• Journal of the Institute of Electronics Engineers of Korea SP
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• v.48 no.4
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• pp.38-48
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• 2011

Block based LCD backlight nonideality and crosstalk compensation methodologies are proposed based on the analysis of backlight profiles and image pixel homogeneity. Large computation complexity required in the conventional compensations is minimized without the degradation of image qualities by optimizing image block size, image area inside the block to be excluded from the compensation computation and the required backlight range to be computed. The optimization results of computation complexity as well as image qualities are verified for the proposed compensation by real image data simulations.

• Journal of Korea Multimedia Society
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• v.22 no.8
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• pp.860-873
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• 2019

LCD backlight boosting and the integration of boosting and dimming are proposed based on image analysis to maximize perceptual image qualities and to reduce display system power. Based on the histogram of the image data, methods for selecting an image suitable for boosting and for adjusting the optimum backlight brightness are proposed. A comprehensive combined optimization method of LCD backlight boosting, dimming and bypass based on image characteristics is also described. Perceptual image quality enhancement and power consumption are evaluated based on well known image databases. Average subjective image quality is improved by 24.8%, RMS contrast is improved more than 20%, and average power consumption is reduced by 15.94% compared to conventional uniform boosting.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.972-974
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• 2009

This paper presents smart regional contrast enhancement technique of partitioned image for local dimming backlight on small-sized mobile display to reach two goals. One is to save the power consumption, and the other to improve contrast ratio of display image. Recently new advanced method is proposed, named local dimming method, that backlight LED is positioned on backside of the display panel. So it is important to partition an image by sub blocks and then post-processing independantly. This means regional contrast enhancement. After partitioning, we compare the mean luminance(Y) value of each sub-block image with the one of original whole image. If some blocks have the mean value lower than the one of whole image, they are processed with the proposed method and others are bypassed. Simultaneously the information of the processed blocks are transferred to BLC(Backlight LED Controller). And then the supply current of each backlight LED is reduced to realize the contrast ratio enhancement and at the same time to power consumption reduction. In addition, we verify this proposed method is free from blocking artifacts.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.791-794
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• 2004

In this article, we present a method to measure precisely the performances of direct-lit CCFL backlights using a luminance meter and dedicated image analysis software. The array of CCFL tubes alone can be measured directly and the luminance of each tube can be extracted along its main dimension. So, comparison of the different tubes on the same backlight can be made easily and the performances in terms of backlight uniformity improved. The influence of the diffuser sheet can be probed in the same way and the homogeneity of the entire surface of the backlight can be automatically extracted and quantified.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.709-712
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• 2017

Liquid nitrogen jet has been imaged by using backlight method. In addition to the images, simultaneously measured temperature by thermocouples has been used to investigate the role of 'Pseudo-flash-boiling' in breakup of the supercritical jet. The backlight image can provide qualitative appearance of the jet, but not the density profile for the high density of injected fluid.

• Journal of Information Display
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• v.11 no.4
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• pp.173-181
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• 2010

In this paper, light-emitting-diode (LED) backlight driving circuits and dimming method for medium-sized and large liquid crystal displays (LCDs) are proposed. The double loop control method, the intelligent-phase-shifted PWM dimming method, the fast-switching current regulator, and the current matching techniques are proposed to improve not only the current regulation characteristics and the power efficiency but also the current matching characteristics and the transient response of the LED current. The brightness of the backlight using the proposed local dimming method was determined from the histogram of the local block to reduce the power consumption of the backlight without image distortion. The measured maximum power efficiency of the LED backlight driving circuit for medium-sized LCDs was 90%, and the simulation results showed an 88% maximum power efficiency of the LED backlight driving circuit for large LCDs. The maximum backlight power-saving ratio of the proposed dimming method was 41.7% in the simulation with a high-contrast image. The experiment and simulation results showed that the performance of LEDs as LCD backlight units (BLUs) improved with the proposed circuits and method.

• Journal of the Semiconductor & Display Technology
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• v.7 no.2
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• pp.29-33
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• 2008

LCD panels are increasingly used to show moving image material, for example in LCD television sets. However, moving images become blurred on LCD panels. One of the causes of motion blur is the slow reaction of LC(liquid crystal) cell to change in the pixel value. Another cause of motion blur is the hold-type characteristic of the LCD panel, during the frame time the image is shown continuously. This type of motion blur can be reduced with a scanning backlight. We have designed and fabricated a scanning backlight system that solves the hold-type characteristic problem in a way that Flat fluorescent lamp divided 6 blocks was scanned 60Hz.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.1316-1318
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• 2009

Nonideality of LED lens and diffuser as well as crosstalk between backlights should be compensated because they have large effects on image qualities. The computation complexities of conventional compensations are greatly increased as resolution becomes higher. The block based compensation is proposed to alleviate the computation complexity considering backlight profiles and image pixel characteristics.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.62 no.2
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• pp.90-94
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• 2013

In this paper, we propose a new algorithm to improve the contrast ratio, to preserve information of bright regions and to maintain the color of backlight image that appears with a great relative contrast. Backlight images of the natural environment have characteristics for difference of local brightness; the overall image contrast improvement is not easy. To improve the contrast of the backlight images, MSR (Multi-Scale Retinex) algorithm using the existing multi-scale Gaussian filter is applied. However, existing multi-scale Gaussian filter involves color distortion and information loss of bright regions due to excessive contrast enhancement and noise because of the brightness improvement of dark regions. Moreover, it also increases computational complexity due to the use of multi-scale Gaussian filter. In order to solve these problems, a linear MSR is performed that reduces the amount of computation from the HSV color space preventing the color distortion and information loss due to excessive contrast enhancement. It can also remove the noise of the dark regions which is occurred due to the improved contrast through edge preserving filter. Through experimental evaluation of the average color difference comparison of CIELAB color space and the visual assessment, we have confirmed excellent performance of the proposed algorithm compared to conventional MSR algorithm.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1559-1560
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• 2007

BGR mixture phosphor pumped by 400 nm is developed for white-light-emitting diode of liquid crystal display backlight. White-emitting phosphor is prepared by mixing $Ba_2SiO_4:Eu^{2+}$ and $(Ba,Sr)_3MgSi_2O_8:Eu^{2+},Mn^{2+}$ phosphors.