At a press event in New York City, Insight Media had a chance to see the latest demonstration of the High Dynamic Range (HDR) LCD-TV developed by Dolby Labs (San Francisco, CA; www.dolby.com) and SIM2 (Pordenone, Italy, www.sim2.it). On display was the first unveiling of a 46" demonstrator, but both companies were clear that no commercialization plans have yet been set. Instead, the demo is designed to show what the technology can do and to gather feedback on commercialization prospects for the display.

Chris Chinnock
Senior Analyst and Editor
for Insight Media

Since the last showing at CES the brightness of the display has been increased, now offering 4000 nits of peak white brightness (measured as ¼ of the surface area surrounded by black). This increase was mainly the result of improved LED thermal management that allows the LEDs to be driven even harder.

The backlight unit is a direct type with a standard film stack, noted Domineco Toffoli, Director, Professional Systems Business Unit, SIM2. In addition, it features 1838 standard white LEDs (sourced from CREE) that can each be modulated in luminance. The heart of the HDR technology is an algorithm that maps the basic luminance of a scene to these LEDs in the backlight. This dynamic backlight image is then further modulated by the LCD panel to create an effective expansion of the dynamic range of the LCD. The result is an LCD display that can provide much brighter whites and much darker blacks at the same time, compared to conventional LCDs - even those with dynamic backlights. While some LCD BLUs contain 64 or 128 dimmable zones, Dolby and Sim2 carry this to the ultimate extreme allowing each LED to be individually dimmed. It is in essence a 1838 zone dimmable BLU.

The demo is clearly impressive, but not perfect. Some of the scenes were actually too bright and some of the darker scenes still did not provide a lot of detail within the darker parts of the image. Dolby’s Guido Voltolina said this was the result of the 8-bit limitation ion the original content. He noted that Dolby has developed a still image capture technique that acquires multiple images of the same scene at different exposure levels, to create a wide dynamic range photo that exceeds 8-bits. This shows up very well on their HDR display, but is not a practical method for conventional photography or video.

The 46" panel has 1920×1080 resolution and offers more than 95% luminance uniformity over the panel. The standard white LEDs can achieve 92% of the NTSC color standard, but Dolby’s Business Line Director for Image Technologies, Bharath Rajagopalan, said they are looking into RGB LEDs too, but more as a latter stage development since managing the W-LEDs is difficult enough.

Under the collaborative agreement that Dolby signed with SIM2, Dolby agreed to supply its HDR technology while SIM2 was responsible for developing the LED BLU, drive electronics, the BLU thermal management systems and the industrial design of the LCD-TV. The goal was to show the efforts of this work in Q1′08 and they got it done just under the wire (March 31st).

The thermal management system in particular is clearly a development platform and not one that is suited for mass production. It consists of an aluminum plate that holds the LEDs on their PCB board, along with some special thermal management interface technology to facilitate heat transfer to the aluminum plate. In addition, various cooling technologies can then be attached to the aluminum plate at various points to test the effectiveness of the technology and airflow combination.

The LEDs from CREE each can consume a maximum of 480ma. You can do the math, but with 1838 of them, SIM2’s Senior Engineer for the R&D department, Marco Rampin, said the maximum power usage was about 2,000W. These LEDs offer about 80lm each with an efficiency of 80lm/W, so power consumption will go down as efficiency improves, but we are still talking about a lot of power. This is probably a lot more than any consumer would dare to consider, which could be a problem for SIM2 whose main customer base is the high-end home theater enthusiast.

The LED drivers are from Texas Instruments (TLC5940) and each driver has 16 outputs grouped in parallel 4 by 4 to feed four LEDs. LED brightness is controlled by PWM (with up to 12-bit grey scale resolution). The BLU LED boards are then connected to the HDR processing board through an LDVS interface.

Incorporated into the design is a Xilinx Virtex field programmable gate arrays (FPGAs) chipset, recently approved by Dolby for HDR innovations. The Xilinx FPGA chipset enables the implementation of Dolby’s complex high-dynamic-range algorithms in the SIM2 display.

As for BLU lifetime, Rajagopalan said it would be longer than CCFL, but this is clearly a function of how hard the LEDs are driven and their thermal management system.

In addition to not discussing any commercial introduction, SIM2 was also ambiguous on the pricing. However, the good thing about the approach is the ability to create solutions that can potentially fit may price points. Want to hit a certain price point? - back off on the number of LEDs and accept a lower uniformity and brightness.

But the concept can also be taken the other way. Creating a digital signage display or medical monitor could be exactly the high value applications that will pay for the performance and pop this display can offer.