An innovative small planar packaging(SPP)system is described that can be combined with card-on-board(COB)packaging in high-speed asynchronous transfer mode switching systems with throughput of over 40-Gb/s. The SPP system provides high I/O pin count density and high packaging density, combining the advantages of both planar packaging used in computer systems and COB packaging used in telecommunication systems. Using a newly developed quasi-coaxial zero-insertion-force connector, point-to-point 311 Mb/s of 8-bit parallel signal transmission is achieved in an arbitrary location on the SPP systems shelf. Also about 5400 I/O connections in the region of the planar packaging system are made, thus the SPP system effectively eliminates the I/O pin count limitation. Furthermore, the heat flux management capability of the SPP system is five times higher than of conventional COB packaging because of its air flow control structure. An SPP system can easily enlarge the switch throughput and it will be useful for future high-speed, high-throughput ATM switching systems.

The small planar packaging (SPP) system described here can be combined with card-on-board (COB) packaging in high-speed asynchronous transfer mode (ATM) switching systems with throughput of over 40-Gb/s. The SPP system provides high I/O pin count density, high packaging density and high cooling capability. Prototype SPP system with air flow control structure for switching MCMs is constructed. Each MCM contained a 35 array of low thermal resistance butt-lead pin-grid-array on a glass ceramic substrate measuring 100170 mm with a plate fin heat-sink. This allows a power dissipation of more than 125 W per MCM, and 300 W per printed circuit board (PCB). Obtained board level heat flux density of the SPP system is 0. 37 W/cm2, which is six times that of conventional COB packaging. The SPP system combined with the COB packaging provides a small system foot-print and compact hardware for high-speed, large capacity ATM switching systems. This high-performance air cooling technology will be especially useful for future broadband ISDN high-speed switching systems.

In live multimedia applications with multiple videos, it is necessary to develop an efficient mechanism of multiplexing several MPEG video streams into a single stream and transmitting it over network without wasting excessive bandwidth. In this paper, we present an efficient multiplexing and traffic smoothing scheme for multiple variable bit rate (VBR) MPEG video streams in live video applications with finite buffer sizes. First, we describe the constraints imposed by the allowable delay bound for each elementary stream and by the multiplexer/receiver buffer sizes. Based on these constraints, a new multiplexing and traffic smoothing scheme is designed in such a way as to smooth maximally the multiplexed transmission rate by exploiting temporal and spatial averaging effects, while avoiding the buffer overflow and underflow. Through computer experiments based on an MPEG-coded video trace of Star-wars, it is shown that the proposed scheme significantly reduces the peak rate, coefficient of variation, and effective bandwidth of the multiplexed transmission rate.

Penumbral imaging is a technique which uses the facts that spatial information can be recovered from the shadow or penumbra that an unknown source casts through a simple large circular aperture. The technique is based on a linear deconvolution. In this paper, a two-step method is proposed for decoding penumbral images. First a local-statistic filter based on adaptive windowing is applied to smooth the noise; then, followed by the conventional linear deconvolution. The simulation results show that the reconstructed image is dramatically improved in comparison to that without the noise-smoothing filtering, and the proposed method is also applied to real experimental X-ray imaging.

The development of a far-infrared imaging system based on ultrafast THz time-domain spectroscopy has opened a new field of applications of femtosecond technology. We describe the principle of this new imaging technique and report recent progress to augment the possibilities of "T-ray" imaging. These include sub-wavelength-resolution near-field imaging and three-dimensional tomographic reconstruction of a samples refractive index profile.

We describe an algorithm for efficiently compositing partial images generated during parallel volume rendering on a distributed memory parallel computer. In this object space partitioning algorithm, each PE is assigned to several subvolumes where each subvolume has a corresponding local frame buffer. After volume rendering is performed independently for each subvolume, the partial images stored in the local frame buffers are combined to generate a complete image. During this compositing process, the communication of partial image data between the PEs is kept minimal by assigning PEs to subvolumes in an interleaved manner. This assignment makes possible a reduction in communication in the axis direction in which there is the most communication. Experimental results indicate that a 9% to 35% reduction in the total rendering time can be attained with no additional data structures and no memory overhead.

A rigorous analysis of coupling between two twin-slot antennas using the Finite Difference Time Domain (FDTD) method is reported for the first time. The Phase Cancellation Effect (PGE) is used to reduce the coupling due to the TM0 surface wave mode between the Coplanar Waveguide (CPW) fed cascade-connected twin-slot antennas. To confirm the effectiveness of this approach, coupling between single-slot and twin-slot elements separated by λ0/2 was analysed. The coupling between the two single-slot antennas was S21 = -30.2 dB. For the case of two twin-slot antennas, the coupling was found to be -37.8 dB, 7.6 dB below that of the single-slot antennas. The phase cancellation effect of surface waves is significant in reducing coupling between two twin-slot antennas, in addition to minimising power loss into substrate modes. A memory optimised implementation of the FDTD method with the Berenger Perfectly Matched Layer (PML) Absorbing Boundary Condition (ABC) was used for the numerical analysis.

This paper deals with two different quantitative inversion algorithms for reconstructing the complex permittivity profile of bounded inhomogeneous objects from measured scattered field data. The first algorithm involves an imaging method with single frequency excitation and multiincidence illumination and the second algorithm involves a method with synthetic pulse (multifrequency mode) excitation for objects surrounded by freespace or buried in stratified half-space media. Transmission or reflection imaging protocols are considered depending on aimed applications: microwave imaging in free-space from far-field data for target identification, microwave imaging from near-field data for nondestructive testing (NDT), microwave tomography of buried objects for mine detection and localization, civil engineering and geophysical applications. And Edge-Preserving regularization scheme leading to a significant enhancement in the image reconstructions is also proposed. The methods are illustrated with synthetic and experimental data.

This paper describes a novel image reconstruction algorithm and experimental results of a 3-dimensional acoustical holographic imaging system which has a limited number of transducers distributed sparsely. The proposed algorithm is based on the conjugate gradient projection onto convex sets (CGPOCS), which allows the addition of convex sets constrained by a priori information to reduce ambiguity and extract resolution iteratively. By several experiments, it is proven that the concept of the new 3-D acoustic image reconstruction algorithm has following improvements:1. the artifacts caused by the spurious lobes can be reduced under the condition that the inter-spacing of elements is larger than the wave length,2. the instability caused by the lack of information about the actual point spread function (PSF) can be reduced,3. the actual PSF can be estimated concurrently with during the image reconstruction process.

MPO optical backplane connectors using multi-fiber push-on plugs (MPO plugs) have been developed. MPO optical backplane connector is a connector connecting a printed board to a backplane using MPO plug. MPO plug is held in the housing with self-retentive mechanism. To get same optical performances as standard MPO connector, precision in dimension and mechanism for appropriate connecting-disconnecting sequence are necessary. We have developed a new backplane housing and printed board housing based on previously reported MU connector. The optical performance is similar to that of MPO connectors.

A quantitative study is made on performance of neutron penumbral imaging with a toroidal-segment aperture, and it focused on isoplanaticity of aperture point spread function and effect of the non-isoplanaticity on the reconstructed images. The results show that the aperture point spread function is satisfactorily isoplanatic for a small field of view, while for a large field of view the point spread function is not satisfactorily isoplanatic resulting in some distortion in the reconstructed image and reduction of resolution.

This paper describes packaging techniques based on a novel passive alignment technique as key techniques for module assembly. A laser diode (LD) is passively positioned by detecting a pair of alignment marks located on the LD and Si substrate. A single-mode fiber is self aligned on a Si V groove. A simple receptacle structure for the module output port is also newly designed. This structure is more suitable for the automatic assembly line as well as the module mounting process on circuit board. In this paper, an advanced module applications such as a hybrid integrated wave guide module and a surface mountable (SMT) LD module is introduced.

We introduce a new type of optical microconnector named "put-in microconnector-" using a planar microlens. The connector part is composed by a lens jack and fiber plug, where the lens jack is a hollow formed on a planar microlens surface, and the fiber plug is a protuberance formed on the core of an optical fiber. This concept can realize an alignment-free single mode fiber coupling. In this paper, we describe the structure and fabrication process, the optical coupling characteristics of the fabricated device, and finally, the basic analysis of optical coupling module. For the optical coupling characteristics, we measured the coupling loss and the return loss. The optical coupling loss of about 4 dB and the return loss of about 49 dB were obtained at wavelength of λ = 0.633 µm. Moreover, we have confirmed that the insertion loss of such a structure does not increase so much in comparison with that of the butt jointing. For the purpose of characterizing the optical property, the theoretical analysis was performed. We have made a software tool to estimate the optical coupling loss due to the position error. For this type of structure, the tolerance of about 15 µm for the distance between the laser and the planar microlens and 150 µm for the distance between the planar microlens and the optical fiber were estimated. Since the put-in microconnector does not require any precise alignment, it is appropriate for mass production.

At present, the widespread use of optoelectronic components is restricted by their high cost. Up to 90% of the cost of a semiconductor laser is in the packaging, with the fibre-chip alignment the major part. In this paper, an approach to low cost packaging is described, which uses an integrated mode size transformer to match the laser output to the fibre mode. This improves the alignment tolerance of the laser-fibre coupling by more than a factor of three, allowing simple passive alignment approaches to be used. It requires only minor modification to the processing of a standard buried heterostructure laser, and allows the coupling efficiency to be optimised without compromising the performance of the laser. The design of a silicon submount for passive laser-fibre alignment is described and coupling losses as low as 1.2 dB to standard cleaved single mode fibre are reported. The technology that has been developed is generic and its successful application to other optoelectronic devices such as fibre grating lasers, semiconductor optical amplifiers and laser arrays is described.

We present a volume rendering algorithm which renders images at approximately two to seven times the speed of a conventional ray caster with almost no visible loss of image quality. This algorithm traverses the volume data in object order and renders the image by performing ray casting for the pixels within the footprint of the voxel (i.e., rectangular prism) being processed. The proposed algorithm supports the rendering of both single and multiple isosurfaces with arbitrary opacity values. While the projection approach to volume rendering is not new, we present an algorithm specifically designed for the perspective projection, evaluate its rendering speed for both single and multiple isosurfaces with arbitrary opacity values, and examine how efficiently it uses cache memory.

We have developed a neutron imaging system based on the penumbral imaging technique. The system consists of a penumbral aperture and a sensitive neutron detector. The aperture was made from a thick (6 cm) tungsten block with a toroidal taper. It can effectively block 14-MeV neutrons and provide a satisfactory sharp, isoplanatic (space-invariant) point spread function (PSF). A two-dimensional scintillator array, which is coupled with a gated two-stage image intensifier system and a CCD camera, was used as a sensitive neutron detector. It can record the neutron image with high sensitivity and high signal-to-noise ratio. The reconstruction was performed with a Wiener filter. The spatial resolution of the reconstructed neutron image was estimated to be 31 µm by computer simulation. Experimental demonstration has been achieved by imaging 14-MeV deuterium-tritium neutrons emitted from a laser-imploded target.

Signal processing antennas have been studied not only for interference suppression but also for high-resolution estimation of radio environment such as directions-of-arrival of incident signals. These two applications are based on the common technique, that is, null steering. This tutorial paper reviews the MUSIC algorithm which is one of the typical high-resolution techniques. Examining the eigenvector beam patterns, we demonstrate that the high-resolution capability is realized by steering nulls. The considerations will be useful for understanding the high-resolution techniques in the signal processing antennas. We then describe a modified version of MUSIC (Root MUSIC). We show the performance and robustness of the method. Furthermore, we introduce radar target identification and two-dimensional radar target imaging. These study fields are new applications of the signal processing antennas, to which a great deal of attention has been devoted recently.

Three-dimensional vocal tract shapes of a male, a female and a child subjects are measured from magnetic resonance (MR) images during sustained phonation of Japanese vowels /a, i, u, e, o/. Non-uniform dimensional differences in the vocal tract shapes of the subjects are quantitatively measured. Vocal tract area functions of the female and child subjects are normalized to those of the male on the basis of non-uniform and uniform scalings of the vocal tract length and compared with each other. A comparison is also made between the formant frequencies computed from the area functions normalized by the two different scalings. It is suggested by the comparisons that non-uniformity in the vocal tract dimensions is not essential in the normalization of the five Japanese vowels.

This paper describes the imaging method for a human forearm in the microwave transmission CT at 3GHz. To improve the spatial resolution, the correction method of the diffraction effects is adopted and the high directivity antennas are used. A cross-sectional image of the human forearm is obtained in vivo.

MRI is a widely used diagnostic imaging modality because it has excellent diagnostic capabilities, is safe to use and generates images not affected by bone artifacts. Images are obtained by utilizing the phenomenon of Nuclear Magnetic Resonance (NMR) by which protons located in a static magnetic field absorb radiofrequency (RF) pulses with a specific frequency and release a part of the energy as a NMR signal. Potentially MRI has the ability to provide functional and metabolic information (such as flow, temperature, diffusion, neuron activity) in addition to morphological information. This paper describes the imaging principles and provides a general outline of some applications: flow imaging, metabolite imaging and temperature imaging.