JP2010019717A - Closed-loop type optical interference angular velocity meter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a closed-loop type optical interference angular velocity meter for reducing an output error caused by noise included in the output of a light receiving unit. <P>SOLUTION: An electric signal from the light receiving unit 6 is demodulated by a demodulation section 10. The demodulation signal is A/D-converted and is inputted to a digital signal processor 30. The demodulation section 10 includes: a first sample-and-hold section 11 for sampling and holding an electric signal from the light receiving unit 6; a first low-pass filter 13 for setting the output of the first sample-and-hold section 11 to be input; a second sample-and-hold section 12 for sampling and holding the electric signal; and a second low-pass filter 14 for setting the output of the second sample-and-hold section 12 to be input. The digital signal processor 30 has a subtractor 31 and performs operation for subtracting the output of the second low-pass filter 14 from that of the first low-pass filter 13. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a closed loop optical interference angular velocity meter.

FIG. 7 shows a configuration example of a standard closed-loop optical interference angular velocity meter, and its operation is outlined.
Light of a certain intensity is emitted from the light source 2 controlled by the light source driving circuit 1. This light is transmitted through an optical fiber and enters the optical element 4 via the optical coupler 3. As the optical element 4, for example, an optical integrated circuit in which a waveguide is formed in an optical crystal of lithium niobate (LiNbO ₃ ) and an optical branching coupler 9, a phase modulator 7, and a phase modulator 8 are integrated is used. The incident light is branched into two routes by the optical branching coupler 9, one of which enters one end of the optical fiber coil 5 as CW (clockwise) light, circulates around the optical fiber coil 5, and reaches the other end. The light enters the other end of the optical fiber coil 5 as CCW (counter-clockwise) light, goes around the optical fiber coil 5 and reaches one end. In this specification, “clockwise” and “counterclockwise” are described as clockwise and counterclockwise when the drawing is viewed from the front.

At this time, phase modulation is performed on the CW light and the CCW light. In other words, when τ is the time during which the CW light or CCW light passes through the optical fiber coil 5 in the absence of an angular velocity input, the phase modulator 7 provided on one of the two routes on the optical element 4 A rectangular wave (see FIG. 8) having a pulse width generated by the phase modulation driving circuit 60 with the timing signal generated by the signal generation circuit 50 as input and a duty ratio of 1/2 is applied to the CW light and the CCW light. Phase modulation of + π / 4 and −π / 4 is alternately performed.
In the configuration shown in FIG. 7, the CW light is phase-modulated by the phase modulator 7 before circulating around the optical fiber coil 5, and the CCW light is phase-shifted by the phase modulator 7 after circulating around the optical fiber coil 5. Undergo modulation. Therefore, since the time of phase modulation between the CW light and the CCW light branched at the same time is shifted by τ, the phase difference of + π / 2 and −π / 2 is relatively different between the CW light and the CCW light. Will be given.

By the way, the CW light and the CCW light circulate around the optical fiber coil 5 and are optically coupled and interfered by the optical branching coupler 9 of the optical element 4. If there is a phase difference of Δφ between the CW light and the CCW light in the absence of an angular velocity input, the intensity of the light that interferes with the CW light and the CCW light (interference light intensity I ₀ ) is expressed as P ₀ is given by equation (1) (see the curve drawn with a solid line shown in FIG. 9A).

When a phase difference of + π / 2 and −π / 2 is given relative to the CW light and the CCW light by the phase modulator 7, Δφ = −− even in the case of Δφ = + π / 2 according to the equation (1). Even in the case of π / 2, the interference light intensity I ₀ is P _0/2 (see FIG. 9B). In addition, since the interference light intensity I ₀ passes through a point where the maximum intensity P ₀ is reached at the time of the rising or falling of the rectangular wave shown in FIG. 8, spike noise shown in FIGS. 9B and 10B is generated. Arise.

  Now, assume that an angular velocity Ω [rad / s] is added clockwise to a closed loop optical interference angular velocity meter. More precisely, the input angular velocity Ω is added to the optical fiber coil 5 clockwise. As a result, the optical path length differs between the CW light and the CCW light, and the position based on the input angular velocity Ω between the CW light and the CCW light. A phase difference occurs (Sagnac effect).

Let Δφ _{s be the} phase difference between the CW light and the CCW light (Sagnac phase difference) due to the Sagnac effect. When the clockwise input angular velocity Ω is added, the phase of the CW light advances by Δφ _{s with} respect to the phase of the CCW light. The interference light intensity I ₀ when the Sagnac phase difference Δφ _s is added is given by the equation (2) (see the curve drawn by the solid line shown in FIG. 10A). 1).

Even when the input angular velocity Ω is added, the phase difference of + π / 2 and −π / 2 is not changed by the phase modulator 7, so the phase modulation Δφ by the phase modulator 7 is different between CW light and CCW light. = ± π / 2 and the Sagnac phase difference Δφ _{s, a} phase difference of + π / 2 + Δφ _s and −π / 2 + Δφ _s is generated. Therefore, when the phase difference between the CW light and the CCW light is + π / 2 + Δφ _s , the interference light intensity I ₀ is P ₁ , and when it is −π / 2 + Δφ _s , the interference light intensity I ₀ is P ₂ (FIG. 10 ( b)). P ₁ is given by equation (3) and P ₂ is given by equation (4). Further, the interference light intensity difference ΔI, which is the difference between the interference light intensity P ₁ and the interference light intensity P ₂ , is defined by Expression (5). The direction (clockwise or counterclockwise) of the input angular velocity Ω can be known from the polarity of the interference light intensity difference ΔI.

Equation (5) means that the Sagnac phase difference Δφ _s can be known by observing the interference light intensity difference ΔI.
The Sagnac phase difference Δφ _s is given by equation (6). R is the radius [m] of the optical fiber coil 5, L is the optical fiber length [m] of the optical fiber coil 5, c is the speed of light [m / s], λ is the light source wavelength [m], and n is the optical fiber coil 5. Represents the refractive index of the core portion.

In the closed loop optical interference angular velocity meter, negative feedback control is performed so that the interference light intensity difference ΔI is 0, that is, the Sagnac phase difference Δφ _s is canceled. This will be described with reference to FIG.
The interference light in which the CW light and the CCW light are optically coupled by the optical branching coupler 9 of the optical element 4 enters the optical coupler 3 and is branched. The interference light branched and output from the optical coupler 3 enters the light receiver 6 and is photoelectrically converted. An analog electric signal generated by photoelectric conversion is input to the A / D converter 25 and converted into a digital signal. This digital signal is input to the digital signal processor 35.

The digital signal processing device 35 includes a synchronous detection circuit 36, an integrator 37, a feedback signal generation circuit 38, and a ramp peak value control unit 39.
The digital signal that is the output of the A / D converter 25 is input to the synchronous detection circuit 36. The synchronous detection circuit 36 performs synchronous detection on the digital signal and outputs a signal corresponding to the interference light intensity difference ΔI, that is, the Sagnac phase difference Δφ _s . The integrator 37 receives the output signal of the synchronous detection circuit 36, and outputs an integral value (cumulative addition value of digital values) obtained by time-integrating this input.

The output of the integrator 37 is input to a feedback signal generation circuit 38. The feedback signal generation circuit 38 increases (decreases) the amplitude of the feedback signal by Δφ _s per time τ, and when the amplitude exceeds ± 2 mπ (m is an integer), the flyback control decreases (increases) the amplitude by 2 mπ. To generate a stepped sawtooth feedback signal. Since the closed loop optical interference angular velocity meter performs negative feedback control, the polarity of the feedback signal is set so as to cancel the Sagnac phase difference Δφ _s . The input angular velocity can be detected by the repetition frequency of the feedback signal, which will be described later.

The ramp peak value control unit 39 of the digital signal processing device 35 is based on the output of the synchronous detection circuit 36 and the flyback signal of the feedback signal generation circuit 38, and the maximum phase deviation φ _R of the feedback signal generated by the feedback signal generation circuit 38. Is controlled to be +2 mπ or −2 mπ.

  The output of the feedback signal generation circuit 38 is input to the D / A converter 40 and converted into an analog signal. This analog signal is input to the phase modulator 8 provided on the other of the two routes on the optical element 4. The A / D converter 25, the synchronous detection circuit 36, the integrator 37, the feedback signal generation circuit 38, and the D / A converter 40 are synchronized in signal processing by the timing signal generated by the timing signal generation circuit 50. ing.

  In the configuration shown in FIG. 7, the CW light circulates around the optical fiber coil 5 and then undergoes phase modulation by the phase modulator 8, and the CCW light is phase-shifted by the phase modulator 8 before it circulates around the optical fiber coil 5. Undergo modulation.

FIG. 11 exemplifies the relationship between the phase for modulation (modulation phase) and time for CW light and CCW light that have undergone phase modulation by a feedback signal having a stepped sawtooth wave. Since both lights undergo phase modulation by a feedback signal that is a stepped sawtooth wave of flyback control, the modulation phase of both lights is a stepped sawtooth wave. Here, since the feedback signal is subjected to flyback control that decreases (increases) the amplitude by 2 mπ when the amplitude exceeds ± 2 mπ, each modulation phase of the CW light and the CCW light repeats with a period T.
In the modulation phase of the CW light (shown by a solid line in FIG. 11A) and the modulation phase of the CCW light (shown by a broken line in FIG. 11A), the time point at which the phase modulation is performed is τ Therefore, there is a shift by τ in the time axis direction. Here, the step width of the stepped sawtooth wave as the feedback signal is set to time τ, and the phase difference between the modulation phase of the CW light and the modulation phase of the CCW light is as shown in FIG. It becomes. That is, a phase difference of −Δφ _s or φ _R (2mπ) −Δφ _s is given between the CW light and the CCW light, and a Sagnac phase difference Δφ _s (shown by a broken line in FIG. 11A). Be countered.

The detection of the input angular velocity by the repetition frequency of the feedback signal will be described. The relationship between the repetition frequency f (period T) of the feedback signal and the input angular velocity Ω is given by Expression (7) by using Expression (6) for the period T = 2mπτ / Δφ _s .

  That is, if the repetition frequency f of the feedback signal is measured, the given input angular velocity Ω can be known. Therefore, the feedback signal from the feedback signal generating circuit 38 is input to the angular velocity output unit 70, the repetition rate f of the feedback signal is obtained by the angular velocity output unit 70, and the positive pulse output and the negative pulse output corresponding to the repetition frequency f are obtained. Generate. A positive pulse output indicates an output when a clockwise angular velocity is input, for example, and a negative pulse output indicates an output when a counterclockwise angular velocity is input, for example.

Note that the phase modulator 7 alternately performs + π / 4 and −π / 4 phase modulation on the CW light and the CCW light by the above-described rectangular wave, and relatively + π between the CW light and the CCW light. The reason for giving a phase difference of / 2 and −π / 2 is that when Δφ = ± π / 2, the rate of change of the interference light intensity in equation (8) is maximized, and the sensitivity to the Sagnac phase difference Δφ _s is maximized. Because.

Examples of such a closed loop optical interference angular velocity meter include Patent Documents 1-4.
JP 2006-177893 A JP 2001-74471 A JP 2001-21363 A Japanese Patent Laid-Open No. 10-318760

  Conventionally, in a closed loop optical interference angular velocity meter, the A / D converter 25 outputs the output (analog signal) of the light receiver 6 after the A / D converter 25 performs A / D conversion as described above. Demodulation processing (synchronous detection) was performed on the digital signal.

  In such a configuration, random noise, high frequency noise electrically coupled with a digital clock, or the like is superimposed on the output of the light receiver 6, and A / D conversion is performed as it is. Alias noise accompanying sampling during conversion is included in the demodulated signal. Such noise is an output error factor of the closed loop optical interference angular velocity meter.

  In order to remove the noise, it is conceivable to insert a low-pass filter between the light receiver 6 and the A / D converter 25. This method uses a frequency component of the signal based on the input angular velocity Ω and the noise. Since the frequency component is close, the noise cannot be sufficiently attenuated, and the error factor cannot be completely removed. Further, a filter having a steep frequency characteristic capable of sufficiently removing the noise introduces a waveform distortion in the output of the photoreceiver, which causes a new problem that a demodulation error is caused based on the waveform distortion. Therefore, inserting a low-pass filter between the light receiver 6 and the A / D converter 25 is not an effective means.

  In view of such problems, an object of the present invention is to provide a closed loop optical interference angular velocity meter that realizes a reduction in output error due to noise included in the output of a light receiver.

  In order to solve the above-described problems, the present invention is directed to a light source, an optical fiber coil, and light from the light source branched to enter both ends of the optical fiber coil to be double-ended light and to propagate through the optical fiber coil to return. An optical branching coupler for coupling and interfering the two-way light, a first phase modulator for providing a phase difference between the two-way light by a periodic phase modulation signal, and interference light coupled and interfered by the optical branching coupler. An optical coupler that branches, a light receiver that converts the intensity of interference light from the optical coupler into an electric signal, a demodulator that demodulates the electric signal from the light receiver, and an A / D that performs A / D conversion on the output of the demodulator A digital signal processing device that generates a feedback signal that causes the Sagnac phase difference between the two-way light to be zero based on the outputs of the conversion unit and the A / D conversion unit; and the feedback signal from the digital signal processing device A D / A converter for conversion, and a second phase modulator for providing a phase difference between the two-way light by the output of the D / A converter, and the demodulator samples the electrical signal from the light receiver A first sample hold unit that performs hold processing; a first low-pass filter that receives the output of the first sample hold unit; a second sample hold unit that performs sample hold processing on an electrical signal from the light receiver; and a second sample A second low-pass filter that receives the output of the hold unit, and when the first sample hold unit performs sample processing, the second sample hold unit performs hold processing, and the second sample hold unit performs sample processing. When the first sample hold unit performs hold processing, the sample of the first sample hold unit is sampled every half of the period of the phase modulation signal. Management and the sample processing of the second sample-and-hold unit is a closed loop system optical interference gyro, characterized in that alternately switched.

  In such a closed loop optical interference angular velocimeter, the A / D converter has a first A / D converter for A / D converting the output of the first low-pass filter, and an output of the second low-pass filter is A / D. A second A / D converter for converting, and the digital signal processing device subtracts the output of the second A / D converter from the output of the first A / D converter, and outputs the output of the subtractor. A configuration including an integrator for integration and a feedback signal generation circuit for generating a feedback signal with the output of the integrator as an input can be employed.

  Alternatively, in such a closed loop optical interference angular velocimeter, the A / D converter unit alternately selects the output of the first low-pass filter and the output of the second low-pass filter every half of the period of the phase modulation signal. And an A / D converter for A / D converting the output selected by the multiplexer, the digital signal processing device delaying the output of the A / D converter, and the output of the A / D converter It is possible to employ a configuration including a subtracter that subtracts the output of the delay device from the integrator, an integrator that integrates the output of the subtractor, and a feedback signal generation circuit that generates a feedback signal with the output of the integrator as an input.

  According to the present invention, the electric signal from the light receiver is divided into two systems (first sample hold unit and second sample hold unit), and sampled every half of the period of the phase modulation signal used in the first phase modulator. Since the processing and the hold processing are alternately switched, the frequency component of the output of the sample hold unit of each system is close to the direct current. Therefore, the first low-pass filter and the second low-pass filter applied to the output of the sample hold unit of each system can be a filter having a characteristic that can sufficiently remove noise included in the output of the light receiver. For this reason, the noise contained in the output of the light receiver can be sufficiently removed, and the output error of the closed loop optical interference angular velocity meter is reduced.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a configuration of an embodiment of a closed loop optical interference angular velocity meter according to the present invention. The same components as those of the conventional closed-loop optical interference angular velocity meter shown in FIG.

  The electric signal from the light receiver 6 is input to the demodulator 10. The demodulator 10 includes a first sample hold unit 11 that performs a sample hold process on the electrical signal from the light receiver 6, a first low-pass filter 13 that receives the output of the first sample hold unit 11, and the light receiver 6. The second sample-and-hold unit 12 performs sample-and-hold processing on the electrical signal, and the second low-pass filter 14 that receives the output of the second sample-and-hold unit 12 as an input.

  The first sample hold unit 11 and the second sample hold unit 12 are synchronized in signal processing by the timing signal generated by the timing signal generation circuit 50.

Each process of the 1st sample hold part 11 and the 2nd sample hold part 12 is demonstrated with reference to FIG. 2 and FIG.
When there is no input angular velocity, the electrical signal waveform corresponding to the interference light intensity shown in FIG. 9B is as shown in FIG. In FIG. 2A, the vertical axis represents the amplitude of the electric signal from the light receiver 6, and the horizontal axis represents time. As shown in FIG. 2B, the timing signal input to the first sample hold unit 11 and the second sample hold unit 12 has a phase of π / 2 with respect to the phase modulation signal input to the phase modulator 7. The square wave is shifted. In FIG. 2B, the vertical axis represents amplitude and the horizontal axis represents time.

  The first sample hold unit 11 performs sample processing at the timing signal rising point and holds this value, and the second sample hold unit 12 performs sample processing at the timing signal falling point and holds this value. The cycle of the timing signal is the same as the cycle of the rectangular wave that is the phase modulation signal input to the phase modulator 7. The sample processing by the first sample hold unit 11 and the sample processing by the second sample hold unit 12 are performed at the same timing. The switching is performed alternately every half of the signal cycle. When the first sample hold unit 11 performs sample processing, the second sample hold unit 12 continues the hold process, and when the second sample hold unit 12 performs sample processing, the first sample hold unit 11 11 holds the hold process.

  Therefore, when there is no input angular velocity, the demodulated signal A output from the first sample hold unit 11 and the demodulated signal B output from the second sample hold unit 12 have the same magnitude as shown in FIG. Become. In FIG. 2C, the vertical axis represents the magnitude of the demodulated signal, and the horizontal axis represents time.

  When there is an input angular velocity Ω, the electrical signal waveform corresponding to the interference light intensity shown in FIG. 10B is as shown in FIG. The timing signals input to the first sample hold unit 11 and the second sample hold unit 12 are the same as when there is no input angular velocity, as shown in FIG. Therefore, when the first sample hold unit 11 and the second sample hold unit 12 operate according to the timing signal, the demodulated signal A by the first sample hold unit 11 and the demodulated signal B by the second sample hold unit 12 are shown in FIG. As shown in FIG. The magnitude of the demodulated signal A corresponds to the interference light intensity P1 shown in FIG. 10B, and the magnitude of the demodulated signal B corresponds to the interference light intensity P2 shown in FIG. 10B.

  The demodulated signal A that is the output of the first sample hold unit 11 is input to the first low-pass filter 13. Further, the demodulated signal B that is the output of the second sample hold unit 12 is input to the second low-pass filter 14. As is apparent with reference to FIGS. 2C and 3C, each frequency component of the demodulated signal A by the first sample hold unit 11 and the demodulated signal B by the second sample hold unit 12 is in the vicinity of DC. Therefore, as the first low-pass filter 13 and the second low-pass filter 14, low-pass filters having characteristics that can sufficiently remove noise included in the output of the light receiver 6 can be used.

  The output of the first low-pass filter 13 becomes an input of the first A / D converter 21 included in the A / D converter 20, and A / D conversion is performed. The output of the second low-pass filter 14 is input to the second A / D converter 22 included in the A / D conversion unit 20 and A / D conversion is performed. The first A / D converter 21 and the second A / D converter 22 are synchronized in signal processing by the timing signal generated by the timing signal generation circuit 50.

The outputs of the first A / D converter 21 and the second A / D converter 22 are input to a subtractor 31 included in the digital signal processing device 30, and the subtractor 31 is connected to the first A / D converter 21. Is subtracted from the output of the second A / D converter 22 and the result is output. The output of the subtractor 31 is input to an integrator 37 included in the digital signal processing device 30.
The processing after the integrator 37 is the same as the conventional one.

<Modification>
A modification of the above-described embodiment will be described.
In the embodiment described above, the configuration in which the digital signal processing device 30 includes the ramp peak value control unit 39 is shown in comparison with the conventional example (see FIG. 1). However, when the maximum amplitude of the feedback signal generated by the feedback signal generation circuit 38 is set to be constant without being dynamically controlled, it is not necessary to provide the ramp peak value control unit 39. FIG. 4 shows a configuration when the ramp peak value control unit 39 is not provided.

  The above-described configuration that forms the gist of the present invention can also be applied to a configuration in which the angular velocity output unit 70 obtains an angular velocity output from the output of the integrator 37 and outputs this (see FIG. 5).

  Further, as a configuration that exhibits the same operation as that of the above-described embodiment, the A / D conversion unit 20 and the digital signal processing device 30 may be configured as shown in FIG. That is, the A / D converter 20 is selected by the multiplexer 23 and the multiplexer 23 that alternately select the output of the first low-pass filter 13 and the output of the second low-pass filter 14 every half of the period of the phase modulation signal. An A / D converter 24 for A / D converting the output is included. The multiplexer 23 and the A / D converter 24 are synchronized in signal processing by the timing signal generated by the timing signal generation circuit 50. The digital signal processing device 30 further includes a delay unit 33 that delays the output of the A / D converter 24. In this configuration, since the output of the first low-pass filter 13 and the output of the second low-pass filter 14 are alternately A / D converted and input to the digital signal processing device 30, either one of the delay devices 33 (in this example) , The output of the second low-pass filter 14). The delay time is set to τ.

The output of the A / D converter 24 and the output of the delay unit 33 are input to a subtracter 31 included in the digital signal processing device 30, and the subtracter 31 outputs the output of the delay unit 33 from the output of the A / D converter 24. Is subtracted and the result is output. The output of the subtractor 31 is input to an integrator 37 included in the digital signal processing device 30.
The processing after the integrator 37 is the same as the conventional one.

  In addition to the above-described embodiments, the closed-loop optical interference angular velocity meter according to the present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the gist of the present invention.

The figure which shows embodiment of the closed loop system optical interference angular velocity meter of this invention. The figure which shows the signal processing of the 1st sample hold part 11 and the 2nd sample hold part 12 when there is no input angular velocity. (A) The figure which shows the electrical signal from a light receiver. (B) The figure which shows a timing signal. (C) The figure which shows the demodulated signal A and the demodulated signal B. The figure which shows the signal processing of the 1st sample hold part 11 and the 2nd sample hold part 12 in case there exists input angular velocity. (A) The figure which shows the electrical signal from a light receiver. (B) The figure which shows a timing signal. (C) The figure which shows the demodulated signal A and the demodulated signal B. The figure which shows the modification of embodiment shown in FIG. The figure which shows the modification of embodiment shown in FIG. The figure which shows the modification of embodiment shown in FIG. The figure which shows the structure of the conventional closed loop system optical interference angular velocity meter. An example of a phase modulation signal used in the phase modulator 7. (A) The figure explaining the relationship between phase modulation and interference light intensity when there is no Sagnac phase difference. (B) The figure which shows the relationship between interference light intensity and time when there is no Sagnac phase difference. (A) The figure explaining the relationship between phase modulation and interference light intensity when there is a Sagnac phase difference. (B) The figure which shows the relationship between interference light intensity and time in case there exists a Sagnac phase difference. (A) The figure which shows the relationship between the modulation | alteration phase of CW light which received the phase modulation by the feedback signal, and the modulation phase of CCW light which received the phase modulation by the feedback signal, and time. (B) The figure which shows the phase difference and relationship between the modulation phase of the CW light which received the phase modulation by the feedback signal, and the modulation phase of the CCW light which received the phase modulation by the feedback signal.

Explanation of symbols

2 light source 3 optical coupler 4 optical element 5 optical fiber coil 6 light receiver 7 phase modulator 8 phase modulator 9 optical branching coupler 10 demodulator 11 first sample hold section 12 second sample hold section 13 first low pass filter 14 first Two low-pass filter 20 A / D converter 21 First A / D converter 22 Second A / D converter 23 Multiplexer 24 A / D converter 30 Digital signal processor 31 Subtractor 37 Integrator 38 Feedback signal generator 39 Ramp peak value control unit 40 D / A converter 50 Timing signal generation circuit 60 Phase modulation drive circuit 70 Angular velocity output unit

Claims (3)

In a closed loop optical interference angular velocimeter that detects the angular velocity by performing feedback control so that the phase change of light (Sagnac phase difference) based on the Sagnac effect caused by the angular velocity is zero,
A light source;
An optical fiber coil;
An optical branching coupler for branching the light from the light source and entering both ends of the optical fiber coil to make double-ended light and coupling and interfering with the double-ended light propagating through the optical fiber coil and returning;
A first phase modulator that provides a phase difference due to a periodic phase modulation signal between the light beams;
An optical coupler for branching interference light coupled and interfered by the optical branching coupler;
A light receiver for converting the intensity of the interference light from the optical coupler into an electrical signal;
A demodulator that demodulates the electrical signal from the light receiver;
An A / D converter for A / D converting the output of the demodulator;
A digital signal processing device that generates a feedback signal based on the output of the A / D converter so that the Sagnac phase difference between the two-way light is zero;
A D / A converter for D / A converting the feedback signal from the digital signal processing device;
A second phase modulator that provides a phase difference between the two-way light by the output of the D / A converter,
The demodulator
A first sample and hold unit that performs a sample and hold process on the electrical signal from the light receiver;
A first low-pass filter that receives the output of the first sample-and-hold unit, and
A second sample and hold unit that performs a sample and hold process on the electrical signal from the light receiver;
A second low-pass filter having the output of the second sample-and-hold unit as an input,
When the first sample hold unit performs sample processing, the second sample hold unit performs hold processing. When the second sample hold unit performs sample processing, the first sample hold unit performs hold processing. A closed-loop optical interference angular velocity meter, wherein the sample processing of the first sample hold unit and the sample processing of the second sample hold unit are alternately switched every half of the period of the phase modulation signal. The A / D converter is
A first A / D converter for A / D converting the output of the first low-pass filter;
A second A / D converter for A / D converting the output of the second low-pass filter,
The digital signal processor is
A subtractor for subtracting the output of the second A / D converter from the output of the first A / D converter;
An integrator for integrating the output of the subtractor;
The closed-loop optical interference angular velocity meter according to claim 1, further comprising: a feedback signal generation circuit that generates the feedback signal with the output of the integrator as an input. The A / D converter is
A multiplexer that alternately selects the output of the first low-pass filter and the output of the second low-pass filter for each half of the period of the phase modulation signal;
An A / D converter for A / D converting the output selected by the multiplexer;
The digital signal processor is
A delay device for delaying the output of the A / D converter;
A subtractor for subtracting the output of the delay device from the output of the A / D converter;
An integrator for integrating the output of the subtractor;
The closed-loop optical interference angular velocity meter according to claim 1, further comprising: a feedback signal generation circuit that generates the feedback signal with the output of the integrator as an input.

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