JPH0472512A - Signal processing device for optical gyroscope - Google Patents

Abstract

PURPOSE:To obtain a photo-electric transduced output signal in proportion to the rotational angular velocity by conducting the beam of light in a photo- transmitting path working together with a rotary shaft in both directions clockwise and counterclockwise simultaneously, subjecting it at the same time to phase modulation, and thereby sensing the phase difference of light due to Sagnac effect. CONSTITUTION:A frequency mixing circuit to output No.1, N0.2, and No.3 analog signals (15-17) is provided along with an A/D converter 18 which converts these analog signals into No.1 digital signal 19. Further are provided a digital demodulating means and also a rotational angular velocity calculating means which outputs No.11 digital signal 33. The frequency mixing circuit converts frequency components of a photo-electric transduced output signal into a signal having a frequency DELTAfm, and the A/D converter makes conversion into digital signal. Further, the standardized demodulation signal is turned into a signal proportional to the input rotational angular velocity. Thereby the gyroscope output signal can be made an output proportional to the input rotational angular velocity.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a signal processing device for an optical gyro, and more particularly, the present invention relates to a signal processing device for an optical gyro, and more specifically, a signal processing device for a signal processing device for an optical gyro. The light of the Sag
The present invention relates to a signal processing device for an optical gyro that detects the phase difference of light based on the nac) effect and obtains a signal proportional to the rotational angular velocity.

[Conventional technology]

FIG. 7 schematically shows a part of the configuration of a conventional optical fiber gyro to which phase modulation is added.

In the figure, 1 is a light source, 2a and 2b are optical splitting couplers, 3 is a polarizer, 4 is a phase modulator, and 5 is a polarization-maintaining single mode optical fiber wound perpendicular to the rotation axis. A light propagation path, 6 a photoelectric conversion circuit, 201 a band pass filter, 2
03 is an analog multiplier, 204 is an oscillator, 205 is a square wave conversion circuit, 208 is a low-pass filter, 7 is a photoelectric conversion output signal, 8 is a phase modulator drive signal, 202, 206 and 207 are output signals of each circuit, and 209 indicates a gyro output signal.

Further, P indicates a signal processing circuit.

In the configuration shown in FIG. 7, the first light beam emitted from the light source 1 enters the first optical splitting/coupling device 2a and is divided into two to become second and third light beams. The second light beam travels in the direction of the solid arrow and enters the polarizer 3. The second light beam incident on the polarizer 3 transmits only a certain polarized wave, and the second light beam enters the polarizer 3.
The light enters the optical splitter coupler 2b. The second light beam incident on the second optical splitting/coupling device is divided into two to become fourth and fifth light beams. The fourth light beam travels in the direction of the dashed arrow;
The signal enters the phase modulator 4 and undergoes phase modulation of Φ,·5 in (ωat). Here, Φ is the maximum phase shift, ω.

indicates the phase modulator driving angular frequency. The fourth optical beam subjected to phase modulation propagates counterclockwise through the optical propagation path 5, and then re-enters the second optical splitter/coupler 2b. The fifth light beam propagates from the second optical splitter coupler 2b in the direction of the dashed line arrow, and after propagating clockwise through the optical propagation path 5,
After entering the phase modulator 4 and undergoing phase modulation of Φ,·5 in (ω, 1), the light enters the second optical splitting coupler 2b again. The fourth and fifth light beams incident on the second optical splitter and coupler are recombined to form a sixth light beam. The sixth light beam is incident on the polarizer 3, and only a certain polarization component is transmitted therethrough, and is incident on the first optical splitter/coupler 2a. The sixth light beam incident on the first optical splitter/coupler 2a is split into two into seventh and eighth light beams, of which the eighth light beam is incident on the photoelectric conversion circuit 6.

A photoelectric conversion output signal 7, which is an output signal of the photoelectric conversion circuit 6, is input to a bandpass filter 201, and ω11 of the same angular frequency as the phase modulator drive signal 8 is transmitted. Further, the phase modulator drive signal 8 outputted from the oscillator 204 is input to the square wave conversion circuit 205, and is converted into a square wave whose frequency and phase are synchronized.

The output signal 202 of the bandpass filter 201 and the output signal 206 of the square wave conversion circuit 205 are both input to an analog multiplier 203. The output signal 207 of the analog multiplier 203 is input to a low-pass filter 208 and only the DC component is transmitted therethrough, resulting in a gyro output signal 209. The gyro output signal 209 is expressed by the following equation.

Vo oc (2/z)Po sinφs ・J+(
η) sinψ.

+U, +U, ・・・・・・・・・・・・・・・・・・
...(1) Here, ■. is the gyro output signal, Po is the non-interfering amount of clockwise or counterclockwise light incident on the photoelectric conversion circuit, φ is the phase difference of light due to the Sagnac effect (=4πRLΩ/λC), and R is the optical propagation road radius,
L is the optical fiber length, Ω is the input rotational angular velocity, λ is the wavelength of light in vacuum, C is the speed of light in vacuum, J is the first-order Bessel function, η is the phase modulation degree, ψ. is the phase difference between the bandpass filter output signal and the square wave conversion circuit output signal, Ul is the offset voltage of the analog multiplier, and U2
indicates the offset voltage of the low-pass filter.

[The problem that the invention tries to solve! ! ] In the conventional optical fiber gyro signal processing circuit P described above, the gyro output signal 209 is proportional to sinφ even when the offset voltages U and Uz are zero. Therefore, there was a problem in that the linearity with respect to the input rotational angular velocity Ω was poor, and the detectable input rotational angular velocity was limited to a range corresponding to ±π/2 [radl with a phase difference φS due to the Sagnac effect.

Furthermore, the gyro output signal 209 includes fluctuations in the amount of non-interfering light P0 incident on the photoelectric conversion circuit, fluctuations in the degree of phase modulation η caused by the phase modulator 4, and phase difference ψ. There is also a problem in that linearity and scale factor stability tend to deteriorate due to fluctuations in .

Furthermore, even when the input rotational angular velocity is zero, that is, the phase difference φ due to the Sagnac effect is zero, the offset voltage U
There is also the problem that bias stability tends to deteriorate due to fluctuations in r and Ut.

The present invention was created in view of the above-mentioned problems in the prior art, and it is possible to make the gyro output signal an output that is accurately proportional to the input rotational angular velocity, minimize the gyro bias fluctuation, and improve linearity and scale factor stability. It is an object of the present invention to provide a signal processing device for an optical gyro that can increase the gyro's maximum detection angular velocity range and eliminate limitations on the maximum detection angular velocity range of the gyro.

[Means to solve the problem]

As shown in the principle block diagram of FIG. 1, according to the present invention, light is simultaneously propagated in a clockwise and counterclockwise direction through a light propagation path cooperating with a rotating shaft, and phase modulated. A device for signal processing of an optical gyro that detects the phase difference of light due to the Sagnac effect from the intensity of interference light of propagated light to obtain a photoelectric conversion output signal 7 proportional to the rotational angular velocity, the device comprising: a phase modulator; In response to analog and digital reference signals 10-13 synchronized in frequency and phase with the drive signal 8, the frequency f of the phase modulator drive signal is determined from the photoelectric conversion output signal.
Extract signal components with the same frequency as m, twice the frequency 2fm, and four times the frequency 4fm, and calculate the respective frequencies Δfm
and output the first, second and third analog signals 15 to 17, respectively, and convert the analog reference signal into a signal with a frequency Δfm and output the fourth analog signal 14. Mixing circuits 98 to 9d, and an analog/digital circuit that converts the first to third analog signals into a first digital signal 19 in response to a second digital signal 37 whose phase is synchronized with the fourth analog signal. (
A/D) converter 18, which outputs the second digital signal and generates a third digital signal 22 whose phase is synchronized with the fourth analog signal, and whose phase is synchronized with the third digital signal. and a fourth phase shifted by 90° from each other.
and a fifth digital signal 24.25, which are digitally multiplied with the first digital signal to remove DC components, and output sixth and seventh digital signals 26.27. digital demodulating means 20a to 20d, 21.23, and the sixth and seventh
Based on the digital signal, the quadrant in which the optical phase difference due to the Sagnac effect exists is determined from the sign of the signal component corresponding to the frequencies of fm and 2fm or 4fm of the photoelectric conversion output signal, and the eighth and ninth digital signals are determined. 29a,
quadrant discriminating means 28 for outputting a signal 29b; a rotational angular velocity calculation means 30 that outputs an eleventh digital signal 33 proportional to the rotational angular velocity based on the sixth to tenth digital signals; A signal processing device for an optical gyro is provided.

[Effect]

According to the above configuration, the frequency mixing circuit converts the fm, 2fm, and 4fm frequency components of the photoelectric conversion output signal into a signal with a frequency Δfm, the A/D converter converts the frequency components into a first digital signal, and the phase modulator Digital demosulation is performed between the first digital signal and the fourth and fifth digital signals whose phases are synchronized with the drive signal and whose phases are shifted by 90 degrees from each other, and the photoelectric exchange output signals fm and 2fm ( The quadrant determining means determines the quadrant of the optical phase difference due to the Sagnac effect from the sign of the frequency component of 2 fm and 4 fm), and the phase modulation calculation means determines the current phase from the amplitude ratio of the 2 fm and 4 fm frequency components of the photoelectric modulation output signal. A coefficient corresponding to the modulation degree is calculated, and this coefficient, the above quadrant, and f of the photoelectric modulation output signal are calculated.
Based on the amplitude ratio of the frequency components m and 2fm, the rotational angular velocity calculation means outputs a signal proportional to the input rotational angular velocity.

This makes the gyro output signal proportional to the input rotational angular velocity, eliminates limitations on the maximum detection angular velocity range, and eliminates light intensity fluctuations, phase modulation degree fluctuations, and phase fluctuations between the photoelectric conversion output signal and the phase modulator drive signal. remove the influence,
It becomes possible to eliminate the occurrence of offset voltage.

Note that other structural features and details of the operation of the present invention will be explained using the embodiments described below with reference to the accompanying drawings.

[Example] Hereinafter, an example of the present invention will be described with reference to FIG.

The signal processing device of this embodiment is applied in place of the signal processing circuit P of the optical fiber gyro shown in FIG. 7, for example, and includes first to fourth terodyne mixers 9a to 9d,
A/D converter 18 and timing pulse generation means 2
1, and cosine/sine signal (cos/5in) generating means 23
and first and second digital multiplication means 20a, 20b.
and first and second digital filters 20c, 20
d, quadrant discrimination means 28, rotational angular velocity calculation means 30, phase modulation degree calculation means 31, and reference signal generation circuit 35 are connected as shown in the figure.

The functions (operations) of each component will be explained below.

First, the reference signal generation circuit 35 generates a phase modulator drive signal (
A fifth analog signal 10 having a frequency fm synchronized in frequency and phase with the analog signal 8, a twelfth digital signal 11, a thirteenth digital signal 12, and a fourteenth digital signal 8 are output. output the digital signal 13 of the fourth heterodyne mixer 9d and the first
and is supplied to the fourth heterodyne mixer 99a, 9d, the second heterodyne mixer 9b, and the third heterodyne mixer 9C. Further, the phase-modulated charging conversion output signal 7 is transmitted to the first to third heterodyne mixers 9a.
~Input at 9C.

In response to the twelfth digital signal 11, the first heterodyne mixer 9a extracts the same frequency component as the frequency fm of the phase modulator drive signal 8 from the photoelectric conversion output signal 7, converts it into a signal with a frequency Δfm, and converts it into a signal with a frequency Δfm. 1 analog signal 1
Outputs 5. This first analog signal 15 is expressed by the following equation.

<First analog signal> L (X:2P6 sinφs・J+(η)Xsin(
Δω, 1+ψI)・・・・・・・・・(2) Here, Δ
ω is the change in the phase modulator driving angular frequency (=2πΔfm
), ψ are the fm component of the photoelectric conversion output signal 7 and (fm+Δ
The phase difference with the twelfth digital signal 11 having a frequency of fm) is shown.

In the second heterodyne mixer 9b, in response to the thirteenth digital signal 12, the frequency 2 is converted from the photoelectric conversion output signal 7.
The fm component is extracted and converted to a signal with frequency Δfm, and the second
The analog signal 16 is output. This second analog signal 16 is a second analog signal expressed by the following formula>V! CC2pHcosφ−・Jz(η)Xsin(Δ
ω, t+φ2)・・・・・・・・・(3) Here, ψ2
is the 2fm component of the photoelectric conversion output signal 7 and (2fm+Δfm
) shows the phase difference with the thirteenth digital signal 12 having a frequency of .

In response to the fourteenth digital signal 13, the third heterodyne mixer 9c converts the photoelectric conversion output signal 7 into a frequency 4.
The fm component is extracted and converted to a signal with frequency Δfm, and the third
The analog signal 17 is output. This third analog signal 17 is expressed by the following equation.

<Third analog signal> V3 CC2P, cosφ, -J, (η)Xsin(
Δω, L÷ψ3)・・・・・・・・・(4) Here, ψ
, is the 4fm component of the photoelectric conversion output signal 7 and (4fm+Δf
m) shows the phase difference with the fourteenth digital signal 13 having the frequency.

The first to third analog signals 15 to 17 are input to an A/D converter 18 and converted into a first digital signal 19. This first digital signal 19 is, for example, a digital signal expressed as a binary number or the like.

The fourth heterodyne mixer 9d converts the fifth analog signal 10 into a signal with a frequency Δr in response to the twelfth digital signal 11, and outputs the fourth analog signal 14. This fourth analog signal 14 is expressed by the following equation.

4th analog signal> ■4ocsin (Δω, t+ψREF) −−−−(5
) Here, φ1F indicates the phase difference between the fifth analog signal 1o and the twelfth digital signal 11.

This fourth analog signal 14 is input to the timing pulse generating means 21, and a second
and converted into a third digital signal 37.22. Of these, the second digital signal 37 is the A/D converter 1
8 is input. The A/D converter 18 converts the first to third analog signals 15 in synchronization with the digital signal 37.
~17 into a first digital signal 19. Further, the third digital signal 22 is input to a cos/sin generating means 23.

The cos/sin generating means 23 generates the third digital signal 2
2, one cycle of the signal 22 is divided at predetermined time intervals, and the signals correspond to the time positions and are 9 times apart from each other.
Cosine and sine 0° out of phase
ine) as fourth and fifth digital signals 24.25, respectively. The fourth and fifth digital signals 24.25 are expressed by the following equations.

Fourth digital signal (24) > VR1! F, cosccCO5(Δω, 1±ψII
F)・・・・・・(6)〈Fifth digital signal (25)
> ■+111! F+ sia cCSln(Δω, t+ψ
tty) --(7) The fourth digital signal 24 is
a first digital multiplication means 20 together with a digital signal 19 of
a, and after being digitally multiplied, the direct current (DC) component is removed through the first digital filter 20c and output as the sixth digital signal 26. The first to third analog signals 15 of this sixth digital signal 26
Each signal corresponding to 17 is expressed by the following equation.

<Sixth digital signal corresponding to first analog signal (15)> ■ I+ Cot ” P OSin φ
, ・J, (η)Xsin(ψ1゛)・・・・・・
・・・・・・・・・(8)〈Second analog signal (16
)〉 ■2+ cos ” Po cosφS'J2 (77)
Xsin (ψ2”)・・・−・・・・・・・・・・・・(
9) <Sixth digital signal corresponding to third analog signal (17)> V 31 cos ” Po CO3-, Ja(η)X
sin(ψ3′)・・・・・・・・・・・・・・・(1
0) Here, ψ1′=ψI−ψtributary EF, ψ2”=ψ2−ψ□1, ψ,′−ψ3−ψIEF,

On the other hand, the fifth digital signal 25 is input to the second digital multiplication means 20b together with the first digital signal 19,
After being digitally multiplied, the second digital filter 2
The DC component is removed through 0d and output as the seventh digital signal 27. Each signal corresponding to the first to third analog signals 15 to 17 of this seventh digital signal 27 is expressed by the following equation.

<Seventh digital signal corresponding to first analog signal (15)> ■1. sin ” P@Sinφ, ・j, (η)X
cos (ψ1゛)・・・・・・・・・・・・・・・(
11) Seventh digital signal corresponding to second analog signal (16)> ■z* si, 1” Po CO3φs ・JZ(77
)X cos (ψ2”)・・・・・・・・・・・・・
...(12) <Seventh digital signal corresponding to third analog signal (17)> v:1. sin cc po cosφs・Ja<y
y)X cos (ψ3゛)・・・・・・・・・・・・
...(13) In this way, multiplication and filtering (i.e., digital demodulation) are performed digitally, so conventional signal processing forms (i.e., analog
It is possible to eliminate the disadvantage that an offset voltage caused by an analog IC or the like is superimposed on a signal after demosulation, as seen in demosulation.

The sixth and seventh digital signals 26,27 are input to the quadrant determining means 28. The quadrant determining means 28 uses the formula (8
), (9), (11), and (12), V I + Co S and Vz of the sixth digital signal 26,
cos or VI+5111 of the seventh digital signal 27
1 and the signs of V z and s t n, the following logical judgment is made.

Here, VI+Col of the sixth digital signal 26 and the seventh
Vl and S□0 of the digital signal 27 correspond to the normalized demosulated output 101 (shown as a solid line) shown in FIG. V! +si* corresponds to the normalized demosulated output 102 (indicated by a broken line) shown in FIG.

As can be seen from FIG. 2, the signs of the normalized demosulated outputs 101 and 102 change as shown in Table 1 (see next page) with respect to the phase difference φ, [rad] due to the Sagnac effect.

Based on the logical judgment shown in Table 1, first, the existence quadrant of the phase difference φ due to the Sagnac effect is within the range of ±π [rad] (
Determined in quadrant range A). In this case, there are four types of quadrant symbols M in the quadrant range A of the phase difference φ, depending on the combination of the codes of the normalized demosulation outputs 101 and 102 (0
~3).

Table 1 [Margin below] As shown in Table 1, there are no identical quadrant symbols M for adjacent phase differences φ. Therefore, quadrant symbol M of quadrant range A
For example, when ■ changes from "3" to "0", the quadrant of the phase difference φ is 2π[ra
It is judged that it exists in the quadrant range where dl has been added. ■Conversely, if it changes from "0" to "3", the phase difference φ,
The quadrant of is 2π from the quadrant range before the quadrant symbol M changes.
[rad] It is judged that it exists in the destroyed quadrant range.

FIG. 3 shows an example of the flow of quadrant discrimination processing. In the illustrated example, the quadrant range A(-
Quadrant discrimination is performed for π to +π).

First, in step 301, the sixth and seventh digital signals 26, 27 (i.e., the normalized demosulated output 10
1.102) is taken into the quadrant determining means 28.

In steps 302 to 309, the logic of the quadrant symbol M is determined based on the combination of the codes of the normalized demosulated outputs 101 and 102.

In step 310, it is determined whether the quadrant symbol M of quadrant range A is equal to 0 (YES) or not (NO). If the determination result is YES, the process proceeds to step 311; if the determination result is NO, Proceed to step 313. Step 311
Then, the quadrant symbol M0 of the quadrant range A one operation cycle before
is equal to 3 (however, M in the initial state = 2) (YES)
If the result of the determination is YES, the process proceeds to step 312; if the result of the determination is no, the process proceeds to step 313.

If the determination result in step 310 is YES and step 31
If the determination result of 1 is YES, this corresponds to the case ① described above, that is, the case where the quadrant symbol M changes from "3" to "0". Therefore, in step 312, quadrant range B
As the quadrant symbol N, the quadrant symbol N of the quadrant range B before the quadrant symbol M changes (however, N in the initial state, = 0) is r
A value obtained by adding "l" is set. As a result, the phase difference φS is 2π[r
It is determined that it exists in the quadrant range where adl has been added.

After the process of step 312 is completed, the process proceeds to step 316, and the quadrant symbols M and N are set as M, , N, respectively. Furthermore, after outputting the quadrant discrimination results (quadrant symbols M, N) in step 317, this flow ends.
becomes.

On the other hand, in step 313, the quadrant symbol M of the quadrant range A is 3.
It is determined whether it is equal to (YES) or not (No), and if the determination result is YES, the process proceeds to step 314, and if the determination result is NO, the process proceeds to step 316. Step 3
14, the quadrant symbol M0 of the quadrant range A one operation cycle before is equal to 0 (however, M in the initial state, = 2) (YE
If the result of the determination is YES, the process proceeds to step 315; if the result of the determination is NO, the process proceeds to step 316.

If the determination result in step 313 is YES and step 31
If the determination result in step 4 is YES, this corresponds to the case 2 described above, that is, the case where the quadrant symbol M changes from "0" to "3". Therefore, in step 315, quadrant range B
as the quadrant symbol N of the quadrant range B before the quadrant symbol M changes. (However, the value obtained by subtracting "l" from the initial state N0=O) is set. As a result, the phase difference φS is increased by 2π from the quadrant range before the quadrant symbol M changes.
[It is determined that it exists in the quadrant range reduced by radl.

After the process of step 315 is completed, the process proceeds to step 316 and the above-described process is repeated.

The quadrant discrimination results based on the above logical discrimination process are shown in Table 2 (
(see next page).

Through the above logical determination, the quadrant determining means 28 outputs the eighth digital signal 29a corresponding to the quadrant symbol M and the ninth digital signal 29b corresponding to the quadrant symbol N.

[Margin below]

Table 2 Next, the phase modulation degree calculation means 31 uses equations (9) and (10)
and V2+CO1 of the sixth digital signal 26 shown in (12) and (13), and ■3. . Based on o5 and V2+Sin and Vl-Sin of the seventh digital signal 27, the following calculation is performed.

g [(V2. cos2+ Vz, 5inz)”
, 2/(Vl, cos” + V:1.s;
n”) ””]=gNJ2(η)/J, (η)11 =lJ2(η)/Jl(η)1・・・・・・・・・・・・
・・・・・・・・・(14) Here, gl ] is IJ2
It represents a function that converts (η)/J4(η)j to 1J2(η)/Jl(η)1.

The phase modulation degree calculation means 31 outputs a tenth digital signal 32 corresponding to the value shown in equation (14).

Next, the rotational angular velocity calculating means 30 calculates Vl, C6, and Vlcos of the sixth digital signal 26 represented by (8), (9), (11), and (12) and the seventh digital signal 27. Vl+1lll and V2. The following calculation is performed based on *rfi and the tenth digital signal 32 expressed by equation (14).

Q=lJz(η)/Jl(η) x [(Vl, c6g”+V1.s=,%2)I/
! /(Vz,C,,” +Vz,,i,”)””]=
l tan(φ,)1・・・・・・・・・・・・・・・
(15) The rotational angular velocity calculation means 30 calculates the eighth and ninth digital signals 29a and 2 corresponding to the quadrant in which the logically determined phase difference φ shown in Table 2 exists.
9b and the calculated value expressed by equation (15), calculates the phase difference φ5 due to the Sagnac effect, and outputs the eleventh digital signal 33 corresponding to this calculated value (that is, proportional to the input rotational angular velocity). .

FIG. 4 shows an example of the flow of rotational angular velocity calculation processing.

First, in step 401, the sixth, seventh and tenth digital signals 26, 27, 32 are input to the rotational angular velocity calculation means 29.
In the next step 402, Q is calculated. Furthermore, in step 403, the eighth and ninth digital signals 29a and 29b are transmitted to the rotational angular velocity calculation means 29.
be taken in.

In step 404, the aforementioned quadrant symbol M is equal to 0 (
YES) or NO (NO), and the determination result is YES.
In the case of S, the process proceeds to step 405, and if the determination result is NO, the process proceeds to step 408.In step 405,
It is determined whether the value of Q is smaller than rl (YES) or not (No), and if the determination result is YES, step 40
The process proceeds to step 6, and if the determination result is NO, the process proceeds to step 407. In step 406, φ,. As the value of 1π+j
an-' (Q) is calculated, and in step 407, -x/2- cot-' (1/Q
) is calculated.

When the processing in steps 406 and 407 is completed, the process proceeds to step 419, where 2πN is added to the calculated value φ3° to calculate the phase difference φ due to the Sagnac effect.

After this, the flow becomes "end".

Note that the remaining steps 408 to 411, 412 to 415
The processes of steps 416 to 418 can be easily inferred from the processes of steps 404 to 407 described above, so their explanation will be omitted.

The eleventh digital signal 33 (ie, gyro output) output based on the above calculation process corresponds to the waveform 103 (displayed by a solid line) shown in FIG. Also, the value φ in the flowchart of FIG. is the waveform 10 shown in FIG.
4 (displayed with a broken line).

FIG. 6 shows another example of the flow of rotational angular velocity calculation processing. For the illustrated steps 601 to 611, the fourth
Since it can be easily inferred from the flowchart in the figure, its explanation will be omitted.

As explained above, in this embodiment, in the rotational angular velocity calculation means 30, the outputs of the first digital multiplication means 20a and the digital filter 20c shown in equations (8) and (9), and the outputs of equations (11) and (12) The calculation shown in equation (15) is performed from the outputs of the second digital multiplication means 20b and the second digital filter 20d shown in equation (14), and the output of the phase modulation degree calculation means 31 shown in equation (14). Eighth and ninth digital signals 29a corresponding to the quadrants of the phase difference φ based on the logical determination shown in FIG. 3 and Table 2;
From 29b, calculations are performed according to the flow shown in FIG. 4 or 6, and a digital signal corresponding to the calculated value is output as a gyro output signal 33.

Therefore, a gyro output signal proportional to the input rotational angular velocity can be obtained, and there is no restriction on the maximum detected angular velocity.

In addition, it is possible to eliminate the effects of light amount fluctuations, phase modulation degree fluctuations, and phase difference fluctuations between the charge conversion output signal 7 and the phase modulator drive signal 8, thereby increasing gyro linearity and scale factor stability. .

In addition, fm, 2 fm and 4 of photoelectric conversion output signal 7
fm component to the first to third heterodyne mixers 9a to 9.
c and the A/D converter 18 convert the AC signal into a digital signal, and the first and second digital multiplication means 20a
, 20b and the first and second digital filters 20
Since demosulation is done digitally by C and 20d, the offset voltage that occurs when demosulating analogously as in the conventional type does not occur, and therefore the gyro bias fluctuations caused by offset voltage fluctuations are eliminated. It can be made extremely small.

〔Effect of the invention〕

As described above, according to the present invention, the gyro output signal can be made to be an output that is accurately proportional to the input rotational angular velocity, the bias fluctuation of the gyro can be minimized, and the linearity and scale factor stability can be improved.

Furthermore, it is possible to eliminate limitations on the maximum detection angular velocity range of the gyro.

[Brief explanation of drawings]

FIG. 1 is a principle block diagram of the optical gyro signal processing device according to the present invention, FIG. 2 is a waveform diagram showing the normalized demosulated output in the device of FIG. 1, and FIG. 3 shows the quadrant discrimination means in FIG. 4 is a flowchart showing an example of the processing performed by the rotational angular velocity calculating means in FIG. 1; FIG. 5 is a waveform diagram showing the gyro output by the device shown in FIG. 1; FIG. 6 is a rotation A flowchart showing another example of the processing performed by the angular velocity calculation means. FIG. 7 is a block diagram partially schematically showing the configuration of a conventional optical fiber gyro with phase modulation added. (Explanation of symbols) 7... Photoelectric conversion output signal, 8... Phase modulator drive signal (sixth analog signal),
9a to 9d...first to fourth heterodyne mixers, 1
0...5th analog signal, If-13...12th to 14th digital signal, 14.
...Fourth analog signal, 15 to 17... First to third analog signal, 18...
・Analog/digital (A/D) converter, 19, 3
7.22.24-27.29a, 29b, 34.3
2.33-...first to eleventh digital signals,
20a, 20b...first and second digital multiplication means, 20c, 20d...digital filter, 21...
- Timing pulse generation means, 23... Cosine/sine signal (cos/5in) generation means, 28... Quadrant discrimination means, 30... Rotation angular velocity calculation means, 31... Phase modulation degree calculation means, 35 ...Reference signal generation circuit.

Claims (7)

[Claims] 1. Light is simultaneously propagated in the clockwise and counterclockwise directions through a light propagation path that co-moves with the rotating shaft, and the phase is modulated, and the phase difference of the light due to the Sagnac effect is detected from the intensity of the interference light of the light propagated in both directions. A device for signal processing of an optical gyro to obtain a photoelectric conversion output signal (7) proportional to the rotational angular velocity using an analog and digital reference whose frequency and phase are synchronized with the phase modulator drive signal (8). In response to the signals (10 to 13), signal components having the same frequency as the frequency f_m of the phase modulator drive signal, twice the frequency 2f_m, and four times the frequency 4f_m are extracted from the photoelectric conversion output signal, and the signal components are each extracted at a frequency Δf_m. Convert to the first and second signals respectively.
and a frequency mixing circuit (9a to 9d) that outputs a third analog signal (15 to 17) and converts the analog reference signal into a signal with a frequency Δf_m to output a fourth analog signal (14). , an A/D converter ( 18), and a third digital signal (22) which outputs the second digital signal and whose phase is synchronized with the fourth analog signal.
), and form fourth and fifth digital signals (24, 25) whose phases are synchronized with the third digital signal and whose phases are shifted by 90 degrees from each other, and between them and the first digital signal. digital demodulating means (20a to 20
d. quadrant discrimination means (28) for discriminating quadrants and outputting eighth and ninth digital signals (29a, 29b); The 10th phase corresponding to the current phase modulation degree is determined from the amplitude ratio of the signal component corresponding to the frequency.
a rotational angular velocity that outputs an eleventh digital signal (33) proportional to the rotational angular velocity based on the sixth to tenth digital signals; A signal processing device for an optical gyro, comprising: a calculation means (30); 2. The quadrant determining means determines a quadrant range in which a quadrant symbol determined according to a combination of signs of a signal component of frequency f_m and frequency 2f_m or 4f_m included in the sixth and seventh digital signals (26, 27) is in a predetermined range. 2π [rad] or -2π
The eighth and ninth digital signals (29
a, 29b).
A signal processing device for an optical gyro according to. 3. The digital demodulating means includes a timing pulse generating means (21) for generating the second digital signal and outputting it to the A/D converter and also generating the third digital signal; cosine/sine signal generating means (23) that outputs the fourth and fifth digital signals based on the digital signal; and multiplication between the fourth and fifth digital signals and the first digital signal, respectively. The first and second digital multiplication means (20a
, 20b), and first and second digital filters that digitally cut DC components from the multiplication results and output the sixth and seventh digital signals, respectively. Signal processing device for optical gyro. 4. The frequency mixing circuit adjusts frequencies f_m, 2f_m and 4f_m, respectively, in response to the photoelectric conversion output signal.
first, second, and third heterodyne mixers (9a to 9c) that convert the signal component of the signal into a signal with a frequency Δf_m and output the first to third analog signals, and the analog reference signal (10). Convert it to a signal with frequency Δf_m and
A fourth heterodyne mixer (
9d). The signal processing device for an optical gyro according to claim 1, comprising: 5. A fifth analog signal (10) whose frequency and phase are synchronized with the sixth analog signal;
digital signal (11), 13th digital signal (12)
), and a reference signal generation circuit that outputs and supplies a fourteenth digital signal (13) to the fourth heterodyne mixer, the first and fourth heterodyne mixers, the second heterodyne mixer, and the third heterodyne mixer, respectively. The signal processing device for an optical gyro according to claim 4, further comprising (35). 6. 2. The signal processing device for an optical gyro according to claim 1, wherein said digital demodulating means, quadrant determining means, phase modulation degree calculating means, and rotational angular velocity calculating means perform their respective processing based on software. 7. The optical propagation path is constituted by an optical fiber.
The signal processing device for an optical gyro according to claim 1.