Research on the development of infrared touch interaction technology

1. Introduction

With the in-depth development of social informatization, home entertainment equipment has been increasingly moving towards digitalization and informatization. However, current digital entertainment equipment has problems such as complex and difficult human-computer interaction and not adapting to the operating habits of mainstream users, so the depth and breadth of popularization are greatly affected. Therefore, home digital entertainment terminals with powerful functions and intuitive operation methods have become an urgent need for users. The successful development of "Advanced Touch Interactive Digital High-Definition Flat-Panel TV Receiver" can not only meet the needs of users, but also open up a series of product markets related to touch control technology, becoming an emerging comprehensive media display control terminal product.

As an intuitive, simple and easy-to-understand human-computer interaction method, touch technology has been widely used. The combination of touch technology and digital high-definition flat-panel TV receivers not only meets the basic needs of users for watching high-definition digital TV programs, but also enables users to fully enjoy the various information functions of digital high-definition flat-panel TV receivers as an intuitive and easy-to-understand operation method. Such as: interactive games, information query, program on demand, surfing the Internet, sending and receiving emails, etc., thereby promoting the popularization of digital high-definition flat-panel TV receivers and the development of the entire flat-panel TV industry chain. In addition, because the visible area is much larger than that of traditional touch query machines, it has a more shocking display effect, flexible and changeable media forms, efficient and fast response capabilities, maintenance-free, long life, high stability and other advantages. It has been quickly recognized by the commercial, engineering and military industries, and the market demand is rapidly expanding.

In the early 1990s, with the rapid development of flat panel display technology and the rapid progress of multimedia information technology, a new human-computer interaction technology, touch interaction technology, emerged. With the development of the information society, the application of touch interaction technology has become more and more common. Globally, the average annual market growth rate exceeds 30%. With this technology, users can operate the host by simply tapping the icons or text on the display screen with their fingers, making human-computer interaction more straightforward. Therefore, this technology greatly facilitates users. The human-computer interaction form also breaks the framework of the previous keyboard and mouse mode, and realizes the operation more directly [1.2].

At present, there are about 20 known touch interaction technologies in the world, of which only a few have been perfected and developed by mainstream companies, forming complete product lines and sold globally. Other technologies are only occasionally adopted in a few environments because they do not have cost advantages or have not yet found a suitable mainstream market.

1) Resistive touch interaction technology (including four-wire, five-wire, six-wire, and eight-wire)

Resistive touch interactive technology uses two layers of highly transparent conductive film to form a touch screen, with supporting particles coated in the middle of the conductive film. When a finger is pressed on the touch screen, the conductive layers come into contact, the resistance changes, and voltage signals are generated in the X and Y directions to achieve coordinate detection.

Due to the surface coating of resistive touch interactive technology, the light transmittance and anti-riot performance are poor and it is easy to be damaged. It is suitable for small-size and low-power application fields, the most common of which are mobile phones, PDAs, etc.

2) Capacitive touch interaction technology

The surface of capacitive touch interactive technology is coated with a transparent metal oxide film. When voltage is applied to the four corners of the screen, a balanced electric field is formed on the screen. When the finger, as a conductor, touches the screen, it will absorb different currents from the four corners, and the magnitude of each current is related to the touch position. The control circuit can determine the touch position based on the difference in current.

Capacitive touch interaction technology is also a film-coated product, with poor light transmittance and anti-riot performance, and is easy to damage. At the same time, due to the different resistance values ​​of the users themselves, positioning drift will occur.

3) Sound wave touch interaction technology[3]

The acoustic wave touch interaction technology is composed of a touch screen glass body, an acoustic wave generator, reflective stripes and an acoustic wave receiver. The acoustic wave generator can send high-frequency acoustic waves across the screen surface. When a finger touches the screen surface, the acoustic waves are absorbed, and the coordinate position of the touch point is determined. Since the sound waves need to be absorbed, there is no response to hard objects.

Acoustic wave touch interaction technology is completely transparent. However, because the acoustic wave generator is easily damaged, the acoustic wave touch interaction technology market is positioned in the mid-range market (including the acoustic wave touch interaction technology manufactured by Elotouch, which has also had large-scale quality problems). At the same time, due to the complex process and extremely low yield rate in the current manufacturing of large-size touch products, it is unable to meet the needs of the currently rapidly growing large-size touch market.

4) Infrared touch interaction technology

Infrared touch interaction technology is based on the infrared scanning detection technology. Infrared transmitting tubes and receiving tubes form an infrared detection matrix grid on the screen surface. When an object enters this detection grid, it will block part of the infrared light to achieve coordinate position detection.

The infrared touch interactive technology is completely transparent and can even be operated without glass. It also has the characteristics of being riot-proof, waterproof, dust-proof, oil-proof, no coordinate drift, anti-light interference, no drift at all, can be touched by any object, has a wide temperature adaptability, and supports pressure axis response.

2. Development trend of infrared touch interaction technology

With the advent of the flat-panel display era, technologies such as flat-panel CRT displays, liquid crystals, and plasma displays have continued to mature and become popular. The advantages of infrared touch interaction technology based on the principle of flat-panel infrared scanning detection have become apparent, and the market advantages based on this have become increasingly obvious.

In terms of technical applicability, infrared touch interaction technology can fully meet the diversified needs of the touch product market today and in the next few years. In the touch interaction technology touch size range of 10.4 inches to 29 inches, infrared touch interaction technology products can fully replace the application of other types of touch interaction technology based on their own technical advantages.

In terms of the market, with the rapid development and popularization of flat display products, the infrared touch interactive technology product market will gain a unique market space that other technologies do not have, and the market demand will continue to expand. From the perspective of price advantage, infrared touch interactive technology has the characteristics of simple production process, low production cost, long service life, maintenance-free, and low maintenance cost. Especially when infrared touch interactive technology is applied to screens above 29 inches, it has absolute monopoly and exclusivity, and is bound to become the new favorite in the touch interactive technology market.

Infrared touch interactive technology has good wide temperature (-25°C ~ +80°C) characteristics and extremely wide size specifications (6.4 inches ~ 150 inches). It is also riot-proof, shock-proof, waterproof, dust-proof and anti-biochemical weapons. It has broad development space in major touch interactive technology application markets such as financial equipment, self-service equipment, POS, gaming equipment, industrial control, education and training, and military command. With the rapid development of flat-panel and large-size display technology and the rapid decline in the cost of infrared light-emitting tubes, infrared touch interactive technology has more and more advantages in both market and cost. It should be pointed out that with the growth of the 30~150-inch display market, only infrared touch interactive technology can fully cooperate with various display methods such as rear projection, front projection, and full transparency, and will occupy a dominant position in the large-size display market.

The first infrared touch interaction technology appeared in 1992, with a resolution of only 32×32. The first generation of infrared touch interaction technology had low resolution, was easily affected by environmental interference and malfunctioned, and required to be used in a certain light-shielded environment. Due to these limitations, infrared touch interaction technology once faded out of the market.

The second generation of infrared touch interactive technology was launched in 1994, with a resolution of 64×64, improved anti-light interference performance, and can adapt to most indoor environments. The third generation of infrared touch interactive technology was launched in 1997, with a resolution of 320×240, which can be used outdoors in non-direct sunlight environments; the fourth generation of infrared touch interactive technology was launched in 1998, which increased the resolution to 800×600. From the development history of infrared touch interactive technology, the main progress has been made in improving resolution and adapting to strong light interference environments, but it has basically not overcome the problems of short product life and easy drift of device characteristic parameters.

The fifth generation of infrared touch interaction technology recently launched not only increases the resolution to 1000×720, but also increases the resolution to 4096×4096 through interpolation. The anti-interference performance of strong light is improved to the point where it can be used even in direct sunlight. More importantly, it has made a substantial leap in product life and maintenance-free performance. The fifth generation of infrared touch technology adopts the guiding principle of redundant distribution of probability function devices, and its life span is greater than 7 years in a working environment. This means that when the matching display reaches the end of its life, the touch interaction module itself can still work normally.

The improvement in performance indicators of the fifth-generation infrared touch interaction technology has pushed the application of touch interaction interface display modules to a new level. For example, in the past, when the touch interaction interface display module tracked the movement trajectory of the finger, many strokes would be broken and it could not be used for Chinese character recognition. When tracking the movement trajectory of the finger, the fifth-generation infrared touch interaction technology can meet the requirements of accuracy, smoothness and tracking speed. The user's writing can be converted into an image trajectory very smoothly, fully supporting handwriting recognition input.

In fact, the fifth-generation infrared touch interaction technology can be used as a single device as a complete human-machine interface platform to replace the mouse, writing tablet and even keyboard. From the application level, touch interaction technology should not only be a simple device that converts touch position into coordinate information, but should be designed as a complete human-machine interface system. The fifth-generation infrared touch interaction technology is based on such standards, and realizes the improvement of product concepts through built-in processors and perfect driver software.

3. Haier Group’s achievements in touch interaction technology

With the in-depth development of social informatization, home entertainment equipment is also increasingly moving towards digitalization and informatization. Since my country first proposed the concept of flat-panel TVs in 2003, flat-panel TVs have been gradually understood and recognized by consumers at all levels of the market. At the same time, home digital entertainment terminals with powerful functions and intuitive operation methods will become an urgent need for users.

Unitop's infrared touch interaction technology has basically monopolized the domestic high-end touch interaction technology products, and has been used for a long time in the financial equipment, self-service equipment and other industries in the country with good feedback. Some other entrants have also appeared in the market, such as OneTouch and GeneralTouch, but due to insufficient technology and frequent instability in product applications, they cannot pose a substantial threat to Unitop in the short term.

The domestic mid-range touch interaction technology market has been basically monopolized by GeneralTouch (Sichuan Jirui)'s acoustic wave touch interaction technology, which is mainly used in the self-service equipment market. Recently, some other entrants have emerged, such as OneTouch and ConTouch, which have been cannibalizing GeneralTouch's market share by providing relatively similar products [4.5].

Haier Group's latest advanced touch-screen interactive digital high-definition flat-panel TV receiver has been quickly recognized by the commercial, engineering, and military industries for its flexible and diverse media formats, efficient and fast response capabilities, maintenance-free, long life, and high stability. It has been accepted by many key markets. It not only meets the needs of users, but also allows users to fully enjoy the various information functions of digital high-definition flat-panel TV receivers. Such as interactive games, information query, program on demand, web surfing, sending and receiving emails, etc. This will drive the popularization of digital high-definition flat-panel TV receivers and the improvement of the entire flat-panel TV industry chain. Compared with traditional flat-panel TVs, the advanced touch-screen interactive digital high-definition flat-panel TV receiver developed by Haier Group has the following advantages:

1) Intelligent adjustment, no light interference, high light transmittance, up to 100%

The revolutionary mechanical and optical design completely solves the defects of the previous infrared touch technology that cannot resist light interference or can only resist light interference within 30 degrees of the normal line. It has strong anti-light interference ability for sunlight at any angle and is fully adapted to outdoor work under strong sunlight. At the same time, there is no coating or film on the display interface surface, which can achieve glass-free operation, up to 100%

2) Touch detection technology with high performance and high reliability using pre-scan compensation technology

In terms of scanning detection, this technology uses a method of pre-detecting the emission and receiving sensitivity of infrared emitting and receiving tubes. It can be set to detect the emission efficiency and sensitivity of infrared emitting and receiving tubes once or several times before the equipment officially works, and then memorize the sensitivity of each pair of tubes. The circuit magnification is adjusted through the microcontroller system inside the touch screen to automatically adapt to the sensitivity of infrared emitting and receiving tubes to ensure the reliability of detection. Using this technology, even if the sensitivity of the tube drops to 1/4 to 1/3 of the original after a long period of use, it can still ensure reliable detection of touch operations, greatly improving the reliability of detection. For existing infrared touch screens, as long as the sensitivity of a pair of tubes drops to half of the original, they cannot be used normally. The curve of the emission efficiency reduction of infrared emitting tubes under high current impact is a curve close to a logarithmic curve, so the use of this technology can extend the service life of infrared touch screens by 3-5 times.

3) Modular bus drive technology

There are many technological limitations that need to be addressed for oversized touch screens. For example, there are many more infrared sensors than conventional ones. If the usual scanning technology of small size is used, not only will the scanning time be incredibly slow, but there will also be problems such as wiring of circuit boards in the narrow space around the display where the touch screen is installed, as well as assembly, maintenance, and transportation. At the same time, there are many sizes of 50-100-inch full-series displays, and there are different size specifications such as 4:3, 16:9, and even non-standard products. In this way, not only are the product development, production, and inventory costs amazing, but if each size product is developed separately, each product needs to undergo relevant testing and certification. The use of innovative universal module circuits, connected in series in bus mode, and using the building blocks method to design oversized touch screens of different sizes on a substrate that only needs to be equipped with a limited number of buses, greatly reduces the design difficulty and shortens the design cycle. It not only perfectly solves the above problems, but also reduces maintenance and repair costs.

4) Rapid response technology

An innovative method that can effectively improve the response speed of infrared touch screens is used. First, the entire touch screen area is scanned to detect whether there is a touch object; if a touch object is detected, the position of the touch object is calculated, and the position is used as a reference point to select several pairs of infrared transmitting and receiving tubes in front, behind, left and right of the touch object to set a new detection area smaller than the size of the entire touch screen and scan and detect the area; if a touch object is detected again in the set area, the above calculation and setting steps are repeated, or a detection area with the same size as the last time is set, or a new area with a smaller size is set to continue scanning and detecting the touch object. The above steps are repeated in a cycle. If a touch object is not detected in one of the above detections, the scanning and detection of the entire touch screen is restarted. Since this method reduces the actual detection scanning area, the response speed of the touch screen to touch operations is greatly improved, making the response speed of a touch screen of nearly 100 inches almost the same as that of a touch screen of more than ten inches, which is very suitable for large-sized infrared touch screens.

5) Multi-touch technology

An innovative patented technology is used to identify multiple touch points on the infrared touch screen. After the touch screen scan detects that more than one pair of transmitting and receiving tubes are blocked in the horizontal or vertical direction of the touch screen, this method stores the serial number or address of the blocked pair of tubes, and combines the detected vertical and horizontal coordinate values ​​to obtain multiple possible touch points. Then, the off-axis scanning method is used to eliminate pseudo touch points, thereby realizing multi-point touch detection. This method has two specific technical solutions, both of which have been applied for Chinese patents. Moreover, these two technical solutions do not change the structure of the existing infrared touch screen, and are both implemented through the software of the microprocessor, so they have the advantages of extremely low application cost and very wide applicability.

4. Conclusion

The flat panel display industry has become one of the fastest growing industries in the field of international trade. The new flat panel display technology is the key technical foundation for the next generation of mobile communications, the new generation of home appliances and 3C integrated products. It will be used in almost all electronic information products in the future and is the technical commanding height of the international information industry. Haier Group has a good foundation in developing international markets. The research and development and industrialization of advanced touch-screen interactive digital high-definition flat panel TV receivers will further highlight the industrial advantages of my country's touch-screen interactive digital high-definition flat panel TVs, and improve the technical level of electronic information products while continuously developing domestic and foreign markets; accelerate the formation of an excellent platform for the development of the flat panel display industry, undertake international technology transfer at a higher level, and carry out broader and deeper international cooperation.