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Frequently Asked Questions

1. What is LED?
2. What is an LED Backlight?
3. What is Surface Acoustic Wave Touch Screen (SAW)?
4. What is Capacitive Touch Screen?
5. What is Resistive Touch Screen?
6. What is Projected Capacitance Touch Screen?
7. What is eDP?
8. What is LVDS?
9. What is TTL?
10. What Is Display Resolution?
11. What Makes A Panel Night Vision Compatible?
12. I Have Already Determined The Panel For My Project But Need To Increase Brightness. What Are My Options?
13. How does EMI shielding work?
14. What Is Optical Bonding?
15. Can I Purchase A Service From AGD, But Buy The Components Myself?
16. Can AGD Help Me Find The Right Solution For My Project?



What is LED?
An LED, or Light Emitting Diode, is a semiconductor device that emits light when electrical energy is applied to it. It consists of a computer chip that is attached to a positive power lead and a negative power lead. The 'anvil' on the top of the negative lead holds one side of the chip and the 'whisker' on top of the positive lead holds the other side. The LED is encased in clear epoxy resin. LED advantages include compact size, low energy consumption, long lifetime, durability and environmental footprint.

What is an LED Backlight?
LED backlighting is most commonly used in small, inexpensive LCD panels. The light is usually colored, although white LED backlighting is becoming more common. LEDs are widely used as indicator lights on electronic devices and increasingly in higher power applications such as flashlights and area lighting. An LED is usually a small area (less than 1 mm) light source, often with optics added to the chip to shape its radiation pattern and assist in reflection. The color of the emitted light depends on the composition and condition of the semiconducting material used, and can be infrared, visible, or ultraviolet.

What is Surface Acoustic Wave Touch Screen (SAW)?
Surface acoustic wave (SAW) technology uses ultrasonic waves that pass over the touch screen panel. When the panel is touched, a portion of the wave is absorbed. This change in the ultrasonic waves registers the position of the touch event and sends this information to the controller for processing. Surface wave touch screen panels can be damaged by outside elements. Contaminants on the surface can also interfere with the functionality of the touch screen.
The Surface Acoustic Wave (SAW) technology is one of the most advanced touch screen types. The technology is based on two transducers (transmitting and receiving) placed for the both of X and Y axis on the touch panel. The other important element of SAW is placed on the glass, called reflector. The controller sends electrical signal to the transmitting transducer, and transducer converts the signal into ultrasonic waves and emits to reflectors that are lined up along the edge of the panel. After reflectors refract waves to the receiving transducers, the receiving transducer converts the waves into an electrical signal and sends back to the controller. When a finger touches the screen, the waves are absorbed, causing a touch event to be detected at that point.

Compared to Resistive and Capacitive technologies, SAW technology provides superior image clarity, resolution, and higher light transmission. Because the panel is all glass, there are no layers that can be worn, giving this technology the highest durability factor and also the highest clarity. Disadvantages of Surface Acoustic Wave (SAW) technology include the facts that the touch screen must be touched by finger, gloved hand, or soft-tip stylus (something hard like a pen won't work) and that the touchscreen is not completely sealable, can be affected by large amounts of dirt, dust, and / or water in the environment.

What is Capacitive Touch Screen?
A capacitive touch screen is coated with a material, typically indium tin oxide (ITO) that conducts a continuous electrical current across the sensor. The sensor therefore exhibits a precisely controlled field of stored electrons in both the horizontal and vertical axes - it achieves capacitance. The human body is also an electrical device which has stored electrons and therefore also exhibits capacitance. Capacitive sensors work based on proximity, and do not have to be directly touched to be triggered. It is a durable technology that is used in a wide range of applications including point-of-sale systems, industrial controls, and public information kiosks. It has a higher clarity than Resistive technology, but it only responds to finger contact and will not work with a gloved hand or pen stylus.

What is Resistive Touch Screen?
A resistive touch screen is composed of several layers. The most important are two thin metallic electrically conductive and resistive layers separated by thin space. When some object touches this kind of touch panel, the layers are connected at certain point; the panel then electrically acts similar to two voltage dividers with connected outputs. This causes a change in the electrical current which is registered as a touch event and sent to the controller for processing.

Resistive touch screen panels are generally more affordable but offer only 75% clarity (premium films and glass finishes allow transmissivity to approach 85%) and the layer can be damaged by sharp objects. Resistive touch screen panels are not affected by outside elements such as dust or water and are the type most commonly used today. The Nintendo DS is an example of a product that uses resistive touch screen technology.

What is Projected Capacitance Touch Screen?
Projected capacitance touch technology is a type of capacitive technology which involves the relationship between an XY array of sensing wires embedded within two layers of non-metallic material, and a third object. In touch screen applications the third object can be a human finger. Capacitance forms between the user's fingers and projected capacitance from the sensing wires. A touch is made, precisely measured, and then passed on to the controller system which is connected to a computer running a software application. This will then calculate how the user's touch relates to the computer software.

What is eDP?
The embedded DisplayPort (eDP) carries a display's multitouch data to the system processor. It also allows for increased battery life, and thinner, lighter devices. This new update was announced by VESA and consumes power more efficiently than LVDS.
eDP is a digital display interface standard put forth by Video Electronics Standards Association (VESA) since 2006. It defines a new royalty-free, digital audio/video interconnect, intended to be used primarily between a computer and its display monitor, or a computer and a home-theater system. The first version was approved in May, 2006, version 1. Version 1.1a was approved on April 2, 2007, and the most current version 1.2 was approved Dec 22, 2009.

What is LVDS?
Low-voltage differential signaling, or LVDS, is an electrical signaling system that can run at very high speeds over inexpensive twisted-pair copper cables. It was introduced in 1994, and has since become very popular in computers, where it forms part of very high-speed networks and computer buses. LVDS is a differential signaling system, meaning that it transmits two different voltages that are compared at the receiver. LVDS uses this difference in voltage between the two wires to encode information. The transmitter injects a small current, typically 3.5 mA, into one wire or the other, depending on the logic level to be sent. The current passes through a resistor of about 100 to 120 ohms (matched to the characteristic impedance of the cable) at the receiving end, and then returns in the opposite direction along the other wire. From Ohm's law, the voltage difference across the resistor is therefore about 350 mV. The receiver senses the polarity of this voltage to determine the logic level. This type of signaling is called a current loop. The small amplitude of the signal and the tight electric- and magnetic-field coupling between the two wires reduces the amount of radiated electromagnetic noise (and power lost to conductor resistance).The low common-mode voltage (the average of the voltages on the two wires) of about 1.25 V allows LVDS to be used with a wide range of integrated circuits with power supply voltages down to 2.5 V or lower. The low differential voltage, about 350 mV as stated above, causes LVDS to consume very little power compared to other systems. For example, the static power dissipation in the LVDS load resistor is 1.2 mW, compared to the 90 mW dissipated by the load resistor for an RS-422 signal. Without a load resistor the whole wire has to be loaded and unloaded for every bit of data. Using high frequencies and a load resistor so that a single bit only covers a part of the wire (while traveling near light speed) is more power efficient.

What is TTL?
Time to live (sometimes abbreviated TTL) is a limit on the period of time or number of iterations or transmissions in computer and computer network technology that a unit of data (e.g. a packet) can experience before it should be discarded.

What Is Display Resolution?
The display resolution of a digital television or display device is the number of distinct pixels in each dimension that can be displayed. It can be an ambiguous term especially as the displayed resolution is controlled by all different factors in cathode ray tube (CRT) and flat panel or projection displays using fixed picture-element (pixel) arrays. One use of the term "display resolution" applies to fixed-pixel-array displays such as plasma display panels (PDPs), liquid crystal displays (LCDs), Digital Light Processing (DLP) projectors, or similar technologies, and is simply the physical number of columns and rows of pixels creating the display (e.g., 1920 x 1200). A consequence of having a fixed grid display is that, for multi-format video inputs, all displays need a "scaling engine" (a digital video processor that includes a memory array) to match the incoming picture format to the display.
What are the advantages/disadvantages between "glossy" and "matte" screens?
Each screen has its advantages and disadvantages, which is why manufacturers waver between the two. Glossy screens produce an image that's generally regarded as "richer." Essentially it means there is more color depth and vibrancy. On the downside, glossy screens are more susceptible to glare, reflecting light from windows and light bulbs. And they tend to show fingerprints and smudges more readily, especially when they are off.

Matte screens tend to handle glare better, due to a polarized coating over the glass that diffuses ambient light. A side effect of the matte finish is a slight blurring, reduced contrast and a narrower viewing angle. Which is better is a matter of environment and personal preference. If the screen is in a room that's generally dark, consider a glossy finish. In a controlled environment it offers a best-case picture. But I wouldn't be too afraid of a matte finish. Most of us use our screens in mixed light where the minor qualitative difference is offset by the anti-reflective benefit.

What Makes A Panel Night Vision Compatible?
Night vision filters are primarily used in military display and lighting applications. NVG, night vision goggles, or NVIS night vision imaging systems must be used in an environment free of near infrared NIR noise, as it would interfere with the sensitivity of the NVG. NVC or night vision compatibility is achieved only when the design of the lighting equipment allows for the use with or without the NVIS, during day or nighttime.

I Have Already Determined The Panel For My Project But Need To Increase Brightness. What Are My Options?
PASSIVE---Passive enhancement mainly refers to optimizing the panel's film stack in order to achieve your max brightness without replacing, or altering any active components such as the backlight or backlight inverter or driver. These types of enhancement would increase the brightness while retaining the stock current values given in the panel's datasheet. This may also be used as a way to maintain the stock brightness levels and scale back the given currents to run using less power. In some cases NVIS filters could be added as a passive enhancement if stock dimming capabilities are sufficient.

ACTIVE---Active enhancement refers to the replacement, addition, and or alteration of active parts such as, backlights and controllers to increase brightness, touch screens, or anything that would alter stock current values of the panel, or increase the number of active parts and controllers. This would most commonly consist of the replacement of CCFL bulbs with LED rails, the addition of a touch screen, or the addition of NVIS fiber optic backlighting.

How does EMI shielding work?
Electromagnetic shielding provides the "immunity" for electronic components that are susceptible to EMI as well as prevents the same components from transmitting excessive interference to their surrounding environment.

What Is Optical Bonding?
Optical bonding refers to a protective glass that is glued in front of a display to enhance its readability where installed in high humidity outdoor environments. When a normal display is used in an outdoor environment, there are some factors that affect its readability. The most common one is "fog", or condensation, which forms on the inner surface of display's vandal shield. Another factor is the reflection of sunlight, which causes a mirror-image on the display. Both phenomenons can be solved by using optical bonding. Touch screens can also be optically bonded to the display.

Can I Purchase A Service From AGD, But Buy The Components Myself?
YES, AGD will provide integration services based on your specifications for your components just the same as if we were providing them for you. AGD can assist in your integration process for you whether or not you need parts sourcing.

Can AGD Help Me Find The Right Solution For My Project?
Given that we have all the requirements needed for your specific project, AGD from start to finish, can source the components you need, work hand in hand with you through the integration process, get your project into production and back to you for distribution as a complete "turnkey" solution.