• Transactions on Electrical and Electronic Materials
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• v.8 no.5
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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.

• Journal of Sensor Science and Technology
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• v.25 no.5
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• pp.349-353
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• 2016

Recently, research on bolometer-type uncooled infrared image sensor which is made for industrial applications has been increasing. In general, it is difficult to calibrate fixed pattern noise (FPN) of bolometer array. In this paper, average-current calibration algorithm is presented for reducing bolometer resistance offset. A resistor which is produced by standard CMOS process, on the average, has a deviation. We compensate for deviation of each resistor using average-current calibration algorithm. The proposed algorithm has been implemented by a chip which is consisted of a bolometer pixel array, average current generators, current-to-voltage converters (IVCs), a digital-to-analog converter (DAC), and analog-to-digital converters (ADCs). These bolometer-resistor array and readout circuit were designed and manufactured by $0.35{\mu}m$ standard CMOS process.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.2
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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.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.23-25
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• 2005

Infrared bolometer sensor's variation is detected by voltage drop between reference resistor and bolometer resistor in this architecture. One of the serious problems in this architecture is that these resistors value has a process variation. So common-mode level could be different from expectation in room temperature. Different common-mode level could lead to wrong output at the end of readout circuit. We suggest useful method to solve this problem. Difference correction using capacitor has reduced CM level difference to 86% for 1 $M\Omega$. bolometer and reference resistor's 10% variation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.2
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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.

• Journal of Sensor Science and Technology
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• v.27 no.5
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• pp.311-316
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• 2018

An antenna-coupled bolometer-type terahertz sensor was designed, fabricated, evaluated, and utilized to obtain terahertz transmission images. The sensor consists of a thin film bowtie antenna that resonates accordingly in response to an incident terahertz beam, a heater that converts the applied current in the antenna into heat, and a microbolometer that converts the rise in temperature into a change in resistance. The device is fabricated by a bulk micromachining process on a 4-inch silicon wafer. The fabricated sensor chip has a size of $2{\times}2mm$ and an active area of $0.1{\times}0.1mm^2$. The temperature coefficient of resistance (TCR) of the bolometer film (VOx) is 2.0%, which is acceptable for bolometer applications. The output sensor signal is proportional to the power of the incident terahertz beam. Transmission images were obtained with a 2-axis scanning imaging system that contained the sensor. The small active area of the sensor will enable the development of highly sensitive focal plane array sensors in terahertz imaging cameras in the future.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.148-149
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• 2008

As infrared light is radiated, the CMOS Readout IC (ROIC) for the microbolometer type infrared sensor detects voltage or current when the resistance value in the bolometer sensor varies. One of the serious problems in designing the ROIC is that resistances in the bolometer and reference resistor have process variation. This means that each pixel does not have the same resistance, causing serious fixed pattern noise problems in sensor operations. In this paper, Reference resistor compensation technique was proposed. This technique is to compensate the reference resistance considering the process variation, and it has the same reference resistance value as a bolometer cell resistance by using a comparator and a cross coupled latch.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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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.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.238-239
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• 2009

The amorphous silicon microbolometer array has been developed by the MEMS design and fabrication technology. Before the bolometer array for the image sensor being designed, the structure of unit cell and $16\times16$ array of it was simulated, designed and fabricated. The properties of bolometer have been measured as such that the TCR -3%/K.

• Journal of Sensor Science and Technology
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• v.27 no.6
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• pp.357-361
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• 2018

This paper presents an averaging current adjustment technique for reducing the pixel resistance variation in a bolometer-type uncooled infrared image sensor. Each unit pixel was composed of an active pixel, a reference pixel for the averaging current adjustment technique, and a calibration circuit. The reference pixel was integrated with a polysilicon resistor using a standard complementary metal-oxide-semiconductor (CMOS) process, and the active pixel was applied from outside of the chip. The averaging current adjustment technique was designed by using the reference pixel. The entire circuit was implemented on a chip that was composed of a reference pixel array for the averaging current adjustment technique, a calibration circuit, and readout circuits. The proposed reference pixel array for the averaging current adjustment technique, calibration circuit, and readout circuit were designed and fabricated by a $0.35-{\mu}m$ standard CMOS process.