LCD touch screen

touch screen

1. Capacitive technology touch screen　　

It uses the current induction of the human body to work. The capacitive touch screen is a four-layer composite glass screen. The inner surface and the interlayer of the glass screen are each coated with a layer of ITO. The outermost layer is a thin layer of silica glass protective layer. The interlayer ITO coating is used as the working surface. Lead out four electrodes, the inner ITO is a shielding layer to ensure a good working environment. When a finger touches the metal layer, due to the electric field of the human body, the user and the surface of the touch screen form a coupling capacitor. For high-frequency current, the capacitor is a direct conductor, so the finger draws a small current from the contact point. This current flows from the electrodes on the four corners of the touch screen, and the current flowing through these four electrodes is proportional to the distance from the finger to the four corners. The controller obtains the position of the touch point by accurately calculating the ratio of these four currents. .

2. Infrared touch screen

The infrared touch screen uses the dense infrared matrix in the X and Y directions to detect and locate the user's touch. The infrared touch screen is equipped with a circuit board outer frame in front of the display. The circuit board arranges infrared emitting tubes and infrared receiving tubes on the four sides of the screen to form a horizontal and vertical cross infrared matrix. When the user touches the screen, the finger will block the horizontal and vertical two infrared rays passing through the position, so the position of the touch point on the screen can be judged. Any touch object can change the infrared ray on the contact to realize touch screen operation. In the early conception, infrared touch screens had technical limitations such as low resolution, limited touch methods, and susceptibility to environmental interference and misoperation, and thus faded out of the market. Since then, the second-generation infrared screen has partially solved the problem of anti-light interference. The third and fourth generations have also improved resolution and stability, but they have not made a qualitative leap in key indicators or overall performance. However, anyone who knows touch screen technology knows that infrared touch screens are not interfered by current, voltage and static electricity, and are suitable for harsh environmental conditions. Infrared technology is the ultimate development trend of touch screen products. Touch screens that use acoustics and other materials science technologies have their insurmountable barriers, such as damage and aging of a single sensor, fear of contamination of the touch interface, destructive use, and complicated maintenance. As long as infrared touch screens truly achieve high stability and high resolution, they will replace other technical products and become the mainstream of the touch screen market. In the past, the resolution of infrared touch screens was determined by the number of infrared pairs in the frame, so the resolution was low. The main domestic products on the market were 32x32 and 40X32. In addition, infrared screens are more sensitive to light environment factors, and the light changes more. It will misjudgment or even crash when it is big. These are the weaknesses of the infrared screens sold by domestic agents of foreign non-infrared touch screens. The resolution of the latest technology fifth-generation infrared screen depends on the number of infrared pairs, scanning frequency and difference algorithm. The resolution has reached 1000X720. As for the infrared screen is unstable under light conditions, from the second-generation infrared touch screen From the beginning, the weakness of anti-light interference has been better overcome. The fifth-generation infrared touch screen is a new generation of intelligent technology products. It has realized 1000*720 high resolution, multi-level self-adjustment and self-recovery hardware adaptability and highly intelligent discrimination and recognition, which can be used in various harsh environments for a long time Use it at will. And it can customize extended functions for users, such as network control, sound sensing, human proximity sensing, user software encryption protection, infrared data transmission, etc. The other major shortcoming of the infrared touch screen promoted by the original media is its poor riot resistance. In fact, the infrared screen can use any riot glass that customers find satisfactory without increasing the cost and affecting the performance. This is something other touch screens cannot imitate.