Touch Screen Technology

By- Akhila Shamsunder

INTRODUCTION

A touch screen is an input device that allows users to operate a PC by simply touching the display screen. The display screen has a sensitive glass overlay placed on it and we could give the desired input by touching it.  It is based on CRT (Cathode Ray Tube) technology that accepts direct onscreen input.

MAIN COMPONENTS OF TOUCH SCREEN ARE:

1.    Touch sensor

A touch screen sensor is a clear glass panel with a touch responsive surface which is placed over a display screen so that the responsive area of the panel covers the viewable area of the display screen. The sensor generally has an electrical current or signal going through it and touching the screen causes a voltage or signal change. This voltage change is used to determine the location of the touch to the screen.

2.    Controller

The controller is a small PC card that connects between the touch sensor and the PC. It takes information from the touch sensor and translates it into information that PC can understand.

3.    Software Driver

The driver is software that allows the touch screen and computer to work together. It tells the operating system how to interpret the touch event information that is sent from the controller.

TYPES OF TOUCH SCREEN

Ø  Resistive Touch screen

Ø  Surface wave Touch screen

Ø  Capacitive Touch screen

                                   *Surface capacitive

                                   *Projected capacitive

Ø  Near Field Imaging Touch screen

Ø  Infrared Touch screen

1.    Resistive touchscreen

Resistive touch screen monitor is composed of a flexible top layer and a rigid bottom layer separated by insulating dots, attached to a touch screen controller. The inside surface of each of the two layers is coated with a transparent metal oxide coating. Pressing the flexible top sheet creates electrical contact between the resistive layers, producing a switch closing in the circuit. The controller gets the alternating voltages between the two layers and converts them into the digital X and Y coordinates of the activated area.

2.    Surface Wave Technology

It has a transmitting and receiving transducers for both the X and Y axes. These waves are directed across the front surface of the touchscreen by an array of reflectors. The touchscreen controller sends a 5 MHz electrical signal to the transmitting transducer, which converts the signal into ultrasonic waves within the glass. Reflectors on the opposite side gather and direct the waves to the receiving transducer, which reconverts them into an electrical signal—a digital map of the touchscreen. When you touch the screen, you absorb a portion of the wave traveling across it. The received signal is then compared to the stored digital map, the change recognized, and a coordinate calculated. . The digitized coordinates are transmitted to the computer for processing.

3.    Capacitive Touch Screen

It has an uniform conductive coating on a glass panel. During operation, electrodes around the panel's edge evenly distribute a low voltage across the conductive layer & creates an uniform electric field. A finger touch draws current from each corner. Then the controller measures the ratio of the current flow from the corners and calculates the touch location. During a touch, capacitance forms between the finger and the sensor grid. The embedded serial controller in the touch screen calculates touch location coordinates and transmits them to the computer for processing.

APPLICATIONS

·         Public Information Displays

·         Customer Self-Services

·         Digital jukeboxes

·          Computerized gaming

·          Student Registration systems

·         Multimedia software

·         Scientific applications, etc.

ADVANTAGES

Ø  Direct pointing to the objects.

Ø  Fast

Ø  Finger or pen is usable (No cable required)

Ø  No keyboard necessary

Ø  Suited to: novices, application for information retrieval etc

DISADVANTAGES

Ø  Low precision by using finger

Ø  User has to sit or stand closer to the screen

Ø  The screen may be covered more by using hand

Ø  No direct activation to the selected function

CONCLUSION

Though the touch screen technology contains some limitations it’s very user friendly, fast, accurate, easy for the novices & fun to operate. It has been widely accepted. And now by just modifying a little it can replace the mouse and key board completely.