Types of Touchscreen Digital Displays

Posted by on Jun 30, 2011 in Displays, DOOH

The following outlines some of the available touch screen applications that could be currently used in the digital signage and kiosk markets. If you have any questions regarding touch screen sign applications, please contact us.

Resistive

Several layers make up a resistive touchscreen panel. There are two layers that are the most important. They are made of thin electrically conductive metallic layers separated by a small space. When pressure is placed on one of the layers, as when someone touches the panels, the layers are able to connect. In this way, the layers act like the connecting output of two voltage dividers. When the layers touch, there is a change in the electrical current, which is sent to the controller for processing.

Although, resistive touchscreen solutions are, in general, considered the most price-conscious solution, they are also known to be the least clear. Unlike other solutions, the layers can be damaged by sharp objects. As the most widely used type of touchscreen on the market today, resistive touchscreen panels are not as susceptible to outside elements like water and dust.

Capacitive

Capacitive touchscreen panels conduct a continuous current of electricity across the sensor using a coating of indium tin oxide. As a result, the sensor has a much more controlled field of stored electrons in both the horizontal and vertical axes. The sensor acts as a capacitant. And, since the human body also contains stored electrons it exhibits capacitance. The sensors on the screen work based proximity and therefore do not have to be directly touched to be triggered. Capacitance touchscreens are used in many POS systems, informational kiosks, and control systems. One superb benefit of Capacitive resistance touchscreens is that they have a much higher clarity than resistive technology. One downside to capacitance technology is that it will only work with human touch and does not respond to a inanimate objects. Finally, capacitive resistance touchscreens support multi-touch capabilities.

Projected Capacitance

Projected Capacitance Touch technology is a subset of capacitance technology. It which involves X-Y array relationship where sensing wires embedded within two layers of non-metallic material are interrupted by a third object. In most cases, the third object involved is a human finger. The projected capacitance sensing wires and the user’s fingers forms capacitance. The controller system measures the capacitance made by the touch made and then relays the communication onto the the controller system and computer software.Projected capacitance touch technology is used with Interactive Foil. In this instance, a gloved hand can make the touch. Interactive Foil allows for touch applications to be utilized in external “through window” touch applications. These applications don’t require an actual “touch.”

Optical imaging

Optical imaging uses two or more sensors around the corner edges of the screen coupled with infrared back-lights. The lighting, placed in the field of a camera’s view of the other side of the screen, sense a touch when a shadow appears. The camera’s triangulate the touch to locate its location. This technology is quite scalable and very affordable, especially when it comes to larger displays.

Surface acoustic wave

Surface acoustic wave technology or SAW utilizes ultrasonic waves that register the positions of the touch. It then sends this information to a controller to process. Because ultrasonic waves are used, surface contaminants like water and dust can interfere with functionality.

Strain gauge

Strain gauge touchscreens utilize a spring-mounted display where four corners are connected to strain gauges. The gauges are used to determine deflection when the screen is contacted by touch. Because the screen is mounted on springs, it also utilizes measurements along the Z-axis. Strain gauge is typically used in outdoor-exposed systems because they have a hearty resistance to the elements.

Dispersive signal technology

DST was introduced by 3M in 2002. Mechanical energy in glass is measured by complex algorithms that interpret dispersive waves traveling through the solid medium. Because the technology is impervious to dust, scratches and other external elements, it is considered a very viable and scalable solution for multitouch on even the largest of displays. Dispersive signal technology also provides excellent optical clarity due to its lack of additional elements needed in the display. The displays can be detect both fingers and styluses. However, one downside is that the glass cannot detect a moving finger or stylus.

Acoustic pulse recognition

Similar to dispersive signal technology, acoustic pulse recognition utilizes two piezoelectric transducers located at positions onthe screen to turn the mechanical energy of a touch vibration into an electrical signal. The transducer signal allows the screen’s hardware to determine the location of the touch through a complex algorithm. The screen is made of ordinary glass, providing excellent clarity and durability. Like dispersive signal technology, acoustic pulse recognition does not allow for motioned touch once a touch has been initiated.

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