The development of touch screen
What’s fundamental of touch screen?
What are types of touch screen technology?
Business person pushing symbols on a touch screen interface
Touch screen, also called a touch-controlled panel, is an inductive liquid crystal display device that can receive input signals such as contacts. When the graphic buttons on the screen are touched, the tactile feedback system can drive various connected devices according to pre-programmed programs, can be wont to replace mechanical button panels, and use liquid display screens to make dynamic audio and video effects.
Touch screen as for a new input device. It’s a very easy and convenient way for human and machine. It gives multimedia a new look and is a very attractive new multimedia interactive device. Mainly used in public information query, industrial control, military command, video games, multimedia teaching, smart home, vending machine, etc.
With the development of touch screen technology, the touch technology goes through from professional to popularization, allowing more people to use to touch screen monitor. Its input method has gone through four stages from the original paper tape, keyboard, to mouse, and then touch input. What’s more, the touch screen is an interactive input device. The user only must touch a particular position on the screen for a finger or a lightweight pen to control the operation of the PC. Therefore, touch screen technology has the characteristics of straightforward operation and versatile use.
Now the touch screen had already applied to many areas, expect to apply to personal portable devices, it also widely applied to household appliances, public information queries (such as banks, hospitals, power businesses, etc.), video games, smart home, industrial control, and so on. Although just about 10 years for development, it has become the most acceptable computer input method of ordinary people after keyboard, mouse, handwriting pad, and voice input. Use this technique. But this touch screen technology very convenient for our life, and it will attract many customers to buy a device with a touch screen.
Touch screen technology is the most common computer input method accepted by ordinary people after keyboard, mouse, handwriting board, and voice input. Using this technology, the user can operate the host by gently touching the icon or text on the computer display screen of his fingers, thus making the human-computer interaction more straightforward. This technology greatly facilitates users and may be a very attractive new multimedia interactive device.
The essence of a slight screen may be a sensor, which consists of a slight detection component and a slight screen controller. The touch detection component is installed ahead of the monitor to detects the user’s touch position, then send it to the touch screen controller; the most function of the touch screen controller is to receive touch information from the touch point detection device, and convert it into contact coordinates and send it off the CPU, At an equivalent time, it can receive commands from the CPU and execute them.
According to the type of touch sensor, touch screen technology including five types of touch screen: Infrared touch screen, resistive touch screen, surface capacitive touch screen, surface acoustic wave touch screen, projected capactive touch screen.
Infrared touch screen is installed an electronic control frame in front of the monitor and the electronic control frame has an infrared transmitting tube and infrared receiving tube around the four sides, they are one-to-one correspondence to form a horizontal and vertical cross infrared matrix. When the users touch the infrared touch screen, the finger will block these two horizontal and vertical lines. So it can confirm the touch position on the monitor. Any touch matter can change the infrared line of touch points and then let the infrared touch screen work.
Advantage:
1. Not interfered by current, voltage, and static electricity, very fit to apply in some harsh environmental conditions
2. Compared with other touch screens, the infrared touch screen will be cheaper.
3. Easy to install, don’t need any other PCB board or controller board, can be installed in any type of computer.
4. The response speed is faster than the capacitive touch screen because there is no capacitor charging and discharging process
Disadvantage:
1. The electronic control frames easy to break
2. Easy interfered by light
3. Distortion in the case of curved surfaces
4. Lower resolution
The resistive touch screen’s outer layer generally uses a soft screen, through the press, and then connects together to the up and down point. The inner layer is equipped with a physical material oxide metal, that is, an N-type oxide semiconductor-Indium Tin Oxides (ITO), also called indium oxide, with a light transmittance of 80%, one layer on top and one layer on top of each other, separated in the middle. Resistive touch screens and capacitive touch screens all use ITO glass. Their working surface is ITO coating. Press the outer layer with your fingertips or any object to make the surface film concave and deform, so that the inner two layers of ITO touch and conduct electricity to locate To the coordinates of the pressing point to achieve control. The resistive touch screen including 4 wires resistive touch screen, 5 wires resistive touch screen, 8 wires resistive touch screen, and so on. The resistive touch screen is using the press to control. When fingers touch the screen, the two layers have connected at the touch point position and then the resistance has changed. At the X and Y position will have a signal, and then transport it to the touch screen controller. The controller will find this signal and calculate the X, Y position, then operate according to the simulation of the mouse.
Advantage:
1. Can be used in a harsh environment, not affected by dust, temperature, humidity. Because the resistive touch screen’s outer layer is plastic and the inner layer is the ITO glass.
2. Accurate positioning.
3. Cost-effective solution.
4. Suitable for wearing gloves and occasions that cannot be touched directly with hands.
Disadvantage:
1.Just can support one touch point, can’t support multi touch.
2.The outer screen film is easy to scratch.
3. Do not touch the screen with sharp objects.
In the surface capacitive touch screen, the transparent electrode layer is located on top of the glass panel and then will have a cover glass cover it. When finger to touch surface capacitive touch screen, it will react to the electrostatic capacity of the human body. The four-side sensor will test the decrease of the capacitor and allow control to confirm touch points. Surface capacitive touch screen just can through the finger or human’s skin or stylus with a charge to operate.
Advantage:
1. the surface capacitive touch screen is very durable
2. Perfect resistance to surface contaminants and liquids such as dust, oil, grease, water droplets
3. High scratch resistance
Disadvantage:
1. just can through the finger or human’s skin or stylus with a charge to operate.
2. Sensitivity to EMI.RFI
Surface acoustic wave touch screen (SAW)
It is designed by using the characteristics of sound waves. Taking the X axis as an example, the control circuit generates a transmitting signal (electrical signal). The electric signal is converted into an ultrasonic wave vibrating in the thickness direction by the X-axis transmitting transducer on the glass screen. The ultrasonic wave is refracted by the wedge-shaped seat under the transducer to produce an edge. The component propagated on the glass surface. The ultrasonic wave is reflected when it encounters a 45-degree inclined reflection line on the way forward, and generates a component that is 90 degrees to the incident wave and parallels to the Y axis. This component is transmitted to the other side of the glass screen in the X direction and also encounters a 45-degree inclined reflection The line is reflected and transmitted to the X-axis receiving transducer in the direction opposite to the emission direction. The X-axis receiving transducer converts the recovered sound waves into electrical signals. The control circuit processes the electrical signal to obtain a waveform that characterizes the acoustic energy distribution of the glass screen. When there is a touch, the finger will absorb part of the sound wave energy, and the recovered signal will be attenuated. The program can analyze the attenuation to determine the coordinates of the touch point in the X direction. In the same way, the coordinates in the Y-axis direction can be judged. Once the coordinates in the X and Y directions are determined, the touch point will naturally be uniquely determined.
Advantage:
1. Best optical performance, highest clarity, and light transmittance
2. Anti scratches and anti savage use
3. Sound waves are mechanical vibrations and are not affected by electromagnetic signals
4. Quickly react and long lasting
Disadvantage:
1.Affect by dust, water droplets, oil stains, etc. The reflector array needs to be cleaned regularly
Projected capactive touch screen
The capacitive touch screen may be a four-layer composite glass screen. The inner surface and therefore the inter-layer of the glass screen are each coated with a layer of ITO. The outermost layer may be a thin layer of silica glass protective layer. The inter-layer ITO coating is employed because the working surface, and therefore the four corners are led out Four electrodes, the inner layer of ITO may be a shielding layer to make sure an honest working environment. When a finger touches the metal layer, thanks to the electrical field of the physical body, a coupling capacitor is made between the user and therefore the surface of the touch screen. For high-frequency current, the capacitor may be a direct conductor, therefore the finger draws a little current from the contact point. This current flows from the electrodes on the four corners of the touch screen, and therefore the current flowing through these four electrodes is proportional to space from the finger to the four corners. The controller calculates the position of the touch point by accurately calculating the ratio of those four currents.
Advantage:
1. Just need touch, don’t need any press to control
2. Only one or no calibration after production
3. Can support multi touch
4. Wear-resistant, long life, low maintenance cost for users
Disadvantage:
1. The capacitive touch screen is easy to drift and cause inaccuracy when the environmental temperature and humidity changes
2. Easy reflective when applying in strong sunlight
Now I believe you are very clearly these five types of touch screen technology. You can according to your detail requirement to choose one type of touch screen for your project. As a projected capacitive touch screen manufacturer, we produce Pcap touchscreen/sensor glass/sensor film/, highly welcome to customize your pcap touchscreen. What’s more, our sales and engineering teams have at least 5 years of work experience in the touchscreen field. So please trust us, we will give you a suitable solution for your every project. And our pcap touchscreen panel mainly applies in industrial-control systems, medical devices, vending machines, automation, POS machine, and so on. So if you have any project need to customize the touchscreen panel. Come on! Contact us!
