JPH01209316A - Azimuth signal outputting device - Google Patents

Abstract

PURPOSE:To avoid the influences affected by noise signals due to the irregular rotation, by arranging two optical loops to be separated by predetermined angles and to have a common rotary shaft, so that the difference of output signals from a light receiving element corresponding to said optical loops is obtained. CONSTITUTION:Bobbins 1A, 1B each wound with an optical fiber loop have a common rotary shaft M, and fixedly arranged by approximately 90 deg.. There are a light source 2, a modulating element 4, a detector and an APC circuit block 6 provided inside the bobbin 1B. The light from the light source 2 is incident upon the optical fiber lops through the modulating element 4. Then, the light ejected from each fiber loop is photoelectrically converted, so that the azimuth signal is obtained based on a signal indicating the difference of the outputs from the fiber loops.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an azimuth signal output device, and in particular, the present invention is constructed using an optical gyro that detects rotational angular velocity using the saniac effect of light. The present invention relates to a direction signal output device.

(Prior Art) Conventionally, in order to obtain an azimuth signal, an optical fiber gyro constructed by winding an optical fiber has been used. For example, the loop surface created by the optical fiber loop is placed in a vertical plane, and the loop surface is rotated around the vertical axis.
Obtaining direction signal.

(Problem to be Solved by the Invention) However, in a configuration in which the loop surface formed by the optical fiber loop is provided in a vertical plane and the loop surface is rotated around the vertical axis to obtain a direction signal, unevenness in rotation during rotation may occur. Noise signals may be generated.

In this case, as disclosed in Japanese Unexamined Patent Application Publication No. 169714/1982, two optical fiber loops are wound around the same bobbin in the same direction and the same number of times, and the position of the modulation section is adjusted to each other. It is conceivable that by providing them at different ends of the optical fiber loop, the phases of the output signals are shifted by 180 degrees, and further, by taking the difference between these two output signals, in-phase noise can be canceled.

However, in such a noise canceling method, the noise signal due to rotational unevenness is also reversed by 180 degrees, so that the noise signal due to rotational unevenness cannot be removed.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide an azimuth signal output device that is not affected by noise signals caused by uneven rotation during rotation.

(Means for Solving Problems) The present invention provides an azimuth signal output device using an optical gyro, in which two optical loops (formed by using a fiber or by combining reflecting mirrors) have a common rotation axis. The two optical loops are arranged so as to form a predetermined angle θ (0 degrees < θ < 180 degrees), and measurement light from a light source is made to enter each of the two optical loops in opposite directions from both ends thereof. A pair of optical gyros is provided that photoelectrically converts the light emitted from both ends of each optical loop using separate light receiving elements corresponding to each optical loop, and the direction is determined based on the difference signal between the output signals of the pair of optical gyros. This is an azimuth signal output device characterized by obtaining a signal.

Further, in this azimuth signal output device, the S/N is improved most when the predetermined angle θ is approximately 90 degrees.

(Function) In the present invention, since the rotation axes of the two optical loops are the same, the offset due to rotation can be made equal in size and shape by adjusting the sensitivity of the signals obtained by the two optical loops equally. can.

Furthermore, since the detection signals obtained by the two optical loops are out of phase by the angle θ formed by the loop surfaces of the two optical loops, the difference signal between the two detection signals is determined by the rotation of the two optical loops. The resulting signal cancels out the noise that occurs and does not cancel out the azimuth signal component.

Therefore, by rotating the rotary shaft vertically, an azimuth signal output device capable of outputting a correct azimuth signal can be obtained.

(Embodiment) FIGS. 1, 2, and 3 are diagrams showing the components of an embodiment of the present invention, and FIG. 1 shows an optical fiber loop wound in order to form an optical loop with an optical fiber. FIG. 2 is a block diagram mainly showing the optical system of the optical fiber gyro, and FIG. 3 is a block diagram of the electrical processing system for determining the azimuth angle.

In FIG. 1, bobbin IA and bobbin IB have a common rotation axis M, and are fixed to each other at an angle of approximately 90 degrees. An optical fiber is wound around the bobbin IA in the direction of arrow A to form a first optical fiber loop, and an optical fiber is wound around the bobbin IB in the direction of arrow B to form a second optical fiber loop.
forming an optical fiber loop. Inside the bobbin IB, there is a light source 2, a modulation element 4A, a B detector and an APC.
A circuit block 6 is provided.

As shown in FIG. 2, light emitted from a light source 2 such as a superluminescent diode passes through an optical fiber and reaches a branch coupler (optical directional coupler) 3a.
a, and the branched lights are guided to branch couplers 3b and 3c through optical fibers, respectively. The light emitted from the branching coupler 3b passes through the optical fiber, reaches the polarizer 5A, and becomes linearly polarized light, and the light that passes through the optical fiber and reaches the branching coupler 3d, which enters the 0-branching coupler 3d, is split into two there. This branched light is input from both ends of the first optical fiber loop 21A. A part of the optical fiber loop 21A is wound around a modulation element 4A such as a piezo element, and expands and contracts in accordance with the expansion and contraction of the modulation element 4A.

Proceed in the opposite direction through the optical fiber loop 21A,
The light emitted from both ends enters the branching coupler 3d, enters the second optical fiber, passes through the polarizer 5A and the branching coupler 3b, enters the detector 6A, and is photoelectrically converted.

On the other hand, the light emitted from the branching coupler 3c is branched into two, one of which passes through the optical fiber and reaches the polarizer 5B, becomes linearly polarized light, and passes through the optical fiber and reaches the branching coupler 3e. The other is monitored as described below. Branch coupler 3
The light branched into two by e is inputted from both ends of the second optical fiber loop 21B. A part of the optical fiber loop 21B is wound around the modulation element 4B, and is expanded and contracted in accordance with the expansion and contraction of the modulation element 4B. The light that travels in the opposite direction through the optical fiber loop 21B and is emitted from both ends of the loop 21B enters the branching coupler 3e, then enters the same optical fiber, passes through the polarizer 5B and the branching coupler 3C, and enters the detector 6B. and is photoelectrically converted.

Further, of the light emitted from the light source 2, the monitor light branched by the branching coupler 3c passes through the optical fiber and reaches the detector 6C. The photoelectric conversion signal of the detector 6C is A
P C (Automatic Power Control)
l) is input to the circuit 6D, and the APC circuit 6D is connected to the light source 2.
The drive current of the light source 2 is controlled so that a constant amount of light is emitted from the light source 2.

As shown in FIG. 3, the photoelectric conversion signals of the detectors 6A and 6B are amplified by amplifiers 31A and 31B, and then enter the detectors 32A and 32B.

The modulator 33 outputs a modulation signal that drives the modulation elements 4A and 4B, and also outputs a modulation signal that drives the modulation elements 4A and 4B, and also outputs a modulation signal that drives the modulation elements 4A and 4B.
A reference signal synchronized with the modulation signal is input to 2B.

The detection signals synchronously detected by the detectors 32A and 32B enter the differential amplifier 34 and are differentially amplified.

This differential amplified signal is transmitted to, for example, the first optical fiber loop 2. This is an azimuth signal that changes depending on the azimuth of the loop plane of the IA. The output signal of the differential amplifier 34 is input to an arithmetic processing device as described below, and is subjected to arithmetic processing.

Although an optical fiber gyro is specifically shown here, it goes without saying that in addition to this optical fiber gyro, all optical gyros that detect angular velocity using the Sunac effect, such as a ring laser gyro that forms an optical loop with a reflecting mirror, can be considered in the same way. Of all the optical fiber gyros, the phase modulation type optical fiber gyro has the highest accuracy and is desirable.

The operation of this embodiment will be explained in detail below.

Figure 4 shows the direction of rotational angular velocity (Ω) and optical fiber loop 2.
1 (which can be considered as one of the optical fiber loops 21A and 21B in FIG. 2) and a loop plane (a plane defined by the X-axis and Y-axis). The loop plane (X-Y plane) of the optical fiber loop 21 is in a vertical plane (in a plane perpendicular to the horizontal plane H), and the Y axis perpendicular to the horizontal plane H is the rotation axis of the optical fiber loop 21. Yes, direction in the horizontal plane of the loop surface of the optical fiber loop 21 (X direction)
and the north-south direction (N-3 direction) in the horizontal plane form an angle θ.

At this time, the rotational angular velocity of the earth detected by the optical fiber loop 21 is Ωsinθ, and the optical fiber loop 21
By rotating the detector 1 around the Y axis, the angle θ, that is, the orientation can be determined from its output (detector 6A or 6B in FIG. 2).

Here, Ω is the rotational angular velocity at a certain latitude on the earth,
If its latitude is λ, then Ω. If Ω is the angular velocity of the earth at the equator, i.e. 15 degrees/hour, then Ω=Ω. cos λ.

Therefore, the signal obtained from the detector 32A is S.

, if the signal obtained from the detector 32B is 32, then Sl
=Kl(Ωsin'(θ+φ,)+ψ,) ・(
1) Sz=Kx(Ωcos (θ+φ,)+ψri・
(2) becomes.

However, Kl, Kz... Constant ψ1, ψ8... Error term φ such as noise, drift, etc.
, . . . The angle from θ=0 (encoder zero point) to true north. Therefore, the output signal S of the differential amplifier 34 that outputs the differential signals of the detectors 32A and 32B is expressed by equation (1), ( 2) From the formula, s=s, -5z -f1 ward lower (," ・5ln(θ+φt 12)+
(Kl ψ1- to 2ψt) (3).

Since K1 and K2 are constants that include the drive voltage of the modulation elements 4A and 4B, as is clear from equation (3), noise, drift, etc. are caused by the first optical fiber loop 21A and the second optical fiber loop 21B. By adjusting the drive voltages so that the same occurs, it is possible to have K1ψ1− and 2ψ2=0.

Therefore, in this case, equation (3) is S, -S.

=!・5in(θ+φt rx )α−tamilo−□・・・・・・(3゛).

By the way, considering the first optical fiber loop 21A,
When θ#π-φ2.2π-φ, KΩ sin θ=0, and the plane of the fiber loop faces the north-south direction (N-3 direction). Which of θ=π−φ and 2π−φ should be north is determined appropriately by focusing on the zero point when the signal changes from negative to positive, or the zero point when the signal changes from positive to negative. , equation (3) for Ωsinθ in equation (1)
”) is delayed by α in phase. In other words, when θ=π−φ2.2π−φE, equation (3
') (DS+St is f muff "+Kz" 5
It has a value of in(-α).

Therefore, it is necessary to adjust the offset through astronomical observation, etc. before actually measuring true north.

For example, the measurement is performed at a point where the true north is known in advance, and the processing system is stored so as to subtract the value of θ such that St 5t=O -φ2+α as an offset.

That is, the signal St St in equation (3) has a period corresponding to one rotation around the Y axis of the first fiber loop 21A, and a phase of the signal corresponds to one rotation of the first fiber loop 21A around the Y axis.
It represents the rotation angle of A, that is, the orientation (the angle α is a constant).

Note that since the loop plane of the first optical fiber loop 21A that becomes S, -O is in the north-south direction, true north can also be found from the direction of the loop plane where the signal S of the first optical fiber loop becomes zero. I do not care.

FIG. 5 is a perspective partial cutaway view showing an example of the orientation sensor using the present invention, and inside the cylindrical frame 50 is the optical system of the optical fiber gyro shown in FIGS. 1 and 2. An optical system block 51 housing the same, a slip ring 52, and a scale disc 53 for detecting rotation angle are fixedly aligned with the rotation axis of a motor 54 fixed to the frame 50. The output terminal of the differential amplifier 34 of the optical system block 51 is connected to the conductor portion 52a provided in a ring shape on the slip ring 52 through wiring (not shown), and a brush (not shown) fixed to the frame 50 is connected to the conductor portion 52a. As a result, even if the optical system block 51 is rotated, the output signal of the differential amplifier 34 can be extracted to the outside of the frame 50 via the brush 9. If necessary, power can be supplied to the optical system block 51 from outside the frame 50 via the slip ring 52. Further, an angle detector for reading the scale of the scale disc 53 is fixed to the frame 50, and together with a part of the arithmetic processing device to be described later, constitutes a so-called low-return encoder. Further, a reference telescope 55 is fixedly provided on the upper surface of the frame 50, and a fixing portion for fixing to a tripod 56 is provided on the lower surface.

The telescope 55 is rotatable in a vertical plane relative to the frame 50, and the frame 50 is rotatable around a vertical axis relative to the tripod 56.

Furthermore, the signals extracted to the outside of the frame 50, that is, the output signal of the differential amplifier 34 and the rotation angle signal from the angle detector (not shown), are input to an arithmetic processing device and subjected to predetermined arithmetic processing. Then, the direction of the target as determined by the reference telescope 55 is displayed on the display device.

These arithmetic processing units and display devices can be arranged on the side or top surface of the frame 50.

The operation of the orientation sensor shown in FIG. 5 will be described below, focusing on the operation of the arithmetic processing unit.

First, the measurer uses the telescope 55 to aim at the target whose direction he or she wants to measure, and then turns on the measurement start switch of the arithmetic processing unit (not shown).The motor 54 starts rotating.The arithmetic processing unit measures the angle from the angle detector. In order to read the angle of rotation of the telescope 55 from the reference direction, an initial measurement is performed by the ON signal of the measurement start switch.

When the motor 54 rotates, the signal S shown in FIG. 6(a) is output from the detector 32A (see FIG. 2) in the optical system block 51.
, is output. This signal is a signal obtained by adding 1ψ1 to the noise component to the original measurement signal. 1 for noise component
ψ1 includes a steady offset (not shown) and instantaneous noise ψ1' due to uneven rotation of the motor or the like. Also, from the detector 32B (see Fig. 2), as shown in Fig. 6(b)
A signal St is output. This signal is also a signal obtained by adding χψ2 to the noise component to the original measurement signal. Similar to 1 ψ1 in the noise component, 2ψ8 in the noise component is also
This includes a steady offset (not shown) and instantaneous noise ψ2' due to uneven rotation of the motor, etc.

Since the differential amplifier 34 (see FIG. 3) outputs the difference signal between the detectors 32A and 32B, the differential amplifier 34 outputs the difference signal between the signals SA and S, as shown in FIG. ) outputs the signal. That is, if the noise components ψ1° and ψ8° of the signals SA and S are approximately equal, the signal in FIG. 6(c) becomes a sine wave 5A-1 as shown in equation (3).

Here, the angle between the phase α in equation (3) and the optical axis of the telescope 55 and the encoder zero point (5 when the optical axis is set to true north)
This corresponds to θ=−φ, where 1=0. ) is removed as an offset by the above-mentioned correction means.

Therefore, the time when the measurement start switch is turned on is shown in Figure 6 (
If the position c) and the position of the zero point of the encoder are Po in FIG. 6(c), then the position pt where the signal 5a-1 crosses the zero point from negative to positive direction (this corresponds to true north)
The rotation angle θ up to is determined by the signal from the angle detector. (Incidentally, the position P where the signal 5a-S crosses the zero point from positive to negative direction is adjusted to correspond to due south).

The arithmetic processing unit calculates the offset from the rotation angle θ mentioned above.
The values θ and -θα obtained by subtracting φ + α (denoted as θα) are output as the final results. That is, θ and −θα are angles corresponding to the direction of the target object as determined by the telescope 55.

(Effects of the Invention) As described above, according to the present invention, it is possible to obtain an azimuth signal output device that is not affected by noise signals caused by uneven rotation during rotation.

[Brief explanation of the drawing]

Figure 1 is a perspective view mainly showing the structure of the bobbin around which the optical fiber loop is wound, Figure 2 is a block diagram mainly showing the optical system of the optical fiber gyro, and Figure 3 is a block diagram of the electrical processing system for determining the azimuth angle. , Figure 4 shows the rotational angular velocity of the earth (
Ω) and the loop surface of the optical fiber loop 21, FIG. 5 is a perspective partial cutaway view showing an example of the orientation sensor using the present invention, and FIGS. 6(a), (b), (c) is a waveform diagram for explaining the principle of removing noise in an embodiment of the present invention. (Explanation of symbols of main parts) 2...Light source, 6A, 6B...Detector, 21
A... First optical fiber loop, 21B... Second optical fiber loop, 32A, 32B... Detector, 34
...Differential amplifier. Applicant Nippon Kogaku Kogyo Co., Ltd.

Claims (2)

[Claims] (1) In an azimuth signal output device using an optical gyro, two optical loops are arranged so as to have a common rotation axis and form a predetermined angle θ (0 degrees < θ < 180 degrees), and the 2
Measurement light from a light source is made to enter each of the two optical loops in opposite directions from both ends thereof, and the light emitted from both ends of each of the two optical loops is transmitted to a separate light receiving element corresponding to each optical loop. An azimuth signal output device comprising: a pair of optical gyros that perform photoelectric conversion; and obtaining an azimuth signal based on a difference signal between output signals of the pair of optical gyros. (2) The azimuth signal output device according to claim (1), wherein the predetermined angle θ is approximately 90 degrees.