Ikuo Ishii

Development of navigation system for the blind using GPS and mobile phone combination

A single GPS (Global Positioning System) or differential GPS receiver is a useful tool for the blind for determining their location relative to the surrounding environment. However, each person needs to carry his/her own personal computer loaded with location data, and these data have to be updated periodically for each area. We therefore developed a new guidance system to solve these problems by using GPS receivers and a mobile phone. In the experiments on campus, we confirmed the automatic on-line personal guidance function. The maximum error of the determined position was 16 m. The weight of the mobile unit was under 2 kg.

ECG data compression by multiscale peak analysis

The paper presents an ECG data compression technique using multiscale peak analysis. The authors define multiscale peak analysis as the wavelet maxima representation of which the basic wavelet is the second derivative of a symmetric smoothing function. The wavelet transform of an ECG shows maxima at the start, peak and stop points of five transient waves P through T. The number of wavelet maxima is expected to be less than the number of original data samples. The wavelet maxima can be enough to reconstruct original signals precisely. The wavelet maxima representation can lead to ECG data compression and analysis. The compressed data still keep the peaks of QRS waves, and abnormal behavior search will be feasible in practice. The result of the compression shows that a normal ECG data is compressed by a factor 10.

Algorithm for extracting ellipses using weighted center points map

When a group of parallel lines pass through an ellipse, the center point between two intersecting points of each straight line is on another straight line passing through the center of the ellipse. Furthermore, a graphical plot of the distance between the two intersecting points vs. a coordinate value (either x or y) of the center point will form an elliptical shape. These two characteristics of the ellipse are exploited by an algorithm for ellipse extraction. Given an input image of ellipses, a center point map is constructed. Then a Hough transform is used to detect the center line that represents the ellipse. Next, the center line so detected is used to estimate the parameters and to obtain sample pixels of the ellipse. This is followed by a least-square fitting and high precision parameter value computation. Numerous experiments were conducted which demonstrated the effectiveness of our algorithm.

Using infrared-transparent pigments to identify objects

With the goal of developing an invisible code that can be used to identify objects, we have created several pigments for color printing that share the characteristic of being transparent to near-infrared light, along with methods to print them. Our recent research has emphasized applications as we continue to pursue our investigations of the characteristics of these infrared-transparent pigments. In the course of our studies, we have discovered a black pigment with high transparency in the infrared (AM-BK) (Makino, Yamamiya, and colleagues, 1997). This pigment has visible light characteristics that are the same to the naked eye as ordinary pigments, and like these pigments it is “lightfast,” that is, resistant to bleaching by light. For this reason, we anticipate that there will be applications for AM-BK in the so-called “universal design” area, whose goals are to provide information to visually impaired people, to keep track of lost or disoriented elderly people noninvasively, and so on. With this in mind, we have recently attempted to create pigments with colors other than black, and to increase the information density they can encode, so as to extend the range of uses for such pigments. In this article, we describe the optical characteristics of the pigments we have developed, and our efforts to use them in a specific type of invisible code. The inks we used in our code experiments generally were of two types: inks that incorporate carbon black (CB), which absorbs infrared light, and inks that contain AM-BK pigment, which is transparent to infrared light. By mixing these two varieties of inks with solid-color pigments, we were able to make pigments in three visible-light colors—yellow, red, and blue. In an experiment with applications in mind, we then screen-printed a bright yellow lattice-like floral pattern on a T-shirt with a “marker” for identifying an individual—the numbers [911]—hidden in it. Our results confirmed that when these numbers were concealed in the T-shirt pattern by printing them with the above-mentioned IR-transparent pigments AM-BK and CB, a CCD camera was able to distinguish them with ease although they were invisible to the naked eye. These experiments also revealed that as the amount of CB added to the pigment increases, its transparency to near-infrared light falls off exponentially. This shows that it is possible to create gray-scale contrasts, which could be used to encode high-density two-dimensional bar codes.

A synchronization mechanism in networked virtual environment

We describe the design of a group synchronization mechanism for a local area network virtual environment and introduce a step synchronization mechanism. We use a football game to evaluate this mechanism. In this football game, users can share a virtual space where they can move around, dribble and shoot. To achieve synchronization among users, a client of the game exchanges data through a server within a certain period time. A problem of such a system is that all users should share the space in the same time for justice competition. But because of the different capacity of computers and the time cost of the communication between clients, it is difficult for all clients to update the virtual space simultaneously. In our systems, we introduce a waiting time synchronization mechanism. To evaluate our proposed architecture and mechanisms, we make a series of experiments in our local area network and then build and analyse the model of our system.

Approximation method for probability distribution functions using Cox distribution to evaluate multimedia systems

Several probability distribution functions such as exponential distribution function have been used to represent the task arrival process and processing time of tasks for multimedia systems. These distribution functions are simple, memory less, and easy-to-use, however,they are difficult to represent the task arrival process of multimedia stream data or audio data having real-time properties. This paper proposes a method for obtaining approximate probability distribution functions for given task arrival process for multimedia systems by using the Cox distribution function. The Cox distribution function can represent arbitrary distribution functions but their parameters are difficult to be determined for representing the given function. In the method, first, an objective probability distribution function is approximated by a linear combination of exponential distribution functions and Erlan distribution functions, then the parameters of the Cox distribution function is determined from the linear combination of the functions obtained above. The examples of the approximations show that the method is effective for approximating given probability distribution functions.

A method of measuring marker position/orientation for VR interface by monocular image processing

The method of measuring position/orientation in the real world determines the construction of the VR interface. This paper proposes a method of measuring marker position/orientation by image processing. The marker is rectangular. The position/orientation is measured using a single camera. The orientation of the marker is estimated by optimization, utilizing the information of two vanishing points obtained from an image. Then, the position of the marker is determined by calculations. This is facilitated because we have only to attach a marker to a target of measurements. The expansion in the measurement of multiple objects is straightforward and the system can be constructed cheaply because no special circuitry is required. Also, the measurement range is easily modified by resetting the camera lens. The advantage of this method is shown by computer simulations and experimental results using a real image. The real-time measuring accuracy of the system, which was composed of ready-made devices and a highly distorted camera, was 0.5 degrees in directional deviations and 1 mm in depth deviation.

A method of handling virtual objects that incorporates the sense of touch

This study aims at the application of the virtual reality technique to model construction and simulation in industrial design and the arts. This paper discusses several problems in the interactive direct manipulation of the virtual object from the viewpoint of real space. The first point is to realize the representation system which can represent the motion parallax without experiencing the response delay. For this purpose, the reduction of the measurement time for the positions of both eyes is investigated, and the problem is solved by developing the both-eye position measurement method using position-sensitive devices (PSD). The second point is to realize the accurate and direct specification method of manipulation from the real space. The direct specification using the hand or the stylus in the real space makes it difficult to realize an accurate manipulation since the error between the real space and the virtual space coordinates is sensed visually in a direct way. For this problem, a stylus for virtual object manipulation was developed. It has a special structure wherein the grip is in the real space and the pointer is in the virtual space. By this elaboration, the visual error in the position relation between the pointer and the object to be handled can be eliminated. Then the real-time processing is investigated for the decision of contact between the stylus pointer and the virtual object to be manipulated, as well as for the generation of the tactile sensation. The real-time processing is realized by utilizing the feature of the virtual pointer stylus and the drawing mechanism.

3-D object information system for the visually impaired using an infrared reflective bar code

We have produced a 3 dimensional object information system using a newly developed infrared reflection type pigment as an identifier. The system incorporates a video camera, which inputs the object image, a personal computer and speech synthesizer. In experiments, a bar code, using the IR reflection pigment, was attached to the surface of a pillar-shaped can, with the bar code matching the color of the object. The name of the object was then output within 1 second, using the image of the attached bar code. With this system, it is possible to identify objects without contact, and it is also possible to explain the positions of plural components on a table.<<ETX>>

An evaluation method for network systems based on delay jitter analysis

This paper proposes a method for evaluating network systems based on delay-jitter analysis using generalized stochastic Petri nets (GSPN). Systems are modeled by GSPN and tagged client approach. The mean delay time and its variance for systems are calculated by using equations derived from a Markov chain of the GSPN model. Systems can be evaluated statistically by the obtained values.