• Transactions on Electrical and Electronic Materials
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• 제8권5호
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• pp.196-200
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• 2007

In this paper, we propose and discuss the design using a simple method that reduces the fixed pattern noise(FPN) generated on the amorphous Si($\alpha-Si$) bolometer. This method is applicable to an IR image sensor. This method can also minimize the size of the reference resistor in the readout integrated circuit(ROIC) which processes the signal of an IR image sensor. By connecting four bolometer cells in parallel and averaging the resistances of the bolometer cells, the fixed pattern noise generated in the bolometer cell due to process variations is remarkably reduced. Moreover an $\alpha-Si$ bolometer cell, which is made by a MEMS process, has a large resistance value to guarantee an accurate resistance value. This makes the reference resistor be large. In the proposed cell structure, because the bolometer cells connected in parallel have a quarter of the original bolometer's resistance, a reference resistor, which is made by poly-Si in a CMOS process chip, is implemented to be the size of a quarter. We designed a ROIC with the proposed cell structure and implemented the circuit using a 0.35 um CMOS process.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.7-8
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• 2009

In the presence of infrared light, a CMOS Readout IC (ROIC) for a microbolometer typed infrared sensor detects the voltage or current that is caused by the changing in resistance in the bolometer sensor. A serious problem in designing the ROIC is how the value of the bolometer and reference resistors vary because of variations in manufacturing process. Since different pixel have different, resistance values, sensor operations must contend with fixed pattern noise (FPN) problems. In this paper, we propose a novel technique to compensate for the fluctuation in reference resistance by tiling into account the process variation. By using constant current source basing and correlated double sampling, we solved FPN.

• 한국전기전자재료학회논문지
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• 제22권2호
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• pp.119-122
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• 2009

As infrared light radiates, the CMOS Readout IC (ROIC) for the microbolometer typed infrared sensor detects voltage or current which is caused by the variation of resistance in the bolometer sensor. A serious problem we may have in designing the ROIC is the value of bolometer and reference resistors will be changed due to process variation. Since each pixel does not have the same value of resistance, fixed pattern noise problems happen during the sensor operations. In this paper, we propose a novel technique to compensate the fluctuation of reference resistance with taking account of process variation. By using a comparator and a cross coupled latch, we will make the value of reference resistor same as the bolometer's.

• 전자공학회논문지B
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• 제30B권2호
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• pp.69-77
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• 1993

Automatic image recognition system is essential for a better man-to machine interaction. Because of the noise and deformation due to the sensor operation, it is not simple to build an image recognition system even for the fixed images. In this paper neural network which has been reported to be adequate for pattern recognition task is applied to the fixed and variational(rotation, size, position variation for the fixed image)recognition with a hope that the problems of conventional pattern recognition techniques are overcome. At fixed image recognition system. ART model is trained with face images obtained by camera. When recognizing an matching score. In the test when wigilance level 0.6 - 0.8 the system has achievel 100% correct face recognition rate. In the variational image recognition system, 65 invariant moment features sets are taken from thirteen persons. 39 data are taken to train multi-layer perceptron and other 26 data used for testing. The result shows 92.5% recognition rate.

• 한국전기전자재료학회논문지
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• 제23권2호
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• pp.89-92
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• 2010

A bolometer sensor used in an infrared thermal imaging system has many advantages on the process because it does not need a separate cooling system and its manufacturing is easy. However the sensitivity of the bolometer is low and the fixed pattern noise(FPN) is large, because the bolometer sensor is made by micro electro mechanical systems (MEMS). These problems can be fixed-by using the high performance readout integrated circuit(ROIC) with noise reduction techniques. In this paper, we propose differential delta sampling circuit to remove the mismatch noise of ROIC itself, the FPN of the bolometer. And for reduction of FPN noise, the reference signal compensation circuit which compensate the reference signal by using on-resistance of MOS transistor was proposed.

• The Journal of the Acoustical Society of Korea
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• 제24권2E호
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• pp.38-45
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• 2005

The noise reduction of the In-The-Ear (ITE) hearing aid (HA) can be achieved by arrays of microphones. Each of the right and the left ears was assumed to have two HA microphones. These arrays of HA microphones produce particular patterns of directivity by some time delay between two microphones. The directivity pattern geometrically increase the S/N ratio. The boundary element method (BEM) was used for the three dimensional simulation of the HA directivity pattern with the two pairs' microphone arrays. The separation between two microphones was fixed to 10 mm. The time delay between the two microphones was calculated to produce the most narrow directivity pattern in the fore front of the head. The variation of the time delay was examined in accordance with input frequencies. This numerical analysis may be then applied for the calculation of the time delay parameter of the digital hearing aid DSP chip.

• 한국정보전자통신기술학회논문지
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• 제16권6호
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• pp.465-471
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• 2023

본 논문은 CMOS Image Sensor(CIS)에 사용되는 single-slope ADC(SS-ADC)의 노이즈와 출력의 지연을 개선한 비교기 구조를 제안한다. 노이즈와 출력의 지연 특성을 개선하기 위해 비교기의 첫 번째 단의 출력 노드와 두 번째 단의 출력 노드 사이에 커패시터를 삽입하여 miller effect를 이용한 비교기 구조를 설계하였다. 제안하는 비교기 구조는 작은 capacitor를 이용하여 노이즈와 출력의 지연 및 layout 면적을 개선하였다. Single slop ADC에서 사용되는 CDS 카운터는 T-filp flop과 bitwise inversion 회로를 사용하여 설계하였고 전력 소모와 속도가 개선되었다. 또한 single slop ADC는 analog correlated double sampling(CDS)와 digital CDS를 함께 동작하는 dual CDS를 수행한다. Dual CDS를 수행함으로써 fixed pattern noise(FPN), reset noise, ADC error를 줄여 이미지 품질이 향상된다. 제안하는 comparator 구조가 사용된 single-slope ADC는 0.18㎛ CMOS 공정으로 설계되었다.

• 전자공학회논문지
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• 제53권12호
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• pp.120-127
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• 2016

디지털 x선 영상을 획득하기 위하여 최근에는 DR(digital radiography) 기술에 근거한 방사선 디텍터의 개발이 활발하게 진행되고 있다. 이러한 방사성 디텍터의 잡음 특성은, 균일한 노출에서 획득한 영상을 사용하여 NNPS(normalized noise power spectrum)를 측정하여 관찰한다. 이때 고정형태잡음(fixed pattern noise)을 제거하기위하여 두 장의 영상 차를 사용한다. 본 논문에서는 보다 정확한 NNPS를 측정하기 위하여, 먼저 여러 장의 영상을 획득하여 두 장의 평균영상을 구하고 그의 차를 사용하여 NNPS를 구하는 방법을 제안하였다. 이때 여러 장의 영상들의 평균으로 인하여 NNPS 값이 실제 값보다 작아지는데, 이러한 NNPS의 보정을 위하여, 평균할 때 사용한 영상 개수의 함수인 보정 상수도 함께 제안하였다. 또한 평균영상의 비를 사용하여 NNPS를 구하는 방법도 제안하였다. 실제 방사선 디텍터에서 획득한 영상을 사용하여 NNPS를 측정하는 실험을 통하여, 제안한 방법으로 NNPS 보다 정확하게 구할 수 있음을 관찰하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계 학술대회논문집(수송기계편)
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• pp.105-108
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• 2005

The radiated noise from the automotive intake system should be predicted at the design stage. To this end, the precise measurement of in-duct acoustic source parameters of the intake system, i.e., the source strength and source impedance, is essential. Most of previous works on the measurement of acoustic source parameters were performed under a fixed engine speed condition. However, the requirement of vehicle manufacturer is the noise radiation pattern as a function of engine speed. In this study, the direct method was employed to measure the source parameters of engine intake system under a fixed engine speed and engine run-up condition. It was noted that the frequency spectra of source impedance hardly changes with varying the engine speed. Thus, it is reasonable to calculate the source strength under the engine run-up condition by assuming that source impedance is invariant with engine speed. Measured and conventional source models, i.e., constant pressure source, constant velocity source, and non-reflective source, were utilized to predict insertion loss and radiated sound pressure level. A reasonable prediction accuracy of radiated sound pressure level spectra from the intake system was given in the test vehicle when using the measured source characteristics which were acquired under the operating condition.

• 전자공학회논문지
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• 제53권4호
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• pp.97-105
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• 2016

방사선 영상 디텍터는 x선 광자로부터 생성된 전하를 수집하여 다수의 전하증폭기 회로를 사용하여 전압 신호로 바꾼 뒤 이를 디지털 신호로 바꾸어 디지털 영상을 생성한다. 이때 다수로 사용한 회로의 불균일한 특성으로 인하여 이득의 불균일이라는 고정형태잡음이 발생한다. 이를 제거하기 위하여 이득지도를 사용하는 이득 보정 알고리듬이 일반적으로 사용되는데, 이득지도 설계 시에 광자 잡음이 이득지도에 남게 되고 이 잡음은 이득 보정된 영상을 오염시킨다. 본 논문에서는 이러한 남아있는 잡음을 필터를 사용하여 제거하는 실험을 하였으며, 효율적으로 잡음을 제거하기위한 필터를 최적화하는 알고리듬을 제안하였다. 실제 디텍터로 획득한 영상에 대하여 실험을 수행하여, 단순한 필터로 제거하기 힘든, 고정형태잡음의 크기가 상대적으로 큰 경우에도, 필터 최적화 알고리듬을 사용하여 효율적으로 잡음 제거에 대한 성능을 개선시킬 수 있음을 보였다.