JP2001124565A - Optical gyro and method using the same for detecting rotation direction - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical gyro which has a small insertion loss at a light extracting part, a small oscillation threshold and a wide allowance range for assembly errors. SOLUTION: A light extracted from a laser mode 19 in the counterclockwise direction by a directional coupler 12 is emitted from a light extracting part 14. A light extracted from a laser mode 18 in the clockwise direction by the directional coupler 12 is emitted from a light take part 15 after deflected by a total reflection mirror 13. Optical waveguides of these light extracting parts similar to the directional couplers are provided having an optical gain by injecting a current, thereby compensating for the absorption loss. The light extracting parts 14 and 15 are directed slightly inwardly by with respect to a parallel position relation, whereby the intensity of light taken in the vicinity of photodetectors 16 and 17 is increased. Two output lights form interference fringes in the vicinity of the photodetectors 16 and 17. The interval between center of two photodetectors 16 and 17 is an (N/2+1/4) times (N is an integer) a pitch A of the interference fringe pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical gyro and a method for detecting a rotation direction using the same, and more particularly, to an optical gyro apparatus for detecting rotation using a semiconductor ring laser, and driving and signal processing thereof.

[0002]

2. Description of the Related Art Conventionally, as a gyro for detecting the rotation of an object, that is, an angular velocity, a mechanical gyro having a rotor and a vibrator and an optical gyro are known. Since the optical gyro can be activated instantaneously and has a wide dynamic range,
It is bringing innovation in the gyro field. The optical gyro includes a ring laser gyro, an optical fiber gyro, a passive ring resonator gyro, 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, a semiconductor laser gyro integrated on a semiconductor substrate as a small and high-precision ring laser gyro is disclosed in, for example, Japanese Patent Application Laid-Open No. Hei 5-288556.

As a signal processing of such a laser gyro, there is a method of converting a vibration frequency of an output signal into a voltage signal by a frequency-voltage conversion circuit. The frequency-voltage conversion circuit includes a circuit for processing an analog signal and a circuit for counting the number of pulses by binarizing the signal.

[0004]

However, the conventional ring laser type gyro cannot detect the rotation direction from the output signal as it is, and applies a minute rotation vibration (dither) to the gyro.
The direction of rotation was detected from the correlation between dither and signal.

[0005] In a ring laser gyro that extracts light from a ring laser element and receives light with another element, backscattering at the light extraction section causes an optical difference between clockwise light and counterclockwise light. Due to the coupling, the lock-in phenomenon occurred in a region of small angular velocity. This is because the oscillation frequency is pulled into the frequency of one mode due to the coupling between the clockwise light and the counterclockwise light, and no signal is output.

Accordingly, a first object of the present invention is to provide a ring laser gyro for detecting a rotation direction without applying mechanical minute vibration (dither).

A second object of the present invention is to provide a ring laser gyro having a small oscillation threshold while suppressing the insertion loss of the light extraction portion.

A third object of the present invention is to provide an optical gyro element capable of electrical correction and having a wide allowable range of element assembly errors.

A fourth object of the present invention is to provide a ring laser gyro in which all components can be formed monolithically on a substrate and the direction of rotation can be detected.

A fifth object of the present invention is to provide a ring laser gyro which is not affected by fluctuations in the interference fringe pitch.

[0011]

An optical gyro according to the present invention for solving the above-mentioned problems comprises a semiconductor ring laser having excitation means, a ring-shaped resonator, and a light extraction part which is a part of the resonator. An output unit for emitting light obtained from the light extraction unit to the outside of the waveguide, and a plurality of light receiving elements disposed at positions where two lights obtained from the output unit overlap.

In the method of detecting a rotation direction according to the present invention, the fluctuation period of the interference fringe pattern formed at the position of the light receiving element is determined by the light intensity signal from the plurality of light receiving elements using the optical gyro described above. And the moving direction are detected, and the angular velocity and the rotating direction are obtained from this.

In the method of detecting a rotation direction according to the present invention, the movement of the interference fringe pattern formed at the position of the array element is determined by the light intensity signal from the plurality of light receiving elements using the above-mentioned optical gyro. The speed and the direction are detected, and the angular speed and the rotation direction are obtained from this.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below with reference to mathematical expressions.

[Embodiment 1] In Embodiment 1, an optical gyro includes a semiconductor ring laser having an excitation unit, a ring-shaped resonator, and a light extraction unit which is a part of the resonator, and a light gyro from the light extraction unit. It has an output section for emitting the obtained light out of the waveguide, and a plurality of light receiving elements placed at positions where two lights obtained from the output section overlap.

In the above configuration, a clockwise rotation mode and a counterclockwise rotation mode exist independently in a ring resonator in which a gain is generated by current injection. When the element has no angular velocity with respect to the inertial system, there is no difference between the oscillation frequencies of the clockwise mode and the counterclockwise mode, and the laser oscillation is in the resonator mode with the gain peak wavelength of the active layer.

At the light extraction section of the ring resonator, a part of the clockwise light and a part of the counterclockwise light are extracted outside the ring resonator and emitted from the output part. At a predetermined place, that is, at the observation plane, these clockwise and counterclockwise lights arrive at an overlap to form interference fringes.

For simplicity, let us consider a case where the observation surface is separated from the light output means and each light can be handled as a parallel beam. When the two beams enter at an angle of ± ε / 2 with respect to the normal to the observation surface, the intersection of the incidence surface and the observation surface is defined as the X axis, and clockwise light is emitted from the positive direction of the X axis. When the counterclockwise light is incident from the negative direction of the X axis, the light intensity distribution I on the observation surface is represented by the following equation.

I = Io (1 + cosΦ) where Φ = 2πεX / λ + 2π (f1-f2) t where λ is the wavelength of light when the semiconductor laser gyro is stationary, and f1 and f2 are clockwise, respectively. And the oscillation frequency of the counterclockwise light. When the semiconductor laser gyro is stationary, the interference fringes do not change with time because f1 = f2. The pitch of the interference fringes is λ / ε
It can be seen that

Here, the semiconductor laser gyro has an angular velocity Ω
, The oscillation frequency of the first clockwise laser beam becomes Δf1 = 2SΩ / λ compared with the non-rotational case.
Decrease by L. Where S is the area surrounding the ring resonator,
L is the optical path length of the laser. At the same time, the oscillation frequency of the second laser beam in the clockwise direction becomes Δf
2 = 2SΩ / λL. At this time, the light intensity distribution I oscillates at a beat frequency (f2−f1) = 4SΩ / λL, and the interference fringe pattern moves in the positive direction of x.

When the laser gyro rotates counterclockwise, it vibrates at a beat frequency (f1−f2) = 4SΩ / λL, and the interference fringes move in the negative direction of x.

Even when the two lights are not parallel beams, the interference fringe pitches represented by the intensity distribution I are unequally spaced, but the movement of the interference fringes according to the beat remains unchanged.

Therefore, a plurality of light receiving elements are arranged on the observation surface at intervals different from the pitch of the interference fringes and light intensity vibrations having different phases are detected, whereby the absolute value of the angular velocity of rotation is known from the vibration frequency. The moving direction of the interference fringes can be detected from the phase difference of the vibration. Therefore, the ring laser gyro can detect the rotation direction.

[Second Embodiment] In the second embodiment, the light extraction unit is a directional coupler.

In the above configuration, the directional coupler functions as an optical branching element that keeps a desired ratio of the laser mode light of the ring resonator inside the ring resonator and extracts the rest outside the ring resonator. In the directional coupler, the light travels in the waveguide direction and the power distribution ratio changes between the two waveguides, but the coupling length of the directional coupler is large at wavelengths near the laser gain peak. By selecting such that part of the light stays in the ring resonator, it is possible to suppress the loss of the directional coupler for the laser mode and to obtain an optical gyro having a low oscillation threshold and a low drive current.

[Third Embodiment] In the third embodiment, the light extraction unit is a multi-mode interferometer.

In the above configuration, the multimode interferometer is
It functions as an optical branching element that keeps a desired ratio of the laser mode light of the ring resonator inside the ring resonator and extracts the rest outside the ring resonator. In particular, it is known that by connecting a plurality of tapered multi-mode waveguides in which the width of the multi-mode waveguide changes, a phase shift can be given to the connection portion and the output branching ratio can be arbitrarily controlled. By using a multimode interferometer designed so that most of the light stays in the ring resonator at wavelengths near the laser gain peak,
An optical gyro with a low driving current and a small oscillation threshold can be obtained while suppressing loss in the ring laser mode.

[Embodiment 4] Embodiment 4 is characterized in that the light extraction portion is a low refractive index layer / semiconductor layer multilayer mirror.

In the above structure, the low-refractive index layer / semiconductor layer multi-layer reflecting mirror is a light splitting element that keeps a desired ratio of the laser mode light of the ring resonator inside the ring resonator and extracts the rest outside the ring resonator. Function as A multi-layer reflecting mirror that provides high reflectivity at wavelengths near the laser gain peak ensures that most of the light stays in the ring resonator, thereby suppressing loss in the ring laser mode and reducing the oscillation threshold. An optical gyro for driving current can be used.

[Fifth Embodiment] In the fifth embodiment, the plurality of light receiving elements are a light receiving element group formed in an array or a CCD array.

In the above configuration, the light receiving elements are formed of two or more light receiving elements in an array or a CCD array.
Signal processing such as interpolation becomes possible, and even when the pitch of the interference fringes on the observation surface where the light receiving element is located is different from the design, the moving direction of the interference fringes can be detected with high sensitivity by the signal processing. In other words, even if the position of the light receiving element deviates from the designed observation surface, the moving direction of the interference fringes can be detected with high sensitivity by signal processing even when the pitch of the complementary fringes is electrically different from the design. That is, even if the position of the light receiving element deviates from the designed observation plane, it can be electrically corrected, and the allowable range of the error in assembling the element can be increased.

[Embodiment 6] In Embodiment 6, as the plurality of light receiving elements, the same layer configuration as the ring laser is used, or a laser element having the same layer configuration as the ring laser is used.

With the above configuration, the ring resonator laser, the optical element for changing the propagation direction of the output light, and the light receiving element have the same layer configuration, so that all the components can be easily monolithically formed.

[Embodiment 7] In Embodiment 7, the fluctuation period and the moving direction of the interference fringe pattern formed at the position of the light receiving element are detected based on the light intensity signals from the plurality of light receiving elements, and the angular velocity and the rotation are determined from this. Get directions.

In the above configuration, as can be seen from the above-described equations of the light intensity distributions I, Δf1, and Δf2, the angular velocity of the element can be obtained from the fluctuation period of the light intensity signal in each light receiving element. The direction of movement of the interference fringe pattern, that is, the direction of rotation, can be detected from the phase difference of the fluctuation of the light intensity signal in step (1).

[Eighth Embodiment] In the eighth embodiment, at least two intervals between the plurality of light receiving elements are different from an integral multiple of the pitch of the interference fringe pattern.

In the above configuration, the light intensity signals obtained from the plurality of light receiving elements provided at intervals different from the integral multiple of the interference fringe pitch change with time in the same oscillation cycle and have different signal phases. The direction of rotation can be detected from this phase difference.

More specifically, a case will be described as an example where two light receiving elements are placed so that the distance between the centers is N / 2 + ／ times the pitch の of the interference fringe pattern (N is an integer). . The x coordinate of the position of the first light receiving element is-を /
4. Assuming that the x coordinate of the position of the second light receiving element is 2 °, the sin fringe pattern sin (2π (f1-
f2) A signal corresponding to t) is output from the second light receiving element to co.
It can be seen that a signal corresponding to s (2π (f1-f2) t) is obtained. As a result, when the light intensity at the second light receiving element is close to the maximum and the light intensity at the first light receiving element is increasing, the interference fringe moves in the negative direction of x, When the light intensity at the first light receiving element decreases, it can be seen that the interference fringes are moving in the positive x direction.

[Embodiment 9] In the real embodiment 9, the interference pattern formed at the position of the light receiving element group is moved by the light intensity signal from the array of light receiving element groups placed at the position where the light overlaps. The speed and direction are detected, and the angular speed and rotation direction are obtained from this.

In the above configuration, the interference fringe pattern is received by the array-like elements, and the intensity signal is subjected to signal processing to obtain a function representing the interference fringe pattern. By examining the time change, the speed and direction of the movement of the interference fringe pattern are detected, and the angular velocity and the rotation direction can be obtained. This is also effective when interference fringe patterns that are not equally spaced are formed.

The same signal processing can always be performed even when the element temperature changes and the laser oscillation wavelength fluctuates and the interference fringe pitch fluctuates.

[Embodiment 10] In Embodiment 10, the fluctuation period and the moving direction of the interference fringe pattern formed at the position of the light receiving element are detected based on the light intensity signals from the plurality of light receiving elements, and the angular velocity and I try to get the direction of rotation.

In the above arrangement, the light intensity signals obtained from the plurality of light receiving elements provided at intervals different from the integral multiple of the interference fringe pitch change with time in the same oscillation cycle and have different signal phases. The direction of movement of the interference fringe pattern can be obtained from this phase difference to detect the direction of rotation.

[Eleventh Embodiment] In the eleventh embodiment, the speed and direction of the movement of the interference fringe pattern formed at the position of the array element are detected based on the light intensity signals from the plurality of light receiving elements, and the angular velocity and the rotation direction are determined. I'm trying to get

In the above configuration, the interference fringe pattern is received by the array-like elements, and the intensity signal is subjected to signal processing to obtain a function representing the interference fringe pattern. By examining the time change, the speed and direction of the movement of the interference fringe pattern are detected, and the angular velocity and the rotation direction can be obtained. This is also effective when interference fringe patterns that are not equally spaced are formed. In addition, even when the element temperature changes, the oscillation wavelength of the laser fluctuates, and the interference fringe pitch fluctuates, the same signal processing can always be performed.

[0046]

FIG. 1A is a plan view of an optical gyro according to a first embodiment. 10 is an optical gyro, 11 is a ring resonator type semiconductor laser device, 12 is a directional coupler provided in a part of the waveguide, 13 is a total reflection mirror, 14 and 15 are light extraction parts, and 16 and 17 are It is a photo detector. 1 for a ring resonator type semiconductor laser device
There are a clockwise rotation mode shown in FIG. 8 and a counterclockwise rotation mode shown in FIG. In the directional coupler 12, there are an input light 121 and output lights 122 and 123.

FIG. 1B is a sectional view of the ring resonator type semiconductor laser device 11, the directional coupler 12, the output units 14, 15, and the photodetectors 16, 17. A semiconductor multilayer structure having such a cross-sectional structure was formed by metal organic chemical vapor deposition.

That is, on the n-InP substrate 102,
Non-doped InGaAsP light guide layer 103 having a composition of 1.3 μm (thickness 0.15 μm), undoped InGaAsP active layer 104 having a composition of 1.55 μm (thickness 0.1 μm)
m) A non-doped InGaAsP light guide layer 105 (thickness: 0.15 μm) and a p-InP cladding layer 106 (thickness: 1.5 μm) having a composition of 1.3 μm and a p-InGaAs cap layer 107 were crystal-grown. Apply photoresist,
The mask pattern was exposed and developed to form a resist pattern having a waveguide shape and a mirror shape. A high mesa-shaped ridge waveguide having a height of 3 μm and a photodetector portion directional coupler were formed by reactive ion etching using chlorine gas. Cr / Au was deposited on the upper part of the ridge waveguide and on the photodetector to form a p-electrode 108. AuGe / Au was deposited on the lower side of the wafer to form an n-electrode 101. The alloy was formed in a hydrogen atmosphere, and the p- and n- electrodes were brought into ohmic contact.

Next, laser oscillation of the ring resonator type semiconductor device 11 will be described. Since the refractive index is different between the semiconductor layer and air, reflection occurs at the interface. If the refractive index of the semiconductor layer is 3.5, total reflection occurs when the angle between the laser beam and the normal to the interface between the semiconductor and air is 16.6 degrees or more. In the ring resonator type laser element 11, the angle formed by the normal of the waveguide and the semiconductor / air interface at the corner mirror at the bent portion of the waveguide is 45 degrees, which satisfies the condition of total reflection. In the mode of total reflection, the threshold gain is smaller by the mirror loss than in the other modes, so that the laser oscillates at a low injection current level. The concentration of the gain in the oscillation mode suppresses the oscillation in the other modes.

The semiconductor laser device 11 of this embodiment oscillated at a threshold value of 15 mA.

In the ring resonator, a clockwise rotation mode 18 and a counterclockwise rotation mode 19 exist independently. When the optical gyro has no angular velocity with respect to the inertial system, there is no difference between the oscillation frequencies of the clockwise mode and the counterclockwise mode, and the laser oscillates at the gain peak wavelength of the active layer. When the optical gyro is rotating at a certain angular velocity, there is a difference between the oscillation frequency of the clockwise rotation mode 18 and the oscillation frequency of the counterclockwise rotation mode 19.

The directional coupler 12 extracts a part of the light oscillated by the laser in the ring resonator. To compensate for the absorption loss, a gain is given to the directional coupler 12 by injecting a current equal to or less than the oscillation threshold current density of the ring resonator.

The counterclockwise laser mode 19 corresponds to the input light 1
When the light enters from the left side of the directional coupler 12 as 21, the two waveguides on the right side of the directional coupler provide an output light 122 staying in the ring resonator and an output light 123 extracted out of the ring resonator. . Coupling length L of directional coupler
Is adjusted, the ratio between the output lights 122 and 123 can be changed. Also, since this ratio indicates chromatic dispersion,
At the gain peak wavelength of the active layer, the output light 122 and the output light 1
It is possible to manufacture a directional coupler in which most of the light becomes the output light 122 with a branching ratio of 23, for example, 20: 1. In this case, the loss in the ring resonator type semiconductor element 11, that is, the insertion loss of the directional coupler is small,
It becomes easier to obtain laser oscillation at a low threshold.

At this time, the clockwise laser mode 18 similarly enters the directional coupler from the right side, most of the light stays in the ring resonator, and some light is extracted from the resonator. The branch ratio at this time is the same as the ratio when the light enters the directional coupler from the left. Even when the oscillation frequency of the ring laser changes due to rotation, the chromatic dispersion of the branch characteristic of the directional coupler is not so steep and does not substantially affect the branch ratio.

The light extracted from the laser mode 19 in the counterclockwise direction by the directional coupler 12 is emitted from the light extraction unit 14. The light extracted from the clockwise laser mode 18 by the directional coupler 12 is reflected by the total reflection mirror 13.
Then, the light is emitted from the light extraction unit 15 after being turned back.
Similarly to the directional coupler, the optical waveguides of these light extraction sections are provided with optical gain by current injection to compensate for the absorption loss.

The light extraction portions 14 and 15 are slightly inward with respect to the parallel positional relationship, and the intensity of the light extracted near the photodetectors 16 and 17 is increased. In the vicinity of the photodetectors 16 and 17, the two output lights form interference fringes. The photodetectors 16 and 17 are applied with a reverse bias, and can extract a current according to incident light. The two photodetectors 16 and 17 are arranged so that the interval between the centers is (N / 2 + ／) times (N is an integer) the pitch の of the interference fringe pattern. With this arrangement, the cos (2π (f1-f2) t) of the interference fringe pattern is obtained.
And a signal corresponding to sin (2π (f1−f2) t) are obtained. Therefore, the moving direction of the interference fringe pattern, that is, the magnitude relationship between f1 and f2, can be determined by signal processing, and the rotation direction is detected. it can. The angular velocity of the rotation can be determined from the period of the vibration of the interference fringes. Alternatively, the angular velocity of rotation can be determined from the moving speed Λ · (f1−f2) of the interference fringe pattern.

When the optical gyro rotates clockwise at an angular velocity of 30 degrees per second due to camera shake or a change in the attitude of the automobile, the oscillation frequency f1 of the laser beam becomes 20.
The frequency increased by 0 Hz, and the oscillation frequency of f2 decreased by 200 Hz. The photodetectors 14 and 15 detected a signal of 400 Hz, and obtained a rotation speed and a rotation direction from this.

The photodetectors 14 and 15 may detect a change in impedance by applying a forward bias.

In this embodiment, InGa is used as a semiconductor material.
AsP / InP system was used, but GaAs system, ZnSe
A material that can cause laser oscillation by current injection, such as an InGaN-based material or an InGaN-based material, may be used.

[Second Embodiment] FIGS. 2A and 2B are a plan view and a sectional view, respectively, of an optical gyro according to a second embodiment. Reference numeral 20 denotes an optical gyro element according to the present invention;
1 is a ring resonator type semiconductor laser device, 22 is a multimode interferometer, 23 is a total reflection mirror provided on a waveguide, 24
Is an intersection of waveguides, 25 and 26 are light extraction parts, 27 is an array-shaped photodetector, and a light receiving part is provided above the substrate in contact with the cleavage end face of the substrate of the ring resonator type semiconductor laser device 21. Is fixed. The ring resonator type semiconductor laser device 21 has a clockwise rotation mode indicated by 28 and a counterclockwise rotation mode indicated by 29.

The configuration and operation of the ring resonator type semiconductor laser device are the same as in the first embodiment.

The multimode interferometer 22 splits light at a fixed ratio and extracts it from the ring resonator as follows. In a multimode interferometer in which the element length L and the position of the input port are properly selected, the input to each port is coupled to all output ports. When light is input to a 2 × 2 coupler by an interferometer having a multimode waveguide section having a uniform width, a branching ratio of 1: 1, 0: 1, 15:85, 28:72, etc. can be obtained. It has been known. Further, when a multimode waveguide having a tapered width is connected as shown in FIG.
It is also known that since the branching ratio of the two couplers can be controlled, it is possible to design with the taper width as a parameter. Therefore, the branching ratio can be set so that the insertion loss of the multimode interferometer with respect to the resonator of the ring resonator laser does not increase. For example, the multimode interferometer 22
94% of the incident light 221 enters the ring resonator as output light 222, and 6% is extracted from the ring resonator as output light 223. At this time, similarly, the clockwise light incident on the multi-mode interferometer 22 is 94%
Stay in the ring resonator and 6% is extracted.

The light taken out of the multi-mode interferometer is turned back by the total reflection mirror 23 and guided to the emission section. The light extracted by the multi-mode interferometer from the clockwise rotation mode 28 is emitted from the light extraction unit 25 after turning the optical path back by the total reflection mirror 23. Light extracted from the counterclockwise rotation mode 29 by the multi-mode interferometer passes through the intersection 24 of the waveguide, and is emitted from the light extraction unit 26.

These lights form interference fringes on the end face of the substrate of the optical gyro element. The element spacing of the array-like photodetector 27 is smaller than half the interference fringe pitch determined by the angle of incidence on the light receiving surface and the laser wavelength. The interference fringe is monitored by the photodetector 27, and the output is subjected to signal processing to obtain an interference fringe pattern. The direction and speed of movement of this interference fringe pattern were detected. Thereby, the rotation direction and the angular velocity were obtained.

When the device is made of an AlGaAs material or the like and the oscillation wavelength is a wavelength at which a silicon CCD has sensitivity, the interference fringe pattern may be observed by an inexpensive CCD array device.

[Third Embodiment] FIGS. 3A and 3B are a plan view and a sectional view of an optical gyro according to a third embodiment, respectively. Reference numeral 30 denotes an optical gyro, 31 denotes a ring resonator type semiconductor laser device, and 32 denotes a low refractive index layer / semiconductor layer multilayer mirror. These have the same layer configuration as in the first embodiment. Reference numeral 33 denotes an array-shaped photodetector.

Low-refractive index layer / semiconductor layer multilayer film reflection mirror 3
2 is (λ / (4ne) with respect to the laser oscillation wavelength λ.
ff)) × (2j + 1) (j = 0, 1, 2,...) and (λ / 4n) × (2k + 1) (k = 0,
1, 2,...) Having a low refractive index portion. In order to reduce absorption loss in a semiconductor layer including an active layer of a laser, the thickness of the semiconductor layer is preferably small. Further, in order to suppress the loss due to the spread of light in the low refractive index layer portion having no waveguide structure, it is desired that this layer is also thin.
For example, a structure including a 3λ / 4neff semiconductor layer and a 3λ / 4n low-refractive index layer was manufactured. Si on the semiconductor layer
An N film and a photoresist film are formed, a pattern formed on the photoresist by EB drawing is transferred to a SiN film by dry etching, and a groove reaching the lower clad is formed by reactive ion etching using chlorine gas. Thus, a multilayer mirror was formed.

Low-refractive index layer / semiconductor layer multilayer mirror 3
Two waveguides are connected to 2 at an angle from the vertical. The incident angle with respect to the multilayer mirror is set to a small angle that does not satisfy the condition of total reflection at the interface from the semiconductor layer to the low refractive index layer. When the refractive index of the semiconductor layer is 3.5 and the low refractive index layer is air (refractive index is 1.0), the incident angle of 16.6 degrees or more is the condition of total reflection. The angle of incidence is small. In addition, since a Goos-Henschen shift occurs, two waveguides are arranged in consideration of the shift amount so that the highest reflectance can be obtained between the waveguides.

The transmitted light from the reflection mirror forms an interference fringe having a large period because the difference in the incident angle is small near the photodetector 33.

As in the first and second embodiments, the moving speed and moving direction of the interference fringes were detected by the array-shaped photodetector 33, so that the rotational speed and direction of the element could be known.

[0071]

According to the first embodiment of the present invention described above, an optical gyro capable of detecting the angular velocity and direction of rotation can be obtained.

According to the second embodiment of the present invention, an optical gyro having a low oscillation threshold and a low driving current was obtained.

According to the third embodiment of the present invention, an optical gyro having a low oscillation threshold and a low driving current was obtained.

According to the fourth embodiment of the present invention, an optical gyro having a low oscillation threshold and a low driving current was obtained.

According to the fifth embodiment of the present invention, even if the position of the light receiving element is deviated from the designed observation surface, it is possible to electrically correct the light receiving element, and the allowable range of the element assembly error can be widened. Gyro was obtained.

According to the sixth embodiment of the present invention, an optical gyro having a small number of components and capable of detecting the angular velocity and the rotation direction of the rotation is obtained.

According to the present invention of the seventh and eighth embodiments, an optical gyro capable of detecting the direction of rotation can be obtained from the phase difference between signals at a plurality of light receiving elements.

According to the ninth embodiment of the present invention, the speed and direction of the movement of the interference fringe pattern are detected, and an optical gyro having an angular velocity and a rotation direction is obtained.

According to the tenth embodiment of the present invention, a method for detecting the rotation direction of the optical gyro, which can detect the rotation direction from the phase difference of the signals at the plurality of light receiving elements, is obtained.

According to the eleventh embodiment of the present invention, a method for detecting the rotation direction of the optical gyro that can obtain the angular velocity and the rotation direction by detecting the moving speed and direction of the interference fringe pattern is obtained.

[Brief description of the drawings]

FIG. 1 is a plan view and a sectional view of an optical gyro according to a first embodiment.

FIG. 2 is a plan view and a sectional view of an optical gyro according to a second embodiment.

FIG. 3 is a plan view and a sectional view of an optical gyro according to a third embodiment.

[Explanation of symbols]

 10, 20 Optical gyro element 11, 21, 31 Ring resonator type semiconductor laser element 12 Directional coupler 14, 15, 24, 25 Light extraction section 16, 17, 26, 33 Photodetector 18, 27, 37 Clockwise Circular mode light 19, 26, 36 Circular mode light counterclockwise 22 Multimode interferometer 32 Multi-layer reflective mirror with low refractive index layer / semiconductor layer

Claims (12)

[Claims] A semiconductor ring laser having pumping means, a ring-shaped resonator, and a light extraction part which is a part of the resonator; and an output part for emitting light obtained from the light extraction part to outside the waveguide. An optical gyro comprising: a plurality of light receiving elements disposed at positions where two lights obtained from an output unit overlap. 2. The optical gyro according to claim 1, wherein the light extraction unit is a directional coupler. 3. The optical gyro according to claim 1, wherein the light extraction unit is a multi-mode interferometer. 4. The light-extracting portion is a multilayer reflector comprising a low-refractive-index layer and a semiconductor layer, and the reflector is located at a bent portion of a waveguide of a ring resonator and optically communicates between the waveguides. 2. The optical gyro according to claim 1, wherein the optical gyro is connected to the optical gyro. 5. The optical gyro according to claim 1, wherein the plurality of light receiving elements are a light receiving element group formed in an array. 6. The optical gyro according to claim 1, wherein the plurality of light receiving elements include a CCD array. 7. The optical gyro according to claim 1, wherein a laser element having the same layer configuration as a ring laser is used as the plurality of light receiving elements. 8. The method according to claim 1, wherein a modulation period and a moving direction of an interference fringe pattern formed at a position of the light receiving element are detected based on light intensity signals from the plurality of light receiving elements, and an angular velocity and a rotating direction are obtained from the detected modulation period and moving direction. The optical gyro according to claim 1. 9. The optical gyro according to claim 8, wherein at least two intervals between the plurality of light receiving elements are different from an integral multiple of a pitch of the interference fringe pattern. 10. The method according to claim 1, wherein a speed and a direction of movement of an interference fringe pattern formed at a position of the array element are detected based on a light intensity signal from the array of light receiving element groups, and an angular velocity and a rotation direction are obtained from the detected speed and direction. The optical gyro according to claim 5, wherein 11. A semiconductor ring laser having pumping means, a ring-shaped resonator, and a light extraction part which is a part of the resonator, and an output part for emitting light obtained from the light extraction part to outside the waveguide. A light gyro having a plurality of light receiving elements placed at positions where two lights obtained from the output unit overlap, formed by light intensity signals from the plurality of light receiving elements at a position of the light receiving element A rotation period of the optical gyro, and a rotation direction of the optical gyro obtained by detecting a fluctuation period and a movement direction of the interference fringe pattern. 12. A semiconductor ring laser having pumping means, a ring-shaped resonator, and a light extraction part which is a part of the resonator, and an output part for emitting light obtained from the light extraction part to outside the waveguide. A light gyro having a plurality of light receiving elements placed at positions where two lights obtained from the output unit overlap each other, the light gyro being formed at a position of an array element by a light intensity signal from the plurality of light receiving elements. A rotational speed and direction of the interference fringe pattern, and obtaining an angular velocity and a rotational direction from the detected rotational speed and direction.