Audio Video News

Despite their popularity, LCD TVs have always had a problem with black level. Yesterday Dolby and SIM2 gave dazzled reporters a glimpse of how good black and dark colors could look on a flat-panel set. Unfortunately, this High Dynamic Range (HDR) tech was only a prototype, so it'll be awhile before you get to share the love.

While this event at Dolby's Manhattan office-theater wasn't the technology's first demo--it was previously shown at CES--this was the first exhibition of a new SIM2-developed 46-inch LCD panel with 1838 LEDs, or light-emitting diodes, substituting for the fluorescent backlight normally used in LCD TVs. The CES demo had used fewer LEDs.

In a darkened theater, the black level and color saturation were impressive. When the screen showed flowers as bright as flames, the black background seamlessly blended with the darkness of the room. But when I held my hand to my face, blocking out the bright flowers, I could see the black rectangle of the screen. The difference probably hinged on the action of the optic nerve--it was impossible to see the background when the flaming flowers were biasing my eyes, but blocking the flowers enabled my eyes to see more shades of black. My camera was able to barely discern the edges of the screen.

There was also live action video featuring car chases. While the brightness and contrast were way in excess of what a correctly calibrated set would display at home--my retinas were sizzling--this was after all a demo showing the extended limits of a new technology, and the images were potent.

The demo material running off a PC benefited from Dolby's proprietary video algorithms. Brightness was said to be 4000 cd/m2, vs. 450-600 for a normal LCD. HDR also includes dual modulation algorithms that modulate liquid crystals while dimming backlighting at the same time.

Following is a summary of technical details from the Dolby press kit:

General Features:
• The prototype is a 46-inch LCD with Dolby’s HDR LED backlight technology
  
• LCD panel provides a resolution of 1920 x 1080 pixels (Full HD), fitting a native 16:9 aspect ratio
  
• Brightness: greater than 4,000 cd/m2
  
• Contrast ratio: INFINITE! Full On / Full Off
  
• Step size: 16 bits of luminance
  
• Luminance uniformity: more than 95% through the LCD panel

  Prototype Detailed Technical data:

• 1,838 LEDs
  
• Each LED is powered by 500 mA and provides a luminous flux of 80 lm
  
• The LED drivers are Texas Instruments TLC5940
  
• Each driver has 16 outputs grouped in parallel 4 by 4
  
• Each driver feeds 4 LEDs
  
• LED brightness is controlled by PWM (with up to 12 bit grey scale resolution)
  
• The BLU boards are connected to the HDR processing board trough an LDVS interface
  
• The color resolution of the LCD panel is 8/bit color
  
• The HDR algorithm expands the signal from the source in 16/bit color
  
• A stream of 8 bit are sent to the LCD panel and the others 8 bit are sent to the BLU
  
• The total effect between the LCD and BLU is equivalent to 16 bit wide dynamic range display

See more detailed report in EETimes and Dolby press release. Also see pictures from press kit: the set, structural diagram, and circuit diagram.