Flat-panel TV is 25% brighter

Agilent has announced a colour management system for backlighting LCD flat-panel TVs that delivers 25% more brilliant colours than current fluorescent backlighting.

The colour management controller IC (integrated circuit) and colour sensor module combine to produce a complete hue (colour ) and intensity (brightness) control system.

The system works with high-power Luxeon red, green and blue LEDs from Lumileds Lighting, the joint venture between Agilent and Philips Electronics.

"For years, manufacturers have struggled with how to provide a sharper, more natural colour tone for their LCD TV displays," said Soo-Ghee Lee, vice president and general manager for the Optoelectronic Products Division in Agilent's Semiconductor Products Group. Now consumers watching flat-panel TVs will be able to see all colours of the rainbow brighter and more clearly."

The system provides a closed-loop optical feedback system and enables plug and play for OEMs and maintains a set colour point over the life of the display.

Initially, the primary application for this technology is to control RGB LED backlighting for LCD flat-panel televisions. This colour management capability may also be used to adjust the colour and brightness of mood lighting in homes and businesses, interior lighting, infotainment and instrument panels in automobiles and context-sensitive colours for signs and other types of displays.

Currently, most flat-panel LCD television displays are backlit using cold-cathode fluorescent lamps. While efficient, CCFLs gradually degrade in brightness and change colour with time, and offer a lifetime in the range of 15,000 to 25,000 h.

In addition, the CCFL light source only covers 75% of the colour space.

These RGB LEDs exceed 100% of the NTSC colour space, providing sharper, more brilliant colours. The use of LEDs also aids European manufacturers who are seeking to eliminate the small amount of mercury used in fluorescent backlighting.

The management system enables white backlighting (using the combination of red, green and blue LEDs with feedback control) and makes it possible to maintain constant colour and brightness over the lifetime of the display.

This level of control, combined with the increased colour spectrum, has not been possible until now.

The system consists of the HDJD-J822-SCR00 controller and the HDJD-S831-QT333 tri-colour photo sensor. The colour management controller is a CMOS mixed-signal optical feedback controller IC; the HDJD-S381-QT333 colour sensor is a monolithic CMOS IC.

By using the colour management feedback system, the light output produced by an RGB LED array maintains its colour over time and with variations in ambient temperature.

The desired colour can be specified using a standard CIE (Commission Internationale de l'Eclairage or International Commission on Illumination) colour space.

An important advantage of using an RGB LED array and colour management is that the white point in a television can be set to, and will maintain, a wide range of colour temperatures (whether the white tends towards a bluish or yellowish tint).

While professional studio monitors in the US and televisions in Europe are set to a colour temperature of 6500 K, typically US televisions are set for a colour temperature of approximately 7100 K (a bluer tint), and Japanese televisions and most worldwide computer monitors are set to 9300 K (even bluer).

A typical system consists of an array of red, green and blue LEDs, LED drivers, the HDJD-S831-QT333 tri-colour photo sensor that samples the light output, and the HDJD-J822-SCR00 controller. The controller interfaces directly to the photo sensor, processes the colour and brightness information and adjusts the light output from the LEDs until the desired colour is achieved. The HDJD-J822-SCR00 integrates a high-accuracy, analog-to-digital converter front-end, a colour data processing logic core and a high-resolution 12-bit PWM (pulse-width modulation) output generator.

The output pulse width modulation signals are connected directly to the LED drivers, controlling the on-time duration of the red, green and blue LEDs. That duration is continually adjusted in real time to match the light output from the LED array to the specified colour.