• 센서학회지
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• 제17권1호
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• pp.35-40
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• 2008

Low power bridge type micro gas sensors were fabricated by micro machining technology with TMAH (Tetra Methyl Ammonium Hydroxide) solution. The sensing devices with different heater materials such as metal and poly-silicon were obtained using CMOS (Complementary Metal Oxide Semiconductor) compatible process. The tellurium films as a sensing layer were deposited on the micro machined substrate using shadow silicon mask. The low power micro gas sensors showed high sensitivity to NO with high speed. The pure tellurium film used micro gas sensor showed good sensitivity than transition metal (Pt, Ti) used tellurium film.

• Journal of the Optical Society of Korea
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• 제19권6호
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• pp.658-664
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• 2015

Lens designers generally refer to flat image fields and attempt to minimize the field curvature. Present-day CMOS image sensors for mobile phone cameras, however, are not flat, but curved. Sometimes it is necessary to generate an intentional field curvature according to the degree and direction of the CMOS image-sensor’s curvature. This paper presents the degree of curvature of a CMOS image sensor measured using an interferometer, and proposes an effective compensation method that minimizes the net field curvature through optimizing the air gap between lens elements, which is demonstrated using simulations and experiments.

• Current Optics and Photonics
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• 제7권2호
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• pp.200-206
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• 2023

Near-infrared (NIR) sensing technology using CMOS image sensors is used in many applications, including automobiles, biological inspection, surveillance, and mobile devices. An intuitive way to improve NIR sensitivity is to thicken the light absorption layer (silicon). However, thickened silicon lacks NIR sensitivity and has other disadvantages, such as diminished optical performance (e.g. crosstalk) and difficulty in processing. In this paper, a pixel structure for NIR sensing using a stacked CMOS image sensor is introduced. There are two photodetection layers, a conventional layer and a bottom photodiode, in the stacked CMOS image sensor. The bottom photodiode is used as the NIR absorption layer. Therefore, the suggested pixel structure does not change the thickness of the conventional photodiode. To verify the suggested pixel structure, sensitivity was simulated using an optical simulator. As a result, the sensitivity was improved by a maximum of 130% and 160% at wavelengths of 850 nm and 940 nm, respectively, with a pixel size of 1.2 ㎛. Therefore, the proposed pixel structure is useful for NIR sensing without thickening the silicon.

• 전기전자학회논문지
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• 제1권1호
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• pp.1-10
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• 1997

It is well-known that rectangular bulk-Si sensors prepared by etch or epi etch-stop micromachining technology are already in practical use today, but the conventional bulk-Si sensor shows some drawbacks such as large chip size and limited applications as silicon sensor device is to be miniaturized. We consider a circular-shape SOI(Silicon-On-Insulator) micro-cavity technology to facilitate multiple sensors on very small chip, to make device easier to package than conventional sensor like pressure sensor and to provide very high over-pressure capability. This paper demonstrates the cross-functional results for stress analyses(targeting $5{\mu}m$ deflection and 100MPa stress as maximum at various applicable pressure ranges), for finding permissible diaphragm dimension by output sensitivity, and piezoresistive sensor theory from two-type SOI structures where the double SOI structure shows the most feasible deflection and small stress at various ambient pressures. Those results can be compared with the ones of circular-shape bulk-Si based sensor$^{[17]}. The SOI micro-cavity formed the sensors is promising to integrate with calibration, gain stage and controller unit plus high current/high voltage CMOS drivers onto monolithic chip.

• 한국항공우주학회지
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• 제35권11호
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• pp.1043-1051
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• 2007

디지털 태양센서는 CMOS 이미지 센서에 맺힌 태양광 이미지를 이용하여 태양광의 입사 각도를 계산한다. 이를 위해서는 태양광 이미지의 정확한 중심점을 찾아야하며 따라서 정밀한 중심점 추정은 디지털 태양센서 개발에서 가장 중요한 요소가 된다. 중심점을 찾기 위해서 가장 일반적으로 쓰이는 중심 알고리즘은 thresholding 방법이며 가장 단순하고 구현하기 쉽다. 또 다른 알고리즘으로는 이미지 처리를 이용하는 image filtering 방법이 있다. 하지만 이러한 방법들은 태양센서 정밀도가 이미지 센서에서 획득한 태양광 강도(intensity) 데이터의 노이즈에 영향을 많이 받으며, 특히 thresholding 방법의 경우 threshold 값에 따라 정밀도가 바뀌기 때문에 효과적인 threshold 값을 정하기 어려운 단점이 있다. 따라서 본 논문에서는 태양광 이미지의 중심점을 구하기 위해서 태양광 이미지 모델을 이용하는 template 방법을 제시하고 성능을 비교 분석하였다. 제안한 template 방법은 thereshold, image filtering 방법과 달리 비교적 높은 정밀도를 가지며, 특히 노이즈 수준에 관계없이 거의 일정한 수준의 정밀도를 가지는 장점이 있어 신뢰성이 높다.

• 센서학회지
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• 제20권1호
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• pp.14-18
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• 2011

An analytical pinning-voltage model of a pinned photodiode has been proposed and derived. The pinning-voltage is calculated using doping profiles based on shallow- and exponential-junction approximations. Therefore, the derived pinning-voltage model is analytically expressed in terms of the process parameters of the implantation. Good agreement between the proposed model and simulated results has been obtained. Consequently, the proposed model can be used to predict the pinning-voltage and related performance of a pinned photodiode in a CMOS active pixel sensor.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 하계종합학술대회 논문집(1)
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• pp.439-442
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• 2002

We present in this Paper a microwave Power sensor fabricated by a standard CMOS process and a bulk micromachining process. The sensor consists of a CPW transmission line, a resistor as a healer, and thermocouple arrays. An input microwave heater, the resistor so that the temperature rises proportionally to the microwave power and tile thermocouple arrays convert it to an electrical signal. The sensor uses air bridged 8round of CPW realized by wire bonding to reduce tile device size and cost and to improve the thermal impedance. Al/poly-Si junctions are used for the thermocouples. Poly-Si is used for tile resister and Aluminium is for transmission line. The resistor and hot junctions of the thermocouples are placed on a low stress silicon nitride diaphragm to minimize a thermal loss. The fabricated device operates properly from 1㎼ to 100㎽\ulcorner of input power. The sensitivity was measured to be ,3.2～4.7 V/W.

• 대한원격탐사학회지
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• 제31권2호
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• pp.85-99
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• 2015

저궤도 지구관측위성에 탑재되는 전자광학 카메라는 높은 SNR 및 MTF 성능 요구조건을 만족시키기 위하여, TDI 기능이 포함된 CCD 센서를 사용하는 것이 일반적이다. 그러나, CMOS 센서가 가진 다양한 장점을 활용하기 위하여 CMOS 센서에도 TDI 기능이 추가되고 있으며, CMOS 센서의 취약점 중의 하나인 motion blur 문제를 개선하기 위한 다양한 방법들이 제시되고 있다. CMOS 센서에서도 CCD 센서의 multiphased clocking 방법과 유사하게, 하나의 픽셀을 다수의 서브픽셀로 나누어 각각을 별도로 읽어내거나, 픽셀 사이에 인위적인 마스크을 삽입하기도 한다. 또한, 노출시간(integration time)을 라인타임보다 짧게 하여, TDI CMOS 카메라 시스템의 motion blur를 최소화 할 수도 있다. 노출시간을 조절하는 방법을 적용함으로써, 카메라 제어 유닛의 명령을 통하여, 각각의 촬영임무의 목적에 맞도록, SNR 우선 영상 또는 MTF 우선 영상을 선택적으로 획득하는 것이 가능하다. 본 논문에서는 노출시간을 조절하여 motion blur를 최소화 하는 방법에 대해 분석한 결과를 기술하고, MATLAB 시뮬레이션을 통하여 확인된 영상품질(dynamic MTF)의 개선 정도를 정리하였다.

• 센서학회지
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• 제14권6호
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• pp.387-394
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• 2005

In order to design SOI CMOS image sensors, SOI MOSFET model parameters were extracted using the equation of bulk MOSFET model parameters and were optimized using SPICE level 2. Simulated I-V characteristics of the SOI NMOSFET using the extracted model parameters were compared to the experimental I-V characteristics of the fabricated SOI NMOSFET. The simulation results agreed well with experimental results. A unit pixel for SOI CMOS image sensors was designed and was simulated for the PPS, APS, and logarithmic circuit using the extracted model parameters. In these CMOS image sensors, a nano-wire MOSFET photodetector was used. The output voltage levels of the PPS and APS are well-defined as the photocurrent varied. It is confirmed that SOI CMOS image sensors are faster than bulk CMOS image sensors.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1787-1790
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• 2005

We have developed satellite devices for fine attitude control of the Science & Technology Satellite-2 (STSAT-2) scheduled to be launched in 2007. The analog sun sensors which have been continuously developed since the 1990s are not adequate for satellites which require fine attitude control system. From the mission requirements of STSAT-2, a compact, fast and fine digital sensor was proposed. The test of the fine attitude determination for the pitch and roll axis, though the main mission of STSAT-2, will be performed by the newly developed FDSS. The FDSS use a CMOS image sensor and has an accuracy of less than 0.01degrees, an update rate of 20Hz and a weight of less than 800g. A pinhole-type aperture is substituted for the optical lens to minimize the weight while maintaining sensor accuracy by a rigorous centroid algorithm. The target process speed is obtained by utilizing the Field Programmable Gate Array (FPGA) in acquiring images from the CMOS sensor, and storing and processing the data. This paper also describes the analysis of the optical performance for the proper aperture selection and the most effective centroid algorithm.