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LCD Display Manufacturers Compare the Advantages and Disadvantages of Various Touch Technologies

2013-08-02 10:25:06


At present, the touch control technologies used in products are infrared, resistive, capacitive, surface acoustic wave, optical image, image recognition, panel induction, electromagnetic, light spot, ultrasonic. The following is an analysis of the advantages and disadvantages of various touch control technologies.



1. Infrared ray: Scanning lines of horizontal and vertical lines are composed of infrared matrix. When an object blocks the light source, the position can be determined.

This is commonly known as the optical occlusion switch. This technology is often seen in movies and used for preservation detection. Application is very wide. such as, the positioning of the printer's print head and the rollers of the roller and mouse are all judged by the optical occlusion method. Its shortcoming is that the real resolution is not high, it's easy to be affected by light,  the reaction speed is slow, but it can sense any object that can occlude light.


Its determination is that there must be pairs of transmitters and receivers around.


At present, the redevelopment of infrared radiation is not the way of occlusion, but the mode of object reflection after launching. It is similar to radar speed measurement. This method can simulate many points, but it still has shielding problem. The cost of transmitting and receiving components increases. If the layout is intensive , the related cost will be higher.


2. Resistance type: contact the two conductive layers through pressure, and calculate the position of the object through the difference of impedance value.


Early stage, this technology was mostly used on small handwritten or touch boards, waterproof keyboards, etc., and early analog rockers, which were calculated by the potential difference generated by resistance. Now, this technology is widely used on mobile phones or small touch screens. Its advantage is that it can be operated by objects with enough pressure, such as hand and pen, and its accuracy will be affected. The influence of temperature and humidity produces the change of impedance value.


Its judgment is that when touching, there must be pressure, so there will be a considerable sense of elasticity, and the surface will be soft material and its technology.


3. Capacitance: Calculate the position of an object by changing the electric field affected by a conductive substance


This technology has been used on TV selectors 20 years ago, but many touch buttons that don't need to be pressed later, such as elevator buttons. In the early development, most of the surface is metal, but now many non-conductive materials can be used. Nowadays, touch boards of notebook computers mostly use this technology. The famous iPod also uses this technology, but its drawback is that it must be through shadow. The object responding to the electric field is inductive, and the reaction speed is slow. In addition, it may be affected by the nearby electromagnetic field to produce accuracy errors.


It can be judged by hand-held non-conductive materials 。


Two common technologies are surface capacitor (3M MiroTouch) or projective capacitor (Apple uses projective capacitor). The advantage of projective capacitor is non-contact induction, i.e. it can be sensed through glass or suspension. The advantage of its application is that the surface will not be depleted by long-term use. At present, projective capacitor can not only be multi-point through special process. Mitsubishi uses the human body to transmit different signals to achieve multi-person and multi-point touch.


4. Surface acoustic wave: High frequency sound wave is transmitted on the surface of medium. When the sound wave meets the absorption of soft material, the position can be calculated.


This technology is gradually used in touch screen, its accuracy and response speed are better than resistor or capacitor type, can also achieve a larger size, but because it must be placed around the carrier reflector antenna, so size changes must be customized, many game consoles have begun to use this technology.


Its judgment method can take the hard conductive material for testing, generally speaking, it will not induce the hard material.


A new extension of this technology is the use of surface shock waves (patented by 3M), which are tiny vibrations generated when an object touches a contact surface to calculate its position.


5. Optical images are passed through two or more CIRs (CMOS/CCD) to calculate the position from the shadow of the side object.


With the maturity of CMOS/CCD technology, this technology is more and more widely used. Now micro-CIR can output more than 100 pictures per second. So it is the fastest technology at present. Of course, with the increasing resolution of CIR, the processing speed is faster and faster, the sensitivity is better and better, and the size of shadow can be judged, so more and more changes can be made. The disadvantage of chemical applications is that they are more susceptible to light.


Its judgment method is to observe four corners, there must be more than two groups of CIR, and there must be reflective or luminous substances (invisible light such as infrared ultraviolet rays) or one side of the luminous substances (invisible light such as infrared ultraviolet rays).


At present, the main touch control technologies used in products are infrared, resistive, capacitive, surface acoustic wave, optical image, image recognition, panel induction, electromagnetic, light spot, ultrasonic. The following is an analysis of the advantages and disadvantages of various touch control technologies.


1. Infrared ray: Scanning lines of horizontal and vertical lines are composed of infrared matrix. When an object blocks the light source, the position can be determined.


This is commonly known as the optical occlusion switch. This technology is often seen in movies and used for preservation detection. Its application is very wide. For example, the positioning of the printer's print head and the rollers of the roller and mouse are all judged by the optical occlusion method. Its shortcoming is that the real resolution is not high, it is easy to be affected by light, and the reaction speed is slow, but it can sense any object that can occlude light.


Its determination is that there must be pairs of transmitters and receivers around.


At present, the redevelopment of infrared radiation is not the way of occlusion, but the mode of object reflection after launching. It is similar to radar speed measurement. This method can simulate many points, but it still has shielding problem. The cost of transmitting and receiving components increases. If the layout is intensive (to improve resolution), the related cost will be higher.


2. Resistance type: contact the two conductive layers through pressure, and calculate the position of the object through the difference of impedance value.


In the early days, this technology was mostly used on small handwritten or touch boards, thin film keyboards/waterproof keyboards, etc., and early analog rockers, which were calculated by the potential difference generated by resistance. Now, this technology is widely used on mobile phones or small touch screens. Its advantage is that it can be operated by objects with enough pressure, such as hand and pen, and its accuracy will be affected. The influence of temperature and humidity produces the change of impedance value.


Its judgment is that when touching, there must be pressure, so there will be a considerable sense of elasticity, and the surface will be soft material and its technology.


Due to the different process, there are four-line, five-line, eight-line and so on.


3. Capacitance: Calculate the position of an object by changing the electric field affected by a conductive substance


This technology has been used on TV selectors 20 years ago, but many touch buttons that don't need to be pressed later, such as elevator buttons. In the early development, most of the surface is metal, but now many non-conductive materials can be used. Nowadays, touch boards of notebook computers mostly use this technology. The famous iPod also uses this technology, but its drawback is that it must be through shadow. The object responding to the electric field is inductive, and the reaction speed is slow. In addition, it may be affected by the nearby electromagnetic field to produce accuracy errors.


It can be judged by hand-held non-conductive materials (conductive materials such as hand must be a certain distance from the contact surface).


Two common technologies are surface capacitor (3M MiroTouch) or projective capacitor (Apple uses projective capacitor). The advantage of projective capacitor is non-contact induction, i.e. it can be sensed through glass or suspension. The advantage of its application is that the surface will not be depleted by long-term use. At present, projective capacitor can not only be multi-point through special process. Mitsubishi uses the human body to transmit different signals to achieve multi-person and multi-point touch (that is, to distinguish which person is touching).


4. Surface acoustic wave: High frequency sound wave is transmitted on the surface of medium. When the sound wave meets the absorption of soft material, the position can be calculated.


This technology is gradually used in touch screen, its accuracy and response speed are better than resistor or or capacitor type, can also achieve a larger size, but because it must be placed around the carrier reflector antenna, so size changes must be customized, many game consoles have begun to use this technology.


Its judgment method can take the hard conductive material for testing, generally speaking, it will not induce the hard material.


A new extension of this technology is the use of surface shock waves (patented by 3M), which are tiny vibrations generated when an object touches a contact surface to calculate its position.



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