Ring laser gyroscope

About: Ring laser gyroscope is a research topic. Over the lifetime, 2070 publications have been published within this topic receiving 18609 citations. The topic is also known as: Sagnac interferometer.

Design and fabrication of a dual axial gyroscope with piezoelectric ceramics

Abstract: Piezoelectric gyroscopes are the devices to measure angular rotation of a system with respect to an inertial frame of reference means of the Coriolis principle. Most of current piezoelectric gyroscopes detect the angular velocity about a single axis of rotation. This paper describes development of a new dual axial gyroscope made out of the piezoelectric ceramic, PZT, that can overcome the limitation of the current single axial type. Validity of the new structure is checked through finite element analysis. Based on the design, an experimental sample of the sensor is fabricated and its performance is discussed in comparison with the theoretical expectation. The results show that the present gyroscope is capable of measuring the rotational velocity over two orthogonal axes simultaneously with good enough sensitivity and distinction between the two axes.

Optical Heterodyne Gyroscope Using Two Reversed Fiber Coils

Abstract: In a fiber-optic gyroscope optical heterodyne detection techniques are suited to obtain a stable scale factor and a linear output of the Sagnac phase shift, as well as a wide dynamic range to detect the rotation rate1). Nevertheless, it is rather hard to contrive a clever fiber-optic system by which a stable output is produced in the presence of environmental noise factors. For example, the presence of frequency difference between the two optical waves counterpropagating in a fiber coil yields a phase bias in the heterodyne output, which is a factor fluctuating the phase output2). Another fluctuating factor also arises from the separate paths transmitted by the two counterpropagating optical waves3). In order to overcome such problems, a novel heterodyne detection scheme was proposed previously4). The proposed system incorporated an orthogonally polarized two -frequency laser beam in conjunction with a single fiber-optic interferometric system using a polarization-maintaining single-mode fiber-coil. However, it was soon proved that the mode coupling effect between the orthogonal components guided in the fiber coil was an unavoidable fluctuating factor in the gyroscope operation. In this paper another novel scheme is proposed to avoide such drawbacks. Two reversed fiber coils play an essential role in the proposed scheme.

Phase modulation of a ring-laser gyro - Part I: Theory

Abstract: The theory of a multimode ring-laser gyro with intracavity phase modulation is developed, starting from the wave equation for a rotating reference frame. The approach is to extract physical information without actually solving the equations. Considering each of the oppositely directed traveling waves (ODTW) separately, the behavior is similar to that of an ordinary two-mirror phase-modulated laser. However, when the waves are heterodyned to measure a beat frequency, small mode-pulling effects become important, and, if the ODTW are treated unequally by the system, a frequency error or offset results. Sources of offset include time variation of the modulator length, reactance of the gain medium, and detuning of the modulator frequency from axial mode spacing. When back reflections are included in the theory, the results reduce to the single-mode ring-laser case, with the coupling coefficient dependent upon overlap between the ODTW at the reflector. It is predicted that at low rotation rates the ODTW frequencies will still become locked together, except in a very special case where the lock-in threshold vanishes. Significance of the nature of the reflecting elements is discussed. Comments are made on the predicted merits of phase modulation as an improvement in the low-rotation-rate measuring capabilities of the device.

Quantization reduction for evaluating laser gyro performance using a moving average filter

Abstract: Ring Laser gyro performance is typically evaluated by measuring the random walk in angle associated with each instrument over a range of operating and environmental conditions. However, the ring laser gyro, being basically a digital sensor, outputs accumulated angle in quantized pulses. This quantization in the presence of dither has a similar effect on gyro test data as white noise in angle. To reduce the effect of quantization and dither on gyro test data, so as to enable the random walk coefficient of the instrument to be determined to high precision in short times, a high speed Moving Average Filter (1 kHz) was developed which outputs accumulated gyro data samples once per second. The quantization noise power is reduced by a factor greater than 512 and the dither is reduced by a factor greater than 200 db while the random walk characteristic is virtually unaffected. The following describes the operation of this Moving Average Filter, analyses its effect on gyro test data and presents test results.