Touch Screen Technology : Insights

By Ravi
Jun 3rd, 2012
3 Comments
2620 Views

Era of smartphones and tablets has come. The smartphone market would never have reached the same heights without the beautiful touch screen technology. Idlebrains brings to you the insights of the “Touch Screen Technology“. We will cover the types, working, usage and evolution of touch screen technology in this article.

Touch Screen – An electronic visual display screen that responds to the touch of human finger interaction or any other objects within the display area.

Touch screen provides you with the freedom to touch the display screen and the screen itself will react to your touch and particular action will be performed, which earlier was done using some indirect system such as mouse. ATM machines, shopping malls, business ventures or your interactive presentations, each one is using this magical technology.

In general, a touch screen system needs 3 major subsystems. One is the sensor, which senses the touch event by recognizing the voltage changes, second one is the controller, which converts the voltage changes into signals understandable by operating system and third one is the software program which perform the necessary action according to the touch event. The touch panel is always placed on top of the display panel.

For recognition of touch, 3 major technologies are used. Based on that, we majorly have 3 types of touch screens. 

R Type Touch:

System Design: The system consists of several layers placed over a normal glass panel. On top of the glass screen, there are 2 conductive and resistive metallic layers which are placed apart using some spacer dots. One more scratch resistant protective layer is placed on top of this complete system setup to protect the screen from scratches due to high pressure.

R Type Touch Screen Technology

R Type Touch Screen

Working : The R type touch is considered as a passive system as it works on the basis of the “pressure” applied on the screen to detect the event, no matter what is the object used to apply the pressure.  When we touch the display screen, both conductive and resistive layers contact each other at a certain point. Due to the contact, there are changes in electric field. According to the change in electric field across those two sheets, the exact coordinates of touch location are determined. These coordinates are sent to the operating system in proper format which performs the corresponding action.

Advantages:

  • Long Life, durability and reliability.
  • No limitation of using only specific objects to operate the screen.
  • More versatile usage.

Disadvantages:

  • Due to the electric field generation as a response to touch event and 3 layers on top of display screen, it emits just 75% of the light, which decreases the screen clarity.
  • The images shown are bulky and dim.

C Type Touch:

System Design: C type touch panel reacts to conductive material only. Human body is also conductive in nature as it has electrons moving in cells inside it hence C type touch screen also works as Human Interface Device(HID). In this system capacitive sensors are used to sense the position of touch. The glass panel is covered with a capacitive layer with static charge.

C Type Touch Screen Technology

C Type Touch Screen

Working: When human body touches the screen, some of the charge shifts to the human body and hence causing a decrease in the charge on the sheet. This decrease in charge is sensed by the system and according to the change detected in indicator circuits placed on different corners of the screen, the coordinates of touch are determined. These coordinates are transferred to computer to perform necessary action.

Advantages:

  • It consists of very thin capacitive layer instead of several layers as in case of R type, hence emits almost 90% of the light. Due to the same, the image clarity is very good.
  • It gives better quality and cleared picture than R type touch.
  • It responds only to human touch, hence enabling us to use fabric to clean the surface.
  • The response is also quite good as they are fine tuned to react against only any conductive material.
  • Any unintended touch by non conductive interfaces cannot cause harm to physical screen or send unexpected events causing the software crash.

Disadvantages:

  • Only human touch can cause the touch event so for the devices as projectors etc. it is not suitable.
  • For quick and fine touch, you cannot use object as stylus until n unless it’s made up of a conductive material.
  • You cannot work with gloves in your hands, wet fingers also cannot be used.
  • It is expensive.
  • No versatile usage possible.

Surface Acoustic Wave System Type Touch:

System Design: In this we have two transducers placed along X and Y axes of the glass panel. One is sending and other is receiving transducer. We also have reflectors placed on the screen to reflect the electrical signal sent from one transducer to the other.

Surface Acoustic Wave Touch Screen Technology

Surface Acoustic Wave Touch Screen

Working: When we press the screen, the signal sent by sending transducer is disturbed in between the transfer. The receiving transducer detects the disturbance and accordingly detects the position of touch. The coordinates are determined and sent to the operating system which performs the corresponding action.

Advantages:

  • There is no metallic layer placed over glass panel, hence it emits 100% light causing the best image quality.
  • Allows the touch by almost each object same as R type touch.
  • More versatile usage.

Disadvantages:

  • Doesn’t allow small objects to generate event.
  • Short life.
  • Much more expensive.

The touch screen technology today is at the heart of every innovation and almost everybody is talking about it but it is not new. It started in 1960s and after almost 50 years of journey, it has reached on the top. Let us have a quick walk through those steps once.

History of touch in last 5 decades:

1960s:

1965-1967: First ever touch screen, a capacitive one, invented by E.A.Johnson at the Royal Radar Establishment, UK.

1968: E.A.Johnson published a full description of touch screen technology in an article published for air traffic control.

1970s:

1971: A Touch sensor called the “Elograph” was developed by Doctor Sam Hurst and was patented by the University of Kentucky Research Foundation. It was non transparent.

1973: “The Elograph” was selected as one of the 100 most Significant New Technical Products of the year 1973 by Industrial Research.

1974: First true transparent touch screen was developed by Sam Hurst and Elographics now known as Elo TouchSystems.

1977: Elographics developed and patented a resistive touch screen technology. Also Siemens Corporation financed Elographics for development of first curved glass touch sensor interface, which became the first device to have a “touch screen” in its name.

1980s:

1983: The computer manufacturing company, Hewlett-Packard introduced HP-150, a home computer with touch screen technology.

1990s:

1993: Apple released a device equipped with handwriting recognition, called “Newton PDA.”
Also IBM released the first smartphone, Simon with touch interface.

1996: Palm entered the PDA market and introduced advanced touch screen technologies with its Pilot Series.

2000s:

2002: Microsoft came with Windows XP Tablet edition to introduce itself in touch screen technology.
2007: Apple introduced the smartest of all, the iPhone with touch screen technology.

Since then it has been a great roar for “Touch screen technology.” Now it’s hard to imagine anything without touch facility. As the time moves on, we expect some more innovative technologies to make our life simpler. Find some more interesting technical stuff in our Interesting X series.

About the Author

- Co-Founder of IdleBrains. Software engineer by profession, a poet at heart and tech writer by passion. Loves sweet music and cricket. Admirer and follower of Sachin Tendulkar. Follows his hobbies as “TheGhost”. Visit the poet here.

3 Responses to “Touch Screen Technology : Insights”

  1. yash says:

    Thanks for the information i was confused over old touch screen and the new one (in mobile phones). 🙂

  2. Harshit Jain says:

    Really informative..thanks!
    Would have liked to read about AMOLED as well 🙂

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