• Title/Summary/Keyword: Quadrant detector

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Phase Difference Detector for Satellite Tracking Based on Field Experiments of COMETS

  • Ta, Masuhisa;Nakajima, Isao;Juzoji, Hiroshi
    • Journal of Multimedia Information System
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    • v.5 no.3
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    • pp.155-162
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    • 2018
  • Nowadays, the tracking technology of Quadrant Detector will become actual by new micro devices. Based on the past filed data of the reception experiment with COMETS satellite, we have studied on new device (AD8302, phase difference detector) was acquired and suspect its abilities. In 1998, we have developed a Quadrant Detector for mobile to track a weak signal from satellite on Ka band of COMETS. The Quadrant Detector is comprised of four dedicated feed components for reception under an environment of Nakagami - Rician fading, and one transmission and reception feed component. We were successful in receiving a 23 GHz beacon signal from ICE transponder of the COMETS and succeeded in tracking the satellite from a moving vehicle at speeds of approximately 10 ~ 20 Km/h on paved roads. In 2018, with new device AD8302, we have verified new QD system and performed a simulation, based on the past filed experiment. This new device shall be improving the tracking abilities from mobile body on the earth to the multimedia satellite.

Similarity analysis of pixelated CdTe semiconductor gamma camera image using a quadrant bar phantom for nuclear medicine: Monte Carlo simulation study

  • Park, Chan Rok;Kang, Seong-Hyeon;Lee, Youngjin
    • Nuclear Engineering and Technology
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    • v.53 no.6
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    • pp.1947-1954
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    • 2021
  • In the nuclear medicine imaging, quality control (QC) process using quadrant bar phantom is fundamental aspect of evaluating the spatial resolution. In addition, QC process of gamma camera is performed by daily or weekly. Recently, Monte Carlo simulation using the Geant4 application for tomographic emission (GATE) is widely applied in the pre-clinical nuclear medicine field for modeling gamma cameras with pixelated cadmium telluride (CdTe) semiconductor detector. In this study, we modeled a pixelated CdTe semiconductor detector and quadrant bar phantom (0.5, 1.0, 1.5, and 2.0 mm bar thicknesses) using the GATE tool. Similarity analysis based on correlation coefficients and peak signal-to-noise ratios was performed to compare image qualities for various source to collimator distances (0, 2, 4, 6, and 8 cm) and collimator lengths (0.2, 0.4, 0.6, 0.8, and 1.0 cm). To this end, we selected reference images based on collimator length and source to collimator distance settings. The results demonstrate that as the collimator length increases and the source to collimator distance decreases, the similarity to reference images improves. Therefore, our simulation results represent valuable information for the modeling of CdTe-based semiconductor gamma imaging systems and QC phantoms in the field of nuclear medicine.

Evaluation of Image Quality by Using Various Detector Materials according to Density : Monte Carlo Simulation Study (몬테카를로 시뮬레이션 기반 밀도에 따른 다양한 검출기 물질을 적용한 획득 영상 평가)

  • LEE, Na-Num;Choi, Da-Som;Lee, Ji-Su;Park, Chan-Rok
    • Journal of radiological science and technology
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    • v.44 no.5
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    • pp.459-464
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    • 2021
  • The detector performance is important role in acquiring the gamma rays from patients. Among parameters of detector performances, there is density, which relates to respond to gamma rays. Therefore, we confirm the detection efficiency according to various detector materials based on the density parameter using GATE (geant4 application for emission tomography) simulation tool. The NaI (density: 3.67 g/cm3), CZT (Cadimium Zinc Telluride) (density: 5.80 g/cm3), CdTe (Cadmium Telluride) (5.85 g/cm3), and GAGG (Gadoinium Aluminum Gallium Garnet) (density g/cm3) were used as detector materials. In addition, the point source and quadrant bar phantom, which is modeled for 0.5, 1.0, 1.5, and 2.0 mm thicknesses, were modeled to confirm the quatitative analysis using sensitivity (cps/MBq) and the full width at half maximum (FWHM, mm) at the 2.0 mm bar thickness containing visual evaluation. Based on the results, the sensitivity for NaI, CZT, CdTe, and GAGG detector materials were 0.12, 0.15, 0.16, and 0.18 cps/MBq. In addition, the FWHM for quadrant bar phantom in the 2.0 mm bar thickness is 3.72, 3.69, 3.70, and 3.73 mm for NaI, CZT, CdTe, and GAGG materials, respectively. Compared with performance of detector materials according to density, the high density can improve detection efficiency in terms of sensitivity and mean count. Among these detector materials, the GAGG material is efficient for detection of gamma rays.

Effect of the Incident Optical Spot Size Upon the Quadrant Photodetector on the Optical Displacement Detection Sensitivity (4분할 광 검출기 상의 광점 크기가 변위 측정감도에 미치는 영향)

  • Lee, Eun-Joong;Lee, Jin-Woo;Kouh, Tae-Joon
    • Journal of the Korean Magnetics Society
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    • v.18 no.2
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    • pp.71-74
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    • 2008
  • In this paper, we have measured the effect of the optical spot size, incident upon the quadrant photodetector, on the optical displacement sensitivity of the optical beam deflection technique. We have built an optical displacement detection system based on the optical beam deflection method using 3 mW He-Ne laser and measured the displacement sensitivity with changing the optical spot size on the quadrant photodetector. We have also calculated the changes in the optical displacement sensitivity as a function of the incident laser spot size by modeling a circular optical spot with constant laser intensity. Our experimental and theoretical studies show that the optical displacement sensitivity increases with the decrease in the optical spot size. This suggests that in the design of the optical motion detection systems with sub-nanometer sensitivity, the displacement sensitivity can be optimized by reducing the size of the incident optical spot on the detector.

A study on multi degrees of freedom fine motion measurement for milli-structure (밀리구조물의 다자유도 미세 변위 측정법에 대한 연구)

  • 배의원;김종안;김수현;곽윤근
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2000.11a
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    • pp.39-42
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    • 2000
  • Cutrent technological development toward miniaturization requires smaller components. These components usually generate complex multi-DOF motions other than simple 1-DOF motlon. Therefore it is essential to develop measurement methodology for 6-DOF motions. In this paper, a new 6-DOF measurement system for milli-struchlre is presented. This methodology basically employs the Optical Beam Deflection Method (OBDM) with a diffraction grating. A laser beam is emitted toward the difliaction grating which could be attached on the surface of a milli-structue and the incident ray is dif'||'&'||'acted in several directions. Among these difliacted beams, $0^{th}$ and $\pm$ $1^{th}4" order difkicted rays are detected by 4 Quadrant Photodiodes. From coordinate values fram each detector, we can get information for 6-DOF motions with lineariration method, Required resolutions for milli-struchue measurement are suh-micrometer in translation and arcsec in rotation. Experimental results indicate that proposed system has possibility to satisfy this requirement.

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Study on Modeling and Experiment of Optical Three Axis Tool-Origin Sensor for Applications of Micro Machine-Tools (초소형 공작기계 적용을 고려한 광학식 3 축 공구원점 센서 모델링 및 실험에 관한 연구)

  • Shin, Woo-Cheol;Lee, Hyeon-Hwa;Ro, Seung-Kook;Park, Jong-Kweon;Noh, Myoung-Gyu
    • Journal of the Korean Society for Precision Engineering
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    • v.26 no.6
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    • pp.68-73
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    • 2009
  • One of the traditional optical methods to monitor a tool is a CCD sensor-based vision system which captures an aspect of the tool in real time. In the case using the CCD sensor, specific lens-modules are necessary to monitor the tool with higher resolution than its pixel size, and a microprocessor is required to attain desired data from captured images. Thus theses additional devices make the entire measurement system complex. Another method is to use a pair of an optical source and a detector per measuring axis. Since the method is based on the intensity modulation, the structure of the measurement system is simper than the CCD sensor-based vision system. However, in the case measuring the three dimensional position of the tool, it is difficult to apply to micro machine-tools because there may not be space to integrate three pairs of an optical source and a detector. In this paper, in order to develop a tool-origin measurement system which is employed in micro machine-tools, the improved method to measure a tool origin in x, y and z axes is introduced. The method is based on the intensity modulation and employs one pair of an optical source radiating divergent beams and a quadrant photodiode to detect a three dimensional position of the tool. This paper presents the measurement models of the proposed tool-origin sensor. The models were verified experimentally The verification results show that the proposed method is possible and the induced models are available for design.

Development a simple MEMS-based astronomical adaptive optics system at laboratory

  • Yu, Hyung-Jun;Park, Yong-Sun;Chae, Jong-Chul;Yang, Hee-Su
    • The Bulletin of The Korean Astronomical Society
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    • v.36 no.2
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    • pp.132.2-132.2
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    • 2011
  • We are developing Adaptive Optics (AO) system for astronomical use. The He-Ne laser works as an artificial light source. The tip-tilt correction servo is added to our AO system. The tip-tilt term, among the Zernike terms, is the biggest contributor of wavefront deformation caused by atmospheric turbulence at small telescopes. The tip-tilt correction servo consists of a Piezo tip-tilt platform with a mirror, a quadrant photodiode as a tip-tilt sensor, and controllers. The Shack-Hartmann wavefront sensor measures the residual wavefront errors and they are corrected by the MEMS (Micro Electro Mechanical System) deformable mirror. The MEMS deformable mirror allows the compact size at low cost compare to adaptive secondary mirror and other deformable mirrors. As the frame rates of the MEMS deformable mirror is about tens of kHz, the frame rates of the detector in wavefront sensor is the bottleneck of the wavefront correction speed. For faster performance, we replaced a CCD which provides frame rates only 70 Hz with a CMOS with frame rates up to 450 Hz.

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DEVELOPMENT OF THE READOUT CONTROLLER FOR INFRARED ARRAY (적외선검출기 READOUT CONTROLLER 개발)

  • Cho, Seoung-Hyun;Jin, Ho;Nam, Uk-Won;Cha, Sang-Mok;Lee, Sung-Ho;Yuk, In-Soo;Park, Young-Sik;Pak, Soo-Jong;Han, Won-Yong;Kim, Sung-Soo
    • Publications of The Korean Astronomical Society
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    • v.21 no.2
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    • pp.67-74
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    • 2006
  • We have developed a control electronics system for an infrared detector array of KASINICS (KASI Near Infrared Camera System), which is a new ground-based instrument of the Korea Astronomy and Space science Institute (KASI). Equipped with a $512{\times}512$ InSb array (ALADDIN III Quadrant, manufactured by Raytheon) sensitive from 1 to $5{\mu}m$, KASINICS will be used at J, H, Ks, and L-bands. The controller consists of DSP(Digital Signal Processor), Bias, Clock, and Video boards which are installed on a single VME-bus backplane. TMS320C6713DSP, FPGA(Field Programmable Gate Array), and 384-MB SDRAM(Synchronous Dynamic Random Access Memory) are included in the DSP board. DSP board manages entire electronics system, generates digital clock patterns and communicates with a PC using USB 2.0 interface. The clock patterns are downloaded from a PC and stored on the FPGA. UART is used for the communication with peripherals. Video board has 4 channel ADC which converts video signal into 16-bit digital numbers. Two video boards are installed on the controller for ALADDIN array. The Bias board provides 16 dc bias voltages and the Clock board has 15 clock channels. We have also coded a DSP firmware and a test version of control software in C-language. The controller is flexible enough to operate a wide range of IR array and CCD. Operational tests of the controller have been successfully finished using a test ROIC (Read-Out Integrated Circuit).

Omental Infarction Following Laparoscopy-assisted Gastrectomy (LAG) for Gastric Cancer (위암 환자의 복강경 위절제술 후 발생한 그물막 경색의 임상적 의의)

  • Kim, Min-Chan;Jung, Ghap-Joon;Oh, Jong-Young
    • Journal of Gastric Cancer
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    • v.10 no.1
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    • pp.13-18
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    • 2010
  • Purpose: Omental infarction (OI) following laparoscopy-assisted gastrectomy (LAG) for gastric cancer could become more common in the future because the indications for LAG are expected to expand. The aim of this study was to determine the clinical characteristics of OI following LAG. Materials and Methods: Three hundred ninety patients who underwent LAG for T1 or T2 gastric cancer from April 2003 to November 2007 were enrolled. OI was diagnosed by two radiologists using the patients' abdominal 16 row-detector CT scans. The clinicopathologic characteristics were retrospectively evaluated in the omental infarction (OI) group and the non-omental infarction (non-OI) group using the gastric cancer database of Dong-A University Medical Center and the medical record. Results: Nine omental infarctions (2.3%) of 390 LAGs were diagnosed. All the OIs could be discriminated from omental metastasis on the initial or follow up CT images. The location of the omental infarctions was on the epigastrium in 3 patients and in the left upper quadrant in 3 patients. The mean size of the OIs was 4.1 cm. Most patients with OI had no signs or symptoms. The body mass index of the OI group was higher than that of the non-OI group (P=0230), and OI was more common in patients who underwent total gastrectomy than in the patients who underwent subtotal gastrectomy (P=0.0011). Conclusion: Laparoscopy-assisted gastrectomy (LAG) with partial omentectomy for gastric cancer can be a cause of secondary OI. Omental infarction after LAG has different clinical characteristics and CT findings that those of other omental infarctions or postoperative omental metastases. Further multicenter study will be needed to evaluate in detail the clinical features of omental infarction after LAG.