Toshihiko Morita

A sequential factorization method for recovering shape and motion from image streams

We present a sequential factorization method for recovering the three-dimensional shape of an object and the motion of the camera from a sequence of images, using tracked features. The factorization method originally proposed by Tomasi and Kanade (1992) produces robust and accurate results incorporating the singular value decomposition. However, it is still difficult to apply the method to real-time applications, since it is based on a batch-type operation and the cost of the singular value decomposition is large. We develop the factorization method into a sequential method by regarding the feature positions as a vector time series. The new method produces estimates of shape and motion at each frame. The singular value decomposition is replaced with an updating computation of only three dominant eigenvectors, which can be performed in O(P/sup 2/) time, while the complete singular value decomposition requires O(FP/sup 2/) operations for an F/spl times/P matrix. Also, the method is able to handle infinite sequences, since it does not store any increasingly large matrices. Experiments using synthetic and real images illustrate that the method has nearly the same accuracy and robustness as the original method.

ECC-less LDPC coding for magnetic recording channels

Summary form only given. Low-density parity check (LDPC) codes are receiving considerable attention as a next-generation coding technique for magnetic recording channels, because they show a 5 dB gain over the conventional PRML method. The gain, however, reduces to 1-1.5 dB if the code is combined with an error correcting code (ECC). After the LDPC code, the ECC is not effective in the sense that its gain is less than the rate loss. In fact, we found that ECC-less LDPC codes perform better than LDPC codes with ECC. However, it is still difficult to avoid use of the ECC since the iterative decoder is unable to correct erasures caused by thermal asperity (TA) or media defects. This paper presents a method of erasure compensation for the iterative decoder. The method enables the use of ECC-less LDPC codes, which leads to better performance than using LDPC codes with ECC.

Design and implementation of high-speed visual tracking system for real-time motion analysis

This paper describes the design and the implementation of a high-speed visual tracking system based on local correlation matching. The system consists of only two PC board modules, which conform to VME bus specifications. The video module is used to input and output video signals, while the tracking module is used to perform visual tracking with the local correlation method. The tracking module contains three frame memories, an image flow controller, a DMA controller for image data transfer, and a dedicated LSI to perform the correlation matching of 8-bit gray-scale images. The processing time is 110 microseconds for an 8/spl times/8 pixel template and 290 microseconds for a 16/spl times/16 pixel template. This paper also describes some of our experimental implementations, including human tracking, recognition of hand movements and signs, and traffic monitoring. Compared to conventional general-purpose image processing systems, our hardware system is compact and inexpensive. This high-performance system can be used for a wide variety of motion analysis applications.

Efficiency of short LDPC codes combined with long Reed-Solomon codes for magnetic recording channels

This paper proposes the use of low-density parity check (LDPC) codes with short block lengths such as 1-K bits for magnetic recording. In general, there is a degradation in bit error rate as the block length of the LDPC codes decreases. Yet, we show that short LDPC codes do not suffer from degraded sector-error-rate performance if the sector size is 32 K bits and if long Reed-Solomon codes over GF(2/sup 12/) are used. This is due to the unique error distribution of iterative decoding. Shorter codes significantly reduce the amount of buffer memory in the iterative decoder and make hardware implementation more feasible.

Structured LDPC Codes With Reversed MTR/ECC for Magnetic Recording Channels

We propose a system for magnetic recording channels where we use a novel structured low-density parity-check (LDPC) code, called a random interleaved array (RIA) code, combined with a reversed maximum-transition run code/error-correction code. Simulation results show that the RIA code provides a significantly better error-rate floor performance than the conventionally structured LDPC code when applied to perpendicular magnetic recording channels. They also show that the system can achieve a 1.2-dB gain at a sector error rate of 10-5 compared with a PRML system combined with a high-rate run-length-limited code

Tracking Vision System for Real-Time Motion Analysis

This paper describes a high-speed motion tracking system based on full-search correlation matching. Incorporating the Advanced Correlation Processor, which computes more than 500 motion vectors per frame, the system enables the detection and tracking of moving objects at a video rate. The system is implemented on a single board and can be mounted inside a PC. Thus, it is compact and economical, and is well suited for a wide variety of applications such as automatic surveillance, traffic monitoring and sports play analysis.

Wrist-mounted laser rangefinder

The authors developed a small, lightweight rangefinder system which can be mounted on the wrist of a robot. Ranging takes place using a binary-coded projection method based on the principle of triangulation. The head of the range finger comprises a multi-slit projector with an infrared semiconductor laser, a nematic-cholesteric phase-transition (NCPT) liquid crystal shutter, and a small CCD camera. A head size of 170 mm/spl times/80 mm/spl times/50 mm and a weight of 230 grams were achieved. A dedicated image processor was developed to speed up range data generation. The time required to produce a range image is about 0.5 second. The system was tested on a real scene of a mechanical part, which is used in truss assembly in space.