Kunlun Tongtai touch screen - six different classifications of touch screens

1. Resistive touch screen

Analog resistive screen

The analog resistive touch screen is what we usually call the "resistive screen", which is a kind of touch screen that uses pressure sensing to control.

It uses two layers of ITO plastic film coated with conductive function, and the two ITO are equipped with particle fulcrums, so that the screen has a certain gap between the two layers of ITO when it is not pressed, and is in an unconductive state.

When the operator presses the screen with a fingertip or pen tip, the pressure will make the film concave, and the ITO layer will be contacted and conductive due to deformation, and then the corresponding pressure point will be converted by detecting the voltage change of the X axis and Y axis, so as to complete the touch processing mechanism of the entire screen.

At present, there are 4-wire, 5-wire, 6-wire and 8-wire analog resistive touch screens. The higher the number of lines, the higher the accuracy of the detection, but the higher the cost.

In addition, the resistive screen does not support multi-touch, has high power consumption, short life, and long-term use will bring detection point drift, which requires calibration. However, the resistive screen has a simple structure and low cost, and before the capacitive touch screen matured, it once occupied most of the touch screen market.

Digital resistive screen

The basic principle of digital resistive screens is similar to that of analog resistive screens, and unlike analog resistive screens, which evenly coat the ITO layer on the glass substrate, digital resistive screens only utilize a substrate with ITO stripes. Among them, the ITO stripes of the upper and lower substrates are perpendicular to each other.

Digital resistive screens are more akin to a simple switch, so they are often used as a membrane switch. The digital resistive screen enables multi-touch.

2. Capacitive touch screen

Surface capacitive

Surface capacitive touch screens sense the touch behavior of the screen surface by means of electric field sensing. Its panel is a uniformly coated ITO layer, and each of the four corners of the panel has an outlet wire connected to the controller, and the surface of the touch screen generates a uniform electric field when working.

Surface capacitive touch screens are characterized by long service life and high light transmittance, but they have low resolution and do not support multi-touch.

At present, it is mainly used in large-size outdoor touch screens, such as public information platforms, public service platforms and other products.

Projected capacitive screen

Projected capacitive touch screens use electrostatic field lines emitted by touch screen electrodes for sensing. Projected capacitive sensing technology can be divided into two types: self-capacitance and interactive capacitance.

Self-capacitance, also known as absolute capacitance, uses the perceived object as another plate of the capacitance, which induces a charge between the sensing electrode and the sensing electrode, and determines the position by detecting the change in the coupling capacitance. However, in the case of a single touch, through capacitance changes, there is only one set of coordinates determined in the direction of the X and Y axes, and the combined coordinates are also unique. If there are two touches on the touch screen and the two points are not in the same X direction or the same Y direction, and there are two coordinate projections in the X and Y directions, then 4 coordinates are combined. Obviously, only two coordinates are real, and the other two are commonly known as "ghost points". As a result, self-capacitive screens cannot achieve true multi-touch.

Interaction capacitance, also known as spanning capacitance, is the capacitance generated by the coupling of adjacent electrodes, and the change in interaction capacitance is felt when the perceived object approaches the electric field line from one electrode to another. When the transverse electrodes send out an excitation signal in turn, all the longitudinal electrodes receive the signal at the same time, so that the capacitance value of the intersection of all transverse and longitudinal electrodes can be obtained, that is, the capacitance of the two-dimensional plane of the entire touch screen. When the human fingers are close, it will lead to a decrease in local capacitance, and the coordinates of each touch point can be calculated according to the two-dimensional capacitance change data of the touch screen, so even if there are multiple touch points on the screen, the real coordinates of each touch point can be calculated.

In the above two types of projected capacitive sensors, the sensing capacitance can be designed in such a way that the touch of a finger can be detected at any given time, and the touch is not limited to one finger, but can also be multiple fingers.

Since 2007, Apple's iPhone and iPad series products have achieved great success, and the projected capacitive screen has begun to develop in a blowout, quickly replacing the resistive touch screen and becoming the mainstream touch technology in the market.

3. 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 installs a circuit board frame in front of the display, and the circuit board arranges infrared emitting tubes and infrared receiving tubes on the four sides of the screen, which correspond to the horizontal and vertical infrared matrix. When the user touches the screen, the finger blocks the horizontal and vertical infrared rays passing through the location. Based on this, the position of the touch point on the screen can be determined.

The infrared touch screen has the advantages of high light transmittance, no interference from current, voltage and static electricity, and high touch stability. However, the infrared touch screen will be affected by the change of ambient light, and will be affected by infrared sources such as remote controls, high-temperature objects, and incandescent lamps, which will reduce its accuracy.

The early infrared touch screen appeared in 1992, with a resolution of only 32×32, which is susceptible to malfunction due to environmental interference, and requires to be used in a certain shading environment.

After 20 years of development, the current advanced infrared touch screen has a life span of more than 7 years in the normal working environment, and when tracking the finger movement track, the accuracy, smoothness and tracking speed can meet the requirements, and the user's writing can be converted into an image trajectory very smoothly, fully supporting handwriting recognition input.

Infrared touch screen is mainly used in all kinds of public places, offices and industrial control places where the requirements are not very precise without infrared and strong light interference.

4. Sonic touch screen

Surface acoustic touch screen

Surface acoustic touch screen is a touch technology that uses sound waves to locate the touch.

In the four corners of the touch screen, sensors that transmit and receive sound waves in the X and Y directions are pasted, and 45° reflection stripes are engraved around them. When a finger touches the screen, the finger absorbs a portion of the sound wave energy, and the controller detects the attenuation of the received signal at a certain point in time, from which it calculates the position of the touch point.

The surface acoustic wave technology is very stable and has very high accuracy, in addition to the X and Y coordinates that can be responded to by ordinary touch screens, it also responds to its unique third axis Z-axis coordinates, that is, the pressure axis response.

Of all types of touch screens, only surface acoustic touchscreens have the ability to sense touch pressure. The surface acoustic touch screen is not affected by environmental factors such as temperature and humidity, with high definition, good light transmittance, high durability, good scratch resistance, sensitive response, long life, can maintain clear and transparent image quality, no drift, only needs to be corrected once during installation, good anti-violence performance, and is most suitable for public information inquiry and public places with clean offices, government agencies and environments.

Curved sonic touchscreen

The curved sonic touch screen is based on sound pulse recognition technology.

When an object touches the surface of the touchscreen, the sensor detects the frequency of the sound wave and determines the location of the touch point by comparing this frequency to a standard frequency pre-stored in the chip.

The sound waves of the surface touch screen propagate along the surface of the substrate, while the curved sound waves propagate inside the substrate, so the anti-environmental interference performance of the curved type is better than that of the surface type. At present, curved touch screens are generally used for kiosks over 5 inches, financial equipment, vending machines, etc.

5. Optical imaging touch screen

Optical imaging touch screen is a touch technology that uses light to position, and the light source and light capture sensor are set at the four corners of the screen, when the object touches the surface of the touch screen, the light changes, and the touch IC module analyzes the change of the light sensor to determine the position of the touch.

The optical imaging touch screen has high durability and is suitable for use in complex environments, and supports multi-touch, but it is easy to be affected by ambient light, dust, insects, etc.

6. Electromagnetic induction touch screen

The sensor of the electromagnetic induction touch screen is set behind the display, and the sensor creates an electromagnetic area on the surface of the display, and when the electronic pen touches the surface of the display, the sensor can determine the position of the touch point by calculating the electromagnetic change.

Compared with other touch screen technologies, electromagnetic induction touch screens have the highest accuracy and resolution, low power consumption, and are thinner and lighter, especially suitable for use in war environments and building environments, and the technology is currently mainly used in the United States military.

Other touch screen technologiesIn addition to the above-mentioned touch technologies, there are also a variety of touch technologies such as pressure-sensing, digital sound wave guided, oscillating pointer, etc., which are generally used for special purposes.

Kunlun Tongtai touch screen - six different classifications of touch screens

Kunlun Tongtai touch screen - six different classifications of touch screens

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