• Korean Journal of Optics and Photonics
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• v.30 no.5
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• pp.197-203
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• 2019

In this paper, we studied a reflector design that can improve the illuminance uniformity when using a xenon flash lamp in the photonic sintering process. To achieve complete sintering of substrates in the irradiated area, the light efficiency and illuminance uniformity were set to target performance. Existing elliptical reflectors or parabolic reflectors make it easy to satisfy the target light efficiency, but have difficulty satisfying the illuminance uniformity. In this paper, a twin-concave feature has been added to the center of the parabolic reflector to satisfy the illuminance uniformity. It was confirmed that the illuminance uniformity of the parabolic reflector with a twin-concave feature was improved, compared to that of the traditional reflector.

• Journal of the Optical Society of Korea
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• v.20 no.5
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• pp.586-592
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• 2016

This paper proposes a luminance compensation method using optical sensors to achieve high luminance uniformity of active matrix organic light-emitting diode (AMOLED) displays. The proposed method compensates for the non-uniformity of luminance by capturing the luminance of entire pixels and extracting the characteristic parameters. Data modulation using the extracted characteristic parameters is performed to improve luminance uniformity. In addition, memory size is optimized by selecting an optimal bit depth of the extracted characteristic parameters according to the trade-off between the required memory size and luminance uniformity. To verify the proposed compensation method with the optimized memory size, a 40-inch 1920×1080 AMOLED display with a target maximum luminance of 350 cd/m² is used. The proposed compensation method considering a 4σ range of luminance reduces luminance error from ± 38.64%, ± 36.32%, and ± 43.12% to ± 2.68%, ± 2.64%, and ± 2.76% for red, green, and blue colors, respectively. The optimal bit depth of each characteristic parameter is 6-bit and the total required memory size to achieve high luminance uniformity is 74.6 Mbits.

• Journal of the Optical Society of Korea
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• v.17 no.2
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• pp.213-218
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• 2013

Although infrared focal plane array (IRFPA) detectors have been commonly used, non-uniformity correction (NUC) remains an important problem in the infrared imaging realm. Non-uniformity severely degrades image quality and affects radiometric accuracy in infrared imaging applications. Residual non-uniformity (RNU) significantly affects the detection range of infrared surveillance and reconnaissance systems. More effort should be exerted to improve IRFPA uniformity. A novel NUC method that considers the surrounding temperature variation compensation is proposed based on the binary nonlinear non-uniformity theory model. The implementing procedure is described in detail. This approach simultaneously corrects response nonlinearity and compensates for the influence of surrounding temperature shift. Both qualitative evaluation and quantitative test comparison are performed among several correction technologies. The experimental result shows that the residual non-uniformity, which is corrected by the proposed method, is steady at approximately 0.02 percentage points within the target temperature range of 283 K to 373 K. Real-time imaging shows that the proposed method improves image quality better than traditional techniques.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.1
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• pp.114-119
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• 2011

There is a limit to technology of improving luminous intensity uniformity and glare, known as a weakness of existing LED lamp. Because of Using many LED, LED lamp not only waste energy but have bad effect on efficiency. Our goal is to develop security lights solution which is contented with suitable area in KS(Korean Industrial Standards) and to remove glare by combining asphere in optical system with different concept. To improve luminous intensity uniformity, a reflect mirror system was used after an aspheric optical system design for this study. We made a mirror and measured it after analysing luminance changes depend on aspheric shapes with simulation program to see if aspheric shapes effect luminance distribution. We made progress to find problems and improve them by comparing measured data and analysed data. This result of the study will contribute to industry of LED lighting through developing solution of emotional illumination of LED security lights by knowing the importance of reflectivity with this study and improving luminous intensity uniformity with solving the problem.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.483-486
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• 2004

A CCD-based color uniformity measurement system was set up. Through measuring the two-dimensional brightness distributions of three primary colors on the screen, chromaticity coordinate distributions of combination gray can be obtained within a few seconds. This system can be widely used in the production of LCD projection.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.4
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• pp.62-72
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• 1997

The optical power splitter/couplers based on MMI(multimode interference) in GaAs/AlGaAs are studied. We presetn a design of optical power splitter/couplers, which have deeply etched multimode waveguide. The properties and fabrication tolerance on the etching depth, multimode waveguide width are simulatedusing a FD-BPM (finite difference beam propgation method). Proposed 1*N optical of designed device is 0.7dB smaller than the optical power splitter with a shallowly etched MMI section. For 0.5dB excess loss, the predicted fabrication tolerance is 0.6.mu.m on the multimode waveguide width of the 14 optical power splitter with a deeply etched MMI section. Also excess loss and uniformity of poposed 32*32 optical power coupler are below 0.3dB. The excess loss of proposed 32*32 optical power coupler is 2dB smaller than the optical power coupler with a shallowly etched MMI section. It is shown that the optical power splitters/couplers with a deeply etched mMI section have low loss, good uniformity, and improved fabriction tolerance.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.692-695
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• 2008

Large area emissive displays have problems with nonuniform pixel characteristics and their individual ageing. A pixel integrated driver with pixel based optical feedback is presented to solve these problems. Photodetectors, optical feedback circuit and data handling capabilities are integrated in a high voltage CMOS technology.

• Proceedings of the Optical Society of Korea Conference
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• 2009.10a
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• pp.298-299
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• 2009

Use of a DLP-beam projector is proposed to measure solar cell quantum efficiency distribution. The measurement requires a good spatial uniformity of the beam from the projector. We measured the spectral power distribution of the beam projector and the spatial uniformity of the white beam. By changing the gray level of the white beam at the measured spatial points, we improved the spatial illuminance uniformity to be about 2 % which was otherwise as much as 400 %.

• Transactions of the Society of Information Storage Systems
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• v.9 no.1
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• pp.10-16
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• 2013

Through the rapid development of LED TV, a large-area edge-lit backlight unit is widely researched in the display industry for enhancing the optical efficiency, luminous uniformity and slim design. In addition, an edge-lit backlight unit includes many optical sheets such as reflection sheet, prism sheet and diffuser sheet. However the function can be replaced by the carefully patterned light guide plate (LGP). Micro patterns which located on the top and bottom surface of light guide plate was designed by ray-tracing optical simulation. The designed patterns improved the light characteristics of LGP, including optical extraction efficiency and intensity distribution uniformity. These results suggest that it is very effective method to design edge-lit LGP with micro-patterns on both sides for large-area display and to reduce the fabrication cost.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.10a
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• pp.73-76
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• 2009

The optical structure of edge-lit LED backlight has been optimized via simulation study in order to remove bright spots appearing on the entrance region of the light guide plate (LGP) and thus to improve the luminance uniformity. The density of scattering dots located on the back surface of LGP was adjusted according to the location of LED's. In addition, lenticular lenses or a diffuse transmissive surface were formed on the side surface of LGP facing the LED's, and the density of lenticular lenses was optimized for redistributing rays emitted from LED's into wider angles. The bright spots which could be seen from conventional LED backlight were removed by the combination of these two optical structures. The application of diffuse surface to the entrance face gave better uniformity than the application of lenticular lenses. However, dark regions still appear on the entrance region of LGP, which should be removed by more appropriate optical design for achieving better luminance uniformity on the LED backlight.