Katsuyoshi Miura

Rotation vector analysis of eye movement in three dimensions with an infrared CCD camera.

We have developed a new technique for analyzing the rotation vector of eye movement in three dimensions with an infrared CCD camera based on the following four assumptions; i) the eye rotates on a point; ii) the pupil edge is a circle; iii) the distance from the center of eye rotation to pupil circle remains unchanged despite the rotation; iv) the image of the eye by the CCD camera is projected onto a plane which is perpendicular to the camera axis. After taking digital images of voluntary circular eye movements, we first constructed a three-dimensional frame of reference fixed on the orbita of the subject wearing a goggle equipped with an infrared CCD camera, and determined the space coordinates of the center of eye rotation, the center of the pupil, and an iris freckle. We then took digital images of the eye movements during a saccade or vestibulo-ocular reflex (VOR) and analyzed the axis and angle of the eye movements by the trajectories of the center of the pupil and the iris freckle. Finally, Listings plane of saccade and the gain and the phase of VOR were obtained. The suitability of this technique is examined.

Dynamics of the Vestibulo-ocular Reflex in Patients with the Horizontal Semicircular Canal Variant of Benign Paroxysmal Positional Vertigo

Objective Two types of direction-changing positional nystagmus, the geotropic and apogeotropic variants, are observed in patients with the horizontal semicircular canal (HSCC) type of benign paroxysmal positional vertigo (H-BPPV). In this study, we assessed the dynamics of the vestibulo-ocular reflex (VOR) of the HSCC in patients with H-BPPV. Material and Methods Patients were rotated about the earth-vertical axis at frequencies of 0.1, 0.3, 0.5, 0.7 and 1.0 Hz with a maximum angular velocity of 50°/s. Eye movements were recorded on a video imaging system using an infrared charge-coupled device (CCD) camera, and our new technique for analyzing the rotation vector of eye movements in three dimensions was used. Results In the patients with geotropic positional nystagmus, there were no differences in VOR gain between rotation to the affected and unaffected sides at frequencies of 0.1–1.0 Hz. Although no differences in VOR gain at frequencies of 0.3–1.0 Hz were noticed in patients with apogeotropic positional nystagmus, the VOR gain at 0.1 Hz was significantly smaller on rotation to the affected compared to the unaffected side. Conclusion The results indicate that cupulolithiasis in the HSCC affected the dynamics of the HSCC-ocular reflex at 0.1 Hz, but not at higher frequencies, and that canalolithiasis in the HSCC does not change the VOR gain of the HSCC at any frequency. It is suggested that cupulolithiasis causes transient impairment of HSCC function by means of its mechanical restriction of movements of the cupula.

Vertical Canal Function in Normal Subjects and Patients with Benign Paroxysmal Positional Vertigo

Objectives —To assess the dynamics of the vertical semicircular canal (VSCC)-ocular reflex in normal subjects and then to compare their gain in VSCC-ocular reflex with that of patients with benign paroxysmal positional vertigo (BPPV). Material and Methods —Subjects were sinusoidally rotated around the earth-vertical axis with their head tilted 60° backward and turned 45° to the right or left side from the sagittal plane at frequencies of 0.1, 0.3, 0.5, 0.7 and 1.0 Hz with a maximum angular velocity of 50°/s. Head rotation to the right side on the right anterior semicircular canal (SCC)–left posterior SCC plane or to the left side on the left anterior SCC--right posterior SCC plane stimulated the pair of VSCCs. Eye movements were recorded on a video imaging system with an infrared charge-coupled device camera, using our new technique for analyzing the rotation vector of eye movements in three dimensions. Results —The mean gains in left posterior SCC-ocular reflex in normal subjects ranged from 0.44 at 0.1 Hz to 0.79 at 1.0 Hz, while the mean gains in right anterior SCC-ocular reflex ranged from 0.45 at 0.1 Hz to 0.73 at 1.0 Hz. The mean gains in right posterior SCC-ocular reflex in normal subjects ranged from 0.53 at 0.1 Hz to 0.89 at 1.0 Hz, while the mean gains in left anterior SCC-ocular reflex ranged from 0.53 at 0.1 Hz to 0.88 at 1.0 Hz. Thus, the gains in VSCC-ocular reflex did not differ among the four VSCCs in normal subjects. Similarly, vestibulo-ocular reflex (VOR) gains of the four VSCCs in patients with right- or left-sided BPPV were almost the same at all frequencies compared to those of normal subjects. Conclusion —In patients with BPPV, gains in VOR in the four VSCCs were not changed in comparison with those of normal subjects. It is suggested that the mass of free-floating otoconial debris associated with canalolithiasis was too small compared to that of the endolymph to change the canal dynamics.

THz emission characteristics from p/n junctions with metal lines under non-bias conditions for LSI failure analysis

We have investigated the characteristics of THz emissions from p/n junctions with metallic lines under non-bias conditions. The waveforms, spectra, and polarizations depend on the length and shape of the lines. This indicates that the transient photocurrents from p/n junctions flow into the metallic lines that emit THz waves and act as an antenna. We have successfully demonstrated the non-contact inspection of open defects of multi-layered interconnects in a large-scale integrated circuit using the laser THz emission microscope (LTEM). The p/n junctions connected to the defective interconnects can be identified by comparing the LTEM images of normal and defective circuits.

Laser THz emission microscope as a novel tool for LSI failure analysis

Abstract We have proposed and developed a novel technique for a non-contact inspection of defective interconnections in an LSI chip using a laser terahertz emission microscope (LTEM). The LTEM measures the THz emission images of an LSI chip by scanning it with fs laser pulses. When a fs laser pulse irradiates a p–n junction in an LSI chip, transient photocurrent flows into interconnections resulting in the emission of the THz pulse into free space. We investigated the characteristics of the THz emissions from simple test element group samples which consist of p–n junctions connected to metal lines. It was found that the metallic lines connected to photo-excited p–n junctions worked as THz emission antennae which enhance the emission efficiency of THz pulses near their resonant frequencies corresponding to the line lengths. This result indicates that THz emission signals from p–n junctions in circuits strongly depend on the structure of the interconnections. We show the successful results on the inspection of defective interconnections in MOSFET devices and C7552 ISCAS’85 benchmark circuits using LTEM. By comparing the THz emission images between a normal circuit and a defective one, it is possible to identify the p–n junctions connected to the defective interconnections without electrical contacts.

Statistical optimization of Canny edge detector for measurement of fine line patterns in SEM image

For the purpose of developing a recognition system for fine line patterns in the LSI, a statistical optimization method of the Canny edge detector for scanning electron microscope (SEM) images is proposed. The analysis of variance (ANOVA) is applied to the estimation of parameters in the SEM image: the grey level in the background, contrast, the line width and the noise level. These parameters are used to optimize statistically the Canny parameters, a scale parameter of the smoothing filter and a binarization threshold, by using noise characteristics of the SEM image. The proposed method is applied to model images and a real SEM image to show its validity.

Boundary extraction in the SEM cross-section of LSI

We have proposed a boundary extraction algorithm for cross-sectional critical dimension (CD) measurements of the scanning electron microscope (SEM) images in machine/computer vision. Noisy SEM images have the image discontinuity of roof edge with peak. A task is to extract a low contrast boundary or edge with about one pixel width in a noisy cross sectional SEM image. Also CD measurements require that the algorithm locate a boundary or an edge at the correct position. Our policy is to detect the edges with high degree of confidence at first, and then to extract the edges with the high probabilities of edge that are calculated by using gray levels of neighboring pixels. Our proposed algorithm integrates the Gaussian pyramid to suppress noise, morphological operations to detect the edges with high degree of confidence, the relaxation method to recover the gaps in the detected edges, and the hierarchical approach. Application of the proposed algorithm to cross sectional SEM images of DRAMs shows its validity.

Hierarchical VLSI Fault Tracing by Successive CircuitExtraction from CAD Layout Data in the CAD-Linked EB TestSystem

A hierarchical VLSI fault tracing method is proposed which isapplicable to the case where only CAD layout data is available in theCAD-linked electron beam test system. The CAD layout data is assumedto be hierarchically structured. The method uses the expansion of apreviously proposed integrated algorithm which combines atransistor-level fault tracing algorithm and a successive circuitextraction from a non-hierarchically or a flat structured CAD layoutdata. The method allows us to trace a fault hierarchically from thetop level cell to the lowest primitive cell and from the primitivecell to the transistor-level circuit in a consistent mannerindependent of circuit functions even when the cell data and thetransistor-level circuit data exist in a level as a mixture. Anapplication of the method to a hierarchically structured CMOS modellayout with about 600 transistors shows its validity.

Automatic EB fault tracing system by successive circuit extraction from VLSI CAD layout data

An automatic electron beam (EB) fault tracing system is described which enables us to trace faults automatically from the top level cell to the lowest primitive cell and from the primitive cell to the transistor-level circuit independently of circuit functions. Only VLSI CAD layout data is required.

Hierarchical fault tracing for VLSI sequential circuits from CAD layout data in the CAD-linked EB test system

A previous hierarchical fault tracing method for combinational circuits which requires only CAD layout data in the CAD-linked electron beam test system is expanded as applicable to sequential circuits. The characteristics in the method remain unchanged that allow us to trace a fault hierarchically from the top level cell to the lowest primitive cell and from the primitive cell to the transistor-level circuit in a consistent manner independently of circuit functions. The applied results of the CAD layouts of some sequential CMOS benchmark circuits show its superiority to the guided-probe method where circuit logical functions are first extracted from the CAD layout data and then the guided-probe testing is executed.