Toshiaki Fujii

Bio: Toshiaki Fujii is an academic researcher from Nagoya University. The author has contributed to research in topics: Visible light communication & Interpolation. The author has an hindex of 30, co-authored 266 publications receiving 4281 citations. Previous affiliations of Toshiaki Fujii include Tokyo Institute of Technology & University of Tokyo.

Image-sensor-based visible light communication for automotive applications

Abstract: The present article introduces VLC for automotive applications using an image sensor. In particular, V2I-VLC and V2V-VLC are presented. While previous studies have documented the effectiveness of V2I and V2V communication using radio technology in terms of improving automotive safety, in the present article, we identify characteristics unique to image-sensor-based VLC as compared to radio wave technology. The two primary advantages of a VLC system are its line-of-sight feature and an image sensor that not only provides VLC functions, but also the potential vehicle safety applications made possible by image and video processing. Herein, we present two ongoing image-sensor-based V2I-VLC and V2VVLC projects. In the first, a transmitter using an LED array (which is assumed to be an LED traffic light) and a receiver using a high-framerate CMOS image sensor camera is introduced as a potential V2I-VLC system. For this system, real-time transmission of the audio signal has been confirmed through a field trial. In the second project, we introduce a newly developed CMOS image sensor capable of receiving highspeed optical signals and demonstrate its effectiveness through a V2V communication field trial. In experiments, due to the high-speed signal reception capability of the camera receiver using the developed image sensor, a data transmission rate of 10 Mb/s has been achieved, and image (320 × 240, color) reception has been confirmed together with simultaneous reception of various internal vehicle data, such as vehicle ID and speed.

View generation with 3D warping using depth information for FTV

Abstract: In this paper, we propose a new method of depth-image-based rendering (DIBR) for free-viewpoint TV (FTV). In the conventional method, we estimated the depth of an object on the virtual image plane, which is called view-dependent depth estimation, and the virtual view images are rendered using the view-dependent depth map. In this method, virtual viewpoint images are rendered with 3D warping instead of estimating the view-dependent depth, since depth estimation is usually costly and it is desirable to eliminate it from the rendering process. However, 3D warping causes some problems that do not occur in the method with view-dependent depth estimation; for example, the appearance of holes on the rendered image, and the occurrence of depth discontinuity on the surface of the object at virtual image plane. Depth discontinuity causes artifacts on the rendered image. In this paper, these problems are solved by projecting depth map to the virtual image plane and performing post-filtering on the projected depth map. In the experiments, high-quality arbitrary viewpoint images were obtained by rendering images from relatively small number of cameras.

Free-Viewpoint TV

Abstract: Free-viewpoint television (FTV) is an innovative visual media that enables us to view a three-dimensional (3-D) scene by freely changing our viewpoints. We proposed the concept of FTV and constructed the world???s first real-time system including the complete chain of operation from image capture to display. We also carried out the FTV on a single personal computer (PC) and a mobile player. FTV is based on the ray-space method that represents one ray in real space with one point in the ray-space. We have developed several types of ray capture systems and interfaces such as a 360° capture/ray-reproducing display. FTV is regarded as the ultimate 3DTV, since it can generate infinite number of views. Thus, FTV is the key to immersive communication. Regarding FTV as the most challenging 3-D media, the Motion Picture Experts Group (MPEG) has been conducting its international standardization activities. This article reviews FTV and its related technologies.

View Generation with 3D Warping Using Depth Information for FTV

Abstract: Free viewpoint images can be generated from multi-view images using Ray-Space method. Ray-Space data requires ray interpolation so as to satisfy the plenoptic function. Ray interpolation is realized by estimating view-dependent depth. Depth estimation is usually costly process, thus it is desirable that this process is skipped from rendering process to achieve real-time rendering. This paper proposes a method to render a novel view image using multi-view images and depth maps which are computed in advance. Virtual viewpoint image is generated by 3D warping, which causes some problems that have not occurred in the method with view dependent depth estimation. We handled these problems by projecting depth map to virtual image plane first and perform post-filtering on the projected depth map. We succeeded in obtaining high quality arbitrary viewpoint images from relatively small number of cameras.

A New Automotive VLC System Using Optical Communication Image Sensor

Abstract: As a new technology for next-generation vehicle-to-everything (V2X) communication, visible-light communication (VLC) using light-emitting diode (LED) transmitters and camera receivers has been energetically studied. Toward the future in which vehicles are connected anytime and anywhere by optical signals, the cutting-edge camera receiver employing a special CMOS image sensor, i.e., the optical communication image sensor (OCI), has been prototyped, and an optical V2V communication system applying this OCI-based camera receiver has already demonstrated 10-Mb/s optical signal transmission between real vehicles during outside driving. In this paper, to reach a transmission performance of 54 Mb/s, which is standardized as the maximum data rate in IEEE 802.11p for V2X communication, a more advanced OCI-based automotive VLC system is described. By introducing optical orthogonal frequency-division multiplexing (optical-OFDM), the new system achieves a more than fivefold higher data rate. Additionally, the frequency response characteristics and circuit noise of the OCI are closely analyzed and taken into account in the signal design. Furthermore, the forward-current limitation of an actual LED is also considered for long operational reliability, i.e., the LED is not operated in overdrive. Bit-error-rate experiments verify a system performance of 45 Mb/s without bit errors and 55 Mb/s with $\text{BER}\ .

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Visible Light Communication, Networking, and Sensing: A Survey, Potential and Challenges

Abstract: The solid-state lighting is revolutionizing the indoor illumination. Current incandescent and fluorescent lamps are being replaced by the LEDs at a rapid pace. Apart from extremely high energy efficiency, the LEDs have other advantages such as longer lifespan, lower heat generation, and improved color rendering without using harmful chemicals. One additional benefit of LEDs is that they are capable of switching to different light intensity at a very fast rate. This functionality has given rise to a novel communication technology (known as visible light communication—VLC) where LED luminaires can be used for high speed data transfer. This survey provides a technology overview and review of existing literature of visible light communication and sensing. This paper provides a detailed survey of 1) visible light communication system and characteristics of its various components such as transmitter and receiver; 2) physical layer properties of visible light communication channel, modulation methods, and MIMO techniques; 3) medium access techniques; 4) system design and programmable platforms; and 5) visible light sensing and application such as indoor localization, gesture recognition, screen-camera communication, and vehicular networking. We also outline important challenges that need to be addressed in order to design high-speed mobile networks using visible light communication.

Connected Vehicles: Solutions and Challenges

Abstract: Providing various wireless connectivities for vehicles enables the communication between vehicles and their internal and external environments. Such a connected vehicle solution is expected to be the next frontier for automotive revolution and the key to the evolution to next generation intelligent transportation systems (ITSs). Moreover, connected vehicles are also the building blocks of emerging Internet of Vehicles (IoV). Extensive research activities and numerous industrial initiatives have paved the way for the coming era of connected vehicles. In this paper, we focus on wireless technologies and potential challenges to provide vehicle-to-x connectivity. In particular, we discuss the challenges and review the state-of-the-art wireless solutions for vehicle-to-sensor, vehicle-to-vehicle, vehicle-to-Internet, and vehicle-to-road infrastructure connectivities. We also identify future research issues for building connected vehicles.

LED Based Indoor Visible Light Communications: State of the Art

Abstract: Visible Light Communication (VLC) is an emerging field in Optical Wireless Communication (OWC) which utilizes the superior modulation bandwidth of Light Emitting Diodes (LEDs) to transmit data. In modern day communication systems, the most popular frequency band is Radio Frequency (RF) mainly due to little interference and good coverage. However, the rapidly dwindling RF spectrum along with increasing wireless network traffic has substantiated the need for greater bandwidth and spectral relief. By combining illumination and communication, VLC provides ubiquitous communication while addressing the shortfalls and limitations of RF communication. This paper provides a comprehensive survey on VLC with an emphasis on challenges faced in indoor applications over the period 1979–2014. VLC is compared with infrared (IR) and RF systems and the necessity for using this beneficial technology in communication systems is justified. The advantages of LEDs compared to traditional lighting technologies are discussed and comparison is done between different types of LEDs currently available. Modulation schemes and dimming techniques for indoor VLC are discussed in detail. Methods needed to improve VLC system performance such as filtering, equalization, compensation, and beamforming are also presented. The recent progress made by various research groups in this field is discussed along with the possible applications of this technology. Finally, the limitations of VLC as well as the probable future directions are presented.