tyco 17 lcd touch screen reburbished free sample

A touchscreen or touch screen is the assembly of both an input ("touch panel") and output ("display") device. The touch panel is normally layered on the top of an electronic visual display of an information processing system. The display is often an LCD, AMOLED or OLED display while the system is usually used in a laptop, tablet, or smartphone. A user can give input or control the information processing system through simple or multi-touch gestures by touching the screen with a special stylus or one or more fingers.zooming to increase the text size.

The touchscreen enables the user to interact directly with what is displayed, rather than using a mouse, touchpad, or other such devices (other than a stylus, which is optional for most modern touchscreens).

Touchscreens are common in devices such as game consoles, personal computers, electronic voting machines, and point-of-sale (POS) systems. They can also be attached to computers or, as terminals, to networks. They play a prominent role in the design of digital appliances such as personal digital assistants (PDAs) and some e-readers. Touchscreens are also important in educational settings such as classrooms or on college campuses.

The popularity of smartphones, tablets, and many types of information appliances is driving the demand and acceptance of common touchscreens for portable and functional electronics. Touchscreens are found in the medical field, heavy industry, automated teller machines (ATMs), and kiosks such as museum displays or room automation, where keyboard and mouse systems do not allow a suitably intuitive, rapid, or accurate interaction by the user with the display"s content.

Historically, the touchscreen sensor and its accompanying controller-based firmware have been made available by a wide array of after-market system integrators, and not by display, chip, or motherboard manufacturers. Display manufacturers and chip manufacturers have acknowledged the trend toward acceptance of touchscreens as a user interface component and have begun to integrate touchscreens into the fundamental design of their products.

The prototypeCERNFrank Beck, a British electronics engineer, for the control room of CERN"s accelerator SPS (Super Proton Synchrotron). This was a further development of the self-capacitance screen (right), also developed by Stumpe at CERN

One predecessor of the modern touch screen includes stylus based systems. In 1946, a patent was filed by Philco Company for a stylus designed for sports telecasting which, when placed against an intermediate cathode ray tube display (CRT) would amplify and add to the original signal. Effectively, this was used for temporarily drawing arrows or circles onto a live television broadcast, as described in US 2487641A, Denk, William E, "Electronic pointer for television images", issued 1949-11-08. Later inventions built upon this system to free telewriting styli from their mechanical bindings. By transcribing what a user draws onto a computer, it could be saved for future use. See US 3089918A, Graham, Robert E, "Telewriting apparatus", issued 1963-05-14.

The first version of a touchscreen which operated independently of the light produced from the screen was patented by AT&T Corporation US 3016421A, Harmon, Leon D, "Electrographic transmitter", issued 1962-01-09. This touchscreen utilized a matrix of collimated lights shining orthogonally across the touch surface. When a beam is interrupted by a stylus, the photodetectors which no longer are receiving a signal can be used to determine where the interruption is. Later iterations of matrix based touchscreens built upon this by adding more emitters and detectors to improve resolution, pulsing emitters to improve optical signal to noise ratio, and a nonorthogonal matrix to remove shadow readings when using multi-touch.

The first finger driven touch screen was developed by Eric Johnson, of the Royal Radar Establishment located in Malvern, England, who described his work on capacitive touchscreens in a short article published in 1965Frank Beck and Bent Stumpe, engineers from CERN (European Organization for Nuclear Research), developed a transparent touchscreen in the early 1970s,In the mid-1960s, another precursor of touchscreens, an ultrasonic-curtain-based pointing device in front of a terminal display, had been developed by a team around Rainer Mallebrein[de] at Telefunken Konstanz for an air traffic control system.Einrichtung" ("touch input facility") for the SIG 50 terminal utilizing a conductively coated glass screen in front of the display.

In 1972, a group at the University of Illinois filed for a patent on an optical touchscreenMagnavox Plato IV Student Terminal and thousands were built for this purpose. These touchscreens had a crossed array of 16×16 infrared position sensors, each composed of an LED on one edge of the screen and a matched phototransistor on the other edge, all mounted in front of a monochrome plasma display panel. This arrangement could sense any fingertip-sized opaque object in close proximity to the screen. A similar touchscreen was used on the HP-150 starting in 1983. The HP 150 was one of the world"s earliest commercial touchscreen computers.infrared transmitters and receivers around the bezel of a 9-inch Sony cathode ray tube (CRT).

In 1977, an American company, Elographics – in partnership with Siemens – began work on developing a transparent implementation of an existing opaque touchpad technology, U.S. patent No. 3,911,215, October 7, 1975, which had been developed by Elographics" founder George Samuel Hurst.World"s Fair at Knoxville in 1982.

In 1984, Fujitsu released a touch pad for the Micro 16 to accommodate the complexity of kanji characters, which were stored as tiled graphics.Sega released the Terebi Oekaki, also known as the Sega Graphic Board, for the SG-1000 video game console and SC-3000 home computer. It consisted of a plastic pen and a plastic board with a transparent window where pen presses are detected. It was used primarily with a drawing software application.

Touch-sensitive control-display units (CDUs) were evaluated for commercial aircraft flight decks in the early 1980s. Initial research showed that a touch interface would reduce pilot workload as the crew could then select waypoints, functions and actions, rather than be "head down" typing latitudes, longitudes, and waypoint codes on a keyboard. An effective integration of this technology was aimed at helping flight crews maintain a high level of situational awareness of all major aspects of the vehicle operations including the flight path, the functioning of various aircraft systems, and moment-to-moment human interactions.

In the early 1980s, General Motors tasked its Delco Electronics division with a project aimed at replacing an automobile"s non-essential functions (i.e. other than throttle, transmission, braking, and steering) from mechanical or electro-mechanical systems with solid state alternatives wherever possible. The finished device was dubbed the ECC for "Electronic Control Center", a digital computer and software control system hardwired to various peripheral sensors, servos, solenoids, antenna and a monochrome CRT touchscreen that functioned both as display and sole method of input.stereo, fan, heater and air conditioner controls and displays, and was capable of providing very detailed and specific information about the vehicle"s cumulative and current operating status in real time. The ECC was standard equipment on the 1985–1989 Buick Riviera and later the 1988–1989 Buick Reatta, but was unpopular with consumers—partly due to the technophobia of some traditional Buick customers, but mostly because of costly technical problems suffered by the ECC"s touchscreen which would render climate control or stereo operation impossible.

Multi-touch technology began in 1982, when the University of Toronto"s Input Research Group developed the first human-input multi-touch system, using a frosted-glass panel with a camera placed behind the glass. In 1985, the University of Toronto group, including Bill Buxton, developed a multi-touch tablet that used capacitance rather than bulky camera-based optical sensing systems (see History of multi-touch).

The first commercially available graphical point-of-sale (POS) software was demonstrated on the 16-bit Atari 520ST color computer. It featured a color touchscreen widget-driven interface.COMDEX expo in 1986.

In 1987, Casio launched the Casio PB-1000 pocket computer with a touchscreen consisting of a 4×4 matrix, resulting in 16 touch areas in its small LCD graphic screen.

Touchscreens had a bad reputation of being imprecise until 1988. Most user-interface books would state that touchscreen selections were limited to targets larger than the average finger. At the time, selections were done in such a way that a target was selected as soon as the finger came over it, and the corresponding action was performed immediately. Errors were common, due to parallax or calibration problems, leading to user frustration. "Lift-off strategy"University of Maryland Human–Computer Interaction Lab (HCIL). As users touch the screen, feedback is provided as to what will be selected: users can adjust the position of the finger, and the action takes place only when the finger is lifted off the screen. This allowed the selection of small targets, down to a single pixel on a 640×480 Video Graphics Array (VGA) screen (a standard of that time).

Sears et al. (1990)human–computer interaction of the time, describing gestures such as rotating knobs, adjusting sliders, and swiping the screen to activate a switch (or a U-shaped gesture for a toggle switch). The HCIL team developed and studied small touchscreen keyboards (including a study that showed users could type at 25 wpm on a touchscreen keyboard), aiding their introduction on mobile devices. They also designed and implemented multi-touch gestures such as selecting a range of a line, connecting objects, and a "tap-click" gesture to select while maintaining location with another finger.

In 1990, HCIL demonstrated a touchscreen slider,lock screen patent litigation between Apple and other touchscreen mobile phone vendors (in relation to

An early attempt at a handheld game console with touchscreen controls was Sega"s intended successor to the Game Gear, though the device was ultimately shelved and never released due to the expensive cost of touchscreen technology in the early 1990s.

Touchscreens would not be popularly used for video games until the release of the Nintendo DS in 2004.Apple Watch being released with a force-sensitive display in April 2015.

In 2007, 93% of touchscreens shipped were resistive and only 4% were projected capacitance. In 2013, 3% of touchscreens shipped were resistive and 90% were projected capacitance.

A resistive touchscreen panel comprises several thin layers, the most important of which are two transparent electrically resistive layers facing each other with a thin gap between. The top layer (that which is touched) has a coating on the underside surface; just beneath it is a similar resistive layer on top of its substrate. One layer has conductive connections along its sides, the other along top and bottom. A voltage is applied to one layer and sensed by the other. When an object, such as a fingertip or stylus tip, presses down onto the outer surface, the two layers touch to become connected at that point.voltage dividers, one axis at a time. By rapidly switching between each layer, the position of pressure on the screen can be detected.

Resistive touch is used in restaurants, factories and hospitals due to its high tolerance for liquids and contaminants. A major benefit of resistive-touch technology is its low cost. Additionally, as only sufficient pressure is necessary for the touch to be sensed, they may be used with gloves on, or by using anything rigid as a finger substitute. Disadvantages include the need to press down, and a risk of damage by sharp objects. Resistive touchscreens also suffer from poorer contrast, due to having additional reflections (i.e. glare) from the layers of material placed over the screen.3DS family, and the Wii U GamePad.

Surface acoustic wave (SAW) technology uses ultrasonic waves that pass over the touchscreen panel. When the panel is touched, a portion of the wave is absorbed. The change in ultrasonic waves is processed by the controller to determine the position of the touch event. Surface acoustic wave touchscreen panels can be damaged by outside elements. Contaminants on the surface can also interfere with the functionality of the touchscreen.

The Casio TC500 Capacitive touch sensor watch from 1983, with angled light exposing the touch sensor pads and traces etched onto the top watch glass surface.

A capacitive touchscreen panel consists of an insulator, such as glass, coated with a transparent conductor, such as indium tin oxide (ITO).electrostatic field, measurable as a change in capacitance. Different technologies may be used to determine the location of the touch. The location is then sent to the controller for processing. Touchscreens that use silver instead of ITO exist, as ITO causes several environmental problems due to the use of indium.complementary metal-oxide-semiconductor (CMOS) application-specific integrated circuit (ASIC) chip, which in turn usually sends the signals to a CMOS digital signal processor (DSP) for processing.

Unlike a resistive touchscreen, some capacitive touchscreens cannot be used to detect a finger through electrically insulating material, such as gloves. This disadvantage especially affects usability in consumer electronics, such as touch tablet PCs and capacitive smartphones in cold weather when people may be wearing gloves. It can be overcome with a special capacitive stylus, or a special-application glove with an embroidered patch of conductive thread allowing electrical contact with the user"s fingertip.

A low-quality switching-mode power supply unit with an accordingly unstable, noisy voltage may temporarily interfere with the precision, accuracy and sensitivity of capacitive touch screens.

Some capacitive display manufacturers continue to develop thinner and more accurate touchscreens. Those for mobile devices are now being produced with "in-cell" technology, such as in Samsung"s Super AMOLED screens, that eliminates a layer by building the capacitors inside the display itself. This type of touchscreen reduces the visible distance between the user"s finger and what the user is touching on the screen, reducing the thickness and weight of the display, which is desirable in smartphones.

In this basic technology, only one side of the insulator is coated with a conductive layer. A small voltage is applied to the layer, resulting in a uniform electrostatic field. When a conductor, such as a human finger, touches the uncoated surface, a capacitor is dynamically formed. The sensor"s controller can determine the location of the touch indirectly from the change in the capacitance as measured from the four corners of the panel. As it has no moving parts, it is moderately durable but has limited resolution, is prone to false signals from parasitic capacitive coupling, and needs calibration during manufacture. It is therefore most often used in simple applications such as industrial controls and kiosks.

This diagram shows how eight inputs to a lattice touchscreen or keypad creates 28 unique intersections, as opposed to 16 intersections created using a standard x/y multiplexed touchscreen .

Projected capacitive touch (PCT; also PCAP) technology is a variant of capacitive touch technology but where sensitivity to touch, accuracy, resolution and speed of touch have been greatly improved by the use of a simple form of

Some modern PCT touch screens are composed of thousands of discrete keys,etching a single conductive layer to form a grid pattern of electrodes, by etching two separate, perpendicular layers of conductive material with parallel lines or tracks to form a grid, or by forming an x/y grid of fine, insulation coated wires in a single layer . The number of fingers that can be detected simultaneously is determined by the number of cross-over points (x * y) . However, the number of cross-over points can be almost doubled by using a diagonal lattice layout, where, instead of x elements only ever crossing y elements, each conductive element crosses every other element .

In some designs, voltage applied to this grid creates a uniform electrostatic field, which can be measured. When a conductive object, such as a finger, comes into contact with a PCT panel, it distorts the local electrostatic field at that point. This is measurable as a change in capacitance. If a finger bridges the gap between two of the "tracks", the charge field is further interrupted and detected by the controller. The capacitance can be changed and measured at every individual point on the grid. This system is able to accurately track touches.

Unlike traditional capacitive touch technology, it is possible for a PCT system to sense a passive stylus or gloved finger. However, moisture on the surface of the panel, high humidity, or collected dust can interfere with performance.

These environmental factors, however, are not a problem with "fine wire" based touchscreens due to the fact that wire based touchscreens have a much lower "parasitic" capacitance, and there is greater distance between neighbouring conductors.

This is a common PCT approach, which makes use of the fact that most conductive objects are able to hold a charge if they are very close together. In mutual capacitive sensors, a capacitor is inherently formed by the row trace and column trace at each intersection of the grid. A 16×14 array, for example, would have 224 independent capacitors. A voltage is applied to the rows or columns. Bringing a finger or conductive stylus close to the surface of the sensor changes the local electrostatic field, which in turn reduces the mutual capacitance. The capacitance change at every individual point on the grid can be measured to accurately determine the touch location by measuring the voltage in the other axis. Mutual capacitance allows multi-touch operation where multiple fingers, palms or styli can be accurately tracked at the same time.

Self-capacitive touch screen layers are used on mobile phones such as the Sony Xperia Sola,Samsung Galaxy S4, Galaxy Note 3, Galaxy S5, and Galaxy Alpha.

Self capacitance is far more sensitive than mutual capacitance and is mainly used for single touch, simple gesturing and proximity sensing where the finger does not even have to touch the glass surface.

Capacitive touchscreens do not necessarily need to be operated by a finger, but until recently the special styli required could be quite expensive to purchase. The cost of this technology has fallen greatly in recent years and capacitive styli are now widely available for a nominal charge, and often given away free with mobile accessories. These consist of an electrically conductive shaft with a soft conductive rubber tip, thereby resistively connecting the fingers to the tip of the stylus.

Infrared sensors mounted around the display watch for a user"s touchscreen input on this PLATO V terminal in 1981. The monochromatic plasma display"s characteristic orange glow is illustrated.

An infrared touchscreen uses an array of X-Y infrared LED and photodetector pairs around the edges of the screen to detect a disruption in the pattern of LED beams. These LED beams cross each other in vertical and horizontal patterns. This helps the sensors pick up the exact location of the touch. A major benefit of such a system is that it can detect essentially any opaque object including a finger, gloved finger, stylus or pen. It is generally used in outdoor applications and POS systems that cannot rely on a conductor (such as a bare finger) to activate the touchscreen. Unlike capacitive touchscreens, infrared touchscreens do not require any patterning on the glass which increases durability and optical clarity of the overall system. Infrared touchscreens are sensitive to dirt and dust that can interfere with the infrared beams, and suffer from parallax in curved surfaces and accidental press when the user hovers a finger over the screen while searching for the item to be selected.

A translucent acrylic sheet is used as a rear-projection screen to display information. The edges of the acrylic sheet are illuminated by infrared LEDs, and infrared cameras are focused on the back of the sheet. Objects placed on the sheet are detectable by the cameras. When the sheet is touched by the user, frustrated total internal reflection results in leakage of infrared light which peaks at the points of maximum pressure, indicating the user"s touch location. Microsoft"s PixelSense tablets use this technology.

Optical touchscreens are a relatively modern development in touchscreen technology, in which two or more image sensors (such as CMOS sensors) are placed around the edges (mostly the corners) of the screen. Infrared backlights are placed in the sensor"s field of view on the opposite side of the screen. A touch blocks some lights from the sensors, and the location and size of the touching object can be calculated (see visual hull). This technology is growing in popularity due to its scalability, versatility, and affordability for larger touchscreens.

Introduced in 2002 by 3M, this system detects a touch by using sensors to measure the piezoelectricity in the glass. Complex algorithms interpret this information and provide the actual location of the touch.

The key to this technology is that a touch at any one position on the surface generates a sound wave in the substrate which then produces a unique combined signal as measured by three or more tiny transducers attached to the edges of the touchscreen. The digitized signal is compared to a list corresponding to every position on the surface, determining the touch location. A moving touch is tracked by rapid repetition of this process. Extraneous and ambient sounds are ignored since they do not match any stored sound profile. The technology differs from other sound-based technologies by using a simple look-up method rather than expensive signal-processing hardware. As with the dispersive signal technology system, a motionless finger cannot be detected after the initial touch. However, for the same reason, the touch recognition is not disrupted by any resting objects. The technology was created by SoundTouch Ltd in the early 2000s, as described by the patent family EP1852772, and introduced to the market by Tyco International"s Elo division in 2006 as Acoustic Pulse Recognition.

There are several principal ways to build a touchscreen. The key goals are to recognize one or more fingers touching a display, to interpret the command that this represents, and to communicate the command to the appropriate application.

Dispersive-signal technology measures the piezoelectric effect—the voltage generated when mechanical force is applied to a material—that occurs chemically when a strengthened glass substrate is touched.

There are two infrared-based approaches. In one, an array of sensors detects a finger touching or almost touching the display, thereby interrupting infrared light beams projected over the screen. In the other, bottom-mounted infrared cameras record heat from screen touches.

The development of multi-touch screens facilitated the tracking of more than one finger on the screen; thus, operations that require more than one finger are possible. These devices also allow multiple users to interact with the touchscreen simultaneously.

With the growing use of touchscreens, the cost of touchscreen technology is routinely absorbed into the products that incorporate it and is nearly eliminated. Touchscreen technology has demonstrated reliability and is found in airplanes, automobiles, gaming consoles, machine control systems, appliances, and handheld display devices including cellphones; the touchscreen market for mobile devices was projected to produce US$5 billion by 2009.

The ability to accurately point on the screen itself is also advancing with the emerging graphics tablet-screen hybrids. Polyvinylidene fluoride (PVDF) plays a major role in this innovation due its high piezoelectric properties, which allow the tablet to sense pressure, making such things as digital painting behave more like paper and pencil.

TapSense, announced in October 2011, allows touchscreens to distinguish what part of the hand was used for input, such as the fingertip, knuckle and fingernail. This could be used in a variety of ways, for example, to copy and paste, to capitalize letters, to activate different drawing modes, etc.

For touchscreens to be effective input devices, users must be able to accurately select targets and avoid accidental selection of adjacent targets. The design of touchscreen interfaces should reflect technical capabilities of the system, ergonomics, cognitive psychology and human physiology.

Guidelines for touchscreen designs were first developed in the 2000s, based on early research and actual use of older systems, typically using infrared grids—which were highly dependent on the size of the user"s fingers. These guidelines are less relevant for the bulk of modern touch devices which use capacitive or resistive touch technology.

Much more important is the accuracy humans have in selecting targets with their finger or a pen stylus. The accuracy of user selection varies by position on the screen: users are most accurate at the center, less so at the left and right edges, and least accurate at the top edge and especially the bottom edge. The R95 accuracy (required radius for 95% target accuracy) varies from 7 mm (0.28 in) in the center to 12 mm (0.47 in) in the lower corners.

This user inaccuracy is a result of parallax, visual acuity and the speed of the feedback loop between the eyes and fingers. The precision of the human finger alone is much, much higher than this, so when assistive technologies are provided—such as on-screen magnifiers—users can move their finger (once in contact with the screen) with precision as small as 0.1 mm (0.004 in).

Users of handheld and portable touchscreen devices hold them in a variety of ways, and routinely change their method of holding and selection to suit the position and type of input. There are four basic types of handheld interaction:

Touchscreens are often used with haptic response systems. A common example of this technology is the vibratory feedback provided when a button on the touchscreen is tapped. Haptics are used to improve the user"s experience with touchscreens by providing simulated tactile feedback, and can be designed to react immediately, partly countering on-screen response latency. Research from the University of Glasgow (Brewster, Chohan, and Brown, 2007; and more recently Hogan) demonstrates that touchscreen users reduce input errors (by 20%), increase input speed (by 20%), and lower their cognitive load (by 40%) when touchscreens are combined with haptics or tactile feedback. On top of this, a study conducted in 2013 by Boston College explored the effects that touchscreens haptic stimulation had on triggering psychological ownership of a product. Their research concluded that a touchscreens ability to incorporate high amounts of haptic involvement resulted in customers feeling more endowment to the products they were designing or buying. The study also reported that consumers using a touchscreen were willing to accept a higher price point for the items they were purchasing.

Unsupported touchscreens are still fairly common in applications such as ATMs and data kiosks, but are not an issue as the typical user only engages for brief and widely spaced periods.

Touchscreens can suffer from the problem of fingerprints on the display. This can be mitigated by the use of materials with optical coatings designed to reduce the visible effects of fingerprint oils. Most modern smartphones have oleophobic coatings, which lessen the amount of oil residue. Another option is to install a matte-finish anti-glare screen protector, which creates a slightly roughened surface that does not easily retain smudges.

Touchscreens do not work most of the time when the user wears gloves. The thickness of the glove and the material they are made of play a significant role on that and the ability of a touchscreen to pick up a touch.

Walker, Geoff (August 2012). "A review of technologies for sensing contact location on the surface of a display: Review of touch technologies". Journal of the Society for Information Display. 20 (8): 413–440. doi:10.1002/jsid.100. S2CID 40545665.

"The first capacitative touch screens at CERN". CERN Courrier. 31 March 2010. Archived from the original on 4 September 2010. Retrieved 2010-05-25. Cite journal requires |journal= (help)

Beck, Frank; Stumpe, Bent (May 24, 1973). Two devices for operator interaction in the central control of the new CERN accelerator (Report). CERN. CERN-73-06. Retrieved 2017-09-14.

Johnson, E.A. (1965). "Touch Display - A novel input/output device for computers". Electronics Letters. 1 (8): 219–220. Bibcode:1965ElL.....1..219J. doi:10.1049/el:19650200.

Stumpe, Bent; Sutton, Christine (1 June 2010). "CERN touch screen". Symmetry Magazine. A joint Fermilab/SLAC publication. Archived from the original on 2016-11-16. Retrieved 16 November 2016.

Mallebrein, Rainer (2018-02-18). "Oral History of Rainer Mallebrein" (PDF) (Interview). Interviewed by Steinbach, Günter. Singen am Hohentwiel, Germany: Computer History Museum. CHM Ref: X8517.2018. Archived (PDF) from the original on 2021-01-27. Retrieved 2021-08-23. (18 pages)

Biferno, M. A., Stanley, D. L. (1983). The Touch-Sensitive Control/Display Unit: A Promising Computer Interface. Technical Paper 831532, Aerospace Congress & Exposition, Long Beach, CA: Society of Automotive Engineers.

Potter, R.; Weldon, L.; Shneiderman, B. (1988). "Improving the accuracy of touch screens: an experimental evaluation of three strategies". Proceedings of the SIGCHI conference on Human factors in computing systems - CHI "88. Proc. of the Conference on Human Factors in Computing Systems, CHI "88. Washington, DC. pp. 27–32. doi:10.1145/57167.57171. ISBN 0201142376. Archived from the original on 2015-12-08.

Sears, Andrew; Plaisant, Catherine; Shneiderman, Ben (June 1990). "A new era for high-precision touchscreens". In Hartson, R.; Hix, D. (eds.). Advances in Human-Computer Interaction. Vol. 3. Ablex (1992). ISBN 978-0-89391-751-7. Archived from the original on October 9, 2014.

Apple touch-screen patent war comes to the UK (2011). Event occurs at 1:24 min in video. Archived from the original on 8 December 2015. Retrieved 3 December 2015.

Hong, Chan-Hwa; Shin, Jae-Heon; Ju, Byeong-Kwon; Kim, Kyung-Hyun; Park, Nae-Man; Kim, Bo-Sul; Cheong, Woo-Seok (1 November 2013). "Index-Matched Indium Tin Oxide Electrodes for Capacitive Touch Screen Panel Applications". Journal of Nanoscience and Nanotechnology. 13 (11): 7756–7759. doi:10.1166/jnn.2013.7814. PMID 24245328. S2CID 24281861.

Kent, Joel (May 2010). "Touchscreen technology basics & a new development". CMOS Emerging Technologies Conference. CMOS Emerging Technologies Research. 6: 1–13. ISBN 9781927500057.

Ganapati, Priya (5 March 2010). "Finger Fail: Why Most Touchscreens Miss the Point". Archived from the original on 2014-05-11. Retrieved 9 November 2019.

Beyers, Tim (2008-02-13). "Innovation Series: Touchscreen Technology". The Motley Fool. Archived from the original on 2009-03-24. Retrieved 2009-03-16.

"Acoustic Pulse Recognition Touchscreens" (PDF). Elo Touch Systems. 2006: 3. Archived (PDF) from the original on 2011-09-05. Retrieved 2011-09-27. Cite journal requires |journal= (help)

Hoober, Steven (2013-11-11). "Design for Fingers and Thumbs Instead of Touch". UXmatters. Archived from the original on 2014-08-26. Retrieved 2014-08-24.

Henze, Niels; Rukzio, Enrico; Boll, Susanne (2011). "100,000,000 Taps: Analysis and Improvement of Touch Performance in the Large". Proceedings of the 13th International Conference on Human Computer Interaction with Mobile Devices and Services. New York.

Lee, Seungyons; Zhai, Shumin (2009). "The Performance of Touch Screen Soft Buttons". Proceedings of the SIGCHI Conference on Human Factors in Computing Systems. New York: 309. doi:10.1145/1518701.1518750. ISBN 9781605582467. S2CID 2468830.

Bérard, François (2012). "Measuring the Linear and Rotational User Precision in Touch Pointing". Proceedings of the 2012 ACM International Conference on Interactive Tabletops and Surfaces. New York: 183. doi:10.1145/2396636.2396664. ISBN 9781450312097. S2CID 15765730.

Hoober, Steven (2014-09-02). "Insights on Switching, Centering, and Gestures for Touchscreens". UXmatters. Archived from the original on 2014-09-06. Retrieved 2014-08-24.

Brasel, S. Adam; Gips, James (2014). "Tablets, touchscreens, and touchpads: How varying touch interfaces trigger psychological ownership and endowment". Journal of Consumer Psychology. 24 (2): 226–233. doi:10.1016/j.jcps.2013.10.003.

Zhu, Ying; Meyer, Jeffrey (September 2017). "Getting in touch with your thinking style: How touchscreens influence purchase". Journal of Retailing and Consumer Services. 38: 51–58. doi:10.1016/j.jretconser.2017.05.006.

"A RESTAURANT THAT LETS GUESTS PLACE ORDERS VIA A TOUCHSCREEN TABLE (Touche is said to be the first touchscreen restaurant in India and fifth in the world)". India Business Insight. 31 August 2011. Gale A269135159.

Sears, A.; Plaisant, C. & Shneiderman, B. (1992). "A new era for high precision touchscreens". In Hartson, R. & Hix, D. (eds.). Advances in Human-Computer Interaction. Vol. 3. Ablex, NJ. pp. 1–33.

Sears, Andrew; Shneiderman, Ben (April 1991). "High precision touchscreens: design strategies and comparisons with a mouse". International Journal of Man-Machine Studies. 34 (4): 593–613. doi:10.1016/0020-7373(91)90037-8. hdl:

BACKGROUND OF THE INVENTION The present invention relates to a touch screen display and, more particularly, to a reflection resistant, touch sensitive display.

A touch screen display permits a user to input information to a computer system by touching an icon or other visual element displayed on a screen or by tracing a symbol on a screen to be identified and interpreted by the computer system. Direct user interaction through a touch sensitive screen is considered to be one of the most intuitive methods of computer input. As a result, touch screens have been widely applied to personal digital equipment; to public access data processing systems, such as self-service fuel pumps, automated teller machines and automated ticketing systems; and to instrumentation and controls for medical equipment, aircraft, and vehicles.

Several types of touch screens have developed to address the needs of the wide variety of potential applications. Surface Acoustic Wave (SAW) touch screens cojmprise a glass panel with acoustic transceivers attached to three corners and reflecting stripes arranged along the edges. The transceivers generate inaudible sound waves that travel across the screen. When a user"s finger makes contact with the screen, a portion of the wave"s energy is absorbed. The touch screen controller detects the energy loss and calculates the coordinates of the contact. A Near Field Imaging (NFI) touch screen comprises a base layer and a front layer of glass separated by a transparent conductive film deposited in a patterned topology. A controller applies an excitation waveform to the conductive

layer to generate a low strength electrostatic field in the front layer of glass. The field is modulated when the glass is contacted by a finger or a conductive stylus, producing a differential signal that is detected and spatially resolved by the controller to determine the location of the contact with the screen. Capacitive touch screens comprise multiple layers of glass with a thin conductive film between a pair of glass layers. A narrow pattern of electrodes is placed between glass layers. The conductive film may be, for example, patterned indium tin oxide (ITO) or a thin wire mesh. An oscillator circuit attached to each corner of the screen induces a low voltage electric field in the coating. When the glass screen is touched, the properties of the electric field change. The touch screen"s controller computes the coordinates of the point of contact with the screen by measuring the relative changes of the electric field at a plurality of electrodes.

The most popular type of touch screen is a resistive touch screen. Resistive touch screens comprise a substantially rigid substrate and a flexible cover each having a surface coated with a transparent conductive material, usually indium tin oxide (ITO). The substrate and cover are bonded together with the conductive surfaces facing each other but separated by an air gap produced by a pattern of transparent insulators deployed on one of the surfaces. When a user presses on the flexible cover, the cover is deformed and the conductive surfaces make contact. A controller measures the voltage drop in circuits resulting from contact between the conductive layers to determine the coordinates of the point at which the contact was made.

Resistive and capacitive touch sensitive systems are typically produced as a transparent, touch-sensitive panel that is placed in front of the screen or display surface of the underlying electronic display. The touch sensitive systems are commonly used in conjunction with several types of displays including cathode ray tubes (CRTs) and liquid crystal displays (LCDs). LCD-based displays are preferred for many touch screen applications because LCDs are lighter, more compact, more rugged, and use less energy than CRT displays.

Generally, an LCD comprises a light valve that controls the intensity of light passing through the panel from a source at the back of the LCD (a "backlight") to a viewer"s eyes at the front of the panel. The light valve generally comprises a pair of polarizers separated by layer of liquid crystals filling a cell gap between the polarizers. The optical axes of the two polarizers are arranged relative to each other so that light from the backlight is either blocked or transmitted through the polarizers. The liquid crystals are birefringent and translucent and the relative orientation of the crystals of the layer can be controlled to switch the light valve from a transmitting state where light is transmitted through the two polarizers to a non-transmitting state where light transmission is blocked. For example, the walls of the cell gap may be buffed to create microscopic grooves that orient adjacent molecules of liquid crystal with optical axes of the two polarizers. Liquid crystals exhibit a dipole that attracts neighboring crystals and causing the crystals of columns spanning the liquid crystal layer to align with each other. If the crystals at the limits of the layer are arranged at an angle to each other to align with the optical axis of the polarizers, the crystals of the intervening column will be progressively twisted into alignment by the dipole. The plane of vibration of light transmitted from the first polarizer passing through a column of crystals is also "twisted" so that it is aligned with the optical axis of the second polarizer and visible to the viewer (in a "normally white" LCD). To turn a pixel off and create an image, a voltage is applied to an electrode of an array of electrodes on the walls of the cell gap with reference to a common electrode causing adjacent liquid crystals to be twisted out of alignment with the optical axis of the adjacent polarizer attenuating the light transmitted from the backlight to the viewer. (Conversely, the polarizers of the light valve of a "normally black" LCD are arranged so that the pixel is "off" or "black" when the controlling electrode is not energized and switched

While LCDs are the displays of choice for many touch screen applications, the combination of an LCD display device and a touch panel can be problematic. The principal problem is that touch panels are reflective and, when exposed to

The reflectivity of a resistive touch panel is principally the result of coating the facing surfaces of the cover and the substrate with the transparent conductive coating of ITO. ITO has a relatively high index of refraction (typically, n=1.83 for light in the green wavelengths) while the air in the gap between the resistive surfaces has an index of refraction of 1.0. The percentage of perpendicularly incident light reflected from a discontinuity in the index of refraction is, approximately:

where: n2 = index of refraction for the optically denser material n1 = index of refraction for the optically less dense material R = percentage of incident light reflected (It is noted that the aforementioned equation is only accurate for perpendicular viewing directions.) The result of two transitions of the air-to-lTO boundaries by ambient light from the front of the panel is reflection of roughly 17% of the ambient light incident on the panel. This reflection is sufficient to obscure the displayed image under modest to high intensity ambient lighting conditions.

Sawai et al., U.S. Patent No. 6,020,945, disclose an optical filter for a resistive touch panel that is intended to prevent reflection of external light and obscuration of the displayed image. The optical filter comprises, generally, a filter polarizer in front of the screen of the display. The filter polarizer may be a circular polarizer comprising a combination of a linear polarizer and a quarter wave phase difference plate. Much of the ambient light striking the front of the panel is absorbed by the filter polarizer. In addition, light passing through the filter polarizer and reflecting from the ITO layers passes twice through a quarter wave phase difference plate. The phase difference plate alters the polarization of the reflected light so that the reflected light is blocked by the filter polarizer.

On the other hand, the linear polarized light of the image from the LCD light valve is circular polarized by a second phase difference plate before passing through the touch panel. The optical axis of a circular polarizing, filter polarizer is aligned so that the circular polarized light from the LCD is transmitted through the filter polarizer to the viewer. While a touch panel filter reduces reflection of ambient light, the combination of the filter polarizer and phase difference plates substantially attenuates the light from the light valve reducing the brightness of the image, and the combination of the touch panel and filter substantially distort the image. What is desired, therefore, is a touch screen providing substantially reduced reflection of ambient light and an undistorted image.

FIG. 2 is an exploded cross-section of a touch screen comprising a resistive , touch panel of alternative construction and an associated liquid crystal display (LCD). FIG. 3 is a schematic representation of the arrangement of the conductive elements of an exemplary four-wire resistive touch panel.

FIG. 4 is an equivalent circuit of an exemplary four-wire resistive touch panel. FIG. 5 is an isocontrast plot of the output of an exemplary LCD. FIG. 6 is an isocontrast plot of the output of a touch screen comprising the exemplary LCD of FIG. 5 and a resistive touch panel.

FIG. 7 is an isocontrast plot of the output of a touch screen comprising the exemplary LCD of FIG. 5 and a resistive touch panel including a front polarizer. FIG. 8 is an exploded cross-section of a reflection resistant touch screen comprising a capacitive touch panel and an associated LCD.

TABLE 1 A is a table of alternate reflection resistant touch screen constructions indicating arrangements and characteristics of touch screen elements. TABLE 1 B is a table of the specular reflection contributions from the components of the touch screens of alternate construction described in TABLE 1A. TABLE 1 C is a table of the diffuse reflection contributions from the components of the touch screens of alternate construction described in TABLE 1A. TABLE 1 D is a table illustrating the optical performance of the touch screens of alternate construction described in TABLE 1 A.

Referring to FIGS. 1 and 2 (like elements are identified by common item numbers), a touch screen generally comprises a transparent touch sensitive panel 68 (indicated by a bracket) which is installed proximate to the display screen of a computer operated display, such as a liquid crystal display (LCD) 50 or a cathode ray tube (CRT) monitor. A user can see the displayed image through the touch panel and interact with the computer system by touching the front surface of the touch panel at a location designated by the computer with the display of an icon or other visible indicator. Typically, touch panels and displays are produced as separate units and are often supplied by different manufacturers.

A liquid crystal display (LCD) 50 (indicated by a bracket) comprises generally, a backlight 52 and a light valve 54 (indicated by a bracket). Since liquid crystals do not emit light, most LCD panels are backlit with flourescent tubes or arrays of light-emitting diodes (LEDs) that are built into the sides or back of the panel. To disperse the light and obtain a more uniform intensity over the surface of the display, light from the backlight 52 typically passes through a diffuser 56 before impinging on the light valve 54. The transmittance of light from the backlight 52 to the eye of a viewer 58,

observing an image displayed on the front of the panel, is controlled by the light valve 54. The light valve 54 comprises a pair of polarizers 60 and 62 separated by a layer of liquid crystals 64 contained in a cell gap between the polarizers. Light from the backlight 52 impinging on the first polarizer 62 comprises electromagnetic waves vibrating in a plurality of planes. Only that portion of the light vibrating in the plane of the optical axis of a polarizer can pass through the polarizer. In an LCD light valve, the optical axes of the first 62 and second 60 polarizers are typically arranged at an angle so that light passing through the first polarizer would normally be blocked from passing through the second polarizer in the series. However, the orientation of the translucent crystals in the layer of liquid crystals 64 can be locally controlled to either "twist" the vibratory plane of the light into alignment with the optical axes of the polarizers, permitting light to pass through the light valve creating a bright picture element or pixel, or out of alignment with the optical axis of one of the polarizers, attenuating the light and creating a darker area of the screen or pixel.

The surfaces of a first glass plate 63 and a second glass plate 51 form the walls of the cell gap and are buffed to produce microscopic grooves to physically align the molecules of liquid crystal 64 immediately adjacent to the walls. Molecular forces cause adjacent liquid crystal molecules to attempt to align with their neighbors with the result that the orientation of the molecules in the column of molecules spanning the cell gap twist over the length of the column. Likewise, the plane of vibration of light transiting the column of molecules will be "twisted" from the optical axis of the first polarizer 62 to a plane determined by the orientation of the liquid crystals at the opposite wall of the cell gap. If the wall of the cell gap is buffed to align adjacent crystals with the optical axis of the second polarizer, light from the backlight 52 can pass through the series of polarizers 60 and 62 to produce a lighted area of the display when viewed from the front of the panel (a "normally white" LCD).

deposited on the walls of the cell gap. The liquid crystal molecules adjacent to the electrode are attracted by the field produced by the voltage and rotate to align with the field. As the molecules of liquid crystal are rotated by the electric field, the column of crystals is "untwisted," and the optical axes of the crystals adjacent to the cell wall are rotated progressively out of alignment with the optical axis of the corresponding polarizer progressively reducing the local transmittance of the light valve 54 and attenuating the luminance of the corresponding pixel. Conversely, the polarizers and buffing of the light valve can be arranged to produce a "normally black" LCD having pixels that are dark (light is blocked) when the electrodes are not energized and light when the electrodes are energized. Color LCD displays are created by varying the intensity of transmitted light for each of a plurality of primary color (typically, red, green, and blue) sub-pixels that make up a displayed pixel.

The. aforementioned example was described with respect to a twisted nematic device. However, this description is only an example and other devices may likewise be used, including, but not limited to, multi-domain vertical alignment (MVA), patterened vertical alignment (PVA), in-plane switching (IPS), and super- twisted nematic (STN) type LCDs.

Several touch panel technologies are available. Resistive touch panels are typically the least expensive and, therefore, the most common. Referring to FIG.1 , a resistive touch panel 68 (indicated by a bracket) comprises generally a i substantially rigid, transparent substrate 70 and a flexible cover 72 that are bonded together but separated by an air gap 74 that is maintained by a plurality of transparent insulators 76 that are deployed between the substrate and the cover. The proximate surfaces 78 and 80 of the substrate 70 and flexible cover 72, respectively, are coated with a transparent conductive material, typically, indium tin oxide (ITO). Referring to FIG. 3, the conductive ITO layers 78 and 80 deposited on the cover 72 and the substrate 70, respectively, comprise resistive conductors between a pair of bus bars at the top 100 and bottom 102 edges of the cover substrate and the right 106 and left 104 edges of the other panel element

A touch screen controller 108 determines the coordinates of the point of contact by measuring voltage between points in the circuits that are completed through the conductive surface layers. Resistive touch panels are generally classified as four-wire, five-wire, and eight-wire touch panels according to the number of conductors in the resistive circuit. For example, FIG. 4 illustrates an equivalent circuit 120 of a four-wire resistive touch panel. The controller 108 compares the voltage between either the top bus bar 100 or the bottom bus bar 102 of the first layer and one of the left 104 and right 106 bus bars of the second conductive layer with a reference voltage (top bus bar 100 to bottom bus bar 102) to determine the x-coordinate of the contact point 122. The controller 108 then switches the procedure and determines the y-coordinate of the screen touch by comparing the reference voltage to the voltage between either the right 104 or left 106 bus bar of the second layer and either the top 100 or bottom 102 bus bar of the first layer. _

LCD-based touch screens are highly desirable for many applications because an LCD is lighter, more rugged, more energy efficient, and more compact than a CRT. However, a resistive touch panel 68 is very reflective and in modest to high intensity ambient lighting the luminance of the reflection from the touch panel may be sufficient to obscure the image displayed by an LCD.

The readability of an LCD is a function of the luminance (brightness) and contrast of the LCD display and the luminance of the reflected ambient light. While the brightness of the LCD can be increased by increasing the intensity of the backlight, the contrast between light and dark areas of the screen is limited by the ability of the light valve to extinguish light from the backlight to produce darkened pixels. The contrast of the screen is typically specified by the ratio of the contrast of light and dark pixels:

L = luminance of white state (lighted pixel) LB = luminance of black state (darkened pixel) The contrast ratio is typically specified for a display viewed in a darkened room because of the effect of reflected ambient light on the contrast ratio at a defined viewing angle. For example, an LCD with a white state luminance of 200 nits and a black state luminance of 0.5 nits has a contrast ratio of 400 when viewed in a darkened room. On the other hand, if the LCD is viewed in a well-lit room that produces a glare of 20 nits at the front surface, the white state luminance will be 220 nits, the black state luminance will be 20.5 nits, and the contrast ratio will be 10.7 (220/20.5) substantially less than the contrast ratio for the display in the darkened room. Since the extinction ratio of the light valve and, therefore, the contrast ratio of the LCD in a darkened room are essentially fixed, increasing the brightness of the backlight to overcome the effects of ambient light reflections produces limited improvements in the readability of the display. Reducing the reflection of ambient light from a touch panel without significantly reducing the brightness or the contrast ratio of the displayed image can significantly improve the readability of LCD displays used in environments with higher intensity ambient lighting.

Ambient light impinging on the front of a touch screen passes through the transparent layers of the touch panel and the LCD. Light is reflected when it crosses the boundary between two materials that have differing indices of refraction. For example, the high reflectivity of the resistive touch panel is principally the result of the interaction of ambient light with the resistive coating on the proximate surfaces 78 and 80 of the substrate 70 and cover 72 of the touch panel. Indium tin oxide (ITO) is commonly used to create the transparent conductive surfaces on the substrate and cover. ITO has a high index of refraction

(typically, n=1.83 for light in the green wavelengths) while the air in the gap between the resistive surfaces has an index of refraction of 1.0. As a result of transiting the air-ITO interface, a substantial portion of the ambient light impinging on the front of the panel is reflected back to the viewer 58. A polarizer 82 arranged in front of the touch screen can significantly reduce the reflection of ambient light. The ambient light randomly vibrates in all planes, but only that portion of the light vibrating in the plane of a polarizer can pass through the polarizer. As a result, a polarizer in front of the touch screen substantially reduces the light reaching the ITO interfaces for reflection back to the viewer 58. If the optical axis of the polarizer 82 on the front of the screen is aligned with the optical axis of the second polarizer 60 of the light valve 54 transmission of the image from the light valve is maximized. However, adding a polarizer 82 to the front of the touch screen distorts the image. The present inventor concluded that the image distortion is primarily the result of the interaction of the polarized light comprising the image with birefringent materials interposed between the light valve and the polarizer 82. For example, the flexible cover of resistive touch panels is typically manufactured from polyester (PET) which is birefringent as a result of its molecular structure. In addition, the birefringence of a material is altered by the effects of local strain on the molecular structure. When the flexible cover of a resistive touch panel is deformed by contact, stress causes the birefringence of the cover to vary spatially. As a result, the polarizer 82 interferes to varying degrees with the polarized light comprising the image and the image is distorted. The present inventor concluded that reflection of ambient light could be reduced by arranging a polarizer in front of the touch panel and that the image quality could be preserved by avoiding introducing birefringence in the optical path between the light valve 54 and the viewer 58.

In the LCD touch screen 20, the front surface of the touch panel 68 comprises a polarizer 82. The flexible cover 72 of the touch panel 68 comprises a substantially non-birefringent, flexible plastic material, such as polycarbonate (PC), triacetate cellulose (TAC), or polyvinyl alcohol (PVA). Since the cover 72 is

Referring to FIG. 2, the touch panel 92 of an alternative touch screen 90 incorporates a polarizer 94 (indicated by a bracket) comprising a polarizing element 95 supported by and bonded to a first surface of a flexible, non-glass, support layer 97. The support layer 97 comprises a non-birefringent material such as PVA that is bonded to the birefringent polarizing element 95 to form a polarizer 94 that can be substituted for the separate polarizer 82 and cover 72 utilized in touch panel 20. The polarizer 94 is attached to the front of the touch panel 92. The second surface of the support layer 97 proximate to the substrate 70 is coated with ITO to provide the electrical conductivity required for a resistive touch panel. The front surfaces of the polarizers 82 and 92 are typically coated with a material that reduces reflection and repels oil to minimize visual effects of finger touches.

Comparison of isocontrast plots for the output of an LCD display without a touch panel 120, see FIG. 5; the LCD equipped a resistive touch panel 122, see FIG. 6; and the LCD equipped with a resistive touch panel including a non- birefringent front cover 124, see FIG. 7, illustrate the improvement in contrast ratio (without image distortion) that can be achieved with the innovative LCD touch screen.

While the touch panels 68 and 92, including non-birefringent covers and front polarizers, substantially reduce the reflection of ambient light, extending the usefulness of LCD touch screens to environments with higher ambient light ( intensity, the touch screens have limited usefulness in outdoor applications. The plastic materials typically used in the manufacture of polarizers for LCDs and touch panels deteriorate when exposed to ultraviolet light. FIG. 8 illustrates a touch screen adapted for outdoor use comprising a capacitive touch panel 152

(indicated by a bracket), an LCD 154 (indicated by a bracket), and a plurality of additional components that can be arranged to provide exemplary touch screens 150 of alternate construction that are suitable for exposure to ultraviolet light and reduce reflection of ambient light. Capacitive touch panels are often used in outdoor applications because the touch panel can be sealed to prevent the entry of moisture or other contaminants. In addition, capacitive touch panels are typically constructed from glass panels that provide durability, resistance to scratches, and ultraviolet light (UV) protection for components underlying the glass panels of the touch panel. The LCD 154 comprises generally, a backlight 156 and a light valve 158

As illustrated in detail for the second polarizer 164 of the light valve 158, polarizers used in LCD construction typically comprise a polymer-based polarizing layer 168 that is sandwiched between a pair of carrier layers 170 and 172 that provide strength and durability to the polarizer. The carrier layer 170 typically comprise a birefringent material such as polyester and the carrier layer 172 is substantially non-birefringent. In alternative constructions of the reflection i resistant touch screen 150, the carrier layers 170 and 172 of the polarizers may comprise a substantially non-birefringent material, such as polycarbonate or triacetate cellulose (i.e., insubstantial x,y birefringence and some birefringence in the z-direction).

The capacitive touch panel 152 comprises a glass substrate 174 with a conductive coating 176 applied to the front surface of the substrate. The conductive patterned surface coating or wire mesh 176 is covered by a protective

coating layer 178. When the user contacts the protective coating layer 178, a change in the local capacitance occurs which may be measured by a change in the current drawn and/or the frequency response from the conductive layer. A controller (not illustrated) compares the current flow from a plurality of electrodes at the periphery of the conductive layer to determine the location of the user"s contact with the panel.

The protective coating layer 178 for the touch panel 152 may have a glare diffusing front surface 180. Glare is the result of reflection of light at an exposed surface. The reflection from an untreated polished surface is generally specular as in a reflection from a mirror. Typically, antiglare treatments roughen or coat the surface to create a texture that scatters the incident light and cause the reflection to be distributed over a large cone or diffused. Antiglare or glare diffusing surfaces also provide some protection from finger prints and similar surface contamination that may cause readability problems. Glare diffusing surfaces reduce the intensity of the reflected light that reaches the viewer"s eyes and is particularly effective in indoor applications where ambient light typically originates from several sources. On the other hand, under direct sunlight it may be relatively easy for a viewer 182 to avoid the intense specular reflection from a single source while the somewhat less intense, but diffuse reflection from a glare diffusing surface may be sufficient to cause readability problems.

To reduce the reflection of ambient light that transits the touch screen 152, the panel may also incorporate a polarizer 184 adjacent to the back surface of the touch panel 152. The polarizer 184 is protected from exposure to ultraviolet light by the glass of the touch panel substrate 174. The polarizer 184 comprises a polarizing layer 186 supported by a pair of carrier layers 188 and 190. The carrier layer 188 of the polarizer 184 may comprise either a birefringent material, such as polyester, or a substantially non-birefringent material, such as polycarbonate or triacetate cellulose, while the carrier layer 188 comprises a substantially non- birefringent material. Ambient light transiting the touch panel 152 comprises light vibrating in a plurality of planes. Since the polarizer 184 will only pass light

vibrating in the plane of its optical axis and absorb substantially all of the light vibrating in other planes, a substantial portion of the ambient light transiting the touch panel is absorbed at the polarizer 184. The optical axis of the polarizer 184 is aligned with the optical axis of the second polarizer 164 of the light valve 158 so that the polarized light comprising the image is transmitted through the polarizer 184 to the viewer 82 at the front of the touch screen display 150 with minimum attenuation.

To further reduce reflection of ambient light impinging on the front of the touch screen 152, the touch screen may include one or more anti-reflection panels 192, 194, and 196. A first anti-reflection panel 192 may be interposed between the touch panel 152 and the second polarizer 164 of the light valve. Typically, this anti-reflection panel 192 is adhered to the front surface of the second polarizer 164. A second anti-reflection panel 194 may also be interposed between the light valve 158 and the touch panel 152. The second anti-reflection panel 194 may be proximate to the back side of the glass substrate 174 or the touch panel polarizer 184, if the touch screen is so constructed. The first 192 and second 194 anti-reflection panels may comprise a film of substantially non- birefringent material, such as polycarbonate or triacetate cellulose, coated with an anti-reflection coating and in the case that a polarizer 184 is omitted may also be birefringent material. The anti-reflection coating shifts the relative phase of the light reflected by the upper and lower boundaries of the coating film by 90° so that the reflecting beams destructively interfere and are extinguished. A third anti- reflection