• International Journal of Fuzzy Logic and Intelligent Systems
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• v.16 no.4
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• pp.246-253
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• 2016

Infrared (IR) imaging has been researched for various applications such as surveillance. IR radiation has the capability to detect thermal characteristics of objects under low-light conditions. However, automatic segmentation for finding the object of interest would be challenging since the IR detector often provides the low spatial and contrast resolution image without color and texture information. Another hindrance is that the image can be degraded by noise and clutters. This paper proposes multi-level segmentation for extracting regions of interest (ROIs) and objects of interest (OOIs) in the IR scene. Each level of the multi-level segmentation is composed of a k-means clustering algorithm, an expectation-maximization (EM) algorithm, and a decision process. The k-means clustering initializes the parameters of the Gaussian mixture model (GMM), and the EM algorithm estimates those parameters iteratively. During the multi-level segmentation, the area extracted at one level becomes the input to the next level segmentation. Thus, the segmentation is consecutively performed narrowing the area to be processed. The foreground objects are individually extracted from the final ROI windows. In the experiments, the effectiveness of the proposed method is demonstrated using several IR images, in which human subjects are captured at a long distance. The average probability of error is shown to be lower than that obtained from other conventional methods such as Gonzalez, Otsu, k-means, and EM methods.

• Proceedings of the Korea Information Processing Society Conference
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• 2015.10a
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• pp.578-579
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• 2015

Transmission and reflectance are two non-invasive techniques to perform pulse oximetry. This paper presents a design of reflectance-based pulse oximetry for watch-type wearable device, in which sensor and detector are located on the same surface of the body part. The basic principle of a pulse oximeter is based on the measurement of the red and infrared (IR) light absorption. Oxygenated blood has significant differences of light absorption characteristics than deoxygenated blood under red (660 nm) and infrared (940 nm) wavelength. Infrared is absorbed more by oxygenated hemoglobin than red. So the hardware implementation is included placing of the two LEDs (red and IR) with single photo-detector in the middle on the patient's wrist to get the corresponding pulsatile signals which are used to estimate the $SpO_2$.

• Current Optics and Photonics
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• v.2 no.3
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• pp.241-249
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• 2018

We report a midinfrared dual-field-of-view (FOV) optical system design for an airborne electro-optical targeting system. To achieve miniaturization and weight reduction of the system, it has a common aperture and fore-optics for three different spectral wavelength bands: an electro-optic (EO) band ($0.6{\sim}0.9{\mu}m$), a midinfrared (IR) band ($3.6{\sim}4.9{\mu}m$), and a designation laser wavelength ($1.064{\mu}m$). It is free to steer the line of sight by rotating the pitch and roll axes. Our design co-aligns the roll axis, and the line of sight therefore has a fixed entrance pupil position for all optical paths, unlike previously reported dual-FOV designs, which dispenses with image coregistration that is otherwise required. The fore-optics is essentially an achromatized, collimated beam reducer for all bands. Following the fore-optics, the bands are split into the dual-FOV IR path and the EO/laser path by a beam splitter. The subsequent dual-FOV IR path design consists of a zoom lens group and a relay lens group. The IR path with the fore-optics provides two stepwise FOVs ($1.50^{\circ}{\times}1.20^{\circ}$ to $5.40^{\circ}{\times}4.32^{\circ}$), due to the insertion of two Si lenses into the zoom lens group. The IR optical system is designed in such a way that the location and f-number (f/5.3) of the cold stop internally provided by the IR detector are maintained when changing the zoom. The design also satisfies several important performance requirements, including an on-axis modulation transfer function (MTF) that exceeds 10% at the Nyquist frequency of the IR detector pitch, with distortion of less than 2%.

• Journal of Sensor Science and Technology
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• v.21 no.6
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• pp.402-407
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• 2012

We report a Fabry-Perot interferometer (FPI)-based multi-channel micro-spectrometer used for multi-gas measurement in the spectral range of $3-5{\mu}m$ and its gas sensing performance. The fabricated infrared (IR) spectrometer consists of two parts: an FPI on the top side for selective IR filtering and a $V_2O_5$-based IR detector array on the bottom side for the detection of the filtered IR. Experimental results show that the FPI-based multi-channel gas sensor has reliability and selectivity for simultaneously detecting environmentally harmful gases such as $CH_4$, $CO_2$, $N_2O$ and CO in the spectral range of $3-5{\mu}m$. The fabricated FPI-based multi-channel gas sensor also demonstrated that a reliable and selective detection of gas concentrations ranging from 0 to 500 ppm is feasible. In addition, the electrical characteristics demonstrate a superior response performance in regards to the selectivity in the multi-target gases.

• Journal of Sensor Science and Technology
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• v.23 no.3
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• pp.165-169
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• 2014

An existing infrared (IR) analysis system is generally composed of infrared source, IR focusing lenses, IR detector, and optical chopper. An optical chopper is widely used in combination with lock-in amplifier to improve the signal-to-noise ratio by periodically interrupting incident light beam. During recent years, a few researches on miniaturized optical chopper have been reported to apply to micro-scaled optical systems. In this paper, a micro optical chopper operated by electromagnetic actuation is proposed and applied to a miniaturized micro-scaled optical system operating in IR spectral range. Additionally, the fabrication method of the proposed micro chopper is demonstrated. The proposed micro optical chopper is composed of the polydimethylsiloxane (PDMS) membrane, solenoid, and permanent magnet. The permanent magnet is bonded on the PDMS membrane using an ultraviolet-activated adhesive. The operation of the chopper is based on the attractive and repulsive forces between permanent magnet and solenoid induced by an electrical current flowing through the solenoid. The fabricated micro optical chopper could operate up to 200 Hz of frequency. The maximum operating distance of the chopper with 7mm diameter membrane was $750{\mu}m$ at 100 Hz of frequency.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.37 no.3
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• pp.63-71
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• 2000

Infrared (IR) detector chip, which detects the IR radiation from all of the objects and converts to image signal, is usually fabricated using hybrid bonding technology with detector away and readout integrated circuit (ROIC). In this study, we designed the readout circuit and simulated its operations. Fabricating readout circuit chips, we measured operation results satisfying its design requirements in 6V supply voltage. After we mount the IR detector chip in the manufactured thermal image system, thermal images were implemented. The obtained thermal images for high and room temperature target objects are sufficiently recognizable. Using the low noise thermal Image system, we expect to obtain thermal images with higher temperature resolution.

• Publications of The Korean Astronomical Society
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• v.32 no.1
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• pp.355-357
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• 2017

For future space IR missions, such as SPICA, it is crucial to establish an experimental method for evaluating the performance of mid-IR detectors. In particular, the wavelength dependence of the sensitivity is important but difficult to be measured properly. We are now preparing a testing system for mid-IR Si:As/Si:Sb detectors on SPICA. We have designed a cryogenic optical system in which IR signal light from a pinhole is collimated, passed through an optical filter, and focused onto a detector. With this system, we can measure the photoresponse of the detector for various IR light using optical filters with different wavelength properties. We have fabricated aluminum mirrors which are adopted to minimize thermal distortion effects and evaluated the surface figure errors. The total wavefront error of the optical system is $1.3{\mu}m$ RMS, which is small enough for the target wavelengths ($20-37{\mu}m$) of SPICA. The point spread function measured at a room temperature is consistent with that predicted by the simulation. We report the optical performance of the system at cryogenic temperatures.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.11
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• pp.7-13
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• 2002

BSCT 320${\times}$240 IRFPA detector module is implemented, which is a key component in uncooled thermal imaging systems. The detector module consists of two parts, infrared sensitive pixel array and read-out integrated circuit(ROIC). The BSCT 320${\times}$240 pixels are made by laser scribe process and 10-${\mu}m$ micro-bump to satisfy 50-${\mu}m$ pitch and 95-% fill-factor. The ROIC has been designed to electrically address the pixels sequentailly and to improve signal-to-noise ratio with single transistor amplifier, HPF, tunable LPF and clamp circuit. The fabricated hybrid chip of detector and ROIC has been mounted on the TEC built-in ceramic package for more stable operation and tested for lots of electrical and optical properties. The IRFA sample has shown successful properties and met with good results of fill-factor, detectivity and responsivity.

• Journal of Astronomy and Space Sciences
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• v.21 no.4
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• pp.467-480
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• 2004

It is very important to eliminate thermal background radiation for the near infrared camera system such as KAONICS (KAO Near Infrared Camera System). Thermal background radiations which come from window and cryostat wall influence IR detector and decrease IR system performance. Therefore the cold box which contains optics and detector housing must be cooled down to eliminate thermal background radiation. We carried out quantitative analysis to determine internal cooling temperature to reduce thermal noise in the J, H, Ks, and L bandpass. Additionally, we estimated the incoming heat load and then chose the cryocooler adequate to KAONICS's requirements. The cooling time and the final cooling temperature of the cold box were calculated. These results were also implemented to the system design.

• Progress in Superconductivity and Cryogenics
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• v.4 no.2
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• pp.68-72
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• 2002

This work investigates the transient cooling characteristics of an Infrared (IR) detector cryochamber, which has a critical effect on the cooling load. The current thermal modeling considers the conduction heat transfer through a cold well. the gaseous conduction due to outgassing. and the radiation heat transfer. The transient cooling Performance. i.e. the penetration depth and cooling load, is determined using a finite difference method. It is found that the penetration depth increases as the bore conductivity increases. Gaseous conduction and radiation hardly affect the penetration depth. The transient cooling load increases as the bore conductivity increases. The effects of gaseous conduction and radiation on transient heat transfer are weak at initial stages of cooling. However, their effects become significant as the cooling Process Proceeds.