Colour management enables LED TV backlighting

A novel colour management system for backlighting LCD flat-panel TVs is claimed to deliver 25% more brilliant colours than current fluorescent backlighting.

Agilent has developed a breakthrough colour management system for backlighting LCD (liquid crystal display) 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 Agilent illumination and colour management system works with high-power Luxeon red, green and blue LEDs (light-emitting diodes) from Lumileds Lighting.

Lumileds is 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.

"Agilent has solved this technology problem".

"Now consumers watching flat-panel TVs will be able to see all colours of the rainbow brighter and more clearly for a more exciting viewing experience".

The innovative Agilent solution solves past problems LCD television display manufacturers have had with RGB LEDs by providing a closed-loop optical feedback system.

The system enables plug and play for OEMs and maintains a set colour point over the life of the TV 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 dynamically 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 (CCFLs).

Although efficient, CCFLs gradually degrade in brightness and change colour with time, and offer a lifetime in the range of 15 to 25kh.

In addition, the CCFL light source only covers 75% of the colour space defined by the National Television System Committee (NTSC), which is responsible for setting television and video standards in the USA.

RGB LEDs with Agilent's illumination and colour management solution exceeds 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 Agilent illumination and colour management solution 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 is not possible with any conventional technology.

The Agilent HDJD-JB01 illumination and colour management system consist of the HDJD-J822-SCR00 colour management controller and the HDJD-S831-QT333 tricolour photosensor.

The colour management controller is a CMOS mixed-signal optical feedback controller IC; the HDJD-S381-QT333 colour sensor is a monolithic CMOS IC solution.

By using Agilent's 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 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 toward a bluish or yellowish tint).

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

A typical system consists of an array of red, green and blue LEDs, LED drivers, Agilent's HDJD-S831-QT333 tricolour photosensor that samples the light output, and the HDJD-J822-SCR00 controller.

The controller interfaces directly to the photosensor, processes the colour and brightness information and adjusts the light output from the LEDs until the desired colour is achieved.

Agilent's HDJD-J822-SCR00 integrates a high-accuracy, analogue-to-digital convertor front-end, a colour data processing logic core and a high-resolution 12bit PWM output generator.

The output PWM 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.

The Agilent HDJD-JB01 illumination colour management system, HDJD-J822-SCR00 colour controller and HDJD-S831-QT333 colour sensor are available individually through Agilent's direct sales channel and worldwide distribution partners.

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