The Evolution of Touchscreen Technology

Source | Dr. Goose

Since the popularization of smartphones, touchscreens have significantly changed our habits of using electronic products. With a simple swipe of a finger, daily entertainment, shopping, and more can be completed on a palm-sized smartphone.

But if we rewind 15 years, people back then would have found it hard to imagine that a seemingly simple screen could so magically change the way we live.

In fact, touchscreens appeared in human society much earlier than we think.

The concept of touch technology was proposed as early as the 1940s, and the first true touchscreen was created in 1965 by engineer Eric Arthur Johnson of the British Royal Radar Company. Johnson initially described his achievement in an article published in Electronics Letters, which is now known as the capacitive touchscreen.

The article published by Johnson in Electronics Letters

Capacitive touchscreens work by sensing the electric current of the human body and can be simply viewed as a screen composed of four layers: the outermost layer is a glass protective layer, followed by a conductive layer, the third layer is a non-conductive glass screen, and the innermost fourth layer is also a conductive layer.

The working principle is as follows: when a finger touches a capacitive touchscreen, a high-frequency signal is connected to the working surface. At this point, the finger and the touchscreen working surface form a coupling capacitor, equivalent to a conductor. When the finger touches, it draws a small current from the touch point, which flows out from the electrodes at the four corners of the touchscreen. The current flowing through the four electrodes is proportional to the straight-line distance from the finger to the corners, and the controller can calculate the coordinates of the contact point based on the ratio of the four currents.

Most of the smartphones we use today employ capacitive touchscreens, which are essentially developed based on Johnson’s invention. However, the capacitive touchscreen of 1965 did not achieve immediate fame and large-scale production, as a superior touch technology emerged soon after—the resistive touchscreen.

In 1971, Professor Sam Hurst from the University of Kentucky invented resistive touch technology that changes current transmission through pressure. Although the college funding this project did not believe this invention could soon leave the lab for commercial production, Dr. Hurst believed that with further improvements, this technology would replace the mouse as a more convenient way to control computers.

Later history proved his judgment to be correct.

The company Elographics, founded by Dr. Hurst, officially developed the resistive touchscreen for computers in 1977 and quickly obtained a patent. Since then, countless companies have developed various types of resistive touchscreens based on it, and until 2007, resistive touchscreens held a dominant market position.

Before the invention of resistive touch technology, there was also the invention of touchscreens based on infrared technology.

PLATO was the first general-purpose computer-assisted teaching system, and in its development, the fourth generation of PLATO introduced terminals equipped with touch-capable semi-transparent plasma displays. In this terminal, students could answer questions by touching any position on the screen, making PLATO IV the first touchscreen computer used in classrooms.

However, this infrared touch technology struggled to improve screen display transparency; thus, resistive touch technology remained the hot application.

So why did resistive touch technology gain market recognition faster than other touch technologies at that time?

First, let’s look at the working principle of resistive touchscreens.

In simple terms, a resistive touchscreen works by sensing pressure to control the conductive state of the screen. Its structure is basically a film plus glass, with both the film and the glass coated with ITO (Indium Tin Oxides, a nano-scale indium tin oxide). ITO has excellent conductivity and transparency (the yellow part labeled 2 in the image below).

When a person’s finger touches the screen, the ITO on the lower film contacts the ITO on the upper glass, and the sensor transmits the corresponding signal, which is then sent to the processor through a conversion circuit, converting it into X and Y values on the screen, completing the selection action and displaying it on the screen.

Image source: Internet

From the 1970s invention to the 1990s, the resistive touchscreen had obvious advantages over capacitive touchscreens:

1. The touch operation of resistive touchscreens is relatively stable because it only requires a certain amount of pressure to operate successfully, unaffected by temperature, the operator, or harsh environments.

2. Resistive touchscreens have a longer lifespan than capacitive touchscreens.

3. The production cost of resistive touchscreens is lower, facilitating large-scale commercial production.

Starting in the 1980s, as the portability of computers gradually improved, technology companies saw the opportunity to combine touchscreens with computers. HP was the first company to release touchscreen computer products, and prior to this, HP had already made a name for itself in the computer manufacturing industry. The first product to be called a “personal computer” was released by HP. However, due to design flaws and ergonomic issues, this attempt did not yield ideal results.

HP-150 Computer

Since the invention of touch technology, there has been a technical difficulty that has been hard to solve—only single clicks could be registered, and simultaneous multi-touch was impossible.

To solve this problem, in 1982, the University of Toronto developed a tablet computer that tracked gestures using an internal camera, allowing the screen to read multiple touch points simultaneously;

Around the same time, American computer designer Myron Krueger developed an optical system to track gesture movements, which was the precursor to the gesture recognition function in today’s touchscreens;

Then in 1984, Dr. Bob Boie from Bell Labs developed a multi-touch screen based on capacitive touch technology, allowing users to draw images at different locations on the screen simultaneously, recognized as the first screen to truly implement multi-touch operations.

By the 1990s, the technology for multi-touch had matured significantly. In 1993, IBM and BellSouth jointly released the first mobile phone product that combined a touchscreen with a phone, Simon, which is now regarded as the first smartphone with a calendar, address book, and notepad.

IBM’s first smartphone, Simon

In 1998, Professor John Elias from the University of Delaware and Wayne Westerman, a PhD student, founded FingerWorks. Based on Westerman’s research, FingerWorks developed the first batch of multi-touch products, including TouchStream LP, MacNTouch, and iGesture Pad, all of which received high praise. However, due to their high prices, these products remained high-end and did not truly integrate into the broader consumer market.

A turning point came in 2005.

That year, Apple acquired FingerWorks, along with all its multi-touch patents and products, and applied this technology to its upcoming products.

In 2007, the first fully touchscreen-controlled smartphone, the iPhone, was launched. Steve Jobs showcased this compact and sleek phone at the product launch, leaving a deep impression with its stylish design and user-friendly interface, especially the classic unlock interface that swiped from left to right. It was from this year onwards that touchscreens gradually entered and became an indispensable part of our lives.

The subsequent story is something most people have personally experienced. Starting with the iPhone, smartphones, aided by multi-touch screens, achieved many functions that could previously only be performed on computers. We only need to pinch in and out with two fingers to zoom in or out of an image; the phone keyboard is no longer necessary, and all operations can be performed on a simple screen.

Image source: Internet

By 2020, touchscreens can no longer be considered a novelty. Not only are they present in our everyday smartphones and tablets, but touchscreen displays are also ubiquitous on the streets, and scientists are working hard to create bolder innovations.

Can touch technology break free from the constraints of physical devices?

In fact, there are already conceptual technologies that project touchscreens onto the human body using optical recognition technology. Perhaps in the near future, people will not only leave their wallets at home but will also have their smartphones become part of their bodies, with touchscreens projected onto any object, turning scenes from science fiction movies into reality.

This article is adapted from: Chengmai Technology

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The Evolution of Touchscreen Technology

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