• Title/Summary/Keyword: Low Contrast

Search Result 2,104, Processing Time 0.03 seconds

The Acquisition Process of Vowel System in Korean (한국어 모음 체계 습득 과정)

  • 안미리;김응모;김태경
    • Korean Journal of Cognitive Science
    • /
    • v.15 no.1
    • /
    • pp.1-11
    • /
    • 2004
  • The aim of this study is to reveal the order and the age of mastery of phonemic contrast in vowel sounds of Korean. For this purpose, we made an observation of the correspondences between the sounds produced by children of 12-35 months and the target sounds produced by adults. The provisional order and the age of contrast acquisition shown from the results of this study are as follows. First, the differential production of vowels by the feature relating to the body of the tongue precedes the differential production of vowels by the feature relating to the lip rounding. Second, as for the differential production of vowels by the feature relating to the body of the tongue, the contrast between the low vowels and the others is accomplished first, and the contrast between the high and low vowels and the contrast between the front and the back vowels are established around the age of 24 months. Third, as for the differential production of vowels by the feature relating to the lip rounding, the contrast between the rounded and the unrounded vowel is not accomplished until 36 months. Finally, we observed, prior to the completion of the differential production of phonemes, children use a specific phoneme excessively. This passing phrase could be interpreted as a result of over-application of a distinctive feature in the course of acquisition of it.

  • PDF

Enhanced High Contrast Image Rendering Method Using Visual Properties for Sharpness Perception (시각 선명도 감각 특성을 이용한 개선된 고명암 대비 영상 렌더링 기법)

  • Lee, Geun-Young;Lee, Sung-Hak;Kwon, Hyuk-Ju;Sohng, Kyu-Ik
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.38A no.8
    • /
    • pp.669-679
    • /
    • 2013
  • When an image is converted from HDR (high dynamic range) to LDR (low dynamic range), a tone mapping process is the essential component. Many TMOs (tone mapping operators) have been motivated by human vision which has lower physical luminance range than that in real scene. The representative of human vision properties which motivate TMOs is the local adaptation. However, TMOs are ultimately compressing image information such as contrast, saturation, etc. and the compression causes defects in image quality. In this paper, in order to compensate the degradation of the image which is caused by TMOs, the visual acuity-based edge stop function is proposed for applying the property of human vision to base-detail separation. In addition, using CSF (contrast sensitivity function) which represents the relationship among spatial frequency, contrast sensitivity, and luminance, the sharpness filter is designed and adaptively applied to the detail layer in regard to surround luminance.

The Evaluation of Image Quality According to the Change of Reconstruction Algorithm of CT Images (재구성 알고리즘 변화에 따른 CT 영상의 화질 평가)

  • Han, Dong-Kyoon;Park, Kun-Jin;Ko, Shin-Kwan
    • Korean Journal of Digital Imaging in Medicine
    • /
    • v.12 no.2
    • /
    • pp.127-132
    • /
    • 2010
  • In this study, the correlation among the changes of Modulation Transfer Function(MTF) in the noise and high-contrast resolution and the change of Contrast to noise ratio(CNR) in the low-contrast resolution will be examined to investigate the estimation of image quality according to the type of algorithms. The image data obtained by scanning American Association of Physicists in Medicine(AAPM) phantom was applied to each algorithm and the exposure condition of 120 kVp, 250 mAs, and then the CT number and noise were measured. The MTF curved line of the high-contrast resolution was calculated with Point Spread Function(PSF) by using the analysis program by Philips, resulting in 0.5 MTF, 0.1 MTF and 0.02 MTF respectively. The low-contrast resolution was calculated with CNR and the uniformity was measured to each algorithm. Since the measurement value for the uniformity of the equipment was below ${\pm}$ 5 HU, which is the criterion figure, it was found to belong to the normal range. As the algorithm got closer from soft to edge, the standard deviation of CT number increased, which indicates that the noise increased as well. As for MTF, 0.5 MTF, 0.1 MTF and 0.02 MTF were all sharp algorithms, and as the algorithm got closer from soft to edge, it was possible to distinguish more clearly with the naked eye. On the other hand, CNR gradually decreased, because the difference between the contrast hole CT number and the acrylic CT number was the same while the noise of hole increased.

  • PDF

A building roof detection method using snake model in high resolution satellite imagery

  • Ye Chul-Soo;Lee Sun-Gu;Kim Yongseung;Paik Hongyul
    • Proceedings of the KSRS Conference
    • /
    • 2005.10a
    • /
    • pp.241-244
    • /
    • 2005
  • Many building detection methods mainly rely on line segments extracted from aerial or satellite imagery. Building detection methods based on line segments, however, are difficult to succeed in high resolution satellite imagery such as IKONOS imagery, for most buildings in IKONOS imagery have small size of roofs with low contrast between roof and background. In this paper, we propose an efficient method to extract line segments and group them at the same time. First, edge preserving filtering is applied to the imagery to remove the noise. Second, we segment the imagery by watershed method, which collects the pixels with similar intensities to obtain homogeneous region. The boundaries of homogeneous region are not completely coincident with roof boundaries due to low contrast in the vicinity of the roof boundaries. Finally, to resolve this problem, we set up snake model with segmented region boundaries as initial snake's positions. We used a greedy algorithm to fit a snake to roof boundary. Experimental results show our method can obtain more .correct roof boundary with small size and low contrast from IKONOS imagery. Snake algorithm, building roof detection, watershed segmentation, edge-preserving filtering

  • PDF

Contrast Sensitivity as a Function of Spatial Frequency for 12 Year Old Child-Eye (눈의 공간주파수와 대비 민감도 함수(CSF) 특성에 대한 연구)

  • Kim, Yong Geun;Park, Sang-An
    • Journal of Korean Ophthalmic Optics Society
    • /
    • v.4 no.1
    • /
    • pp.63-68
    • /
    • 1999
  • It was made of a chart by new method to be measured the contrast sensitivity for a spatial frequency, and the mean luminance of a lattice frequency was made to three forms of 25, 50, 75% and let it to be ready a CS value from 0 to $10^3$. As a result of measuring of the CS value for a spatial frequency on a target of 12 year old students, CS value decreased of according to down the average luminance value and also the peak position shift to low spatial frequency. The low visioned person decreased the CS value in side of high frequency or in space of total frequency. By the lattice adaptation, a measured CS value was decreased in circumstance regions of adapted space frequency.

  • PDF

Image segmentation based on hierarchical structure and region merging using contrast for very low bit rate coding (초저속 부호화를 위한 계층적 구조와 대조를 이용한 영역 병합에 의한 영상 분할)

  • 송근원;김기석;박영식;이호영;하영호
    • Journal of the Korean Institute of Telematics and Electronics S
    • /
    • v.34S no.11
    • /
    • pp.102-113
    • /
    • 1997
  • In this paepr, a new image segmentation method reducing efficiently contour information causing bottleneck problem at segmentatio-based very low bit rate codingis proposed, while preserving objective and subjective quality. It consists of 4-level hierarchical image segmentation based on mathematical morphology and 1-leve region merging structure using contast of two adjacent regions. For two adjacent region pairs at the fourth level included in each region of the thid level, contrast is calculated. Among the pairs of two adjacent regions with less value than threshold, two adjacent regions having the minimum contrast are merged first. After region merging, texture of the merged region is updated. The procedure is performed recursively for all the adjacent region pairs at the fourth level included in each region of the third level. Compared with the previous method, the objective and subjective image qualities are similar. But it reduces 46.65% texture information on the average by decreasing total region number to be tansmitted. Specially, it shows reduction of the 23.95% contour information of the average. Thus, it can improve efficiently the bottleneck problem at segementation-based very low bit rate coding.

  • PDF

Contrast Enhancement of Laser Speckle Contrast Image in Deep Vasculature by Reduction of Tissue Scattering

  • Son, Taeyoon;Lee, Jonghwan;Jung, Byungjo
    • Journal of the Optical Society of Korea
    • /
    • v.17 no.1
    • /
    • pp.86-90
    • /
    • 2013
  • Various methods have been proposed for enhancing the contrast of laser speckle contrast image (LSCI) in subcutaneous blood flow measurements. However, the LSCI still suffers from low image contrast due to tissue turbidity. Herein, a physicochemical tissue optical clearing (PCTOC) method was employed to enhance the contrast of LSCI. Ex vivo and in vivo experiments were performed with porcine skin samples and male ICR mice, respectively. The ex vivo LSCIs were obtained before and 90 min after the application of the PCTOC and in vivo LSCIs were obtained for 60 min after the application of the PCTOC. In order to obtain the skin recovery images, saline was applied for 30 min after the application of the PCTOC was completed. The visible appearance of the tubing under ex vivo samples and the in vivo vasculature gradually enhanced over time. The LSCI increased as a function of time after the application of the PCTOC in both ex vivo and in vivo experiments, and properly recovered to initial conditions after the application of saline in the in vivo experiment. The LSCI combined with the PCTOC was greatly enhanced even in deep vasculature. It is expected that similar results will be obtained in in vivo human studies.

Dose Reduction According to the Exposure Condition in Intervention Procedure : Focus on the Change of Dose Area and Image Quality (인터벤션 시 방사선조사 조건에 따른 선량감소 : 면적선량과 영상화질 변화를 중심으로)

  • Hwang, Jun-Ho;Jung, Ku-Min;Kim, Hyun-Soo;Kang, Byung-Sam;Lee, Kyung-Bae
    • Journal of radiological science and technology
    • /
    • v.40 no.3
    • /
    • pp.393-400
    • /
    • 2017
  • The purpose of this study is to suggest a method to reduce the dose by Analyzing the dose area product (DAP) and image quality according to the change of tube current using NEMA Phantom. The spatial resolution and low contrast resolution were used as evaluation criteria in addition to signal to noise ratio (SNR) and contrast to noise ratio (CNR), which are important image quality parameters of intervention. Tube voltage was fixed at 80 kVp and the amount of tube current was changed to 20, 30, 40, and 50 mAs, and the dose area product and image quality were compared and analyzed. As a result, the dose area product increased from $1066mGycm^2$ to $6160mGycm^2$ to 6 times as the condition increased, while the spatial resolution and low contrast resolution were higher than 20 mAs and 30 mAs, Spatial resolution and low contrast resolution were observed below the evaluation criteria. In addition, the SNR and CNR increased up to 30 mAs, slightly increased at 40 mAs, but not significantly different from the previous one, and decreased at 50 mAs. As a result, the exposure dose significantly increased due to overexposure of the test conditions and the image quality deteriorated in all areas of spatial resolution, low contrast resolution, SNR and CNR.

Effects of Contrast Phases on Automated Measurements of Muscle Quantity and Quality Using CT

  • Dong Wook Kim;Kyung Won Kim;Yousun Ko;Taeyong Park;Jeongjin Lee;Jung Bok Lee;Jiyeon Ha;Hyemin Ahn;Yu Sub Sung;Hong-Kyu Kim
    • Korean Journal of Radiology
    • /
    • v.22 no.11
    • /
    • pp.1909-1917
    • /
    • 2021
  • Objective: Muscle quantity and quality can be measured with an automated system on CT. However, the effects of contrast phases on the muscle measurements have not been established, which we aimed to investigate in this study. Materials and Methods: Muscle quantity was measured according to the skeletal muscle area (SMA) measured by a convolutional neural network-based automated system at the L3 level in 89 subjects undergoing multiphasic abdominal CT comprising unenhanced phase, arterial phase, portal venous phase (PVP), or delayed phase imaging. Muscle quality was analyzed using the mean muscle density and the muscle quality map, which comprises normal and low-attenuation muscle areas (NAMA and LAMA, respectively) based on the muscle attenuation threshold. The SMA, mean muscle density, NAMA, and LAMA were compared between PVP and other phases using paired t tests. Bland-Altman analysis was used to evaluate the inter-phase variability between PVP and other phases. Based on the cutoffs for low muscle quantity and quality, the counts of individuals who scored lower than the cutoff values were compared between PVP and other phases. Results: All indices showed significant differences between PVP and other phases (p < 0.001 for all). The SMA, mean muscle density, and NAMA increased during the later phases, whereas LAMA decreased during the later phases. Bland-Altman analysis showed that the mean differences between PVP and other phases ranged -2.1 to 0.3 cm2 for SMA, -12.0 to 2.6 cm2 for NAMA, and -2.2 to 9.9 cm2 for LAMA.The number of patients who were categorized as low muscle quantity did not significant differ between PVP and other phases (p ≥ 0.5), whereas the number of patients with low muscle quality significantly differed (p ≤ 0.002). Conclusion: SMA was less affected by the contrast phases. However, the muscle quality measurements changed with the contrast phases to greater extents and would require a standardization of the contrast phase for reliable measurement.

Perfusion MR Imaging in Gliomas: Comparison with Histologic Tumor Grade

  • Sun Joo Lee;Jae Hyoung Kim;Young Mee Kim;Gyung Kyu Lee;Eun Ja Lee;In Sung Park;Jin-Myung Jung;Kyeong Hun Kang;Taemin Shin
    • Korean Journal of Radiology
    • /
    • v.2 no.1
    • /
    • pp.1-7
    • /
    • 2001
  • Objective: To determine the usefulness of perfusion MR imaging in assessing the histologic grade of cerebral gliomas. Materials and Methods: In order to determine relative cerebral blood volume (rCBV), 22 patients with pathologically proven gliomas (9 glioblastomas, 9 anaplastic gliomas and 4 low-grade gliomas) underwent dynamic contrast-enhanced T2*-weighted and conventional T1- and T2-weighted imaging. rCBV maps were obtained by fitting a gamma-variate function to the contrast material concentration versus time curve. rCBV ratios between tumor and normal white matter (maximum rCBV of tumor / rCBV of contralateral white matter) were calculated and compared between glioblastomas, anaplastic gliomas and low-grade gliomas. Results: Mean rCBV ratios were 4.90°±1.01 for glioblastomas, 3.97°±0.56 for anaplastic gliomas and 1.75°±1.51 for low-grade gliomas, and were thus significantly different; p < .05 between glioblastomas and anaplastic gliomas, p < .05 between anaplastic gliomas and low-grade gliomas, p < .01 between glioblastomas and low-grade gliomas. The rCBV ratio cutoff value which permitted discrimination between high-grade (glioblastomas and anaplastic gliomas) and low-grade gliomas was 2.60, and the sensitivity and specificity of this value were 100% and 75%, respectively. Conclusion: Perfusion MR imaging is a useful and reliable technique for estimating the histologic grade of gliomas.

  • PDF