Capactive VS Infrared Interactive Dispaly Things You ...

Table of Contents

• CAPACITIVE TOUCH
• INFRARED TOUCH

The technology behind interactive touch screens is continually evolving. A major advancement has been the transition from infrared touch to capacitive touch technology.

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Understanding the differences and advantages of Infrared touch technology versus Capacitive touch technology will assist you in selecting the ideal touchscreen for your needs.

Capacitive technology is the predominant type of touchscreen available today. Even if you aren’t familiar with the name, you’ve likely interacted with a capacitive device. From smartphones and tablets to gaming consoles and smart home appliances, numerous touchscreen devices utilize this technology. On the other hand, infrared touchscreens are less prevalent than capacitive screens; however, they are gaining traction and are worth consideration for potential buyers.

CAPACITIVE TOUCH

Capacitive touchscreens work by applying a uniform electrostatic charge to the top layer of the screen. The human body, being a conductor of electricity, absorbs some of this charge upon the user touching the display, allowing the device to register touch commands.

This technology exhibits high sensitivity and accuracy. The glass surface is extremely durable, ensuring it remains functional even in demanding environments like classrooms.

INFRARED TOUCH

Infrared touch screens differ as they do not use an electrostatic charge to identify touch. Instead, they utilize a combination of light-emitting diodes (LEDs) and sensors. In this technology, LEDs are strategically placed to emit light towards corresponding sensors. Touching the screen interrupts the LED light path in that area, enabling the device to register the touch input.

This technology operates by employing an embedded overlay of infrared beams across the screen's perimeter. When a touch occurs, such as from a finger or stylus, it will be recognized as a touch point by the device.

Both IR and capacitive technologies represent distinct approaches to touchscreen functionality. IR technology employs a grid of LEDs and sensors to detect touch, while capacitive relies on a uniform electrostatic current.

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With nearly 20 different technologies surrounding touch panels today, selecting the right one can pose a challenge. The myriad of end products that utilize touch panels for user navigation demonstrates the evolution of technology, but understanding how these touch panels function is crucial to making an informed decision.

This buyer's guide aims to provide an overview of the current state of touchscreen technology and the criteria necessary for selecting the most suitable touch technology for your application.

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Choosing the Right Touchscreen for Success

A touchscreen serves as a human-machine interface, activated by user touch through a stylus or fingers on the specified display area. This interface can yield an independent x-y coordinate system calibrated to the display matrix. The device computes the touch point's location using x-y coordinates. This interaction allows users to engage directly with displayed information without relying on a mouse or keyboard.

Touch input provides immediate audio and/or visual feedback to confirm actions. Touchscreens are prevalent in various devices such as smartphones, gaming consoles, personal computers, touchscreen televisions, tablets, and electronic voting machines. They are commonly employed in public information kiosks, industrial control systems, military displays, and interactive video systems.

Touchscreen sensors and firmware have been provided by numerous aftermarket system integrators, diverging from traditional display or chip manufacturers. Companies globally have embraced touchscreen technology as a sought-after user interface component, integrating it into their core product designs.

Ideally, touchscreens should possess the following characteristics:
- They should not compromise display image quality when layered on top.
- The resolution ought to match that of the video display.
- Activation should remain effective regardless of the stylus size or whether the user is wearing gloves.
- Positive tactile feedback must be delivered upon interaction.
- The architecture should support modularity and integration with other input devices.
- Human perspectives should be considered, including ergonomics and cognitive psychology.
- The screens should accurately select touchpoints to minimize unintended selections.
- They should resist adverse environmental factors like dust, moisture, and chemicals.

At present, no touchscreen technology embodies all of these ideal features, leading to compromises based on specific applications and environments. The touchscreen interface is becoming increasingly necessary in modern electronic products.

Deep Dive into Touchscreen Technologies

Various touchscreen technologies utilize distinct methods for detecting touch: resistive, capacitive, projected capacitive, scanning infrared (IR), and surface acoustic wave (SAW). Careful evaluation is essential in selecting the appropriate touch technology for particular applications. All touchscreens typically consist of a touchscreen overlay and an information-processing controller.

Resistive technology. The five-wire resistive touchscreen is among the most utilized touch technologies today. It consists of a glass panel coated with thin conductive and resistive metallic layers separated by a small gap. Touching the screen causes the layers to come into contact, triggering a change in the electrical field, which is detected by the computer to identify the touch point. These screens are often the most affordable but typically offer image clarity of only about 70% to 85%.

They can be activated using any rigid object, including fingers, styluses, or gloves, allowing for tactile interaction. These screens resist surface contaminants like dust and oil.

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Key benefits of resistive touch technology include low costs and power consumption. There are three variations: four-wire, five-wire, and eight-wire.

Surface-capacitive technology. This technology operates by measuring electrical current. A protective cover is placed over a transparent electrode film atop the glass substrate. When voltage is applied from the corners, any contact with the surface alters the current, indicating the touch point to the controller. Most often, this technology is applied in the gaming industry, achieving light transmission of 80% and above.

This approach offers superior image clarity, excellent scratch resistance, and immunity to contaminants. Capacitive touchscreens can be activated by human skin or a stylus that carries an electrical charge.

These screens are susceptible to electromagnetic interference (EMI/RFI) from surrounding environments, which could hinder performance. They generally exhibit moderate durability and limited resolution.

Projected capacitance technology. Projected capacitive technology is a standout in the market. This method is employed in devices like iPhones and iPads, projecting an electronic field through the glass surface. Changes on the surface generate detectable electrostatic fields, enabling the identification of touch points.

This technology supports multi-touch capabilities, allowing for two to ten touch points simultaneously, contingent on the controller type used. It offers exceptional lighting and over 80% light transmission but tends to be higher in cost compared to other options.

Additionally, touch recognition may not function correctly when using gloves.
IR grid technology. Widely used in touch panels, this technology involves IR LEDs and sensors located around the bezel's perimeter. LEDs send beams that create a light grid across the screen. If this grid is disrupted, a touch point is registered by the controller.

However, performance can be influenced by environmental factors, including water, rain, and surrounding light interference, potentially leading to operational issues due to dust and oil accumulation. It is generally more expensive than alternative technologies.

SAW touchscreen. This technology uses a structure-borne sound wave that spreads across the surface in two dimensions. The receiving transducer identifies the touch point and conveys that information to the controller.

SAW touchscreens boast exceptional image clarity, suitable for displaying intricate graphics. They can be activated by fingers, gloved hands, and soft-tip styluses.

However, SAW panels can be quite costly, particularly when exposed to hard contact that might trigger false touches. Solid contaminants may create non-responsive areas until they are cleaned off.

Optical touchscreens. This more recent advancement relies on two line-scanning cameras at the screen corners, complemented by IR backlights positioned within their view. This design has gained popularity for large units, presenting scalability, versatility, and affordability while maintaining 100% light transmission with minimal calibration needed.

Near-field imaging touchscreens. This newly developed technology includes two touchscreens that register contact through electrostatic field disturbances caused by fingers, gloves, or conductive styluses. It offers excellent durability, making it well-suited for industrial applications in challenging environments.

Considerations for Purchasing Touchscreen Panels

The choice of a touchscreen panel hinges on specific application requirements and user demographics. For example, a classroom touchscreen will have different specifications compared to a panel in an industrial setting, impacting choices concerning size, response time, environment, and cost.

Key performance specifications to consider when evaluating touchscreen displays include:

Touch type. Each touchscreen method has its unique benefits and drawbacks. Choosing the right one necessitates balancing positives and negatives. The projected capacitive type is well-suited for rugged, industrial, and outdoor settings, whereas IR touchscreens may not be the best fit. If image clarity is paramount, IR can be a preferable option despite its higher cost.

Screen size. Touchscreen monitors vary widely in size, typically ranging from small (under 8.9cm) to large (up to 2.5m). The most common sizes fall between 38.1cm to 48.2cm (15-inch to 19-inch) and 81.2cm to 1.1m (32-inch to 42-inch) for extensive control rooms.

Accuracy of touch. This involves reliable performance in noisy environments (from chargers or displays) that may interfere with touch accuracy; it’s vital to ensure users can accurately select targets and prevent accidental selections.

Touchscreen resolution. This refers to the number of touch-active points available, impacting precision and selection errors—higher resolutions facilitate greater pointing effectiveness. Display pixel density (HD, full-HD, etc.) is also an important factor to consider.

Response time. The faster the response from touch to action, the better user experience. Evaluated in milliseconds (ms), ideal latency should ideally be below 10ms. For reference, SAW touchscreens provide rapid response times around 10ms, compared to IR, which has around 20ms.

Transmission/clarity. As touchscreens overlay displays, some light loss may occur affecting image clarity. However, IR touchscreens do not have an overlay, yielding clarity ratings of 95% to 100%—the best among technologies. Resistive types fall short in this regard.

Life expectancy. With extended use, performance degradation over time is expected. Generally, IR touchscreens last around five years, while capacitive types have a shorter lifespan of about two years.

Resistance to environmental factors. The covering layer must be robust enough to withstand scratches, and sealing must prevent elements like water and chemicals from entering the device.

Ergonomics. Appropriate design of touchscreen interfaces considers cognitive psychology and user experience, encompassing touchpoint placement, size, sequence, and visual elements.

Deployment environment. The choice of touchscreen should reflect its intended use; outdoor or harsh settings require those designed to resist dust and temperature variations.

Nidhi Kathuria, a senior application engineer at EFY Labs in New Delhi, shares insights based on extensive experience within the field.

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