wave and particle behaviors of lcd displays pricelist

The quantification of wave-particle duality (WPD) by means of measurable features associated to it, such as fringe visibility ($\mathcal {V}$) and path distinguishability ($\mathcal {D}$), led to the establishment of the constraint $\mathcal {V}^{2}+\mathcal {D}^{2} \leq \,1$. The two involved quantities refer to so-called "quantons", physical objects that are capable of generating an interferometric pattern, while being at least partially localizable. Any quanton"s internal degree of freedom (DOF) can in principle be used as a path-marker. When the quanton and its internal DOF are simultaneously engaged, new constraints can be derived and experimentally tested. Generalized constraints show how $\mathcal {V}$ and $\mathcal {D}$ relate to other quantifiers and bring to light coherences that might remain otherwise hidden in both quantum and classical light. We submitted two-qubit constraints to experimental tests, using optical light beams. This shows that, despite the rather contrived nature of the constraints, linear optics setups are appropriate to test them. Our experimental results are in very good agreement with theoretical predictions related to the tested constraints. Our results also show that quantifiers such as $\mathcal {V}$ and $\mathcal {D}$ help not only to quantify, but also to generalize the concept of WPD.

The concept behind how light travels and behaves has been one of physics’ greatest mysteries. In the world we experience every day, we see that objects, like a chair or a rock, can only be in one place at one time. We can say that these objects behave like a particle, which is a tiny object that is characterized by only being in one place at a time. On the other hand, we have things that can be at different places at the same time, such as waves. Have you noticed what happens when you throw a rock in the water? It makes waves that spread in a ring and grow as they move outward. In physics, waves are described as the spread of the disturbance or perturbation of something, often energy. When you throw a rock in the water, you are transferring some energy of the movement of the rock into the water, which causes the water to move around to disperse that energy.

We can see how a rock behaves differently from a wave. But scientists could not agree if light behaves like a particle or a wave In 1801, Thomas Young, a British scientist, was convinced that light was a wave, and he designed his famous double-slit experiment. In this experiment, Young would shine a light source onto a screen that had two small slits close to one another to see the reflection of the light after passing through the slits in the wall behind it. What he saw was what physicists now call an interference pattern. Let’s go back to the ripples in the water. If we throw a rock in the water, we see that it creates waves that have crests and troughs. If we throw a rock next to it, we will see that it also creates crests and troughs. As the waves spread, we will see that the waves that originated from one rock will start to cross the path of the waves created by the other rock. When the crests of waves created by rock A cross the troughs of waves created by rock B, they will cancel each other out. When the crest of waves created by rock A crosses the crest of waves created by rock B, then they form a taller crest. Then you can imagine what happens when the paths of two troughs cross each other: they forma deeper trough. See image below.

If instead of thinking of water waves now we think about light, then what we expect to see on the wall will be lines of bright light and lines with no light. That is exactly what Young’s double-slit experiment showed. Confirming the hypothesis that light behaves as a wave. So then, that’s it, right? Light is a wave! Yes, but…

In order to be sure, other scientists decided to explore the subject a bit further. In 1909, Geofrey Taylor repeated Young’s experiment and took photos of the light coming out of the slits. Initially he saw the same interference patter as Young. But when he dimmed the light to very low level, the photos were of little points, like particles hitting the screen. If he left exposure of the photo for long enough, the little points started forming the interference pattern. Therefore, he demonstrated that light can behave both as particle and wave. Many other scientists throughout history have tested this concept with electrons, molecules, and atoms always seeing the same result. Now it is time for you to check it out!

Thin copper filament/strand. Many wires are made with copper strands. Cut a piece of a cable that you don’t mind discarding. Remove the rubber and separate the intertwined pieces of copper. Get a single strand, depending on your laser pointer 3 inches will suffice.

Note: You can find other DIY setups that use old DVD discs, aluminum foil, or even cardboard paper. We have found this the easiest and most reliable form of doing it.

In the student’s guide, students are tasked with developing an experiment, following Young’s experiment, to see if they can determine whether light behaves as a particle or a wave. The idea of this experiment is that students start to form a model of the light’s behavior as a particle and as a wave.

Before setting up any of the experiments, ask the students what they are expecting to see when light goes through an obstacle such as the double slit, what a particle behavior should look like, what a wave behavior should look like, and finally, what light would look like. Ask them to draw their models. To give them a starting point, provide the specific examples, i.e., what it would look like when you let sand pass through the double slits vs water, then ask what they expect to happen when they flash a laser.

In this experiment, students will be asked to explain the model of light. Before the experiment starts, ask students to predict what they expect to see when they shine a laser onto a screen without an obstacle and then with the double slit. Ask them to sketch their predictions and provide an explanation.

Once predictions are complete, let students carefully shine the laser onto a wall or a screen. Ask them to write down their observations and how what they saw compares to models of particles (thinking about sand grains as particles) and waves without obstacles.

Next, ask students to build their double slit diffraction set up. Take the piece of copper filament/strand and place it across the laser pointer, where the beam comes out.

Use electrical tape to secure the copper strand to the laser pointer on the top and bottom. Then add extra tape to the side to make a smaller aperture for the beam to go through. See pictures below.

Now ask students to write their predictions of what they expect to see now with the laser light going through the double slit, and how it will be similar to the particle or wave models. Ask them to sketch in their notebooks the patterns that they predict will appear.

Once students have submitted their predictions, they can shine the laser light onto the screen or wall. You should see a horizontal pattern of dark and bright lines or dots that represent the crests and troughs of the interference of the light as it passess through the doble slits. Patterns are easier to see if the lights are off and the wall or screen is flat with no edges that interfere with the light as it passes through the double slit.

Figure X and Y are two examples of what you should see on the screens/wall. These patterns were created with the laser pointer set up shown above. Picture Z shows a double slit pattern from a physics lab. Ask students to draw what they see and compare to their predictions and also to what they expect particles or waves will be like. Then ask how their observations explain the need for a theory of wave-particle duality of light.

Just what is the true nature of light? Is it a wave or perhaps a flow of extremely small particles? These questions have long puzzled scientists. Let"s travel through history as we study the matter.

Around 1700, Newton concluded that light was a group of particles (corpuscular theory). Around the same time, there were other scholars who thought that light might instead be a wave (wave theory). Light travels in a straight line, and therefore it was only natural for Newton to think of it as extremely small particles that are emitted by a light source and reflected by objects. The corpuscular theory, however, cannot explain wave-like light phenomena such as diffraction and interference. On the other hand, the wave theory cannot clarify why photons fly out of metal that is exposed to light (the phenomenon is called the photoelectric effect, which was discovered at the end of the 19th century). In this manner, the great physicists have continued to debate and demonstrate the true nature of light over the centuries.

Known for his Law of Universal Gravitation, English physicist Sir Isaac Newton (1643 to 1727) realized that light had frequency-like properties when he used a prism to split sunlight into its component colors. Nevertheless, he thought that light was a particle because the periphery of the shadows it created was extremely sharp and clear.

The wave theory, which maintains that light is a wave, was proposed around the same time as Newton"s theory. In 1665, Italian physicist Francesco Maria Grimaldi (1618 to 1663) discovered the phenomenon of light diffraction and pointed out that it resembles the behavior of waves. Then, in 1678, Dutch physicist Christian Huygens (1629 to 1695) established the wave theory of light and announced the Huygens" principle.

Some 100 years after the time of Newton, French physicist Augustin-Jean Fresnel (1788 to 1827) asserted that light waves have an extremely short wavelength and mathematically proved light interference. In 1815, he devised physical laws for light reflection and refraction, as well. He also hypothesized that space is filled with a medium known as ether because waves need something that can transmit them. In 1817, English physicist Thomas Young (1773 to 1829) calculated light"s wavelength from an interference pattern, thereby not only figuring out that the wavelength is 1 μm ( 1 μm = one millionth of a meter ) or less, but also having a handle on the truth that light is a transverse wave. At that point, the particle theory of light fell out of favor and was replaced by the wave theory.

The next theory was provided by the brilliant Scottish physicist James Clerk Maxwell (1831 to 1879). In 1864, he predicted the existence of electromagnetic waves, the existence of which had not been confirmed before that time, and out of his prediction came the concept of light being a wave, or more specifically, a type of electromagnetic wave. Until that time, the magnetic field produced by magnets and electric currents and the electric field generated between two parallel metal plates connected to a charged capacitor were considered to be unrelated to one another. Maxwell changed this thinking when, in 1861, he presented Maxwell"s equations: four equations for electromagnetic theory that shows magnetic fields and electric fields are inextricably linked. This led to the introduction of the concept of electromagnetic waves other than visible light into light research, which had previously focused only on visible light.

The term electromagnetic wave tends to bring to mind the waves emitted from cellular telephones, but electromagnetic waves are actually waves produced by electricity and magnetism. Electromagnetic waves always occur wherever electricity is flowing or radio waves are flying about. Maxwell"s equations, which clearly revealed the existence of such electromagnetic waves, were announced in 1861, becoming the most fundamental law of electromagnetics. These equations are not easy to understand, but let"s take an in-depth look because they concern the true nature of light.

Maxwell"s four equations have become the most fundamental law in electromagnetics. The first equation formulates Faraday"s Law of Electromagnetic Induction, which states that changing magnetic fields generate electrical fields, producing electrical current.

The second equation is called the Ampere-Maxwell Law. It adds to Ampere"s Law, which states an electric current flowing over a wire produces a magnetic field around itself, and another law that says a changing magnetic field also gives rise to a property similar to an electric current (a displacement current), and this too creates a magnetic field around itself. The term displacement current actually is a crucial point.

The fourth equation is Gauss"s Law of magnetic field, stating a magnetic field has no source (magnetic monopole) equivalent to that of an electric charge.

If you take two parallel metal plates (electrodes) and connect one to the positive pole and the other to the negative pole of a battery, you will create a capacitor. Direct-current (DC) electricity will simply collect between the two metal plates, and no current will flow between them. However, if you connect alternating current (AC) that changes drastically, electric current will start to flow along the two electrodes. Electric current is a flow of electrons, but between these two electrodes there is nothing but space, and thus electrons do not flow.

Maxell wondered what this could mean. Then it came to him that applying an AC voltage to the electrodes generates a changing electric field in the space between them, and this changing electric field acts as a changing electric current. This electric current is what we mean when we use the term displacement current.

A most unexpected conclusion can be drawn from the idea of a displacement current. In short, electromagnetic waves can exist. This also led to the discovery that in space there are not only objects that we can see with our eyes, but also intangible fields that we cannot see. The existence of fields was revealed for the first time. Solving Maxwell"s equations reveals the wave equation, and the solution for that equation results in a wave system in which electric fields and magnetic fields give rise to each other while traveling through space.

The form of electromagnetic waves was expressed in a mathematical formula. Magnetic fields and electric fields are inextricably linked, and there is also an entity called an electromagnetic field that is solely responsible for bringing them into existence.

Now let"s take a look at a capacitor. Applying AC voltage between two metal electrodes produces a changing electric field in space, and this electric field in turn creates a displacement current, causing an electric current to flow between the electrodes. At the same time, the displacement current produces a changing magnetic field around itself according to the second of Maxwell"s equations (Ampere-Maxwell Law).

The resulting magnetic field creates an electric field around itself according to the first of Maxwell"s equations (Faraday"s Law of Electromagnetic Induction). Based on the fact that a changing electric field creates a magnetic field in this manner, electromagnetic waves-in which an electric field and magnetic field alternately appear-are created in the space between the two electrodes and travel into their surroundings. Antennas that emit electromagnetic waves are created by harnessing this principle.

Maxwell calculated the speed of travel for the waves, i.e. electromagnetic waves, revealed by his mathematical formulas. He said speed was simply one over the square root of the electric permittivity in vacuum times the magnetic permeability in vacuum. When he assigned "9 x 109/4π for the electric permittivity in vacuum" and "4π x 10-7 for the magnetic permeability in vacuum," both of which were known values at the time, his calculation yielded 2.998 x 108 m/sec. This exactly matched the previously discovered speed of light. This led Maxwell to confidently state that light is a type of electromagnetic wave.

The theory of light being a particle completely vanished until the end of the 19th century when Albert Einstein revived it. Now that the dual nature of light as "both a particle and a wave" has been proved, its essential theory was further evolved from electromagnetics into quantum mechanics. Einstein believed light is a particle (photon) and the flow of photons is a wave. The main point of Einstein"s light quantum theory is that light"s energy is related to its oscillation frequency. He maintained that photons have energy equal to "Planck"s constant times oscillation frequency," and this photon energy is the height of the oscillation frequency while the intensity of light is the quantity of photons. The various properties of light, which is a type of electromagnetic wave, are due to the behavior of extremely small particles called photons that are invisible to the naked eye.

The German physicist Albert Einstein (1879 to 1955), famous for his theories of relativity, conducted research on the photoelectric effect, in which electrons fly out of a metal surface exposed to light. The strange thing about the photoelectric effect is the energy of the electrons (photoelectrons) that fly out of the metal does not change whether the light is weak or strong. (If light were a wave, strong light should cause photoelectrons to fly out with great power.) Another puzzling matter is how photoelectrons multiply when strong light is applied. Einstein explained the photoelectric effect by saying that "light itself is a particle," and for this he received the Nobel Prize in Physics.

The light particle conceived by Einstein is called a photon. The main point of his light quantum theory is the idea that light"s energy is related to its oscillation frequency (known as frequency in the case of radio waves). Oscillation frequency is equal to the speed of light divided by its wavelength. Photons have energy equal to their oscillation frequency times Planck"s constant. Einstein speculated that when electrons within matter collide with photons, the former takes the latter"s energy and flies out, and that the higher the oscillation frequency of the photons that strike, the greater the electron energy that will come flying out.

In short, he was saying that light is a flow of photons, the energy of these photons is the height of their oscillation frequency, and the intensity of the light is the quantity of its photons.

Einstein proved his theory by proving that the Planck"s constant he derived based on his experiments on the photoelectric effect exactly matched the constant 6.6260755 x 10-34 (Planck"s constant) that German physicist Max Planck (1858 to 1947) obtained in 1900 through his research on electromagnetic waves. This too pointed to an intimate relationship between the properties and oscillation frequency of light as a wave and the properties and momentum (energy) of light as a particle, or in other words, the dual nature of light as both a particle and a wave.

French theoretical physicist Louis de Broglie (1892 to 1987) furthered such research on the wave nature of particles by proving that there are particles (electrons, protons and neutrons) besides photons that have the properties of a wave. According to de Broglie, all particles traveling at speeds near that of light adopt the properties and wavelength of a wave in addition to the properties and momentum of a particle. He also derived the relationship "wavelength x momentum = Planck"s constant."

From another perspective, one could say that the essence of the dual nature of light as both a particle and a wave could already be found in Planck"s constant. The evolution of this idea is contributing to diverse scientific and technological advances, including the development of electron microscopes.

This section contains lecture notes in both PDF and PowerPoint formats. Some of the slides include animations, which can be seen by viewing the PowerPoint file as a slide show.

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Photo: A trick of the polarized light: rotate one pair of polarizing sunglasses past another and you can block out virtually all the light that normally passes through.

Photo: A less well known trick of polarized light: it makes crystals gleam with amazing spectral colors due to a phenomenon called pleochroism. Photo of protein and virus crystals, many of which were grown in space. Credit: Dr. Alex McPherson, University of California, Irvine. Photo courtesy of NASA Marshall Space Flight Center (NASA-MSFC).

Photo: Prove to yourself that an LCD display uses polarized light. Simply put on a pair of polarizing sunglasses and rotate your head (or the display). You"ll see the display at its brightest at one angle and at its darkest at exactly 90 degrees to that angle.

Photo: How liquid crystals switch light on and off. In one orientation, polarized light cannot pass through the crystals so they appear dark (left side photo). In a different orientation, polarized light passes through okay so the crystals appear bright (right side photo). We can make the crystals change orientation—and switch their pixels on and off—simply by applying an electric field. Photo from liquid crystal research by David Weitz courtesy of NASA Marshall Space Flight Center (NASA-MSFC).

Liquid crystal displays (LCDs) consist of liquid crystals that are activated by electric current. They are used most frequently to display one or more lines of alpha-numeric information in a variety of devices: fax machines, laptop computer screens, answering machine call counters, scientific instruments, portable —active matrix displays—are even being used as screens for handheld color TVs. Eventually, they may be widely used for large screen, high-definition TVs.

The basis of LCD technology is the liquid crystal, a substance made of complicated molecules. Like water, liquid crystals are solid at low temperatures. Also like water, they melt as you heat them. But when ice melts, it changes into a clear, easily flowing liquid. Liquid crystals, however, change into a cloudy liquid very different from liquids like water, alcohol, or cooking oil. At slightly higher temperatures, the cloudiness disappears, and they look much like any other liquid.

When the liquid crystal is a solid, its molecules are lined up parallel to one another. In the intermediate cloudy phase (liquid), the molecules still retain this more or less parallel orientation. As in any liquid, the molecules are free to move around, but they tend to "line up" in one direction, reflecting light and causing a cloudy appearance. Higher temperatures tend to agitate the molecules and thus make the liquid clear.

In an LCD, an electric current is used to switch segments of liquid crystals from a transparent phase to a cloudy phase, each segment forming part of a number or letter. The segments can also be in the shape of tiny dots or pixels, and the can be arranged in rows and columns. They are turned on and off individually to either block or allow polarized light to pass through. When the light is blocked, a dark spot is created on the reflecting screen.

There are two general types of LCDs: passive matrix, and the newer active matrix (AMLCDs). Brighter and easier to read, active matrix displays use transistors behind each pixel to boost the image. The manufacturing process for AMLCDs, however, is much trickier than that for passive matrix LCDs. As many as 50 percent of those made must now be thrown out because of imperfections. One imperfection is enough to ruin an AMLCD. This makes them very expensive to manufacture.

A working LCD consists of several components: display glass, drive electronics, control electronics, mechanical package, and power supply. The display glass —between which the liquid crystals lie—is coated with row and column electrodes and has contact pads to connect drive electronics (electric current) to each row and column electrode. The drive electronics are integrated circuits that supply current to "drive" the row and column electrodes. The control electronics are also integrated circuits. They decode and interpret the incoming signals—from a laptop computer, for example—and send them to the drive electronics. The mechanical package is the frame that mounts the printed circuit boards for the drive and control electronics to the display glass. This package

also strengthens and protects the display glass and anchors the entire display to the device using the LCD, whether it is a laptop computer, a fax machine, or another device. Finally, the power supply is an electronic circuit that supplies current to the LCD. Equipment makers who use LCDs often purchase the power supplies separately.

In all LCDs, the liquid crystal is sandwiched between two pieces of glass or transparent plastic called substrates. Just any glass will not do. If the glass has many sodium or other alkali ions, they can move to the glass surface, combine with any moisture that is there, and alter the electric field pattern and liquid crystal alignment. To eliminate that, LCD makers either use borosilicate glass, which has few ions, or they apply a layer of silicon dioxide to the glass. The silicon dioxide prevents the ions from touching any moisture. An even simpler solution is to use plastic instead of glass. Using plastic also makes the display lighter. However, inexpensive plastics scatter light more than glass, and they may react chemically with liquid crystal substances.

Most LCDs today also use a source of light coming from the rear of the display (backlight), such as a fluorescent light, to make the liquid crystal appear darker against the screen when in its cloudy phase. LCD makers also use sheets of polarizer material to enhance this effect.

Making passive matrix LCDs is a multi-step process. The surface and rear glass of the display is first polished, washed, and coated with silicon dioxide (SiO2). Next, a layer of indium tin oxide is evaporated onto the glass and etched into the desired pattern. A layer of long chain polymer is then applied to allow the liquid crystals to align properly, followed by a sealing resin. The spacers next are put into place, and the glass sandwich is filled with the liquid crystal material.

Preparing the glass substrates1 First, the two glass substrates must be cut to the proper size, polished, and washed. Cutting can be done with a diamond saw or scribe, while polishing involves a process called lapping, in which the glass is held against a rotating wheel that has abrasive particles embedded in it. After being washed and dried, the substrates are coated with a layer of silicon dioxide.

Making the electrode pattern2 Next, the transparent electrode pattern must be made on the substrates. This is done by completely coating both front and rear glass surfaces with a very thin layer of indium tin oxide. Manufacturers then make a mask of the desired pattern, using either a silk-screening or photolithography process. They apply the finished mask to the fully coated glass, and areas of indium tin oxide that are not needed are etched away chemically.

3 Alternatively, finer definition can be achieved by using glass that has a layer of etching-resistant, light-sensitive material (called photoresist) above the indium tin oxide film. A mask with the desired pattern is placed over the glass, and the glass is bombarded with ultraviolet light. This light causes the resistive layer it shines on to lose its resistance to etching, allowing the chemicals to eat away both the exposed photoresist and the indium tin oxide below it, thus forming the pattern. The unnecessary photoresist that remains can then be removed with other chemicals. A second variety of resistive film resists etching only after it is exposed to ultraviolet light; in this case, a negative mask of the pattern must be used. Regardless of which method is used, the patterns on the two substrates are designed to overlap only in specific places, a design that ensures that the thin strips of indium tin oxide conveying voltage to each element have no electrode positioned directly opposite that might show up while the cell is working.

Applying the polymer4 After the electrode pattern is in place, the substrates must be coated with a polymer. The polymer allows the liquid crystals to align properly with the glass surface. Polyvinyl alcohol, polyamides, and some silanes can be used. Polyamides are the most popular agents, because polyvinyl alcohol is subject to moisture problems, and silanes produce a thin, unreliable coating.

5 After coating the glass, manufacturers then stroke the polymer coat in a single direction with soft material. This can result in small parallel grooves being etched into the polymer, or it may simply stretch the polymer coat. In any case, this process forces the liquid crystals to lie parallel to the direction of the stroke. The crystals may be aligned another way, by evaporating silicon oxide onto the glass surface at an oblique angle. This procedure is used to make most digital watch displays but is not convenient for making large-scale displays. It also does not yield the low-tilt angle possible with the previous method.

6 If LCD makers want to align liquid crystals perpendicular to the glass surface, another technique is used: coating the glass with an amphophilic material. This is material whose molecules display affinity for water at one end of the molecule and repulsion from water at the other end. One end—the affinity end—adheres to the glass surface while the other end—the repulsing end—points into the liquid crystal area, repelling the liquid crystals and forming them into an alignment that is perpendicular to the glass surface.

the liquid crystal7 A sealing resin is next applied to the substrates, followed by plastic spacers that will give the liquid crystal cell the proper thickness. Next, the liquid crystal material is injected into the appropriate area between the two glass substrates. The thickness of the LCD cell is usually restricted to 5-25 micrometers. Because proper thickness is crucial for cell operation and because spacers don"t always achieve uniform thickness, LCD makers sometimes put appropriately sized glass fibers or beads in the liquid crystal material. The beads or fibers cannot be seen by the naked eye. They help hold the cell at the proper thickness while the sealant material is setting.

8 To make LCDs more visible, polarizers are added. These are usually made from stretched polyvinyl alcohol films that have iodine in them and that are sandwiched between cellulose acetate layers. Colored polarizers, made using dye instead of iodine, are also available. Manufacturers glue the polarizer to the glass using an acrylic adhesive and cover it with a plastic protective film. They can make reflective polarizers, which also are used in LCDs, by incorporating a simple metal foil reflector.

Final assembly9 After the polarizer film is attached, the unit is allowed to age. Finally, the finished glass display assembly is mounted to the circuit boards containing the control and drive electronics. Then, the entire package is ready to be mounted to the device using the LCD—laptop computer, fax machine, clock, etc.

The process used to make an active matrix LCD (AMLCD) is quite similar to that used for passive matrix LCDs, although it is more complex and more difficult. Generally, the steps of SiO2 coating, indium tin oxide application, and the photoresist etching are replaced by a host of other steps.

In the case of AMLCDs, each LCD component has to be changed to work properly with the thin film transistor and electronics used to boost and clarify the LCD image. Like their passive matrix brethren, active matrix displays are sandwiches consisting of several layers: a polarizing film; a sodium barrier film (SiO2), a glass substrate incorporating a black matrix, and a second sodium barrier film; a color filter and a color filter overcoat made of acrylic/urethane; a transparent electrode; an orientation film made of polyamide; and the actual liquid crystal material incorporating plastic/glass spacers to maintain proper LCD cell thickness.

conditions in a clean room environment to maximize yield. "Clean rooms" have special air filtering devices designed to keep all dust particles out of the room, and workers inside the room must wear special clothing. Nonetheless, many LCDs have to be discarded because of imperfections. This is particularly true of AMLCDs, which currently have a rejection rate of approximately 50 percent. To minimize the rejection rate, each active device is inspected and as many are repaired as possible. In addition, active matrix assemblies are inspected immediately after the photoresist etching step and again after the liquid crystal material is injected.

The future is clearly with active matrix LCDs, even though the current rejection rate is very high and the manufacturing process is so expensive. Gradual improvements are expected in the manufacturing process of AMLCDs, and in fact companies are already beginning to offer inspection and repair equipment that may cut the current rejection rate from 50 percent down to around 35 percent.

But the real boost to LCD manufacturing technology may come from all the money that companies are pouring into the research and development process on large screen, AMLCD displays for the long-awaited high-definition television technology.

Robinson, Gail M. "Display Systems Leap Forward: New Technologies Offer Designers More Choices Than Ever in CRTs, LCDs, EL and More." Design News. February 13, 1989, p. 52.

LCD panelscan be categorized as flat-panel displays. What makes them distinct from other display technologies is the layer of liquid crystal material within. In this thin layer, liquid crystal molecules are aligned between two glass substrates. On the inner surfaces of each of those substrates lie electrodes that control charge carriers like electrons that then interact with the liquid crystals, creating an electric field that runs through them; this, in turn, can change the alignment of the crystals, also changing the overall behavior of the molecules. On the opposite sides of the substrate, polarizers are used to control the levels of light passage, affecting the overall image of the display.

Unlike CRT monitors, LCD monitors cannot illuminate themselves, and so they require a light source: the backlight. This backlight is most frequently made of the well-known LEDs which stand for light-emitting diodes. Sourced from the backlight, light is moved through the back polarizer and back substrate, into the liquid crystals. Now, the light waves can behave in a variety of ways. Backlight used in LCD displays can be LED (Light Emitting Diode) backlight or CCFL (Cold Cathode Fluorescent Lamp) backlight. LED backlights use less power which becomes more popular, while CCFL is lower cost for large size LCD displays such as large LCD TV. Recently, quantum dots technology is used to increase the LCD contrast.

Electrodes are the controlling factors of the liquid crystal behavior, and thus also the light behavior. By conducting or not conducting a current into the crystal layer, the light may or may not be able to pass through the liquid crystals in a manner that will allow passage through the polarizer. Because of this role, electrodes in LCDs are often made of indium tin oxide (ITO). ITO has good conducting properties and can also make for a transparent electrode which is essential to the appearance of displays today.

How the electrodes affect the liquid crystal alignment can vary depending on the method of alignment used (twistednematic,multi-domain,in-planeswitching). For example, twisted nematic liquid crystals are oriented in a twist when no electric field is present which then polarizes the light passing through the layer; when the electrodes apply the field in full, the twist will straighten out, no longer polarizing the light, and so no light passes. In each of these alignment types, the electrodes are placed differently within the structure, altering the properties of the display, such as width of viewing angle, power consumption, and response time. Despite these different alignment methods, the liquid crystal layer’s purpose remains the same: to polarize the light so that the polarized light passes through to the surface of the display. By polarizing the light transmitted from the backlight, the liquid crystal molecules play a role in how much of the light passes through the polarizing filters, whether it be all, none, or a partial amount.