planar capacitive touch screen monitors free sample

2023-01-03 12:32:11

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planar capacitive touch screen monitors free sample

- Must contact Tyco Touch Inc’s RMA Dept. to obtain an RMA (Return Merchandise Authorization) number before returning the product. No return will be accepted without an RMA number issued by Tyco Touch Inc. Customer must request RMA number within 30 days of purchase.

- If the defective product is under warranty, Tyco Touch Inc. will repair or replace the product free of charge once an arrangement for return shipping by the customer has been made.

- Tyco Touch Inc. warrants its product against defects in functions, materials and workmanship for 1 full year. from the date of purchase. Normal wear and tear are not covered by the warranty. Select models may have longer warranties, see product for details. Longer warranties may be purchased for a small fee.

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planar capacitive touch screen monitors free sample

- If the defective product is under warranty, Tyco Touch Inc. will repair or replace the product free of charge once an arrangement for return shipping by the customer has been made.

planar capacitive touch screen monitors free sample

The Planar PT1701MU is 17" LCD Monitor features 3M® capacitive touch screen and USB touch screen driver for use in harsh environments that require a more rugged touch screen interface. The Planar PT1701MU features a bright and fast panel combined with a durable desk stand, and is compatible with mounting options using the 75mm VESA standard. The Planar PT1701MU includes Planar"s leading 3-Year CustomerFirst™ Warranty featuring FREE 2-Day Advance Replacement for three full years.

planar capacitive touch screen monitors free sample

Using projected capacitive technology, the Planar Helium PCT2435 registers up to 10 simultaneous touch points using either a finger or a passive stylus. With this interactive technology, the Planar Helium PCT2435 is extremely fast and accurate when browsing the web, scanning emails, editing photos or graphic design projects. The Planar Helium PCT2435 is designed to take full advantage of Microsoft Windows 10, which works seamlessly with multi-touch technology.

planar capacitive touch screen monitors free sample

Featuring Projected Capacitive touch technology for fast and accurate touch operation, the Planar PCT2235 touchscreen monitor is a value-for-money choice for productivity workloads. This 21.5" LED-backlit LCD monitor delivers vivid visuals with Full HD resolution and 1000:1 contrast ratio, and features two onboard speakers for convenient sound reproduction - without the need for external speakers. Three inputs, VGA, HDMI and DisplayPort, allow broad compatibility with various video sources. The thin black bezel makes the Planar PCT2235 ideal for multiple-monitor applications, while the blue light reduction presets vary blue light levels depending on the activity, enhancing visual comfort when viewing the screen for extended periods of time. You"ll also delight in the adjustable stand, which supports 15° to 70° tilt, or can be fully folded flat for tabletop use.

The Planar PCT2235 22” Full HD monitor with multi-touch interactivity is the best value for the money. Featuring Projected Capacitive touch technology which registers up to 10 simultaneous touch points, the monitor is extremely fast and accurate for the office workers when scanning through emails, or for the graphic designers when swiping through various design alternatives or resizing photos.

Blue light has a short wavelength and produces a higher amount of energy. Studies have shown that prolonged exposure to blue light could cause damage to your eyes. The Planar PCT2235 incorporates blue light reduction presets. Varying blue light levels depending on the activity enhances visual comfort when viewing the screen for extended periods of time.

The Planar Helium Stand can be easily tilted from 15° to 70° - quickly moving the user from passive viewing to full touch screen interaction. For the mobile worker desiring to dock their tablet to larger display when manipulating spreadsheets, or for the college student scrolling through social media updates, the versatile stand accommodates all usage scenarios. For added flexibility, the stand can be collapsed into the back of the monitor and laid flat for tabletop usage, for example, in a museum environment to further explain an exhibit.

For more integration flexibility, the Planar PCT2235 multi-touch monitor boasts multiple video inputs – DisplayPort, HDMI and VGA - and integrated speakers. And the VESA-compatible hole pattern on the back of the monitor makes it easy to attach to other mounting option, such as a Planar single-arm clamp stand or a height-adjust desk stand.

planar capacitive touch screen monitors free sample

The best touchscreen monitors can offer advantages for certain workflows. Whether it’s for creative use or to improve general productivity tasks, the best touchscreen displays can make navigating certain programs more intuitive and more precise, particularly for tasks like making a selection in an image.

They can deliver a seamless, responsive experience that feels like writing with a pen on paper, and an immediacy that you don"t get with even the best mice to the best keyboards. But while touch screens now abound in phones and tablet, most monitors don"t offer touch. There are some excellent touch displays out there, however.

Below, we"ve made our pick of the best touchscreen monitors after evaluating a range of options for their accuracy and responsiveness, design, extra features and price. From regular-sized displays ideal for a desktop PC to portable monitors for those on the road, these are the best touchscreen monitors we"ve found.

If you prefer a more traditional monitor, possibly with a higher resolution, check out guides to the best monitors for photo editing and the best 4K monitors. If accurate colours are important to you, whether you’re a photographer or video editor, you might want to invest in one of the best monitor calibrator tools.

With so many options on the market, our choice of the best touchscreen monitors comes down to the details. And detail is something that Dell"s P2418HT monitor does brilliantly. This 1080p monitor on a 23.8-inch panel boasts an LCD screen to deliver excellent resolution, contrast, and colour. Moreover, it boasts an anti-glare surface that works beautifully in distracting light conditions as well as ultra-thin bezels that give it a stylish flair and you more screen real estate.

Looking for a cheap touchscreen monitor from a reputable brand? The 21.5in Dell P2219H IPS monitor is available at a brilliant price, and it still does an impressive job, making it one of the best touchscreen monitors available for those on a tighter budget.

While creative professionals usually go for larger screens, there’s definitely a place for portable monitors in content creation. Nomadic users in particular can benefit from a portable monitor that’s designed specifically with video editors, designers, and music producers in mind.

The ProArt Display PA148CTV is something of a rarity in the sea of portable monitors with its robust set of features targeted towards creatives. They include the Asus Dial, a physical dial that you can use to make effortless adjustments to your project whether you’re in Lightroom, Premiere Pro, or Photoshop. There’s also the Virtual Control Panel function, which allows you to use the display itself as your touchscreen control panel, simplifying your workflow.

The ViewSonic TD2230 is small, light and portable touchscreen monitor, making it perfect for anyone with limited desk space and/or who needs to travel with their screen. The 22in, Full HD, IPS display offers beautifully sharp image quality and high visual accuracy. The screen is also scratch-poof, and the bookstand design allows it to be tilted and adjusted from 20 to 70 degrees, or rested flat.

The connection ports are all on the side of the monitor, offering easy access. You get HDMI, DisplayPort and VGA and USB connectivity. The monitor offers low power consumption – great for both your pocket and the planet. The colours are a little dull, but overall this is an excellent buy for anyone looking for a portable touchscreen monitor.

The Philips 242B9T is another good touchscreen monitor. It might not be the most stylish looking touch monitor but it has an awful lot to offer. For a start, it comes with built-in 2W speakers. Also, you can connect it to a wide range of devices via HDMI, DVI, VGA and DisplayPort.

The Asus VT229H comes with many features you’ll find on most touchscreen monitors, including 10-point multi-touch capacity, 178/178 viewing angles, flicker-free backlighting, and blue light filter to make it easy on the eyes. However, it also boasts a few extras you won’t find on rival displays, and these help make your workflow more seamless.

Want a larger touchscreen monitor? Most touchscreen monitors tend to be on the smaller side, but this 27in offering from Planar offers a relatively large IPS LED-backlit display. While Full HD is a little thin for a 27in display, the screen offers dependable color accuracy and contrast that won"t shift depending on where you"re looking.

It"s a versatile monitor too, with a built-in HD webcam and microphone, making it great for home office working and video conferencing. It boasts 10-point capacitive multi-touch and an ergonomic stand that can take the display from completely flat to a 70-degree tilt.Is it worth buying a touchscreen monitor?If you’ve ever used a touchscreen laptop and wished you could do the same at your desk, then the slightly higher price of a touchscreen monitor over its non-touch counterpart is well worth it. After all, there’s no other way to get that kind of nuanced control when navigating various windows and apps. For example, if you want to translate handwriting to text or draw directly on the screen using your finger, one of these panels is the way to do it. And, instead of having to use keyboard shortcuts to carry out a command, you can perform the actual action directly on the screen.

But, you won’t be holding a touchscreen display the way you would a tablet or smartphone. So, consider whether you’re comfortable using your fingers to navigate a screen that’s sitting at eye level for long periods.What are the disadvantages of a touchscreen monitor?There are some drawbacks to using a touchscreen monitor. For example, holding your arm up to interact with a touchscreen throughout a day’s worth of work will get tiring no matter how strong you are. And, you’ll have to clean that screen regularly. Otherwise, that buildup of smudges and fingerprints can get in the way of seeing it properly.

Most importantly, however, touchscreen displays are more likely to experience some kind of damage. This is because there’s much more going on under the hood than with non-touch monitors. And, when something goes wrong, it will cost more to fix due to the more complicated design of these panels.What is a 10-point touchscreen?A 10-point touchscreen can register 10 distinct points of contact all at once. Not all touchscreen devices and displays utilise this technology. But, having it makes a huge difference in the accuracy of your taps, swipes, and various gestures. With one or two-point touchscreens, any accidental contact like the edge of your palm grazing the screen could confuse the interface and register a tap where it shouldn’t be. Utilising a 10 point touchscreen largely eliminates that kind of accidental interaction. And, it also allows for more complex interactions like typing directly on the screen.Can I use a touch screen monitor with any computer?Yes, you can use a touch-sensitive screen with any PC, or even a laptop. provided it has the right ports to connect with your machine. Check what ports your device has, but most touchscreen monitors will have several, including USB and HDMI.

planar capacitive touch screen monitors free sample

Searching for the best and brightest large touch screen monitor for your office? Sounds like someone got an increase in their A/V budget. We’re not surprised, seeing as employee experience and self-service tech is a hot topic these days, with a 2017 Deloitte study stating that almost 80 percent of executives believe it’s important to very important. One way to improve employee experience is with transparency and visibility. Large-format touch screen displays showing interactive office maps in your lobby, kitchen, and elevator bay, for example, accomplish just that.

For the best-case scenario when employees interact with a large format touch screen display in your office, we recommend looking for these qualities to make for a quick, easy and accurate experience.

• Multi-touch vs single-touch:if you’re looking to use software that has zoom capabilities (like Robin interactive maps), you want to look for multi-touch displays. These could also be good for large-format displays where multiple people may be trying to click around, or if the software has any added multi-touch functionality (similar to Apple’s trackpad two-finger scroll or page flip motions).

• 5-wire resistive or infrared touch screens:Between the two, they cover the best circumstances for touch screen technology from transmissivity, type of object able to be used (stylus vs. finger), and more.There are technically five different types of touch screen technology, which you can read more about here.

We made a quick list of five the best touch screen options for your office lobbies and elevator bays. At Robin, we’ve tried out both Chromebase and Elo touch screen displays, both being solid options as they’re relatively easy to mount and setup. We also pulled some favorites from across the web.

Pros:Many format and size options, from seamless to matrixed video walls to simple large format touch screen displays. Includes infrared and multi-touch options.Cons:They seem to be expensive (but, you get what you pay for, if you’re looking for a 70” display or an entire wall)

You’re in luck. A fair amount of the larger format touch screen technology we’ve seen works with a standard TV. Seems like the industry recognizes it’s worth reusing a standard TV and simply making it touch-enabled with an overlay “frame” of sorts. Here are a ton of size options for infrared, multi-touch overlays from OPTIR via Tyco Touch.

An ideal office scenario would be to have a large-format touch screen monitor in your lobby and on each floor in the elevator bay or kitchen areas. These are often the highest-trafficked collision points in an office and therefore the places where employees would greatly benefit from seeing an interactive map and schedule of the workplace.

As your company grows, you’ll want to keep up the pace of strong internal communications and visibility. Large-format displays, especially touch screen ones, help you accomplish this objective really easily.

From wayfinding and conference room booking to internal communications of all types, having touch screens in high-traffic locations will make you look like the office admin superstar you really are. You could welcome new hires, tell everyone about a new product, or roll out a brand new software tool (like Robin) via these screens.

planar capacitive touch screen monitors free sample

Touchscreens have been studied and developed for a long time to provide user-friendly and intuitive interfaces on displays. This paper describes the touchscreen technologies in four categories of resistive, capacitive, acoustic wave, and optical methods. Then, it addresses the main studies of SNR improvement and stylus support on the capacitive touchscreens that have been widely adopted in most consumer electronics such as smartphones, tablet PCs, and notebook PCs. In addition, the machine learning approaches for capacitive touchscreens are explained in four applications of user identification/authentication, gesture detection, accuracy improvement, and input discrimination.

Human beings collect a lot of information through their eyes, and many displays around us play a key role to transfer this visual information. Displays have evolved dramatically from cathode-ray tube (CRT) [1,2,3,4] via plasma display panel (PDP) [5,6,7,8,9,10] and liquid crystal display (LCD) [11,12,13,14,15] to cutting-edge organic light-emitting diode (OLED) [16,17,18,19,20,21,22] and micro-LED technologies [23,24,25,26,27,28]. This evolution has led to larger screen-size, slimmer design, lower weight, higher resolution, faster frame rate, brighter luminance, wider color gamut, longer life time, and lower power consumption in the large-size display applications such as monitors, televisions (TVs), and digital signage [29,30,31,32,33,34,35,36,37,38,39]. The resolutions of off-the-shelf displays have increased up to 8K (7680 × 4320) along with the high frame rate of 120 Hz and the larger screen sizes than 55-inch have taken more than 30% of overall TV set sales [40,41]. Even rollable OLED TVs were demonstrated in the consumer electronics show 2018 (CES2018) [42]. On the other side of the small-size display applications, higher density of pixels, narrower bezel, flexibility, bendability, rollability, and low power consumption have been achieved along with enhanced picture quality [43,44,45,46,47,48]. The latest smartphones contain the bezel-less screens of larger pixel densities than 450 pixel per inch (ppi) and smartphones with foldable displays are being sold on the market [49]. Recently, as augmented reality and virtual reality (AR/VR) attract substantial interest, the demand for high-performance near-eye displays is increasing further [50,51,52,53,54,55,56,57]. Consequently, the very high resolution OLED on silicon (OLEDoS) displays up to 4410 ppi have been reported [58,59,60,61,62,63].

On top of the role of a visual information provider, displays have supported the interaction with users by means of various user interfaces. Users can adjust the visual information on the screen by themselves. The very old but still popular representative user interfaces are mouse and keyboard [64,65,66]. There have also existed pen tablets for more elaborate works such as drawing and writing [67,68,69,70]. Because these devices work on the different planes separated from displays, additional markers such as cursors and pointers are needed. On the other hand, more intuitive input interfaces called touchscreens have been studied to directly interact with displays by touching displays [71,72,73,74]. Touchscreen technologies can be categorized into finger-touch and stylus-touch methods. While finger-touch methods include resistive, capacitive, acoustic wave, and optical approaches [75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,101], stylus-touch ones cover up to electromagnetic resonance (EMR) schemes including finger-touch methodologies [102,103,104,105,106,107,108]. Recently, as wearable devices such as smartwatches and smartbands are becoming more popular, small-size displays are becoming further widespread with touch sensing functionality. However, because this very small-area screen cannot support multiple finger-touches and the whole area is covered even by a single finger, a variety of separate input modalities in the outside of the screen have been studied by using infrared (IR) line sensors, microphones, gaze trackers, IR proximity sensors, electric field sensors, deformation sensors, magnetic field sensors, and mechanical interfaces [109,110,111,112,113,114,115,116,117,118,119,120,121,122,123]. In addition, some approaches have coped with the limitation of the single touch by differentiating palm and finger or identifying pad, nail, tip, and knuckle of a finger [124,125]. Especially, because AR/VR displays are placed near to eyes, it is impossible to touch the screen directly. Therefore, other input tools using various sensors such as leap motion sensors, electromyograph sensors, inertial measurement units, eye-trackers, IR facial gesture sensors, cameras, and axis-tilt sensors, have been employed [126,127,128,129,130,131,132,133,134].

There have been also efforts to integrate machine learning (ML) approaches into touchscreen technologies. These ML networks are employed to add extra input tools, to improve the touch-sensing performance, to support the user identification/authentication, to discriminate finger-touches from others, and to capture the gestures [135,136,137,138,139,140,141,142,143,144,145,146,147,148,149,150,151,152,153,154,155,156,157,158,159,160,161,162,163,164].

There have been brief reviews of touchscreen technologies [76,96]. Walker [165] published many overview papers about a variety of touchscreen technologies from resistive to optical and electromagnetic resonance (EMR) stylus schemes. Those papers explained their histories, principles of operation, pros and cons, and applications. However, the technological details have not been handled such as algorithms, driving circuits, and ML approaches. Kwon et al. [166] reviewed capacitive touchscreen technologies including sensors, driving circuits, sensing methods, and stylus schemes in more detail. However, ML approaches were not introduced. Bello et al. [164] summarized ML approaches to improve security on touchscreen devices without addressing the touchscreen technologies. A variety of ML applications only for the security issues were addressed. This paper provides a unified and broader view of the touchscreen technologies with the detailed explanation and ML approaches in various scenarios.

The contributions of this paper are as follows:Providing the most comprehensive review about the touchscreen technologies. In particular, this describes various studies on sensing methods and ML approaches.

This paper is organized as follows. Section 2 addresses the overview of the touchscreen technologies, and then Section 3 describes various studies on capacitive touchscreen applications that are integrated in most smartphone and notebook displays. Section 4 shows the ML approaches working with existing capacitive touchscreen technologies. Section 5 concludes this paper with some suggestions of the future directions.

In this section, touchscreen technologies for finger as well as stylus have been simply addressed in terms of principles of operation, advantages, and drawbacks. We categorize the touchscreen technologies into four categories of resistive, capacitive, acoustic wave, and optical, and address further various techniques in each category as shown in Figure 1. Table 1 compares their specifications.

An analog resistive scheme is the oldest touchscreen technology [165]. It extracts touch coordinates by sampling the voltage at the touched area. The voltage is proportional to the location of the screen due to the voltage division based on the ratio of resistances from the current position to two opposite sides [78]. The most popular resistive touchscreen panels are fabricated by 4-wire and 5-wire architectures [79]. Both methods estimate x-axis and y-axis coordinates of a touch position sequentially. Normally, two separate layers are coated by the conductive films only at one side, and one layer should be composed of a flexible material. When the touch force is applied, the flexible layer is pressed to contact the other layer and to obtain the voltage at the contacted area. Four-wire structures use both layers to generate the voltage slopes as well as to sense the voltage as illustrated in Figure 2a. For example, after the flexible layer (Layer #1) generates the voltage slope at an x-axis and the other (Layer #2) senses the voltage, Layer #2 generates the voltage slope at an y-axis and Layer #1 senses the voltage. Five-wire ones apply voltages only to one specific layer (Layer #2) and use the other layer (Layer #1) only to sense the voltage as depicted in Figure 2b. Therefore, it is known that 5-wire schemes usually have a longer life time.

The advantages of the resistive touchscreen technology are to be able to work with anything, to be fabricated at the lowest cost, to be insensitive to any contaminants, and to consume low power. However, it has drawbacks of the only single touch support, the poor durability due to scratches, poking, and sharp objects, the poor optical clarity, and the relatively high touch force requirement [80,165].

On the other hand, there have been efforts to support multi-touch capability. Some researchers were trying to add the multi-touch functionality to a conventional structure by sensing the current consumption at voltage sources [167,168,169]. Whereas, other researchers divide the conductive films into multiple lines and columns that give rise to many separate overlapped areas [170,171,172], where each area can detect touches separately. This scheme is named as the digital resistive touchscreen [165]. Since the resistive touchscreen methods fall short of the capacitive schemes, the resistive touchscreen panels are being applied to the limited areas such as toys, office electronics, and card payment machines.

Capacitive touchscreens sense the change of the capacitance caused by the finger to estimate the touch position. While resistive schemes need the pressing force to make the actual contact between two conductive layers, capacitive methods can obtain the capacitance change just by the light touch on the screen. Consequently, it enables the smooth and fast scrolling, high durability, and excellent optical performance. In addition, any materials can be adopted for layers, for example, glasses and plastics, while resistive technologies require one flexible layer at least. Because the parasitic capacitance added by fingers is very small, large-size capacitive touchscreen panels are very difficult to implement and contaminants such as water and dusts can be also recognized as touches. Recently, the large size capacitive touchscreens have been reported based on the metal mesh structure [108,173]. It can support only capacitive input tools including fingers to make parasitic capacitors with electrodes of the touchscreen panel.

The capacitive scheme is divided into surface-capacitive [81,83] and projected-capacitive methods [82,84]. Surface-capacitive touchscreens consist of one conductive layer of which four corners are connected to four perfectly synchronized alternative current (AC) voltage signals as described in Figure 3. While any difference does not occur without touches at these voltage sources, the finger touching the screen brings out the current difference in four voltage sources. As the voltage source is located nearer to the touch point, the current variation becomes larger due to the smaller resistive load. As a result, the touch locations are extracted from the ratio of the currents over four voltage sources. Even though it cannot deal with multiple touches at the same time, its high durability enables the integration in automated teller machines (ATMs).

Surface-capacitive touchscreen. The touch location can be estimated from the current variation at four corner AC voltage sources caused by the finger touch.

The projected-capacitive methods can be further divided into self-capacitance and mutual capacitance architectures. Especially, the mutual capacitance has been the mainstream technology used in most consumer electronics such as smartphones, tablet PCs, and notebook PCs since the appearance of iPhones in 2007, because it can support multi-touch functions along with high durability and good optical clarity.

In general, the projected-capacitive touchscreen panels use two patterned conductive layers that are separated and crossed to each other in the shape of a matrix. Horizontal and vertical patterns correspond to the position information of the touch event. While the self-capacitance senses the capacitance between layers and ground as shown in Figure 4a, the mutual capacitance measures the capacitance at the overlapped areas of horizontal and vertical patterns as presented in Figure 4b. Consequently, the finger touch increases the self-capacitance due to the additional parasitic capacitor in parallel and decreases the mutual capacitance due to the electric field loss by the finger placed between two electrodes.

The self-capacitance estimates x-axis and y-axis coordinates sequentially by measuring the capacitance of vertical and horizontal electrodes over the ground, respectively. Consequently, the multiple touches may cause ghost touches. For example, when there are two touches at locations of (x1, y1) and (x2, y2), the self-capacitance can figure out that there are touches at x1, x2, y1, and y2, separately, and then it provides two correct locations of (x1, y1) and (x2, y2) along with two additional ghost locations of (x1, y2) and (x2, y1) by four possible combinations of two x-axis data and two y-axis data. Thus, the self-capacitance has difficulty to support multi-touch functionality. To cope with this ghost touch issue, some panel makers use separate self-capacitance cells directly connected to the touchscreen controller that senses each capacitance variation, respectively, [174]. This approach has been implemented in the off-the-shelf smartphones.

On the other hand, because the mutual capacitance measures the overlap capacitance separately between vertical and horizontal conductive patterns, it can support multi-touch functions without any limits on the number of fingers. Therefore, it has become the widely used touchscreen technology today. The excitation pulses are applied to horizontal patterns and the transferred charges are measured through charge amplifiers at the ends of the vertical patterns. Since the amount of transferred charges is proportional to the mutual capacitance, the variation of capacitance can be detected. Section 3 will address the mutual capacitance approaches in more details.

While additional touchscreen panels on the displays require further electronics, the embedded touchscreen solutions that are called an in-cell touch can merge panel and touchscreen electronics into a single driver integrated circuit. Therefore, various in-cell approaches have been developed including self-capacitance cells and capacitive sensors embedded in pixel areas [174,175,176,177,178,179].

The acoustic wave scheme is composed of a wave guide, sound wave sources, and receivers. The well-known technology is a surface acoustic wave (SAW) touchscreen as depicted in Figure 5 [85,86,87,91]. The SAW contains two pairs of ultrasonic transmitters and receivers to calculate x-axis and y-axis coordinates of touch locations, respectively. The reflectors in the bezel area generate multiple horizontal and vertical acoustic wave paths that have different arrival times at receivers. When a finger is placed in a certain path, the signals attenuated by that touch arrive at the receiver with corresponding delays that are converted into the position coordinates. Because the SAW needs only one wave guide layer, it has the most excellent optical performance. In addition, large size touchscreen and high durability are achievable. However, its sequential estimation of x-axis and y-axis coordinates gives rise to the same ghost touches as the self-capacitance method. It can also detect some input tools of soft materials to absorb waves and the sensing performance is sensitive to contaminants on the screen.

Surface acoustic wave (SAW) touchscreen. The ultrasonic waves move through multiple horizontal and vertical paths. The finger touch attenuates the received signal strength in the contacted wave paths and their delay information is converted to the touch locations.

The another one is a bending wave scheme, where the sound wave caused by tapping on the screen is used as the sound source as well as the touch signal [88,89,90]. There are two methods of acoustic pulse recognition (APR) and dispersive signal technology (DST) [180]. The APR senses the bending waves by multiple piezoelectric transducers and processes them with the data stored in the memory to extract the touch positions. Therefore, the APR needs a prior process to sample and store the large amount of bending wave data at enough number of positions over the screen. However, because the bending wave characteristics are not deterministic, the resultant coordinates have some variance, leading to errors on the location estimation. Furthermore, the enough bending wave strength is required for the sensors to detect. The bending wave characteristics are dependent of the mounting structure and material. Since too large an amount of data is necessary for multi-touch cases, it supports only a single-touch input.

To cope with the requirement of the prior process to store the bending wave data in the APR, the DST extracts touch locations directly only from the measured bending wave data. Because the signal delay is affected by its frequency, the measured time and frequency information is used to reconstruct the bending wave pattern on the screen, which is converted to the touch coordinates. However, it also has several drawbacks such as only single touch support, high tapping strength, measurement variance, mounting dependency, as well as high computational power. In addition, both APR and DST cannot support the holding function because only the tapping action generates the sound waves.

The optical touchscreens are developed based on the invisible infrared (IR). The traditional IR-based touchscreen places transmitters at two sides and receivers at their opposite sides without any additional layers. Because the touches block the light path over the screen between a pair of transmitter and receiver, x-axis and y-axis coordinates can be obtained by finding the receivers’ positions that do not receive IR. While large-size displays and excellent optical clarity can be supported, the bezel needs some height over the screen for IR transmitters and receivers and the multiple touches cause the ghost touch issue.

The other IR-based schemes such as planar scatter detection (PSD) [100,101] and frustrated total internal reflection (FTIR) [75,95,98,99] are similar to the acoustic wave approaches except for the use of IR instead of the sound wave. In the PSD, while the transmitters send the IR lights through the wave guide at the total internal reflection (TIR) condition, receivers sense them. When any touches are applied on the wave guide plate, it breaks the TIR condition out, therefore, the scattered and remaining TIR lights arrive at multiple receivers as described in Figure 6a, leading to the extraction of the touch location by the complex analysis. The PSD can support multi-touch and high image clarity, but the larger-size touchscreens require higher computational power to extract the touch location. The FTIR also makes use of the TIR condition, but the touch location is attained from the lights escaped toward the opposite plane to the touched one as depicted in Figure 6b. Those lights are captured by the external camera or vision sensors and the resultant images provide the information of touch locations. There also exist the embedded LCD solutions, where IR transmitters are allocated in the backlight and the vision sensors are placed in the pixel areas.

As explained in the previous section, there have exist various touchscreen technologies by means of resistance, capacitance, sound wave, and IR. Among them, the capacitive touchscreen has become a mainstream scheme, especially, the mutual capacitance touchscreen is the most widely used technology on many consumer electronics such as smartphones, notebook PCs, tablet PCs, and smartwatches, because of its multi-touch support, slim form factor, high optical quality, excellent durability, smooth scrolling, and so on. Particularly, this section addresses the mutual capacitance capacitive touchscreens in more details. Unlike the self-capacitance method where the parasitic capacitor of a finger touch is connected to the self-capacitor in parallel, the mutual capacitance scheme experiences the capacitance reduced by electric field leakages into a finger. As a result, the touch location can be found out by searching the position which mutual capacitance is reduced.

As shown in Figure 7, a conventional mutual capacitance capacitive touchscreen panel is composed of excitation (EX) electrodes and sensing (SE) electrodes, which give rise to the mutual capacitor array at their intersection areas [181,182]. Excitation drivers generate EX pulses sequentially in the way of line-by-line that arrive at charge amplifiers attached to SE lines through mutual capacitors. The non-inverting input terminals of these charge amplifiers are connected to the reference voltage (VREF) and the charge transferred through a mutual capacitor (Cm) is converted through a feedback capacitor (Cf) into analog voltages (VOUT) that are proportional to the mutual capacitance as presented in Equation (1). VEX is the amplitude of the EX pulse. When a user touches on the screen with a finger, the reduction on the mutual capacitance is sensed as the different output voltage of the charge amplifier from the voltage level obtained without any touches as illustrated in Figure 8. To improve the precision of the touch detection, the transferred charge is accumulated at the charge amplifiers over multiple EX pulses. In addition, a multiplexer (MUX) allows one analog-to-digital converter (ADC) to sample the output voltages of charge amplifiers in all SE lines sequentially. Finally, a host processor handles the digital data to determine the touch locations and it also controls excitation drivers.

Block diagram of a conventional mutual capacitance capacitive touchscreen system. NEX and NSE are the numbers of excitation and sensing electrodes, respectively. The touch locations are estimated from the mutual capacitor array formed at the intersection areas of EX and SE lines.

Yang et al. [189] employed the differential-ended charge amplifier with two out-of-phase excitation pulses (EX, EXb) as depicted in Figure 10. With the single-ended amplifier, the output dynamic range (DR) is limited by the default mutual capacitance without touches. However, the proposed differential structure reflected only the difference of the mutual capacitance (Cm) over the adjacent line’s capacitor on the output voltages. In addition, the differential-ended amplifier gave rise to the doubled DR by non-inverting and inverting outputs (Voutp, Voutn). Therefore, the increased signal power led to the improved SNR performance.

Kim et al. [190] proposed the common-mode noise cancellation by subtracting the signals of the adjacent EX lines. Since the parasitic capacitance between neighboring EX lines of a touchscreen panel and display panel are almost equal, the injected noises from the display to the touchscreen would be similar, therefore, the differential sensing method over EX pulses of two neighboring lines could eliminate the common-mode display noise. Yang et al. [191] added a charge-interpolation filtered-delta-integration (CI-FDI) scheme to cancel the charger noise. The large noise is detected, and then the noise is prevented by the charge-interpolation.

As the other method to reduce the display noise components, it was proposed that the sensing operation was conducted only during the vertical blank interval as presented in Figure 11a. However, the sensing operation over the whole touchscreen area should be finished within very short period of time at the end of a frame time. Since it could not support smooth scrolling motions, the time division multiple sensing (TDMS) was introduced to spread the touch sensing functions evenly over a frame time [174,192], where the divided vertical blank parts were added in the middle of the active interval by stopping the scanning operations as illustrated in Figure 11b.

Touch sensing methods during the vertical blank periods. (a) Sensing during one vertical blank period. (b) TDMS sensing during divided vertical blank periods in the middle of a frame.

Miura et al. [193] adopted a two-step dual-mode scheme that performed self- as well as mutual-capacitance measurements. After the self-capacitance measurement found the touched areas, the mutual-capacitance measurement provided the fine touch location over the touched areas. Therefore, it achieved the high resolution of 80 × 80 and the high scan rate of 322 Hz.

An output accumulation sensing method can improve the SNR by applying multiple EX pulses per one touch position estimation, but lowers the scan rate inevitably. To improve SNR as well as scan rate simultaneously, Shin et al. [194] implemented a code-division multiple-sensing (CDMS) method. While multiple EX pulses per one EX line are used for sensing one touch position like the output accumulation sensing method, multiple EX electrodes are excited with orthogonal patterns simultaneously as illustrated in Figure 12. Then, the touch information over multiple positions was obtained at the same time through the decoding process. As a result, the CDMS method achieves a much higher scan rate without the SNR degradation [195,196].

Code division multiple sensing. CDMS enables the multiple capacitance sensing at the same time by transmitting orthogonal codes through multiple EX lines. The charge amplifiers’ outputs are demodulated and converted into digital data that are decoded as multiple simultaneous touch locations.

Park et al. [197] used the delta-sigma modulator in the ADC to move the low frequency noise to the high frequency region as shown in Figure 13. By applying a low-pass filter to remove the high frequency noise components, the noise power within the touch signal band was substantially reduced, leading to the improved SNR performance.

An et al. [108] introduced the multiple-frequency driving scheme. A fast Fourier transform (FFT) was applied to find the touch locations because EX pulses had different frequencies for each EX line, that is, the number of EX frequencies is equal to the number of EX lines. Furthermore, a spectrum of external noises was acquired, and then the frequencies of EX signals were located in the low noise region for the high SNR. However, in order to implement the FFT functionality, EX signals must be driven at a very high frequency for the large number of EX lines, which leads to the increased power consumption and hardware complexity. In addition, An et al. [198] integrated the amplitude-modulation to the multiple-frequency driving scheme to reduce the charge-overflow. The excitation pulses were amplitude-modulated to reduce their amplitudes with the same periodicity. It achieved 33.9 dB charge-overflow reduction, leading to the high SNR performance.

Handwriting and drawing applications on touchscreens require more elaborate input tools than a finger. The representative input tool is a stylus that has the shape of a pen. The simplest stylus implementation called a passive stylus is based on the conductive tip that imitates a finger touch as depicted in Figure 14a [103]. However, since the contact area must be large enough to be comparable to that of a finger, it is not adequate to elaborate works. In addition, it cannot support smooth scrolling and high durability due to its rubber-type tip. Additionally, the passive stylus is not distinguished from a finger. Lin et al. [199] showed that the pressure level could be sensed in the passive stylus due to the contact area change of the deformable head proportional to the pressing force.

Active stylus schemes have been introduced to support elaborate works even with small-sized tips as illustrated in Figure 14b. The early active stylus [105] senses EX pulses from the touchscreen and transmits its inverted and boosted pulses back to the touchscreen via a tip. As these inverted pulses reduce the amount of charges transferred to the charge amplifiers, the resultant outputs of charge amplifiers become equivalent to the voltage levels caused by the reduced mutual capacitance. The process of amplifying the sensed EX signal allows for the use of much smaller radius tips than the passive stylus.

If larger inverted pulses are applied to the tip, the different output voltage from finger-touch as well as no-touch will be obtained at charge amplifiers, which enables the stylus differentiation from the finger [106]. However, this scheme needs much higher voltage amplification at stylus circuits than EX pulses of the touchscreen to give rise to the additional voltage level required for the stylus discrimination. It reduces both dynamic range and SNR for the finger-touch detection when the ADC has the fixed input voltage range. In addition, the boosted voltage levels should be separately adjusted in accordance with touchscreens.

An et al. [108] introduced the other active stylus based on the multiple-frequency driving scheme as presented in Figure 15. It could distinguish the stylus from the finger, because tip pulses of the stylus had different frequencies from EX pulses of the touchscreen. Even though it can achieve the high SNR, it required the high computational power due to the FFT implementation. Its stylus supported pressure and tilt sensing functions by means of additional force gauge and gyro sensor.

Multiple-frequency driving touchscreen scheme based on an FFT processor. EX lines as well as stylus can be discriminated in the frequency domain at the same time by assigning different frequencies.

Lee et al. [187] proposed an electrically coupled resonance (ECR) stylus. As depicted in Figure 16, when the excitation pulse is asserted, the pulse is transferred to an LC resonance circuit of inductor (LST) and capacitor (CPR) in the ECR stylus and the signal of the resonance frequency is transmitted from the tip of the stylus to the touch sensing circuits. Since the ECR stylus consists of only passive elements, it does not need any batteries. In addition, the finger touch can be differentiated from the stylus. Because CPR is modified by the pressure, the pressure level can be differentiated by the resonance frequency. However, the large excitation pulse amplitude is necessary to generate the resonance pulse signals that can be detected at the touch sensor circuits. Besides, the frequency detection requires the increased hardware complexity.

Seol et al. [157,163] adopted the active stylus scheme that used the higher frequency pulses to generate different patterns from EX pulses for the finger-touch detection. It discriminated stylus-touches from no-touches and finger-touches without the high complicated FFT functionality by machine-learning-based classifiers as depicted in Figure 17. It also showed that the proposed method allowed for the effective data communication between touchscreens and styli. On the other hand, since the patterns of stylus-touches were placed in between finger-touches and no-touches, the achieved SNR was relatively low compared to the state-of-the-art high SNR touchscreen technologies.

ML-based touchscreen scheme. The higher frequency pulses of a stylus generate the different sequence from finger-touch and no-touch, and three touches are discriminated by ML-based classifiers.

While previous passive and active ways are grounded in the capacitive touchscreen panel, there is a stylus with a different approach that works with an electro-magnetic resonance (EMR) technology [107]. Since EMR responds only to the stylus and the capacitive touchscreen panel senses only the fingers, two separate touch sensing schemes enable the finger to be distinguished from the stylus. However, this technique needs additional layers that increase hardware complexity as well as manufacturing cost.

The stylus technologies that can be implemented on the capacitive touchscreen are summarized in Table 3 in terms of tip size, stylus discrimination support, SNR degradation, computational cost, and hardware complexity.

Several ML algorithms have been employed to the capacitive touchscreen in a variety of applications such as user identification/authentication, gesture detection, accuracy improvement, and input discrimination. While many approaches used traditional ML techniques of decision tree (DT), random forest (RF), naive Bayes (NB), radial basis function network (RBFN), back propagation neural network (BPNN), support vector machine (SVM), and Gaussian process regression (GPR), the latest ML networks, such as convolutional neural network (CNN), anomaly detection (AD), and recurrent neural network (RNN), have been also utilized in the touchscreen field. The following machine learning applications are implemented on the off-the-shelf smartphones and tablet PCs with mutual capacitance capacitive touchscreens.

The user identification and authentication is the most active field to apply the machine learning to the touchscreen because the touch behaviors are different according to the users. Kolly et al. [135] used DT, RF, and NB classifiers over touch gestures for the user authentication application. Mean and maximal pressures, the point in the time at the maximal pressure event, minimal and maximal gradients of the pressure, the hold time, mean x-axis and y-axis positions, and the variances in x-axis and y-axis directions were employed as input features that were crowdsourced by designing a quiz game. The resultant identification accuracy for five users was 80% or more. It also proposed the anomaly detection for the user authentication based on the learned distribution of features from 5 button touch events. The equal error rate of false reject ratio (FRR) and false accept ratio (FAR) was estimated as about 30%.

Feng et al. [138] proposed a finger-gesture authentication system using touchscreen (FAST). FAST collected touch gesture information including gesture type, x-axis and y-axis coordinates, directions of the finger motion, finger motion speed, pressure, and the distance between multi-touch points. Totally 53 features for each gesture and six gestures of down to up swipe, up to down swipe, left to right swipe, right to left swipe, zoom-in and zoom-out were put into DT, RF, and NB classifiers. It achieved FAR of 4.66% and FRR of 0.13% for the continuous post-login user authentication.

For the user authentication, Meng et al. [139] constructed 21 features such as average touch movement speeds for eight directions, fractions of touch movements for eight directions, average single-touch time, average multi-touch time, number of touch movements per session, number of single-touch events per session, and number of multi-touch events per session. They evaluated the performance of DT, NB, Kstar, RBFN, and BPNN, leading to the conclusion that RBFN showed the best performance with FAR and FRR of 7.08% and 8.34%. In addition, the particle swarm optimization (PSO) with a RBFN classifier reduced FAR and FRR further to 2.5% and 3.34%, respectively.

Saravanan et al. [140] proposed the authentication scheme based on the user’s touch interaction with common user interface elements such as buttons, checkboxes, and sliders. Using SVM and RF, they achieved average accuracies of 97.9% and 96.79% with mobile phone and tablet PC, respectively.

Guo et al. [143] proposed CapAuth that is a user identification and authentication technique based on capacitive touchscreen data combined with machine learning classifiers. It used the capacitive image of the hands-flat pose revealing the more distinguishing features. CapAuth was built based on quadratic-kernel SVM classifiers, a binary classifier for authentication and a multi-class one-to-one classifier for identification. The measure FRR and FAR for authenticat

planar capacitive touch screen monitors free sample

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