For touch panels, big is beautiful. However, it is a challenge to achieve multi-touch and maintain good sensitivity and accuracy on a larger display and more demanding environments.
The "Global Touch Screen Market 2015" report of the business research company found that since 2009, projected capacitive touch (PCAP) technology has been widely used in a variety of touch phones and tablets. This successful model is derived from admirable product features, including unrestricted life from tempered glass, full-plane design capabilities and a high level of sensitivity. PCAP manufacturers are using this technology on large screens up to 85 inches in size, focusing on speed, accuracy, immunity to electromagnetic interference (EMI) and system integration in four directions to improve touch and user interface. Design performance.
Fast speed/precision, multi-touch with better interactive experience
On a typical consumer phone (approximately 4.5-inch diagonal screen), only one or two touch points can be recorded, while on a 47-inch diagonal commercial touch panel, ten to forty precisions are recorded. The situation of 1 mm touch points has become commonplace. When the diagonal length is doubled, the screen area of ​​the 16:9 format is four times that of the original. To maintain the same touch detection performance, the touch processor on the 47-inch screen has to handle more input signals than the 4.5-inch phone. At the same time, anti-missing, gesture recognition and other functions also increase the demand for touch processors.
Touch panel sizes continue to increase, however, in multi-player casino gaming tables, museum interactive exhibits, multi-user design workstations/construction workstations, retail store catalogs and EPOS tablets, car showrooms and bank branches, 55 Screens that are up to 85 inches in size are becoming popular. Providing a touch experience on a screen of this size means increasing the number of touch detection electrodes.
The latest in-body touch detection algorithm can double the number of touch detection electrodes, which supports 256, compared to 128 standard multi-touch controllers (for no more than The 47-inch screen) has doubled in number. The capacitance sensing matrix in the touch panel can achieve higher density, which enables it to be simultaneously touched even on the largest 85-inch touch panel based on multi-touch projected capacitive technology (MPCT). The identification of controlled events achieves greater precision.
This allows the touch controller to support forty simultaneous simultaneous touch events with a touch distance of less than 10 mm from each other and to do so in MPCT touch panels of all sizes available today.
To transfer data to a personal computer (PC) host without delay, the touch controller must have a lot of processing power. As a processor, the touch panel often becomes as important as the system itself. Due to the careful design of the firmware, additional information that must be captured on the large screen to achieve this level of performance can still be collected, processed and output to the host PC in less than 5 milliseconds.
4K screen touch delay problem has a solution
Ultra high resolution (UHD), the 4K screen, is becoming more popular and successfully integrates touch panels. However, some of the observed delays or delays are actually due to performance issues with earlier 4K screens, rather than performance issues with touch controllers.
Typical high-definition (HD) displays used today for touch panels have an update rate of approximately 120 Hertz (Hz). The data processing requirements necessary to control a very large amount of graphics data refer to the latest 4K display to operate at 60 or lower Hertz. This makes it challenging to handle instant touch events such as cursors on dragged screens, as the background image with display processing capabilities being updated consumes a lot of computing power.
Therefore, the mobile touch event on the UHD display is like drawing a line, and the ability to track the finger is more obvious than tracking the HD display. Even the PCAP screen that reports touch events in milliseconds is overwritten by this delay. This problem will be reduced as 4K displays with higher update rates enter the market. But before that, you must carefully consider the touch application running on UHD and its impact on the user experience.
Improve anti-electromagnetic interference and improve touch performance
Although electromagnetic interference is considered to be only one of the factors in the industrial environment of touch panel systems, in fact, in a wide variety of commercial applications, electromagnetic interference can adversely affect touch operations. For example, self-service kiosks such as self-service ticket vending machines and vending machines at train stations will be affected by the surge in electromagnetic interference from trains.
In particular, 4K displays currently generate higher electromagnetic interference due to the increasing complexity of drive circuits required to manage higher graphics densities. This can cause interference or "noise" in the display to be three to four times higher than in normal high definition (HD) displays. This can cause problems for the touch panel and control electronics from the surrounding noise recognition signal, which will reduce the signal to noise ratio and affect the identification of actual touch events.
In these cases, significant improvements must be made to the electronic design and touch detection firmware used in the touch controller to ensure a high level of integrity. For example, PCAP touch panel technology such as Zytronic's proprietary projected capacitive technology (PCT) has an XY coordinate matrix of fine electrodes embedded in a laminated glass substrate and uses frequency modulation to detect small capacitance changes in the conductive electrodes.
One method of eliminating electromagnetic interference is to implement a smart frequency scanning function in a touch controller. The operating frequency is dynamically floating between 0.7MHz and 2.2MHz to avoid detecting "noise" in the environment, which would otherwise hinder the detection of touch events.
New developments in materials/interfaces to drive the development of touch technology
Although the touch inquiry machine may be some large units, due to aesthetic considerations and other considerations that sometimes need to be included in the unit's spare parts, a small space is unexpectedly placed behind the screen. If the touch controller's board can be minimized, it will bring benefits. Therefore, it is important to reduce the PCB size so that the controller can be used as a chipset, and then the designer can embed the touch controller on the existing system board.
The four elements of the touch panel: touch sensor embedded in the screen, touch controller, glass and system interface.
Material technology makes the glass thin and light, but it is very strong. The latest development in glass is that the antibacterial elements on the glass surface will ensure that the bacteria will gradually disappear rather than increase. With the health concerns about the adhesion of bacteria to the glass, users will no doubt be more aware of the potential risks associated with using touch screens by others with poor hygiene.
In terms of system interface, a recent important development is the first release of an encrypted PIN touchscreen application that meets the payment card industry (PCI) security requirements. The application encrypts all PIN codes entered by the user on the touch panel interface, providing consumers with a safer way of operating on automated teller machines (ATMs), point-of-sale (POS) devices, and unattended payment terminal devices. This potentially eliminates the need for automated teller machines and similar devices to access a mechanical keyboard to enter a PIN code, which is beneficial in design.
Fundamentally, the key feature of PCAP touch panel technology such as PCT and MCPT is its high sensitivity. It detects touch events through thick cover films, protective glasses, and even thick-brushed hands, and therefore has Z-axis sensitivity and control. Plus a well-designed touch controller that delivers a reliable, intuitive touch experience that accurately responds to forty touch events, recognizes gestures and prevents accidental touch. The continuous improvement of the PCAP controller IC, coupled with the continuous development of sensors using printable conductive inks and nanomaterials, has driven the expansion and usability of multi-touch technology.
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