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Low power high image quality display using colour sequential display technology

Final Report Summary - GREEN (Low power high image quality display using colour sequential display technology)

As preplanned in the project proposal and the grant agreement, this Marie Curie Action International Fellowship project is aimed to find a future display solution which is of low power consumption and high image quality. The whole project including two phases:

[PHASE -1]
The first phase was conducted at Philips Eindhoven, from October 2009 to September 2011. During this period, Dr. Zhang proposed and implemented a local-primary-desaturation (LPD) color-sequential display. This LPD color-sequential display technology applies LED backlight and removes the need of color filter, so it has three times higher light efficiency and reduces the power consumption to lower than 25% of the currently used LCDs. With LPD color sequential technology, the spatial resolution is three times higher compared to the currently used LCDs with the same amount of the addressable pixels. It potentially reduces production cost and is well suited for 3-D display applications.

The work includes:
- A local primary desaturation (LPD) algorithm was proposed. It applies a LED matrix backlight and modulates the backlight intensity and chromaticity spatially and temporally according to the image content. A LC panel without color filter is used to refine the light output and provides the high quality image.

- A simulation platform was developed for LPD color sequential display design. Taking backlight and LC panel properties into account, it analyzes input image content, calculates backlight driving signal, simulates backlight profile, and determines LC panel driving signal. It presents the field images and simulates the presence of color breakup, and indicates the power consumption factors.

- A functional demo system was built up. It mainly consists of a 180Hz OCB LC panel and a LED matrix backlight. It proves the concept of LPD color sequential display technology and verifies the simulation model. The demo system was presented to and got interests from different audience both inside Philips and outside Philips.

- Perceptual experiment was conducted to verify the simulation model and evaluate the performance of LPD color-sequential display, especially on the respect of color breakup suppression. The results was used to optimize the LPD algorithm and also analyzed for the color breakup measure modeling.

- Two solutions were proposed to reduce the cost. Both can be accomplished based on a 120Hz LCD (without color filter or with wide band color filter), which is commercial off the shelf and of low production cost.

[PHASE-2]
The second return phase of this Marie Curie Project, from October 2011 to December 2012, was conducted at Philips Research China. During this period, the work includes two parts:

(Part 1) Continuation on the LPD color sequential display technology.

It includes:
- A color breakup measure was built up based on perception experiments and statistic analysis. It provides predicted MOS of color breakup visibility, which has high correlation with the subjective perceptual data. It provides a standard tool for color-sequential display design and evaluation.
- A LPD color sequential based 3D display configuration was proposed. It benefits from high resolution and high light efficiency, both are important for the application of 3D displays. It has potential opportunity of being applied in commercial products, since 3D display technology are not stereotyped yet either in market or in production chain.
- Collaborating with China National Institute of Standardization (CNIS), China Electronics Standardization Institute (CESI), Dr. Zhang submitted a project proposal for Chinese Standardization on Future Display Technology, which passed the first round review.
- Dr. Zhang was invited as a review expert for Chinese Military LCD Standardization Seminar (2012). The DMTF method proposed by Dr. Zhang was accepted by ICDM (International Committee of Display Measurement) as an international standard methodology.

(Part 2) LED's unique features make it possible to realize LPD color sequential display technology. They provide more possibility of cross research and application between lighting and display. To make full use of LED merits and provide lighting more features, taking advantage of working at a lighting research department, Dr. Zhang conducted lighting orientated work, it includes:

(1) A comprehensive outside-in study was conducted on industry lighting, using site visit and user interview to identify the customer need and following research direction. Such built outside-in skill would be of general and lifelong benefit.

- Interviews were planed and arranged with peoples of different positions and different backgrounds both inside and outside Philips. Site visits was arranged with field interview and technical parameters measurement.
- Three workshops intern and cross departments were held for brainstorm and research topic identification.
- Easy maintenance and high (task light) quality were identified as the two main insights. Both these two insights provide LED with more differentiated features than conventional lighting solutions.

(2) Based on the insides above, a matrix lighting solution was proposed. It uses LED matrix and integral lenses, providing adjustable light beam and light spot shapes.

- The matrix lighting technology combines both lighting and display features. Based on integral imaging, it controls the light beams and shapes the lighting patterns. It can be applied in various areas, like in the retail, stage, operation, and so on.
- Preliminary simulation platform was built to trace the light ray. Principle demo setups were built up for the concept verification. Functional demo system is also in process.

The work results in 13 published papers and 7 ID submissions intern Philips. An over 100-page technical report was completed on the work.