Also known as luminance is a measurement of the amount of light the LCD monitor produces and is a key component for perceived image quality of a monitor or display. Measured in candelabras (cd2) otherwise known as nits, brightness is particularly important in venues with varying ambient light where users are able to adjust display brightness to accommodate different light conditions. Displays with lower brightness can look soft and wash out especially at a distance. In general a higher brightness level is preferred.
When integrating a touch screen onto an LCD, the measured brightness from the user perspective is impacted by the light transmission characteristics of the touch screen. The better the transmission of the touch screen, more brightness is maintained from the LCD and the worse the transmission of the touch screen, less brightness is maintained. As a result, when choosing touch screen and LCD components a touch screen with a high transmission and an LCD with high brightness are preferred.
The color gamut is a measure of how broad a range of colors that can be expressed by a display. This is typically measured as a percent of the NTSC color space. Typical color gamut ranges are from 72% to 105%. The color gamut impacts the saturation of the colors presented as well as the tonal subtleties of an image.
The measure of the luminance of the brightest color (white) to that of the darkest color (black) a display can produce. Contrast ratio is an important image quality attribute that affects our ability to perceive both image brightness and image detail. Without a sufficient level of contrast, images will appear flat with blacks and whites taking a gray shade while finer image details are lost.
The total number of colors is a measure of how finely levels of color can be expressed by a display. This is dependent on the bit depth of each pixel. Typical LCD panels today have a 24 bit depth which delivers 16.8 million colors while some higher end panels have a 30 bit depth which delivers 1.07 billion colors.
DisplayPort is a digital display interface developed by the Video Electronics Standards Association (VESA). The interface is primarily used to connect a video source to a display device such as a computer monitor, though it can also be used to transmit audio, USB, and other forms of data.
The VESA specification is royalty-free. VESA designed it to replace VGA, DVI, and LVDS by creating a high performance standard. Backward compatibility to VGA and DVI by using adapter dongles enables consumers to use DisplayPort fitted video sources without replacing existing display devices. Although DisplayPort supports much of the same functionality as HDMI, it is expected to complement the interface, not replace it.
DVI or "Digital Video Interface" is a video connection standard created by the Digital Display Working Group (DDWG). Most DVI ports support both analog and digital displays. If the display is analog, the DVI connection converts the digital signal to an analog signal. If the display is digital, no conversion is necessary.
There are three types of DVI connections: 1) DVI-A (for analog), 2) DVI-D (for digital), and 3) DVI-I (integrated, for both analog and digital). The digital video interface supports high bandwidth signals, over 160 MHz, which means it can be used for high resolution displays such as UXGA and HDTV. You may find DVI ports on video cards in computers as well as on high-end televisions.
Refers to HDTV's or LCD panels that are characterized by 1080 horizontal lines of vertical resolution, and is commonly referred to as 1080p. Full HD assumes a 16:9 aspect ratio panel.
HDMI or "High-Definition Multimedia Interface" is a digital interface for transmitting audio and video data in a single cable. It is supported by most HDTVs and related components, such as DVD and Blu-ray players, cable boxes, and video game systems.
While other types of A/V connections require separate cables for audio and video data, HDMI carries the audio and video streams together, greatly eliminating cable clutter. Because HDMI is a digital connection, HDMI cables are less prone to interference and signal noise than analog cables.
LCD Technology Types
There are several types of LCD displays that deliver varying levels of viewing angle performance. Standard Twisted Nematic (TN) type LCD displays have viewing angles ranging from 120 to 140 degrees in the vertical and horizontal direction. The viewing angle is limited due to the physical structure of the LCD crystals that causes scattering of the light as it leaves the LCD. The LCD manufacturers have developed improved LCD constructions such as In-Plane Switching (IPS), Multi-domain vertical alignment (MVA), and Patterned Vertical Alignment (PVA) which greatly improve the viewing angle of the displays. These technologies deliver viewing angles of 178 degrees in every direction which deliver brilliant images at nearly every angle, however these technologies have varying levels of color performance.
Backlights used to produce the light used in the display to illuminate the LCD display. Edge-LED backlights are quickly becoming the new standard for LCD displays because they provide significant performance improvements over CCFL backlights such as providing more uniform brightness over time and typically reducing power consumption by 20 to 30% as compared to CCFL backlights. This enhanced efficiency not only reduces the overall usage cost of the display over time, but also aligns with today’s increasing environmental standards. Unlike CCFLs, Edge-LED's backlights are solid state devices allowing them orientation versatility unlike CCFL displays that are designed to be in either portrait or landscape orientation.
Open Frame Chassis Display
A touch display that is specifically designed to be integrated into a kiosk, table or other fixture. Open frame chassis are designed for 24/7 commercial applications, have a thin form factor, and are well ventilated to maintain ideal operating temperatures.
Power Supply Design
Displays typically require a power supply to convert the AC power to DC power and transform the input voltage to 12V, 24V or any other voltage that may be needed for the display to function. Depending on the display design this power supply can integrated into the design of the display (Internal) or be a separate component outside of the display (External). There are pros and cons to each approach and the decision depends on heat management, serviceability and cost.
The refresh rate of the display is a measure of the number of times in a second that the display presents the data that it is given by the video source. Typical refresh rates for LCDs are 60Hz, 120Hz or 240Hz. The faster the refresh rate the less perceived flicker and provides smoother, more fluid motion.
Display resolution is the measure of the horizontal and vertical pixels on the display. The density of these pixels and distance the user is from the display determines the perceived image quality of the display. Low resolution can lead to pixilation which causes the details of the image or text to blur and smooth lines to become jagged.
Thermal management refers to the additional engineering required to keep and maintain a touch display within a standard operating temperature range particularly when the display is integrated into a kiosk, tabletop or other fixture where airflow is restricted.
The Video Electronics Standards Association (VESA) has created industry standard guidelines for mounting patterns of displays. Based on factors such as display size and weight the standard defines the location, spacing and type of screw for mounting the display. This standardization allows manufacturers to create mounting brackets, bases and arms that fit all displays of similar sizes.
Video Response Time
The refresh rate of the display is the time it takes the liquid crystal to go from one value to another. This was typically measured the time to complete a full black to white transition but has more recently been measured through grey to grey transitions. Typical response times for LCD's are 8 to 16ms for black-white-black and 2 to 6ms for grey-to-grey. The faster the response time the less blur there is through video transitions.
VGA or "Video Graphics Array." is the standard monitor and display interface used in most PCs and monitors. The VGA standard was originally developed by IBM in 1987 and allowed for a display resolution of 640x480 pixels. Since then, many revisions of the standard have been introduced. The most common is Super VGA (SVGA), which allows for resolutions greater than 640x480, such as 800x600 or 1024x768. A standard VGA connection has 15 pins and is shaped like a trapezoid.
A measure of the maximum angle at which a display can be viewed with acceptable visual performance by one or more users. When displays are viewed off-axis, colors can begin to appear washed out, inverted or experience significant drops in brightness. Touch displays with wide viewing angles (170° to 178°) are preferred as they maintain high image quality at extreme angles and become essential with multiple users interacting across the entire display.