Learning Centre Touch Screen Displays

SAW means surface Accoustics Touch  (Not common in Point of Sale)
Surface acoustic wave (SAW) technology uses ultrasonic waves that pass over the touchscreen panel. When the panel is touched, a portion of the wave is absorbed. This change in the ultrasonic waves registers the position of the touch event and sends this information to the controller for processing. Surface wave touchscreen panels can be damaged by outside elements. Contaminants on the surface can also interfere with the functionality of the touchscreen.[1]—by recognizing the sound created when the glass is touched at a given position.

Resistive Technology (Most common in All touch products especially point of sale)
AccuTouch technology is the workhorse of resistive touchscreens, providing unsurpassed performance in POS, industrial, medical, and transportation applications. Touch the screen with a finger, gloved hand, fingernail, or object such as a credit card, and you'll receive a fast, accurate response every time.

Capacitive Technology
A capacitive touchscreen panel is a sensor typically made of glass coated with a material such as indium tin oxide.[2][3] This type of sensor is basically a capacitor in which the plates are the overlapping areas between the horizontal and vertical axes in a grid pattern. Since the human body also conducts electricity, a touch on the surface of the sensor will affect the electric field and create a measurable change in the capacitance of the device. These sensors work on proximity, and do not have to be directly touched to be triggered. It is a durable technology that is used in a wide range of applications including point-of-sale systems, industrial controls, and public information kiosks. It has a higher clarity than Resistive technology, but it only responds to finger contact and will not work with a gloved hand or pen stylus unless the stylus is conductive

IR Touch Infrared Technology
Conventional optical-touch systems use an array of infrared (IR) light-emitting diodes (LEDs) on two adjacent bezel edges of a display, with photosensors placed on the two opposite bezel edges to analyze the system and determine a touch event. The LED and photosensor pairs create a grid of light beams across the display. An object (such as a finger or pen) that touches the screen interrupts the light beams, causing a measured decrease in light at the corresponding photosensors. The measured photosensor outputs can be used to locate a touch-point coordinate.

Sunlight Readable
A display becomes less viewable in a bright ambient light. This is true for both light emitting panels such as an OLED or for a transmissive LCD display that uses a backlight. In a bright ambient environment, the light from the sun competes with the light from the display and the perceived contrast goes down. We have two ways to deal with this intrinsic problem.

High Brightness
Building a stronger backlight unit behind the display or more efficient to guide the light from the source to the panel surface, It make the display viewable under sunlight

Transflective
The transflective technology gets enough light from a backlight unit to see the display in darker environments and under bright ambient conditions, light coming through the display is reflected. Such enhance the brightness on the panel surface not only from the backlight unit but also from the reflection.