Efforts by: Ankit Puri B-Tech ECE

O VERVIEW Introduction Multi Point Touch Touchscreen Technologies Comparison Of Technologies Conclusion Future Technologies

I NTRODUCTION A touchscreen is an electronic visual display that can detect the presence and location of a touch within the display area. Touchscreens can sense by touching the display of device by finger, hand or devices such as a stylus.

H ISTORY Touchscreen emerged from academic and corporate research lab in late 1960’s. One of the first places where they gained some visibility was in the learning terminal of a computer-assisted that came out in 1972 as part of the PLATO project. The HP-150 from 1983 was probably the world's earliest commercial touchscreen computer. It doesn't actually have a touchscreen in the strict sense, but a 9" Sony CRT surrounded by infrared transmitters and receivers which detect the position of any non-transparent object on the screen.

M ULTI -P OINT T OUCH Until the early 1980s, most consumer touchscreens could only sense one point of contact at a time, and few have had the capability to sense how hard one is touc hing. The development of multi-point touch facilitated the tracking of more then one finger on a screen With the influence of multi touch the touch screen market for mobile devices is projected to produce 15 Billon $ in 2011

T OUCHSCREEN T ECHNOLOGIES Resistive Touchscreen Capacitive Touchscreen Surface Acoustic Wave Touchscreen Infrared Based Touchscreen

W ORKING O F R ESISTIVE S ENSORS Resistive touchscreen monitor is composed of Flexible Top Layer ( Plastic Film ) Rigid Bottom Layer ( Substrate ) Insulating Dots ( Spacer ) Top and Bottom Layers are transparent. Pressure over top layer makes the electric contact between resistive bottom layer. With the help of controller alternative voltages are converted into digital X Y co-ordinates and mark the position of touch. Resistive technology gives only 75% optical transparency and the fact that sharp objects can destroy resistive layers.

W ORKING O F C APACITIVE S ENSORS The sensor consists of four electrodes which are subjected to small amount of voltage. As the human body is also an electrical conductor, touching the surface of the screen results in a distortion of the screen's electrostatic field, measurable as a change in capacitance. The location is then sent to the controller for processing. Unlike resistive touchscreens, you can't use a capacitive touchscreen with gloves in winter time: you need a special capacitive stylus, or a special designed glove with finger tips that generate static electricity.

W ORKING O F SAW T ECHNOLOGY Surface acoustic wave (SAW) technology uses ultrasonic waves that pass over the touchscreen panel. On the pure glass substrate there are four piezoelectric transmitter and receiver transducer on three corners of both X Y axis. The SAW controller sends 5 MHz electrical signal to X Y axis transmitting transducers. When the touchscreen is touched the finger absorbs a portion of a wave passing across the surface, which is sensed by receiving transducer.

W ORKING O F I NFRARED S ENSORS An infrared touchscreen uses an array of X-Y infrared LED and photodetector pairs around the edges of the screen to detect a disruption in the pattern of LED beams. these LED beams cross each other in vertical and horizontal patterns. This helps the sensors pick up the exact location of the touch. Unlike all other touchscreens, infrared touchscreens do not require any patterning on the glass which increases durability and optical clarity of the overall system.

C OMPARISON OF T ECHNOLOGIES ResistiveSAWInfraredCapacitan ce Durability5 Years 3 Years2 Years StabilityHighHigherHighGood Transparency okGoodHighHigher Touch TypeAnythingFinger/PenSharp Object Conductive Response Time < 10 ms < 20 ms< 15 ms Application

E RGONOMICS A ND U SAGE Finger Stress The stress on human fingers when used for more than a few minutes at a time a significant pressure is required and the screen is non- flexible. Finger Prints Touch screens also suffer from the problem of fingerprints on the display. This can be mitigated by the use of materials with optical coatings designed to reduced the visible effects of fingerprint oils. Finger nail as Stylus Rather than pressing with the soft skin of an outstretched fingertip, the finger is curled over, so that the top of the forward edge of a fingernail can be used instead Gorilla Arm The defect is usually seen in Fine Art Painters due to their posture and repetitiveness of their movements while painting.

F UTURE O F T OUCHSCREEN T ECHNOLOGIES In future there is no usage of mouse and keyboards as they will be replaced by touchscreens.

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