The search functionality is under construction.

Author Search Result

[Author] Akira KOJIMA(4hit)

1-4hit
  • Stabilization Technique for Region-of-Interest Trajectories Made from Video Watching Manipulations

    Daisuke OCHI  Hideaki KIMATA  Yoshinori KUSACHI  Kosuke TAKAHASHI  Akira KOJIMA  

     
    PAPER-Human-computer Interaction

      Vol:
    E97-D No:2
      Page(s):
    266-274

    Due to the recent progress made in camera and network environments, on-line video services enable people around the world to watch or share high-quality HD videos that can record a wider angle without losing objects' details in each image. As a result, users of these services can watch videos in different ways with different ROIs (Regions of Interest), especially when there are multiple objects in a scene, and thus there are few common ways for them to transfer their impressions for each scene directly. Posting messages is currently the usual way but it does not sufficiently enable all users to transfer their impressions. To transfer a user's impressions directly and provide users with a richer video watching experience, we propose a system that enables them to extract their favorite parts of videos as ROI trajectories through simple and intuitive manipulation of their tablet device. It also enables them to share a recorded trajectory with others after stabilizing it in a manner that should be satisfactory to every user. Using statistical analysis of user manipulations, we have demonstrated an approach to trajectory stabilization that can eliminate undesirable or uncomfortable elements due to tablet-specific manipulations. The system's validity has been confirmed by subjective evaluations.

  • Extrinsic Camera Calibration of Display-Camera System with Cornea Reflections

    Kosuke TAKAHASHI  Dan MIKAMI  Mariko ISOGAWA  Akira KOJIMA  Hideaki KIMATA  

     
    PAPER-Image Recognition, Computer Vision

      Pubricized:
    2018/09/26
      Vol:
    E101-D No:12
      Page(s):
    3199-3208

    In this paper, we propose a novel method to extrinsically calibrate a camera to a 3D reference object that is not directly visible from the camera. We use a human cornea as a spherical mirror and calibrate the extrinsic parameters from the reflections of the reference points. The main contribution of this paper is to present a cornea-reflection-based calibration algorithm with a simple configuration: five reference points on a single plane and one mirror pose. In this paper, we derive a linear equation and obtain a closed-form solution of extrinsic calibration by introducing two ideas. The first is to model the cornea as a virtual sphere, which enables us to estimate the center of the cornea sphere from its projection. The second is to use basis vectors to represent the position of the reference points, which enables us to deal with 3D information of reference points compactly. We demonstrate the performance of the proposed method with qualitative and quantitative evaluations using synthesized and real data.

  • PARS Architecture: A Reconfigurable Architecture with Generalized Execution Model--Design and Implementation of Its Prototype Processor

    Kazuya TANIGAWA  Tetsuo HIRONAKA  Akira KOJIMA  Noriyoshi YOSHIDA  

     
    PAPER

      Vol:
    E86-D No:5
      Page(s):
    830-840

    Reconfigurable architectures have been focused for its potential on achieving high performance by reconfiguring special purpose circuits for a target application and its flexibility due to its ability of reconfiguring. We have set our sights on use of a reconfigurable architecture as a general-purpose computer by extending the advantageous properties of the architecture. To achieve the goal, a generalized execution model for reconfigurable architecture is required, so we have proposed an Ideal PARallel Structure (I-PARS) execution model. In the I-PARS execution model, any programs based on its model has no restriction depending on hardware structures based on a specific reconfigurable processor, which makes it easier to develop software. Further, we have proposed a PARS architecture which executes programs based on the I-PARS execution model effectively. The PARS architecture has a large reconfigurable part for highly parallel execution, which utilizes parallelism described on the I-PARS execution model. For effective utilization of the reconfigurable part in the PARS architecture, it has an ability to reconfigure and execute operations simultaneously in one cycle. Further, the PARS architecture supports branch operations to introduce control flow in an execution on the architecture, which makes it possible to skip an execution which does not produce a valid result. In this paper, we introduce the detailed structure of an implemented prototype processor based on the PARS architecture. In the implementation, 420,377 CMOS transistors were used, which was only 3.8% of the number of transistors used in the UltraSPARC-III in logic circuits. Additionally, we evaluated the performance of the prototype processor by using some benchmark programs. From the evaluation results, we found that the prototype processor could achieve nearly the same performance and be implemented with extremely the less number of transistors compared with UltraSPARC-III 750MHz.

  • Implementation of the Multicolored SOR Method on a Vector Supercomputer

    Seiji FUJINO  Ryutaro HIMENO  Akira KOJIMA  Kazuo TERADA  

     
    PAPER

      Vol:
    E80-D No:4
      Page(s):
    518-523

    We describe the implementation of an iterative method with the goal of gaining a long vector length. The strategy for vectorization by means of multipoint stencils used for discretization of the partial differential equations is discussed. Numerical experiments show that the strategy that requires certain restrictions on the number of grid points in the x and y directions improves the performance on the vector supercomputer.