The optical touch is at the top two corners of the touch screen, and the two cameras (the blue squares shown in the figure below) respectively emit light, which is reflected by the surrounding reflective bars and passed to each other. In this way, the light is interwoven into a light net on the touch screen. When touching the touch screen, it will block the light at that point, and the emitted light and the received light form two angles with the horizontal line at the top of the touch screen. The length of the touch screen is set, and the coordinates of the touch point can be calculated and reacted through simple geometric knowledge.

Infrared touch is to use the infrared matrix in the horizontal and vertical directions to detect and locate the user's touch. There are infrared receiving tubes and infrared emitting tubes distributed around the infrared touch screen. They are arranged in a one-to-one correspondence on the surface of the touch screen, forming an optical network composed of infrared rays. When the user touches the screen, fingers or other opaque objects will Blocking the horizontal and vertical infrared rays passing through this point, the controller will judge the coordinate position of the contact point.

Both optical touch and infrared touch are widely used, and a rough comparison can be made between the two:

project

Infrared touch

Optical touch

Anti-light interference (environmental adaptability)

it is good

difference

responding speed

<4ms

> 10ms

Touch accuracy

5mm

2mm (90% area)

Touch dead zone

no

Have

Minimum touch object

5mm

8mm

Infrared and optical touch positioning technologies have their own advantages, but in general, optical touch positioning technology will be more critical to the external environment. When the device is exposed to direct sunlight, the optically touched device cannot be positioned, and there is currently no technology that can solve this problem. For infrared touch positioning, manufacturers who already have cutting-edge technology can completely overcome this problem, thereby ensuring that the interactive smart tablet environment is highly adaptable. For example, the perfect application of Yi Erzhuo products in Beijing Union University has proved that the infrared touch positioning technology used by it is not affected by light, nor is it affected by current, voltage and static electricity. In the teaching application, the lighting needs of the classroom determine the impossible "dark" teaching.

Secondly, the optical touch screen is positioned by calculating the Tan value of two included angles according to the geometric algorithm, but when the touch point is infinitely close to the top of the touch frame, that is, the included angle is infinitely small, the Tan value of the included angle will also become infinite Large, then the geometric algorithm cannot locate the touch point. This also means that when the touch point is close to the top of the touch frame, there will be a situation where it cannot be accurately positioned. The infrared touch positioning technology uses matrix arrangement calculations, and there is no "blind spot" on the entire screen.

Third, optical touch positioning relies on two lenses to emit and receive light sources. If one lens is damaged, the entire device will be paralyzed. Infrared touch positioning is based on a large number of lamps for scattering scanning. When a small number of lamps fail, the interactive smart tablet can completely "lightly hurt and not fire." In an extreme test environment, the Yi Er Zhuo brand can even run stably even when 10% of the lamps are not continuous.

Finally, optical touch positioning requires higher physical accuracy. Accidental collision or severe bumps may cause the optical camera to shift. After the camera is shifted, it cannot be accurately positioned, and the repair is very difficult. The infrared positioning technology does not have this problem.

It is for these reasons that the application of infrared touch positioning technology in interactive smart tablets is more common and has become the development trend of touch technology in the future.

In addition, many optical touch positioning patents are in the hands of foreign manufacturers. In order to break through the patent blockade, many domestic manufacturers have independently invested a lot of manpower and material resources, and have found new ways to carry out research and development, and have achieved tremendous results. For example, Vision Technology has dozens of infrared touch technology patents, and has further developed new patents such as touch writing follow, which makes infrared touch positioning faster and more accurate. Among them, the local calculation technology can calculate and process the touch screen partially but not all by predicting the range of the touch point only locally, thus greatly improving the positioning and writing speed.

Of course, touch positioning technology requires application software coordination and high-tech LCD driver matching. These have put forward higher requirements for manufacturers in the interactive smart tablet industry. Well-known software such as EasiNote for education is a supporting solution that can be perfectly combined with touch positioning technology.

The ultimate goal of touch positioning technology is to bring users a better touch experience. This is the direction of future technical efforts. The industry-leading enterprises represented by Vision Corporation will continue to lead the trend of exploration from the perspective of users.

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