An LCD is a flat-panel technology used in computer monitors and televisions. In its most basic form, it is a shutter that allows light to pass through from fluorescent or light-emitting diodes (LED) backlights, explains Gary Clinton, vice president of Clinton Electronics Corp., Loves Park, Ill.
The light that is allowed to pass is filtered through colored red, green or blue pixels. The current applied to that pixel in the grid determines the amount of light allowed to pass through it. For example, for the color black, a pixel is closed, while for white, it is wide open.
LCD monitors differs from plasma ones, the other flat-screen technology, in their contrast ratio and handling of motion blur. According to experts contacted for this article, plasma monitors are not widely used in the security industry for several reasons.
One of the major reasons is that they are large and may burn into their screens static images that are held on them for long periods of time, such as in a fixed view from a surveillance camera. Their manufacturers continue to work on solutions.
Additionally, LCDs enjoy a significant edge compared with plasmas in the viewing angle they offer, maintains Lee Muratori, product manager for Toshiba America Information Systems Inc.’s imaging systems division, Irvine, Calif. He reports the viewing angle of a Toshiba LCD is 179 degrees versus a 155-degree viewing angle on a plasma display.
Cathode ray tubes (CRTs), the picture tube technology that has been in use for decades, have much larger power draws than LCDs. An LCD of similar size will draw about 40 percent less power than a CRT monitor, Clinton reports. “If you deploy several LCD monitors, the savings can be significant,” he asserts.
CRT monitors have larger footprints than LCD, Clinton explains. “LCDs are becoming less than one-inch thick,” he points out. “CRTs cannot be made any thinner than they are already, because they can only deflect the electron beam so much without losing the spot size in the corners.”
LCDs also are more environmentally friendly. As environmental concerns grow, so do worries about the impact of disposing of CRT monitors, Clinton says. Because of the high content of hazardous materials they use, CRTs are becoming increasingly difficult to discard, and many states now charge fees for the disposal of CRT monitors.
Longer life is another advantage of LCDs. CRT monitors typically have total usable lives of approximately 20,000 hours each, and they are not practical to repair. LCD panels are capable of lasting 10 years or longer if the backlights are replaced, Clinton estimates. Backlights are rated at 50,000 hours before reaching half-life, he notes.
In addition, LCDs offer higher resolutions that can resolve pictures up to 3,840 pixels by 2,160, Clinton reports. A color CRT is limited in resolution because it must shoot the beam through a shadow mask. A high-resolution CRT offers 1,280 pixels by 1,024.
“A black-and-white or monochrome CRT does not have to use a shadow mask, so the resolution is limited only by the spot size,” Clinton explains. “We have seen resolutions as high as 8 megapixels in monochrome CRTs.”
Stack up the AdvantagesOther advantages of LCDs over CRTs include all the following, Clinton says.
LCD monitors can provide brightness levels of 500 nits, while CRTs typically offer only 200 nits. LCDs produce less static. A CRT is essentially a capacitor, and will attract a charge for dust.
LCDs are highly stable because they are digital and suffer no loss of tuning. CRTs still rely on analog parts that need to be readjusted over time.
Finally, a CRT also will screen burn, while LCDs do not. “This is important to the security industry, because we tend to leave the picture in a static mode,” Clinton admits.
Despite all these advantages of LCDs, CRTs and plasma monitors have some plusses that LCDs do not, Clinton points out. Plasma displays, although lacking the punch of LCDs, are a little faster than most LCDs and offer superior contrast.
CRT monitors’ advantages over LCDs include speed and color rendering. The use of phosphor provides slightly better and more realistic color to the human eye.
Additionally, LCD monitors have difficulty displaying low-resolution video images, maintains Richard Becker, regional sales manager with the commercial closed circuit video equipment (CCVE) product division of Tatung Co. of America, Long Beach, Calif.
“However, more and more DVR and multiplexer products provide alternative digital signals to LCD products that overcome many composite video display issues,” Becker says.
Most LCD monitors used for the security industry are direct-view units and come in sizes ranging from 3 to 57 inches, Clinton says. LCD rear-projection uses a form of LCD technology, but it is popular only in control rooms where the lighting is dimmer and the screen sizes are large, he adds.
The Impressive Video WallFor video walls, digital light processing (DLP) technology is used. It also is employed a great deal in the consumer market for DLP rear-projection televisions, says John Kilgore, Western area sales manager for Toshiba America Information Systems Inc.’s imaging systems division.
“But we have applications perfect for video walls, where you can stack these cubes into different arrays or configurations, and they’re excellent for command and control room applications,” he says.
Having a small bezel or mullion, the outer frame separating the cubes, makes the picture on a video wall seamless. The key to a video wall, Kilgore says, is the CTU, enabling many, many images to be shown on the wall.
“But if someone wanted to do a large magnification image, they can do that as well,” he notes. “We do that with our DLP rear-projection cubes, but we can also do it with our LCD flat-panel monitors. The only true difference is that the bezel or mullion separating the frames is larger in an LCD monitor than a DLP cube, at present.”
Becker observes that typically all LCD products in the security industry utilize “FN” or TFT” display technologies, and projection techniques for LCD would be unusual.
“The biggest advancement in LCD products is the introduction of ‘touch screen technology,’” Becker says. “Another area of future LCD growth will be the digital signage display usage of LCD monitors. LCD’s future will offer several huge advancements in technology, such as OLED, a higher-resolution, thinner panel display.”
LCD monitors for security applications traditionally have been priced higher than their consumer-oriented counterparts. According to Clinton, premiums for security monitors range from 30 percent to 50 percent higher than the prices of TV and PC monitors.
Several factors contribute to this price premium. First, LCD security monitors must resolve a composite signal, not the standard VGA signal most consumer-market monitors are created to recognize.
Second, the consumer market is driven primarily by price and the latest market style trends. In comparison, although concerned about price, the security industry bases its purchases of LCD monitors on such considerations as long-term availability and reliability.
Third, the type of application often influences price. For example, LCDs with high contrast generally are needed for settings involving bright rooms, and these units will cost users more. “All these reasons add up to a more expensive monitor than you can go buy at the local computer store,” Clinton says.
Becker notes that popular sizes of LCD monitors, including 15-, 17-, 19- and 20.1-inch units, are priced similarly to equal sizes of color, high-resolution CRT monitors. “The larger the LCD display, the more expensive they become,” he says. “However, relatively speaking, LCD technology prices have come down substantially in the past few years.”
Sidebar: More Security Monitor DifferentiatorsA differentiator between television or computer monitors and ones designed for security is that monitors built for professional security applications do not have NTSC tuners, points out Lee Muratori, product manager for Toshiba America Information Systems Inc.’s imaging systems division, Irvine, Calif.
A professional LCD panel features video inputs, such as DVI or HDMI, he adds. “Some of your consumer lines have those inputs too,” he says. “But they have tuners, and professional units do not have tuners.”
Video monitors used for security share a lot of the same technology as TV monitors, concedes Gary Clinton, vice president of Clinton Electronics Corp., Loves Park, Ill. “We are dependent on the television and computer markets for many components,” he admits. However, the security market is almost non-existent to the giant LCD panel manufacturers, he adds.
The industry has been reduced to a handful of true manufacturers, and even if all security monitor makers worldwide banded together, total units produced would remain paltry compared to the overall television and PC market sales, Clinton insists.
“These plants are multi-billion dollar investments, and they must produce very high volumes in order to remain competitive,” he says of flat-panel manufacturing facilities.
“Depending on the application, we will use LCD panels designed for the television industry or the PC industry,” Clinton adds. “The similarities normally stop after the panel, though.
“A typical PC monitor will only have VGA inputs, and have a brightness of around 270 nits,” Clinton points out. ”This 270 rating is measured when the brightness is turned up, and in most cases, [results in] an undesirable appearance. You will always get something less than the stated brightness when you set the video to where you like it, so this 270 nits more than likely ends up being 200 nits.
“A 200-nit display does not have much room to lose brightness as it ages, and will need to be viewed from a [short] distance or darkened area,” he maintains. “Also, remember that most consumer displays will not offer warranties in commercial applications.”
One more difference can be found in the glass used in commercial versus professional LCD monitors, according to John Kilgore, Western area sales manager for Toshiba America Information Systems Inc.’s imaging systems division.
Consumer LCD panels tend to use what is called interplace switching, or IPS, glass, he says. LCD monitors used in security and other commercial fields typically feature vertical alignment (VA) glass.
VA glass is not as prone to image retention as IPS glass, Kilgore reports. “It’s not really burn-in, like with plasma, but it’s temporary image retention,” he says. “It should dissipate when you turn off the panel and let it cool down.
“It is really [dependent on] impurities in the glass and the heat of the panel, also,” Kilgore explains. That heat is produced from the backlights and may be dissipated by a fan on some LCD panels.
“LCD in the security industry focuses on display of composite video images,” points out Richard Becker, regional sales manager with the commercial closed circuit video equipment (CCVE) product division of Tatung Co. of America, Long Beach, Calif. “LCD products in general could have multiple technology capabilities, such as DVI, SVGA, S-Video and even HDMI. These functions are generally selectable from on-screen menus provided with LCD monitors.”