Norimichi Tsumura

Chiba University, Tiba, Chiba, Japan

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Publications (204)68.37 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Abstract In this article, the authors propose a method to estimate the reflectance property from refocused images from a light source reflected on an object. The blurred information of the light source on the surface of the object is expected to be a practical method to estimate the reflectance property, although various methods have previously been proposed. Because the degree of blurred information is changed with the position of focus in the camera, the authors introduce a light field camera that can change the position of focus after the image is captured. In this research, the authors chose the refocused image where the light source is focused through the reflection on the object surface. Based on the blurred information of the focused light source, they estimate the reflectance property of the object. The estimated reflectance property is applied to inverse rendering for auto material appearance balancing.
    Journal of Imaging Science and Technology 05/2015; 59(3). DOI:10.2352/J.ImagingSci.Technol.2015.59.3.030501 · 0.40 Impact Factor
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    ABSTRACT: Tongue diagnosis is a noninvasive diagnosis and is traditionally one of the most important tools for physicians who practice Kampo (traditional Japanese) medicine. However, it is a subjective process, and its results can depend on the experience of the physician performing it. Previous studies have reported how to measure and evaluate the shape and color of the tongue objectively. Therefore, this study focused on the glossy component in order to quantify tongue moisture in tongue diagnosis. We hypothesized that moisture appears as a gloss in captured images and measured the amount of water on the tongue surface in 13 subjects. The results showed a high correlation between the degree of gloss and the amount of water on the tongue surface and suggested that the moisture on the tongue can be estimated by the degree of gloss in a captured image. Because the moisture level on the tongue changes during the course of taking photos, it became clear that we had to wait at least 3 minutes between photos. Based on these results, we established the tongue image analyzing system (TIAS), which can consistently record the gloss and color of the tongue surface simultaneously.
    BioMed Research International 01/2015; 2015:249609. DOI:10.1155/2015/249609 · 2.71 Impact Factor
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    ABSTRACT: We present a rendering method to reproduce translucent appearances in real-time. Since the translucency is caused by complicated light behavior such as scattering and absorption, reproducing translucent material requires computationally expensive cost. Due to its computational cost, it is difficult to apply the digital mock-up with the computer graphics for the purpose of cost reduction and acceleration of developing products. In order to reproduce the translucent appearance rapidly, we focus on the contrast-reversing image processing. We embed this simple image processing method to the reflection model. Our proposed method can reproduce in real-time with almost the same appearance compared to commercial rendering software.
    11/2014;
  • Misa Hirose, Yuri Tatsuzawa, Saori Toyota, Norimichi Tsumura
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    ABSTRACT: In this research, we evaluate the visibility of age spot and freckle with changing the blood volume based on the actual facial color images and compare the result with that of pigmentation patterns generated by simulated spectral reflectance. We acquire the concentration distribution of melanin, hemoglobin and shading components by applying the independent component analysis on a facial color image. We reconstruct images by using the obtained melanin and shading concentration and the changed hemoglobin concentration to generate facial images with changing the blood volume. Finally, we evaluate the visibility of pigmentations using these images and compare with the result of pigmentation patterns based on simulated reflectance. In our previous study, we have already evaluated the visibility of pigmentation patterns, and the visibility became lower as the blood volume increases. However, we can see that a specific blood volume reduce the visibility of the actual pigmentations from the result of evaluating the skin color images.
    11/2014;
  • Artificial Life and Robotics 09/2014; 19(2):170-175. DOI:10.1007/s10015-014-0154-0
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    ABSTRACT: Abstract In this article, principal component analysis is applied to pigmentation distribution in the whole face to obtain feature values, and the relationship between the obtained feature vectors and age is estimated by multiple regression analysis to simulate the changes of facial images in women of ages 10 to 80. Since the human face receives more attention than other body parts, a change of a small quantity of the features in a face makes a large difference to its appearance. We can divide the features into two categories. One category is physical features such as skin condition and shape, and the other is physiological features, which are influenced by age and health. In the beauty industry, the synthesis of skin texture is based on these two kinds of feature values. Previous works have analyzed only small areas of skin texture. By morphing the shapes of facial images to that of an average face and extending the analyzed area to the whole face, the authors’ method can analyze pigmentation distributions in the whole face and simulate the appearance of a face as a function of changing the person’s age.
    Biocontrol Science and Technology 03/2014; 58(2). DOI:10.2352/J.ImagingSci.Technol.2014.58.2.020503 · 0.73 Impact Factor
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    ABSTRACT: In this paper, we propose using earth mover’s distance (EMD) to obtain the appropriate similarity between each histogram for segmentation of abnormal liver regions with mapping of the distances by multidimensional scaling. Conventionally, the similarity between each histogram is calculated by integrating the difference between each bin of the histograms. However, this similarity is unsuitable for appropriate comparison of the histograms because the number of bins for calculating the local histograms of computed tomography images varies. We used EMD to resolve this problem regarding the difference in bin numbers, and the obtained distances are used for mapping the local histograms by multidimensional scaling to low-dimensional space. In the low-dimensional space, the abnormal liver region was well segmented by support vector machine in the test datasets.
    Artificial Life and Robotics 12/2013; 18(3-4). DOI:10.1007/s10015-013-0110-4
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    ABSTRACT: We measured the oxygen saturation of skin at various ages by iterating our previously proposed method that can rapidly simulate skin spectral reflectance with high accuracy. Oxygen saturation is commonly measured by a pulse oximeter to evaluate oxygen delivery for monitoring the functions of heart and lungs at a specific time. On the other hand, oxygen saturation of skin is expected to assess peripheral conditions. Our previously proposed method, the optical path-length matrix method (OPLM), is based on a Monte Carlo model of steady-state light transport in multi-layered tissue (MCML), but can simulate skin spectral reflectance 27,000 times faster than MCML. In this study, we implemented an iterative OPLM with a nonlinear optimization technique such that this method can also be used for estimating hemoglobin concentration and oxygen saturation from the measured skin spectral reflectance. The iterative OPLM was over 25,000 times faster than the MCML with 95 % accuracy. Before measurements in clinic, stability of oxygen saturation among measuring pressure was confirmed. Then, the skin reflectance spectra of 72 outpatients aged between 20 and 86 years were measured by a spectrophotometer. Three points were measured for each subject: the forearm, the thenar eminence, and the intermediate phalanx. The result showed that the oxygen saturation of skin remained constant at each point as the age varied.
    Artificial Life and Robotics 12/2013; 18(3-4). DOI:10.1007/s10015-013-0111-3
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    ABSTRACT: Since metabolic syndrome is a cause of lifestyle-related diseases, and its early diagnosis and an evaluation of visceral fat are important, this study proposes a new method of estimating the amount of fat. The goal of this study is to estimate visceral fat from estimation of subcutaneous fat and total fat. The subcutaneous fat is estimated from the elasticity of the lumbar area, and the total fat is estimated from body information such as the abdominal vertical and lateral width, and body weight. Finally, the estimated subcutaneous fat is subtracted from the estimated total fat to calculate the visceral fat. Measurement tests conducted to verify the constructed visceral fat estimation model showed good results, with a correlation of 0.96 between the visceral fat area estimated by the proposed method and the actual measured area. The reproducibility of the estimation model was also verified by the cross validation method.
    Artificial Life and Robotics 02/2013; DOI:10.1007/s10015-013-0133-x
  • Kimiyoshi Miyata, Norimichi Tsumura
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    ABSTRACT: A concept of image quality metamerism as an expansion of conventional metamerism defined in color science is introduced, and it is applied to segment similar color areas in a cultural property. The image quality metamerism can unify different image quality attributes based on an index showing the degree of image quality metamerism proposed. As a basic research step, the index is consisted of color and texture information and examined to investigate a cultural property. The property investigated is a pair of folding screen paintings that depict the thriving city of Kyoto designated as a nationally important cultural property in Japan. Gold-colored areas painted by using high granularity colorants compared with other color areas are evaluated based on the image quality metamerism index locally, then the index is visualized as a map showing the possibility of the image quality metamer to the reference pixel set in the same image. This visualization means a segmentation of areas where color is similar but texture is different. The experimental result showed that the proposed method was effective to show areas of gold color areas in the property.
    Journal of Electronic Imaging 01/2013; 22(1):3029-. DOI:10.1117/1.JEI.22.1.013029 · 0.85 Impact Factor
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    ABSTRACT: In this paper, we apply principal component analysis to pigmentation distribution in whole face and obtain feature values. Furthermore, we estimate the relationship between the obtained vectors and the ages and simulate the changes of women facial image from in her 20s to in her any age by multiple regression analysis. Human faces is the well-known part which receive a lot of attention in the body. Changing the small quantity of the features in faces make large differences in their appearance. The features which we can receive divide broadly into two categories. One is the physical feature such as skin condition and its shape, and another one is the psychological features such as the ages and the health. In the beauty industry it is required to synthesize the skin texture based on the two kinds of the feature values. Previous works remain in the analysis of the skin texture using small area. By morphing shape of facial images to that of average face and extending the analyzed area to whole face, our method can analyze pigmentation distribution in whole face and simulate appearance of face by changing the age.
    01/2013;
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    ABSTRACT: In this article, we propose a new method—the optical path-length matrix method (OPLM)—as a faster alternative to the Monte Carlo for multi-layered media (MCML), which is often used to simulate the skin spectrum. Theoretically, peripheral oxygen saturation can be estimated by iterating MCML, but it is not a realistic strategy because it requires huge computation time. The optical path-length matrix is obtained as the probabilistic density histograms of the optical path length in skin using MCML, and once the matrix is obtained, skin spectral reflectance can be calculated by accumulating all combinations of elements in the matrix and by setting an absorption coefficient based on the Beer-Lambert law. The computational time of OPLM was approximately 26,000 times faster than that of MCML.
    Optical Review 11/2012; 19(6):361-365. DOI:10.1007/s10043-012-0058-y · 0.55 Impact Factor
  • Ahmed Mahmoud Hamad, Norimichi Tsumura
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    ABSTRACT: Background model updating is a vital process for any background subtraction technique. This paper presents an updating mechanism that can be applied efficiently to any background subtraction technique. This updating mechanism exploits the color and spatial features to characterize each detected object. Spatial and color features are used to classify each detected object as a moving background object, a ghost, or a real moving object. The starting position of each detected object is the cue for updating background images. In addition, this paper presents a hybrid scheme to detect and remove cast shadows based on texture and color features. The robustness of the proposed method and its effectiveness in overcoming challenging problems such as gradual and sudden illumination changes, ghost appearance, non-stationary background objects, the stability of moving objects most of the time, and cast shadows are verified quantitatively and qualitatively.
    Optical Review 05/2012; 19(3). DOI:10.1007/s10043-012-0030-x · 0.55 Impact Factor
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    ABSTRACT: Conventional 3-dimensional color spaces such as L*a*b* or L*C*h have a limitation in that colors of materials can only be separated on the same hyperplane. Therefore, it would be useful to find appropriate axes for dental color analysis by analyzing spectral data itself, rather than conventional 3-dimensional color spaces. Hyperspectral data are detailed color spectra with narrow spectral bands over a continuous spectral range. We acquired hyperspectral data of the shade guides without specular reflection, and standardized them as reflectance data. Then, reflectance data were weighed by luminous efficiency function, and used in principal component analysis (PCA). Principal components (PCs) and their contribution, and values of respective shades to respective PCs were calculated as PC scores. Cumulate contribution rate of 1st to 3rd PCs were approximately 100%, which meant shade colors were very similar to each other. Respective PCs showed specific figures, and values of shades showed sequences unique to each PC, which were independent of each other; values to the 1st PC showed gradual changes with change in shade numbering, values to the 2nd PC showed relatively high scores on opaque shades, values to the 4th PC showed lower scores on B and C group shades, and values to the 6th PC showed differences between manufacturers. Using PCA, we could find axes independent of the conventional 3-dimensional color spaces. These axes reflected certain changes which are not detected on conventional color spaces. Our methods are taking into account color matching under any illumination by focusing on the spectra themselves, and we can discuss about components of the teeth from spectra of resulting principal components. By applying our method to conventional systems, it would help diagnose color differences of dental materials.
    Dental materials: official publication of the Academy of Dental Materials 04/2012; 28(7):736-42. DOI:10.1016/j.dental.2012.03.010 · 4.16 Impact Factor
  • Ahmed Mahmoud Hamad, Norimichi Tsumura
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    ABSTRACT: This paper proposes a robust method to detect and extract silhouettes of foreground objects from a video sequence of a static camera based on the improved background subtraction technique. The proposed method analyses statistically the pixel history as time series observations. The proposed method presents a robust technique to detect motions based on kernel density estimation. Two consecutive stages of the k-means clustering algorithm are utilized to identify the most reliable background regions and decrease the detection of false positives. Pixel and object based updating mechanism for the background model is presented to cope with challenges like gradual and sudden illumination changes, ghost appearance, non-stationary background objects, and moving objects that remain stable for more than the half of the training period. Experimental results show the efficiency and the robustness of the proposed method to detect and extract the silhouettes of moving objects in outdoor and indoor environments compared with conventional methods.
    Optical Review 03/2012; 19(2). DOI:10.1007/s10043-012-0009-7 · 0.55 Impact Factor
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    ABSTRACT: — In this paper, the relative influences of misalignment such as cross-talk, vertical shift, and motion blur on visual fatigue by using a binocular stereoscopic display has been verified. Experiments were conducted for two cases: a still image and a motion image. They were evaluated by using the simulator sickness questionnaire (SSQ). By changing the disparity angle, cross-talk, and vertical shift in the still-image experiment, it was found that the SSQ score of each parameter increased as the amount of each factor increased. With a two-sample t-test between the presence and absence of each factor, a significant difference was found for the case of a more than 36-arcmin disparity, more than 20% cross-talk, and more than 10% vertical shift. In the motion-image experiment, in which motion speed and the misalignment were varied, it was found that movement of the disparity angle caused much more visual fatigue in comparison with the misalignment factors, which were cross-talk and vertical shift. In contrast, motion images in addition to the cross-talk and/or vertical shift had a slight but unnoticeable relationship to an increase in visual fatigue. Therefore, it was concluded that vertical shift dominated the evaluation for still images, and the movement itself dominated the evaluation for motion images. The results suggest that it is necessary to evaluate visual fatigue according to the representing case, still or motion images, of a 3-D stereoscopic display.
    02/2012; 20(2). DOI:10.1889/JSID20.2.94
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    ABSTRACT: We measured the oxygen saturation of skin at various ages using our previously proposed method that can rapidly simulate skin spectral reflectance with high accuracy. Oxygen saturation is commonly measured by a pulse oximeter to evaluate oxygen delivery for monitoring the functions of heart and lungs at a specific time. On the other hand, oxygen saturation of skin is expected to assess peripheral conditions. Our previously proposed method, the optical path-length matrix method (OPLM), is based on a Monte Carlo for multi-layered media (MCML), but can simulate skin spectral reflectance 27,000 times faster than MCML. In this study, we implemented an iterative simulation of OPLM with a nonlinear optimization technique such that this method can also be used for estimating hemoglobin concentration and oxygen saturation from the measured skin spectral reflectance. In the experiments, the skin reflectance spectra of 72 outpatients aged between 20 and 86 years were measured by a spectrophotometer. Three points were measured for each subject: the forearm, the thenar eminence, and the intermediate phalanx. The result showed that the oxygen saturation of skin remained constant at each point as the age varied.
    Proceedings of SPIE - The International Society for Optical Engineering 02/2012; DOI:10.1117/12.907874 · 0.20 Impact Factor
  • Kimiyoshi Miyata, Norimichi Tsumura
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    ABSTRACT: In this paper, we introduce a concept of the image quality metamerism as an expanded version of the metamerism defined in the color science. The concept is used to unify different image quality attributes, and applied to introduce a metric showing the degree of image quality metamerism to analyze a cultural property. Our global goal is to build a metric to evaluate total quality of images acquired by different imaging systems and observed under different viewing conditions. As the basic step to the global goal, the metric is consisted of color, spectral and texture information in this research, and applied to detect image quality metamers to investigate the cultural property. The property investigated is the oldest extant version of folding screen paintings that depict the thriving city of Kyoto designated as a nationally important cultural property in Japan. Gold colored areas painted by using high granularity colorants compared with other color areas in the property are evaluated based on the metric, then the metric is visualized as a map showing the possibility of the image quality metamer to the reference pixel.
    Proceedings of SPIE - The International Society for Optical Engineering 01/2012; DOI:10.1117/12.907694 · 0.20 Impact Factor
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    ABSTRACT: In Kampo medicine (Japanese traditional herbal medicine), the appearance of the tongue contains a lot of useful information for diagnosis. However, an inspection of the tongue is not considered to be important in modern medical diagnosis, since the skills applied in the examination are difficult to understand. Thus, we developed an imaging system and algorithm for quantitative analysis of the tongue to provide the traditional techniques of Kampo with greater objectivity. Tongue images were taken from 9 healthy subjects for 3 consecutive weeks (5 days/week), 12 times a day, with 300 images taken successively within 30 s each time. Then, the temporal color changes in 30 s, 1 day, and 3 weeks were measured in the device-independent International Commission on Illumination (CIE) 1976 L*a*b* color space. The tongue color change in 30 s varied between individuals, and it was mainly classified into 3 patterns. This image acquisition system and valid color management should help all tongue-related research, and the 30-s temporal color change might be an important target for further tongue analysis. We were able to acquire tongue images without specular reflection and with valid color reproduction, and the color change in 30 s was found to vary. Tongue color changes have not been mentioned in the classics of Kampo medicine, since they were certainly impossible to discriminate by the naked eye. The change during 30 s is a new finding based on the electronic devices, and together they are expected to become a new criterion for tongue analysis.
    Forschende Komplementärmedizin / Research in Complementary Medicine 01/2012; 19(2):80-5. DOI:10.1159/000338516 · 1.65 Impact Factor
  • Journal of Vision 12/2011; 11(15):64-64. DOI:10.1167/11.15.64 · 2.73 Impact Factor

Publication Stats

976 Citations
68.37 Total Impact Points

Institutions

  • 1995–2015
    • Chiba University
      • • Graduate School of Advanced Integration Science
      • • Graduate School of Medicine
      • • Division of Information Sciences
      • • Graduate School of Science and Technology
      • • Department of Information Processing and Computer Science
      Tiba, Chiba, Japan
  • 2003–2005
    • Kao Corporation
      Edo, Tōkyō, Japan
  • 1993
    • Osaka University
      • Department of Applied Physics
      Suika, Ōsaka, Japan