• Laser Solutions
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• v.10 no.1
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• pp.29-34
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• 2007

We propose a novel application of laser engraving to patterning of light guide panel (LGP) for backlight. The feasibility of three-dimensional engraved pattern in the LGP was verified by measuring brightness and uniformity. To improve the overall uniformity, we have modified proposed patterns and found improved design for patterns. The tailoring of pattern by using laser engraving method could endow the controllability of uniformity. The proposed LGPs are more efficient in both average brightness and uniformity of illumination than the conventional LGPs which have surface pattern on the panel.

• Journal of Power Electronics
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• v.10 no.4
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• pp.351-356
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• 2010

A new current-balancing multi-channel LED driver is proposed in this paper. The conventional LED driver system consists of three cascaded power conversion stages and its driver stage has the same number of expensive boost converters as those of the LED channels. On the other hand, the proposed LED driver system consists of two cascaded power stages and its driver stage requires only passive devices instead of expensive boost converters. Nevertheless, all of the currents through multi-channel LEDs can be well balanced. Therefore, it features a smaller system size, improved efficiency, and lower cost. To confirm the validity of the proposed driver, its operation and performance are verified on a prototype for a 46" LCD TV.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.375-376
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• 2007

In this work, we have simulated a 42-inch LED BLU which was based on 300 RGB LEDs. We have done an adjustment of LEDs' strip distance and a height of the top of the LED to the back of the LCD to get white color uniformity. So, we have changed simultaneously the distance between the top of the LEDs and the back of the LCD. Moreover, we set a fixed position for the horizontal of LED's pitch. And then, we have experimented and compared to our simulation data.

• Journal of Information Display
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• v.9 no.1
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• pp.26-32
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• 2008

The dependence of optical performances of collimating films such as prism films and pyramid films on the reflecting properties of reflection films were investigated by using a ray tracing technique. The angular distribution of the luminance and the on-axis luminance gain were obtained by using a simple backlight model composed of a reflection film, a virtual flat light source, and a collimating film. Three kinds of reflecting properties were used, which were a perfect Lambertian reflector, a perfect mirror reflector, and a reflector having both diffuse and specular properties. It was found that the on-axis luminance gain was the highest in the simulation where a mirror reflector was used, while the viewing angle was the widest where the Lambertian reflector was used. This result indicates that it is necessary to optimize the simulation condition such as the reflecting properties in order to predict the optical performances of collimating films accurately. Quantitative correlation between the optical characteristics of collimating films and the reflecting properties of reflection films can be used to improve simulation technique for the development and the optimization of collimating films for LCD backlight applications.

• Korean Journal of Optics and Photonics
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• v.21 no.6
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• pp.247-253
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• 2010

A dual-layer light guide plate (DLGP) was designed and a simulation was done to optimize the structure of the light guide plates used at backlight units while maintaining the luminance, uniformity and viewing angle by reducing the optical sheet. The characteristic of DLGP with prism pattern with curvature on the top surface is simulated and the luminance and uniformity are obtained. In order to improve the uniformity, the V groove prism pattern on the bottom surface was turned by an angle of $90^{\circ}$. In particular, we used the pitch calculation program to select the value of the ratio (Max : Min) between the pitch at the extreme outside and the pitch at the middle, the number of V groove lines and the variance at the bottom pattern of DLGP. After that, the optimum distance between V grooves was determined. For optimizing the DLGP, we examined the uniformity again by changing the number of pattern grooves on the bottom surface of DLGP. As a result of the simulation, we find that the BLU with DLGP has a uniformity of 90.6% and viewing angle $145^{\circ}$.

• 전자공학회논문지 IE
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• v.46 no.4
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• pp.57-65
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• 2009

This paper presents the image contrast enhancement technique suitable for local dimming backlight of small-sized mobile display while achieving the reduction of the power consumption. In addition to the large-sized TFT-LCD, small-sized one has adopted LED for backlight. Since, conventionally, LED was mounted on the side edge of a display panel, global dimming method has been widely used. However, recently, new advanced method of local dimming by placing the LED to the backside of the display panel and it raised the necessity of sub-blocked processing after partitioning the target image. When the sub-blocked image has low brightness, the supply current of a backlight LED is reduced, which gives both enhancement of contrast ratio and power consumption reduction. In this paper, we propose simple and improved image enhancement algorithm suitable for the small-sized mobile display. After partitioning the input image by equal sized blocks and analyzing the pixel information in each block, we realize the primary contrast enhancement by independently processing the sub-blocks using the information such as histogram, mean, and standard deviation values of luminance(Y) component. And then resulting information is transferred to each backlight control unit for local dimming to realize the secondary contrast enhancement as well as reduction of power consumption.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.158-161
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• 2001

Light guide can be manufactured with a several method dot-screen method, injection method and DSF method. The advantage of DSF method is three-dimensional optical distribution.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.1262-1265
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• 2004

To increase the performance of the light diffusion films, we controlled the three dimensional microstructure of the organic fillers(beads). The refractive index, the size distribution and the three dimensional distribution of beads play an important role to determine the performance of light diffusion films for the backlight unit of TFT-LCD.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1577-1579
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• 2007

Xe content is one of important factors related to characteristics of the mercury-free flat fluorescent lamp. The electro-optical properties of lamp were investigated for wide range of Xe content in Xe-Ne mixing gas. The maximum luminance of $9,289\;cd/m^2$ and efficacy of 3 lm/W was obtained with Xe 90 %.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.940-943
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• 2007

The objective of the research presented in this paper is to design a highly efficient LCD-TV backlight unit (BLU) which minimizes lamp count without light leakage from the BLU. A new optical plate helps to successfully distribute spatial luminance in a 46inch LCD-BLU consisting of only 20 CCFLs.