• ETRI Journal
• /
• v.43 no.6
• /
• pp.1093-1102
• /
• 2021

Microdisplays based on organic light-emitting diodes (OLEDs) have a small form factor, and this can be a great advantage when applied to augmented reality and virtual reality devices. In addition, a high-resolution microdisplay of 3000 ppi or more can be achieved when applying a white OLED structure and a color filter. However, low luminance is the weakness of an OLED-based microdisplay as compared with other microdisplay technologies. By applying a tandem structure consisting of two separate emission layers, the efficiency of the OLED device is increased, and higher luminance can be achieved. The efficiency and white spectrum of the OLED device are affected by the position of the emitting layer in the tandem structure and calculated via optical simulation. Each white OLED device with optimized efficiency is fabricated according to the position of the emitting layer, and red, green, and blue spectrum and efficiency are confirmed after passing through color filters. The optimized white OLED device with color filters reaches 97.8% of the National Television Standards Committee standard.

• Analytical Science and Technology
• /
• v.32 no.3
• /
• pp.77-87
• /
• 2019

High viscosity carbon black dispersions are used in various industrial fields such as color cosmetics, rubber, tire, plastic and color filter ink. However, carbon black particles are unstable to heat due to inherent characteristics, and it is very difficult to keep the quality of the product constant due to agglomeration of particles. In general, particle size analysis is performed by dynamic light scattering (DLS) during the dispersion process in order to select the optimum dispersant in the carbon black dispersion process. However, the existing low viscosity analysis provides reproducible particle distribution analysis results, but it is difficult to select the optimum dispersant because it is difficult to analyze the reproducible particle distribution at high viscosity. In this study, dynamic light scattering (DLS) and asymmetrical flow field-flow fractionation (AsFlFFF) analysis methods were compared for reproducible particle size analysis of high viscosity carbon black. First, the stability of carbon black dispersion was investigated by particle size analysis by DLS and AsFlFFF according to milling time, and the validity of analytical method for the selection of the optimum dispersant useful for carbon black dispersion was confirmed. The correlation between color and particle size of particles in high viscosity carbon black dispersion was investigated by using colorimeter. The particle size distribution from AsFlFFF was consistent with the colorimetric results. As a result, the correlation between AsFlFFF and colorimetric results confirmed the possibility of a strong analytical method for determining the appropriate dispersant and milling time in high viscosity carbon black dispersions. In addition, for nanoparticles with relatively broad particle size distributions such as carbon black, AsFlFFF has been found to provide a more accurate particle size distribution than DLS. This is because AsFlFFF, unlike DLS, can analyze each fraction by separating particles by size.

• Current Optics and Photonics
• /
• v.6 no.2
• /
• pp.171-182
• /
• 2022

A single-photon laser and mid-wave infrared (MWIR) common aperture optical system was designed and developed to detect and range a long-distance civil aviation aircraft. The secondary mirror of the Ritchey-Chretien (R-C) optical system was chosen as a dichroic lens to realize the design of a common aperture system for the laser and MWIR. Point spread function (PSF) ellipticity was introduced to evaluate the coupling efficiency of the laser receiving system. A small aperture stop and narrow filter were set in the secondary image plane and an afocal light path of the laser system, respectively, and the stray light suppression ability of the small aperture stop was verified by modeling and simulation. With high-precision manufacturing technology by single point diamond turning (SPDT) and a high-efficiency dichroic coating, the laser/MWIR common aperture optical system with a 𝜑300 mm aluminum alloy mirror obtained images of buildings at a distance of 5 km with great quality. A civil aviation aircraft detection experiment was conducted. The results show that the common aperture system could detect and track long-distance civil aviation aircraft effectively, and the coverage was more than 450 km (signal-to-noise ratio = 6.3). It satisfied the application requirements for earlier warning and ranging of long-range targets in the area of aviation, aerospace and ground detection systems.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.12 no.1
• /
• pp.9-18
• /
• 1987

An electro-optic system using linear photosensitive Charge Coupled Devices(CCDs) having dummy pixels has been proposed for realzation of linear prodictor in the differential pulse code modulation(DPCM). The system consists of three components as conventional system:input light source, spatial filter(mask) and CCD line scanning sensor. For the delay time due to the dummy pixels in CCD, modifying conventional mask, a new dispersive mask is proposed, of which every prediction coefficient is dispersed on the more than one element, the characteristics of the system using the proposed dispersive mask are analyzed theoretically and verified with experiment.

• 한국연소학회:학술대회논문집
• /
• 2006.10a
• /
• pp.53-59
• /
• 2006

This study is measurement of radicals in gas & light oil diffusion flame focused on burner exit. The goal of this study is to analyse the relationship between flame chemiluminescence($OH^{\ast}$, $CH^{\ast}$, $C_2^{\ast}$) intensities and flame conditions. The investigation performed turbulent diffusion flame of commercial burner in varying the excess air ratio from 1.0 to 1.8. The optical emissions were measured by photomultiplier(PMT) using optical band pass filter and spectrometer system. The effects of excess air ratio and NOx emission characteristics on the radical emission intensities were investigated experimentally.

• Proceedings of the KSRS Conference
• /
• 2005.10a
• /
• pp.515-518
• /
• 2005

LiDAR(Light Detection and Ranging) with digital aerial photograph can be used to measure tree growth factors like total height, height of clear-length, dbh(diameter at breast height) and crown projection area. Delineating crown is an important process for identifying and numbering individual trees. Crown delineation can be done by watershed method to segment basin according to elevation values of DSMmax produced by LiDAR. Digital aerial photograph can be used to validate the crown projection area using LiDAR. And tree height can be acquired by image processing using window filter$(3cell\times3cell\;or\;5cell\times5cell)$ that compares grid elevation values of individual crown segmented by watershed.

• Proceedings of the KIEE Conference
• /
• 2003.11b
• /
• pp.71-74
• /
• 2003

The signal processing algorithm for a PSD(Position Sensitive Detector) using amplitude modulation/demodulation is addressed in this paper. Dark currents and external noises such as daylight and fluorescent lights are eliminated by using amplitude modulation/demodulation and a low pass filter. The proposed amplitude modulation/demodulation method for a PSD sensor is compared with pulse amplitude modulation method. The proposed amplitude modulation is proved to be more accurate and robust than PAM method by analysis and experiments. Multiple measurements using one PSD sensor by amplitude modulation/demodulation is also addressed. The Power variation of light source is compensated by normalization process using a divider.

• Journal of Microbiology and Biotechnology
• /
• v.8 no.6
• /
• pp.575-580
• /
• 1998

Cellulase production by batch culture using the Trichoderma reesei Rut C30 strain with various concentrations of Solka Floc with 1 % wheat bran was studied in a 2.5 I fermenter. The cellulase activity increased with Solka Floc concentration up to 5%. When 5% Solka Floc and 1% wheat bran were contained in the medium, carboxymethyl cellulose (CMC) and filter paper (FP) activities were 232.4 U/$m\ell$ and 21.25 U/$m\ell$, respectively. The productivity was 143.6 FPU $1^{-l}h^{-1}$ and the yield was 425 FPU/g. The colonial morphology of T. reesei Rut C30 grown on Avicel agar plates and the changes in mycelial morphology of T. reesei Rut C30 with culture time are also presented.

• Journal of the Korean Society of Combustion
• /
• v.11 no.3
• /
• pp.18-25
• /
• 2006

The present studying is aimed to establish the relationship between flame chemiluminescence$(OH^*,\;CH^*,\;C_2^*)$ intensities and combustion conditions such as $NO_x$ emission characteristics. Measurements are made for $OH^*,\;CH^*,\;C_2^*$ radicals in gas & light oil diffusion flames. At turbulent nonpremixed combustion mode, the equivalence ratio is varied. The optical emissions were measured by photomultiplier(PMT) using optical band pass filter and spectrometer system. The experimental results showed that the ratio of radicals and $NO_x$ emission characteristics have exponential correlations and equivalence ratio characteristics have linear correlations at this experimental conditions.

• Bulletin of the Korean Space Science Society
• /
• 2008.10a
• /
• pp.29.2-29.2
• /
• 2008

The CCD photometric observations of the W UMa type contact binary GX Aur were performed for 33 nights from 2004 to 2008 using a 2K CCD camera and Johnson BVRI filter system attached to the 61cm reflector at Sobaeksan Optical Astronomy Observatory (SOAO). From our observations, the first BVRI light curves of GX Aur were completed and eight new times of minima (primary: 4, secondary: 4) were obtained. All the times of minima including our timings were collected and analyzed to see the dynamical behavior of GX Aur system. Intensive analysis of our BVRI lightcurves with the recent Wilson-Devinney binary model shows that GX Aur is an over-contact binary whose component stars have equal mass and time-variable spots.