JP3531918B2 - Optical gyro, driving method thereof, and signal processing method - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD OF THE INVENTION

The present invention relates to an optical gyro device for detecting rotation by using a ring resonator type semiconductor laser, and more particularly to a semiconductor optical gyro device capable of detecting a rotation direction, a driving method thereof and a signal processing method.

[Prior art]

Conventionally, as a gyro that detects the rotation of an object, that is, the angular velocity, a mechanical gyro having a rotor and a vibrator, and an optical gyro are known. Optical gyro
Since it can be activated instantaneously and has a wide dynamic range, it is innovating in the gyro field. Optical gyro,
There are ring laser type gyros, optical fiber gyros, passive type ring resonator gyros and the like. A ring laser type gyro using a gas laser has already been put to practical use in aircraft and the like. Further, as a small and highly accurate ring laser type gyro, a gyro composed of a ring resonator type semiconductor laser on a semiconductor substrate has been proposed. As this publicly known document, Japanese Patent Publication No. Sho 62-39836 and Japanese Patent Laid-Open No. 4-17
4317 and Japanese Patent Publication No. 6-38529.

A gyro composed of a ring resonator type semiconductor laser is characterized in that the element size can be further reduced, power consumption can be reduced, and start-up time can be shortened as compared with a mechanical gyro having a vibrator. It is an element suitable for use in an image stabilization control device that prevents shooting errors due to camera shake of a camera and a video camera.

In such a gyro, the beat frequency has information on the angular velocity. Then, in order to detect the beat frequency, there are a method of converting the vibration frequency of the beat signal into a voltage signal by a frequency-voltage conversion circuit, a method of directly detecting the beat frequency by a frequency counter, and the like.

[Problems to be Solved by the Invention]

However, the conventional gyro composed of the ring resonator type semiconductor laser cannot detect the rotational direction from the output signal as it is. Therefore, a minute rotational vibration (dither) is added and the rotational direction is detected from the correlation between the dither and the signal. Further, Japanese Patent Publication No. Sho 62-39836 and Japanese Patent Laid-Open No. 4-174317 do not show a method for detecting the rotational direction.

In Japanese Patent Publication No. 6-38529, it is stated that the rotation direction can be detected by comparing the phase information of the signals obtained from the two electrodes. The treatment method is not specifically shown.

[0008] Therefore, a first object of the present invention is to provide an optical gyro that accurately detects the rotation direction.

A second object of the present invention is to provide a method of driving an optical gyro that detects the direction of rotation with high accuracy.

A third object of the present invention is to provide a signal processing method for an optical gyro that accurately detects the rotation direction.

[Means for Solving the Problems]

In order to achieve the above-mentioned first object, the optical gyro of the first invention of the present application is such that the cycle of impedance variation between terminals changes according to the applied angular velocity, and an electrical terminal for detecting the impedance variation. An optical gyro provided with three or more ring resonator type semiconductor lasers on a plane that is not perpendicular to each other so that they are optically independent of each other , and at least when the angular velocity in a certain direction increases. A first ring resonator type semiconductor laser having a low impedance fluctuation frequency, and a second ring having a high impedance fluctuation frequency when the impedance fluctuation period of the first ring resonator type semiconductor laser decreases. Both the resonator-type semiconductor laser and the third ring in which the frequency of impedance fluctuation increases when the absolute value of the angular velocity increases And a vessel-type semiconductor laser. In the above structure, since the ring resonator type semiconductor lasers are optically independent from each other, the first and second optical gyros are rotated regardless of which direction the optical gyro is rotated.
The frequency of the impedance variation of the ring resonator type semiconductor laser is low on one side and high on the other side. Also, the third
In the ring resonator type semiconductor laser, the frequency of impedance fluctuation is proportional to the absolute value of the angular velocity of rotation except for the region where the lock-in greatly affects the small angular velocity.

In the above structure, since the respective ring resonator type semiconductor lasers are optically independent from each other, the first and second ring resonators are irrespective of which direction the optical gyro is rotated. One of the frequencies of impedance fluctuation of the semiconductor laser is low and the other is high. Further, in the third ring resonator type semiconductor laser, the frequency of impedance fluctuation is proportional to the absolute value of the angular velocity of rotation except for the region where the angular velocity has a small effect on the small angular velocity.

Therefore, in a region where the angular velocity is small, signal processing is performed on the frequency change of impedance fluctuation in the first and second ring resonator type semiconductor lasers. It is possible to separate the noise with the same sign change and the signal with the opposite sign change depending on the angular velocity between these ring resonator type semiconductor lasers, so that the signal-to-noise ratio can be improved and the rotation can be improved. It is possible to accurately obtain the angular velocity including the sign indicating the direction. Further, in the third ring resonator type semiconductor laser, in a region where the angular velocity is large and which is not affected by lock-in,
The angular velocity can be obtained from the frequency change of the impedance fluctuation in the third ring resonator type semiconductor laser. Since the angular velocity is not affected by the fluctuation of the impedance fluctuation frequency at rest, the angular velocity can be obtained with high accuracy. Also in this angular velocity region, the signal processing is performed on the frequency change of the impedance fluctuation in the first and second ring resonator type semiconductor lasers, and the angular speed becomes the change of the opposite sign between these ring resonator type semiconductor lasers. Since the dependent signal can be separated, the direction of rotation can be known from this code.

[0014] To achieve the first object, an optical gyro of the second invention of the present application, the first invention odor <br/> Te, the first and second ring resonator type semiconductor Laser
Orbiting in the opposite direction in each optical resonator,
And having two laser beams having different oscillation frequencies when stationary, the magnitude relationship between the oscillation frequencies of the clockwise laser beam and the counterclockwise laser beam is reversed between the two lasers. In the third ring resonator type semiconductor laser, the oscillation frequency of the laser light that circulates in the opposite direction in the optical resonator is the same at rest.

In the above-mentioned structure, in the first and second ring resonator type semiconductor lasers, two laser lights that circulate in opposite directions in the respective optical resonators and have different oscillation frequencies at rest are An optical beat is generated in the optical resonator. Further, since the first and second ring resonator type semiconductor lasers are optically independent from each other, when the gyro equipped with them is rotated, the oscillation frequencies of the respective laser lights change independently. Since the magnitude relationship between the oscillation frequencies of the clockwise laser light and the counterclockwise laser light is reversed between the two ring resonator type semiconductor lasers, the light in these optical resonators is The beat frequency increases on the one hand and decreases on the other hand when the gyro rotates.

Further, in the third ring resonator type semiconductor laser, when the angular velocity of rotation is large and there is no influence of lock-in, the oscillation frequencies of the clockwise and counterclockwise laser light are changed independently to cause optical resonance. The light beat is generated inside the vessel. The frequency of this light beat is proportional to the absolute value of the angular velocity. Any change in the frequency of the optical beat in these first to third ring resonator type semiconductor lasers can be detected as a change in the frequency of the impedance change between the terminals.

Therefore, in a region where the angular velocity is small, signal processing is performed on the frequency change of impedance fluctuation in the first and second ring resonator type semiconductor lasers. It is possible to separate the noise with the same sign change and the signal with the opposite sign change depending on the angular velocity between these ring resonator type semiconductor lasers, so that the signal-to-noise ratio can be improved and the rotation can be improved. It is possible to accurately obtain the angular velocity including the sign indicating the direction. Further, in the third ring resonator type semiconductor laser, in a region where the angular velocity is large and which is not affected by lock-in,
The angular velocity can be obtained from the frequency change of the impedance fluctuation in the third ring resonator type semiconductor laser. Since the angular velocity is not affected by the fluctuation of the impedance fluctuation frequency at rest, the angular velocity can be obtained with high accuracy. Also in this angular velocity region, the signal processing is performed on the frequency change of the impedance fluctuation in the first and second ring resonator type semiconductor lasers, and the angular speed becomes the change of the opposite sign between these ring resonator type semiconductor lasers. Since the dependent signal can be separated, the direction of rotation can be known from this code.

In order to achieve the above first object, the optical gyro of the third invention of the present application is the same as that of the first invention ,
In the first and second ring resonator type semiconductor lasers, a part of the optical waveguide has a taper portion, and the taper portion gradually widens the width of the optical waveguide along the clockwise laser light propagation direction. The first part and the second part where the width of the optical waveguide gradually narrows
In the first ring resonator type semiconductor laser, the first portion is longer than the second portion,
In the second ring resonator type semiconductor laser, the second
Is longer than the first portion, and the third ring resonator type semiconductor laser does not have the taper portion.

In the above structure, the taper portions of the first and second ring resonator type semiconductor lasers provide a difference in oscillation frequency between the clockwise clockwise laser light and the counterclockwise laser light at rest. This is the introduced structure. Further, in the first and second ring resonator type semiconductor lasers, the magnitude relation of the lengths of the first portion and the second portion of the tapered portion is reversed. As a result, the dependence of the resonator loss on the orbiting direction is reversed between the first and second ring resonator type semiconductor lasers, whereby the clockwise laser light and the counterclockwise laser light are reversed. And the magnitude relationship of the oscillation frequency is reversed.

More specifically, the taper portion operates as follows in more detail. The laser light in the optical resonator propagates while repeating total reflection at the interface of the optical waveguide. At the tapered portion, the incident angle to the interface of the optical waveguide deviates from the total reflection condition, so that a waveguide loss occurs. Since the incident angle on the interface at the taper portion differs depending on the circulating direction, there is a difference in loss, and the resonator loss depends on the circulating direction. Since there is a difference in the resonator loss, a difference occurs in the oscillation threshold of the ring laser, and when two laser lights having different orbiting directions coexist and oscillate, a difference in the photon number density occurs. This difference in the photon number density gives a difference in the oscillation frequency of the laser light due to the non-linear effect.

Further, in the above structure, since the third ring resonator type semiconductor laser has no taper portion, there is no dependency of the resonator loss in the orbiting direction, and the clockwise laser light and the counterclockwise laser light when stationary. The oscillating frequencies of are identical.

In the first and second ring resonator type semiconductor lasers, two laser lights that circulate in opposite directions in the respective optical resonators and have different oscillation frequencies at rest are generated in the optical resonators. To generate a light beat. Further, since the first and second ring resonator type semiconductor lasers are optically independent from each other, when the gyro equipped with them is rotated, the oscillation frequencies of the respective laser lights change independently. Since the magnitude relationship between the oscillation frequencies of the clockwise laser light and the counterclockwise laser light is reversed between the two ring resonator type semiconductor lasers, the light in these optical resonators is The beat frequency increases on the one hand and decreases on the other hand when the gyro rotates.

In the third ring resonator type semiconductor laser, when the angular velocity of rotation is large and there is no influence of lock-in, the oscillation frequencies of the clockwise and counterclockwise laser beams change independently to cause optical resonance. The light beat is generated inside the vessel. The frequency of this light beat is proportional to the absolute value of the angular velocity of rotation. Any change in the frequency of the optical beat in these first to third ring resonator type semiconductor lasers can be detected as a change in the frequency of the impedance change between the terminals.

Therefore, in a region where the angular velocity is small, signal processing is performed on the frequency change of impedance fluctuation in the first and second ring resonator type semiconductor lasers. It is possible to separate the noise with the same sign change and the signal with the opposite sign change depending on the angular velocity between these ring resonator type semiconductor lasers, so that the signal-to-noise ratio can be improved and the rotation can be improved. It is possible to accurately obtain the angular velocity including the sign indicating the direction. Further, in the third ring resonator type semiconductor laser, in a region where the angular velocity is large and which is not affected by lock-in,
The angular velocity can be obtained from the frequency change of the impedance fluctuation in the third ring resonator type semiconductor laser. Since the angular velocity is not affected by the fluctuation of the impedance fluctuation frequency at rest, the angular velocity can be obtained with high accuracy. Also in this angular velocity region, the signal processing is performed on the frequency change of the impedance fluctuation in the first and second ring resonator type semiconductor lasers, and the angular speed becomes the change of the opposite sign between these ring resonator type semiconductor lasers. Since the dependent signal can be separated, the direction of rotation can be known from this code.

Further, in order to achieve the above-mentioned second object, an optical gyro driving method of a fourth invention of the present application is to drive each of the plurality of ring resonator type semiconductor lasers with a constant current,
A voltage change is detected from the electric terminal.

Further, the order to achieve the second object, the driving method for an optical gyroscope of the fifth invention of the present application, the first origination
A method of driving a light of the optical gyro, the first, second
Each of the second and third ring resonator type semiconductor lasers is driven at a constant voltage, and the fluctuation of the driving current is detected from the electric terminal.

In the above structure, the driving method of constant voltage driving and constant current driving makes it possible to take out the impedance variation of the element with a simple circuit structure and realize easy connection with various signal processing circuits. In the signal processing circuit, a signal depending on the angular velocity, which has a change in opposite sign between the first and second ring resonator type semiconductor lasers, and a fluctuation in static beat frequency and noise, which have a change in the same sign, are generated. Separation is possible and the signal-to-noise ratio can be improved. Further, it becomes possible to switch the signal processing method according to the angular velocity, and when the angular velocity is large, the angular velocity can be accurately known from the signal from the third ring resonator type semiconductor laser. In this way, it is possible to accurately know the angular velocity and the rotation direction in a wide angular velocity range.

In order to achieve the third object, the signal processing method of the optical gyroscope according to the sixth invention of the present application is the first method .
The method of processing a signal from an optical gyro according to the invention of claim 1, wherein one or more specific ones are selected from the first, second and third ring resonator type semiconductor lasers according to the value of the angular velocity, The angular velocity is obtained using the signal from the selected ring resonator type semiconductor laser.

In the above structure, by selecting the first and second ring resonator type semiconductor lasers, the beat frequency can be changed in accordance with the angular velocity from a region having a small angular velocity. The direction of rotation and angular velocity can be known after improving the signal-to-noise ratio. Further, in a region where the angular velocity is not affected by the lock-in, a beat frequency proportional to the absolute value of the angular velocity can be obtained from the third ring resonator type semiconductor laser, so that the angular velocity can be obtained with high accuracy. Therefore, by selecting an element according to the angular velocity and performing signal processing, it is possible to obtain an angular velocity signal with high accuracy and small influence of noise. In addition, the response speed of the gyro can be improved by selecting an element having a high frequency of impedance fluctuation and using the signal from this for signal processing.

In order to achieve the third object, the signal processing method of the optical gyroscope according to the seventh invention of the present application is the sixth invention.
In the invention , when the absolute value of the angular velocity is smaller than a predetermined value, the angular velocity is obtained using only the signals from the first and second ring resonator type semiconductor lasers.

In the above structure, even when the absolute value of the angular velocity is smaller than the predetermined value, the lock-in does not affect the first and second ring resonator type semiconductor lasers.
The impedance fluctuation frequency changes according to the angular velocity.
By performing signal processing on these signals, the rotation direction and angular velocity can be known.

More specifically, no matter which direction the optical gyro is rotated, one of the frequencies of impedance fluctuation of the first and second ring resonator type semiconductor lasers is low and the other is high. . By the signal processing, the signal that depends on the angular velocity, which changes the opposite sign between these ring resonator type semiconductor lasers, and the noise, which changes the same sign, can be separated to improve the signal-to-noise ratio. It is possible to accurately obtain the angular velocity including the sign indicating the direction.

In order to achieve the third object, the signal processing method of the optical gyroscope according to the eighth invention of the present application is the sixth invention.
In the invention , when the absolute value of the angular velocity is larger than a predetermined value, the frequency of impedance fluctuation in the third ring resonator type semiconductor laser is calculated,
It is characterized by obtaining the absolute value of the angular velocity.

In these configurations, when the absolute value of the angular velocity is larger than a predetermined value and there is no influence of lock-in, the beat frequency at rest does not exist in the third ring resonator type semiconductor laser, and therefore the fluctuation thereof. Since the impedance variation frequency proportional to the absolute value of the angular velocity is generated without being affected by, the absolute value of the angular velocity can be known accurately from this. At this time, the rotation direction can be known by comparing the frequency of impedance variation between the terminals and the reference frequency in at least one of the first and second ring resonator type semiconductor lasers. Alternatively, the rotation direction can be known by comparing the frequency of impedance fluctuation between the terminals of the first and second ring resonator type semiconductor lasers. In this way, the angular velocity and the rotation direction can be obtained with high accuracy without being affected by the fluctuation of the beat frequency at rest.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be described below with reference to the drawings.

First Embodiment FIG. 1 is a plan view and a sectional view of a first embodiment of an optical gyro of the present invention. Reference numeral 10 is an optical gyro according to the present invention, reference numerals 11, 12 and 13 are ring resonator type semiconductor lasers, and reference numerals 14 and 15 are portions (tapered portions) provided in a part of the optical waveguide where the waveguide width changes. Is. In the ring resonator type semiconductor laser, the counterclockwise rotation mode 16
There is a clockwise orbit mode 17.

Three ring resonator type semiconductor laser devices 1
1, 12 and 13 were manufactured as follows.

First, the semiconductor multi-layer structure shown in the element cross-sectional view of FIG. 1 was formed by a metal organic chemical vapor deposition method. That is, on the n-InP substrate 102, an undoped InGaAsP optical guide layer 103 (thickness: 0.1 μm) having a composition of 1.3 μm is formed.
5 μm), 1.55 μm composition undoped InGaAs
P active layer, 104 (thickness 0.1 μm), 1.3 μm composition undoped InGaAsP optical guide layer 105 (thickness 0.15 μm), p-InP clad layer 106 (thickness 1.5 μm), p-InGaAs cap The layer 107 was crystal-grown. A photoresist was applied, and the mask pattern was exposed and developed to form a ring resonator-shaped resist pattern. A ring resonator type semiconductor laser having a height of 3 μm and made of a high-mesa ridge waveguide was formed by reactive ion etching using chlorine gas. Cr
/ Au is vapor-deposited on the ridge waveguide to form the p-electrode 108.
And AuGe / Ni / Au was vapor-deposited on the lower side of the wafer to form an n-electrode 101. After being alloyed in a hydrogen atmosphere, the interface between the p and n electrodes and the semiconductor was brought into ohmic contact.

Now, the shape of the waveguide forming the ring waveguide will be described in detail below. Each of the ring resonator type semiconductor lasers 11 and 12 has an asymmetrical shape. That is, the tapered portion 14 (and 15) has a first portion in which the width of the optical waveguide is wide and a second portion in which the width of the optical waveguide is narrow along the counterclockwise (clockwise) propagation direction of the laser light. The first portion and the second portion have different lengths. In the illustrated example, the first portion is extremely short. The shape of the resonators of the ring resonator type semiconductor laser 11 and the ring resonator type semiconductor laser 12 is mirror-symmetrical to each other.

When arranging the plurality of ring resonator type semiconductor lasers 11, 12 and 13 formed on the same substrate, the lasers are arranged at intervals so that the laser beams are not coupled to each other. In order to avoid the influence of evanescent light, the interval is set to approximately 15 mm or more. Also,
At the asymmetric taper portion, since laser light emitted outside the waveguide due to mode conversion exists, it is noted that the taper portions do not face each other or are not arranged on the same axis. Further, an absorber in which the semiconductor layer is left without being etched may be formed between the respective ring resonator type semiconductor lasers. Further, an insulating film and an electrode metal may be formed on the side surface and the upper surface of the absorber to serve as a light shield. Further, a light shield may be formed by an insulating film formed on the side surface of the element and an electrode metal formed on the insulating film. These light shields may be arranged so as to be inclined so that the reflected light on the surface of the light shield does not return to the ring resonator type semiconductor laser. The element arrangement, the absorber, and the light shield can reduce the interaction between the ring resonator type semiconductor lasers. In addition, the reflected light is prevented from coupling the clockwise laser light and the counterclockwise laser light, thereby suppressing the lock-in.

Ring resonator type semiconductor lasers 11, 12,
A circuit as shown in FIG. 2 was used to independently inject current into 13 and detect the terminal voltage.

In FIG. 2, 10 is an optical gyro according to the present invention, 11, 12 and 13 are ring resonator type semiconductor lasers, 201, 202 and 203 are drive current input terminals, and 204, 205 and 206 are couplings. Capacitors, 207, 208, 209 are comparators, 21
Reference numerals 0, 211 and 212 are counters, 213 is a signal processing circuit, 214 is an output terminal, and 215 and 216 are error signal output terminals.

Each of the terminals 201, 202 and 203 is connected to a power source and driven at a constant current above the oscillation threshold current of the ring resonator type semiconductor laser. At the injection current above the oscillation threshold, the ring resonator type semiconductor laser 11 (and 1
In 2), the clockwise and counterclockwise laser lights exist independently.

The oscillation frequency of the laser light at rest differs between the clockwise laser light and the counterclockwise laser light. This is due to the action of the asymmetric taper portion of the ring resonator type semiconductor laser 11 (and 12) as described below. The laser light propagates while repeating total reflection at the interface of the optical waveguide, but at the tapered portion, the incident angle to the interface of the optical waveguide changes, so that waveguide loss occurs. Since the incident angle at the taper portion differs depending on the circulating direction, the loss varies, and the resonator loss depends on the circulating direction.

Since there is a difference in the resonator loss depending on the circulating direction of the laser light, a difference occurs in the oscillation threshold of the ring resonator type semiconductor laser depending on the circulating direction. In the state where the two laser lights coexist, a difference occurs in the photon number density of the two laser lights due to the nonlinear optical effect. There is the following relationship between the oscillating frequencies f _{j of} two coexisting laser beams (modes) and the photon number density S _j , and it can be seen that if there is a difference in the photon number density, there is a difference in the oscillating frequency. Here, Φ _i is a phase, Ω is a resonance angular frequency, σ _i is a mode pull-in coefficient, ρ _i is a coefficient showing self-extrusion of modes, and τ _ij is a coefficient showing mutual push-out of modes. However, i , j = 1 , 2; i ≠ j. Since the oscillation frequencies f ₁₀ and f ₂₀ of the laser light are different when stationary, a beat occurs at a frequency Δf ₀ = f ₂₀ −f ₁₀ .

On the other hand, laser oscillation occurs in the ring resonator type semiconductor laser 13 with an injection current above the oscillation threshold. In the ring resonator type semiconductor laser 13 having no taper portion, there is no difference in the photon number density of the two modes at rest, and the oscillation frequencies are equal.

Here, when the ring resonator type semiconductor laser rotates clockwise at an angular velocity Ω, the oscillation frequency of the clockwise first laser light is Δf ₁ = 2SΩ as compared with the oscillation frequency f ₁₀ when it is not rotating. / (Λ ₁ L) (2) decrease. Where S is the area surrounded by the ring resonator, L
Is the optical path length, and λ ₁ is the wavelength of the clockwise laser light in the medium. At the same time, the oscillation frequency of the counterclockwise second laser light is Δf ₂ = 2SΩ / (λ ₂ compared to the oscillation frequency f ₂₀ when not rotating. L) (3) increase. Here, λ ₂ is the in-medium wavelength of the second laser light.

Since the clockwise first laser light and the counterclockwise second laser light coexist in the ring resonator, the oscillation frequencies of the first laser light and the second laser light are different from each other. Beat light corresponding to the frequency of the difference is generated. When rotating,
The beat frequency Δf is Is. The beat light causes pulsation of population inversion at the same frequency Δf and changes impedance between terminals. Therefore, when the constant current driving is performed, the voltage fluctuation at the frequency Δf is observed in the inter-terminal voltage. However, the observed frequency is always positive, so | Δf
| Is obtained.

As described above, if the oscillation frequencies f ₁₀ and f ₂₀ of the laser light are different at rest, as shown in FIG. 3, the beat Δf ₀ = (f ₂₀ −f ₁₀ ) is obtained at rest. As shown in the straight line portion of FIG. 3, the beat frequency increases or decreases according to the rotation direction during rotation.

The relationship between the frequency of the voltage signal obtained from the ring resonator type semiconductor laser and the angular velocity in this manner will be described with reference to FIG.

In FIG. 3, the straight line portions of solid lines a and c and the extended broken line thereof are Δf expressed by the equation (4). When the difference between the oscillation frequencies of the two laser beams is less than a certain threshold value (broken line portion), the two laser beams may be in a strong coupling state and two-mode independent laser oscillation may not be possible. At this time, the beat of light and the periodic fluctuation of the voltage cannot be observed.

In such a case, the relationship between the angular velocity and the voltage signal is as shown by the solid line in FIG. If the solid line of a is (f ₂₀ −f ₁₀ )> 0, the dotted line of c is (f ₂₀
Shows a case of ₂₀ -f ₁₀₎ <0. Both are Δ
f ₀ = | f ₂₀ −f ₁₀ |. The solid line of b is (f
The case where ₂₀ −f ₁₀ ) = 0 is shown. This is an example in which two modes are strongly coupled at rest due to backscattering. If the backscattering is sufficiently small and the two laser beams are weakly coupled even at rest, beat light is generated with rotation.

The relationship between the angular velocities and the frequency of the voltage signal of the ring resonator type semiconductor lasers 11 and 12 which are mirror-symmetrical to each other under the same driving condition is shown in a and c of FIG. It is symmetrical with respect to Ω . In addition, the beat frequency Δf ₀ at rest Are equal. Also, b
The characteristic of the ring resonator type semiconductor laser 13 indicated by the solid line is the characteristic of the ring resonator type semiconductor laser 13 having no taper portion. Here, three ring resonator type semiconductor lasers 1
1, 12 and 13 have the same ratio S / L between the area S surrounded by the ring resonator and the optical path length L of the ring resonator so that the beat frequency has the same inclination with respect to the angular velocity.

With the signal processing circuit shown in FIG. 2, the angular velocity was detected as follows. Capacitors 204, 205, 206
The voltage fluctuation signal from each ring resonator type semiconductor laser is fetched via the
The frequency signal was shaped into a rectangular wave by the 8 and 209.
The number of pulses within a predetermined time was counted by the counters 210, 211 and 212. The number of pulses from each element was taken into the signal processing circuit 213, and the following processing was performed to obtain an angular velocity signal and an error signal for adjusting the drive current.

First, the angular velocity Ω where the effect of lock-in in the ring resonator type semiconductor laser 13 without taper can be ignored.
c was preset as a reference. The processing in the signal processing circuit 213 was changed as follows in the range of | Ω | <Ωc and the range of Ωc ≦ | Ω |.

In the range of | Ω | <Ωc, the difference f ₋ between the beat frequencies of the first and second ring resonator type semiconductor lasers 11 and 12 is , And the fact that it is directly proportional to the angular velocity was used. Where λ
_{j, cw, λ j, ccw} (J = 1, 2) are oscillation wavelengths of the clockwise and counterclockwise laser light in the j-th ring resonator type semiconductor laser, which are almost equal to each other. Therefore, this frequency difference was divided by 2 to obtain a signal output that is proportional to the angular velocity including the code indicating the rotation direction. Also,
The sum f ₊ of the signal frequencies from the ring resonator type semiconductor laser 11 and the ring resonator type semiconductor laser 12 was obtained. This amount is f ₊ = Δf ₀₁ + Δf ₀₂ and does not depend on the angular velocity of the gyro. Where Δf
_0j is the beat frequency of the j-th ring resonator type semiconductor laser at rest. When this amount fluctuates, since the beat frequency at rest in at least one of the two ring resonator type semiconductor lasers fluctuates, the detection of the angular velocity by the equation (5) includes an error. Therefore, this amount is taken out as error signals 215 and 216 and returned as an error signal to the feedback control circuit of the drive current. That is, the amount set in advance by the setting unit 217 (f ⁺ corresponding to twice the beat frequency at rest)
The sum signals 215 and 216 of the beat frequencies are used as the error signals for the initial value of the. According to this, the adjusting unit 219 adjusts the drive current of the ring resonator type semiconductor laser.

When the drive current of the ring resonator type laser is increased above the threshold value, the difference in light intensity between the two modes shown in equation (1) also increases, and the beat frequency at rest tends to increase. Therefore, the drive current may be decreased when the beat frequency at rest increases, and the drive current may be increased when the beat frequency at rest decreases.

In the range of Ωc ≦ │Ω│, the frequency of the signal from the ring resonator type semiconductor laser 13 without taper is
(2S | Ω | / L) · (1 / λ _{13, cw} + 1 / λ
_{13, ccw} ), which is proportional to the absolute value of the angular velocity and is not affected by the beat frequency fluctuation at rest, so this is used as the signal output. Further, the frequencies of the signals from the ring resonator type semiconductor laser 11 and the ring resonator type semiconductor laser 12 may be compared to determine the rotation direction (sign of Ω). Alternatively, a predetermined beat frequency Δf at rest
_ref and ring resonator type semiconductor laser 11 or 12
The direction of rotation may be determined by comparing the frequencies of the signals from the. In the range of Ωc ≦ | Ω |, even when Δf _ref deviates from the true stationary beat frequency Δf ₀₁ (or Δf ₀₂ ), if the deviation is smaller than 4SΩc / Lλ, the correct rotation direction can be obtained.

The beat frequencies from the ring resonator type semiconductor laser 11 and the ring resonator type semiconductor laser 12 and the angular velocities measured by the respective elements obtained by using the equation (4), and the ring resonator type semiconductor Using the difference in angular velocity obtained from the laser 13 as an error signal, feedback control was performed on the driving conditions of the ring resonator type semiconductor laser 11 and the ring resonator type semiconductor laser 12 to suppress the beat frequency fluctuation at rest.

By the way, when the absolute value of the angular velocity is larger and the lock-in phenomenon occurs in any of the tapered ring resonator type semiconductor lasers 11 to 12,
The feedback control was suspended for the device. Therefore, the error signal 215 for controlling the ring resonator type semiconductor laser 11 and the error signal 216 for controlling the ring resonator type semiconductor laser 12 are provided as different outputs.

As described above, when the angular velocity is small, by subtracting the beat frequency, a signal proportional to the angular velocity including the sign indicating the rotation direction is obtained without using the reference value of the beat frequency at rest. At the same time, feedback control was performed to stabilize the beat frequency at rest regardless of angular velocity, and an optical gyro with excellent stability could be obtained. Further, when the angular velocity was large, a signal proportional to the absolute value of the angular velocity was obtained from the ring resonator type semiconductor laser without the taper portion. At this time, the rotation direction was obtained by comparing signals from the tapered ring resonator type semiconductor laser. Further, at this time, feedback control may be performed on the driving condition of the tapered ring resonator type semiconductor laser with reference to the beat frequency of the ring resonator type semiconductor laser without taper, and an optical gyro with excellent stability may be obtained. did it.

In this embodiment, InG is used as the semiconductor material.
Although an aAsP / InP system was used, GaAs system, ZnSe
It may be a material system capable of oscillating laser by current injection such as a system or InGaN system. Also, an example has been shown in which the feedback control system controls the drive current, but feedback control may be performed on the temperature adjustment circuit of the element to stabilize the beat frequency at rest. In this case, if the threshold current of the element is lowered by lowering the temperature of the element, the intensity difference between the two modes at the same drive current increases, and the beat frequency at rest tends to increase.
The temperature of the element may be raised when the beat frequency at rest is increased, and the temperature of the element may be lowered when the beat frequency at rest is reduced.

Further, in the range of | Ω |> Ωc, the driving condition of the ring resonator type semiconductor lasers 11 and 12 having the tapered portion is set with reference to the beat frequency from the ring resonator type semiconductor laser 13 having no tapered portion. In addition to the method of obtaining the angular velocity for each element as described above, as a feedback method for controlling the, a tapered ring resonator type semiconductor laser is used as in the signal processing in the range of | Ω | <Ωc. 1
A method of using the difference between the angular velocity obtained as the difference between the beat frequencies from 1 and 12 and the angular velocity obtained from the ring resonator type semiconductor laser 13 as the error signal may be used.

FIG. 11 shows a compact camera having an image stabilization system using the gyro of this embodiment. This camera has a function of performing shake correction on the optical axis 111 with respect to vertical shake and horizontal shake of the camera indicated by arrows 112 and 113. Reference numeral 114 is a correction means, and 115 and 116.
Is a vibration detection device in which the gyro and the drive circuit of this embodiment are contained in one package, 117 is a CPU (camera microcomputer), and 118 is a correction lens.

The output signals from the vibration detection devices 115 and 116 correspond to the angular velocities of the vertical shake and the horizontal shake of the camera, respectively. This signal is input to the camera microcomputer 117. When the release button of the camera is fully pressed, the camera microcomputer 117 corrects the signal according to the focal length and the distance to the subject, and the correction means 114 is driven by this signal. In the correction unit 114, the correction lens 118 is moved in the biaxial directions in the plane orthogonal to the optical axis in accordance with the drive signal to perform the shake correction, thereby preventing a shooting error due to the shake of the camera.

Since the vibration detecting device including the gyro of the present embodiment is small in size and consumes less power, it is possible to construct an anti-vibration system suitable for a compact camera.

[Second Embodiment] FIG. 4 is a perspective view showing another example of the optical gyro according to the present invention, showing a case where a plurality of ring resonator type semiconductor lasers are provided in one housing.

In FIG. 4, 40 is a stem used as a housing, 41 is a common electrode connected to the stem, and 42, 4
3 and 44 are ring resonator type semiconductor lasers and 4 respectively.
Reference numeral 5 is an electrode corresponding to each element of the ring resonator type semiconductor lasers 42, 43 and 44, and 46 is a wire connecting each electrode 45 and the ring resonator type semiconductor lasers 42, 43 and 44. Here, the ring resonator type semiconductor lasers 42, 4
The respective layer configurations of 3 and 44 are the same as those of the ring resonator type semiconductor laser shown as the first embodiment.

Further, as shown in FIG. 5, in the ring resonator type semiconductor lasers 42 and 44, a first portion in which the width of the optical waveguide is gradually widened along the clockwise laser light propagation direction, There are taper portions 421 and 441 each of which has a second portion in which the width of the optical waveguide is gradually narrowed, and the circumference lengths of the resonators are the same with each other, and the two portions are mirror image symmetric. The circumference of the resonator of the ring resonator type semiconductor laser 43 is determined by the ring resonator type semiconductor lasers 42 and 44.
Is the same as. However, there is no tapered portion as shown in FIG.

In the above structure, the ring resonator type semiconductor lasers 42, 43, 44 are individually bonded to the stem 41 by soldering, using the substrate side of the ring resonator type semiconductor lasers 42, 43, 44 as a common electrode, and the ring resonator type semiconductor lasers 42, 43, 44 are individually bonded. The electrode on the cap layer side of was connected to the individual electrode 45 by each wire 46.

As shown in FIG. 4, the device is connected so that a current can flow, and while the current is being injected, the voltage change between the electrodes of each ring resonator type semiconductor laser is detected. In order to perform current injection and voltage detection with the same electrode, a circuit as shown in FIG. 6 was used here.

In FIG. 6, 40 is an optical gyro according to the present invention, 42, 43 and 44 are ring resonator type semiconductor lasers, 601, 602 and 603 are drive current input terminals, and 604, 605 and 606 are couplings. Capacitors 607, 608, 609 are f-V conversion circuits, 61
Reference numeral 0 is a signal processing unit. 611 is a signal output terminal,
612 is a control signal output terminal, 613 is a drive current ON / O
This is a control signal output terminal for the FF.

From each of the terminals 601, 602 and 603, the ring resonator type semiconductor lasers 42, 43, and 42 are supplied with a current higher than the oscillation threshold current of the ring resonator type semiconductor laser.
44 is driven with a constant current. A ring resonator type semiconductor laser 42 in which a gain is generated by injecting a current above an oscillation threshold
At 43 and 44, clockwise and counterclockwise laser lights are present, respectively. In particular, in the ring resonator type semiconductor lasers 42 and 44 having the tapered portion, the clockwise and counterclockwise laser lights are independent and the oscillation frequencies are different from each other, so that a beat of light is generated.

FIG. 7 shows the relationship between the angular velocity and the frequency of the beat signal from each ring resonator type semiconductor laser. Here, three ring resonator type semiconductor lasers 42, 43, 4
In No. 4, the ratio S / L of the area S surrounded by the ring resonator and the optical path length L of the ring resonator is made equal so that the inclination of the beat frequency with respect to the angular velocity is the same. In particular, the driving conditions of the tapered ring resonator type semiconductor lasers 42 and 44 were controlled so that the beat frequencies at the time of rest were matched, as will be described later.

The signal processing circuit shown in FIG. 6 detects the angular velocity as follows. Capacitors 604, 605, 606
The signal of the voltage fluctuation from each ring resonator type semiconductor laser is taken in via the f-V conversion circuits 607 and 60.
The voltage was converted into a voltage according to the frequency of the beat signal by 8, 609. Further, in the signal processing unit 610, the following processing was performed to obtain an angular velocity signal 611, an error signal 612 for adjusting the drive current, and a control signal 613 for turning on / off the drive current.

First, the angular velocity Ω where the influence of lock-in in the ring resonator type semiconductor laser 43 without taper can be ignored.
c and Ωs having an angular velocity smaller than this, were set in advance as a reference. Similar to the first embodiment, depending on the value of the measured angular velocity Ω, the range of | Ω | <Ωc and Ωc ≦ | Ω
The processing in the signal processing circuit 213 was changed within the range of |.

In the range of | Ω | <Ωc, a signal (including a sign indicating the rotation direction) proportional to the angular velocity, which is obtained as the difference between the beat frequencies of the two ring resonator type semiconductor lasers 42 and 44, is used as the signal output. did. Also, by summing the signal frequencies from the ring resonator type semiconductor lasers 42 and 44, the sum of the beat frequencies at rest can be obtained regardless of the angular velocity. Feedback control was performed.

In the range of Ωc ≦ │Ω│, a signal which is proportional to the absolute value of the angular velocity can be obtained from the ring resonator type semiconductor laser 43 having no taper, and this is used as the signal output. The rotation direction (sign of Ω) is the same as the ring resonator type semiconductor laser 4
The frequency of the signal from 2,44 was determined by comparison with a reference (beat frequency at rest). Further, the difference between the angular velocity obtained from each of the beat frequencies of the ring resonator type semiconductor lasers 42 and 44 by using the equation (4) and the angular velocity from the ring resonator type semiconductor laser 43 is defined as an error signal, Feedback control was performed on the driving conditions of the ring resonator type semiconductor lasers 42 and 44 to suppress the fluctuation of the beat frequency at rest. Particularly, in the present embodiment, since the optical path lengths of the resonators of the ring resonator type semiconductor lasers 42 and 44 and the ring resonator type semiconductor laser 43 are equal and the inclination of the beat frequency with respect to the angular velocity is the same, the fV conversion output 607 is The static beat frequency of the ring resonator type semiconductor laser 42 was obtained as the sum or difference of the fV conversion outputs 608 (depending on the rotation direction). Also, f-V conversion output 609 and f
The static beat frequency of the ring resonator type semiconductor laser 44 was obtained as the sum or difference of the −V conversion outputs 607 (depending on the rotation direction). In this way, the process for extracting the control error signal is simplified.

Further, when the angular velocity thus obtained is | Ω | ≦ Ωs (<Ωc), the control signal 613 for supplying the current to the ring resonator type semiconductor laser 43 is turned off and the ring resonator is turned on. Driving of the semiconductor laser 43 is stopped to reduce power consumption. At this time, since | Ω | <Ωc, the angular velocity is obtained only by the signals from the ring resonator type semiconductor lasers 42 and 44. The hysteresis region width Δs shown in FIG. 7 may be set for the switching angular velocity Ωs. For example, the absolute value of angular velocity Ω is (Ωs +
Driving is started when Δs is exceeded, and the angular velocity is (Ωs−
By stopping the drive when it becomes smaller than Δs), frequent On / Of is performed when the angular velocity slightly changes in the vicinity of Ωs.
The repetition of f can be avoided.

In the above description, an example in which the drive current of the ring resonator type semiconductor laser 43 is set to On / Off is shown. Furthermore, the second switching angular velocity Ωs2 is set to an angular velocity larger than Ωc, and an angular velocity higher than this is set. When the absolute value is large, it is possible to stop driving of the two ring resonator type semiconductor lasers with a taper whose beat frequency is low. In a region where the absolute value of the angular velocity is larger than Ωs2, it is possible to stop driving both of the tapered ring resonator type semiconductor lasers.

In the above description, an example in which the stem is used as the case has been shown, but the case according to the present invention may be of any form as long as a plurality of ring resonator type semiconductor lasers can be hybrid-mounted. For example, a case may be used. In the above-described two embodiments, the ring resonator shape of the ring resonator type semiconductor laser has a quadrangle shape, but a ring path having a closed path such as a circular shape or a triangular shape may be applied.

[Third Embodiment] FIG. 8 is a view showing another embodiment of the optical gyro according to the present invention.

In FIG. 8, 80 is an optical gyro according to the present invention, 81 and 82 are ring resonator type semiconductor lasers having a tapered portion, and 83 is a ring resonator type semiconductor laser having no tapered portion. The layer structure of the laser is similar to that of the first embodiment.

FIG. 9 is a diagram showing an optical gyro drive circuit according to the present invention. In FIG. 9, 901 and 90
2, 903 are drive current input terminals, 904, 905, 90
6 is a coupling capacitor, 907, 908, 909
Is a comparator, 910, 911 and 912 are counters,
913 is a signal processing circuit, 914 is a signal output terminal, 915
Is an error signal output terminal. Further, 916 is an injection current setting unit 916, 917 is an error signal input terminal for the current control block, and 918 is an injection current adjustment unit.

The ring resonator type semiconductor lasers 81 and 82 have a tapered portion, and the resonator shapes are mirror images. In addition, the ring resonator type semiconductor laser 83 has a shorter resonator circumference length than the ring resonator type semiconductor lasers 81 and 82, and the ratio S / of the area surrounded by the resonator and the resonator circumference length S /.
L is small.

Drive current input terminals 901, 902 and 903
Of the ring resonator type semiconductor lasers 81, 82,
A constant current drive is performed when the oscillation threshold currents of the respective 83 are exceeded. However, the injection current is changed here. As a result, the ring resonator type semiconductor laser 81 (and
2, 83), clockwise and counterclockwise laser light exists. In the ring resonator type semiconductor lasers 81 and 82 having the tapered portion, the clockwise and counterclockwise laser lights are independent and the oscillation frequencies thereof are different due to the existence of the tapered waveguide portion. A beat signal is generated even when stationary. By the way, the frequency of the beat signal depends on the light intensity difference between two laser modes in different circling directions as shown in the equation (1). Therefore, when the injection currents of the two ring resonator type semiconductor lasers are different, the stationary beat frequencies of the two ring resonator type semiconductor lasers are also different. Further, in the ring resonator type semiconductor laser 83 having no taper portion, the frequencies of the two laser lights are equal to each other at rest, and no beat occurs.

Next, FIG. 10 shows the relationship between the rotational angular velocity Ω of the gyro and the beat frequency Δf. The solid and dotted lines show the characteristics of the ring resonator type semiconductor lasers 81 and 82, respectively. Here, the absolute value of the inclination of the beat frequency Δf at the time of rotation with respect to the angular velocity Ω expressed by the equation (4) is 2S (1 /
λ ₂ + 1 / λ ₁ ) / L, the two ring resonator type semiconductor lasers have almost the same wavelength of laser light, and S / L
If they are equal, it can be considered that both elements are equal. The characteristics of the ring resonator type semiconductor laser 83 are also shown by the alternate long and short dash line in FIG.

Such a ring resonator type semiconductor laser 8
The voltage fluctuation signals from 1, 82, and 83 are fed to the capacitor 8
04, 805, 806, and the frequency signal is shaped into a rectangular wave by comparators 807, 808, 809. The number of pulses within a predetermined time was counted by the counters 810, 811, 812, and arithmetic processing was performed by the signal processing circuit.

That is, in the angular velocity range shown by a in the figure, from the difference in beat frequencies of the two ring resonator type semiconductor lasers 81 and 82, the difference in the beat frequency at rest (Δf
_01- Δf ₀₂ ) was subtracted to obtain a signal proportional to the angular velocity.

In the angular range shown by b1 in the figure, the beat frequency Δ of the ring resonator type semiconductor laser 82 at rest is
f ₀₂ The beat frequency of the ring resonator type laser 83 is (−2) times (the ratio of L / S of the ring resonator type lasers 82 and 83 and the rotation direction (−1)). Then, a signal proportional to the angular velocity including the sign was obtained.

In the angular range indicated by b2 in the figure, the beat frequency Δf ₀₂ at rest from the beat frequency of the ring resonator type semiconductor laser 81. Was added to the one obtained by subtracting the beat frequency of the ring resonator type laser 83 (L / S ratio of the ring resonator type lasers 81 and 83) to obtain a signal 914 proportional to the angular velocity.

In the angular velocity range indicated by a in the figure, 2
From the sum of the beat frequencies of the two ring resonator type semiconductor lasers 81 1 and 82 2, the amount (Δf ₀₁ + Δf) that does not depend on the angular velocity is obtained.
₀₂ ). Further, in the angular range indicated by b1 in the figure, the beat frequency of the ring resonator type semiconductor laser 82 is reduced by twice the beat frequency of the ring resonator type laser 83 to obtain an amount that does not depend on the angular velocity (Δf ₀₂ ) Was asked. Further, in the angular range indicated by b2 in the figure, the beat frequency of the ring resonator type semiconductor laser 81 is reduced by a value obtained by doubling the beat frequency of the ring resonator type semiconductor laser 83 to obtain an amount (Δf that does not depend on the angular velocity). ₀₁ ). These amounts are taken out as an error signal 915 and returned as an error signal to the drive current feedback control circuit.
That is, an amount set in advance by the setting unit 916 (Δf ₀₁ + Δf ₀₂ , Δf ₀₂ , depending on the angular velocity region,
The error signal 915 is used as the error signal 917 for any one of Δf ₀₁ ), and the adjusting unit 918 adjusts the laser drive current.

As described above, by the calculation using the beat frequencies from the three elements, a signal proportional to the angular velocity including the sign indicating the rotation direction was obtained. At the same time, feedback control that stabilizes the signal independent of the angular velocity was performed, and an optical gyro with excellent stability could be obtained.

In the three embodiments described so far, the case where the constant current driving is performed to detect the voltage variation between the terminals according to the angular velocity of the element has been described, but the element receives the voltage while driving the element. As is clear from the measurement principle that the element impedance changes depending on the angular velocity, the element is driven at a constant voltage to detect the current change, or the impedance change is measured by another impedance measurement method. You can also know

【The invention's effect】

As described above, according to the first to third inventions of the present application, the optical gyro capable of accurately detecting the angular velocity of rotation and the rotation direction is obtained.

Further, according to the fourth and fifth inventions, the impedance variation of the element can be observed with a simple circuit configuration,
A method for driving an optical gyro, which can detect the angular velocity and direction of rotation with high accuracy, has been obtained because it can be easily connected to various signal processing circuits.

Further, according to the sixth to eighth inventions, the signal processing method of the optical gyro which can detect the angular velocity of rotation and the rotation direction with high accuracy is obtained.

[Brief description of drawings]

[0098]

FIG. 1 is an optical gyro according to a first embodiment of the present invention.

FIG. 2 is an optical gyro and drive according to the first embodiment of the present invention;
Signal processing circuit

FIG. 3 shows the frequency and angular velocity of the beat signal of the optical gyro according to the first embodiment of the present invention.

FIG. 4 is an optical gyro according to a second embodiment of the present invention.

FIG. 5 is a plan view of an optical gyro according to a second embodiment of the present invention.

FIG. 6 is an optical gyro and drive according to a second embodiment of the present invention;
Signal processing circuit

FIG. 7 shows the frequency and angular velocity of the beat signal of the optical gyro according to the second embodiment of the present invention.

FIG. 8 is a plan view of an optical gyro according to a third embodiment of the present invention.

FIG. 9 is an optical gyro and drive according to a third embodiment of the present invention,
Signal processing circuit

FIG. 10 shows the frequency and angular velocity of the beat signal of the optical gyro according to the third embodiment of the present invention.

FIG. 11 is a conceptual diagram of a camera that detects vibrations by the optical gyroscope according to the first embodiment of the present invention to perform vibration isolation.

[Explanation of symbols]

[0099] 10, 40, 80 Optical gyro element Ring resonator type semiconductor laser device 42,43,44 ring resonator type semiconductor laser device 81, 82, 83 ring resonator type semiconductor laser device 14, 15, 421, 441 Tapered part 16 Counterclockwise orbital mode light 17 clockwise orbit mode light 207, 208, 209 comparator 907, 908, 909 Comparator 210, 211, 212 counter 910, 911, 912 counter 607, 608, 609 f-V conversion circuit 213, 610, 913 Signal processing unit

─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-7-139954 (JP, A) JP-A-7-146150 (JP, A) JP-A-10-261837 (JP, A) JP-A-2002-22456 (JP, A) JP 2002-22459 (JP, A) JP 2002-22458 (JP, A) JP 3323844 (JP, B2) JP 3363862 (JP, B2) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01C 19/64-19/72 G03B 5/00 H01S 3/083 H01S 5/10

Claims (8)

(57) [Claims] 1. A ring resonator type semiconductor laser having three or more ring resonator type semiconductor lasers, each of which has an electrical terminal for detecting the impedance variation, in which the cycle of impedance variation between the terminals varies depending on the applied angular velocity, and is optically independent of each other. And a first ring resonator type semiconductor laser, which is an optical gyroscope provided on a surface that is not perpendicular to each other , in which the frequency of impedance fluctuation becomes low at least when the angular velocity in a certain direction increases, A second ring resonator type semiconductor laser whose frequency of impedance fluctuation increases when the cycle of impedance fluctuation of the first ring resonator semiconductor laser decreases, and a frequency of impedance fluctuation which increases when the absolute value of the angular velocity increases. An optical gyro including a third ring resonator type semiconductor laser having a high wavelength. 2. The first and second ring resonator type semiconductor lasers circulate in opposite directions in their respective optical resonators and oscillate two laser lights having different oscillation frequencies when stationary, The magnitude relationship between the oscillation frequencies of the clockwise laser light and the counterclockwise laser light is reversed between the two lasers, and the third ring resonator type semiconductor laser is provided in the optical resonator. 2. The optical gyro according to claim 1, wherein the oscillation frequencies of the laser beams that circulate in opposite directions are the same when stationary. 3. The first and second ring resonator type semiconductor lasers have a taper portion in a part of an optical waveguide, and the taper portion gradually extends in the clockwise optical waveguide propagation direction. Of the first ring resonator type semiconductor laser, the first ring resonator type semiconductor laser includes a first portion having a wide width and a second portion having a gradually narrowing width of the optical waveguide.
Of the second ring resonator type semiconductor laser, the second part of the second ring resonator type semiconductor laser is longer than the first part, and the third ring resonator type semiconductor laser has the tapered portion. The optical gyro according to claim 1, wherein the optical gyro is absent. 4. A method for driving an optical gyro according to claim 1 , wherein each of the first, second and third ring resonator type semiconductor lasers is driven with a constant current, and is driven from the electrical terminal. An optical gyro driving method characterized by detecting voltage fluctuations. 5. A method for driving an optical gyro according to claim 1 , wherein each of the first, second and third ring resonator type semiconductor lasers is driven at a constant voltage, and is driven from the electric terminal. An optical gyro driving method, which is characterized by detecting a change in driving current. 6. A method of processing a signal from an optical gyro according to claim 1, wherein the first signal is output according to a value of an angular velocity .
A specific one or two or more are selected from the first, second and third ring resonator type semiconductor lasers, and the angular velocity is obtained by using the signal from the selected ring resonator type semiconductor laser. Optical gyro signal processing method. When the absolute value of 7. angular velocity is smaller than a predetermined value, according to claim 6, wherein the obtaining the angular velocity by using only the signal from the first and second ring resonator type semiconductor laser Optical gyro signal processing method. 8. When the absolute value of the angular velocity is larger than a predetermined value, arithmetic processing is performed based on the frequency of impedance fluctuation in the third ring resonator type semiconductor laser to obtain the absolute value of the angular velocity. The signal processing method of the optical gyro according to claim 6 .