Adaptive local backlight dimming algorithm based on local histogram and image characteristics

Real-time gamma correction is an essential function in display devices such as CRTs, plasma TVs, and TFT LCDs [1]. In this paper, we present the image quality enhancement by real-time gamma correction for a CMOS image sensor in mobile phones. The proposed algorithm and system operate with a block structure and the bit width of input and output of the proposed system is 12-bit. The proposed gamma system is reduced the error range and enhanced the image quality compared with conventional system that has 10-bit input and 8-bit output. The proposed system was implemented experimentally by using Xilinx Virtex4 FPGA and was successfully demonstrated with a CMOS image sensor for mobile application.

Thermal effects were investigated in a liquid crystal display (LCD) backlight unit (BLU) that was composed of light emitting diode (LED) arrays. The driving power for a single LED in a BLU is determined by the desired brightness of the LCD panel and the pitch distance between adjacent LEDs. As the pitch distance increases, individual LEDs need to be driven by a higher power in order to maintain the same brightness. Since the junction temperature of an LED plays an important role in LED performance, such as optical efficiency, intensity degradation, and lifetime, the maximum driving power for an LED should be limited by a critical level of the junction temperature. A guideline for designing LED BLU panels taking account of the junction temperature is presented using various parameters of LED arrays.

With increase in image quality and screen sizes, the energy consumption of computer displays and television sets has significantly grown. In a typical personal computer or PC, display accounts for 30%~50% of the total PC energy consumption [Mahesri 2005, Robertson 2002]. For instance, typical 19 inch LCD monitor, such as Sony SDM-S93 (1280x1024 pixels), burns in active mode 50W or almost 38% of the total desktop system power (130W). With large popularity of video and gaming applications, LCD makers are being called on to cut power consumption while providing better images. Rapid utilization of multiple displays -each consuming tens of watts -throughout homes, offices and buildings increases cost and environmental impact of energy consumption significantly. Although most PC displays support power management, new robust methods are needed for evolving display usage scenarios. For TV sets, the quest for efficient display energy management is more severe, because modern TVs have much bigger screens than computer displays and therefore consume more power. Although the LCD TVs are more efficient than their cathode-ray tubes (or CRT) TVs, recently emerged plasma television sets are twice as bigger and about four times more energy than their cathode-ray tube equivalents [Coughlan, 2006]. A 50-inch flat-screen plasma HDTV now burns over 500Watts of power [Plasma TV, 2006]; consuming almost the same amount of energy as dishwasher or in-room air-conditioner. The problem however does not relate only to plasma television sets. The LCD TV sets also consume a lot. A typical 42” LCD TV takes 169-250Watts of power per each hour [TV Power Consumption, 2008]. According to Nielsen Media Research Inc. [Nielsen 2009] over 99% of all households in US have TV sets, with 2.24 TVs per household in average. Since TV is ON for almost 5 hours in an average US home a day [Television & Health], it has become one of the largest energy consumers. Due to emerging problems of global warming and fossil fuel shortage, reducing TV energy is very important. Up to the date, reducing energy consumption of LCD displays has been tackled mainly through system and circuit optimizations, which either ignore the user, assuming fixed and stable demands on system operation or rely on very simplified policies, which eventually lead to large energy losses. Generally, there are two sources of energy losses in a device: intrinsic losses and the user-related losses. The intrinsic energy losses are caused by the engineering design, technology and materials used in construction of the device. For example, a plasma TV intrinsically dissipates more energy than a LCD TV, etc. The user-

ObjectivesTo evaluate the radiation exposure, quantitative, and qualitative image quality in pediatric cardiac CT by using photon-counting detector computed tomography (PCD CT) versus energy-integrating detector CT (EID CT) in matched children.Materials and methodsThirty-seven contrast-enhanced, clinically indicated cardiac CTs performed on PCD CT were matched with 37 examinations acquired by EID CT. The patients were matched according to water-equivalent diameters. Quantitative evaluation of image quality comprised a region of interest (ROI)-based analysis, calculating image noise, signal-to-noise (SNR) and contrast-to-noise (CNR) ratio. Differences of the attenuation variation of the paraspinal and the pectoral muscles were calculated to measure beam hardening artifacts. Volume CT dose index (CTDIvol) and dose length product (DLP) were documented, and the effective radiation dose was calculated for each patient. Statistical analysis comprised t-tests and Wilcoxon signed rank tests.ResultsThe mean age of the children on PCD CT was 794 ± 1016 days, similar to the mean age of 815 ± 957 days of the children on EID CT (p = 0.76). Moreover, age, height, weight, and body mass index (BMI) were also not significantly different between the two groups (p ≥ 0.32). Radiation exposure was significantly lower on PCD CT (CTDIvol 0.20 ± 0.12 mGy and DLP 4.06 ± 3.22 mGy*cm) versus EID CT (CTDIvol 0.37 ± 0.17 mGy, p < 0.001 and DLP 7.21 ± 4.67 mGy*cm, p < 0.001). No significant differences in SNR, CNR, or beam hardening artifacts could be observed. Qualitative image quality was also comparable for PCD CT versus EID CT.ConclusionsWith a reduction in radiation exposure exceeding 40% by using PCD CT, image quality remained stable compared to EID CT. Reducing radiation with PCD CT while preserving image quality might substantially advance cardiac imaging in children.Key PointsQuestionChildren are particularly sensitive to radiation exposure, highlighting the need for dose reduction.FindingsRadiation dosage can be significantly reduced while preserving image quality when using photon-counting detector (PCD) CT in pediatric patients with congenital heart disease.Clinical relevanceSince radiation exposure can be significantly reduced by PCD CT compared to energy-integrating detector (EID) CT, while image quality was comparable, PCD CT is advisable for children with congenital heart disease.Graphical

This paper presents a color sequential light‐emitting diode (LED) backlight power system for large‐scale LCD panels. The proposed power system uses ripple‐free circuit to improve image quality. In the proposed circuit structure, a set of power converter is operated in interleaving fashion and with switching regulation for generating two sets of output voltages to respectively supply red, green and blue LEDs by switch control. with this approach, an inductor for achieving ripple—free feature is adopted in each phase of the proposed interleaving converter. Compared to the conventional color—sequential LED backlight power system, the proposed power converter can be reduced its power converter counts, size, volume and cost, and increased its conversion efficiency significantly. Simulated results obtained from the proposed power system have been verified its feasibility.

This paper proposes high performance control of light emitting diode(LED) drive system for liquid crystal display(LCD) backlight. The CCFL(cold cathode fluorescent lamp)was used to a conventional LCD backlight. Due to improvement on luminous efficiency, long life and wide color gamut, LED has gradually substituted for CCFL as backlight. The backlight using LED is necessary to use many LED. For that reason, the LED backlight is using a lot of LED driving circuits. The many LED driving circuit is generated a current deviation between LED. Eventually, it is caused brightness deviation between LED. Therefore, this paper improves the current deviation using transformer and balancing capacitor to solve this problem. Also, for accurate and uniform brightnesss control, this paper is applied the artificial intelligent control to a dimming control. This paper is compared with conventional system, and validity of this paper proves through that result.

In this paper, we propose a new method for reversible data hiding by employing the hierarchical relationships of original images. Considering the ease of implementation and the little overhead needed for decoding, we employ the histogram-based scheme with extensions for reversible data hiding. By utilizing the hierarchical structure and corresponding histograms of difference values, global and local characteristics of original images can be utilized for hiding more capacity with acceptable quality of output image. With our method, better performances can be obtained in enhanced image quality, embedding capacity, and comparable amount of side information. More importantly, the reversibility of our method is guaranteed, meaning that original image and hidden message can both be perfectly recovered at the decoder. Simulation results demonstrate that proposed method in this paper outperforms those in conventional histogram-based algorithms.KeywordsReversible data hidinghierarchical structurequadimage qualitycapacity

This paper presents analysis of lighting quality in different road surface conditions using the DIALux software. Dry and wet road surfaces are used to study lighting quality by following classifications of the International Commission on Illumination (CIE). Lighting quality of high pressure sodium (HPS) and light emitting diode (LED) luminaires are compared, based on roadway with a traffic island. Results indicate that the HPS luminaire can provide better average illuminance and average luminance values than the LED luminaire, resulting in positive visual performance. However, the LED luminaire can achieve visual and comfort performance including energy saving due to its light distribution efficiency. For lighting quality on different road surface conditions, the lighter dry road surface materials, the higher lighting quality. Wet road surfaces cause very bright areas on road surface alternating with large dark areas. It results in the average luminance of the surface increased while overall uniformity decreased.

A low power consumption is an essential issue for all of the electrical products, especially for the wearable electrical products, and the liquid crystal displays. This manuscript proposed a single polarized light emitting diode (LED) chip which is used for a direct back light unit for LCD. A wire grid polarizer and a meta‐ surface textures are set on the top and bottom of the LED chip in order to obtain a high polarization and transparency. After optimization the potential parameters, the transmittance of TM and the polarization are 93.71% and 99.3% respectively. It can replace the normal LED of direct back light unit in order to obtain a high efficiency of 20% improvement, by comparing liquid crystal display using the APF polarizer. It can be used for reducing power consumption and supply dependence, as well as the cost of displays.

A low power consumption is an essential issue for all of the electrical products, especially for the wearable electrical products, and the liquid crystal displays. This manuscript proposed a single polarized light emitting diode (LED) chip which is used for a direct back light unit for LCD. A wire grid polarizer and a meta‐surface textures are set on the top and bottom of the LED chip in order to obtain a high polarization and transparency. After optimization the potential parameters, the transmittance of TM and the polarization are 93.71% and 99.3% respectively. It can replace the normal LED of direct back light unit in order to obtain a high efficiency of 20% improvement, by comparing liquid crystal display using the APF polarizer. It can be used for reducing power consumption and supply dependence, as well as the cost of displays.

A method to maximize backlight dimming of liquid crystal displays (LCDs) based on human visual system are proposed to minimize power consumption of display panels. Based on images, the proposed method optimizes global, local, and red, green, blue (RGB) backlight dimming by enhancing dimming about 12% on average for various images while maintaining tolerable degradation of perceived image qualities in pixel saturation areas. The method considers and utilizes the brightness sensitivity and contrast response functions of human visual system using the mean luminance and the contrast of an image, which are mathematically modelled to allow optimization for display panels and application areas. A simulator that can calculate various dimming cases with the evaluations of numerical and perceptual image qualities as well as power consumption amount is introduced. With pattern and real photo images, the degree of power savings and the preservation of image quality of the proposed method are verified to outperform conventional approaches with high scores of the mean opinion score (MOS) and the structural similarity index measure (SSIM) over 0.97 while saving more than 10% of power dissipation.

Chapter 11 - Video Technology: TV and Video Is All Digital Now

The color characteristics of medical liquid-crystal displays (LCDs) have become one of the main interests in quality assurance and quality control of medical display devices. It is necessary to evaluate variations of the color characteristics in medical LCDs in order to provide consistent color characteristics for image reading. In this study, we characterize the color characteristics in grayscale images displayed on medical LCDs. Eight medical color LCDs and eight medical monochrome LCDs were used in this study with operating times ranging from 800 to 25 000 h. Default settings of correlated color temperature (CCT) of white points for all color LCDs were set at 7500 K. We measured chromaticity in the Commission Internationale de l'Éclairage (CIE) u'v' color space and CCT of the white point at 18 luminance levels. A colorimeter and grayscale test patterns with various luminance levels were used for the measurements. First, we examined differences in chromaticity and CCT at 18 luminance levels for each LCD. Second, we compared chromaticities of the different LCDs. Then, chromaticity and CCT of LCDs were measured at different ambient light conditions (30 and 560 lux) and compared to those measured in a dark room. Finally, the relationship between operating times and CCT was evaluated. The chromaticities of monochrome LCDs changed toward the blue and CCT increased as luminance decreased. In color LCDs, the chromaticity and CCT of the white point except at the minimum luminance were nearly constant to those measured at the maximum luminance. We observed differences in chromaticity between color and monochrome LCDs because of the nonadjustable white point of monochrome LCDs. When the ambient light increased, chromaticity varied, and CCT decreased on every LCD. Ambient light had a much greater impact on chromaticity and CCT at lower luminance levels. The CCT of LCDs decreased in longer operating times. The grayscale of LCDs with longer operating times was measured to be more yellowish due to the degradation of cold cathode fluorescent lamps. Our results clearly indicate that the white point in grayscale images displayed on medical LCDs changes depending on luminance levels, color or monochrome LCDs, ambient light conditions, and operating times. These data provide useful information to understand color characteristics of LCD for image reading, especially for quality assurance and quality control of LCDs.

Estimating the economic life of a technology is the first important prerequisite step in the feasibility analysis of technology-based business. Many empirical studies have concentrated on patents data to estimate the time period for a technology. However, it is recommended to estimate it along with qualitative considerations of future technological and market conditions. In this regard, little is known about how approaches are applied. This paper aims to establish a structural framework of estimating the lifetime of a technology by integrating the outputs of an analysis of the determinants in each transition of a product life cycle. We describe an illustrative case about a light emitting diode (LED) backlight unit (BLU) technology for the liquid crystal display (LCD) TV. The framework allows valuators and experts to estimate a technology lifetime by using multidimensional factors.

Optimisation of lighting quality and energy efficiency of LED luminaires in roadway lighting systems on different road surfaces