Video monitoring technology continues to evolve at an amazing pace. Just consider the variety of new broadcast and production monitors that were announced and demonstrated at NAB this year, including the debut of a number of 3-D products. It’s no surprise that 3-D was among the top themes at the show. “Avatar” is now the highest-grossing film of all time, several new 3-D consumer HDTVs were introduced this spring, and analysts are predicting that up to 80 million 3-D TV sets could be sold by 2015. Coverage of 3-D at the conference involved all aspects of 3-D, including cameras, post production, distribution and displays.
LCD monitors have now displaced CRTs as replacement (and new) products in video facilities; some even exceed CRT capabilities. Plasma panels have found a home meeting the requirements for large displays. New technologies continue to advance performance. This month, we’ll examine new technologies available in video displays.
OLED becomes a reality
OLED displays, only recently a laboratory curiosity, are now practical, and they are becoming available for professional use. The displays use organic LEDs as the light-emitting pixel elements, and they are different from ordinary LEDs in that they are composed of layers of organic semiconducting material, i.e., they are based on carbon rather than silicon. (Some OLED display backplanes are built from silicon as well.) In OLED screens, an applied voltage transports electrons and electron holes into the emissive layer. (See Figure 1.) Light is produced when the electrons and holes recombine.
The advantages of OLEDs include fast response times, broad color reproduction, high brightness, high contrast levels and deep black levels; contrast ratios of over 1,000,000:1 have been achieved. The displays obviate the need for a cold cathode fluorescent lamp (CCFL) or LED backlight unit, can have a lower costs in mass production (due to a simpler manufacturing process with fewer components) and offer a more “green” manufacturing process; recycling is no more onerous than processing glass.
While OLEDs historically have had lower lifetimes than LCD/CCFL or plasma panels (typically 60,000 hours for 50 percent brightness of a blue OLED device), power reduction strategies and “pixel orbiting” options can offset the risk of burn-in. Meanwhile, the lifetime and efficiency of the devices continue to improve to the point where we can expect practical 42in to 60in displays in the next five years.
3-D displays are now entering professional service as well. In consumer electronics and theatrical applications, displays generally use one of three technologies: filtering, shuttering or autostereoscopy. With filtering, the left and right images are orthogonally filtered with corresponding passive eye wear. Filtering comes in two varieties: polarization (either linear or circular) and narrowband color separation (not to be confused with the two-color anaglyph process). With shuttering, the left and right images are time-multiplexed and viewed through active synchronized eyewear. Autostereo applications remove the need for glasses and are usually realized with a diffuser/lenticular screen or a “parallax barrier” system using a series of vertical slits. For professional applications, 3-D monitors usually incorporate either polarization or shuttering.
A sampling of products seen at NAB
In addition to OLED and 3-D technologies, manufacturers continue to improve the performance of LCD displays. For example, Dolby may have just crossed the performance barrier of CRTs. At NAB, the company unveiled a 42in LCD reference monitor that accurately reveals true and deep black levels with higher contrast across the entire color spectrum. The Grade 1 monitor uses an RGB backlight unit with LEDs that are modulated individually on a frame-by-frame basis. The LCD panel is also modulated in real time as part of a dual-modulation process. The combination of technologies produces an extremely deep black level for an LCD panel. The unit can be used in darkened and well-lit rooms, and screen brightness can reach 600nits.
Other key features of the monitor include extended dynamic range, such as that of digital cinema cameras; DCI/P3 (digital cinema) color gamut support; color accuracy across all luminance levels; and the ability to emulate various display devices. Applications include high-end post-production houses and broadcast quality control.
TVLogic showed two 15in OLED monitors, one of which provides 3-D monitoring by means of a shutter glass display. Designed for color- critical visualization for film and broadcast production, the monitors feature 1366 x 768 resolution, 3G-SDI 1080p 4:2:2 10-bit support, SDI/HDMI 10-bit support, dual-link 4:4:4 mode, waveform monitors and 1:1 pixel mapping modes for SD/HD. The 3-D monitor also features 3-D left/right channel blocking.
TAMUZ introduced two OLED rack monitors at NAB. One is a multiscreen monitor equipped with four 4.3in (16:9) OLED displays built into a 2RU monitor bridge. These OLED monitors offer CRT-like viewing angles, direct 3G/SD/HD-SDI inputs and 1080p60/50 support. The products provide a stated contrast ratio of over 100,000:1 and support multiple color spaces. The panels are also said to offer more than 30,000 hours of life. The other product is an OLED audio/video monitor with analog and SDI inputs and outputs, and built-in speakers.
Sony showed an OLED display panel that delivers high-contrast, high-color images, even in ambient light. The 7.4in high-resolution (960 x 540) portable monitor can be used in 3-D camera rigs with its horizontal/vertical flip mode, and it can be outfitted with a viewing hood, carrying handle and connector protector. An anti-reflective coating provides protection from scratches and enables a high transmission of the OLED output, keeping picture brightness high while minimizing ambient light reflection. The monitor is equipped with a feedback system, which monitors the emitted light output and automatically adjusts the white balance. Sony also announced two new 3-D monitors featuring circular polarization in 42in and 24in sizes. These models offer proprietary color matching, full HD resolution and wide viewing angles. The monitors can be used to view 2-D content as well.
Panasonic also showed a new 3-D LCD video monitor. This monitor uses a 25.5in 1920 x 1200 LCD in-plane switching (IPS) panel that can display in 3-D using passive polarized glasses. To accommodate various 3-D signal formats, the unit supports dual SDI inputs and three types of 3-D video: simultaneous (dual SDI), line-by-line and side-by-side. These formats have emerged as ways of interfacing 3-D video signals. (See Figure 2.) In the first, two full-bandwidth pictures are relayed. In the second, each picture is decimated vertically, each successive line is alternately transmitted, and the two images are sent in one channel. In the third, each picture is downsampled horizontally, and the two images are sent in one channel.
New display technologies are appearing in combination monitor-processor units, too. Wohler showed a rack-mounted modular SDI-centric audio mixer and router at NAB that combines dual 4.3in OLED displays with loudness metering and control, and audio routing and mix controls. The use of OLEDs in such a unit brings the advantages of low cost and wide viewing angles to this type of application.
With an increasing number of products from second- and third-tier manufacturers, the field will become filled with products ranging from the excellent to the mediocre. What’s the solution? Set out your specifications, and then get your hands on a demo unit. You can always make a better decision after seeing it in operation in your particular application.
Editorial note: As this column does not engage in product reviews, those described here are intended to illustrate new emerging technologies. For that reason, model numbers and pricing are not discussed. The astute reader can get further information about the products from the manufacturers.
Aldo Cugnini is a consultant in the digital television industry.
