Backlight Panel Research Articles

Deep Controllable Backlight Dimming for HDR Displays

High dynamic range (HDR) displays with dual-panels are one type of displays that can provide HDR content. These are composed of a white backlight panel and a colour LCD panel. Local dimming algorithms are used to control the backlight panel in order to reproduce content with high dynamic range and contrast at a high fidelity. However, existing local dimming algorithms usually process low dynamic range (LDR) images, which are not suitable for processing HDR images. In addition, these methods use hand-crafted features to estimate the backlight values, which may not be suitable for many kind of images. In this work, a novel deep learning based local dimming method is proposed for rendering HDR images on dual-panel HDR displays. The method uses a Convolutional Neural Network (CNN) to directly predict backlight values, using as input the HDR image that is to be displayed. The model is designed and trained via a controllable power parameter that allows a user to trade off between power and quality. The proposed method is evaluated against seven other methods on a test set of 105 HDR images, using a variety of quantitative quality metrics. Results demonstrate improved display quality and better power consumption when using the proposed method compared to the best alternatives.

Using a bio-inspired copper complex to investigate reactive mass transfer around an oxygen bubble rising freely in a thin-gap cell

The present study describes an original colorimetric method to visualize and quantify the local oxygen mass transfer around a rising bubble in reactive media. This method is based on the use of a colorless bio-inspired copper complex, Cu(btmgp)I, specially tailored for the study, which, dissolved in acetonitrile, oxidizes into an orange copper-complex [Cu2O2(btmgp)2]I2. The latter complex, unstable at ambient temperature, decays quite fast into two Cu(II) complexes, leaving a permanent pale-green color as final products. The flow investigated consists in a pure oxygen single bubble rising freely in a confined thin-gap cell (400 × 200 × 1 mm). A wide range of motion regimes for the bubbles are observed as the Archimedes number ranges from 860<Ar<18,800 and the Reynolds number from 580<Re<8200. A high-resolution 16-bit sCMOS camera, combined with specific filters, is used to capture images from a region-of-interest of the cell, illuminated by a white LED backlight panel. An ad hoc calibration protocol is developed to correlate the grey-levels from the colored signal to the equivalent oxygen concentrations. This procedure then allows to measure indirectly the amount of oxygen transferred to the liquid phase. The series of images are also treated to identify the bubble motion and properties. Thanks to this method, equivalent oxygen concentration fields, gap-averaged and time-averaged, can be reached with high precision in the far-field wake of the bubbles, enabling thus to deeply characterize the mass transfer mechanisms under reactive conditions in such confined configuration, and to establish a dimensionless representation in terms of Sherwood number versus Peclet number. At last, thanks to the knowledge of the kinetic rate of the reaction and of the diffusion coefficients, the Hatta number and the enhancement factor are estimated, and thus the intrinsic Sherwood numbers; these results demonstrate that the enhancement of the mass transfer by the reactions involved with the copper-complexes is not negligible (almost 12–15%).

Achieving 12-bit perceptual quantizer curve with liquid crystal display.

We proposed a scheme to drive the light emitting diode (LED) backlight and liquid crystal (LC) panel simultaneously to achieve 10,000-nit 12-bit perceptual quantizer (PQ) curve, which is required by high dynamic range (HDR) displays. Besides the relative fast response time and low driving voltage, this approach can also mitigate image noises.

A Saliency-Driven LCD Power Management System

Large liquid crystal display (LCD) technology is being widely used in every corner of our modern life, ranging from personal laptops to flat-panel televisions. Among all the components in an LCD display system, the backlight panel is the dominant power consumer, irrespective of lighting technology or class. In this paper, a saliency-based field-programmable gate array accelerator for revolutionary LCD power management is proposed that allows dynamic modulation of the different zones of the backlight panel. This hardware accelerator-based system is capable of processing a high-definition video stream in real-time and uses less than 50% of the power that a normal LCD display system consumes, with minimum overhead. We also compare our proposed approach with other state-of-the-art power-aware methods and show numerous advantages using our data-driven strategy.

Development of a continuous injection direct rolling imprint system for microstructure thin-plate

A prototype of a continuous injection direct rolling (CIDR) imprint system was developed and applied to CIDR tests to evaluate its feasibility for the large-area replication of an optical micro device. The developed system adopts the theories of injection compression and thermal imprinting and presents the capacity to fabricate a 200 mm-wide and over 10 m-long PMMA plate and to replicate ultra-precision structures on its surface at a rolling speed range of 1.1–11.5 mm/s. Under the given CIDR conditions (injection temperature, 280 °C; injection pressure, 6 MPa; rolling force, 13 MPa; roller temperature, 85 °C), complete fabricating of a 0.7 mm-thick Polymethyl methacrylate (PMMA) plate with 17.3 μm-deep and 35 μm-wide V-groove microstructures was achieved at a rolling speed of 3.4 mm/s. Finally, a light guide plate for a backlight panel was fabricated by CIDR. The light transmittance of this plate reached 90.8 %, the maximum birefringence was ~99 nm and its average haze was 0.51 %.

59-2:Distinguished Paper: The Role of Local Dimming Density, Native Panel Contrast, and Glare Sources in the Visual Quality of HDR Displays

Using an RGB OLED display, we applied a paired comparison method to evaluate visual preference of OLED images and LCD emulations with varied backlight zone spacing and panel contrast. We also evaluated the impact of a glare source. Panel contrast was the strongest factor in determining image quality.

Q-point estimation for an LED arrangement in a large-scale lighting display using the mean value approach

A generalized light-emitting diode (LED) arrangement using the mean point (also known as the Q-point) approach from the well-known mean value theorem is proposed to simplify the estimation of LED combinations in large-scale lighting displays. A power dissipation (PD) curve built by N LEDs in series is explored to guide the estimation in a definite route, in which the estimation for the LED arrangement and power requirement can be quickly acquired, even in multiple estimations. With the Q-point, the estimation process can be easily achieved by simply taking the square root of a total of N LEDs. This is much faster than the usual step-by-step bisection estimation. Accordingly, further estimation can continue along the PD curve until the resultant combination is suitable for practical use. A non-integer adjustment reconciling to reach the feasible application is only tailored to the decimal part of the estimation number after integer estimation. The luminance distribution in the direct backlight panel is measured using a nine-hole window frame, which shows an average luminance between each pair of holes of about 1.15 kcd/m2. This is quite similar to a surface light source before using a light filter.

Optimal Backlight Modulation With Crosstalk Control in Stereoscopic Display

Crosstalk between the left-eye and right-eye images is one of the main artifacts affecting the visual quality of stereoscopic liquid crystal display (LCD) systems. In this paper, a novel technique, called Optimal Backlight Modulation (OBM), is proposed to reduce crosstalk by taking the advantage of newly emerged light-emitting diode (LED) backlight panel. Unlike most existing techniques which solely aim at eliminating the effect of crosstalk, ignoring image brightness and contrast, OBM strikes a better balance by maximizing the output luminance while confining the crosstalk within a given level. A simple closed-form approximation of the optimization problem can be easily employed and solved in real time on LCD control hardware. Simulation results show that the proposed OBM algorithm provides the same or higher luminance while reducing the crosstalk by 60% compared with the other tested methods.

Orientation effect on heat transfer of a shrouded LED backlight panel with a plate-fin array

This study reports thermal performance of a shrouded 348mm×558mm aluminum plate-fin heat sink subject to various input powers and orientations. Effects of clearance (C) and the orientation on the heat transfer of the heat sink were investigated. Results show that the clearance effect is detectable only in a “window region” between 5mm and 10mm where an appreciable rise of heat transfer coefficient is encountered. As the tilted angle (θ) of the LED panel is increased, the heat transfer coefficient is reduced and the clearance effect on heat transfer becomes more pronounced. The heat transfer coefficients are similar between two cases in which the tilted angles of the LED panel are supplementary irrespective of clearance and input power. Except the cases of a horizontal heat sink, heat transfer coefficient of the shrouded heat sink having a fin array facing downward is usually slightly higher than that having supplementary tilted angle.

Display power analysis and design guidelines to reduce power consumption

Cold cathode fluorescent lamps (CCFLs) are used to provide lighting for liquid crystal displays (LCDs). This paper presents a set of guidelines for measurement characterization and design to reduce the power consumption of CCFL LCD backlight inverters and panel electronics. The proposed methods aim to reduce the backlight power consumption by fine-tuning a backlight inverter for a specific LCD, using several methods. First, the authors describe their power measurement methodology; and next, they identify different areas for tuning a backlight inverter for a given display. The experiment results showed that power savings can range from 50 to 200 mW if the backlight inverter is properly tuned. This paper also proposes an optimized configuration for light-emitting device (LED) panels to reduce power loss by selecting a LED with a specific input voltage and number of cells to help minimize power loss.

6.3: A New Method for Hot‐Spot and Mura Quantification and Evaluation in LCD Backlight Units and Panel

AbstractA convenient method to quantificationally and objectively describe the grade of hot‐spot and mura of Liquid Crystal Display is introduced. By converting the spatial backlight unit luminance distribution of a Liquid Crystal Display to frequency domain, Fast Fourier transform is used for luminance variation analysis. The results not only give a factor which can quantificationally describe the grade of hot‐spot and mura of a LCD backlight unit area but also unify different experimental processes that using a camera or a Radiant Imaging ProMetric 1400 system keeping the results consistent.

Two‐parallax‐barriers‐based autostereoscopic liquid‐crystal display without cross‐talk

Abstract— An autostereoscopic liquid‐crystal display (LCD) consists of two parallax barriers and an LCD including a liquid‐crystal panel, and a backlight panel is proposed. Parallax barrier 1 is located between the backlight panel and the liquid‐crystal panel, and Parallax barrier 2 is located between the liquid‐crystal panel and viewers. The operation principle of the autostereoscopic display and the calculation equations for the parallax barriers are described in detail. The autostereoscopic LCD was developed and produces high‐quality stereoscopic images without cross‐talk at the optimal viewing distance and less cross‐talk than a conventional one based on one parallax barrier at other viewing distances.

Autostereoscopic three-dimensional display based on two parallax barriers

An autostereoscopic three-dimensional (3D) display composed of a flat-panel display, two parallax barriers, and a backlight panel is proposed. Parallax barrier 1, located between the backlight panel and the flat-panel display, divides the lights to create the perception of stereoscopic images. Parallax barrier 2, located between the flat-panel display and the viewers, acts as the function of decreasing the cross talk of the stereoscopic images. The operation principle of the display and the calculation equations for the parallax barriers are described in detail. An autostereoscopic 3D display prototype is developed. The prototype presents high-quality stereoscopic images. At the optimal viewing distance, it presents stereoscopic images without cross talk. At other viewing distances, it has less cross talk than a conventional autostereoscopic 3D display based on one parallax.

Thermal characterization of shrouded plate fin array on an LED backlight panel

This study experimentally investigates a 348 mm × 558 mm LED backlight panel consisting of 270 1-W LEDs and a plate-fin heat sink in an acrylic housing. Effects of shroud clearance, obstructions at entrance or exit on the overall performance are also examined. The results show that the heat transfer coefficient is very slightly reduced with the rise of shroud clearance from 0 mm to 5 mm, followed by a notable rise but it peaks at a shroud clearance between 10 and 20 mm. A further increase of shroud clearance leads a marginal decrease of heat transfer coefficient. It is found that the maximum temperatures within the LED panel are not necessarily located at the center region due to the edge effect. On the other hand, the temperature variation along the longitudinal direction indicates a local minimum Nusselt number occurring near the exit of LED panel. This unique phenomenon is associated with the development of velocity and temperature field, and is consistent with previous numerical examinations. On the other hand, the obstruction placed at the exit are often severe than at the entrance.

P‐167: High‐Efficiency Solution‐Processed 3.5‐inch White Backlight Panel Based on a Blue Dendrimer

AbstractHigh‐efficiency and color stable 3.5‐inch white backlight panel with maximum efficiency of 9.5 cd A−1 and CIE coordinates of (0.30, 0.31) is obtained utilizing a solution‐processible fluorescent π‐conjugated dendrimer, G0, as host, and MEH‐PPV and P‐PPV as guests.

Color Breakup Reduction by 180 Hz Stencil-FSC Method in Large-Sized Color Filter-Less LCDs

Field-sequential color (FSC) is a high optical throughput technique for future green liquid crystal displays (LCDs). However, the FSC-LCD faces a lethal issue, color breakup (CBU) which degrades image clarity and prevents high level LCD-TV productions. We proposed the 180 Hz Stencil Field-Sequential-Color method to redistribute intensities of the three primary color field-images to suppress CBU. By applying local color-backlight-dimming technology to FSC-LCDs, a low resolution colorful backlight panel combined with a high resolution color filter-less LC panel generated a green-based multi-color field-image which showed the most image luminance in the first field. Therefore, residual red and blue field-image intensities were reduced and effectively suppressed CBU when compared to field-rate increasing methods. In addition, to further implement hardware, the number of backlight divisions of 32×24 and a proper Gaussian point spread function profile were optimized via simulations while considering CBU reduction and image fidelity. Using optimized hardware parameters, the CBU phenomenon was suppressed by 50% of traditional RGB driving in simulation and was demonstrated on a 120 Hz 46-inch MVA LCD-TV.

Controllable Viewing-Angle Display Using GHLC Cell as Backlight Panel

There is a desire for a display technology which can change the display viewing angle. Controllable Viewing Angle (CVA) device has been developed by using a Guest-Host liquid crystal cell which allows a high light-shielding effect and the control with a wide range of available viewing angle. By putting the CVA device on a Thin-Film Transistor ( TFT ) Liquid-Crystal Panel, or placing a Guest-Host Liquid Crystal (GHLC) device between the LED and the backlight, we have realized a simple controllable viewing-angle LCD which could be switched in the narrow and normal(wide) viewing angle. The viewing angle can decrease to 40° when power is on but it also can shift to normal viewing angle when power is off.

5.2: Approaches to Virtual Product Development in LCD Business

AbstractIn the process to build up the complicated system for a LCD backlight unit, a panel and their module assembly, the use of physical prototype has many drawbacks in terms of cost and lead‐time. The virtual prototyping platform, EzOptics we developed in the cooperative work, provides the way of working where the LCD design and optical analysis activities can be developed in the early product development stages. The work being described here permits that a designer analyses the optical characteristics of a LCD module with a panel. In the LCD industry this must be the first system by which the virtual prototyping of LCD can substitute the physical prototype. The system allows a virtual prototype with a full size scale LCD backlight unit and panel modelling without any limitations of the size and shape. The result of the simulation also guarantees the accuracy by supporting the bidirectional scattering distribution functions (BSDF) to define the scattered light propagation over the optical components, and the expert knowledge is provided for more comprehensive, quick and user‐friendly virtual prototype modelling.

Luminance and brightness field distribution of light guiding plate for backlight panel (BLP) by micro molding

AbstractThis research investigates the luminance and the brightness field distribution of the microstructure of a light guiding plate (LGP) by micro injection molding (MIM) and micro injection‐compression molding (MICM). The process of manufacturing a LGP includes photo‐etching, MIM, MICM, and optical field measurement. The results show that the luminance of microstructure of LGPs produced using MICM is better than those made using MIM. The results also indicate that the most important processing parameter is the mold temperature for the luminance distribution of the LGP whether made by MIM or MICM. The maximum luminance of the LGP is 80 Nit (cd/m2) on micro molding. The brightness field distribution of the LGP made using MICM is more uniform than those made using MIM for the same processing parameters. MICM is a more suitable process than MIM for the fabrication of a LGP on a backlight panel (BLP). Copyright © 2008 John Wiley &amp; Sons, Ltd.

LED를 PLS 배열로 사용한 시역 형성 광학계가 없는 3차원 영상의 시역에 대한 연구

A two dimensional point light source array can replace both the viewing zone forming optics and the back light panel in the contact-type 3 dimensional imaging systems based on LC panels. This replacement can make the system structure of the 3 dimensional imaging systems no different from that of the conventional LCD and can reduce undesirable visual effects caused by the viewing zone forming optics. The problem with the point light source array is the visual quality deterioration of the system due to the non-ideal nature of the array.