• Electronics and Telecommunications Trends
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• v.36 no.3
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• pp.97-105
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• 2021

The terahertz wave (THz wave) is a band between infrared and microwaves and is defined as an electromagnetic wave having a frequency of 0.1 to 10 THz band. THz waves have the property of transmitting nonpolar materials, which the visible light cannot be transmitted, such as ceramics, plastics, and paper; and the photon energy is low, such as several meV. For this reason, non-destructive testing equipment based on THz imaging technology can be applied to the industrial field. Recently, THz imaging technology was applied in wide industrial fields, such as automobiles, batteries, food, medical, and security, and being actively studied. In this paper, we describe the research trends of terahertz imaging technology and experimental results. Furthermore, we summarize the recent commercialized terahertz camera. Finally, we present the research results in the field of the human security scanner system.

• Korean Journal of Optics and Photonics
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• v.32 no.6
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• pp.286-295
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• 2021

A modified catadioptric omnidirectional optical system (MCOOS) using an RGB/NIR CMOS sensor is optically designed for a capsule endoscope with the front field of view (FOV) in visible light (RGB) and side FOV in visible and near-infrared (NIR) light. The front image is captured by the front imaging lens system of the MCOOS, which consists of an additional three lenses arranged behind the secondary mirror of the catadioptric omnidirectional optical system (COOS) and the imaging lens system of the COOS. The side image is properly formed by the COOS. The Nyquist frequencies of the sensor in the RGB and NIR spectra are 90 lp/mm and 180 lp/mm, respectively. The overall length of 12 mm, F-number of 3.5, and two half-angles of front and side half FOV of 70° and 50°-120° of the MCOOS are determined by the design specifications. As a result, a spatial frequency of 154 lp/mm at a modulation transfer function (MTF) of 0.3, a depth of focus (DOF) of -0.051-+0.052 mm, and a cumulative probability of tolerance (CPT) of 99% are obtained from the COOS. Also, the spatial frequency at MTF of 170 lp/mm, DOF of -0.035-0.051 mm, and CPT of 99.9% are attained from the front-imaging lens system of the optimized MCOOS.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.2
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• pp.13-19
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• 2012

Ultra Precision Machining Techniques, such as manufacturing Micro Lens Array(MLA), off-axis mirror, $F-{\theta}$ lens for laser printer, are achieved, based on technologies in consequence of development of modern high-precision machining mechanism. Above all, FTS(Fast Tool Servo) and STS(Slow Tool Servo) are more innovative technologies for reducing time and development costs. In this paper, it is described that MLA machining technique by FTS, off-axis mirror machining technique by STS, optics for observing space, and development of infrared aspheric lens for a thermal imaging microscope.

• Journal of Sensor Science and Technology
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• v.18 no.2
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• pp.135-138
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• 2009

$64{\times}1$ forcal plane infrared detector has been fabricated by using HgCdTe epi layer. HgCdTe was grown on GaAs substrate by using metal organic chemical vapor deposition. This paper describes key developments in the epi layer growth and device fabrication process. The performance of IR imaging system is summarized.

• Journal of the Korea Institute of Military Science and Technology
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• v.9 no.2 s.25
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• pp.111-117
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• 2006

This paper describes the design principles and methods of electronic processor for thermal imager with 320$\times$240 staring array infrared detector. For the detector's nonuniformity correction and excellent image quality, we have designed the multi-point correction method using the defocusing technique of the optics. And to enhance the image of low contrast and improve the detection capability, the new technique of histogram processing has been designed. Through these image processing techniques, we have developed the high quality thermal imager and acquired a satisfactory thermal image. The result of MRTD(Minimum Resolvable Temperature Difference) is $0.1^{\circ}C$ at 4cycles/mard.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.324-325
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• 2014

Quantum wells infrared photodetectors (QWIPs) have been used to detect infrared radiations through the principle based on the localized stated in quantum wells (QWs) [1]. The mature III-V compound semiconductor technology used to fabricate these devices results in much lower costs, larger array sizes, higher pixel operability, and better uniformity than those achievable with competing technologies such as HgCdTe. Especially, GaAs/AlGaAs QWIPs have been extensively used for large focal plane arrays (FPAs) of infrared imaging system. However, the research efforts for increasing sensitivity and operating temperature of the QWIPs still have pursued. The modification of heterostructures [2] and the various fabrications for preventing polarization selection rule [3] were suggested. In order to enhance optical performances of the QWIPs, double barrier quantum well (DBQW) structures will be introduced as the absorption layers for the suggested QWIPs. The DBWQ structure is an adequate solution for photodetectors working in the mid-wavelength infrared (MWIR) region and broadens the responsivity spectrum [4]. In this study, InGaAs/GaAs/AlGaAs double barrier quantum well infrared photodetectors (DB-QWIPs) are successfully fabricated and characterized. The heterostructures of the InGaAs/GaAs/AlGaAs DB-QWIPs are grown by molecular beam epitaxy (MBE) system. Photoluminescence (PL) spectroscopy is used to examine the heterostructures of the InGaAs/GaAs/AlGaAs DB-QWIP. The mesa-type DB-QWIPs (Area : $2mm{\times}2mm$) are fabricated by conventional optical lithography and wet etching process and Ni/Ge/Au ohmic contacts were evaporated onto the top and bottom layers. The dark current are measured at different temperatures and the temperature and applied bias dependence of the intersubband photocurrents are studied by using Fourier transform infrared spectrometer (FTIR) system equipped with cryostat. The photovoltaic behavior of the DB-QWIPs can be observed up to 120 K due to the generated built-in electric field caused from the asymmetric heterostructures of the DB-QWIPs. The fabricated DB-QWIPs exhibit spectral photoresponses at wavelengths range from 3 to $7{\mu}m$. Grating structure formed on the window surface of the DB-QWIP will induce the enhancement of optical responses.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.55.2-55.2
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• 2015

NISS is a unique spaceborne imaging spectrometer (R = 20) onboard the Korea's next micro-satellite NEXTSat-1 to investigate the star formation history of Universe in near infrared wavelength region (0.9 - 3.8 um), with a customized H1RG IR sensor(Jeong 2014). In this paper, we will introduce the compact electronics system (Fig. 1) as well as the novel readout method to reduce the 1/f noise for NISS.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.207-208
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• 2011

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.5
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• pp.421-426
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• 2009

The emissivity is different because the emitted angle changes according to the position of the infrared thermography camera and object. Because of this, the temperature distribution expressed when measuring the temperature by using the infrared thermography system is not the accuracy temperature. Although the real surface temperature is constant, the temperature measured by using infrared thermography camera have error in accordance with the value of emissivity. In this paper, the temperatures of the round cylindrical object and the flat square object that heated to the equal temperature were measured by infrared thermography camera. The emissivity calibration formula and correction table are made with the affect of the view angle and emission angle form the surface temperature value. The error of measured temperature values are corrected by using the emissivity calibration formula and correction table, and apply to defect detection of the nuclear power plant pipe. From the calibration method, reliability surface temperature values were obtained.

• Aerospace Engineering and Technology
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• v.10 no.2
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• pp.29-36
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• 2011

The Science and Technology Satellite-3 (STSAT-3) is based on the KITSAT-1, 2, 3 and STSAT-1, 2 which were Korea micro-satellites for the mission of space and earth science. The objectives of the STSAT-3 are to support earth and space sciences in parallel with the demonstration of spacecraft technology. The STSAT-3 carries an infrared (IR) camera for space & earth observation and an imaging spectrometer for earth observation. The IR payload instrument of the STSAT-3, Multi-purpose Infrared Imaging System (MIRIS), will observe the Galactic plane and North/South Ecliptic poles to research the origin of universe. The secondary payload instrument, Compact Imaging Spectrometer (COMIS), images the Earth's surface. The data acquired from COMIS are expected to be used for various application fields such as monitoring of disaster management, water quality studies, and farmland assessment. In this paper we present the operations concept of STSAT-3 which will be launched into a sun-synchronous orbit at a nominal altitude of 600km in late 2012.