Flat Screen Display Technologies: Plasma, Electroluminescent, and Touchscreen

Flat Screen Electroluminescent Display

This is a type of flat-screen display based on the electroluminescent effect. This effect involves the non-thermal conversion of electric energy into light. Light is generated by striking a phosphorescent material with high-energy electrons.

Benefits:

• Excellent viewing angle
• Excellent brightness
• Quick response

Disadvantages:

• Low contrast
• Monochromatic
• High cost
• High power consumption

Flat Plasma TV

In flat plasma TVs, light is emitted by a phosphor excited by a plasma discharge of noble gas. This technology involves applying a high voltage between two electrodes, generating a gas discharge. After colliding with a phosphorescent material, light is emitted. The term "plasma" refers to the ionized gas during discharge. These displays are flat.

Advantages:

• Perfectly thin and light screens
• Low power consumption
• Available in large sizes
• Excellent viewing angle

Disadvantages:

• High cost
• Burn-in issues with static images

Touchscreens

Touchscreens use a sensor attached to the screen that determines the coordinates of a touch. The sensor uses a controller and control software. There are five types, differentiated by the method used to detect the position.

Resistive Touchscreens

Resistive touchscreens are popular for their low cost and versatility. They are suitable for:

• Point of sale terminals
• Medical monitoring devices
• Process control systems
• Industrial hand tools
• Portable communication devices

Technology Used:

Composed of a flexible top layer and a flexible bottom layer separated by a few points of isolation. The inner surfaces of the layers are covered by a transparent metal oxide. Applying a voltage to one layer forms a gradient along it. Pressing the flexible layer forces electrical contact between the two layers, allowing the voltage to be measured across the contact zone.

Advantages:

• Low cost
• Highly industrialized
• Can be used with any type of blunt pointer
• High resolution
• Low power consumption

Disadvantages:

• Reduced light transmission
• The front layer is made of plastic

Capacitive Touchscreens

Capacitive touchscreens are used in:

• Information kiosks
• ATMs
• Gaming machines

Technology Used:

Comprising a sandwich of glass layers. The outer side is covered with a transparent metal oxide. A voltage is applied to the corners of the screen, creating a uniform electric field. When a finger touches the screen, it generates a current flow that produces a voltage drop. The voltage drop is measured to determine the position of the contact point.

Advantages:

• Better light transmission
• Good resolution
• More robust, as there are no moving parts

Disadvantages:

• Requires the use of a finger or a conductive pointer
• Requires frequent calibration
• Difficult to industrialize
• The effects of screen abrasion affect performance
• High cost

Infrared Touchscreens

Infrared touchscreens are used in applications that require large screens.

Technology Used:

Based on the interruption of a beam of light to register the touch. The screen is surrounded by a frame that has infrared sources on opposite sides, creating an array of light beams on the screen. When a pointer touches the screen, it interrupts the light beam, causing a drop in the signal generated by the photoreceptor.

Advantages:

• Total light transmission
• Good accuracy

Disadvantages:

• High cost
• Parallax problems
• Accidental activations
• Low resolution
• Protects the surface of the graphic display

Surface Acoustic Wave Touchscreens

Surface acoustic wave touchscreens are suitable for applications including medical monitors or point-of-sale terminals.

Technology Used:

Uses ultrasonic transducers to generate surface waves that are transmitted through the glass surface and are received by a series of sensors located on the opposite side. When a pointer touches the screen, it absorbs some of the acoustic wave energy. The receiver measures the changes in the amplitude of the received acoustic wave to detect the position of the touch.