Multi-primary Color Research Articles

Baylor University Introduces 6P Multiprimary Color System

On 3 June, at Baylor University’s Research and Innovation Collaborative (BRIC), Baylor University researchers Corey Carbonara and Michael Korpi, both professors in the university’s Film and Digital Media department, opened “Expanding the Color Universe: The Next Frontier in Imaging,” to introduce the 6P multiprimary color system they had been developing over the last two years. The new system, they said, will be a “retro-compatible multiprimary color capture, processing, distribution and display system to advance the ability of digital devices to produce a wider color gamut & closer to natural viewability of the human eye.”

Multi-primary-color quantum-dot down-converting films for display applications.

We propose and fabricate a multi-primary-color (MPC) quantum-dot down-converting film (QDDCF). A four-primary-color QDDCF composed of red (R), yellowish green (YG), bluish green (BG), and blue (B) subpixels was fabricated via totally five rounds of photolithographic processes. A verification platform was built up using a laser projector, and the measured results show that the QD film can expand display color gamut to 118.60% of Rec. 2020 and can cover the entire Pointer's gamut. The issues of blue light absorption and film thickness are analyzed in detail. The combination of MPC technology and QDDCF is a potential strategy to realize ultra wide color gamut for emerging display technologies.

Performance analysis of multi-primary color display based on OLEDs/PLEDs

A multi-primary color display, such as the six-primary color format, is a solution in expanding the color gamut of a full-color flat panel display. The performance of a multi-primary color display based on organic/polymer light-emitting diodes was analyzed in this study using the fitting curves of the characteristics of devices (i.e., current density, voltage, luminance). A white emitter was introduced into a six-primary color format to form a seven-primary color format that contributes to energy saving, and the ratio of power efficiency of a seven-primary color display to that of a six-primary color display would increase from 1.027 to 1.061 by using emitting diodes with different electroluminescent efficiencies. Different color matching schemes of the seven-primary color format display were compared in a uniform color space, and the scheme of the color reproduction did not significantly affect the display performance. Although seven- and six-primary color format displays benefit a full-color display with higher quality, they are less efficient than three-primary (i.e., red (R), green (G), and blue (B), RGB) and four-primary (i.e., RGB+white, RGBW) color format displays. For the seven-primary color formats considered in this study, the advantages of white-primary-added display with efficiently developed light-emitting devices were more evident than the format without a white primary.

多主色LED照明光源的相关色温调控

Based on the established photo-electro-thermal(PET)model,a model predictive control method of Correlated Color Temperature(CCT)for a Light Emission Diode(LED)was investigated to realize the CCT control of multi-primary color LEDs.The Guassian distribution hypothesis and the thermal equilibrium variable relationship stability hypothesis were presented.The regression submodels of different model parameters were calculated by least square estimation method successively according to the strategy of soft model.The change trend of spectral sensitive coefficient curves with different CCT curves was analyzed.Then,current control parameter values of 3typical CCTs at3 000,4 500 and 6 500 K were fixed by the gravity line adjusted method.Finally,a set of spectral power distribution curves were obtained by bringing a certainty random variation to the fixed current control parameter values to validate and evaluate the accuracy of the PET model.Experimental resultsindicate that the PET model predicts accurately the heat sink temperature and the Spectral Power Density(SPD)of the LED by control of the currents and environment temperatures,the accuracy of predictive chromatic coordinate value is better than±0.005,and the accuracy of predictive CCT is better than ±150K.The model-based control method has good accuracy for CCT control and can be generalized to the multi-primary color LED illumination with more primary color channels.

Comparative Evaluation of the Imaging Performance of Multi-Primary Color LCDs With RGBCW and RGBCY Pixel Units by Simulation

Through a simulation study, the imaging performance of two types of multi-primary color liquid crystal displays (LCDs) with striped RGBCW (red, green, blue, cyan, and white) and RGBCY (red, green, blue, cyan, and yellow) pixel units is evaluated comparatively. Results show that color consistency and enhanced luminance can be achieved in image rendering with RGBCW rather than RGBCY pixels when the proposed color conversion algorithm is employed. Color measurement by spectrometry is conducted simultaneously to prove that with RGBCW pixels, the color imaging performance is almost as good as that with conventional RGB pixels; the luminance achieved with RGBCW pixel units is higher than that achieved with RGBCY pixel units.

49.1: Invited Paper: Low Power, High Color Gamut, PenTile RGBCW Hybrid FSC LCD

AbstractHybrid operation of a locally desaturated field sequential color (FSC) multiprimary backlight with a subpixel rendered multiprimary color filtered liquid crystal display offers the potential for lower power consumption and higher color gamut than conventional local dimming RGB filtered LCD TV panels, while further reducing color break‐up compared to locally desaturated FSC LCD w/o color filters.

Review Paper: Multi‐primary‐color displays: The latest technologies and their benefits

Abstract— Multi‐primary‐color (MPC) display technology is one of the fastest emerging research areas in recent years. Wide‐color‐gamut display devices have been required for visually sufficient and/or accurate color reproduction. It is well known that MPC displays can reproduce accurate colors with high efficiency. In addition, not only the image‐quality improvement but some other performance of display devices is also required for display devices. This paper reviews achievements in MPC display technologies and focuses on the benefits of MPC displays: power‐savings and high resolution.

P‐58: Resolution Evaluation of MPC Displays

AbstractIn this paper, we evaluate the resolution characteristics of multi‐primary color (MPC) display systems. We have previously shown that the four primary color (4PC) displays increase effective resolution in the luminance domain to twice that of conventional RGB‐based displays with 4PC‐specialized sub‐pixel rendering we proposed. We improve this rendering method to allow apply five or more primary color systems and compare several rendering methods using the resolution characteristics of each display obtained by computational simulation.

53.1: Invited Paper: Recent Trend of LED Backlight with Local Dimming and its Application for Multi‐Primary‐Color Displays

AbstractWe will consider the characteristics of LED backlights discussing merits and demerits of those characteristics which we will summarize. We have also evaluated combination with multi‐primary color panels. By combining with multi‐primary color panels, it will be possible to create new effects in Local Dimming technology.

Color Calibration Method Based on Spectrally Reproduced Colors and its Application to XYZ-Type Digital Camera

This paper presents the development of a color calibration method based on spectrally reproduced colors produced by multi-primary color narrow-band LED’s. The additive mixture of the primary colors can spectrally reproduce an object color. This approach has been used in our work to overcome the insufficient calibration results obtained by commonly used color targets such as the Macbeth Chart. The method has been tested using a developed prototype of digitally controlled light source calibrated to simulate object color under D65 Daylight standard illumination. The method allows for obtaining of the average color difference for the calibrated XYZ camera of ∆E=0.79 and shows significant improvement in comparison with calibration using standard Macbeth (∆E=1.47). Moreover, we explain the advantages of color calibration with usage of multi-primary light source with regard to the amount of the primary colors.

レーザーディスプレイと広色域映像システム

Wide color gamut displays with using pure-color primaries such as laser displays or multiprimary color

P‐69: Beyond RGB‐Primaries: Chromaticity Measurement Issues for Multi‐Primary Displays

AbstractThe current standards of color gamut measurement regarding RGB‐primary displays are not applicable to multi‐primary color (MPC) display systems. We show two case studies that measurement performed by simply extending the use of today's RGB‐based standards is not able to provide accurate evaluation of the color gamut of MPC displays. The color gamut of MPC displays depends on signal processing algorithm; therefore, for measuring the color gamut of MPC displays, we propose to use not only the input signals of the maximum values for respective colors but also medium‐level signals which are able to measure the chromaticity of respective primary color points on MPC display.

29.2: Power‐Saving: A New Advantage of Multi‐Primary Color Displays Derived by Numerical Analysis

AbstractIn this paper, we present the advantages of Multi‐Primary Color (MPC) display devices compared to the conventional display devices with three (red, green, and blue) primary colors. Not only do we review the well‐known advantages such as wide color gamut and wide viewing angles but also introduce the examples of numerical computation for the purposes of the luminance reproduction. According to the results, we also estimate the potentials of power‐saving for RGB, RGB + Yellow, and RGB + White systems. It is shown that MPC systems are much superior to RGB‐based systems in terms of power‐saving. Not only does RGB + Yellow system widens color gamut but also reduces power consumption by 20% with respect to RGB‐based systems.

19.3: Spatial Analysis of MultiPrimary Color Matrix Arrangements for Mobile Displays

AbstractIn this paper we present the concept of Pixcale displays and analyze their spatial performance. In these displays multiprimary color matrix is placed on top of a standard RGB TFT backplane providing high luminance efficiency with respect to RGB displays of the same subpixel size. However, the placing of more than three primaries on a backplane with subpixel aspect ratio of 1:3 results in an increased period of the full color sequence. In the paper we analyze the implication of the increased color sequence period on data rendering and reproduction accuracy. We show that Pixcale displays reduce power consumption and provide good image quality for mobile applications.

19.4: Color Management Technologies on WideGamut Display Devices with MultiPrimary Colors

AbstractWe propose two color management systems for the cases of 1 RGB input signals to RGBbased display devices and 2 RGB input signals to multiprimary color MPC display devices. for RGB to RGB, our algorithm reproduces “memory colors” as expected and also uses the capability of a display device. for RGB to MPC, we solve a problem causing the hue angle difference between input signals and an MPC display. This realizes faithful hue reproduction as expected in an input image in addition to impressively widegamut of an MPC system.

Gamut boundary description for one dependent primary color

The gamut boundary description (GBD) of multiprimary color displays (MPD) is important for color gamut mapping. Dependent primary color (DPC) is the color stimulus of a controllable color channel represented by an additive mixture of positive amounts of other primary colors. We propose a method to obtain the GBD of a MPD with one DPC. Further, the ideal color volume in CIE xyY and CIE L*a*b* color space with complete-controlling white channel is about 218.8% and 144% compared with the one of digital light processing with incomplete-controlling white channel. The white channel with complete control will not only increase brightness, but also expand color volume.

A color temperature adjustment method for multiprimary displays using nonlinear programming

AbstractMultiprimary display are now widely researched and used. There is little research concerning color temperature design, namely the relationship of the primaries. It is easy to design the relationship in three‐ primary display, because that is a simple 3 × 3 matrix inversion. But it is difficult when the number of primaries gets to be more than three, because the coefficient matrix is not in a square form, which always yields an infinite solution set. This article presents a method to design the relative primary luminances of multiprimary color display. It will be useful in the multiprimary color laser projection or multiprimary color LED‐based backlighting LCD display. © 2009 Wiley Periodicals, Inc. Col Res Appl, 34, 201–204, 2009

A Field Sequential Color LCD Based on Color Fields Arrangement for Color Breakup and Flicker Reduction

The field sequential color (FSC) mechanism can effectively generate multi-primary color fields in temporal sequence to form a full-color image. Color breakup (CBU), however, has appeared intrinsically in conventional FSC displays to degrade visual qualities. A novel CBU suppression method, color fields arrangement (CFA), was proposed to eliminate the artifacts for FSC liquid crystal displays (LCDs). The modified order of consecutive color fields results in superimposed color images on a retina without CBU. Additionally, the 4-CFA method with a field rate of 240 Hz was found to avoid the flicker phenomenon on static images. The proposed method was successfully implemented on a 5.6-in optically compensated bend (OCB) LC panel. Our results confirm that the visibility of CBU artifacts can be reduced as the evaluation of dynamic and static models.

Beyond Red–Green–Blue (RGB): Spectrum-Based Color Imaging Technology

This article presents a comprehensive study on the spectrum-based color reproduction system, called Natural Vision (NV), which aims to break through the limitation of red–green–blue (RGB) three-primary schemes. After a basic discussion on the motivation for color imaging technology beyond RGB, the method for systematizing the multispectral and multiprimary color imaging technologies, including image capture, processing, storage, printing, and display, is presented. Then experimental multispectral systems for both still image and video are introduced, and the following features of spectrum-based scheme are revealed: a) highly accurate color reproduction is possible even under different illumination environment, b) an expanded color gamut can be reproduced by multiprimary color displays, c) the influence of observer metamerism can be reduced by the spectral color reproduction, and d) the quantitative spectral attributes of an object, useful for its analysis or recognition, can be captured and preserved. Finally, the effectiveness of the system is also demonstrated through experiments in fields of application, such as medicine, digital archives, color printing, electronic commerce, and computer graphics.

Design Considerations Between Color Gamut and Brightness for Multi-Primary Color Displays

Color displays show a vivid colorful image by combination of three or above primary colors on every individual pixel. Brightness of color displays, however, strongly restricts the color gamut of displays. From the color mixing theory, the area of color gamut on the color coordination would shrink smaller when brightness grows up. At the maximal brightness, displays can show one system white point only. The difficulties how to obtain the maximal brightness under an assigned color point or color gamut have been a key issue for display manufacturers. The paper proposes a theory to analyze the relation between brightness and color gamut based on the multi-primary color display. Simulations estimate the boundary of color gamut of multi-primary color displays under required brightness which had been proved by experimental results of tri-primary color display. The theory can be applied on the color temperature (CT) design which experimental results show the fact that a display apparatus with higher color temperature could sacrifice brightness less compared to one with lower color temperature when color temperature of the display image needs to change. The theory provides a design guideline for optimization between color gamut, color temperature and brightness on multi-primary color displays