• Nuclear Engineering and Technology
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• 제54권5호
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• pp.1760-1768
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• 2022

When gamma-camera sensor modules, which are key components of radiation imagers, are derived from the coupling between scintillators and photosensors, the light collection efficiency is an important factor in determining the effectiveness with which the instrument can identify nuclides via their derived gamma-ray spectra. If the pixel area of the scintillator is larger than the pixel area of the photosensor, light loss and cross-talk between pixels of the photosensor can result in information loss, thereby degrading the precision of the energy estimate and the accuracy of the position-of-interaction determination derived from each active pixel in a coded-aperture based gamma camera. Here we present two methods to overcome the information loss associated with the loss of photons created by scintillation pixels that are coupled to an associated silicon photomultiplier pixel. Specifically, we detail the use of either: (1) light guides, or (2) scintillation pixel areas that match the area of the SiPM pixel. Compared with scintillator/SiPM couplings that have slightly mismatched intercept areas, the experimental results show that both methods substantially improve both the energy and spatial resolution by increasing light collection efficiency, but in terms of the image sensitivity and image quality, only slight improvements are accrued.

• 한국광학회:학술대회논문집
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• 한국광학회 2003년도 하계학술발표회
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• pp.98-99
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• 2003

PIN photodiode has been used in solid-state detector for x-ray detection as a photosensor of visible light from scintillator. Since the light from CWO is short wavelength having peak at 490nm, the light is absorbed within a very shallow layer near the surface of the photodiode before arriving at the depletion layer and does not contribute to the signal. In designing the PIN photodiode, it is important to make the p-layer as shallow as possible. (omitted)

• 한국군사과학기술학회지
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• 제15권2호
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• pp.201-207
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• 2012

Pulsed lasers at the 613 nm and 1064 nm wavelengths on nanoseconds have been utilized to characterize the damage on Si photodiode exposed to intense illumination. Morphological damages and structural changes at sites on the photodiode irradiated during microseconds of laser pulses were analyzed by FE-SEM images and XRD patterns, respectively. The removal of oxide coating, ripple, melting marks, ridges, and crater on photodiodes were definitely observed in order of increasing the pulse intensities generated above the damage threshold. Then, the degradation in photosensitivity of the Si photodiode irradiated by high power density pulses was measured as a function of laser irradiation time at the various wavelengths. The free charge carrier and thermal diffusion mechanisms could have been invoked to characterize the damage. The relative photosensitivity data calculated using the thermal diffusion model proposed in this paper have been compared with the experimental data irradiated above the damage threshold.

• 대한의용생체공학회:의공학회지
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• 제25권4호
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• pp.253-259
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• 2004

본 연구에서는 디지털 X-선 영상시스템의 최적화 설계를 위하여 몬테카를로 방법을 이용한 영상모의실험용 코드를 visual $C^{++}$ 프로그래밍 언어를 사용하여 개발하였다. 디지털 X-선 영상시스템으로 Gd$_2$O$_2$S(Tb) 섬광체 및 광센서 어레이를 고려하였으며, 일반적인 실험 환경을 모사하기 위해 2차원 평행 그리드를 포함시켰다. X-선과 피사체, 그리드 및 섬광체와의 반응, 그리고 섬광체에서 발생된 빛의 거동 및 광센서 어레이에서의 수집을 몬테카를로 방법을 이용하여 모사하였다. Gd$_2$O$_2$S(Tb) 섬광체의 두께는 66$\mu\textrm{m}$로 설정하였으며, 광센서 어레이의 픽셀 피치는 48$\mu\textrm{m}$ 그리고 픽셀의 포맷은 256${\times}$256으로 가정하였다. 다양한 모의실험조건에서 X-선 영상을 획득한 후 객관적인 영상시스템의 성능평가 지표인 SNR(signal-to-noise ratio), MTF(modulation transfer function), NPS(noise power spectrum), DQE(detective quantum efficiency) 등을 계산하였으며, 이를 통해 화질을 평가하였다. 본 연구에서 개발된 영상모의실험 코드는 다양한 디지털 X-선 영상시스템에 대해 여러 설계변수들에 대한 성능을 예측함으로써 영상시스템 최적설계에 활용될 수 있다.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2009년도 추계학술대회 논문집
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• pp.169-172
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• 2009

Daylight responsive dimming system, which is one of the method for utilizing available daylight. continuously adjusts lighting output with an algorithm of the correlation of photosensor signal and workplane illuminance levels. This system must be related with shading systems which are to control penetrating daylight. The purpose of this research is to analyze illuminance distributions by artificial lighting in different shading systems. Lighting power is changed by 5 levels in nighttime for comparing correlation between illuminance and lighting power in different shading systems.

• Journal of information and communication convergence engineering
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• 제10권1호
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• pp.91-95
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• 2012

The photoplethysmography (PPG) signal measured from a mobile healthcare device contains various motion artifacts occurring from a patient’s movements. Recently, to reject the motion artifacts, the method of using an acceleration sensor was suggested, but such sensors are very expensive. Therefore, this study deals with a novel sensor device to replace the acceleration sensor, and evaluated the performance of the proposed sensor experimentally. In the results of the experiments, it is shown that the proposed sensor device can reconstruct the PPG signal despite the occurrence of motion artifacts, and also that the variation rate in heart rate analysis was 1.22%. According to the experimental results, the proposed method can be applied to design a low-cost device.

• 한국전기전자재료학회논문지
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• 제16권12호
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• pp.1097-1102
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• 2003

In this paper, we used only PR as etching mask, while it used usually Cr/AU as etching mask, and in order to fabricate a photosensor has the increased sensitivity, we investigated on the sensitivity of general type and p-i-n type diode. we designed microchannel size width max 10um, min 5um depth max 10um, reservoir size max 100um, min 2mm. Fabrication of microfluidic devices in glass substrate by glass wet etching methods and glass to glass fusion bonding. The p-i-n diode has higher sensitivity than photodiode, Considering these results, we fabricated p-i-n diodes on the high resistive(4㏀$.$cm) wafer into rectangle and finger pattern and compared internal resistance of each pattern. The internal resistance of pin diode can be decreased by the application of finger pattern has parallel resistance structure from 571Ω to 393Ω.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2006년도 제33회 추계학술대회 발표논문집
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• pp.48-48
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• 2006

• JSTS:Journal of Semiconductor Technology and Science
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• 제13권5호
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• pp.500-510
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• 2013

In this paper, a high-sensitivity low power photodetector using double gate (DG) MOSFET is proposed for the first time using change in subthreshold current under illumination as the sensitivity parameter. An analytical model for optically controlled double gate (DG) MOSFET under illumination is developed to demonstrate that it can be used as high sensitivity photodetector and simulation results are used to validate the analytical results. Sensitivity of the device is compared with conventional bulk MOSFET and results show that DG MOSFET has higher sensitivity over bulk MOSFET due to much lower dark current obtained in DG MOSFET because of its effective gate control. Impact of the silicon film thickness and gate stack engineering is also studied on sensitivity.

• 한국식물학회:학술대회논문집
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• 한국식물학회 1998년도 The 12th Symposium on Plant Biotechnology Vol.12
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• pp.83-96
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• 1998

The plant pigment proteins phytochromes are a molecular light sensor or switch for photomorphogenesis involving a variety of growth and developmental responses of plants to red and far-red wavelength light. Underscoring the photomorphogenesis mediated by phytochromes is the light signal transduction at molecular and cellular levels. For example, a number of genes activated by the phytochrome-mediated signal transduction cascade have been identified and characterized, especially in Arabidopsis thaliana. The light sensor/switch function of phytochromes are based on photochromism of the covalently linked tetrapyrrole chromophore between the two photoreversible forms, Pr and Pfr. The photochromism of phytochromes involves photoisomerization of the tetrapyrrole chromophore. The "photosensor" Pr-form ("switch off" conformation) of phytochromes strongly absorbs 660 nm red light, whereas the "switch on" Pfr-conformation preferentially absorbs 730 nm far-red light. The latter is generally considered to be responsible for eliciting transduction cascades of the red light signal for various responses of plants to red light including positive or negative expression of light-responsive genes in plant nuclei and chloroplasts. In this paper, we discuss the structure-function of phytochromes in plant growth and development, with a few examples of biotechnological implications.