Yasuji Seko

Proposal of recordable pointer: Pointed position measurement by projecting interference concentric circle pattern with a pointing device

We propose a new pointing device that can measure pointed positions by processing the interference concentric circles projected with a pointing device. The pointing device has a donut-shaped lens that is designed so as both to make the laser source be two hypothetical sources for forming optical interference and to project the concentric circle pattern widely. Two image sensors set on the projected side capture small parts of the concentric circles, and its center coordinate that is a pointed position of the pointing device is calculated from two normal lines to the arcs of the circles. In practice, we succeeded in measuring the pointed position accurately by real-time processing of the widely projected concentric circle patterns. We demonstrated mouse cursor operation on a large screen with the pointing device and also used it as real-object-based user interface to show the related information of real objects by pointing them

Valence Subband Structures and Optical Properties of Strain-Compensated Quantum Wells

The strain compensation effects on the valence subbands and on the optical properties of GaInAs/AlGaInAs quantum well structures are theoretically studied for the first time. In the case of compressive-strained quantum wells, where the top valence subbands are always formed with heavy hole (HH) subbands, the compensatingly tensile-strained barriers shift the first light hole (LH) subbands upward increasing the valence band mixing between them, and significantly reducing the transverse electric (TE) gain. In contrast, in the tensile-strained quantum wells whose top valence subband is formed with LH subband, the compensatingly compressive-strained barriers shift the top LH subband downward and on some occasions the top LH subband is replaced with the first HH one. The increase of the TE gain is relatively small due to the strong valence band mixing. The strain of the barrier layers is found to play an important role in the valence subband structures and optical properties.

Optical 3D sensing by a single camera with a lens of large spherical aberration

We propose a new principle to measure the 3D position of a light source by a video camera with a lens of large spherical aberration. The light source is transformed into a ring image by the large spherical aberration of the lens; the rings center position and diameter, respectively, determine the direction and distance to the light source. We clarify the characteristics of the ring images, and succeed in measuring the 3D position by processing the video images of the optical rings in real time.

Firefly capturing method: Motion capturing by monocular camera with large spherical aberration of lens and Hough-transform-based image processing

We demonstrate a new motion capturing method that uses the monocular camera with large spherical aberration of lens to measure 3D positions of point light sources attached on an object in real time without any sequential lighting. Point light sources are transformed into circle patterns by the large spherical aberration of lens mounted in the camera. The diameter and center position of circle pattern give the distance and direction to the light source, resulting in measuring its 3D position. Circle patterns are extracted by video image processing based on Hough transform even if they are overlapped each other. We tracked the circle patterns by predicting their next positions by Kalman filter that includes the acceleration of movement. By combining these processing techniques we succeeded in demonstrating the motion capturing of several LEDs in real time, which is shown in 3D graphics

Simultaneous 3D position sensing by means of large-scale spherical aberration of lens and Hough transform technique

We demonstrate a real time 3D position sensing of multiple light sources by capturing their ring images that are transformed by the molecular lens system with large spherical aberration. The ring images change in diameter in accordance with the distance to the light sources, and the ring center positions determine the directions toward them. Therefore, the 3D positions of light sources are calculated by detecting the diameters and center positions of the circles. This time we succeeded to measure 3D positions of multiple light sources simultaneously in real time by extracting and tracking the circle patterns individually. Each circle is extracted by the Hough transform technique that uses not-closely-distributing three edge points to search the primal votes more than threshold, and is tracked by predicting the successive positions by Kalman filter. These processes make it possible to measure the 3D positions of light sources even in the case of overlapped plural circles. In the experiment, we could track several circle patterns measuring the center positions and diameters, namely, measuring the 3D positions of LEDs in real space. Measurement error of 3D positions for a LED was 6.8mm in average for 150 sampling points ranging from 450mm to 950mm in distance.

A new method to measure 3D position of a light source by tracking the ring images made by a hemispherical lens

We demonstrate a new method to measure 3D position of a light source by tracking the ring images transformed through a single hemispherical lens. The ring images are formed by the large spherical aberration of the lens and always clear regardless of the distance and angle of the light source without any focusing mechanism. Dynamic change of diameter and center position of the ring image enables 3D position measurement of the light source with accuracy and high resolution. Experimental results verified that this new principle solves the 3D optical measurement problems of complex structures, narrow-angle views and slow measuring speed due to focusing mechanism, indicating the possibility for wide applications.