Our Educational Primer Series presents a deep dive into the technical elements that bring together the world of 4D Systems and what we have to offer. You’ll find that this information series, developed with our experts and engineers, is the perfect place to power up your knowledge and take your understanding of our hardware and software to the next level. As always, feel free to reach out and get in touch. The best learning is interactive and we’d love to hear from you.

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What is Pulse Width Modulation?

Have you ever wondered how computers dissipate the amount of heat that gets generated by the CPU and other components? Compact electrical fans have been used for better ventilation and for cooling PCs. However, as fans produce noise levels that increase with the rotation speed, different methods were explored to control the speed of the motor and to ultimately quieten it. In recent years, the technology of controlling the power’s output has evolved significantly. Researchers have been looking for methods where a microcontroller or a switch would constantly control the amount of power a motor delivers, as mentioned in the above case, the fan in a PC.

So what is PWM and how does it work? And what are the ways to use the PWM outputs on your intelligent display?

What is PWM?

Pulse Width Modulation (PWM) is a method used for controlling an analogue signal using a digital source. The output voltage of the converter is controlled by modulating the width of the pulse. A lot of power electronic circuits are controlled by PWM signals of various forms.

How does PWM work? 

A PWM signal consists of a duty cycle and a frequency. The duty cycle is the amount of time in which the signal is active or is in a ‘high’ or ‘on’ state. The duty cycle is expressed as a percentage or ratio of the total time it takes to complete one cycle. The frequency is calculated by finding out how fast the PWM completes a duty cycle. In other words, it means the frequency is determined how fast it switches between high and low states. By steering a digital signal off and on at a fast rate and at a particular duty cycle, the output will perform like a constant voltage analogue signal when providing power to devices.

The energy is distributed through a series of pulses rather than a continuously varying signal. By increasing or decreasing pulse width, i.e. how long the digital signal is held high, the energy flow to the motor shaft can be controlled.

PWM is found in a wide variety of applications, ranging from control circuitry to telecommunications to servomechanisms to power delivery and as an efficient voltage regulator.

Let’s take a look at the ways to use the PWM outputs on your intelligent display.

Dimming the LED backlight

One of the most popular applications of PWM is controlling the brightness of LED and LCD displays. The majority of LCD displays contain a LED backlight. LED lighting is used due to its efficiency, life span, and energy saving properties. Because the brightness and colour of an LED can affect the display, the LED lighting system requires an application to adjust the brightness and colour at the same time. PWM can be used to control the brightness level of the LED by turning the LED on and off at a specific rate. The naked eye cannot see these rapid oscillations of light, so even when the light is off we see the light as on.

Controlling the brightness of the display in laptops

Following the same principle, PWM is also used to regulate the brightness of the display in laptop monitors. When a monitor is set to maximum brightness the LEDs are glowing at full strength. If you reduce the brightness to 50%, the light intensity is lowered by inserting small pauses where the LEDs turn on and off for a very short time. When you reduce the brightness setting further, the pauses become longer, reducing the brightness further.

Controlling the speed of a fan (DC motor) in the CPU

As mentioned in the introduction, PWM can also be used to control the speed of a motor by regulating the
amount of power delivered. PWM speed control works by driving the motor with a series of on and off pulses and
varying the duty cycle of the pulses while keeping the frequency constant. It operates like a switch that constantly
cycles on and off, thereby regulating the speed of the fan.

Varying the width of these pulses can control the power applied to the motor and thereby varying the average DC
voltage applied to the motor’s terminals. By modulating the timing of the pulses, the speed of the motor can be
controlled. So longer the pulse is on, the faster the motor will rotate and the shorter the pulse is on, the slower
the motor will rotate. PWM operates like a switch that constantly cycles on and off, thereby regulating the speed
of the fan.

PWM has emerged as a solution for a wide variety of applications.

For a great range of LCD screens, visit: www.4dsystems.com.au/products/

Our Educational Primer Series presents a deep dive into the technical elements that bring together the world of 4D Systems and what we have to offer. You’ll find that this information series, developed with our experts and engineers, is the perfect place to power up your knowledge and take your understanding of our hardware and software to the next level. As always, feel free to reach out and get in touch. The best learning is interactive and we’d love to hear from you.

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What are intelligent display microcontrollers?

Have you ever wondered how your TV’s remote device controls the channel selector, speaker volume or colour adjustments of your TV? Or how your car engine maintains the desired fuelling and ignition. Or how the display unit keypad on your kitchen gadgets can execute a command that can turn the gadget on and off. What is that component that first gathers information then processes it and finally outputs a certain action based on the information gathered?

Microcontrollers are ruling our lives. There is hardly any electronic device that comes without at least one microcontroller, and usually there are several – there is one microcontroller for the user interface and another to control the motor and so on. Whether you’re driving your car, scrolling your computer screen, opening your garage door or heating a cup of water in your microwave oven, there is one component that is in common. Microcontrollers are widely used in various applications and different devices.

What are microcontrollers?

TI (Texas Instruments) engineers, Gary Boone and Michael Cochran, created the first microcontroller in 1971. As the name indicates, microcontrollers are single integrated circuits (IC) that are designed to control one task and run one specific program. These single-chip microcomputers are also known as embedded controllers because they are often embedded into the devices they control; like automatically controlled electronic devices such as smartphones, cameras, microwave ovens, washing machines, etc. The microcontroller can be seen as a minicomputer and has the same components a computer possesses – a processor unit (MCU), memory, serial ports and a few peripherals.

Advantages of a microcontroller:

Interfacing microcontrollers with intelligent displays

Many electronic gadgets that are frequently used in our day-to-day life integrate microcontrollers with an appropriate external device to perform many special tasks. This process of connecting devices together so that they can exchange information is known as interfacing.

Here data or information is transferred between the microcontrollers and interfacing peripherals. There are different types of interfacing peripherals like LCD displays, LEDs, ADC, sensors, keypads, microprocessors, motors, external memories and other devices. Interfacing has been able to resolve many complex glitches in circuit designing.

Intelligent displays have been around for a long time and many fields are adopting touchscreens and touch panels for applications with computer interfaces. As intelligent displays offer a more natural interaction that humans are used to, it also offers a great advantage over conventional tracking methods like a keyboard or mouse.

Display options for interfacing microcontrollers

A few of the intelligent display options available for microcontrollers are LCD, LED and OLED. An LCD uses a backlight made of either CCFL or LEDs. An LED display uses LED backlighting, and an OLED emits light to LEDs and does not require a separate backlight.

LCDs have been used to display output messages for many automated devices ranging from microwave ovens to washing machines to cell phones to televisions, to monitors and other similar devices. Liquid crystal, as the name suggests, is an organic substance that is found in both the liquid and crystal molecular form. Liquid crystals are placed between transparent electrodes, which are covered by polarisation filters. In the presence of an electric field, the liquid crystals tend to untwist which blocks the light coming through the filters. This makes the screen or part of it look dark. When the light passes through both filters, the screen looks lighter in colour.

LCDs are reasonably priced, easily programmable and they have no limitations of displaying special characters, graphics and multiple lines of information. It consists of a command register and a data register. While the command register stores the command instructions given to the LCD, the data register stores the data to be displayed on an LCD. A command could be any instruction like initialising, clearing the screen, setting the cursor posing or controlling the display.

Microcontrollers have played an important part in the technological revolution that has shaped our fastpaced lives. With the IoT (Internet of Things) rapidly increasing and with data constantly being gathered, microcontrollers are going to be a huge part of the future modern world.

For a great range of LCD screens, visit: www.4dsystems.com.au/products/

Our Educational Primer Series presents a deep dive into the technical elements that bring together the world of 4D Systems and what we have to offer. You’ll find that this information series, developed with our experts and engineers, is the perfect place to power up your knowledge and take your understanding of our hardware and software to the next level. As always, feel free to reach out and get in touch. The best learning is interactive and we’d love to hear from you.

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Avoiding burn-in on an intelligent display

Have you ever been bewildered by the ghost-like images or discolouration that appears on your phone screen, LCD monitor or any other intelligent display screens? You must have also noticed that these stubborn images are mostly found around the areas which have been constantly used or where images have been constantly projected, for example, navigation buttons on a phone or a channel logo on a TV channel.

This phenomenon is known as a screen burn-in.

So what is a burn-in? How is it caused? What should you do to avoid burn-in on an intelligent display?

Let’s find out.

What is burn-in?

Burn-in is a visible mark that is left on an intelligent display and remains there even if the content changes on the display. In other words, it appears as if the images were permanently burned-in onto the screen, hence the name burn-in. The burn-in could be in the form of an image outline or a text outline or a discolouration.

How is a burn-in caused?

The continuous display of static images over an extended period of time can create a permanent shadow or ghost of that image on the screen.

The common instances where you might find a burn-in on your intelligent display are:

• Channel logos from TV channels
• Navigation buttons or notification bar on your smart device
• Certain icons or banners on gaming console monitors

Let’s take a look at a more technical explanation for burn-in:

The images on an intelligent display are made up of thousands and thousands of picture elements or pixels. Each pixel is composed of three sub-pixels – red, blue, and green – which blend together to form various shades of colours. However, with time and prolonged use, the sub-pixels age and lose their intensity. Also, the sub-pixels have a varying lifecycle and do not age at the same rate. For example, the red pixels have the highest luminous efficiency, followed by the green and then the blue. Low luminous efficiency means that the blue pixels require more electricity to achieve the same level of brightness as the red or green one. The higher current causes the blue pixel to degrade faster, shortening its lifespan. This causes the blue pixel to not glow as brightly as the other two pixels. And this gradually shifts the colours of the screen in one area more than in other, leaving what looks like a ghost image or a discolouration behind.

How to avoid a burn-in?

Burn-in makes the intelligent display screen start to look really bad. Let’s take a look at the few steps you can do to avoid a burn-in on an intelligent display.

Lowering the screen timeout not only saves battery life but also prevents a screen burn-in. Also using a black or moving screensaver lessens the chance of potential image retention issues. Turn the display off when you’re not using the device.

Using a black wallpaper instead of bright wallpapers will not only solve the problem of burn-in but will also improve the battery performance of your device.

Change to an immersive full-screen mode if available. This will remove the top and bottom bars.

There are certain applications that can remove the navigation bar and add it back when needed.

Avoid using display filters that could accelerate a burn-in.

Once the burn-in has come into effect, it cannot be repaired. However, it can be slowed down and the visibility of the ghost images can be lessened. Take a note of the above-mentioned points to avoid burn-in on an intelligent display.

Once the burn-in has come into effect, it cannot be repaired. However, it can be slowed down and the visibility of the ghost images can be lessened. Take a note of the above-mentioned points to avoid burn-in on an intelligent display.

Our Educational Primer Series presents a deep dive into the technical elements that bring together the world of 4D Systems and what we have to offer. You’ll find that this information series, developed with our experts and engineers, is the perfect place to power up your knowledge and take your understanding of our hardware and software to the next level. As always, feel free to reach out and get in touch. The best learning is interactive and we’d love to hear from you.

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Cover Lens Bezel: What is it And Why Do You Need it?

Bezel used to be a term usually associated with the jewellery industry. There, the word is used to describe a groove that holds a gemstone or a watch crystal in its place. However, soon the word gained popularity, and it was widely used to describe other things too – such as the rim around gauges like the speedometer in a vehicle.

It did not take long for the word to enter the technology industry as well – the bezel is now a familiar term in the computer industry too. Here, it is used to refer the edge around the monitor or the front of a desktop case. And as mobile phones and other handheld devices gained popularity, bezel became a buzzword in the mobile industry as well. In the mobile industry, the term refers to the area of display surrounding the screen.

Bezel in the modern industries

A screen bezel is the area display surrounding the screen of your gadget – mobile, TV, tablet phone, touchscreen security systems and more. The bezel can be either plastic or metal. In simple words, the bezel is the border between the gadget’s display area and its frame. Although most of the earlier gadgets featured boarder bezel, most of the latest gadgets come with ultra narrow bezels. In many cases, they are so narrow that one feels the device doesn’t have one at all. A thinner bezel means more screen display area and vice versa.

Cover Lens Bezel

As technology evolved, most gadgets started offering more functions than they originally offered. For instance, mobile is no longer a simple tool to make and receive calls, but a device to send and receive emails, a camera, a news portal, handheld TV and more. Most other gadgets are now all in one tool offering a wide range of uses. As such, they have become more sophisticated across the globe.

It is not surprising then that bezel has made its presence known among these gadgets too. A cover lens bezel is basically a cosmetic feature adding to the aesthetics of the device and its screen. However, that doesn’t mean it is without any practical use.

Here are some of the benefits of the bezel:

One of the major benefits of the bezel is it provides additional protection to the system. Although most people take good care of their devices, they are likely to scratch or damage the screen in one way or the other. Sometimes, a drop could mean broken screens, rendering the device useless, especially if it is a touchscreen. A cover lens bezel can act as a safeguard against scratches and other pollutants like dirt, among others.

Lens covers are easy to replace than the actual screens themselves. Additionally, you can change them from time to time if you need a new look or better technology.

Although some people might think the lens cover bezel does not add any value to the devices that is not true. Well-fitted into the frame of the device, a bezel could save it from popping out of its place in case of a fall or other such impact. However, when you have a bezel around it, it would mean the screen is firmly held in its place even in the event of a fall.

A bezel improves the aesthetics of the device itself. If you are someone who loves add-ons, a lens cover bezel can be your best friend. It can be used to improve the overall look and feel of the system.

A bezel adds to the usability of the device because in its absence you are likely to activate a function on the screen accidentally.

Here are some of the benefits of the bezel:

4D systems offer state of the art intelligent display solutions covering a vast range of requirements. Whether it is smart LCD modules or TFT modules, we offer solutions to suit the needs of our users. All the gen4 display modules with resistive touch features come with bezels. These bezels not only offer a sleek cover to these display modules but also provide an easy way to mount the display modules into the enclosure. The display module is mounted on the bezel which provides a mounting solution into a panel while keeping everything firmly together.

For a great range of intelligent displays, visit:  www.4dsystems.com.au/products/

Our Educational Primer Series presents a deep dive into the technical elements that bring together the world of 4D Systems and what we have to offer. You’ll find that this information series, developed with our experts and engineers, is the perfect place to power up your knowledge and take your understanding of our hardware and software to the next level. As always, feel free to reach out and get in touch. The best learning is interactive and we’d love to hear from you.

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Normally you buy a phone or a touchscreen device based on the features it offers in terms of memory, battery life, camera, operating system and so on. However, you don’t give much thought to the touchscreen itself.

This could be because it is not always mentioned in the product description whether the touchscreen is capacitive or resistive. Additionally, both types of touchscreens are available on various devices across the electronics industry. So, what are the factors to consider before you choose one over the other?

Although to the layman the touchscreens look all similar at first glance, there are ways to differentiate them. On closer observation, you can find that the two are different. To put it simply, the most expensive tablets and smartphones you carry are more likely to feature a capacitive display. On the other hand, the older models in your collection would likely be the ones with a resistive touch display.

So, what is the difference between the two? The basic difference is the technology underlying the working of both screens. Let’s look at them closely.

Resistive touchscreen

The resistive touchscreen was one of the most common touchscreens used in industrial electronics. One of the main reasons for this was its cost-effectiveness. As the name itself implies, it works on the principle of resistance. In resistive touchscreens, two very thin layers of material are separated by a thin gap or air. PET film and glass are typically used as layers.

The upper and bottom layers of resistive touchscreens are lined with conductors such as indium tin oxide (ITO). The conducting sides are placed facing one another. However, there is a thin gap between the two layers that would prevent them from touching when the screen is not in use. So, when you press your finger or a stylus against the screen, it creates a change in resistance (an increase in voltage). The sensor layer detects this change, and the processor calculates the coordinates of that change and determines the position of the touch.

Advantages of resistive touchscreen

Capacitive touchscreens

Capacitive touchscreens, on the other hand, respond directly to the touch of your finger or an input device such as a stylus. Although they were invented almost a decade before the first resistive touchscreen, they became popular only recently.

Unlike the resistive touch displays that relies on mechanical pressure applied to the surface, capacitive touchscreen makes use of human body’s natural conductivity to operate. These screens are made of transparent, conductive material—usually ITO—coated onto a glass material.

As you touch the glass material with your finger, the static electricity stored in it transfers to the finger. The sensors in the processors use this change in electricity to determine the position of the touch. These sensors are very sensitive and can track even the slightest of touch, making capacitive touchscreens more receptive than resistive types.

Advantages of capacitive touchscreen

Disadvantages of capacitive touchscreen

Conclusion

From the above details, it is clear that capacitive touch displays are better than the resistive touch displays in more ways than one. Although they are costlier the benefits offered by capacitive touch displays outweigh the cost.

Furthermore, touchscreens are liable to develop cracks if they fall or come into contact with a hard substance. While the resistive touch displays cease to work even in case of a small crack, the capacitive touch displays can work even in the event of a cracked screen.

Armed with such practical information, you would be better off choosing a capacitive touch display device with a
high touch-sensitive screen that requires no effort to operate. Sharp pictures would be an added advantage.

For a great range of LCD screens, visit: www.4dsystems.com.au/products

Our Educational Primer Series presents a deep dive into the technical elements that bring together the world of 4D Systems and what we have to offer. You’ll find that this information series, developed with our experts and engineers, is the perfect place to power up your knowledge and take your understanding of our hardware and software to the next level. As always, feel free to reach out and get in touch. The best learning is interactive and we’d love to hear from you.

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The benefits of resistive touchscreens

Touchscreens have become an integral part of our lives. We use touchscreens when we type out a text message on our smartphones, when we scroll through a selection menu at a restaurant, when we need to get cash out from an ATM and when we’re using an elevator in a shopping mall. As technology begins to advance and become more and more interactive, touchscreens are bound to be found everywhere – from personal gadgets like tablets, laptops, printers and gaming consoles, to household appliances like cooktops and washing machines, and to public conveniences like car GPS systems, elevators and ticket vending machines to name a few.

In all these touchscreens, you must have noticed a difference between the texture of the touch panels, the response time, and the required pressure you need to apply with your fingers. This is because the underlying technology is different in different touchscreens. Based on the types of touch sensors used in the development of a touchscreen, there are a few types of touchscreens.

Resistive touch

Resistive touch is one of the most commonly used touchscreen technologies and was once the most prevailing type of touchscreen interfaces. It was the American inventor Dr. Samuel G. Hurst who founded the first resistive touchscreen in 1971. He called the sensor Elograph, after his company Elographics and he even received a US patent for his invention in 1975.

Let’s find out more about resistive touch, as well as the benefits of resistive touch.

What is resistive touch?

As the name suggests, resistive touch works on the basis of a pressure applied to the screen. A resistive touchscreen consists of several thin layers. The layers comprise of a bottom glass panel that is followed by two resistive circuit layers which are coated with electrically conductive thin metallic layers separated by a slim gap consisting of separator dots.

When pressure is applied on the screen with a finger or stylus, the outer resistive layer is pushed onto the inner layer. The two metallic conductive layers come into contact closing a circuit, causing a current loop and generating a change in resistance on both vertical and horizontal axis. The change is detected by the sensors located on the screen’s edges which in turn find out the exact location by using the horizontal-vertical axis coordinates to indicate the touch point.

Benefits of resistive touch

Let’s take a look at the benefits of resistive touchscreens and how they can be suited to a variety of applications.

Resistive touchscreens are less complex to make due to its simple structure and cost less when compared
to other touch technologies. The affordability of the resistive touchscreen explains their success in highuse
applications like PDAs and Internet appliances.

Resistive touchscreens have more sensors per inch than a capacitive touchscreen; the touchscreens can be touched to perform the desired action using a bare finger, gloved finger and stylus. This property makes resistive touchscreens the preferred choice in an industrial setting, where operators have to use gloves on the resistive touch panel. On the contrary, most of the capacitive touch screens will not work with gloves since the screen actually detects the electrical properties of the finger.

Resistive touchscreens are extremely durable and can be used in tough and harsh environments. The surface is resistant to liquids like water, oil and grease and other contaminants like dust and moisture.

Resistive touchscreens do not use much power.

Resistive touchscreens are very suitable for handwriting recognition. The touchscreen can come with a
built-in handwriting recognition capability.

Though a high degree of sensitivity can be a good feature for a touchscreen, it is not always an advantage in industrial environments. Resistive touchscreens do not respond to stray stimuli such as liquid spills and spatters that are common in an industrial unit that can cause the terminal to react unintentionally.

Most touchscreen technologies use glass plates as the outer touch layer. This is usually not allowed in the
food and beverage facilities as they have strict ‘no exposed glass’ policies. Resistive screens use a tough
polycarbonate outer layer that can contain the glass, even if the sensor screen is shattered by impact.

Resistive touchscreens have been widely used for many years and hope to remain a popular, well-proven and trusted solution in the future as well.

For a great range of LCD screens, visit: www.4dsystems.com.au/products/

Our Educational Primer Series presents a deep dive into the technical elements that bring together the world of 4D Systems and what we have to offer. You’ll find that this information series, developed with our experts and engineers, is the perfect place to power up your knowledge and take your understanding of our hardware and software to the next level. As always, feel free to reach out and get in touch. The best learning is interactive and we’d love to hear from you.

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Benefits of Capacitive Touch

Thanks to touchscreen technology, the days of clunky mechanical pushbuttons taking up valuable real-estate on our devices are gone. Smartphones with touchscreens have made our lives a lot easier, and so have many other devices that use touchscreen technology – such as satellite navigation devices, personal digital assistants, access control panels, tablets and touchscreen laptops to mention a few.

The latest in touchscreen technology uses the conductive touch of a human finger or specialised device for input. We’ll explore this in more detail.

How does Capacitive Touch Work?

Capacitive touchscreens are most commonly controlled by human touch. A finger touching the screen becomes an electrical conductor that stimulates the electrostatic field of the touchscreen.

The touch panel/glass has a capacitive layer with a static charge that shifts from the device to the finger. The system detects this reduction in charge and then processes the information to the program to tell the exact location of the touch, based on the many capacitor sensors on the screen.

Capacitive Vs. Resistive Touch

Before capacitive touch screens became available, the alternative to detect touch was using resistance. Resistive touchscreens have three layers – upper, middle and bottom layers. The middle layer consists of air or similar inert gas/substance. When pressure is applied on the surface of a resistive touchscreen device, it presses the upper and bottom layers together and the point of touch is calculated based on it.

However, capacitive touchscreens register touch through the electrical current transmitted to the human body, which means that they require less pressure to operate. That’s why it is possible to operate capacitive touchscreens simply by dragging the finger across the surface.

Benefits of Capacitive Touch

That brings us to the benefits of capacitive touch, which makes it a preferred choice to resistive touch.

A key feature of capacitive touchscreen technology is its strength and durability. These screens are more durable than resistive touchscreens because the fingerprint smudges and dirt, if any, won’t hamper the functionality.

A cracked screen is the most common damage suffered by touchscreen devices. However, in most cases, devices with a capacitive screen will continue to work, even with a cracked screen. This is because even when there are minor cracks, the device will continue to measure the electrical charge from the fingers and use the information to determine the point of touch. It means cracks don’t interfere with the function of a capacitive touchscreen device.

As capacitive touchscreen devices use glass layers, they come with exceptional picture quality. If you’re planning to watch movies, TV shows and videos on your touchscreen device, make sure you choose one with capacitive touch.

Perhaps one of the major benefits of capacitive touch is the ease of use. You need not learn anything – much of it is intuitive. It has never been easier to choose the correct button or menu from the screen. What’s more, on-screen buttons can be enlarged as needed. A clear view of the buttons and knowing where to touch to select the feature is all it requires to operate a capacitive touch screen.

Capacitive touch screens usually offer all-in-one solutions. It means that the device can be customised to suit customer needs. These touch panel controllers or touch monitors can save desk space as there is no need for a mouse or a keyboard. Everything is available on-screen, saving valuable space. Furthermore, the integration of data entry with the display saves space in the device used too.

Capacitive touchscreens use the human body’s electrical current to register the touch, and so, all they need is a light touch of the fingers. One need not put any pressure at all. That’s why it is easy to operate them simply by dragging the finger across the surface. This is opposite to the resistive touchscreens, which need a firm and slightly forceful press for registering the touch.

Capacitive touch screens can be of different kinds. A projected capacitive touch screen facilitates multitouch, which is a huge advantage for many kinds of touchscreen devices. Do you use the pinch zoom feature on your device? It is thanks to projected capacitive touch screen functionality. Gesture touches like this can enhance user experience and flexibility by allowing to get the most from the device.

The TFT LCD capacitive touch screens come with a sturdy glass top layer. It is easier to clean and is not impacted by dirt, rain, grease or dust. It makes capacitive touch screens very well suited for long term use.

Thus, we can see that there are several benefits offered by capacitive touch. With rapid changes and the introduction of advanced technologies, we can expect more features and benefits in the future.

To see the extensive range of screens from 4D Systems, visit: www.4dsystems.com.au/products/

Our Educational Primer Series presents a deep dive into the technical elements that bring together the world of 4D Systems and what we have to offer. You’ll find that this information series, developed with our experts and engineers, is the perfect place to power up your knowledge and take your understanding of our hardware and software to the next level. As always, feel free to reach out and get in touch. The best learning is interactive and we’d love to hear from you.

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How Does an LCD Work?

LCD screens are ubiquitous in a wide range of applications, from the giant high-definition screens you would find at a cricket stadium to the smaller displays you’d find in some of your personal gadgets such as digital watches, smartphones and laptop monitors. LCD technology also lies behind the displays of calculators, digital cameras, notification panels and many other electronic devices.

So what is an LCD? What are the components you’d find inside an LCD screen? How does an LCD work?

Let’s take a closer look.

What is an LCD?

The acronym, LCD, stands for Liquid Crystal Display. Liquid crystal, as the name suggests, is an organic substance that has two states – a liquid form and a crystal molecular form.

Friedrich Reinitzer, an Austrian botanist, first discovered liquid crystals in 1888. In the late 1800s and early 1900s, liquid crystal was only used for research purposes and in experiments. An American company, RCA Corporation, discovered that liquid crystals had electro-optical effects, i.e. when exposed to an electrical field, the liquid crystal could change from transparent to visible light to partially opaque. RCA recognised this value of liquid crystal and made the first experimental LCD in 1968. Since then, LCD manufacturers have found ways to improve the quality of LCD screens.

Basic Structure of an LCD

An LCD comprises of several layers. Starting from back to front, the parts of an LCD include the following layers:

• Reflective mirror
• Polarising film
• Glass filter
• Negative electrode plane
• Liquid crystal substance
• Positive electrode plane
• Glass filter
• Polarising film
• Display glass

The two layers of flexible polarising filters are set at a 90-degree angle to each other with a layer of liquid crystal solution lodged in between. The two glass sheets come with thin grids of transparent electrodes placed on their inside faces. Also, on the inner side of both the glass filters, a special polymer that creates microscopic grooves is applied. The grooves are aligned in the same direction as that of the polarising film. Once a coating of liquid crystals is added onto one of the filters, the grooves will cause the first layer of molecules to align with the filter’s orientation. Simultaneously, all the layers of the LCD components will twist and align until the uppermost layer is at a 90-degree angle to the bottom layer.

An LCD does not produce any illumination on its own and depends on an external source for light. If there is an external light source, it passes through the first filter, as it is polarised. The light then passes through each layer and is guided on to the next with the help of molecules. When the light passes through the liquid crystal layer, the molecules tend to change the light’s plane of vibration to match their own angle. As the light passes through the liquid crystal layer, it vibrates at the same angle as the final layer of molecules. If the angle of the final layer matches with the second polarised glass filter, then the light will pass through.

How Does an LCD Work?

When there is no current, the liquid crystal molecules are aligned parallel with the glass surface. The light entering through the front of the LCD hits the reflective mirror and bounces right back out. However, when a voltage is applied between the electrode planes, the liquid crystals tend to untwist and change their direction and turn vertical to the glass surface. This blocks the light coming through the layers that makes that area darker than the surrounding areas.

When the light passes through both filters, the screen looks lighter in colour, i.e. in different levels of grey. The motion of liquid crystal molecules together with the direction of the two polarisation filters can control the quantity of light transmission. This is the principle on which an LCD works.

For an LCD to produce a coloured image, coloured filters are used to generate red, green and blue pixels. A coloured dye is used in the liquid crystal and the liquid crystal molecule becomes a sub-pixel either generating red, green or blue light. Three of these sub-pixels together make a pixel and millions of pixels together form an image. Controlling the liquid crystals with voltage adjusts the colour and brightness of the image.

LCDs come with many advantages and are the preferred display medium for many applications. This is because LCDs produce a sharp image, use less power which translates to lower cost and less heat, can be made into larger sizes, is compact and thin, and more importantly, have a flat-screen.

There could be other technologies set to become the next big thing in displays, but for now, LCDs are here to stay.

To see the extensive range of screens from 4D Systems, visit:  www.4dsystems.com.au/products/