Acquisition of three-dimensional information of a real-world scene from two-dimensional images has been one of the most important issues in computer vision and image understanding in the last two decades. Noncontact range acquisition techniques can be essentially classified into two classes: Passive and active. This paper concentrates on passive depth extraction techniques which have the advantage that 3-D information can be obtained without affecting the scene. Passive range sensing techniques are often referred to as shape-from-x, where x is one of visual cues such as shading, texture, contour, focus, stereo, and motion. These techniques produce 2.5-D representations of visible surfaces. This survey discusses aspects of this research field and reviews some recent advances including video-rate range imaging sensors as well as emerging themes and applications.

The goal of this paper is to present a critical survey of existing literature on an omnidirectional sensing. The area of vision application such as autonomous robot navigation, telepresence and virtual reality is expanding by use of a camera with a wide angle of view. In particular, a real-time omnidirectional camera with a single center of projection is suitable for analyzing and monitoring, because we can easily generate any desired image projected on any designated image plane, such as a pure perspective image or a panoramic image, from the omnidirectional input image. In this paper, I review designs and principles of existing omnidirectional cameras, which can acquire an omnidirectional (360 degrees) field of view, and their applications in fields of autonomous robot navigation, telepresence, remote surveillance and virtual reality.

Computational sensor (smart sensor, vision chip in other words) is a very small integrated system, in which processing and sensing are unified on a single VLSI chip. It is designed for a specific targeted application. Research activities of computational sensor are described in this paper. There have been quite a few proposals and implementations in computational sensors. Firstly, their approaches are summarized from several points of view, such as advantage vs. disadvantage, neural vs. functional, architecture, analog vs. digital, local vs. global processing, imaging vs. processing, new processing paradigms. Then, several examples are introduced which are spatial processings, temporal processings, A/D conversions, programmable computational sensors. Finally, the paper is concluded.

Phase performance in a fiber optic temperature sensor using a mode-division multiplex is studied. The phase shift due to the temperature change of a multimode graded-index optical fiber is analyzed. The intensity fluctuation by the interference of two modes is estimated in computer simulation.

This paper proposes a medium access control (MAC) protocol for single-hop WDM star-coupler networks, in which the number of stations is larger than the number of channels and the stations have arbitrary distances to the star coupler. The proposed protocol has one control channel for reserving the slots of data channels and several data channels which are used to transmit traffic. This paper also suggests a scheme that accomplishes load balancing among data channels for arbitrary traffic patterns between stations. Since this load balancing scheme diminishes an influence that traffic patterns have on the performance of the proposed MAC protocol, the proposed system is appropriate for systems which have asymmetric traffic intensity between stations. Throughput and mean message delay of the MAC protocol are analyzed using a discrete time Markov process and a D/G/1 queue with batch arrivals. The numerical results show that the performance is improved as the message length increases, the maximum round-trip propagation delay decreases, and the number of data channels increases.

There are two dynamics issues in vision chips: (i) The temporal dynamics issue due to the parasitic capacitors in a CMOS chip, and (ii) the spatial dynamics issue due to the regular array of processing elements in a chip. These issues are discussed in [1]-[3] for the resistor network with only associated parasitic capacitances. However, in this paper we consider also parasitic inductances as well as parasitic capacitances for a more precise network dynamics model. We show that in some cases the temporal stability condition for the network with parasitic inductances and capacitances is equivalent to that for the network with only parasitic capacitances, but in general they are not equivalent. We also show that the spatial stability conditions are equivalent in both cases.

In this paper, the authors present general views of computer vision and image processing based on optimization. Relaxation and regularization in both broad and narrow senses are used in various fields and problems of computer vision and image processing, and they are currently being combined with general-purpose optimization algorithms. The principle and case examples of relaxation and regularization are discussed; the application of optimization to shape description that is a particularly important problem in the field is described; and the use of a genetic algorithm (GA) as a method of optimization is introduced.

The tera-bit order capacity of ultrahigh-speed and wide-band networks will become necessary to provide highly advanced multimedia services. In conventional networks, electronic circuits limit the speed capability of the networks. Consequently, all-optical networks are essential to realize ultrahigh-speed and wide-band communications. In this paper, we propose the configuration of an all-optical code division multiplexing (CDM) switching network based on self-routing principles and the structure of a nonlinear all-optical switching device as one of the key components for the network. We show that the required performances of the optical devices used in the CDM switching fabric are lower than those used in the TDM and illustrate the basic transmission characteristics of the switching device utilizing FD-BPM. To evaluate the multiplexing performance, we demonstrate the maximum number of channels under an error-free condition and the BER characteristics when the Gold sequence is applied as one of the CDM code sets, and show that the network of the sub-tera-bit order capacity is realizable by adopting TDM, WDM and CDM technologies. We also illustrate the packet assembly method suitable for self-routing transmissions and one of network architectures where the proposed switching fabric can be exploited.

Wavelength division multiplex (WDM) photonic networks are expected as the key for the global communication infrastructure. Recent increase of communication demands require large-scale highly-dense WDM systems, which results in severe requirements for optical cross-connect systems, such as cross-talk specification. In this paper, we propose a new optical path cross-connect system (OPXC) using matrix-WDM scheme, which makes it possible to reduce cross-talk requirements of WDM filters and to construct OPXC in modular structures. The matrix-WDM scheme is a concept of two-layered optical paths, which provides wavelength group managements in the fiber dispersion equalization and EDFA gain equalization.

Wavelength Division Multiplex (WDM) photonic networks are expected as key for global communication infrastructure. The accurate measurement methods for AWG-MUX/DMUX are desirable for WDM network design. We measured a transfer function matrix of an AWG-MUX to find that polarization mode dispersion (PMD) and polarization dependent loss (PDL) shows the bandpass characteristics, which may limit the maximum size and the bit rate of the system. These bandpass characteristics of PMD and PDL are reproduced by a simple AWG-MUX model: The phase constant difference of 0.5% between orthogonal modes in arrayed waveguides is sufficient to obtain the measured passband characteristics of PMD and PDL. We find phase distribution difference between two orthogonal modes in the arrayed waveguide grating gives arise to complex PMD.

Recent work in the area of ultrafast optical time-division multiplexed (OTDM) networking at MIT Lincoln Laboratory is presented. A scalable helical local area network or HLAN architecture, presented elsewhere as an architecture well-suited to ultrafast OTDM LANs and MANs, is considered in the context of wide area networking. Two issues arise in scaling HLAN to the wide area. The first is protocol extension, and the second is supporting the required bandwidth on the long-haul links. In this paper we discuss these challenges and describe progress made in both architecture and technologies required for scaling HLAN to the wide area.

Recent work in the area of ultrafast optical time-division multiplexed (OTDM) networking at MIT Lincoln Laboratory is presented. A scalable helical local area network or HLAN architecture, presented elsewhere as an architecture well-suited to ultrafast OTDM LANs and MANs, is considered in the context of wide area networking. Two issues arise in scaling HLAN to the wide area. The first is protocol extension, and the second is supporting the required bandwidth on the long-haul links. In this paper we discuss these challenges and describe progress made in both architecture and technologies required for scaling HLAN to the wide area.

A 116 arrayed waveguide grating multiplexer operating around 1550 nm has been realized using newly synthesized fluorinated poly(arylene ethers). The channel spacing is 0.8 nm (100 GHz). The insertion loss of the multiplexer is 17-20 dB and the cross talk is less than -15 dB. The propagation loss of a rib waveguide is less than 0.5 dB/cm at 1550 nm.

Divisor-Skip Wavelength Division Multiplexing (DS-WDM) ring is an optical interconnection network for workstation clusters or parallel machines which can connect various number of nodes easily using wavelength division multiplexing techniques. However, the wavelength-ordered routing algorithm proposed for the DS-WDM ring requires complicated processes in each router. Here, a new routing algorithm called the comparing dimensional number routing algorithm for the DS-WDM ring is proposed and evaluated. Although the diameter and average distance are almost same as traditional wavelength-ordered routing, the cost and latency are much reduced.

Wavelength Division Multiplex (WDM) photonic networks are expected as key for global communication infrastructure. The accurate measurement methods for AWG-MUX/DMUX are desirable for WDM network design. We measured a transfer function matrix of an AWG-MUX to find that polarization mode dispersion (PMD) and polarization dependent loss (PDL) shows the bandpass characteristics, which may limit the maximum size and the bit rate of the system. These bandpass characteristics of PMD and PDL are reproduced by a simple AWG-MUX model: The phase constant difference of 0.5% between orthogonal modes in arrayed waveguides is sufficient to obtain the measured passband characteristics of PMD and PDL. We find phase distribution difference between two orthogonal modes in the arrayed waveguide grating gives arise to complex PMD.

A 116 arrayed waveguide grating multiplexer operating around 1550 nm has been realized using newly synthesized fluorinated poly(arylene ethers). The channel spacing is 0.8 nm (100 GHz). The insertion loss of the multiplexer is 17-20 dB and the cross talk is less than -15 dB. The propagation loss of a rib waveguide is less than 0.5 dB/cm at 1550 nm.

Wavelength division multiplex (WDM) photonic networks are expected as the key for the global communication infrastructure. Recent increase of communication demands require large-scale highly-dense WDM systems, which results in severe requirements for optical cross-connect systems, such as cross-talk specification. In this paper, we propose a new optical path cross-connect system (OPXC) using matrix-WDM scheme, which makes it possible to reduce cross-talk requirements of WDM filters and to construct OPXC in modular structures. The matrix-WDM scheme is a concept of two-layered optical paths, which provides wavelength group managements in the fiber dispersion equalization and EDFA gain equalization.

The tera-bit order capacity of ultrahigh-speed and wide-band networks will become necessary to provide highly advanced multimedia services. In conventional networks, electronic circuits limit the speed capability of the networks. Consequently, all-optical networks are essential to realize ultrahigh-speed and wide-band communications. In this paper, we propose the configuration of an all-optical code division multiplexing (CDM) switching network based on self-routing principles and the structure of a nonlinear all-optical switching device as one of the key components for the network. We show that the required performances of the optical devices used in the CDM switching fabric are lower than those used in the TDM and illustrate the basic transmission characteristics of the switching device utilizing FD-BPM. To evaluate the multiplexing performance, we demonstrate the maximum number of channels under an error-free condition and the BER characteristics when the Gold sequence is applied as one of the CDM code sets, and show that the network of the sub-tera-bit order capacity is realizable by adopting TDM, WDM and CDM technologies. We also illustrate the packet assembly method suitable for self-routing transmissions and one of network architectures where the proposed switching fabric can be exploited.

Three multiplicative algorithms for the floating-point divide operation are compared: the Newton-Raphson method, Goldschmidt's algorithm, and a naive method that simply calculates a form of the Taylor series expansion of a reciprocal. The series also provides a theoretical basis for Goldschmidt's algorithm. It is well known that, of the Newton-Raphson method and Goldschmidt's algorithm, the former is the more accurate while the latter is the faster on a pipelined unit. However, little is reported about the naive method. In this report, we analyze the speed and accuracy of each method and present the results of numerical tests, which we conducted to confirm the validity of the accuracy analysis. Basically, the comparison are made in the context of software implementation (e. g. , a macro library) and compliance with the IEEE Standard 754 rounding is not considered. It is shown that the naive method is useful in a realistic setting where the number of iterations is small and the method is implemented on a pipelined floating-point unit with a multiply-accumulate configuration. In such a situation, the naive method gives a more accurate result with a slightly lower latency, as compared with Goldschmidt's algorithm, and is much faster than but slightly inferior in accuracy to the Newton-Raphson method.

This study presents a method that can be used to manage individual pieces of information in large scale distributed geographic information systems (GIS). In a distributed GIS, ordinary users usually cannot alter any of the contents on the server. The method in this study can be used to alter the content or add individual datums onto these types of non-write-permitted data sets. The authors have called it a 'Geographic Differential Script File' (GDSF). A client creates a GDSF, which contains private information that is to be added onto the served data. The client keeps this file on a local disk. When the user employs the data, he applies the differential script sequence onto the downloaded data in order to retrieve the information. GDSF is a collection of graphic operation commands which insert and delete objects as well as modify operations. GDSF also contains modifications of the attribute information of geographic entities. This method can also be used to revise information that is published on ROM media, e. g. CD-ROM or DVD-ROM, as well as in a distributed environment. In this paper, the method and results of applying it are presented.