• Korean Journal of Optics and Photonics
• /
• v.11 no.4
• /
• pp.261-264
• /
• 2000

Continuous ND filters are fabricated on the silver halide photoplates. These filters enable us to get intensity modulated laser beam. Two kinds of continuous ND filters are fabricated. Optical density of one filter is increased radically and that of the other is decreased. In order to get a filter having desirable optical density, a mask which has reversed optical density has to be made. made.

• The Bulletin of The Korean Astronomical Society
• /
• v.46 no.2
• /
• pp.78.3-79
• /
• 2021

Coronal Diagnostic Experiment (CODEX) is a diagnostic coronagraph developed by the Korea Astronomy and Space Science Institute and the NASA Goddard Space Flight Center (GSFC) to be deployed in 2023 on the International Space Station (ISS). It is designed to obtain simultaneous measurements of electron density, temperature, and velocity in the 2.5 - 10 solar radius range using multiple filters. The filters are mounted in two filter wheel assemblies (FWAs), which have five filter positions each. One position of each FWA is occupied by windows, and remaining eight positions are occupied by three bandpass filters for temperature, two bandpass filters for velocity, one Ca II H filter for F-corona, one broadband filter for fast imaging and density, and one neutral density (ND) filter for direct Sun viewing and safety.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.36 no.6
• /
• pp.466-473
• /
• 2016

In a shipbuilding process, thermal damage to the ship structure at the rear end results from an excessive heat input and conduction during welding process. To prevent such damage, appropriate control of the heat input, based on welding temperature measurement, is required. For temperature measurement, contact and non-contact methods are available; the thermography system is a popular non-contact temperature measurement. When the intensity of radiation from a high-temperature object is excessive, however, detecting the sensors of ordinary thermography systems leads to an inability in measuring the temperature due to saturation. Hence, this study suggests use of a neutral density filter that prevents an excessive amount of radiation from being accumulated in a thermography system, and thus makes it possible to quantitatively measure an object's temperature as high as $3000^{\circ}C$.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
• /
• 2009.04a
• /
• pp.65-73
• /
• 2009

The terrestrial laser scanner measures the signal delay time of electronic circuit in EDM(Electronic Distance Measurement) Module for distance measurement. To measure signal delay time precisely, transmitting laser beam of terrestrial laser scanner is divided optically. Therefore, 10% of the laser beam power is entered into the electronic circuit and the others go out through lens. But, measure of delay time is severe in the laser scanner system that the laser beam power is changed dynamically by reflectance of a object, because characters like gain of electronic circuit involving APD(Avalanche Photo Diode) and so on are changed by incident laser beam. Therefore, we adapt ND(Neutral Density) filter that has grid pattern to the laser scanner system to keep constant the incident laser beam power. In this paper, we propose the simulation program for efficient design of ND filter pattern. Finally, to affirm simulation program, we conduct the experimental test of simulated ND filter that has linearly transmittance change, and we consider the experiment result.

• Journal of Korean Society for Atmospheric Environment
• /
• v.21 no.E2
• /
• pp.49-56
• /
• 2005

A long-path transmissometer is one of the optical instruments widely used to measure atmospheric light extinction coefficient without enclosing a light beam and perturbing aerosols. Over the past two decades, a number of measurements have been carried out using the long-path transmissometer manufactured by OPTEC, Inc. Calibration of the transmissometer should be performed when any component of the transmissometer system is interchanged or installation condition is changed. For a better calibration of the transmissometer, application of a modified calibration method for the existing neutral density (ND)-filter method was recommended for the computation of the atmospheric transmittance using model MODTRAN 4 in this study. It was revealed that the measured light extinction coefficient from the transmissometer which was calibrated using the existing ND-filter method could be overestimated due to the assumption of the atmospheric transmittance suggested by OPTEC, Inc. The uncertainty of the measured light extinction coefficient from the transmissometer calibrated based on the modified ND-filter method was calculated to be approximately $13Mm^{-1}$.

• Journal of Welding and Joining
• /
• v.27 no.6
• /
• pp.9-16
• /
• 2009

In this paper, the coaxial monitoring system to capture image of weld pool was developed in laser-arc hybrid welding. In order to obtain the reliable image, green laser was used as a illumination system and measuring components such as band pass filter, ND (Neutral Density) filter and shutter speed was designed and optimized. Using this monitoring system, weld pool images were captured according to laser power, welding speed, welding current and interspace between laser and arc through the experiment. ANOVA (Analysis of Variation) was carried out to identify the influence of process variables on bead widths extracted from captured images of monitoring system. Welding speed and current were major factor to affect weld pool.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.525-525
• /
• 2013

Low temperature plasma diagnosis is one of the big issues in laboratory scale or processing industry. One of the most powerful techniques of plasma diagnostics is the use of the scattering of electromagnetic radiation from the plasma. Electron temperature and density are important parameters for understanding the information of plasmas in the plasma processing industry. Laser scattering experiments on plasma can provide a substantial amount of information about plasma parameters such as the electron density ne, the electron temperature Te, and the neutral density nn and temperature Tn. Thomson scattering spectroscopy is used several method, in accordance with detector type. Commonly, Thomson scattering is used several notch filter to separate expanded wavelength. Since using a spectrometer with surface relief grating or notch filter, the system of the measurement will be complicated and bigger. In this study, using VPHG (Volume Phase Holographic Grating) in order to install the simple and cheap system. VPHG has the advantage of the system installation, because it can be Transmission Type. The diffraction efficiency and dispersion angle of VPHG is higher than the surface relief grating relatively. For a wavelength and bandwidth selection, Using a slit or mask to select a rejection wavelength instead of notch filter.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.56 no.12
• /
• pp.2122-2126
• /
• 2007

A special PM-Tube(Photo Multiplier Tube) that is using the photoelectric effect has been designed and manufactured to measure the radiation energy of arc in a gas circuit breaker(GCB). The PM-Tube, LLG(liquid light guides), ND(neutral density) filter, and a model gas circuit breaker have been combined for the reception and the transmission of the light and a simplified synthetic test facility with the arc energy measuring system has been established. In the case of $SF_6$ gas pressure $5kg.f/cm^2$ and arc length 20mm, the radiation energy increases with the arc current but it tend to be saturated in the above 20kA. Under the arc current 20kA, the total radiation energy has the biggest value around 8kA and was not exceeded 40% of the total arc energy.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.12
• /
• pp.804-815
• /
• 2019

Due to the depletion and environmental problems of fossil fuel, biomass has arisen as an alternative energy source. Biomass is a renewable and carbon-neutral source. However, it is moister and has lower energy density. Therefore, biomass needs thermal chemical conversion processes like gasification, and it does not only produce a flammable gas, called 'syngas', which consists of CO, H2, and CH4, but also some unwanted byproducts such as tars and some particulates. These contaminants are condensed and foul in pipelines, combustion chamber and turbine, causing a deterioration in efficiency. Thus this work attempted to find a method to remove tars and particles from syngas with a filter which adopts a pre-coating technology for preventing blockage of the filter medium. Hydrated limestone powder and activated carbon(wood char) powder were used as the pre-coat materials. The removal efficiency of the tars was 86 % and 80 % with activated carbon(wood char) coating and hydrated limestone coating, respectively.