JP2000055671A - Method and apparatus for offset cancellation of output signal of optical fiber gyro - Google Patents

Abstract

(57) [Problem] In a conventional optical fiber gyro, since the polarity of a piezo element of a phase modulator is fixed, an offset of an electric system included in a gyro output cannot be eliminated, and accuracy is reduced. Was the cause. A method and apparatus for canceling an offset of an output signal of an optical fiber gyro according to the present invention include a phase modulator (9).
The gyro output of the gyro output (18a) is eliminated by subtracting the gyro output after inversion obtained by inverting the polarity of the piezo element from the gyro output before inversion obtained before inverting the polarity. This is a configuration for obtaining an output (30).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for canceling an offset of an output signal of an optical fiber gyro, and more particularly to a method of obtaining a gyro output after inversion when the polarity of phase modulation is inverted before the polarity is inverted. The present invention relates to a novel improvement for eliminating an electrical offset by subtracting from a gyro output before inversion.

[0002]

2. Description of the Related Art Conventionally, as an offset erasing method of an output signal of an optical fiber gyro of this kind, there are known methods.
The well-known phase modulation method shown in FIG. 2 has been adopted.
That is, what is indicated by reference numeral 1 in FIG. 2 is an optical system having a ring-shaped sensing coil 2 formed of an optical fiber, and this sensing coil 2 is connected via a first coupler 3, a polarizer 4 and a second coupler 5. The light source module 6 and the detector 7 are connected by an optical fiber 8.
Between the sensing coil 2 and the first coupler 3, a phase modulator 9 made of a well-known piezo element (PZT) is provided in contact with the optical fiber 8 and located near the sensing coil 2. . By driving the phase modulator 9 with an AC signal of a predetermined frequency, a phase difference of light generated by the angular velocity is caused to interfere, and a gyro output 18a is obtained by a well-known Sashack effect of light.

An electric system 10 is connected to the optical system 1, and an input amplifier 11 of the electric system 10 is connected to the detector 7.
Is output after photoelectric conversion. A laser diode drive circuit 12 connected to the output side of the input amplifier 11 is connected to the light source module 6 via a laser driver 13, and a laser beam enters the optical fiber 8 from the light source module 6. The input amplifier 1
1 is connected to a modulation control circuit 14 and a lock-in amplifier 17, and an oscillation circuit 15 and a driver 16 are connected to the modulation control circuit 14. An output of the driver 16 is input to the phase modulator 9. Have been. The output of the oscillation circuit 15 is input to the driver 16 and also to the lock-in amplifier 17,
And a gyro output 19 through an output amplifier 18.

[0004]

The output method of the conventional optical fiber gyro has been configured as described above.
The following issues existed. That is, in an optical fiber gyro, an offset error occurs in a gyro output due to an offset of an optical system generally generated by Rayleigh scattering or the like and an offset of an electric system generated by components of an electronic circuit or a signal processing system. The offset is most of the offset of the optical fiber gyro, and it is impossible to eliminate the offset of the electric system by the conventional method.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. In particular, a gyro output after inversion when the polarity of phase modulation is inverted is obtained by inversion obtained before inversion of the polarity. It is an object of the present invention to provide a method and an apparatus for eliminating an offset of an output signal of an optical fiber gyro, wherein an electrical offset is eliminated by subtracting the offset from a previous gyro output.

[0006]

SUMMARY OF THE INVENTION According to the present invention, there is provided a method of offset elimination of an output signal of an optical fiber gyro, wherein light from a light source is guided to a sensing coil comprising an optical fiber,
In an optical fiber gyro using a phase modulator provided in the vicinity of the sensing coil to obtain a gyro output by interfering a phase difference of light at the time of inputting an angular velocity, the gyro output is obtained by inverting the polarity of a piezo element of the phase modulator. Subtracting the gyro output after inversion from the gyro output before inversion obtained before inverting the polarity to obtain a corrected gyro output in which the electric system offset of the gyro output is eliminated. In the optical fiber gyro using a phase modulator provided in the vicinity of the sensing coil to guide the light from the optical fiber to a sensing coil made of an optical fiber, to obtain a gyro output by interfering the phase difference of the light at the time of inputting the angular velocity, A polarity inversion switch provided between a driver for driving the phase modulator and the phase modulator; A configuration in which an arithmetic unit for sending a command for inverting the polarity reversing switch inputs the gyro output.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a method and an apparatus for offset offset of an output signal of an optical fiber gyro according to the present invention will be described below with reference to the drawings. Note that the same or equivalent parts as those in the conventional example will be described using the same reference numerals. 1 is an optical system having a ring-shaped sensing coil 2 formed of an optical fiber, and the sensing coil 2 includes a first coupler 3,
The optical fiber 8 is connected to the light source module 6 and the detector 7 via the polarizer 4 and the second coupler 5.

A well-known piezo element (PZ) is provided between the sensing coil 2 and the first coupler 3 in a state of being in contact with the optical fiber 8 and in the vicinity of the sensing coil 2.
T) is provided. By driving the phase modulator 9 with an AC signal having a predetermined frequency, a gyro output 18a is obtained by interfering a phase difference of light generated by the angular velocity.

An electric system 10 is connected to the optical system 1, and an input amplifier 11 of the electric system 10 is connected to the detector 7.
Is output after photoelectric conversion. A laser diode drive circuit 12 connected to the output side of the input amplifier 11 is connected to the light source module 6 via a laser driver 13, and a laser beam enters the optical fiber 8 from the light source module 6.

A modulation control circuit 14 and a lock-in amplifier 17 are connected to the output side of the input amplifier 11, and an oscillation circuit 15 and a driver 16 are connected to the modulation control circuit 14. The output of the driver 16 has a polarity. The signal is input to the phase modulator 9 via the inversion switch 20. The output of the lock-in amplifier 17 is input to an arithmetic unit 21 composed of a CPU as a gyro output 18a via an output amplifier 18, and an inversion command 21a output from the arithmetic unit 21
Is input to the polarity inversion switch 20 so that the polarity of a piezo element (not shown) of the phase modulator 9 can be inverted.

Next, the operation will be described. First, when a system (not shown) connected to the optical fiber gyro 30 is activated, a command 21 a is input from the arithmetic unit 21 to the polarity inversion switch 20 in conjunction with the activation of the system, and the phase modulator 9 is activated. The polarity of the piezo element is inverted, the angular velocity input at that time is detected by the detector 7, and the obtained gyro output 18a is stored in the arithmetic unit 21 as the gyro output after the inversion. Next, the gyro output 18a obtained by returning the polarity inversion switch 20 again by the command 21a is used as a gyro output before inversion, and the arithmetic unit 21 subtracts the gyro output after inversion from the gyro output before inversion. Thus, a corrected gyro output 30 (angular velocity signal output) in which the offset generated in the electric system 10 is eliminated can be obtained. The polarity of the piezo element of the phase modulator 9 can be easily inverted by exchanging the two signal lines 31 from the driver 16.

[0012]

The method and apparatus for canceling the offset of the output signal of the optical fiber gyro according to the present invention are configured as described above, and the following effects can be obtained. That is, by inverting the polarity of the piezo element of the phase modulator in the phase modulation method and performing a subtraction process using the gyro outputs before and after the inversion, it is possible to obtain a gyro output in which the offset of the electric system is eliminated. Since most of the offsets are eliminated, high accuracy can be obtained when integrating the gyro output.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a device for canceling an offset of an output signal of an optical fiber gyro according to the present invention.

FIG. 2 is a configuration diagram showing a conventional configuration.

[Explanation of symbols]

 2 Sensing coil 6 Light source 8 Optical fiber 9 Phase modulator 16 Driver 18a Gyro output 20 Polarity inversion switch 21a Command 30 Correction gyro output

Claims (2)

[Claims] 1. A method for guiding a light from a light source (6) to a sensing coil (2) composed of an optical fiber (8) and interfering with a phase difference of light when an angular velocity is input to obtain a gyro output (18a). Phase modulator (9) installed near the sensing coil (2)
An optical fiber gyro using the phase modulator
By subtracting the gyro output after inversion obtained by inverting the polarity of the piezo element of (9) from the gyro output before inversion obtained before inverting the polarity, the gyro output is obtained.
(18a) A method for eliminating an offset of an output signal of an optical fiber gyro, wherein a corrected gyro output (30) in which an offset of an electric system is eliminated is obtained. 2. A method for guiding a light from a light source (6) to a sensing coil (2) formed of an optical fiber (8) and interfering with a phase difference of light when an angular velocity is input to obtain a gyro output (18a). Phase modulator (9) installed near the sensing coil (2)
An optical fiber gyro using the phase modulator
(9) a driver for driving (16) and the phase modulator (9)
And a polarity reversing switch (20) provided between the gyro output (18a) and the polarity reversing switch.
An offset erasing device for an output signal of an optical fiber gyro, comprising: (20) an operation unit (21) for sending an inversion command (21a).