• JSTS:Journal of Semiconductor Technology and Science
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• 제6권4호
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• pp.270-274
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• 2006

A color filter array (CFA) helps a single electrical image sensor to recognize color images. The Red-Green-Blue (RGB) Bayer CFA is commonly used, but the amount of the light which arrives at the photodiode is attenuated with this CFA. Red-White-Blue (RWB) CFA increases the amount of the light which arrives at photodiode by using White (W) pixels instead of Green (G) pixels. However, white pixels are saturated earlier than red and blue pixels. The pseudo multiple capture scheme and the corresponding RWB CFA were proposed to overcome the early saturation problem of W pixels. The prototype CMOS image sensor (CIS) was fabricated with $0.35-{\mu}m$ CMOS process. The proposed CIS solves the early saturation problem of W pixels and increases the dynamic range.

• JSTS:Journal of Semiconductor Technology and Science
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• 제17권1호
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• pp.35-41
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• 2017

We propose a novel multi-photodiode array (MPDA) based retinal implant IC with on/off stimulation strategy for a visual prosthesis with improved spatial resolution. An active pixel sensor combined with a comparator enables generation of biphasic current pulses when light intensity meets a threshold condition. The threshold is tuned by changing the discharging time of the active pixel sensor for various light intensity environments. A prototype of the 30-channel retinal implant IC was fabricated with a unit pixel area of $0.021mm^2$, and the stimulus level up to $354{\mu}A$ was measured with the threshold ranging from 400 lx to 13120 lx.

• JSTS:Journal of Semiconductor Technology and Science
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• 제5권2호
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• pp.102-106
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• 2005

A low dark current CMOS image sensor (CIS) pixel without any process modification is developed. Dark current is mainly generated at the interface region of shallow trench isolation (STI) structure. Proposed pixel reduces the dark current effectively by separating the STI region from the photodiode junction using simple layout modification. Test sensor array that has both proposed and conventional pixels is fabricated using 0.18 m CMOS process and the characteristics of the sensor are measured. The result shows that the dark current of the proposed pixel is 0.93fA/pixel that is two times lower than the conventional design.

• Current Optics and Photonics
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• 제7권5호
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• pp.485-495
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• 2023

The pixel size in high-resolution complementary metal-oxide-semiconductor (CMOS) image sensors continues to shrink due to chip size limitations. However, the pixel pitch's miniaturization causes deterioration of optical performance. As one solution, a quad color filter (CF) array with pixel binning has been developed to enhance sensitivity. For high sensitivity, the microlens structure also needs to be optimized as the CF arrays change. In this paper, the covered microlens, which consist of four microlenses covered by one large microlens, are proposed for the quad CF array in the backside illumination pixel structure. To evaluate the optical performance, the suggested microlens structure was simulated from 0.5 ㎛ to 1.0 ㎛ pixels at the center and edge of the sensors. Moreover, all pixel structures were compared with and without in-pixel deep trench isolation (DTI), which works to distribute incident light uniformly into each photodiode. The suggested structure was evaluated with an optical simulation using the finite-difference time-domain method for numerical analysis of the optical characteristics. Compared to the conventional microlens, the suggested microlens show 29.1% and 33.9% maximum enhancement of sensitivity at the center and edge of the sensor, respectively. Therefore, the covered microlens demonstrated the highly sensitive image sensor with a quad CF array.

• 대한전자공학회논문지TE
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• 제42권3호
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• pp.45-50
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• 2005

산업용, 의학용 및 군사용, 환경감시용 등 다양한 분야에서 UV 카메라가 이용되고 있다. 높은 분해능과 고효율을 가진 GaN 계열의 III-V족 질화물 반도체를 이용하여 제작한 UV 센서인 포토다이오드로 부터 최적의 자외선 응답을 읽어낼 수 있는 ROIC(ReadOut IC)를 개발 했다. FPA(Focal Plane Array)용 UV $8{\times}8$ ReadOut IC(ROIC)를 설계를 위하여 포토다이오드 타입 센서 소자를 커패시터로 모델링하였다. ROIC는 검출되는 신호를 받아 이를 증폭하고 잡음제거 필터링을 거쳐 픽셀 단위로 순차적으로 출력하는 기능을 수행하도록 하였다. ROIC는 $0.5{\mu}m$ 2Poly, 3Metal N-well CMOS process를 이용하여 제작되었으며, 이방성 전도성 페이스트 (Anisotropic Conductive Paste:ACP)를 사용하는 gold stud bumping 공정으로 ROIC와 포토다이오드 어레이를 하이브리드 패키지 (package)한 후 PC에서 자외선 영상으로 확인함으로써 ROIC의 동작을 검증하였다.

• 센서학회지
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• 제26권4호
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• pp.223-227
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• 2017

Conventional CMOS image sensors (CISs) have a trade-off relationship between dynamic range and sensitivity. In addition, their sensitivity is determined by the photodiode capacitance. In this paper, CISs that consist of dual-sensitivity photodiodes in a unit pixel are proposed for achieving wide dynamic ranges. In the proposed CIS, signal charges are generated in the dual photodiodes during integration, and these generated signal charges are accumulated in the floating-diffusion node. The signal charges generated in the high-sensitivity photodiodes are transferred to the input of the comparator through an additional source follower, and the signal voltages converted by the source follower are compared with a reference voltage in the comparator. The output voltage of the comparator determines which photodiode is selected. Therefore, the proposed CIS composed of dual-sensitivity photodiodes extends the dynamic range according to the intensity of light. A $94{\times}150$ pixel array image sensor was designed using a conventional $0.18{\mu}m$ CMOS process and its performance was simulated.

• 대한전자공학회논문지SD
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• 제44권2호
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• pp.55-60
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• 2007

본 논문에서는 1차원 CMOS 포토다이오드 픽셀 어레이를 이용한 광학 각도 센서에서, 해상도를 2배 향상시키는 인터폴레이션 방법을 제안한다. 제안된 구조는 인터폴레이션을 위하여 모든 픽셀을 짝수 픽셀 그룹과 홀수 픽셀 그룹으로 나누어, 각 그룹에서 가장 밝은 빛이 들어오는 픽셀(winner)을 winner take all 회로를 이용하여 찾아 이로부터 인터폴레이션을 수행하여 각도 센서의 해상도를 2배 향상시킨다. 제안된 인터폴레이션 방법은 픽셀이나 WTA 회로의 추가없이 간단히 하나의 XOR 게이트와 전압 비교기 회로를 이용하여 구현할 수 있다. $5.6{\mu}m$의 픽셀 피치를 가진 336개의 포토다이오드 픽셀 어레이를 $0.35{\mu}m$ CMOS 공정으로 구현한 후, 그 위에 $50{\mu}m$ 폭의 슬릿을 붙여서 광학 센서를 구성하여 실험하였다. 측정된 각도 해상도는 $0.1{\circ}$이며 35mW의 전력을 소모하고 최대 초당 8000번 각도를 측정할 수 있다.

• 한국전기전자재료학회논문지
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• 제25권11호
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• pp.857-861
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• 2012

FPN (fixed-pattern-noise) mainly comes from the device or pattern mismatches in pixel and color filter, pixel photodiode leakage in CMOS image sensor. In this paper, optical stack module related pixel FPN was investigated and the classification of pixel FPN contribution with the individual optical module process was presented. The methodology and procedure would be helpful in reducing the greater pixel FPN and distinguishing the complex FPN sources with respect to various noise factors.

• 방사선산업학회지
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• 제9권1호
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• pp.1-7
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• 2015

The trend of x-ray image sensor has been evolved from an amorphous silicon sensor to a crystal silicon sensor. A crystal silicon X-ray sensor, meaning a X-ray CIS (CMOS image sensor), is consisted of three transistors (Trs), i.e., a Reset Transistor, a Source Follower and a Select Transistor, and a photodiode. They are highly sensitive to radiation exposure. As the frequency of exposure to radiation increases, the quality of the imaging device dramatically decreases. The most well known effects of a X-ray CIS due to the radiation damage are increments in the reset voltage and dark currents. In this study, a pixel array of a X-ray CIS was made of $20{\times}20pixels$ and this pixel array was exposed to a high radiation dose. The radiation source was Co-60 and the total radiation dose was increased from 1 to 9 kGy with a step of 1 kGy. We irradiated the small pixel array to get the increments data of the reset voltage and the dark currents. Also, we simulated the radiation effects of the pixel by MCNP (Monte Carlo N-Particle) simulation. From the comparison of actual data and simulation data, the most affected location could be determined and the cause of the increments of the reset voltage and dark current could be found.

• 센서학회지
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• 제5권3호
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• pp.65-73
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• 1996

수액을 장시간 환자에게 주입할 때 적절한 주입량, 주입률을 조절하는 것이 중요하다. 부적절한 주입량은 환자의 회복에 좋지 않은 영향을 끼칠 수 있으므로 주입량을 감지하는 센서의 신뢰도는 인퓨전 펌프 시스템에 많은 영향을 미친다. 본 연구에서는 인퓨전 펌프 시스템에 사용될 3가지 센서의 성능을 검토하였다. 피에조 필름, 광트렌지스터 및 광 다이오드 어레이의 3가지 센서가 비교되었으며 제안하는 신호 처리 기법과 광 다이오드 어레이를 사용한 기법을 이용하여 간섭과 진동 조도변화 센서의 위치에 따른 감도 변화등의 영향을 줄일 수 있었다. 실험 결과 광 다이오드 어레이가 다른 센서들에 비하여 높은 신지도를 보여 주었다.