JP2964217B2 - Fiber optic gyro - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber gyro suitable for use as an gyro for an aircraft, a ship, an automobile, and the like.

[0002]

2. Description of the Related Art An optical fiber gyro is widely used as a device for measuring an angular velocity, and has advantages of being small in size and having high reliability. The optical fiber gyro is configured to measure an angular velocity using a Sagnac effect (also called a Sagnac effect) of light. Examples of the interference type optical fiber gyro include a phase modulation system, a serrodyne modulation system, and a digital modulation system, and these will be described.

First, an optical fiber gyro of a phase modulation system will be described with reference to FIG. The optical fiber gyro device includes a light emitting device 1 such as a semiconductor laser and a light emitting diode, a light receiving device 2 for converting detection light into a current, an optical fiber loop 3 formed by winding one optical fiber a plurality of times, and a polarizer 4. It has first and second couplers 5 and 6 for combining or splitting light propagating through an optical fiber, and a phase modulator 8 provided at one end of the optical fiber loop 3.

The light output from the light emitter 1 passes through a first coupler 5 and a polarizer 4 and is split into two propagating lights by a second coupler 6 and propagates in the optical fiber loop 3 in opposite directions. . That is, one propagates clockwise through the optical fiber loop 3, and the other propagates counterclockwise.

When an angular velocity Ω is applied to the optical fiber loop 3 from the outside, the optical fiber loop 3
A phase difference Δθ is generated between lights propagating in the opposite directions. Such a phase difference Δθ is called a Sagnac phase difference,
It is proportional to the angular velocity Ω and is expressed by the following equation.

[0006]

Equation 1 Δθ = (2πDL / λc) Ω

Here, D is the loop diameter of the optical fiber loop 3, L is the length of the optical fiber loop 3, λ is the wavelength of the light output from the light emitter 1, c is the speed of light, and Ω is the optical fiber loop 3. Represents the angular velocity around the central axis of the loop.

According to the phase modulation method, the light propagating clockwise and the light propagating counterclockwise in the optical fiber loop 3 are phase-modulated by the phase modulator 8, respectively. The light E _C propagating clockwise and the light E _CC propagating counterclockwise in the optical fiber loop 3 are expressed as follows at both ends of the optical fiber loop 3.

[0009]

E _C = E ₀ sin (ωt−Δθ / 2 + β ₀ ) E _CC = E ₀ sin (ωt + Δθ / 2 + β _T )

Where E ₀ is the amplitude, ω is the angular frequency with respect to the frequency of the light, t is the time, Δθ / 2 is the phase difference caused by the Sagnac effect, and β ₀ and β _T are generated by the phase modulator 8. The phase difference. The phase difference β ₀ of the light E _C propagating clockwise is generated by phase-modulating at the exit of the optical fiber loop 3 after propagating clockwise through the optical fiber loop 3, and the light propagating counterclockwise. The phase difference β _T of E _CC is generated in the light that has been phase-modulated at the entrance of the optical fiber loop 3 and then propagated counterclockwise through the optical fiber loop 3.

The two propagation lights E _C and E _CC are combined by the second coupler 6, and the interference light is detected by the light receiver 2 via the first coupler 5. The intensity I of the interference light detected by the light receiver 2 is represented by the following equation.

[0012]

Equation 3] I = 2E ₀ ² _{[1 + cos (Δθ + β T} -β 0) ] = 2E ₀ ² [1 + cos (Δθ + Δβ)] ^{_{= 2E 0 2 (1 + cosx}} )

Here, Δβ = β _T −β ₀ , x = Δθ + Δβ
It is. In the method without phase modulation (Δβ = 0), since the intensity I of the interference light detected by the light receiver 2 is a function of the cosine value cos Δθ of the phase difference Δθ, if the input angular velocity Ω is small, the intensity I of the interference light Phase difference Δ
θ cannot be obtained. In the phase modulation method (Δβ ≠ 0), since the operating point is in a region where the slope of the sine curve is large, an accurate phase difference Δθ can be obtained even when the input angular velocity Ω is small.

[0014] Phase modulation is performed using a sine wave of the reference frequency of the angular frequency omega _m. In such a case, the phase differences β _T and β ₀ are represented by the following equations.

[0015]

## EQU4 ## β _T = β sin (ω _mt + ω _m · τ / 2) β ₀ = β sin (ω _mt −ω _m · τ / 2)

Here, β is a constant, and τ is the time required for light to propagate through the optical fiber loop 3. From this equation, 2
The difference Δβ = β _T −β ₀ between the two phase differences β _T and β ₀ is obtained as follows.

[0017]

[Number 5] _{Δβ = β T -β 0 = 2βsin} (ω m · τ / 2) · cosω m t = zcosω m t

Here, z is called a phase modulation degree and is expressed by the following equation.

[0019]

## EQU6 ## z = 2β sin ω _m τ / 2

The phase modulation degree z changes according to the magnitude of the voltage signal supplied to the phase modulator 8. By substituting the phase difference Δβ in the equation (5) into the equation (3), the following equation is obtained.

[0021]

Equation 7] I = 2E ₀ ² _{[1 + cosΔθ · {J 0 (} z) +
2Σ _{k = 1} J _2k (z) cos2k · ω _m t｝ -2sinΔ
θ · Σ _{k = 0} J _{2k + 1} (z) sin (2k + 1) ω _mt ]

E _O is a constant related to the intensity of light, ω _m is the angular frequency given by the phase modulator 8, z is the degree of phase modulation, and J ₀ , J ₁ , J ₂ ,. , T is time.

The equation of Equation 7 is expressed as the following Equation 8.

[0024]

[Equation 8] _{I = I 0 -I 1 sinω m} t + I 2 cos2ω
_{m t-I 3 sin3ω m t} + I 4 cos4ω m t + ··
・

Here, I ₀ , I ₁ , I ₂ , I ₃ , and I ₄ are represented by the following equation (9). Here, I ₀ is a DC component, and I _0
1 is called a first harmonic component, I ₂ is called a second harmonic component, I ₃ is called a third harmonic component, and the like.

[0026]

I ₀ = 2E ₀ ² ｛1 + J ₀ (z) cosΔθ｝ I ₁ = 4E ₀ ² J ₁ (z) sin Δθ I ₂ = 4E ₀ ² J ₂ (z) cos Δθ I ₃ = 4E ₀ ² J ₃ (Z) sin Δθ I ₄ = 4E ₀ ² J ₄ (z) cos Δθ

In the optical fiber gyro device of the phase modulation system, the intensity I of the interference light received by the photodetector 2 is not only the term of cos Δθ but also sin Δθ as shown in the equation (9).
When the input angular velocity Ω is small and the value of the sagnac phase difference Δθ is small, an accurate value can be obtained by taking out the term of the sin Δθ and obtaining the sagnac phase difference Δθ.

Referring back to FIG. The optical fiber gyro device further includes a current-voltage converter 7, a signal generator 11, a synchronous detector 12, and a signal processing unit 13. The current-voltage converter 7 converts the current signal output from the light receiver 2 into a voltage signal, and outputs the voltage signal to the synchronous detection unit 12. Signal generator 1
Reference numeral 1 denotes a signal generator for generating a reference signal having an angular frequency of ω _{m, and} the frequency of the reference signal is multiplied by 2ω _m , 3ω _m , and 4ω
and a frequency multiplier for generating an _m pulse signal.

The synchronous detector 12 is supplied from the signal generator 11.
Angular frequency ω_m, 2ω_m, 3ω _m, 4ω_mSignal and
The voltage signal output from the current-voltage converter 7 is input.
First, a DC component I is obtained from the intensity signal I of the interference light._ORemove
You. Next, the angular frequency ω_m, 2ω _m, 3ω_m, 4ω_mNo faith
Signal to synchronously detect the intensity signal I of the interference light,
Minute I₁, 2nd harmonic component I_Two, Third harmonic component I_ThreeAnd 4 times harmonic
Minute I_FourAnd the like.

In order to calculate the sagnac phase difference Δθ using these signals, E ₀ , J
₁ (z), J ₂ (z), J ₃ (z), and J ₄ (z) may be deleted. For example, J ₁ (z) = J ₂ (z). Assuming that the maximum value among the modulation degrees z satisfying J ₁ (z) = J ₂ (z) is the optimum modulation degree z ₀ , z ₀ ≒ 2.63. Therefore, phase modulation may be performed by the phase modulator 8 so that the modulation factor z ≒ 2.63. As a result, the Sagnac phase difference Δθ is obtained using the two equations of Expression 9. This is calculated by the signal processing unit 13.

Next, a conventional serrodyne modulation type optical fiber gyro will be described with reference to FIG. The optical fiber gyro of the serrodyne modulation method is an improvement of the optical fiber gyro of the phase modulation method, and is configured to obtain a wider dynamic range than the optical fiber gyro of the phase modulation method.

Optical fiber gyro of serrodyne modulation system
In addition, a serrodyne modulator 9 is provided in addition to the phase modulator 8.
Have been killed. Propagating clockwise through optical fiber loop 3
Light E _CAnd the light E propagating to the left_CCIs due to the phase modulator 8
It is superposed on the phase modulation and further subjected to serrodyne modulation. Light fa
The light that has propagated through the evar loop 3 is the following number instead of the equation 2
It is represented by the equation of 10.

[0033]

E _C = E ₀ sin (ωt−Δθ / 2 + β ₀ + α _T ) E _CC = E ₀ sin (ωt + Δθ / 2 + β _T + α ₀ )

Α ₀ and α _T are phase differences generated by the serrodyne modulator 9 between the light propagating clockwise and the light propagating counterclockwise in the optical fiber loop 3. Receiver 2
The intensity I of the interference light detected by the following equation is expressed by the following equation.

[0035]

Equation 11] I = 2E ₀ ² _{[1 + cos (Δθ + β T} -β 0 + α 0 -α T) ] = 2E ₀ ² [1 + cos (Δθ + Δβ + Δα) ]

Here, Δβ is the phase difference generated by the phase modulator 8 and Δα is the phase difference generated by the serrodyne modulator 9. Δα is called the serrodyne phase difference.

[0037]

Δβ = β _T −β ₀ Δα = α ₀ −α _T

As is clear from the comparison between the equation (3) and the equation (11), in the serrodyne modulation method, the light intensity I of the interference light is obtained by substituting Δθ + Δα instead of Δθ in the equation (7). Can be Therefore, the DC component, the first harmonic component, the second harmonic component, the third harmonic component, and the like of the current signal output by the light receiver 2 are represented by the following equations corresponding to the equation (9).

[0039]

I ₀ = 2E ₀ ² ｛1 + J ₀ (z) cos (Δθ + Δα)｝ I ₁ = 4E ₀ ² J ₁ (z) sin (Δθ + Δα) I ₂ = 4E ₀ ² J ₂ (z) cos (Δθ + Δα ) I ₃ = 4E ₀ ² J ₃ (z) sin (Δθ + Δα) I ₄ = 4E ₀ ² J ₄ (z) cos (Δθ + Δα)

FIG. 16 shows the phase difference signals α ₀ and α _T generated by the serrodyne modulation and the serrodyne phase difference Δ
indicates α. As shown in FIG. 16A, the phase difference signals α ₀ , α
_T is a sawtooth wave having an amplitude of 2π and a period of T _S. As shown in FIG. 16B, the serrodyne phase difference Δα is a rectangular wave whose value alternates between α _S and α _S -2π. alpha _S is proportional to the slope 2 [pi / T _S of the sawtooth wave is expressed by the following equation.

[0041]

Α _S = 2πτ / T _S = 2πf _S τ

Here, T _S is the period of the serrodyne phase difference Δα, f _S (= 1 / T _S ) is the frequency of the serrodyne phase difference Δα, and τ is the time required for light to propagate through the optical fiber loop 3. .

In the serrodyne modulation method, sin (Δθ +
The propagation light is phase-modulated by the serrodyne modulator 9 so that Δα) = 0. Therefore, the serrodyne modulator 9
At the stable point due to the feedback loop including
Δθ. At this time, the gradient 2 of the sawtooth wave shown in FIG.
π / T _S is proportional to the Sagnac phase difference Δθ (that is, the angular velocity Ω).

If Δα = α _S = 2πτ / T _S , then Δθ = 2πτ / T _S ignoring the sign. By substituting this into the equation of Equation 1, the following equation is obtained.

[0045]

Ω = λcτ / DLT _S = λcτf _S / DL

Referring again to FIG. The optical fiber gyro further includes a signal generator 11, a synchronous detector 12, first and second integrators 15, 16, a counter 17, and a reset circuit 1.
8 and a 2π reference unit 19.

The synchronous detector 12 synchronously detects the formula 1 harmonic component I ₁ of the signal generator 11 the number by entering the reference signal outputted angular frequency omega _m than 13. Therefore, the synchronous detector 1
2, the first harmonic signal I ₁ is supplied to the first integrator 15. The second integrator 16 generates a ramp signal that increases with a gradient proportional to the serrodyne phase difference Δα.

On the other hand, the 2π signal generated by the 2π reference unit 19 is supplied to the reset circuit 18. The reset circuit 18 generates a 2π reset signal, and resets it when the value of the tilt signal of the integrator 16 increases to 2π. Thus, a serrodyne waveform signal as shown in FIG. 16A is generated from the second integrator 16, and the serrodyne waveform signal is supplied to the serrodyne modulator 9.

As described above, in the serrodyne modulation method,
Phase modulation is performed so that sin (Δθ + Δα) = 0. At this time, the output signal I ₁ of the synchronous detector 12 becomes zero. Therefore, at this time, the counter
The wave number of the serrodyne waveform as shown in FIG.
_S is required. From this frequency f _S , the angular velocity Ω is obtained by the equation (15).

Next, a conventional digital modulation type optical fiber gyro will be described with reference to FIGS. In the digital modulation system, the light propagating through the optical fiber loop 3 is phase-modulated by the phase modulator 8, whereby the intensity signal I of the interference light is converted into Δβ ₁ = + π / 2 and Δβ every time τ.
A phase difference Δβ that alternates with ₂ = −π / 2 is generated. Therefore, the intensity signal I of the interference light is given by Δβ =
By substituting ± π / 2, it is expressed as follows.

[0051]

I ₁ = 2E ₀ ² ｛1 + cos (Δθ + Δβ ₁ )｝ = 2E ₀ ² ｛1 + cos (Δθ + π / 2)｝ = 2E ₀ ² (1-sinΔθ) I ₂ = 2E ₀ ² ｛1 + cos (Δθ + Δβ ₂ ) ^{_{} = 2E 0 2 {1 +}} cos (Δθ-π / 2)} = 2E 0 2 (1 + sinΔθ)

Thus, the difference ΔI between the interference light intensity I when the phase difference is Δβ ₁ = + π / 2 and when the phase difference is Δβ ₂ = −π / 2
= I ₁ −I ₂ .

[0053]

Equation 17] _{ΔI = I 1 -I 2 = 2E} 0 2 (1-sinΔθ) -2E 0 2 (1 + sinΔθ) = -4E 0 2 sinΔθ

Since the right side of this equation does not include the phase difference Δβ generated by the phase modulator 8, the Sagnac phase difference Δ
θ can be obtained. Thus, according to the digital modulation method, the phase modulator 8 generates a phase difference Δβ = ± π / 2 that changes every time τ in the interference light I, and the phase difference is Δ
Light intensity I ₁ when β ₁ = + π / 2 and Δβ ₂ = −π /
The difference ΔI of the light intensity I ₂ at the time of ₂ is obtained, and from this, Δθ
Find the value of

The digital modulation method will be specifically described with reference to FIGS. According to the digital modulation method, the clockwise light Ecw has a phase difference β ₀ of, for example, FIG.
Is phase-modulated so that the periodic square wave of period 2τ and amplitude [pi / 4 as shown, as the light Eccw around left a rectangular wave as shown in the phase difference beta _T, for example, FIG. 18B Phase modulated. The phase difference β _T of the left-handed light Eccw has the same rectangular waveform as the phase difference waveform of the right-handed light Ecw, but is delayed by the time τ with respect to the phase difference of the right-handed light Ecw.

Thus, the difference between the phase difference β ₀ of the clockwise light Ecw and the phase difference β _{T of the} clockwise light Eccw, that is, the phase difference Δβ
= Β ₀ −β _T is a rectangular wave that alternately changes to + π / 2 and −π / 2 every time τ as shown in FIG. 18C.

FIG. 18D shows the phase x = Δθ + Δβ in the equation (3).
Represents the waveform. When the angular velocity Ω does not act on the optical fiber gyro, Δθ = 0, so that the waveform of the phase x in FIG. 18D matches the phase difference Δβ in FIG. 18C.

Next, referring to FIG. 19, the intensity I ₁ , Δβ ₂ of the interference light when the phase difference Δβ is Δβ ₁ = + π / 2 using the equation of equation 3 or the equation of equation 16 A method for obtaining the intensity I ₂ of the interference light when = −π / 2 will be described.

FIG. 19A is a graph of the equation (3), which is often used to represent the relationship between the phase difference x and the light intensity I. In such a graph, the horizontal axis represents the phase x (= Δθ + Δβ), and the vertical axis represents the intensity I (x) of the interference light. 19B and 19C shown on the lower side of FIG. 19A, the horizontal axis (vertical direction of FIG. 19A) is time, and the vertical axis (horizontal direction of FIG. 19A) is phase x (=
Δθ + Δβ). FIG. 19 shown on the right side of FIG. 19A
D and FIG. 19E show time on the horizontal axis (the horizontal axis direction in FIG. 19A).
The vertical axis (the vertical axis direction in FIG. 19A) is the intensity I of the interference light.

FIG. 19B shows a waveform of the phase x (= Δθ + Δβ) when the sagnac phase difference Δθ = 0, and corresponds to the waveform of FIG. 18C. FIG. 19D shows the intensity I of the interference light in such a case. Similarly, FIG. 19C shows the sagnac phase difference Δ
8 shows a waveform of a phase x (= Δθ + Δβ) when θ ≠ 0,
This corresponds to the waveform of FIG. 18D. FIG. 19E shows the intensity I of the interference light in such a case.

When the sagnac phase difference Δθ = 0, even if the value of the phase x alternates between + π / 2 and −π / 2 as shown in FIG. As shown in FIG. 19D, the value is constant (except for the spike-shaped protrusion).
However, when the sagnac phase difference Δθ ≠ 0,
As shown in FIG. 19C, the value of the phase x is alternately Δ
It changes to θ−π / 2 and Δθ + π / 2, and at this time, the intensity I of the interference light alternately changes every time τ (except for the spike-like protrusions) as shown in FIG. 19E.

In FIG. 19D, the value of the intensity I of the interference light is the time τ.
Each spike-shaped protrusion is provided when the value of the phase x shown in the waveform of FIG. 19B changes between −π / 2 and + π / 2, and the sine wave interference light of FIG. This is because the strength I increases. Similarly, in FIG. 19E, the interference light intensity I
Has a spike-like projection every time τ, because the value of the phase x shown by the waveform in FIG. 19C is Δθ−π / 2 and Δθ.
This is because when changing between + π / 2, the intensity I of the sinusoidal interference light in FIG. 19A increases.

In FIG. 19E, the rectangular wave at the high level indicates the intensity I ₂ of the interference light at the phase x = Δθ−π / 2, and the rectangular wave at the low level indicates the phase x = Δθ + π /
2 represents the intensity I ₁ of the interference light. Therefore, FIG.
The difference between the high level and the low level of the square wave corresponds to the deviation ΔI = I ₂ −I ₁ of the intensity of the interference light.

That is, the magnitude of the difference between the high level and the low level of the rectangular wave in FIG. 19E represents the right side of the equation (17). Thus, in the digital modulation method, the light intensity I in FIG.
A rectangular wave having the intensity I of the interference light shown in FIG. 19E is generated from the sine wave shown in FIG. 19E, and Δθ is obtained from the difference between the high level and the low level of the rectangular wave according to the equation (17).

Description will be made again with reference to FIG. The optical fiber gyro of this embodiment further includes a timing signal generator 21, a phase modulation signal generator 22, an AD converter 23, and a signal processor 2.
And 4. The timing signal generator 21 generates a timing signal having a period τ and outputs the generated timing signal to a phase modulation signal generator 22.
And to the signal processing unit 24. Phase modulation signal generator 2
2 generates a phase modulator drive signal for generating the phase differences β ₀ , β _T , Δβ as shown in FIGS. 18A, 18B and 18C.

On the other hand, the A / D converter 23 receives the voltage signal (shown in FIGS. 19D and 19E) from the current / voltage converter 7 and generates a digital signal indicating the intensity I of the interference light. The values I ₁ and I ₂ are supplied to the signal processing unit 24.
The signal processing unit 24 operates based on the timing signal from the timing signal generator 21 and generates the two values I ₁ and I ₁ .
₂ are alternately stored, and the expression of Expression 17 is subtracted. The angular velocity Ω is calculated from the obtained sagnac phase difference Δθ according to the equation (1).

[0067]

In the optical fiber gyro apparatus of the phase modulation system and the serrodyne modulation system, the input signal I of the synchronous detector 12 has only a sine wave component as shown in the equations (9) and (13). However, the input signal I has a large value even when the input angular velocity Ω is zero because of the cosine wave component. Therefore, the synchronous detector 12
However, it is difficult to increase the AC gain of the gyro signal, and the noise of the synchronous detector 12 directly becomes an error source of the gyro signal.

In the conventional optical fiber gyro apparatus of the phase modulation system, the output signal of the synchronous detector 12 is an analog signal including sin Δθ, which is inappropriate for the signal processing unit 13 to calculate the angular velocity Ω digitally. there were. Therefore,
It was difficult to obtain a gyro output Ω with high precision.

In an optical fiber gyro device of the conventional serrodyne modulation method, when the input angular velocity Ω is close to zero,
There is a disadvantage that the slope of the sawtooth waveform shown in FIG. 16A is small, and thus the serrodyne period T _S becomes large, making it difficult for the second integrator 16 to operate accurately as an integrator.

[0070] In the optical fiber gyro system of conventional serrodyne modulation method, when the input angular rate Ω is large, serrodyne period T _S is reduced, the serrodyne frequency f _S is close to the number of the phase modulation period f _m = ω _m / 2 π Drawback or lock-in. In the lock-in range, even if the input angular velocity Ω changes, the serrodyne phase difference Δα does not change at all, so that the input angular velocity Ω cannot be detected. To avoid such a lock-in phenomenon,
It is necessary to add a dither signal or the like which is an alternating wave signal and introduce a virtual input angular velocity Ω.

In the optical fiber gyro apparatus of the serrodyne modulation method, the serrodyne modulated signals α ₀ and α _T have a sawtooth waveform, and change sharply from 2π to 0. This is called flyback. However, in practice, the serrodyne modulation signals α ₀ and α _T cannot instantaneously change from 2π to 0, and may take several nanoseconds or less depending on the semiconductor switch used.
It takes about several hundred nanoseconds. An error caused by such a transition time is called a flyback error.

The serrodyne modulation signals α ₀ , α _T normally fly back to 0 when exactly 2π, but may fly back at a deviation from 2π. 2π
An error caused by flyback with a further deviation is referred to as a 2π error. Eliminating such 2π errors required a complex and separate control loop.

In the conventional fiber optic gyro apparatus of the serrodyne modulation method, the flyback error and the 2π error are not always exactly the same, but change. That is, there is a disadvantage that the random walk deteriorates and it is difficult to remove the error.

In the conventional optical fiber gyro of the digital modulation method, the period of the rectangular wave signals β ₀ and β _T used for phase modulation is 2τ (τ is the time required for light to propagate through the optical fiber loop 3). . Therefore, when the optical fiber loop 3 having a normal length is used, the frequency corresponding to the period 2τ is on the order of megahertz, and all the circuits used are high-frequency circuits. Therefore, it is necessary to take measures against electric noise and the like, and there is a disadvantage that the cost is higher than when a low-frequency circuit is used.

In view of the above, it is an object of the present invention to eliminate the disadvantages of the conventional optical fiber gyros of the phase modulation system, the serrodyne modulation system and the digital modulation system.

[0076]

According to the present invention, as shown in FIG. 1, for example, a light source, an optical fiber loop, a first propagating light and a second propagating light propagating in opposite directions in the optical fiber loop. A phase controller for changing a phase between the first propagating light and the second propagating light, and a photodetector detecting interference light between the first propagating light and the second propagating light. In an optical fiber gyro configured to obtain the angular velocity Ω from the sagnac phase difference Δθ generated in the intensity signal I of the interference light when rotating at an angular velocity Ω about the axis, the phase controller controls the interference light. Strength I
A reference phase difference Δβ and a ramp phase difference σ are generated in the signal of
The reference phase difference Δβ has a fixed period T, and the first and second times T _A and T _{B of} one period T become first and second reference phase differences Δβ _A and Δβ _B , respectively. The first and second reference phase differences Δβ _A and Δβ _B have opposite signs and have the same absolute value, and the ramp phase difference σ is controlled so as to cancel the sagnac phase difference Δθ and is fed back to the propagation light, The control voltage signal supplied to the phase controller to generate the reference phase difference and the ramp phase difference Δβ, σ has a phase difference Δβ at the first time T _A.
A has a first slope corresponding to _A + σ, and the second time T
_B has a second slope corresponding to the phase difference Δβ _B + σ,
One of the first and second slopes is negative and the other is positive, which results in a triangular delta serrodyne waveform signal that is bent at each of the first and second times T _A and T _B. And

According to the present invention, in the optical fiber gyro, the reference phase difference Δβ is Δβ _A = − (2n−1) π / 2 at the first time T _A , and n is a positive integer. At the time T _B , Δβ _B = + (2n−1) π / 2. In another example, the reference phase difference Δβ is defined as Δβ _A = − [(2n−) at the first time T _A , where n is a positive integer and δ is an arbitrary constant satisfying | δ | <π / 2. 1) π /
2 + [delta]], the second at time T _B Δβ _B = + [(2n
-1) π / 2 + δ].

[0078] According to the present invention, in an optical fiber gyro, one period of the delta serrodyne waveform signals the first time T _A and the sum of the second time T _B constant T = T _A
+ T _{B so} that the peak value of the delta serrodyne waveform signal does not exceed a predetermined allowable value.
Characterized in that it is configured such that the magnitude of the _A and the second time T _B is regulated.

[0079] According to the present invention, in an optical fiber gyro, a positive time in one period T of the delta serrodyne waveform signals T _+, a negative time T _- when that difference ΣT ₊ -ΣT of the integrated value _- or integrated value sigma (T of the difference ₊ -
T _-) the first time T _A and the second time based on T _B
Characterized in that the size is adjusted.

According to the present invention, in the optical fiber gyro, at the stable point of the control loop where the sagnac phase difference Δθ is canceled by the ramp phase difference σ, the positive time in one cycle T of the delta serrodyne waveform signal is obtained. Where T _{+ is} the negative time and T ₋ is the negative time,
₊ -ShigumaT _- or integrated value Σ of the difference - characterized by calculating the input angular rate Ω and turning angle based on (T _{+ -T).}

According to the present invention, in the optical fiber gyro, the positive time T ₊ and the negative time T _- are counted with pulses of a predetermined period, and the number of pulses is N ₊ and N respectively.
_- When the difference ΣN ₊ -ΣN of the integrated value _- characterized by calculating the input angular rate Ω and turning angle based on - the integrated value or the difference Σ (N _{+ -N).}

According to the present invention, in the optical fiber gyro, the control voltage signal supplied to the phase controller is a constant reference voltage signal V ^* corresponding to the reference phase difference and a lamp voltage signal corresponding to the lamp phase difference. becomes than the sum of the V _R, the lamp voltage signal V _R is the first time T value of the intensity I of the interference light in the _a I _a and the second intensity I of the interference light at the time T _B characterized in that it is produced by integrating the value voltage signal corresponding to the difference signal ΔI between I _B.

According to the present invention, in the optical fiber gyro, the intensity signal I of the interference light output from the light receiver is input and the difference signal ΔI = I _A −I of the intensity of the interference light is input.
Inputs an output signal V _R of the integrator and the integrator for integrating enter the signal processing unit and said voltage signal V ₀ which generates a voltage signal V ₀ corresponding to generate the delta serrodyne waveform signal _B And a delta serrodyne portion.

According to the present invention, in the optical fiber gyro, the signal processing section removes a DC component from the intensity signal I of the interference light and alternately outputs ± ΔI / 2 at times T _A and T _B.
A DC eliminator for generating an alternating signal that changes to an AC signal, an AC amplifier for AC amplifying an output signal of the DC eliminator, and a synchronous detector for obtaining a DC voltage signal V ₀ from the output signal of the AC amplifier. It is characterized by the following.

According to the present invention, in the optical fiber gyro, the delta serrodyne section includes a reference voltage signal V ^* having a positive or negative sign that alternates with each other at times T _A and T _B and a lamp voltage output from the integrator. characterized in that it comprises a delta serrodyne integrator for integrating the output signal of the adder and said adder for adding the signal V _R.

According to the present invention, an optical fiber gyro
And the reference voltage signal V^*Reference phase control unit that generates
Is provided, and the reference phase control unit operates at the first time T_ATo
Signal I of the above interference light_AAnd the second time T _B
The intensity signal I of the interference light at_BAverage I of₀Equivalent to
It is characterized in that it is generated by using a voltage signal.

According to the present invention, a first phase difference (reference phase difference) Δβ and a second phase difference (reference phase difference) are added to the interference light intensity signal I using a triangular waveform, that is, a delta serrodyne waveform signal. (Ramp phase difference) σ is generated. The phase x of the intensity signal I of the interference light is = Δθ + σ + Δβ. The reference phase difference Δβ is
It changes to constant values Δβ _A and Δβ _B having the same absolute value but different signs for each of the times T _A and T _B.

According to the present invention, the ramp phase difference σ is controlled so that Δθ + σ = 0. Therefore, at the stable point of the control loop, the sagnac phase difference Δθ is equal to the ramp phase difference σ. Further, the phase x of the intensity signal I of the interference light does not include the sagnac phase difference Δθ, and x = Δβ. Therefore, the position of a desired operating point can be selected by setting the reference phase difference Δβ to a predetermined value. That is, the operating point is always at a predetermined position on the sinusoidal curve regardless of the value of the sagnac phase difference Δθ. In this manner, the operating point at the stable point of the control loop can be set to a predetermined point in a region where the slope of the sine wave signal is large, so that the phase difference Δθ can be obtained with high sensitivity.

According to one preferred embodiment of the invention, the reference
The phase difference Δβ is a time T where n is an integer. _AThen Δβ_A= −
(2n-1) π / 2 and time T_BThen Δβ_B= + (2n-
1) Alternately to π / 2. In such a case, the intensity of the interference light
The phase x of the signal I is x = Δθ + σ + Δβ = Δθ + σ ±
(2n-1) π / 2. Also, the first operating point Δβ_ATo
Signal I of the interference light intensity_AAnd the second operating point Δβ_BTo
Signal I_BΔI is ΔI = 2I₀sin (Δθ +
σ). Is Δθ + σ = 0 at the stable point of the control loop?
Therefore, the signal difference ΔI is ΔI = 0.

The delta serrodyne waveform signal has one cycle T = T
_At time T _A of _A + T _B , it decreases to the right and decreases at time T _B
Is a triangular waveform increasing to the right. According to the present invention, the slope of the delta serrodyne waveform signal corresponds to the ramp phase difference σ, ie, the sagnac phase difference Δθ. As the input angular velocity Ω increases, one of the slopes of the delta cellodyne waveform signal increases. Since the period T of the delta serrodyne waveform signal is constant, the peak value of the delta serrodyne waveform signal exceeds the allowable value when one of the slopes increases. In the present invention, the period of the delta serrodyne waveform signal T = T _A + T
The _B constant, time T _A in 1 period T, is configured to adjust the length of the T _B. As a result, even if the slope of the delta cellodyne waveform signal increases, the peak value falls within the allowable value.

According to the example of the present invention, one cycle T (= T_A+
T_BThe time T in)_A, T_BIs corrected by the correction time Δt
I do. For example, time T_AIs corrected for half cycle T / 2
Increase or decrease by the time Δt and correspondingly the time T_BTo
Decrease or increase by the correction time Δt with respect to the half cycle T / 2
You. The deviation time Δt is, for example, one cycle T (= T _A
+ T_BThe time during which the delta serrodyne waveform signal in) is positive
T₊And the time T that is negative _-Set to be proportional to the difference ΔT
I do.

According to one preferred embodiment of the invention, the reference
The phase difference Δβ is a time T where n is an integer. _AThen Δβ_A= −
[(2n-1) π / 2 + δ] and time T_BThen Δβ_B= +
[(2n-1) π / 2 + δ] alternately. That is,
In this example, the reference phase difference Δβ is exactly ± (2n−1) π /
There is no need to control to be 2. In such cases, interference
The phase x of the light intensity signal I is x = Δθ + σ + Δβ + δ = Δ
θ + σ ± [(2n−1) π / 2 + δ]. Also the first
Operating point Δβ_ASignal I of the interference light intensity at_AAnd the second
Operating point Δβ_BSignal I at_BΔI is ΔI = 2I
₀sin (Δθ + σ + δ) · cosδ. Control loop
Since Δθ + σ = 0 at the stable point of the loop, the signal difference ΔI is ΔI
= 0.

[0093]

FIG. 1 shows a configuration example of an optical fiber gyro according to the present invention. The optical fiber gyro of this example is
A light emitting device 1 as a light source, a light receiving device 2 for converting received light into a current signal, an optical fiber loop 3, a polarizer 4, two couplers 5 and 6, a current / voltage converter 7 for converting a current signal into a voltage signal, A phase controller 8 'for controlling the phase of light propagating through the optical fiber loop 3;
1, an integrator 32, a delta serrodyne section 33, an angular angular velocity calculation section 34, a switching signal generation section 35, and a reference phase control section 36.

Here, the concept of the optical fiber gyro according to the present invention will be described. In the optical fiber gyro according to the present invention, the phase controller 8 'causes the interference light intensity signal I to generate two phase differences, that is, a reference phase difference Δβ and a ramp phase difference σ. First, the reference phase difference Δβ will be described.

According to this example, the reference phase difference Δβ is equal to the time T _A
And T _B alternately, and at time T _A , Δβ _A = −
(2n-1) π / 2 , Δβ at time T _{B B} = + (2n-
1) It becomes π / 2.

The cycle T of the reference phase difference Δβ is T = T _A + T _B
Is constant, but the times T _A and T _B are different except when the input angular velocity Ω = 0, and generally T _A ≠ T _B. This will be described later in detail. The period T is sufficiently longer than the time τ required for the propagating light to propagate through the optical fiber loop 3. For example, it may be several tens to several hundred times the time τ.

Although n is a positive integer, in the following, n =
Explanation is made as 1. Equation 3 gives Δβ _AAnd Δβ_BAssign
Then, an expression similar to Expression 16 is obtained. In addition, constant 2
E₀ ^Two= I₀And put.

[0098]

Equation 18] I _A = I _{0 [1 + cos (Δθ + Δβ A} ) ] = I ₀ [1 + cos (Δθ-π / 2) ] _{= I 0 (1 + sinΔθ)} I B = I 0 _{[1 + cos (Δθ + Δβ B} ) ] = I ₀ [1 + cos (Δθ + π / 2)] = I ₀ (1−sinΔθ)

When the reference phase difference is Δβ _A = −π / 2 and Δ
When the difference ΔI between the intensity signals I of the interference light when β _B = + π / 2 is obtained, an expression similar to Expression 17 is obtained.

[0100]

Equation 19] _{ΔI = I A -I B = I} 0 (1 + sinΔθ) -I 0 (1-sinΔθ) = 2I 0 sinΔθ ΔI / 2 = I 0 sinΔθ

Description will be made with reference to FIG. FIG. 2 is a view similar to FIG. That is, FIG. 2A is a graph of Expression 3 and is often used to represent a relationship between the phase difference x and the intensity I of the interference light. In such a graph, the horizontal axis represents the phase difference x (= Δθ
+ Δβ), and the vertical axis indicates the intensity I (x) of the interference light. FIG. 2A
2B and 2C shown on the lower side of FIG. 2, the horizontal axis (the direction of the vertical axis in FIG. 2A) is time, and the vertical axis (the direction of the horizontal axis in FIG. 2A) is the phase difference x.
(= Δθ + Δβ). FIG. 2 shown on the right side of FIG. 2A
In FIGS. 2D and 2E, the horizontal axis (horizontal direction in FIG. 2A) is time, and the vertical axis (vertical direction in FIG. 2A) is the intensity I of the interference light.

Circles A and B on the curve in FIG. 2A indicate operating points when the sagnac phase difference Δθ = 0, and circles A ′ and B ′
Indicates an operating point when the sagnac phase difference Δθ ≠ 0.

FIG. 2B shows the waveform of the phase x (= Δθ + Δβ) when the sagnac phase difference Δθ = 0, and FIG. 2C shows the phase x (= Δθ + Δβ) when the sagnac phase difference Δθ ≠ 0.
3 shows the waveforms of FIG. FIG. 2D shows the intensity I of the interference light when the sagnac phase difference Δθ = 0, and similarly, FIG. 2E shows the intensity I of the interference light when the sagnac phase difference Δθ ≠ 0.

As shown in FIGS. 2B and 2D, when the sagnac phase difference Δθ = 0, the phase x (= Δθ + Δβ =
[Delta] [beta]) is -π alternately every time T _A and T _B as described above
As shown in FIG. 2D, the intensity I of the interference light becomes a constant value (except for the spike-shaped protrusions) because the rectangular wave changes to // 2 and + π / 2.

However, as shown in FIG. 2C and FIG. 2E, when the sagnac phase difference Δθ ≠ 0, as shown in FIG. 2C, the value of the phase x is alternately ΔT every time T _A and T _B.
changes in θ-π / 2 and Δθ + π / 2, the intensity I at this time interference light (with the exception of spike-like protrusions) as shown in FIG. 2E alternately changes each time T _A and T _B .

The high level of the rectangular wave shown in FIG.
θ + Δβ _A = represents Δθ-π / 2 the intensity I _A of the interference light when the, low level of the square wave phase x = Δθ + Δβ _B = Δ
It represents the intensity I _B of the interference light when the θ + π / 2. Therefore,
The difference between the high and low levels of the rectangular wave in FIG. 2E corresponds to the deviation ΔI = I _A -I _B. That is, the magnitude of the difference between the high level and the low level of the rectangular wave in FIG. 2E represents the right side of Expression (19).

In FIG. 2D, the value of the intensity I of the interference light is the time T _A.
And T has a spike-like protrusions each _B, fig 2B
The value of the phase waveform x indicated by x is x _A = Δθ + Δβ _A and x _B =
This is because when changing between Δθ + Δβ _B , the operating point moves on the sine wave of FIG. 2A from A to B or from B to A, respectively, and the intensity I of the interference light increases. Similarly, the value of time T _A and T _B of the intensity I of the interference light by Figure 2E
Each of the spike-shaped projections has a value of a phase waveform x shown in FIG. 2C where x _A = Δθ + Δβ _A and x _B = Δθ + Δ
When changing between β _B , the operating point moves on the sine wave of FIG. 2A from A ′ to B ′ or from B ′ to A ′, respectively, and the intensity I of the interference light increases. Because.

Next, the ramp phase difference σ will be described. According to the present invention, instead of calculating the difference ΔI between the high level and the low level of the rectangular wave in FIG. 2E and calculating the phase difference Δθ using the equation (19), the reference phase difference A ramp function phase difference σ is generated in addition to Δβ. In such a case, the following expression is obtained instead of the expression of Expression 18 and Expression 19.

[0109]

I _A = I ₀ [1 + cos (Δθ + Δβ _A + σ)] = I ₀ [1 + cos (Δθ−π / 2 + σ)] = I ₀ [1 + sin (Δθ + σ)] I _B = I ₀ [1 + cos (Δθ + Δβ _B + σ) )] = I ₀ [1 + cos (Δθ + π / 2 + σ)] = I ₀ [1-sin (Δθ + σ)]

[0110]

Equation 21] _{ΔI = I A -I B = 2I} 0 sin (Δθ + σ) ΔI / 2 = I 0 sin (Δθ + σ)

According to the present invention, which will be described later in detail,
The ramp phase difference σ is controlled so that Δθ + σ = 0. Therefore, at the stable point of the control loop of this example, the Sagnac phase difference Δθ is equal to the ramp phase difference σ, ignoring the sign.

[0112]

## EQU22 ## Δθ = −σ

This is substituted into the equations (20) and (21) to obtain the interference light intensity signals I and I at the stable points of the control loop.
A deviation signal ΔI and an amplitude ΔI / 2 are obtained.

[0114]

I _A = I _B = I ₀ ΔI = ΔI / 2 = 0

When the intensity phase signal I of the interference light is further generated with a ramp phase difference σ in addition to the reference phase difference Δβ, the discussion described with reference to FIG. 2 holds. At the stable point of the control loop, since Δθ + σ = 0, the phase x is x = Δθ + σ + Δβ
= Δβ, and the Sagnac phase difference Δθ = 0 in the example of FIG.
The state is the same as in the case of. Accordingly, the operating point returns to the circles A and B on the curve in FIG. 2A, and the phase x = as shown in FIG. 2B.
Δβ = ± π / 2, and the intensity signal I of the interference light has a constant value I _{0 as} shown in FIG. 2D.

When the input angular velocity Ω changes and the sagnac phase difference Δθ changes, the operating point moves to the circles A ′ and B ′ on the curve in FIG. 2A, and the phase x changes as shown in FIG. 2C and the intensity of the interference light changes. Although the signal I changes as shown in FIG. 2E, the operating point moves to the stable points A and B again by controlling the ramp phase difference σ. Regardless of the value of the sagnac phase difference Δθ, at the stable point of the control loop, the operating points A and B are located at the fixed points of the region where the sine wave gradient is the largest, so the operating point moves in the region where the sine wave gradient is small. A better sensitivity can be obtained as compared with the case.

Referring back to FIG. The signal processing unit 31
Output signal V of the current-to-voltage converter 7_IAnd the amplitude ΔI / 2
Voltage signal V corresponding to₀Generate Figure 4A shows the signal processing
Input signal V of the unit 31_IOf the intensity I of the interference light corresponding to
FIG. 4B shows the output signal V ₀Of ΔI / 2 corresponding to
Show the shape. Note that at the stable point of the control loop,
As shown, ΔI / 2 = 0 and therefore the voltage signal V₀
Is 0.

[0118] Such a voltage signal V ₀ is the integration time by the integrator 32, the integrated value V _R is the delta serrodyne 3
3 is supplied. The delta serrodyne unit 33 calculates the integral value V _R
Is generated, that is, a delta serrodyne wave signal V _S is generated.

The phase controller 8 'controls the phase of the light propagating through the optical fiber loop 3 using the delta serrodyne wave signal V _S. Thereby, a phase difference x is generated in the intensity signal I of the interference light. The phase x of the intensity signal I of the interference light is expressed as follows.

[0120]

X = Δθ + α _S = Δθ + σ + Δβ = Δθ + σ
± (2n-1) π / 2

Here, Δθ is a sagnac phase difference generated by the input angular velocity Ω, and α _S is a delta serrodyne phase difference generated by the delta serrodyne wave signal V _S. Further, σ is a ramp phase difference generated by the ramp signal included in the delta serrodyne wave signal V _S , and Δβ is a reference phase difference generated by the reference signal included in the delta serrodyne wave signal V _S.

As described above, the reference phase difference Δβ is equal to the time T _A.
And changes in [Delta] [beta] _A and [Delta] [beta] _B every T _B. The phase of the intensity signal I of the interference light at time T _A is x _A , the phase difference of the delta serrodyne is α _SA , the phase of the intensity signal I of the interference light at time T _B is x _B , and the phase difference of the delta cellodyne is _Let it be α _SB . These are represented as follows:

[0123]

Equation 25] _{x A = Δθ + α SA =} Δθ + σ + Δβ A = Δθ + σ- (2n-1) π / 2 x B = Δθ + α SB = Δθ + σ + Δβ B = Δθ + σ + (2n-1) π / 2

As described later, the ramp phase difference σ is
It can be obtained from the slope of the delta serrodyne wave signal V _{S or} the like. Angle velocity calculation unit 34 obtains the lamp retardation σ or Sagnac phase difference Δθ from the serrodyne wave signal V _S, further calculates the angular velocity input Omega.

The switching signal generating unit 35 operates at times T _A , T _B
Alternately generating a switching signal V _C of the period T = T _A + T _B which code is changed for each. The reference phase controller 36 generates a voltage signal V ^* that contributes to the slope of the serrodyne wave signal V _S.

The configuration and operation of the signal processing section 31 according to the present embodiment will be described with reference to FIGS. As shown in FIG. 3, the signal processing unit 31 includes a DC remover 31-1, an AC amplifier 31-2, and a synchronous detector 31-3. The signal processing unit 31 generates an output signal V ₀ that corresponds to the rectangular-wave signal [Delta] I / 2 as shown in Figure 4B receives the output signal V _I-mentioned current-to-voltage converter 7 shown in FIG. 4A as described above It may be constituted as follows.

[0127] The output signal V _I of the current-voltage converter 7 Figure 2D
Alternatively, it corresponds to the intensity signal I of the interference light shown in FIG. 2E.
That is, the intensity signal I of the interference light time T _A and T _B number every 2
0 changes to I _A and I _B shown in formula. As apparent from the numerical formula 20, an intermediate value of I _A and I _B is I _0. Accordingly, as shown in FIG. 4B, by subtracting the constant I ₀ from the intensity signal I of the interference light, square-wave signal changes to + [Delta] I / 2 and -.DELTA.I / 2 alternately every time T _A and T _B [Delta] I
/ 2 is obtained.

[0128] DC remover 31-1 removes the DC component I ₀ from the output signal V _I of the current-voltage converter 7. FIG. 4C shows the waveform of the output signal V _I ′ of the DC remover 31-1. The waveform of the intensity signal I of the interference light output from the current / voltage signal converter 7 actually has a spike-like projection when the rectangular wave is switched between the high level and the low level as shown in FIG. 2D or 2E. Have. Therefore, the waveform of the output signal V _I ′ of the DC remover 31-1 actually has a spike-shaped projection corresponding to the waveform. In the waveform of the output signal V _I ′ of the DC remover 31-1 shown in FIG. 4A, such spike-shaped protrusions are omitted for convenience of description.

If the rectangular wave signal V _I ′ of FIG. 4C is synchronously detected, a value proportional to the amplitude ΔI / 2 can be obtained. In this example, however, the signal passes through the AC amplifier 31-2 in order to achieve higher accuracy. Let it. FIG. 4D shows the output signal V of the AC amplifier 31-2.
_I ″. The rectangular wave signal V _I ′ is AC-amplified by the AC amplifier 31-2, and the time T becomes as shown in FIG. 4D.
An AC waveform V _I ″ whose sign changes alternately for each of _A and T _B is obtained. The AC amplifier 31-2 has a band-pass filter, thereby removing spike-like protrusions rich in high frequency. , A slight phase delay T as shown in FIG.
_F occurs.

[0130] The output signal V _I of the AC amplifier 31-2 "is supplied to the synchronous detector 31-3, are synchronously detected by the time T _A, the switching signal V _C which code is changed alternately every T _B. Figure 4E is an output signal V _I of the synchronous detector 31-3 '"
3 shows the waveforms of FIG. Synchronous detector 31-3 may be a circuit having a function of inverting the polarity by T _B for example time. DC component V ₀ which such signals V _I '"is proportional to the amplitude [Delta] I / 2.

Thus, the signal processing section 31 generates a DC voltage signal V ₀ proportional to the amplitude ΔI / 2, and
To supply.

[0132] The integrator 32 integrates the such DC voltage signal V ₀ time, supplies the resultant integrated signal V _R to the delta serrodyne unit 33. The signal processing section 31 of this example is configured by the AC amplification method as described above, but may be configured by the conventional synchronous detector 12 if a required gain is obtained.

[0133] above, the control loop is the description of a case not yet reached a stable point, when the control loop has reached a stable point, the output signal V _I of the current-voltage converter 7 Figure 4A
A constant value I _{0 as} shown by the broken line of FIG.
The output signal V _I -1 'is a constant value 0 rather than the square wave shown in FIG. 4C. Therefore, the output signal V ₀ of the signal processing unit 31 becomes zero.

The configuration and operation of the delta cellodyne unit 33 of this embodiment will be described with reference to FIGS. Delta serrodyne unit 33, as shown in FIG. 5, having a T _A / T _B switcher 33-1 and adder 33-2 and delta serrodyne integrator 33-3. T _A / T _B switcher 33-1
Are the switching signal V _C supplied from the switching signal generator 35 and the voltage signal V _C supplied from the reference phase controller 36.
^*, And at time T _A , as shown in FIG.
V ^*, to generate a time T _B in the + V ^* to become square wave signal ± V ^*.

The adder 33-2 adds the integration signal V _R supplied from the integrator 32 and the rectangular wave signal ± V ^* supplied from the T _A / T _B switcher 33-1. as shown, generates a square wave signal ± V ^* + V _R. That is, the time T _A in -V ^* + V _R, the signal of the time T _B in the + V ^* + V _R becomes the value is obtained. The value of the integrated signal V _R will vary, the size -V ^* + V _R of the signal at time T _A is always configured to be negative. Therefore, the adder 33-2
Code is changed to positive and negative alternately every output signal ± V ^* + V _R of time T _A and T _B

[0136] Delta serrodyne integrator 33-3 integrates the output signal ± V ^* + V _R from the adder 33-2 times, 6
As shown in C, a triangular wave signal, that is, a delta cellodyne waveform signal is generated. At time T _B positive signal value + V ^* +
Positive slope from integrating the V _R (> 0) is produced, the negative slope is generated from integrating the time T _A in the negative signal value _{^{-V * + V R (<0}} ). As apparent from FIG. 6, the voltage signal V ^* supplied from the reference phase control unit 36 mainly contributes to the slope of the delta cellodyne waveform.

[0137] Delta Cerro Delta serrodyne waveform signal V _S generated by the dyne integrator 33-3 is supplied to the phase controller 8 ', the light propagating through the optical fiber loop 3 is phase-modulated. As a result, a delta cellodyne phase difference α _S = Δβ + σ is generated in the intensity signal I of the interference light.

According to the present invention, phase modulation is performed using a triangular wave, that is, a signal having a delta serrodyne waveform as shown in FIG. 6C. Therefore, a flyback error occurs when a signal having a conventional serrodyne waveform is used. Nothing.

Next, the delta serrodyne phase difference α _S , particularly the reference phase difference Δβ and the ramp phase difference σ, and the voltage signals V ^* and V _R
Ask for a relationship. The voltage phase conversion coefficient of the phase controller 8 'k, the integration time of the delta serrodyne integrator 33-3 T _I
And then, d [alpha] _SA / dt inclination of the delta serrodyne phase angle at time T _A, the inclination of the delta serrodyne phase angle at time T _B and dα _SB / dt, which are expressed as follows.

[0140]

Equation 26] _{dα SA / dt = k (-V} * + V R) / T I dα SB / dt = k (+ V * + V R) / T I

The delta therodyne phase differences α _SA and α _SB are obtained by multiplying the slope of the delta therodyne phase angle by time τ, and are as follows. τ is the time required for light to propagate through the optical fiber loop 3.

[0142]

[Number 27] ^{_{α SA = k (-V * +}} V R) τ / T I = -kV * τ / T I + kV R τ / T I α SB = k (+ V * + V R) τ / T I = + kV * τ / T _I + kV _R τ / T _I

When this equation is compared with the equation (25), the following is obtained.

[0144]

[Number 28] ^{_{Δβ A = -kV * τ / T}} I Δβ B = + kV * τ / T I σ = kV R τ / T I

As is apparent from this equation, the reference phase difference Δ
β _A and Δβ _B are proportional to the voltage signal V ^* . Here, in order to obtain the reference phase difference Δβ = ± (2n−1) π / 2, the voltage signal V ^* is set as follows.

[0146]

(29) kV ^* τ / T _I = (2n−1) π / 2

The ramp phase difference σ is proportional to the output signal V _R of the integrator 32. Until the delta serrodyne control loop reaches the stable point, Δθ + σ ≠ 0, and the output signal V ₀ of the signal processing unit 31 is V ₀ ≠ 0. Accordingly, such a signal V ₀ generates an integrated signal V _R via the integrator 32,
A ramp phase difference σ is generated as shown in Expression 26.
According to this example, such a ramp phase difference σ is controlled so that Δθ + σ = 0, that is, the output signal V ₀ of the signal processing unit 31 becomes zero.

Next, referring to FIG. 7, two times T _A and T _B
Will be described. If the times T _A and T _B are constant, there is a disadvantage that if the input angular velocity Ω acts, the value of the serrodyne wave signal V _S increases and exceeds the allowable value. For example, when T _A = T _B = T / 2 and the sagnac phase difference Δθ = 0, the delta serrodyne waveform is an isosceles triangle, and the peak value of the serrodyne wave signal V _S is constant. However, if T _A ≠ T _B or the sagnac phase difference Δθ ≠ 0, the serrodyne wave signal V _S
Peak value increases or decreases every period T, and exceeds a permissible value.

[0149] As described with reference to FIGS. 6B and 6C, the inclination of the delta serrodyne waveform, time T _A in -V
^* + Is a V _R, which is the time the T _B V ^* + V _R. The output signal V _R of the integrator 32 is not constant, but may be assumed to be constant within one cycle T. Therefore, when comparing the absolute values of such inclinations, the following is obtained.

[0150]

[Number 30] _{^{| V * + V R |>}} | -V * + V R |

Therefore, if T _A ≒ T _B , the time point P ₁
At a time point P ₃ after one cycle T from the cellodyne wave signal V _S
Is displaced to the + side. When the output signal V _R increases, the absolute value on the left side of the equation (30) increases and the absolute value on the right side decreases. Therefore, the cellodyne wave signal V _S
Is increasingly shifted to the + side, and increases to near the allowable value of the cellodyne wave signal V _S.

Therefore, in this example, the cellodyne wave signal V _S
T _A and T so that the peak value of
_B is controlled. In general, when the equation of Equation 30 is satisfied,
The time T _A by the increase in time T _B than the half period T / 2 to less than a half period T / 2, it is possible to prevent the increase of the peak value of the serrodyne wave signal V _S.

As shown in FIG. 7A, the first half of one cycle is time T _A , and the second half is time T _B. According to this example, both ends (time points P ₁ , P ₃ , P ₅ ) of the period T are fixed in time, but the intermediate time points P ₂ , P ₄ (approximately T / 2 periods) are temporally fixed. Be changed. That is, switching from one period T to the next period T is made at preset method, switching from time T _A to time T _B in the one period T is variably controlled.

As shown in FIG. 7B, the delta serrodyne wave
Shape signal V_SIs positive T₊Is a positive value, for example +1, negative
Time T_-Is a negative value, for example, -1. When positive
Interval T ₊And the time T that is negative_-Are generally not equal. One cycle
The positive and negative time T at T₊> T _-In the case of delta cello
The dyne waveform as a whole is deviated in the + direction (upward).
Conversely, the positive and negative time T₊<T_-In the case of
Rodine waveform is shifted in the negative direction (downward) as a whole.
I have.

[0155] Therefore, positive time is long T _+> T than negative time in one period T _- in the case of, slower switching point P _2, P ₄ in the next cycle. That is, to increase the time T _A may be reduce the time T _B. Thereby, the delta serrodyne waveform is displaced as a whole in the negative direction (downward),
Time points P ₃ and P ₅ are slightly displaced downward.

For example, as shown in FIG. 7C, the time T _A is increased by a correction time Δt with respect to the half cycle T / 2, and the time T _A is increased.
_B may be reduced by the correction time Δt with respect to the half cycle T / 2. Such a correction time Δt is, for example, a difference ΔT = T ₊ −T ₋ between positive and negative times T ₊ and T ₋ in one cycle as follows.
May be set to a value proportional to.

[0157]

Δt = K _T ΔT

Here, K _T is a proportional constant. As described above, the present embodiment is configured to correct the T _A / T _B switching point in the next cycle back and forth by the correction time Δt proportional to the positive / negative time difference ΔT in one cycle. Thus, according to this example, the delta serrodyne waveform can always be stabilized as a whole near the center position of one cycle T.

Here, as an example of a method of stabilizing the serrodyne wave signal V _S , a method of obtaining the correction time Δt using the positive / negative time difference ΔT = T ₊ −T ₋ in one cycle has been described. Obviously, other methods are possible within the range.

The configuration and operation of the angular velocity calculator 34 will be described with reference to FIG. As shown in FIG. 8, the angular / angular velocity calculation unit 34 of this example includes a positive / negative discriminating circuit 34-1, a positive / negative pulse generator 34-2, and three up / down counters 34-.
3, 34-4 and 34-5. Positive / negative discriminating circuit 34
-1 inputs the output signal V _S of the delta serrodyne portion 33 as shown in FIG. 6C or FIG. 7A, and determines the sign of the sign. The positive / negative discrimination circuit 34-1 generates a signal whose sign alternates between positive and negative as shown in FIG. 7B.

The positive / negative pulse generator 34-2 has a time τ_CNo
Inputs the lock signal and the output signal of the positive / negative discrimination circuit 34-1
Then time T₊Then the period τ_CGenerates a positive pulse signal of
Time T _-Then the period τ_CTo generate a negative pulse signal. Week
Period τ_CIs several tenths of the period T of the delta cellodyne waveform
It may be up to several hundredths. The sign changes to positive or negative
Period τ_CPulse signal has three up-down cows
And supplied to the counters 34-3, 34-4, and 34-5.

Up / down counters 34-3, 34-
Reference numerals 4 and 34-5 input the output pulse signal of the positive / negative pulse generator 34-2 and count the number of positive / negative pulses and the difference therebetween. The number of positive and negative pulses is set to N ₊ and N ₋ , and the difference is set to ΔN.

[0163]

[Number 32] ΔN = N ₊ -N _-

The time T ₊ during which the delta serrodyne waveform signal V _S is positive is equal to τ _C N ₊ , and the time T ₋ during which the delta cellodyne signal V _S is negative is τ _C
N _- equal to. Therefore, the time difference ΔT = T ₊ −T ₋ is τ _C Δ
Equal to N.

[0165]

３３T = τ _C ΔN

The time T ₊ during which the delta serrodyne waveform signal V _S is positive and the time T ₋ during which it is negative are determined by the slope dα _SA / d of the delta serodyne waveform signal V _S expressed by the equation (25).
t, δα _SA / dt. Being equal such tilting, i.e., if _{dα SA / dt = δα SA /} dt, is positive or negative time equal T ₊ = T _- become.

Now, consider the relationship between the ramp phase difference σ and the slope of the delta cellodyne waveform signal V _S. Time difference Δ
T = T ₊ −T ₋ is the difference d between the two inclination angles shown in the equation (26).
It is related to the _{α SA / dt-dα SA /} dt. Such a difference is, as apparent from the equation (26), a ramp phase difference σ = kV
_It is proportional to _R τ / T _I. Therefore, the following relationship is established from the equation (28).

[0168]

Σ = K _S ΔN

K _S is a constant determined by the entire system. By using this relationship, the expression of Expression 22, and the expression of Expression 1, the input angular velocity Ω can be obtained from the positive / negative pulse number difference ΔN.

First, the first up / down counter 34-3
Will be described. First up / down counter 34-
3 counts the positive / negative pulse number difference ΔN and holds the count value ΔN. Such a count value ΔN is reset every predetermined time. Therefore, a new count value ΔN is output every predetermined time. From the count value ΔN, the expression of Expression 34, the expression of Expression 28,
The input angular velocity Ω is obtained by using the equations of Equation 22 and Equation 1.

Next, a second up-down counter 34-4
Will be described. Second up / down counter 34-
4 finds the turning angle. The turning angle is obtained by integrating the angular velocity Ω with time. Therefore, the turning angle is obtained by integrating the positive and negative pulse number differences ΔN. The second up / down counter 34-4 calculates an integrated value ΣΔN of the positive / negative pulse number difference ΔN. Such an integrated value ΣΔN is equivalent to the integrated value of the angular velocity Ω. Therefore, similarly, Equation 34
The turning angle can be obtained by using the expression of Expression 32, the expression of Expression 28, the expression of Expression 22, and the expression of Expression 1.

Finally, the third up / down counter 34-
5 will be described. Third up / down counter 34
-5 counts the positive / negative pulse number difference ΔN, but resets it every time T. Therefore, the pulse deviation ΔN of the cycle (cycle) immediately before the current cycle (cycle) is always held and supplied to the switching signal generator 35.

FIG. 9 shows the structure of the switching signal generator 35 of this embodiment.
This is shown. The switching signal generator 35 includes a reference clock 35
-1 and a switching signal generator 35-2. Standard
The lock 35-1 has a period τ_CPulse τ_CAnd Delta Seroda
In-wave period T (= T_A+ T _B) And a pulse T equal to
A period τ sufficiently smaller than the period T of the lutha cellodyne wave_C0No pa
Lus τ_C0Generate Pulse τ_CIs the angular angular velocity calculator 3
4 is supplied to the positive / negative pulse generator 34-2.

The switching signal generator 35-2 is provided with a positive / negative pulse number difference ΔN output from the third up / down counter 34-5 of the angular angular velocity calculating section 34 and the reference clock 35.
-1 and the pulse T and the pulse τ _C0 supplied from
Generating a switching signal V _C of the time T _A and T period T code is changed for each _B. The step of generating the switching signal V _C includes the above-described calculation of the correction time Δt. In this example, the correction time Δt is obtained by the following equation instead of the equation (31).

[0175]

Δt = γτ _C0 ΔN

Here, the constant γ is an arbitrary positive constant smaller than 1, but a fraction is selected from a small number so as to be convenient for counting pulses. The time τ _C0 is any time sufficiently smaller than T / 2, but a value that satisfies τ _C0 ≦ τ _C and is convenient to be generated by the reference clock 35-1 is selected.

[0177] While the third up-down counter pulse number difference between the positive and negative from 34-5 .DELTA.N is not supplied, the time T _A of the switching signal V _C, although T _B is constant T _A = T _B = T / 2 When the positive / negative pulse number difference ΔN is supplied from the third up / down counter 34-5, the correction time Δt =
The switching time T _A / T _B changes before and after the middle time of one cycle by γΔNτ _C0 .

[0178] T _+> T _- in the case, i.e., .DELTA.N> 0 in the case, the time T _A half period T / 2 from the time Δt = γΔNτ
_{C 0} , and the time T _{B is set} to a time Δt =
It is shortened by γΔNτ _C0 . T ₊ <T _- In the case of, that is, Δ
In the case of N <0, the time T _A is set to the time Δ from the half cycle T / 2.
t = γΔNτ _C0 only short and longer by the time T _B time than the half period T / 2 Δt = γΔNτ _C0.

The configuration and operation of the reference phase control unit 36 of this embodiment will be described with reference to FIGS. The reference phase controller 36 is configured to always generate a constant reference voltage signal V ^* . According to the present example uses a constant voltage signal I ₀ described with reference to FIG. 4A for generating a reference voltage signal V ^*.

As shown in FIG. 10, the reference phase control unit 36
Represents a sampling mechanism 36-1 and an average value calculating section 36-2.
And a reference voltage calculation unit 36-3. Sampling mechanism
36-1 is the interference light supplied from the current-voltage converter 7;
When the intensity signal I is input and the time T _AAnd time T_BDried in
Light intensity signal I_AAnd I_BIs sampled. Also
Time T_A, T_BSpikes when switching
The intensity signal 2I of the interference light corresponding to₀Sample
You.

FIG. 11 shows the intensity signal I of the interference light shown in FIG. 2E.
Is enlarged. Time T a voltage corresponding to the intensity signal I _A of the interference light at _A V _A, a voltage corresponding to the intensity signal I _B of the interference light at the time T _B and V _B.
The time T _A, the voltage corresponding to the spike-like projections at the time of switching of T _B and V _F.

As described with reference to FIG. 2E,
According to the two interference light intensity signals I_A, I_BIntermediate value of
That is, the average value is always a constant value I₀It is. Therefore such constant
Value I ₀By using the voltage value corresponding to
Pressure signal V^*Can be generated.

[0183] voltage value V _A average value calculating unit 36-2 for suitable sampling number N _S, the average value of V _B V _AM = (1
/ N _S ) ΣV _A , V _BM = (1 / N _S ) ΣV _B
Further, the average value (V _AM + V _BM ) / 2 of both is calculated. Such voltage average value (V _AM + V _BM ) / 2 corresponds to the intermediate value I ₀ . Mean value V _FM voltage value V _F for more average calculator 36-2 suitable sampling number _{N S = (1 / N S} ) Σ
To calculate the V _F. Such a voltage average value V _FM corresponds to the peak value 2I ₀ of the spike-shaped protrusion.

Therefore, by using the voltage average value (V _AM + V _BM ) / 2 corresponding to the intermediate value I ₀ or the voltage average value V _FM corresponding to the peak value 2I ₀ , an accurate and stable reference voltage signal V ^* Is obtained.

[0185] The reference voltage calculating unit 36-3, two voltage average value V _AM, and multiplied by a constant 1 / mu to the sum of V _BM, the deviation [Delta] V _FM and the resulting value of the voltage average value V _FM Ask for. Such an operation is represented as follows.

[0186]

ΔV _FM = V _FM − (V _AM + V _BM ) / μ

Here, the constant 1 / μ is a constant close to 1.
Reference voltage calculating portion 36-3 to integration time by amplifying a further such deviation [Delta] V _FM, adds the initial value V ^{* 0} to the integral value.
Thereby, a voltage signal V ^* is obtained.

[0188]

V ^* = V ^{* 0} + ∫ΔV _FM dt

FIG. 12 shows a control loop including the reference phase controller 36. The reference voltage calculator 36-3 includes a coefficient unit 36-3A for multiplying the sum of the two voltage average values V _AM and V _BM by a constant 1 / μ close to 1 and an adder 36-3B for calculating the equation (36).
And an amplifier 36-amplifying the output signal of the adder 36-3B.
An integrator 36-3D for time-integrating the output signals of the 3C and the amplifier 36-3C, and an adder 36-3 for performing the operation of Expression 37.
E may be provided.

When 1 / μ = 1, V ^* = V _FM / 2. In such a case, the reference phase difference Δβ is | Δβ | = (2n−
1) (π / 2). If μ ≠ 1, the reference phase difference Δβ obtained is | Δβ | = μ (2n−1) (π / 2). Since the constant 1 / μ can be set to an appropriate value other than 1, the reference phase difference Δβ can be set in a wide range around (2n−1) (π / 2). Initial value V ^{* 0}
Is arbitrary, but if the value is selected to be close to the reference voltage value V ^* used first, the response at the time of startup becomes faster.

In the above example, the case where the reference phase difference Δβ is expressed as Δβ = ± (2n−1) π / 2 using a positive integer n has been described. Further, for simplicity of description, n = 1 has been described as needed, for example, in Expression 20 and Expression 21. n may be a positive integer, but practically n = 2
Is convenient. When n = 2, the following expression is obtained instead of the expression of Expression 20 and Expression 21.

[0192]

Equation 38] I _A = I _{0 [1 + cos (Δθ + Δβ A} + σ) ] = I ₀ [1 + cos (Δθ-3π / 2 + σ) ] = I ₀ [1-sin (Δθ + σ)] I _B = I ₀ [1 + cos (Δθ + Δβ _B + σ)] = I ₀ [1 + cos (Δθ + 3π / 2 + σ)] = I ₀ [1 + sin (Δθ + σ)]

[0193]

Equation 39] _{ΔI = I A -I B = -2I} 0 sin (Δθ + σ) ΔI / 2 = -I 0 sin (Δθ + σ)

In general, when n is an odd number, the equation (20) and the equation (21) are obtained. When n is even, the equation (36) and the equation (37) are obtained. Therefore, when n is an even number, it is necessary to provide a sign inverter in the control loop.

Another example of the present invention will be described with reference to FIG. In the above example, the reference phase difference Δβ obtained by multiplying ± π / 2 by an odd number (2n−1) is used. However, according to the present invention, the reference phase difference Δβ is not necessarily Δβ =
It is not necessary to satisfy ± (2n-1) π / 2. According to the present invention, at the stable point of the control loop, the sagnac phase difference Δθ
Irrespective of the value of x, the phase x of the interference light intensity signal I is x =
Δβ. Therefore, at the stable point of the control loop, the operating point is always at a predetermined position on the sinusoidal curve regardless of the value of the sagnac phase difference Δθ.

For example, when Δβ = ± π / 2,
At the stable point of the control loop, the operating point is always the phase x = ± π on the sinusoidal curve regardless of the value of the sagnac phase difference Δθ.
/ 2 position.

To obtain a predetermined resolution, the phase x = Δ
β, that is, the operating point must be in a region where the slope of the sinusoidal curve is sufficiently large, but the phase, that is, the operating point must be x = Δβ = ± (2n−1) π / 2. There is no. An example in which an “arbitrary phase” close to ± (2n−1) π / 2 is used as the reference phase difference Δβ will be described.

[0198]

Δβ = ± [(2n−1) π / 2 + δ]

Δ is an arbitrary constant satisfying | δ | <π / 2. Here, it is assumed that n = 1 for simplification. The intensity signal I of the interference light is represented by the following equation, similarly to the equations of Equations 20 and 21.

[0200]

Equation 41] I _A = I _{0 [1 + cos (Δθ + Δβ A} + σ) ] = I ₀ [1 + cos (Δθ-π / 2-δ + σ) ] = I ₀ [1 + sin (Δθ-δ + σ) ] I _B = I ₀ [1 + cos (Δθ + Δβ _B + σ)] = I ₀ [1 + cos (Δθ + π / 2 + δ + σ)] = I ₀ [1-sin (Δθ + δ + σ)]

[0201]

Equation 42] _{ΔI = I A -I B = I} 0 [sin (Δθ-δ + σ) + sin (Δθ + δ + σ) ] _{= 2I 0 sin (Δθ + σ} ) · cosδ ΔI / 2 = I 0 sin (Δθ + σ) · cosδ

Assuming that the equation of Equation 22 is satisfied at the stable point of the control loop, the equation of Equation 40 is as follows.

[0203]

ΔI = I _A −I _B = 0 ΔI / 2 = 0

FIG. 13 shows an example in which “arbitrary phase” is used as the reference phase difference Δβ. FIG. 13 is a diagram similar to FIG. 2, and circles A and B in FIG. 13A represent a state where the control loop has reached a stable point, that is, a case where the equation of Expression 22 is established. FIG.
The circles A ′ and B ′ in 3A indicate a state where the sagnac phase difference Δθ has changed and the control loop has not yet reached a stable point.
FIG. 13B shows the phase x = when the control loop has reached a stable point.
Δβ = ± (π / 2 + δ), which is substantially equal to, for example, 2π / 3. FIG. 13D shows the intensity signal I of the interference light in such a case. FIG. 13C shows the phase x = Δθ + Δβ + σ = Δθ ± (π / 2 + δ) + σ when the control loop has not reached the stable point.
FIG. 13E shows the intensity signal I of the interference light in such a case.

Thus, the present invention can be applied as long as the stable points A and B of the control loop are in the region where the slope of the sinusoidal curve is sufficiently large. For example, the AC gain of the signal processing unit 31 may be increased. When using “arbitrary phase” to which δ is added, the gain of the signal system is simply calculated as 1 / c
osδ times. For example, the AC gain of the signal processing unit 31 may be increased by 1 / cos δ times.

Although the embodiments of the present invention have been described in detail, it will be apparent to those skilled in the art that the present invention is not limited to the above-described embodiments and can adopt various other configurations without departing from the spirit of the present invention. It will be easily understood.

For example, FIG. 1 shows a block diagram of a configuration example of the optical fiber gyro of the present invention, but this is merely an example, and the signal processing unit 31, the integrator 32, the delta cellodyne unit 33, the angular angular velocity calculation The unit 34, the switching signal generating unit 35, the reference phase control unit 36, and the like may be appropriately configured by combining a CPU, a storage device, an A / D converter, a D / A converter, and the like.

In the example shown in FIG. 1, two couplers 5,
6, polarizer 4, phase controller 8 'etc. have been described as separate elements, but some of these elements may be replaced by a single optical integrated circuit.

[0209]

According to the conventional optical fiber gyro of the phase modulation system, a synchronous detector for detecting the second and fourth harmonics and a harmonic canceling circuit having a relatively large AC gain are used for controlling the degree of modulation. However, the optical fiber gyro of the present invention does not require them, and thus has an advantage that the size and cost can be reduced.

In the conventional phase modulation type optical fiber gyro, the intensity signal I of the interference light is obtained as an analog signal including sin θ or cos θ, and the sagnac phase difference Δθ is obtained from the analog signal I. Therefore, there was a defect that the linearity and accuracy were poor. In the conventional digital modulation scheme to generate a phase difference ± [pi / 2 which digitally changes the intensity signal I of the interference light, the two interference light intensity signal I _A, the difference between I _B [Delta] I = I _A -I _The difference signal ΔI is obtained as an analog signal including sin θ or cos θ, and thus has a disadvantage that linearity and accuracy are inferior as in the phase modulation method.

In the optical fiber gyro according to the present invention, the reference phase difference Δβ and the lamp phase difference σ are generated in the intensity signal I of the interference light, and the lamp phase difference σ is controlled so that Δθ + σ = 0, and the lamp phase difference σ is controlled. Sagnac phase difference Δθ from phase difference σ
= −σ. Therefore, in the present invention, since the ramp phase difference σ can be obtained as a digital signal, the angle and angular velocity can be calculated by a digital method, and the linearity and accuracy are good, and the error can be eliminated. Having.

In the optical fiber gyro according to the present invention, Δθ + σ = 0 at the stable point of the control loop, and the phase x of the interference light intensity signal I becomes x = Δβ, which is only the reference phase difference Δβ. Therefore, in the present invention, at the stable point of the control loop, regardless of the value of the sagnac phase difference Δθ, the operating point is always a predetermined point of the sine wave curve, so that there is an advantage that the linearity and accuracy are good and errors can be eliminated. Have.

In a conventional serodyne modulation type optical fiber gyro, a serrodyne waveform signal, that is, a sawtooth waveform signal is used in phase modulation.
That is, although there is a drawback that flyback becomes a problem, in the optical fiber gyro according to the present invention, since a delta serrodyne waveform signal, that is, a triangular waveform signal is used for phase modulation, a flyback problem does not occur. Has advantages.

In a conventional serodyne modulation type optical fiber gyro, an error due to flyback, for example, 2
Although there was a drawback that a π error occurred, the optical fiber gyro according to the present invention uses a delta serrodyne waveform signal, that is, a triangular waveform signal for phase modulation, so that there is no error caused by flyback. Having.

The conventional serodyne modulation type optical fiber gyro has a drawback that the random walk is deteriorated due to flyback. However, the optical fiber gyro according to the present invention has a delta serrodyne waveform signal, ie, Since the triangular waveform signal is used, there is an advantage that the random walk does not deteriorate due to flyback.

In the optical fiber gyro of the conventional serrodyne modulation method, when the input angular velocity Ω is close to zero, the slope of the serrodyne waveform, that is, the sawtooth wave, becomes smaller, the serrodyne cycle becomes longer, and the operation of the second integrator is reduced. Although there is a drawback that the inaccurate, period T = T _a + T _B of the delta serrodyne wave in the optical fiber gyro according to the invention for constant across, no such drawbacks.

The conventional serodyne modulation type optical fiber gyro has a drawback that a lock-in phenomenon occurs because two oscillation frequencies of a phase modulation frequency and a serodyne modulation frequency are used. However, the optical fiber gyro according to the present invention has a phase modulation frequency. Also, since the detection of the sagnac phase difference Δθ uses a single delta serrodyne wave signal, there is an advantage that the lock-in phenomenon does not occur.

The conventional digital modulation type optical fiber gyro is configured to generate a phase difference Δβ having one cycle of 2τ (τ is the time required for light to propagate through the optical fiber loop 3). Although a modulation frequency of the order of MHz was required, in the optical fiber gyro according to the present invention, since the period T of the delta serrodyne wave signal can be several tens to several hundreds of τ, several KHz to several tens KHz Therefore, there is an advantage that the manufacturing cost can be reduced because a modulation frequency in a low frequency range on the order of the above can be used.

[0219] In an optical fiber gyroscope according to the present invention, when obtaining the Sagnac phase difference Δθ from the delta serrodyne wave signal, several tenths from 1 to several hundred parts per period tau _C of the period T of the delta serrodyne wave signal Because it uses the pulse signal of
The number of pulses obtained per unit time is several tens to several hundreds times as large as that of the conventional serodyne modulation method. As a result, there is an advantage that the gyro signal Ω can be obtained with high accuracy and high resolution.

In the conventional digital modulation type optical fiber gyro, the reference phase difference Δβ = ± π is applied to the intensity signal I of the interference light.
/ 2, and an error occurs if the reference phase difference Δβ is not exactly equal to ± π / 2, so that the control and management of the reference phase difference Δβ = ± π / 2 Although the optical fiber gyro according to the present invention has a disadvantage that it is expensive, the reference phase difference Δβ is Δβ = ± (2n−1) π /
2, for example, Δβ = ± (2n−1) π /
There is an advantage that a value in a wide range near 2 can be set.

According to the present invention, there is an advantage that a high precision optical fiber gyro can be provided by eliminating the drawbacks or problems of the conventional optical fiber gyros of the phase modulation method, the serrodyne modulation method and the digital modulation method.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration example of an optical fiber gyro according to the present invention.

FIG. 2 is a diagram illustrating a relationship between an intensity signal of interference light and a phase difference in the optical fiber gyro according to the present invention.

FIG. 3 is a diagram illustrating a configuration example of a signal processing unit of an optical fiber gyro according to the present invention.

FIG. 4 is a waveform diagram for explaining the operation of the signal processing unit of the optical fiber gyro according to the present invention.

FIG. 5 is a diagram showing a configuration example of a delta serrodyne section of an optical fiber gyro according to the present invention.

FIG. 6 is a waveform diagram for explaining the operation of the delta serrodyne section of the optical fiber gyro according to the present invention.

FIG. 7 is a waveform chart for explaining a method of correcting the times T _A and T _B within one cycle of the optical fiber gyro according to the present invention.

FIG. 8 is a diagram showing a configuration example of an angular angular velocity calculation unit of the optical fiber gyro according to the present invention.

FIG. 9 is a diagram showing a configuration example of a switching signal generator of an optical fiber gyro according to the present invention.

FIG. 10 is an explanatory diagram showing a configuration example of a reference phase control unit of the optical fiber gyro according to the present invention.

FIG. 11 is a waveform diagram for explaining the operation of the reference phase control unit of the optical fiber gyro according to the present invention.

FIG. 12 is a diagram showing a configuration of a control loop including a reference phase control unit of the optical fiber gyro according to the present invention.

FIG. 13 is a diagram showing a relationship between an intensity signal of interference light and a phase difference in the optical fiber gyro according to the present invention.

FIG. 14 shows a conventional optical fiber gyro (phase modulation method).
FIG. 3 is a diagram showing an example of the configuration of FIG.

FIG. 15 is an explanatory diagram showing a configuration example of a conventional optical fiber gyro (serodyne modulation system).

FIG. 16 is a waveform chart for explaining the operation of a conventional optical fiber gyro (serodyne modulation method).

FIG. 17 is an explanatory diagram showing a configuration example of a conventional optical fiber gyro (digital modulation system).

FIG. 18 is a waveform chart for explaining the operation of a conventional optical fiber gyro (digital modulation method).

FIG. 19 is a diagram showing a relationship between an intensity signal of interference light and a phase difference in a conventional optical fiber gyro (digital modulation method).

[Explanation of symbols]

 Reference Signs List 1 light emitter 2 light receiver 3 optical fiber loop 4 polarizer 5, 6 coupler 7 current-voltage converter 8 phase modulator 8 'phase controller 9 serrodyne modulator 11 signal generator 12 synchronous detector 13 signal processing unit 15, Reference Signs List 16 integrator 17 counter 18 reset circuit 19 2π reference device 21 timing signal generator 22 phase modulation signal generation unit 23 A / D converter 24 signal processing unit 31 signal processing unit 32 integrator 33 delta serrodyne unit 34 angular angular velocity calculation unit 35 switching signal generator 36 reference phase controller

Continuation of front page (72) Inventor Takeshi Hojo 2-16-46 Minami Kamata, Ota-ku, Tokyo Inside Tokimec Co., Ltd. (56) References JP-A-5-332775 (JP, A) JP-A-3-170869 (JP, A) JP-A-6-307875 (JP, A) JP-A-4-223213 (JP, A) JP-A-3-130612 (JP, A) JP-A-3-503568 (JP, A) ( 58) Fields surveyed (Int. Cl. ⁶ , DB name) G01C 19/00-19/72

Claims (12)

(57) [Claims] A light source; an optical fiber loop; a phase controller for changing a phase between a first propagation light and a second propagation light propagating in opposite directions in the optical fiber loop; A light receiver for detecting interference light between the first propagation light and the second propagation light, the intensity signal of the interference light when the optical fiber loop rotates at an angular velocity Ω around the central axis of the loop. In the optical fiber gyro configured to obtain the angular velocity Ω from the sagnac phase difference Δθ generated in I, the reference phase difference Δβ and the ramp phase difference σ are generated in the signal of the intensity I of the interference light by the phase controller. The reference phase difference Δβ has a constant period T, and the first and second times T _A and T _{B of} one period T become first and second reference phase differences Δβ _A and Δβ _B , respectively. The first and second reference phase differences Δβ _A and Δβ _B are mutually However, the sign is opposite and the absolute value is equal, and the lamp phase difference σ is controlled so as to cancel out the sagnac phase difference Δθ and is fed back to the propagating light to generate the reference phase difference and the lamp phase difference Δβ, σ. The control voltage signal supplied to the phase controller has a first slope corresponding to the phase difference Δβ _A + σ at the first time T _A , and has a phase difference at the second time T _B Δβ _B + σ
, One of said first and second slopes being negative and the other being positive, whereby a triangular wave is bent at each of said first and second times T _A , T _B An optical fiber gyro, which is a delta serrodyne waveform signal of: 2. The optical fiber gyro according to claim 1, wherein the reference phase difference Δβ is Δβ _A = − (2n−1) π / 2 at the first time T _A , where n is a positive integer. Second
Time T _B in _{Δβ B = + (2n-1} ) optical fiber gyro characterized by comprising a [pi / 2. 3. The optical fiber gyro according to claim 1, wherein the reference phase difference Δβ is such that n is a positive integer and δ is | δ | <π.
/ Above the arbitrary constant satisfying 2 first time T _A in the [Delta] [beta] _A = - [(2n-1) π / 2 + δ ], [Delta] [beta] in the second time T _{B B} = + [(2n-1) π / 2 + δ]. 4. The optical fiber gyro according to claim 1, wherein the first delta serrodyne waveform signal is one cycle.
The sum of the time T _A and the second time T _B constant T = T _A + T _B
, And the like peak value of the delta serrodyne waveform signal does not exceed a predetermined allowable value, and is configured such that the magnitude of the first time T _A and the second time T _B is regulated An optical fiber gyro characterized by the above. 5. The optical fiber gyro according to claim 4, wherein when a positive time in one cycle T of the delta serrodyne waveform signal is T ₊ and a negative time is T ₋ , a difference ΔT _{+ in an} integrated value thereof. -ShigumaT _- or integrated value of the difference Σ (T ₊ -T _-)
An optical fiber gyro, wherein the magnitudes of the first time T _A and the second time T _B are adjusted based on the following formula. 6. The optical fiber gyro according to claim 1, wherein the sagnac phase difference Δθ is determined by the lamp phase difference σ.
At the stable point of the control loop where is canceled, the positive time in one cycle T of the delta serrodyne waveform signal is represented by T ₊ ,
The negative time T _- when a difference in the integrated value oT ₊ .-. SIGMA
T _- or integrated value Σ of the difference (T ₊ -T _-) optical fiber gyro characterized by calculating the input angular rate Ω and turning angle based on. 7. The optical fiber gyro according to claim 6, wherein the positive time T ₊ and the negative time T _- are counted with pulses of a predetermined cycle, and the number of pulses is set to N ₊ and N ₋ , respectively. An optical fiber gyro that calculates an input angular velocity Ω and a turning angle based on the difference 積 算 N ₊ −ΣN ₋ or the difference Σ (N ₊ −N ₋ ) of the integrated value. 8. The optical fiber gyro according to claim 1, wherein the control voltage signal supplied to the phase controller is a constant reference voltage corresponding to the reference phase difference. becomes than the sum of the lamp voltage signal V _R corresponding to the signal V ^* and the lamp retardation, the lamp voltage signal V _R is the value I _a and the intensity I of the interference light in the first time T _a An optical fiber gyro, which is generated by integrating a voltage signal corresponding to a difference signal ΔI from the value I _B of the intensity I of the interference light at the second time T _B. 9. The optical fiber gyro according to claim 1, wherein an intensity signal I of the interference light output from the photodetector is input to the optical fiber gyro. difference signal light intensity ΔI = I _a -I signal processing unit for generating a voltage signal V ₀ corresponding to _B an integrator for integrating by inputting the voltage signal V ₀ and the output signal V of the integrator
A delta serrodyne section for inputting _R to generate the delta serrodyne waveform signal. 10. The optical fiber gyro according to claim 9, wherein the signal processing unit removes a DC component from the intensity signal I of the interference light and alternately sets ± ΔI / 2 for each of the times T _A and T _B. Including a DC remover for generating a changing alternating signal, an AC amplifier for AC amplifying an output signal of the DC remover, and a synchronous detector for obtaining a DC voltage signal V ₀ from an output signal of the AC amplifier. An optical fiber gyro characterized by the following. 11. The optical fiber gyro according to claim 9, wherein the delta serrodyne section outputs a reference voltage signal V ^* whose sign changes alternately at times T _A and T _B and an output from the integrator. An optical fiber gyro, comprising: an adder for adding the ramp voltage signal V _R thus obtained _; and a delta serrodyne integrator for integrating an output signal of the adder. 12. The method according to any one of claims 8 to 11, wherein
In the optical fiber gyro, the reference voltage signal V^*The reference phase control unit that generates
And the reference phase controller controls the first time T_AIn
The intensity signal I of the interference light_AAnd the second time T _BSmell
The intensity signal I of the interference light_BAverage I of₀The equivalent of
Optical fiber characterized by being generated using a pressure signal
gyro.