JPS6015509A - Light interference angular velocity meter - Google Patents

Abstract

PURPOSE:To reduce a linearity error, by installing optical phase modulator and phase shifter on an input and output end of optical path producing the Sagnac effect and controlling a light source by operating phase driving frequency component and phase modulation driving frequency component. CONSTITUTION:A phase shifter 25 is arranged in series on one input and output and of an optical path 16 and the phase shifter 25 is driven by a driving frequency fo from a shift driving circuit 26 with approximately pi/2 of phase difference between mutually opposed transmitting rays of light. On the other input and output end of the light path 16 is installed a phase modulator 27 and is modulated by output of a phase modulation driving circuit 28. The circuit 28 is disconnected after synchronization with a driving signal of the circuit 28 is disconnected after synchronization with a driving signal of the circuit 26 and an output of a light receiver 16 is taken out through BPF32, 33 as frequency fo component and modulated frequency fm component of the circuit 28. Next, after synchronized detection 34, 37, these components are supplied to a velocity meter processing circuit. Further, they are compared with an output of the reference power source 49 through squaring circuit 45, 46 and addition circuit 47 and a light driving circuit 24 is driven by the compared output. Thus, a linearity error can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical interference gyrometer that utilizes the Zabnak effect, and is particularly intended to stabilize the light level thereof.

<Prior Art> In a conventional optical interference angular velocity meter, as shown in FIG. ,
The light is divided into clockwise light 14 and counterclockwise light 15, and these lights are incident on both ends of the optical path 16, respectively. The optical path 16 is, for example, an optical fiber wound in a loop. These nine right-handed lights 16 and left-handed received lights 17 that have passed through the optical path 16
are mutually coupled by the distribution coupling means 13 to produce interference light 18.
When an angular velocity along the circumferential direction of the 3° optical path 16 received by the light receiver 19 and an angular velocity Ω around the same axis as the axis of the shunting optical path 16 are applied, a so-called Sagnac effect occurs and the optical A phase difference occurs between the two components 16 and 17 that have passed through the path 1G. The light intensity 10 of the interference light 18 of these two lights becomes IO"'1-4 (Δφ+Δψ). By detecting the strong IIIO of this interference light 18, the angular velocity Ω applied to the optical path 16 can be detected.

As described above, in this type of optical interference angular velocity meter, the detected angular velocity is related to the light intensity of the interference light 18, so it is necessary to keep the maximum value of the electrical signal received by the light receiver 19 constant. In the conventional method, as shown in FIG.
1 and the reference voltage 5 from the reference voltage generator 22 are compared by the comparator 23, and the light source drive circuit 24 is controlled by the comparison output, and accordingly, the way the light is emitted from the light source 110 is controlled. , this result is input to the comparator 23.
The output was made to match the reference voltage.

In this conventional optical interference angular velocity meter, the intensity of the optical output of the light source 11 is maintained stably, but the original interference velocity converter includes the optical splitting coupler 13, the optical path 16, and the optical receiver 19.
Furthermore, as shown in the figure, there are commonly used optical phase modulators and optical phase shifters that are affected by temperature fluctuations, external vibrations, etc., such as rotation of the optical principal axis or misalignment of the optical axis. or the sensitivity of the light receiver 19 has changed,
The maximum value of the output electric signal of the light receiver 19 fluctuates, and as a result, there is a drawback that an IJ nearness error occurs in the original interference angle 'MIX meter. Note that since the intensity of the output electric signal from the light receiver 19 changes due to the Sagnac effect, it is not possible to stabilize the entire optical interference gyrometer using this received intensity.

<Summary of the Invention> The object of the present invention is to provide an optical interference gyro meter that is difficult to change due to disturbances such as temperature and vibration, can keep the maximum value of the photoelectric conversion output signal constant, and therefore improves the accuracy of linearity. It provides:

According to this invention, an optical phase modulator and a phase shifter are provided at the input and output ends of an optical path, respectively, and the phase difference of light transmitted through the phase shifters in opposite directions is '= 2J2 The phase shift drive circuit alternately repeats the following: 1, and the phase shift 1 is synchronized with the drive of the phase shift 1 deception circuit. 1. Disconnect the drive circuit. - force, transferred from the output of the light receiving means a'll 'd"Q,
The 1 drive frequency component is extracted by the first F wave generator, and the 14 drive frequency component is extracted by the second P wave generator. The first of these? The outputs of the p-wave device and the second wave device are squared and added together, and this added output is compared with a reference value to control the light arrival so that the two match.

<Embodiment> FIG. 2 shows an embodiment of the optical interference gyrometer according to the present invention, and parts corresponding to those in FIG. 1 are given the same reference numerals. In this embodiment, a phase shifter 25 is arranged in series at one input/output end of the optical path 16. This phase shifter 25 provides a phase difference between the light transmitted from one side and the saw light transmitted from the other side, and the polarity of this phase difference alternates. Phase shift drive circuit 26 to invert
A drive signal of frequency fo is applied to the phase shifter 25 from .

A phase modulator 27 is provided in this example in cascade to the other input and output end of the optical path 16.

However, these phase modulator 27 and phase shifter 25 are connected to the optical path 16.
They may be provided at the same input and output terminals. The phase modulator 27 is subjected to phase modulation by the output of the phase modulation drive circuit 28, and the phase of the light transmitted therethrough is modulated. This phase modulation drive circuit 28-2 is periodically separated from the phase modulator 27 in synchronization with the drive signal of the phase shift drive circuit 26. In this example, the output of the phase shift drive circuit 26 is frequency-divided by a frequency divider 29 to 1, and the frequency-divided output causes the switch 31;
The phase modulation drive circuit 28 is periodically disconnected from the phase modulation upper unit 27.

The output of the light receiver 19 is supplied to lachrymal fluid vessels 32 and 33, the F wave generator 32 extracts a component of the drive frequency fO of the phase shift drive circuit 26, and the filter 33 extracts the component of the drive frequency fO of the phase shift drive circuit 28. The component of frequency fm is extracted. P wave device 32
The output is synchronously detected by the synchronous detection circuit 34 using the output of the phase shift drive circuit 26. The output of the phase modulation driving circuit 28 is also given to a phase inverter 35, and the output with and without phase inversion is taken out by a changeover switch 36, and the output of the phase modulation drive circuit 28 is taken out by a changeover switch 36. The output of the lachrymal fluid machine 33 is synchronously detected. The changeover switch 36 is controlled by the output of the phase shift drive circuit 26. The outputs of the synchronous detection circuits 34 and 37 are connected to the low-pass P-wave generator 4 through switches 38 and 39, respectively.
Supplied at 1.42.

The switches 38 and 39 are controlled according to the output of the frequency divider 29, but these are controlled in an inverse relationship to each other. Filter 4
The output of 1.42 is fed to output terminals 4.3.44, one or both of which are fed into a processing circuit (not shown) for detecting the angular velocity of the optical interference gyrometer.

In addition, the outputs of these lachrymal fluid vessels 41 and 4.2 are outputted by a square circuit 45.
．． 46, and the outputs of these square circuits 45 and 46 are added together in an adder circuit 47. The added output is amplified in an amplifier 48, and compared with the output of a reference power source 49 in a comparator 51. The optical drive circuit 24 is controlled.

In the phase shifter 25, a phase difference of +2'2 is alternately given between the lights passing through the phase shifter 25 in opposite directions, so the drive frequency fo of the phase shift drive circuit 26 is used as the fundamental component. The output ■0 of the interference light 18 becomes 10cc fish (Δφshig). This output ■0 changes by 5IfIΔφ with respect to the phase difference Δφ caused by the Sagnac effect. At this time, the phase modulator 27 is in an inactive state, and when the phase modulation drive circuit 28 is disconnected, the output is -.

becomes sLnΔφ.

On the other hand, when the switch 31 is turned on and the phase modulator 27 is phase modulated by the drive signal of the frequency fm, the interference light 18 whose basic component is the phase modulation drive frequency fm at that time
The optical output Im is given by ImoCJl(η1sin(Δφ±ψ)).

At this time, the phase shifter 25 performs its phase shifting operation. Jl(η) is a Bessel function of the first kind, and η=2
β torture πfmτ. β is the modulation index, τ is the optical fiber 1
The propagation time of light in 6, ψ indicates the phase difference bias of 100 given by the phase shifter 25. Therefore, the intensity of the interference light 18 having the frequency fm as a fundamental component changes with respect to the phase difference Δφ.

When the output of the phase shift drive circuit 26 is as shown in FIG. 3A, the switch 31 is controlled as shown in FIG. 3B, and the switches 38, 39
are controlled as shown in FIG. 3C and D, respectively. That is, when the switch 31 is on, the switch 38 is off and the switch 39 is on. Further, the ON period and the OFF period of the switch 31 are the same length, and in the ON period, the number of times that the phase difference by the phase shifter 25 becomes +-2-100 is equal, and in this example, it is once. It is said to be one by one. In this way, the frequency fO acid component in the output of the photoreceiver 19,
The frequency fm component is taken out alternately, and as shown in FIG.
The output of the filter 42 is expressed as VmcOsΔφ. These are each squared by a square circuit 45°46, and the output of the adder 47 is VO25in2△φ+vm2
cos2△φ, and by adjusting the gain in advance so that VO=Vm, the output of the adder 47 becomes f=
The comparator 5
The light source drive circuit 24 is controlled by the output of 1. In this way, the maximum values Vo and Vm of the signals whose fundamental components are frequencies fO and fm can be kept constant, respectively.
Therefore, the linearity error of the optical interference gyrometer can be reduced accordingly.

Effect> As described above, according to the second invention, the output of the light receiver 19 can be used to stabilize it, and therefore, each part of the optical interference gyrometer as a whole is safe against external disturbances. jl, and the linearity error of the optical interference gyrometer can be reduced.

[Brief explanation of drawings]

Figure 1 is a block diagram showing a conventional optical interference gyrometer, Figure 2
The figure is a block diagram showing the optical interference gyrometer of the present invention.
The figure is a time chart showing an example of switching the switch, and FIG. 4 is a diagram showing an example of the signal output waveform of the wave transmitters 41 and 42. IJ: light source, 12: light distribution/coupling means, 16: optical path, 1
9: Light receiver, 24: Light source drive circuit, 25: Phase shifter, 26
: Phase shift drive circuit, 27: Phase modulator, 28 Biphase modulation drive circuit, 32.33: Bandpass v5 filter, 34.37:
Synchronous detector, 41, 42: Low pass? P temporary vessel, 45,
46: Square circuit, 47: Addition circuit, 49: Reference power supply, 5
1: Comparator. 7171 Figure ]6 71-3 Figure ON FF- 2172 Figure Horoscope

Claims (1)

[Claims] (1) A light source, an optical path that goes around at least once, a means for making the light from the light source enter the optical path as a clockwise and counterclockwise source, and clockwise light emitted from the optical path. and interference means for interfering the left-handed and counter-clockwise lights, respectively, and a circumferential angular velocity is added to the optical path to increase the optical intensity of the interfering light by increasing the phase difference that appears due to the Zabnack effect between the clockwise original and counter-clockwise lights. 1i, and measures the angular velocity from the output of the first stage of light receiving. Between the lights,
is a phase shifter that provides a phase difference of 2, a phase modulator that is arranged in series at one input/output end of the optical path and provides phase modulation to the light passing through the optical path, and the phase shifter. A phase shift drive circuit that drives the phase shifter and a phase shift drive circuit that drives the phase shifter, and synchronize with the drive signal of the phase shift drive circuit so as to alternately give a phase difference of 1 between the lights passing in opposite directions. a separating means for separating the phase modulation driving circuit from the modulator; and a first device for extracting a driving frequency component of the phase shift driving circuit from the output of the light receiving means.
a P wave device, a second wave device for extracting a drive frequency component of the phase modulation drive circuit from the output of the light receiving means, and a first
It is equipped with an adding means for squaring the outputs of the P-wave device and the second P-wave device and adding them together, and a comparison means for comparing the intermediate layer and output with a cardinal value and controlling the light source based on the comparison output. Optical interference gyrometer.