• Journal of the Korean Magnetics Society
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• v.18 no.2
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• pp.71-74
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• 2008

In this paper, we have measured the effect of the optical spot size, incident upon the quadrant photodetector, on the optical displacement sensitivity of the optical beam deflection technique. We have built an optical displacement detection system based on the optical beam deflection method using 3 mW He-Ne laser and measured the displacement sensitivity with changing the optical spot size on the quadrant photodetector. We have also calculated the changes in the optical displacement sensitivity as a function of the incident laser spot size by modeling a circular optical spot with constant laser intensity. Our experimental and theoretical studies show that the optical displacement sensitivity increases with the decrease in the optical spot size. This suggests that in the design of the optical motion detection systems with sub-nanometer sensitivity, the displacement sensitivity can be optimized by reducing the size of the incident optical spot on the detector.

• Current Optics and Photonics
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• v.7 no.2
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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.

• Journal of Sensor Science and Technology
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• v.30 no.3
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• pp.131-138
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• 2021

The optimization of the specifications of vertical silicon on insulator (SOI) slot optical waveguides suitable for integrated-optical biochemical sensors was performed through computational analysis of the confinement factor of the guided mode distributed in the slot in addition to analytical examination of the TE mode. The optimized specifications were confirmed based on sensitivity in terms of the change in the refractive index of the biochemical analyte. When the slot width, rail width, and height were set to 120 nm, 200 nm, and 320 nm, respectively, the confinement factor was evaluated to be about 56% and the sensitivity was at least 0.9 [RIU/nm].

• Journal of the Optical Society of Korea
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• v.15 no.4
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• pp.329-334
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• 2011

We proposed a poly-dimethylsiloxane (PDMS)-coated fiber Bragg grating (FBG) temperature sensor for enhancing temperature sensitivity. By embedding the bare FBG in a temperature-sensitive elastomeric polymer, the temperature sensitivity of the proposed structure could be effectively improved by 4.2 times higher than those of the conventional bare-type FBG sensors due to the high thermal expansion coefficient of the PDMS. We analyzed the temperature-sensitivity enhancement effect with the increased Bragg wavelength shift in our structure and dependence on the temperature sensitivity with respect to the cross-section area of the PDMS.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.15
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• pp.6177-6186
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• 2015

Sensitivity and specificity are the two most important indicators in selection of medical imaging devices for cancer screening. Breast images taken by conventional or digital mammography, ultrasound, MRI and optical mammography were collected from 2,143,852 patients. They were then studied and compared for sensitivity and specificity results. Optical mammography had the highest sensitivity (p<0.001 and p<0.006) except with MRI. Digital mammography had the highest specificity for breast cancer imaging. A comparison of specificity between digital mammography and optical mammography was significant (p<0.021). If two or more breast diagnostic imaging tests are requested the overall sensitivity and specificity will increase. In this literature review study patients at high-risk of breast cancer were studied beside normal or sensitive women. The image modality performance of each breast test was compared for each.

• ETRI Journal
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• v.40 no.6
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• pp.794-801
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• 2018

This paper proposes a novel graphene-based optical microelectromechanical systems MEMS accelerometer that is dependent on the intensity modulation and optical properties of graphene. The designed sensing system includes a multilayer graphene finger, a laser diode (LD) light source, a photodiode, and integrated optical waveguides. The proposed accelerometer provides several advantages, such as negligible cross-axis sensitivity, appropriate linearity behavior in the operation range, a relatively broad measurement range, and a significantly wider bandwidth when compared with other important contributions in the literature. Furthermore, the functional characteristics of the proposed device are designed analytically, and are then confirmed using numerical methods. Based on the simulation results, the functional characteristics are as follows: a mechanical sensitivity of 1,019 nm/g, an optical sensitivity of 145.7 %/g, a resonance frequency of 15,553 Hz, a bandwidth of 7 kHz, and a measurement range of ${\pm}10g$. Owing to the obtained functional characteristics, the proposed device is suitable for several applications in which high sensitivity and wide bandwidth are required simultaneously.

• Current Optics and Photonics
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• v.5 no.6
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• pp.652-659
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• 2021

The theoretical analysis and optimization of extrinsic Fabry-Perot interferometer (EFPI) opticalfiber humidity sensors are deeply investigated. For a typical dual-cavity structure composed of an optical fiber and a humidity-sensitive membrane (HSM), the changes in refractive index (RI) and initial length are discussed for polymer materials and porous oxide materials when relative humidity (RH) increases. The typical interference spectrum is simulated at different RH using MATLAB. The spectral change caused by changing HSM RI and initial length are simulated simutineously, showing different influences on humidity response. To deeply investigate the influence on RH sensitivity, the typical response sensitivity curves for different HSM lengths and air-cavity lengths are simulated. The results show that the HSM is the vital factor. Short HSM length can improve the sensitivity, but for HSM RI and length the influences on sensitivity are opposite, because of the opposite spectral-shift trend. Deep discussion and an optimization method are provided to solve this problem. According to analysis, an opaque HSM is helpful to improve sensitivity. Furthermore, if using an opaque HSM, a short air cavity and long HSM length can improve the sensor's sensitivity These results provide deep understanding and some ideas for designing and optimizing highly sensitive EFPI fiber humidity sensors.

• Journal of the Korea Furniture Society
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• v.25 no.4
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• pp.338-344
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• 2014

Modern furniture design is advancing by putting value on individual sensitivity. Accordingly, this study will focus on optical art, which can give various changes in people's sensitivity. Optical art was actively applied in various fields of image, photograph, fashion, textile, accessory and interior from the 1950s till the 1960s. Optical art realized by Victor Vasarely (1908~) opened a new trend in art by accurately realizing concise and precise expressions. This study analyzed the impact of pattern expression on sensitivity in optical art and suggested a method, which can spatiotemporally maximize the emotional change by combining optical art with the form of furniture. Modern furniture design is changing toward the direction of fitting to the propensity and emotional taste of an individual. Accordingly, this study analyzed the emotional expression felt in the furniture modeling works featured by concise, straight and standardized rectangular shape. Based on the result of analysis, this study would like to suggest a method to utilize optical pattern as a means for emotional design, with which people are able to perform various emotional expressions while keeping the function and form of furniture.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.3
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• pp.218-223
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• 2016

This study examined the order of the Butterworth filter for the correlation on the sensitivity of the receiver in the receiver of an optical system. In the general case, the sensitivity of the receiver is increased if the order of the filter was increased more. This is because increasing the order of the filter response of the normalized frequency of the filter is similar to the rectangular wave. For that reason, the method used to increase the order of the filter increases the sensitivity of the receiver. On the other hand, a method of increasing the order of the filter and makes the system complicated increases the cost of the system. This study examined the correlation between the order of the sensitivity of the receiver filter and to configure the system by simply looking for ways to reduce the cost of the system. The simulation results showed that increasing the order of the filter resulted in a receiver that can determine if the sensitivity is raised. In addition, the order of the Butterworth filter range that does not reduce the sensitivity of the receiver was 2. Therefore, it will be possible to implement an inexpensive optical system of the receiver using the data from this study.

• Journal of Industrial and Engineering Chemistry
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• v.67
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• pp.236-243
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• 2018

A series of $Er^{3+}/Yb^{3+}$ co-doped fluorophosphate glasses with varying $YbF_3$ concentration were prepared by a high temperature melt quenching technique. Absorption and emission cross-sections were determined by using the McCumber theory. The larger emission cross-section ($9.86{\times}10^{-21}cm^2$) and longer fluorescence lifetime (12.37 ms) were obtained for the $^4I_{13/2}{\rightarrow}^4I_{15/2}$ transition of ABS3Er4Yb glass. The sensitivity and temperature of the maximum sensitivity were evaluated by the fluorescence intensity ratio method from the measured upconversion spectra. The results were discussed and compared to the other reported glasses.