does not occur. The index of refraction for both polarization directions is no along this axis. This axis lies along the director for nematic liquid crystal.

Order parameter: S describes the orientational order of liquid crystalline material, allowing for the individual orientational deviation of the molecules from the director, which represents the average over the collection. Typically, S ranges from 0.3 to 0.9, depending on the temperature, with a value of unity for perfect order.

Ordinary ray: See birefringence

Orientational order: Measure of the tendency of the molecules to align along the director on a long-range basis. See order parameter.

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 tranparencies onto a screen. LCD projection panels are designed to be used with transmissive OHPs and work best with OHPs that produce at least 3,000 lumens. Since 5% to 10% of the light that shines through an LCD panel gets onto the screen, a 3000 lumen OHP will produce an image of 150 to 300 lumens. Transmissive OHPs are fairly bulky (bigger than many projectors). Reflective OHPs are fairly portable but are not useful with LCD projection panels.

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PAL: A European and international broadcast standard for video and 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 transmissive overhead projector (OHP). (See the definition of Overhead Projector for lumen performance.) Because of its small size, low cost, and versatility, panels have been a popular solution for education applications where an OHP is frequently available in the classroom for other instructional purposes. A few products have been built that integrated the panel and the OHP. These were some of the earliest projectors.

PanelLink: An all digital interface used to transmit computer video from a PC/Notebook to a projector. Supports resolutions from 640x480(VGA) up to 1600x1200(UXGA). This digital interface might someday replace the analog VGA interface typically used to connect projectors to computers.

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 terrible color dynamics and contrast (typically 15:1). They are also incredibly slow: On passive laptop computers, the cursor (or anything else) moving on the screen, goes invisible until you stop moving it (submarining) Only one or two projectors use any type of passive matrix display.

Perturbations: Disturbances from an equilibrium condition.

Plastics: A large group of polymers that has properties between elastomers and fibers. As such, plastics have a wide range of properties such as flexibility and hardness and can be synthesized to have almost any combination of desired properties.

Plasticizer: Material added to a polymer to improve its processability and/or flexibility. These are low molecular weight substances which, when mixed with a polymer, lower its glass transition temperature, Tg.

Pitch: The distance it takes for the director of a cholesteric liquid crystal to go through one complete rotation of 360 degrees.

Pitch (pixel): The center-to-center distance between subpixels of the same color.

Pixel: Picture element (see Dot/Pixel).

Polarizability: Relates the induced electric dipole moment, p, of an atom or molecule to the local electric field it experiences as a = p / Elocal, hence depending on the displacement by the field of the electronic charge from its equilibrium position in the atom or molecule.

Polarizer (linear): A device, which in the transmission of electro-magnetic radiation, confines the vibration of the electric and magnetic field vectors to one plane.

Polydisperse polymer system: A polydisperse polymer system is one in which there is a distribution of molecular weights present. A monodisperse system would have only one molecular weight present.

Polydispersity: The ratio of weight average molecular weight to number average molecular weight.

Polymers: Long chains of covalently bonded atoms.

Polymer liquid crystals: Polymers that contain mesogen units and thus have liquid crystal properties.

Polymerization: The act of joining simple molecules(monomers)into giant ones (polymers) to form plastics, fibers, elastomers and non-structural resins.

Polymorphism: The ability to exist in more than one crystal structure.

Poly-Si (silicon) LCD: A popular LCD technology for the top of the line LCD projectors. Monochrome Poly-Si LCDs are typically placed in each of the three color light paths inside a projector, one each for Red, Green, and Blue. This results in increased color saturation, with contrast ratios above 200:1. Poly-Si technology is also a bit faster than the Active Matrix TFT, for smooth video and multimedia.

Positional order: The extent to which the position of an average molecule or group of molecules shows translational symmetry.

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

Progressive Scan: A type of display in which all the horizontal lines of an image are displayed at one time in a single frame, unlike an interlaced scan in which a frame consists of two separate fields with the first field consisting of odd horizontal lines and the second field even horizontal lines. Progressive scan is used by projectors, computer monitors, some TVs and HDTV systems, and some digital camcorders.

Projector: A projector is a device that integrates a light source, optics system, electronics and display(s) for the purpose of projecting an image from a computer or video device onto a wall or screen for large image viewing. There are
hundreds of products available in the market and they are differentiated by their resolution, performance and features. These devices attached to a computer or video device as you would connect a monitor.

Propagation reaction: The middle step in chain polymerization where successive monomers are attached to the growing chain.

Prolate: Elongated at the poles.

Propagation (in polymer growth): The irreversible repetitive addition of monomers to the growing chain.

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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.

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Racemic mixture: See enantiomers

Rear Screen Projection: Using an opaque screen, the projector is placed behind the screen, invisible to the audience. It projects onto the screen and the audience sees it on the other side. Good rear projection screens actually produce brighter images than some standard screens. So as not to waste space behind the screen, ideally a projector with a short throw lens is used. Since the projector can be placed even with the middle of the screen, without blocking anyone's view, keystoning is not a problem. Some mid-room projectors like the Epson have available 3rd party short throw lenses. Since the image is projected through the screen, the image must be reversed.

Recrystallization: Reorganization proceeding through partial melting. Recrystallization is likely to result in an increase in the degree of crystallinity, or crystal perfection or both.

Relaxation: A term used to mean all irreversible processes which bring a system back to equilibrium after it has been perturbed by some external force. For instance, if an electric field is applied to a fluid of polar materials a polarization will be induced, but this will disappear after the field is removed, because of the randomization of the molecular orientations produced by Brownian motions.

Reorganization: The molecular process by which (i) amorphous or poorly ordered regions of a polymer specimen become incorporated into crystals, or (ii) a change to a more stable crystal structure takes place, or (iii) defects within the crystals decrease.

Resonance: A method of stabilizing a bond by delocalizing the electrons around the molecule.

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.

Rotatory power: Measure of the capability of a twisted liquid crystal layer to rotate the angle of incident polarized light.

Rotational symmetry: Consider the example of an unmarked billiard ball. Rotation of any amount about any axis through its center will take the ball into itself so it has complete rotational symmetry. However, the stitching on a baseball places several restrictions on the axes about which it can be rotated into itself.

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Saturation Voltage: RMS voltage required to turn fluid to 90% ON.

Scaling: An operation performed by a digital signal processor to fill the screen with an image not being displayed in the native resolution of the LCD panel.

Schlieren texture: The texture that appears in the optical microscopy of nematic and related smectic C phases under crossed polarizers when the planarity of the phase is interrupted by defects. The schlieren, dark streaks or brushes, form in the liquid crystal, connecting the defect points. The dark streaks or brushes that are characteristic of this texture may also appear along disclinations in a liquid crystal.

SDTV: SDTV stands for standard definition television and is a class of digital television (DTV) that refers to the 480i format. 480i is an interlaced video format that produces a full frame of 480 lines of video in two successive fields. The first field includes the odd lines and the second field includes the even lines.

SECAM: A French and international broadcast standard for video and broadcasting. Higher resolution than NTSC.

Self-assembly: The aggregation of molecular moieties into more ordered structures that are thermodynamically stable and involve noncovalent bonds. Crystallization is an example of such self-assembly. Self-assembly is used to build
nanostructures such as inorganic clusters and lattices, nanotubes and channels, host-guest complexes, monolayers, hydrogen-bonded networks and systems of intertwined molecules.

Short Throw Lens: A lens designed to project the largest possible image from short distance. Most front room projectors use short throw lens. They are often required for rear projection, where the depth behind the screen is limited. A typical short throw lens might produce a diagonal image size of 10 FT, from a distance of 7 to 10 FT.

Side chain polymer liquid crystal: A polymer liquid crystal in which the mesogens are attached to the side of the main chain and not a part of the main chain itself.

Smectic mesophase: The molecules organize themselves into layers. The smectic phases form a one dimensional periodic lattice in which the individual layers are two dimensional liquids. Now 12 different smectic phases have been identified.

Spacer: Flexible section of polymer chain between two mesogens or the mesogen and the backbone of a polymer.

sRGB: sRGB stands for screen Red Green Blue and is a proposed standard for rendering color evenly across a variety of platforms. One objective is to replace the Web-safe palette of 216 colors with sRGB.

Stability: A measure of the reactivity of a given molecule.

Star-branching: A type of polymerization in which a branched polymer is formed as branches emanating from a single point.

Stereoisomers: Isomers that differ only in the way their atoms are oriented.

Steric hindrance: A condition when the rotation of a given group is restricted due to the size of neighboring groups.

Stereoregular polymer: A regular polymer, the molecules of which can be described in terms of only one species of stereorepeating unit in a single sequential arrangement.

Isotactic polymer: A regular polymer, the molecules of which can be described in terms of only one species of configuration base unit (having chiral or prochiral atoms in the main chain) in a single sequential arrangement. In an isotactic polymer, the configurational repeating unit is identical with the configurational base unit.

S-Video: 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(color, C). S-Video is also
referred to as Y/C. A composite signal, typically found coming out of an RCA jack on the back of most 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 composite signal into the luminance and chrominance signals. A comb-filter can reduce the sharpness of your video image.

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.

Syndiotactic polymer: A regular polymer, the molecules of which can be described in terms of alternation of configurational base units that are enantiomeric. In the syndiotactic polymer, the configurational repeating units consist of two configurational base units that are enantiomeric.

Atactic polymer: A regular polymer, the molecules of which have equal numbers of the possible configurational base units in a random sequence distribution.

Stereorepeating unit: A configurational repeating unit having defined configuration at all sites of stereoisomerism in the main chain of a polymer molecules.

Enantiomeric: The configurational unit that corresponds to the same
constitutional units if they are non-superposable mirror images.

Diastereoisomeric: Two non-superposable configurational units that correspond to the same constitutional unit (if they are not mirror images).

Stereoselectivity: The chemical selectivity to polymerize only one stereoisomer (enantioselectivity and diastereoselectivity)

Stereospecific polymerization: Polymerization in which a polymer of a specific tacticity is formed. A polymerization in which stereoisomerism present in the monomer is merely retained in the polymer is not to be regarded as stereospecific.

Step-growth polymerization: Often termed condensation, it is defined as a polymerization in which all molecular species in the system can react with each other ,and the growth of polymer chains proceeds by condensation reactions between molecules of all degrees of polymerization.

Subpixel: A red, blue, or green liquid crystal shutter. One subpixel of each color forms a pixel capable of displaying as many as 16.7 million colors.

SuperClearMVA (Multi-Domain Vertical Alignment): Combines SuperClear screen technology digital with a liquid crystal technology in which each subpixel is subdivided into four regions in which the liquid crystal molecules align at angles to each other. The advantages of MVA are wider viewing angles and faster video response than TN or IPS.

Super critical fluids: A substance above its critical point on the temperature/pressure phase diagram. Above the critical point, the fluid is neither a gas nor a liquid but possesses properties of both. The viscosity of a supercritical fluid is at least one order of magnitude higher than the viscosity in the gaseous state, but is one or two orders of magnitude less than in the liquid state.

Super Twisted Nematic (STN): A type of liquid crystal in which the alignment surface, and therefore the liquid crystal molecules, is oriented more than 90 degrees from each surface of glass.

Surfactants: Surface active agents. Organic compounds consisting of two parts: a water-attracting (hydrophilic) portion and a water-resistant (hydrophobic) portion. Detergents may contain more than one kind of surfactant. The hydrophobic ends attach themselves to the soil particles or to the fabrics being washed while the hydrophilic ends are attracted to the water. The surfactant molecules surround the soil particles, break them up, force them away from the surface of the fabric, then suspend the soil particles in the wash water. Surfactants are classified by their ionic (electrical charge) properties in water.

Symmetry: The invariance of some properties of the object being investigated with respect to all the transformations considered.

Syndiotactic polymer: See stereoregular polymer.

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Tacticity: The orderliness of the succession of configurational repeating units in the main chain of a polymer molecule. (See stereoregular polymer)

Tensile strength: A measure of the ability of a polymer to withstand pulling stresses.

Termination reaction: The final step in chain polymerization where the growth of a polymer is stopped.

Terpolymerization: Polymerization involving three types of monomers.

TFT: Thin Film Transistor

Thermoplastics: Linear plastics of finite molecular weight that can be fabricated into complex shapes by melting and injection molding.

Thermosets: A type of plastic that must be cured, forming network-like structures that do not soften at high temperatures.

Thermotropic: Liquid crystal molecules which exhibit temperature dependent liquid crystalline behavior. See also: lyotropic

Threading: When a nemaparallelepipedtic liquid crystalline material shows a tangled, thread-like appearance when observed between crossed polaroids in the optical microscope.

Threshold Voltage: RMS voltage required to turn fluid to 10% ON.

Topology: A branch of mathematics concerned with those properties of geometric configurations which remain unaltered under very general kinds of elastic deformations (transformations such as stretching or twisting) where length, angles, and shapes are changed.

Torsion: The rotation about a single bond which joins two atoms.

Translational order: A condition when molecules have some arrangement in space. Crystals have three degrees of translational order (each molecule is fixed in space with an x, y, and z coordinate) and liquids have no translational order.

Transmissive: An LCD which does not have a reflector or transflector laminated to the rear polarizer. A backlight must be used with this type of LCD configuration.

Twisted Nematic (TN): A type of liquid crystal in which the alignment surface, and therefore the liquid crystal molecules, is oriented 90 degrees from each surface of glass.

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Uniaxial materials: Possess only one direction along which monochromatic light vibrating in any plane will travel with the same velocity. This direction is know as the optic axis.

Unit cell: The smallest, regularly repeating material portion contained in a parallelepiped from which a crystal is formed by parallel displacements in three dimensions. Unlike the case of low-molar mass substances, the unit cell of polymer crystals usually comprises only parts of the polymer molecules, and the regularity of the periodic repetition may be imperfect.

UXGA: UXGA 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 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

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Van der Waal's forces: Forces which act between molecules that are caused by small random fluctuations in the polarity of the molecules.

VGA: VGA 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 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.

Video Response (response time): The time it takes to turn a pixel from OFF to ON to OFF again. A low number is desirable to display moving images without ghosting.

Viewing Angle: A cone perpendicular to the LCD in which the contrast ratio exceeds 10.

Viewing Area: The actual area that can be illuminated when the entire screen is turned ON (white).

Viscosity: The internal resistance to flow existing between two liquid layers when they are moved relative to each other. This internal resistance is a result of interaction between liquid molecules in motion.

Vulcanization: A process by which a network of crosslinks is introduced into an elastomer to strengthen it.

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Weight average molecular weight: In the distribution of molecular weights represented in a polymer sample, the weight average is determined by summing the product of the number of molecules of length i and the square of the molecular weight of a molecule of length i and then dividing by the total weight. See also number average

Wi-Fi: Wi-Fi is Wireless Fidelity and is based on the IEEE 802.11 specifications for wireless local area networks (WLAN) developed by a working group of the Institute of Electrical and Electronics Engineers (IEEE). There are four specifications in the family: 802.11, 802.11a, 802.11b, and 802.11g. All four use the Ethernet protocol and CSMA/CA (carrier sense multiple access with collision avoidance) for path sharing.

Wi-Fi (802.11a): An IEEE specification for wireless networking that operates in the 5 GHz frequency range (5.725 GHz to 5.850 GHz) with a maximum 54 Mbps data transfer rate. The 5 GHz frequency band is not as crowded as the 2.4 GHz frequency, because the 802.11a specification offers more radio channels than the 802.11b. These additional channels can help avoid radio and microwave interference.

Wi-Fi (802.11b): International standard for wireless networking that operates in the 2.4 GHz frequency range (2.4 GHz to 2.4835 GHz) and provides a throughput of up to 11 Mbps. This is a very commonly used frequency. Microwave ovens, cordless phones, medical and scientific equipment, as well as Bluetooth devices, all work within the 2.4 GHz frequency band.

WSXGA: WSXGA defines a class of SXGA displays with a width resolution sufficient to create an aspect ratio of 16:9. Resolution is defined by the number of individual dots that a display uses to create an image. These dots are called pixels. A WSXGA display has 1920 to 1600 horizontal pixels and 1080 to 900 vertical pixels respectively that are used to compose the image delivered by the projector.

WXGA: WXGA defines a class of XGA displays with a width resolution sufficient to create an aspect ratio of 16:9. Resolution is defined by the number of individual dots that a display uses to create an image. These dots are called pixels. A WXGA display has 1366 to 1280 horizontal pixels and 768 to 720 vertical pixels respectively that are used to compose the image delivered by the projector.

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XGA: XGA 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 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.

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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: Is 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. Conversely, a 10 foot diagonal image at 15 feet with no zoom would still be a 10 image at 21 feet at maximum zoom (15 x 1.4 = 21 feet). A zoom lens is "not as bright" as a fixed lens, and the higher the ratio, the less light output.

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