Since the birth of computer equipment, the keyboard and mouse have always been the most basic input devices in the development of human-computer interaction, while the screen is only the output device of computer information; However, from beginning to end, human beings have always been fascinated by the natural user interface (commonly known as touch interface) represented by touch technology, because in this operation mode, people will have the most intuitive feeling and experience. In this operation mode, the screen is not only an output device, but also an input device, which can be operated directly on the screen through touch, To manipulate the computer.
With the popularity of mobile phones and other consumer digital products, small screen multi touch technology has gradually matured. At the same time, multi touch technology for large screen has gradually become the key demand of commercial display users, because relying on multi touch technology, interaction, feeling and experience with large screen can be realized, and large-scale multimedia interaction can be completed Screen effect demonstration and many other wonderful effects bring more convenience to daily work and study.
At present, for large screen commercial display, the realization of large screen multi touch technology has been relying on the multi touch technology of backscattered infrared light illumination in the past few years. The technical principle of backscattered infrared light illumination multi touch technology is that infrared light is illuminated from the back and integrated with diffuse reflection effect (the function of diffuse reflection is to generate diffuse reflection when infrared light shines on the diffuse reflection screen, so as to reduce the reflected infrared light being read by the camera) On the large screen, when the finger touches the screen, the finger will reflect more infrared light than the diffuse reflection screen, and the reflected infrared light is read by the infrared camera to form an electrical signal, which is finally calculated by the relevant software program to form specific touch coordinates and feed back to form the screen action.
To sum up, the backscattered illumination multi touch technology relies on the infrared camera to detect the infrared light reflected by the touched object to realize the positioning of the touch position. Therefore, from a technical point of view, this technology not only supports daily finger touch, but also supports the remote space separation operation of handheld infrared laser pen.However, based on this, if the indoor irradiation light or direct sunlight is particularly strong during normal use, the excessive infrared light will be monitored by the infrared camera, which will cause the system to misjudge the touch function, and then seriously interfere with and affect the touch effect of the large screen.For example, a few years ago, a large screen manufacturer designed and constructed a large screen project with multi touch function in a ministry in Beijing. Once, when a central leader inspected the Ministry and watched the multi touch large screen demonstration on site, due to a large number of flash photos gathered by accompanying reporters, there was a large screen touch failure in the on-site demonstration link, resulting in It left no small regret for the reception work of the Ministry.
In fact, from the analysis of technical principle, we can know that the light emitted by the camera flash not only contains many visible light visible to human eyes, but also emits ultraviolet light with a wavelength of 200nm-400nm and infrared light with a wavelength of 700nm-1200nm. The infrared light emitted by the flash passes through the screen, is received by the multi touch infrared camera and finally rotates Instead of electrical signals and touch signals, these signals conflict with the touch signals generated by human touch, resulting in the confusion of screen touch failure.
At present, the multi touch function of hisan laser screen, a large screen commercial display brand, is realized by using the laser plane multi touch technology. Its technical principle is that there are a group of laser transmitting tubes and receiving tubes on the upper, lower, left and right opposite sides of the laser screen respectively. The laser grid woven by the emission of the tubes is spread over the whole screen surface to form a laser surface when the finger touches the screen During the screen, the finger destroys the vertical and horizontal laser reception on the screen surface; therefore, when the receiving lamp does not receive the laser signal, the relevant software can find the specific coordinates of the finger touch position by analyzing the position of the non received laser lamp, and finally guide the screen to respond according to the finger moving position to form the touch interaction effect.
The biggest technical difference between laser plane multi-point touch and back scattered infrared light multi-point touch is that one is to determine the finger touch position coordinates according to the detection of the laser tube position that does not receive the laser, and the other is to determine the finger touch position coordinates by detecting the infrared line reflected from the finger touch position. Therefore, when the external light is strong, the back scattered light Lighting multi touch is more vulnerable to the interference of invisible infrared light in the external strong light line, which affects the normal use.
At the same time, under the background of the deepening application of big data and the Internet of things, more and more scenes require the use of large-size and large-area commercial display screens. At present, the laser plane multi touch technology can realize smooth touch operation of multiple people on the 322 inch multi touch screen at the same time. At the same time, with the unique intelligent touch recognition technology, it can In order to easily realize complex drawing and text writing on the large screen; while the multi-point touch control of backscattered infrared light is applied to the large-scale commercial display screen, many times, due to the uneven projection of infrared light, the touch resolution can not reach the screen resolution, which is easy to cause the phenomenon that the line sawtooth is not practiced or even disconnected during touch writing, which greatly affects the touch control Use experience.
Finally, at present, the laser plane multi touch technology has realized the integrated frame structure design and convenient and simple USB power supply, which is more convenient and easy in construction, installation, commissioning and later maintenance than the multi-component independent design of multi touch with backscattering infrared light.