Noboru Niwa

Rotation detection by optical heterodyne fiber gyro with frequency output

A fiber gyro with optical heterodyne detection is proposed. The experimental setup has been constructed and tested. Both the frequency difference in the fiber and the path-length difference between counterpropagating waves are eliminated to reduce output drift. An electronic circuit for phase-nulling detection has been constructed, which gives an electronic frequency output in proportion to the rotation rate. Direct frequency modulation of a single-mode laser diode has been adopted to reduce the noise that is due to the backward Rayleigh scattering. A short time resolution of the rotation rate of about 5 deg/h for an integration time of 1 sec. (0.0014 deg/sec) has been achieved with good linearity, for an integration time of 1 sec.

Fiber-optic laser gyro with easily introduced phase-difference bias.

An optical system for easy introduction of phase-difference bias to optimize the sensitivity of the fiber-optic laser gyro is proposed. The theory of using a laser diode has been considered, and the rotation detection experiment has been performed. The experimental setup consists of a 300-m long single-mode optical fiber, individual optical components, and a laser diode stabilized by a thermal controller and an optical isolator. Short-time resolution of the rotation rate better than 0.87 mrad/sec has been achieved with good linearity.

Optical Fiber Laser Gyro: Homodyne and Heterodyne Detections

The ring interferometer with a multiturn single-mode optical fiber loop has been investigated for use as a rotation rate sensor utilizing the Sagnac effect. We have proposed an optical system with homodyne detection, in which the phase-difference bias can easily be introduced, and the rotation detection experiment was performed using the preliminary test setup with a He-Ne laser [1].

Drift Reduction in the Optical Heterodyne Fiber Gyro

Optical Heterodyne Fiber Gyro[l,2], which we have proposed and experimented with, has a wide dynamic range and a good linearity. We demonstrated the rotation detection with 5 digits [1,2]. However, it has a relatively large zero-point drift induced mainly by thermal fluctuation of the acoustic-wave velocity in the Acousto-Optical Modulator (AOM) [1,2].

Application Of Television Techniques To Image Data Acquisition

New television techniques applied to image data acquisition and several examples in Japan are described.

A Narrow Band Television System as a View-Finder of Balloon Borne Solar-Telescope

観測装置を気球で高層にあげて天文観測する際, ファインダーとしてテレビカメラが活用されている.筆者らは, 気球搭載望遠鏡で太陽面微細構造を観測する際, 撮像蓄積管による狭帯域テレビカメラをファインダーに使用し, 視野の選択と画像信号による焦点合わせをおこなった.また, 気球の形状変化の実時間観測をおこない, 気球の設計資料を得るなどに応用した.この報告を中心に, 気球天文学へのテレビカメラの応用例を紹介し, 今後の応用面と問題点を述べた.