TOUCH TECHNOLOGY & COMPARISON

HOW IT WORKS

When a user touches the sensor on the touch panel with his finger, the input will be registered as an analog signal. The signal is converted into a digital signal by a controller in order for the computer to recognize the signal. The touch driver in the computer integrates various components to compile the digital signal in order for the video card to render the position of the touch event on the display.
Based on their structures and types of input sensing formats, touch screens can be divided into the following types: resistive touch screen, capacitive touch screen, SAW touch screen, optical touch screen, and electromagnetic digitizer
At present, the most extensively used controller for touch screens is the USB port controller. The function of a controller is to receive the analog signal from the sensors and convert it to a digital signal in order for the drivers to interpret the signal. Touch screen applications can offer an assortment of different usages through the design of touch drivers and functions. For example, the interface could be presented in different languages to make the operation easier for users of other nationalities; handwriting recognition, multi-screen system support, PC game support could also be added to enhance the touch screen's added value. Not only that, the operating software could also be custom designed according to clients' needs.

Resistive Touchscreen

A resistive touch screen is basically comprised of a layer of ITO Film and a layer of ITO Glass. The two layers are separated by DOT. A 5V electrical current is introduced to the ITO Film and ITO Glass. When a user touches the ITO Film with his finger or stylus, the indentation will result in contact with the ITO Glass at the bottom layer to result in a change of voltage.
The signal is converted into a digital one by the A/D controller in order for the PC to compute the coordinates (X and Y axis) of the touch event to achieve positioning. Resistive touch screens can be further divided into the 4-wire type and 5-wire type based on their performance and prevalence. With a 4-wire resistive touch screen, the X and Y axes are located on the ITO Film and ITO Glass. When the ITO Film sustains severe scratches, it results in short circuit and renders the touch screen panel inoperable. The 5-wire type can be seen as an improved version of the 4-wire resistive touch screen with the entire electrical field evenly panned out over the ITO Glass; the overlay of ITO Film merely acts as a conductor. As a result, when the ITO Film sustains scratch damage at a specific area, other portions of the touch panel can still function normally. However, if the damage is serious enough to affect the ITO Glass layer, the Touch Panel will still malfunction.

Capacitive Touchscreen

Capacitive touch screens are specifically designed to improve the shortcoming of low scratch resistance with resistive touch panels. The outermost layer of the structure is a thin film of hardened silicon dioxide that reaches 7H in scratch hardness; the second layer is ITO with a glass surface covered with an evenly spread out electrical field that detects traces of electrical current from the human body to achieve touch input. The bottom layer of ITO acts as a mask that keeps out interferences for the Touch Panel to function in optimal conditions.

SAW Touchscreen

SAW touch screen technology overcome the flaws inherent in capacitive touch screens. Capacitive touch screens are susceptible to interference by signal noise and static electricity. Although the surface has been hardened to reach 7H in scratch hardness, the layer of silicon dioxide (Sio2) has to be plated extremely thin in order to prevent insulation of electrical currents on the ITO surface. When excessive force is exerted to the surface of capacitive touch screen, it is still possible to damage the ITO layer and result in malfunction.
This leads to the development of SAW touch screen. It has a glass touch panel with three ultrasonic wave transmitters placed at three corners and a receiver placed in the middle to create an even field of acoustic waves. Since acoustic wave has the unique characteristics of losing energy when in contact with a soft medium, it is utilized to achieve positioning of touch input in the application.

Optical Touchscreen

Thanks to the improvement in LED quality and refinement of relevant manufacturing processes in recent years, optical touch screen is showing signs of a comeback in the market. Optical touch screens operate with infrared backlights and image sensors placed around the edges of the screen. The light beams along the X and Y axes form a matrix arrangement. When an opaque object obstructs the beams, the system is able to define the coordinates of the touch on the X and Y axes.

Electromagnetic Digitizer

Electromagnetic digitizer operates based on electromagnetic sensing; it involves the use of an electromagnetic pen that functions as a signal transmitter while the electromagnetic board acts as a receiver. When the transmitter is brought close to the panel surface, the change in magnetic flux is registered for the system to compute and define the coordinates of the touch event.

Comparsion

  Hardness Trans-parency Operating Force Contact media Resolution Resist water/dust performance Size Range

GTOUCH
4W Resistive

3H 80% 20g~50g Hands or TouchPen 4096×4096 Water proof for surface 1.4"~19"

GTOUCH
5W Resistive

3H 80% 20g~50g Hands or TouchPen 4096×4096 Water proof for surface 4.5"~26"

GTOUCH
Saw

7H 90% 30g~60g Hands & soft media 2048×2048 no good 7"~47"

GTOUCH
SCT

7H 90% 0g Hands 2048×2048 Water proof for surface 4.5"~26"

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PCT

7H 90% 0g Hands 2048×2048 Water proof for surface 7"~32"

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Infrared

7H 90% 0g Hands or any media(R>7mm) 4096×4096 no good Standard

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Optical

7H 90% 0g Hands or any media(R>5mm) 32767×32767 no good Standard