Introduction to the type of touch screen - Hitec

1. Resistive contact screen

Analog resistive screen

The analog resistive contact screen is what we generally call the "resistive screen", which is a kind of contact screen that uses pressure sensing to operate.

It uses two layers of ITO (indium tin oxide) plastic film coated with conductive function, and the two ITO are equipped with particle fulcrums, so that the screen has a certain space between the two layers of ITO when it is not pressed, and is in an unconductive state. When the operator presses the screen with his 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.

Now there are 4 wires, 5 wires, 6 wires and 8 wires and other types of analog resistive contact screens, as shown in Figure 1, the more lines, the higher the precision that can be detected, but the cost will also be relatively improved. The resistive screen does not support multi-touch, has high power consumption, short life, and long-term use together will bring detection point drift, which requires calibration. However, the structure of the resistive screen is simple and the cost is low, and the capacitive contact screen was mature, and once occupied most of the contact screen shopping mall.

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 use a substrate with ITO stripes. The ITO stripes of the upper and lower substrates are perpendicular to each other.

Digital resistive screens are more and more similar to a simple switch, so they are generally used as a membrane switch. The digital resistive screen is capable of multi-touch.

Introduction to the type of touch screen - Hitec

Introduction to the type of touch screen - Hitec

2. Capacitive contact screen

Exterior capacitive type

The surface capacitive contact screen senses the contact behavior of the screen surface through the electric field sensing method. 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, which generates a uniform electric field on the surface of the contact screen during operation. When the grounded object touches the surface of the screen, the electrode can sense the change of charge on the surface of the screen and confirm the coordinates of the touch point.

The capacitive contact screen has a long service life and high light transmittance, but it has low resolution and does not support multi-touch, so it is now mainly used in large-scale outdoor contact screens, such as public information channels (POI) and public service (sales) channels (POS) and other products.

Projected capacitive screen

Projected capacitive contact screens use electrostatic field lines emitted by contact screen electrodes for sensing. Projected capacitive sensing skills 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 detects the change in the coupling capacitance to confirm the orientation. However, in the case of a single point of contact, after the capacitance is changed, there is only one set of coordinates confirmed in the direction of the X and Y axes, and the combined coordinates are also unique. If there are two points in contact on the contact 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, as long as the two coordinates are real, the other two are commonly known as "ghost points". As a result, self-capacitive screens cannot complete true multi-point contact.

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 lines from one electrode to another. When the transverse electrodes announce the encouragement signal in turn, all the longitudinal electrodes will accept the signal together, 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 contact screen. When the human fingers are close to each other, it will lead to the reduction of part of the capacitance, according to the two-dimensional capacitance change data of the contact screen, the coordinates of each contact point can be calculated, so even if there are multiple contact points on the screen, the real coordinates of each contact point can be calculated.

In both types of projected capacitive sensors, the sensing capacitance can be planned in such a way that the finger contact can be detected at any given time, not just one finger, but 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 style, quickly replacing the resistive contact screen and becoming the mainstream touch technology in the shopping mall.

3. Infrared contact screen

The infrared contact screen uses an infrared matrix in the X and Y directions to detect and locate the user's contact. The infrared contact screen is equipped with 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 infrared matrix that crosses anyway. When the user touches the screen, the finger will block the two infrared rays passing through the direction, so as to determine the position of the contact point on the screen.

The infrared contact screen has the advantages of high light transmittance, not disturbed by current, voltage and static electricity, and high touch stability, but the infrared contact screen will be affected by the change of ambient light, and will be affected by infrared sources such as remote control, high-temperature objects, and incandescent lamps, and its accuracy will be reduced. The early infrared contact screen appeared in 1992, with a resolution of only 32×32, which is susceptible to environmental disturbance and malfunction, and requires to be used in a certain shading environment.

After 20 years of development, now the advanced infrared contact screen in the normal operating environment life is more than 7 years, when the tracking finger moves the track, the accuracy, smoothness and tracking speed can meet the requirements, the user's writing can be very smooth into the drawing track, fully support the handwriting recognition input. Infrared contact screen is mainly used in all kinds of public places, offices and industrial control places where the requirements are not very precise without infrared rays and strong light disturbance.

4. Sonic touch screen

Exterior sonic contact screen

The appearance of the sonic touch screen is a touch skill that is positioned by sound waves. In the four corners of the contact screen, sensors that emit and receive sound waves in the X and Y directions are pasted, and 45° reflective stripes are engraved around the perimeter. When a finger touches the screen, the finger absorbs a portion of the sound wave energy, while the controller detects the attenuation of the received signal at a certain moment in time, and calculates the orientation of the contact point.

In addition to the X and Y coordinates that can be responded to by general contact screens, it also responds to its unique third axis Z-axis coordinates, which is the pressure axis response. With this function, each contact point is not just two digital switches with and without contact, but an analog switch that senses force: the higher the pressure, the wider and deeper the attenuation gap in the waveform of the receiving signal.

In all types of contact screens, as long as the appearance of the sonic contact screen has the function of sensing contact pressure. The appearance of the acoustic contact screen is not affected by environmental factors such as temperature and humidity, with high clarity (extremely high resolution), good light transmittance, high durability, outstanding scratch resistance, active response, long life, can maintain clear and translucent picture quality, no drift, only need to be proofread once when installed, good anti-violence function, and is most suitable for public information inquiry and use in public places where the environment is relatively clean.

Zigzag sonic contact screen

The zigzag sonic touch screen is based on the skill of sound pulse recognition. When an object touches the surface of the contact screen, the sensor detects the frequency of the sound wave and compares the frequency with the standard frequency stored in the chip to confirm the orientation of the contact point. This method excludes fault identification caused by environmental elements such as clothing, luggage, dust and insects.

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

5. Optical imaging contact screen

Optical imaging contact screen is a touch skill that uses light to position, in the four corners of the screen to set up the light source and light capture sensor, when the object touches the surface of the contact screen, the light changes, the touch IC module analyzes the change of the light sensor to confirm the direction of the touch.

The optical imaging contact screen has high durability and is suitable for use in complex environments, and supports multi-touch, but it is easy to be misidentified by the influence of ambient light, dust, insects, etc. Now this skill is only used for desktop monitors over 10 inches, education/training, etc.

6. Electromagnetic induction contact screen

The sensor of the electromagnetic induction contact screen is installed 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 calculate the electromagnetic change to confirm the orientation of the touch point.

Compared with other contact screen skills, electromagnetic induction contact screen has the highest accuracy and resolution, low power consumption, and is more and more thinner, especially suitable for use in war environments and construction environments, and now this skill is mainly used in the United States military.

Other touch screen skills are now available in shopping malls in addition to the above-mentioned touch skills, as well as a variety of touch skills such as pressure-sensitive, digital sonic wave guided, and oscillating pointers, which are generally used for special purposes.

Introduction to the type of touch screen - Hitec

Sections viewed

Contact

working hours