This allows the system electronics to measure each node intersection individually to detect multiple touches on the screen during one screen scan.
When a finger touches near an intersection, some of the mutual capacitance between the row and column is coupled to the finger which reduce the capacitance at the intersection as measured by the system electronics. This reduced capacitance crosses the "touch threshold" set by the electronics indicating a touch has occurred. Extremely durable Very accurate Good optical clarity Good resolution. Requires bare finger or capacitive stylus Severe scratch can affect operation within the damaged area.
The DST Touch System determines the touch position by pinpointing the source of "bending waves" created by finger or stylus contact within the glass substrate. This process of interpreting bending waves within the glass substrate helps eliminate traditional performance issues related to on-screen contaminants and surface damage, and provides fast, accurate touch attributes.
Fast, accurate repeatable touch Touch operates with static objects or other touches on the screen Touch unaffected by surface contaminants, such as dirt, dust and grime Excellent light transmission provides vibrant optical characteristics with anti-glare properties Operation unaffected by surface damage Input flexibility from finger or stylus, such as pencil, credit card, fingernail, or almost any pointing stylus Available for display sizes 32" to 46". More expensive to integrate than Optical Only available for displays 32" and larger.
Acoustic wave touch screens use transducers mounted at the edge of a glass overlay to emit ultrasonic sound waves along two sides.
These waves are reflected across the surface of the glass and received by sensors. A finger or other soft tipped stylus absorbs some of the acoustic energy and the controller measures the amplitude change of the wave to determine touch location. Requires finger or sound absorbing stylus Difficult to industrialize Signal affected by surface liquids or other contaminants. Infrared touch screens are based on light-beam interruption technology. Instead of an overlay on the surface, a frame surrounds the display.
The frame has light sources, or light emitting diodes LEDs on one side and light detectors on the opposite side, creating an optical grid across the screen. When an object touches the screen, the invisible light beam is interrupted, causing a drop in the signal received by the photo sensors. Optical touch screen technology uses two line scanning cameras located at the corners of the screen. The cameras track the movement of any object close to the surface by detecting the interruption of an infra-red light source.
The light is emitted in a plane across the surface of the screen and can be either active infra-red LED or passive special reflective surfaces. Can be affected by direct sunlight Frame increases overall depth of monitor Cannot be fitted to plasma and LCD displays with integrated speakers. Single Touch occurs when a finger or stylus creates a touch event on the surface of a touch sensor or within a touch field so it is detected by the touch controller and the application can determine the X,Y coordinates of the touch event.
These technologies have been integrated into millions of devices and typically do not have the ability to detect or resolve more than a single touch point at a time as part of their standard configuration. If offered by a touchscreen, you can typically pinch the screen using two fingers to zoom the display in or out.
This is just one of many applications in which multi-touch is used. With that said, only some touchscreens support multi-touch. The most common type of touchscreen technology, capacitive, supports multi-touch.
Capacitive touchscreens, of course, use capacitance to detect touch commands. Touching the display with a bare finger or a conductive object causes a change in capacitance. Your finger or the object will essentially draw some of the electrostatic field from the device, resulting in a change in capacitance. For instance, you can an icon with your index finger to open the app on an smartphone, which is a single-touch function because it uses a single touch.
As such, developers began to experiment with a new form of touchscreen technology: multi-touch. Unlike single-touch, multi-touch supports the use of two or more simultaneous touch-based commands. If you want to zoom in, you pinch the screen inwards using two fingers. If you want to zoom out, you perform the opposite motion, pinching outwards. Features such as this are not found on single-touch devices, simply because it cannot register two simultaneous points of contact.
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