• Title/Summary/Keyword: Low Contrast

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A Relationship between Kinetic Visual Acuity and Contrast Sensitivity (동적시력과 대비감도의 상관관계)

  • Shim, Moon-Sik;Kang, Hye-Sook;Kim, Sang-Hyun;Shim, Hyun-Suk
    • Journal of Korean Ophthalmic Optics Society
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    • v.19 no.2
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    • pp.225-229
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    • 2014
  • Purpose: The study was to analyze the correlation between kinetic visual acuity (KVA), visual acuity(static visual angle, SVA) and contrast sensitivity. Methods: Ninety-nine undergraduate students studying Ophthalmic Optics were fully corrected by the Topcon CV-3000 Phoropter. The contrast sensitivity was measured for the participants under the photopic condition ($100cd/m^2$) with Vector Vision CSV-1000E at 2.5 meter, while KVA was measured with KOWA AS-4A. The participants were classified into three groups L, M and H depending on the KVA (0.1~0.3, 0.31~0.6 and greater than 0.61, respectively) and were analyzed whether there was the correlation between the contrast sensitivity, visual acuity and refractive error. Results: The KVA was correlated with the contrast sensitivity for 3 cpd (r=0.26), for 6 cpd (r=0.48), for 12 cpd (r=0.38) and 18 cpd (r=0.47). Except for the low frequency of 3 cpd, they all were higher than the one of the SVA and the KVA (r = -0.37). The contrast sensitivity for 3, 6, 12 and 18 cpd was 59.41, 92.22, 38.41 and 14.39 in the group L, respectively. The contrast sensitivity in the group M was 66.03, 108.78, 53.51 and 19.20 and the one in the group H was 70.90, 146.10, 62.90 and 25.33 for 3, 6, 12 and 18 cpd, respectively. Conclusions: The correlation of the contrast sensitivity and the KVA was higher than the one of the contrast sensitivity and the SVA. It can be assumed that the contrast sensitivity will be high if the KVA is high, except for the case for low spatial frequency.

Electro-optical Properties of Polymer Dispersed Liquid Crysta Displays (고분자 분상형 액정표시소자의 전기광학적 특성 연구)

  • 박우상;고영부;박세근
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.11 no.10
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    • pp.885-890
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    • 1998
  • The electro-optical properties of polymer dispersed liquid crystals (PDLCs) depend on dispersion structures and nematic alignment which can be controlled by taking proper liquid crystal/polymer mixtures and process conditions. To achieve excellent electro-optical properties such as low driving voltage, good contrast ratio and negligible hysteresis, we have developed optimization procedure. Under the optimized conditions, PDLC of low threshold voltage less than 3.1 V, high contrast ratio more than 150 and negligible hysteresis were obtained.

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Enhancing Single Thermal Image Depth Estimation via Multi-Channel Remapping for Thermal Images (열화상 이미지 다중 채널 재매핑을 통한 단일 열화상 이미지 깊이 추정 향상)

  • Kim, Jeongyun;Jeon, Myung-Hwan;Kim, Ayoung
    • The Journal of Korea Robotics Society
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    • v.17 no.3
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    • pp.314-321
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    • 2022
  • Depth information used in SLAM and visual odometry is essential in robotics. Depth information often obtained from sensors or learned by networks. While learning-based methods have gained popularity, they are mostly limited to RGB images. However, the limitation of RGB images occurs in visually derailed environments. Thermal cameras are in the spotlight as a way to solve these problems. Unlike RGB images, thermal images reliably perceive the environment regardless of the illumination variance but show lacking contrast and texture. This low contrast in the thermal image prohibits an algorithm from effectively learning the underlying scene details. To tackle these challenges, we propose multi-channel remapping for contrast. Our method allows a learning-based depth prediction model to have an accurate depth prediction even in low light conditions. We validate the feasibility and show that our multi-channel remapping method outperforms the existing methods both visually and quantitatively over our dataset.

Vicarious excretion of contrast medium to small intestine in a dog with Toxocara canis infection

  • Sieun Park;Jin-Ok Ahn;Jinyoung Chung;Kija Lee;Inchul Park;Sooyoung Choi
    • Korean Journal of Veterinary Research
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    • v.62 no.4
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    • pp.33.1-33.4
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    • 2022
  • A male mixed-breed dog of unknown age was presented with a history of bloody diarrhea and cachexia. Toxocara canis in vomitus was identified by a parasitologist. Hematology revealed low hematocrit, eosinophilia, and low albumin. Computed tomography (CT) revealed an enlarged pulmonary artery with an irregular wall, micronodules in the lung, and vicarious excretion of contrast medium to small intestine. CT scan was helpful for identifying lung lesions and the central organs of larval migration and also show vicarious excretion of contrast medium to the small intestine in T. canis infection.

Contrast Sensitivity and Glare with Spherical and Toric Soft Contact Lenses in Low-astigmatic Eyes (구면과 토릭 소프트 렌즈로 교정한 약도 난시안의 대비감도와 눈부심)

  • Lee, Min-Ah;Kim, Hyun Jung;Kim, Jai-Min
    • Journal of Korean Ophthalmic Optics Society
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    • v.14 no.1
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    • pp.39-45
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    • 2009
  • Purpose: The purpose of this study is to compare the visual performance by contrast sensitivity (CS) and disability glare (DG) in low astigmatic eyes corrected with toric soft lenses and other optical corrections. Methods: Twenty university students with myopia (-1.00 to -6.50D Sph. with astigmatism up to 1.50 cyl) were enrolled and corrected by five different methods: 1) soft toric lenses; 2) spherical soft contact lenses; 3) RGP lenses; 4) best spectacle corrected visual acuity; 5) spherical equivalent spectacles. All subjects had corrected vision acuity of 20/20 or better. Contrast sensitivity and disability glare were measured using the OPTEC 6500 contrast sensitivity view-in tester included the EyeView Functional Vision Analysis software at photopic or mesopic conditions with glare. Results: At photopic condition, best corrected spectacle wearers had the highest monocular contrast sensitivity at all spatial frequency followed by soft toric lenses, RGP lenses, spherical equivalent spectacles, and spherical soft contact lenses. However, all of them were in normal contrast sensitivity value at photopic condition. At mesopic condition with glare, toric soft lenses were the highest and followed by RGP lenses, spherical equivalent spectacles, best spectacle corrected visual acuity and spherical soft contact lenses. It was observed that spherical soft contact lens wearers demonstrated lower range than normal contrast sensitivity value at mesopic condition with glare. Conclusion: Toric soft lenses gave better visual performance than spherical soft lenses in low astigmatic eyes. Subjects requiring the use of contact lenses under mesophic conditions could benefit from toric soft lenses.

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Diagnostic Efficacy and Safety of Low-Contrast-Dose Dual-Energy CT in Patients With Renal Impairment Undergoing Transcatheter Aortic Valve Replacement

  • Suyon Chang;Jung Im Jung;Kyongmin Sarah Beck;Kiyuk Chang;Yaeni Kim;Kyunghwa Han
    • Korean Journal of Radiology
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    • v.25 no.7
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    • pp.634-643
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    • 2024
  • Objective: This study aimed to evaluate the diagnostic efficacy and safety of low-contrast-dose, dual-source dual-energy CT before transcatheter aortic valve replacement (TAVR) in patients with compromised renal function. Materials and Methods: A total of 54 consecutive patients (female:male, 26:38; 81.9 ± 7.3 years) with reduced renal function underwent pre-TAVR dual-energy CT with a 30-mL contrast agent between June 2022 and March 2023. Monochromatic (40- and 50-keV) and conventional (120-kVp) images were reconstructed and analyzed. The subjective quality score, vascular attenuation, contrast-to-noise ratio (CNR), and signal-to-noise ratio (SNR) were compared among the imaging techniques using the Friedman test and post-hoc analysis. Interobserver reliability for aortic annular measurement was assessed using the intraclass correlation coefficient (ICC) and Bland-Altman analysis. The procedural outcomes and incidence of post-contrast acute kidney injury (AKI) were assessed. Results: Monochromatic images achieved diagnostic quality in all patients. The 50-keV images achieved superior vascular attenuation and CNR (P < 0.001 in all) while maintaining a similar SNR compared to conventional CT. For aortic annular measurement, the 50-keV images showed higher interobserver reliability compared to conventional CT: ICC, 0.98 vs. 0.90 for area and 0.97 vs. 0.95 for perimeter; 95% limits of agreement width, 0.63 cm2 vs. 0.92 cm2 for area and 5.78 mm vs. 8.50 mm for perimeter. The size of the implanted device matched CT-measured values in all patients, achieving a procedural success rate of 92.6%. No patient experienced a serum creatinine increase of ≥ 1.5 times baseline in the 48-72 hours following CT. However, one patient had a procedural delay due to gradual renal function deterioration. Conclusion: Low-contrast-dose imaging with 50-keV reconstruction enables precise pre-TAVR evaluation with improved image quality and minimal risk of post-contrast AKI. This approach may be an effective and safe option for pre-TAVR evaluation in patients with compromised renal function.

Color Enhancement of Low Exposure Images using Histogram Specification and its Application to Color Shift Model-Based Refocusing

  • Lee, Eunsung;Kang, Wonseok;Kim, Sangjin
    • IEIE Transactions on Smart Processing and Computing
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    • v.1 no.1
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    • pp.8-16
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    • 2012
  • An image obtained from a low light environment results in a low-exposure problem caused by non-ideal camera settings, i.e. aperture size and shutter speed. Of particular note, the multiple color-filter aperture (MCA) system inherently suffers from low-exposure problems and performance degradation in its image classification and registration processes due to its finite size of the apertures. In this context, this paper presents a novel method for the color enhancement of low-exposure images and its application to color shift model-based MCA system for image refocusing. Although various histogram equalization (HE) approaches have been proposed, they tend to distort the color information of the processed image due to the range limits of the histogram. The proposed color enhancement algorithm enhances the global brightness by analyzing the basic cause of the low-exposure phenomenon, and then compensates for the contrast degradation artifacts by using an adaptive histogram specification. We also apply the proposed algorithm to the preprocessing step of the refocusing technique in the MCA system to enhance the color image. The experimental results confirm that the proposed method can enhance the contrast of any low-exposure color image acquired by a conventional camera, and is suitable for commercial low-cost, high-quality imaging devices, such as consumer-grade camcorders, real-time 3D reconstruction systems, digital, and computational cameras.

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Development of a Contrast Enhancer for MD Projection TV (wwMD 프로젝션 TV의 명암비 향상 액츄에이터 개발)

  • Kim, Jae-Eun;Yun, Gi-Tak;Lee, Jong-Jin;Hong, Sam-Nyol;Ko, Eui-Seok;Ju, Chae-Min;Yang, Sang-Sik
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2006.05a
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    • pp.656-659
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    • 2006
  • MD (DLP, LCoS) Projection TV is appropriate for large screen display with high definition at a relatively low price and thus, has been popular in the digital TV market. In order to realize high resolutions in the DLP projection TV, we successfully developed the Pixel Enhancement Actuator. Furthermore, it is also required that the contrast ratio of projected video signals onto a large screen should be improved. Therefore, we propose a contrast enhancer which adjusts the amount of projected lights by a dynamic aperture and a attached position sensor.

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Contrast Enhanced Ultrasonography and CT Features of Gastrointestinal Stromal Tumor in a Dog

  • Saran Chhoey;Soyeon Kim;Kroesna Kang;Sath Keo;Jihye Choi
    • Journal of Veterinary Clinics
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    • v.40 no.5
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    • pp.375-381
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    • 2023
  • A large abdominal mass was incidentally found in a 13-year-old mixed-breed dog and was confirmed to be a cecal gastrointestinal stromal tumor (GIST). Contrast-enhanced ultrasound and post-contrast computed tomography (CT) showed mild contrast enhancement of the mass, indicating low blood flow. The tumor origin was determined to be the cecum by identifying the vessels supplying the mass on post-contrast CT. The exophytic growth of the tumor left the cecal lumen intact without obstruction. This report described the CEUS and CT perfusion of the cecal GIST and perfusion evaluation can help diagnose and characterize GISTs in dogs.