JP2511346B2 - Ring resonance type gyro - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ring resonance type gyro, in which the entire apparatus is miniaturized and stabilized.

[0002]

2. Description of the Related Art As an optical gyro system, three systems of a laser gyro, an optical fiber gyro and a ring resonance type gyro have been proposed. The ring resonance type gyro has an advantage that the optical fiber length can be shorter than that of the optical fiber gyro. The basic configuration and operation of the conventional ring resonance type gyro will be briefly described with reference to FIG. For example, the light from the light source 10 formed of a semiconductor laser is branched into the optical fibers 13 and 14 by the optical coupler 16, passes through the optical couplers 17 and 18, respectively, and then is introduced into the optical fiber loop 15 by the optical coupler 19. , Light in the clockwise direction (CW) and light in the counterclockwise direction (CCW).

CW light undergoes multiple interference in the loop 15, and the leaked light is an optical coupler 19-optical fiber 13-optical coupler 17.
Is input to the detector 12 via. Similarly, the CCW light also undergoes multiple interference in the loop 15, and the leaked light is the optical coupler 19
-Optical fiber 14-detector 11 via optical coupler 18
Is input to The optical fiber loop 15 has a resonance frequency determined by the loop length and the wavelength of the light obtained from the light source 10, and the light is confined in the optical fiber loop 15 in the resonance state. When no rotation is applied to such a gyro, both the CW light and the CCW light have the same resonance frequency, but when the rotation angular velocity is applied, the CW light is affected by the Sagnac effect
The resonance frequency differs between light and CCW light. By detecting this difference (deviation), the rotational angular velocity can be known.

In the configuration shown in FIG. 2, the intensity of the leaked light of the CW light is detected by the detector 12, the detection output is fed back to the light source 10, and the light is emitted from the light source 10 according to the intensity of the leaked light. The frequency of the light is controlled, and the CW light is kept in the optical fiber loop 15 so that it is always in a resonance state. Therefore, this example shows the case where the CW light is used for correcting the disturbance such as temperature.

On the other hand, the intensity of leaked CCW light is detected by the detector 11
The detected output is fed back to the frequency shifter 20, and the frequency shifter 20 is detected according to the intensity of leaked light.
The frequency of the light passing therethrough is shifted, and the CCW light is also kept in a resonant state in the optical fiber loop 15. The rotational angular velocity applied to the gyro is calculated from the frequency shift amount with respect to the frequency shifter 20.

[0006]

In this conventional gyro, since the optical fiber is used as the loop 15, there is a problem that it is vulnerable to disturbances such as vibrations. The production technique is required, and the frequency shifter 20 has to be mounted in the optical fiber, and the mounting work and the optical adjustment are troublesome. Therefore, an acousto-optic modulator (AOM) as the frequency shifter 20 is required. It is expensive. Further, in the conventional example of the ring resonance type gyro, the optical fiber 1 forming the loop is
3 and the optical fiber 14 and the optical fiber loop 15 are arranged on the same plane as shown in the drawing, and are optically coupled to each other through the optical coupler 19, so that the gyro shown in FIG.
Is the diameter of the loop forming the optical fibers 13 and 14 and the optical fiber loop 1
The size is the sum of 5 diameters. The configuration in which the optical fibers 13 and 14 and the optical fiber loop 15 are arranged in series in the horizontal direction in this manner is inconvenient for downsizing the ring resonance gyro. The present invention provides a ring resonance type gyro that solves the above-mentioned problems in reducing the size and cost of the ring resonance type gyro.

[0007]

[Means for Solving the Problems] A first waveguide 1 and a Y-shaped branching portion 5 which divides light sent from the first waveguide 1 into two parts.
Of the second waveguide 2 and the third waveguide 3 that are branched into two Y-shapes from the first waveguide 1 in the Y-shaped branch portion 5, and the second waveguide 2 and the third waveguide 3 that are branched into two. A ring waveguide 4 which is disposed between the ring waveguide 4 and the second waveguide 2 is optically coupled to the second waveguide 2 via the optical coupling portion 6 and to the third waveguide 3 via the optical coupling portion 7.
And are integrally formed on a common substrate 9 having an electro-optical effect,
A ring resonance type gyro in which a modulation electrode 8 is attached to a portion between the Y-shaped branch portion 5 of the second waveguide 2 or the third waveguide 3 and the optical coupling portion 6 or the optical coupling portion 7. Configured.

[0008]

The first waveguide 1, the second waveguide 2, the third waveguide 3, and the ring waveguide 4 are formed by being integrated on a common substrate 9 having an electro-optical effect, and the optical coupling portion 6, 6. 7 is formed and, of course, the same rotational angular velocity detecting operation as in the conventional case is performed, but since it is integrated on the substrate 9, it is possible to reduce the size and cost and to stabilize it.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of a ring resonance type gyro according to the present invention will be described with reference to FIG. In the present invention, an electro-optical material such as lithium niobate or lithium tantalate is used as the substrate 9, and the conventional optical fibers 13 and 14, the optical fiber loop 15 and the optical couplers 16 and 17 shown in FIG. It is formed by directly accumulating portions having the same function as 18, 19.

That is, the first waveguide 1 of the substrate 9 shown in FIG.
The portions corresponding to the second waveguide 2, the third waveguide 3, and the ring waveguide 4 are formed to have a higher refractive index than other portions. In order to form a part (waveguide) of the substrate 9 with a high refractive index,
The well-known titanium diffusion method or proton conversion method is used. As a result, the diffused portion of the substrate 9 becomes the respective waveguides 1, 2, 3, 4. The optical coupling portions 6 and 7 can be integrated and formed on the substrate 9 by a similar method, and can function as a conventional directional coupler.

The branch portion 5 may be formed by simply forming the second waveguide 3 and the third waveguide 3 in the Y-shape with respect to the first waveguide 1. The first waveguide 1 shown in FIG. 1 is formed to have a relatively short length from the left edge (in the drawing) of the substrate 9 toward the right edge, and the left edge is optically connected to the light source 10, and the second and third waveguides are provided. The waveguides 2 and 3 are formed symmetrically with respect to the extension direction of the first waveguide 1, and their right end portions reach the right end edge of the substrate 9 and are optically coupled to the detectors 11 and 12. .

A pair of modulation electrodes 8 are provided so as to sandwich the second waveguide 2 between the branch portion 5 and the optical coupling portion 6 so as to sandwich it.
Are mounted on the substrate 9. Since lithium niobate has an electro-optical effect, if an electric field is applied between the pair of electrodes 8, the refractive index of the waveguide of the light sandwiched between the electrodes 8 will be increased according to the strength of the electric field. In other words, the phase of light in the waveguide can be changed, that is, the frequency of light can be changed by changing the phase linearly with respect to time (serodyne modulation method). Therefore, the modulation electrode 8 can function as a frequency shifter.

The operation of this gyro will be described. The light source 1
The light emitted from 0 is introduced into the first waveguide 1 and is split into two at the branch portion 5. One of the two split lights passes through the second waveguide 2 and enters the ring waveguide 4 at the optical coupling portion 6 to become CW light. The other light split into two at the branching portion 5 passes through the third waveguide 3 and enters the ring waveguide 4 at the optical coupling portion 7 to become CCW light. The CW light undergoes multiple interference in the ring waveguide 4, and the intensity of the leaked light is detected by the detector 11. Similarly, the CCW light also undergoes multiple interference in the ring waveguide 4, and the intensity of the leaked light is detected by the detector 12.

CW light and CCW light also have a resonance frequency determined by the wavelength of the light from the light source 10 and the loop length of the ring waveguide 4, and when the rotational angular velocity is not applied to the gyro in the resonance state, these resonances occur. The frequencies are the same and are confined in the ring waveguide 4. When the rotational angular velocity is applied to the gyro, these resonance frequencies shift from each other due to the Sagnac effect. Therefore, the rotational angular velocity can be calculated by detecting this shift. Since the means for calculating the frequency shift is well known in the art, its explanation is omitted. In this example, the CCW light is used for disturbance correction such as temperature change (the same use as the CW light described in FIG. 2), and the CW light is used for measurement.

The light source 10 and the detectors 11 and 12 may be directly attached to the substrate 9 or may be attached via an optical fiber. In the above description, the modulation electrode 8
Is opposed to the second waveguide 2, but may be opposed to the third waveguide 3. In this case, the output of the detector 12 controls the strength of the electric field of the modulation electrode 8, and the output of the detector 11 controls the frequency of the light from the light source 10.

[0016]

As described above, the ring resonance type gyro of the present invention is formed by integrating each waveguide, the optical coupling section and the Y-shaped branch section on one substrate. It is possible to reduce the size of the entire ring resonance type gyro, reduce the cost, and stabilize the system against disturbance. That is, the configuration of the Y-shaped branch portion that transmits and receives light to and from the ring waveguide 4 and the second and third waveguides that branch in the Y-shape is the same as the first waveguide 1 and the second waveguide. It is only necessary to form the third waveguide in a Y shape, which is extremely easy and easy as compared with the conventional example in which these waveguides are formed in a ring shape. Since the first waveguide 1 can be made relatively short, it can be said that this configuration is suitable for downsizing the entire ring resonance type gyro and reducing the manufacturing cost. In addition, the ring waveguide 4
Is disposed between the second waveguide 2 and the third waveguide 3 which are branched into two, and is optically coupled to the second waveguide 2 through the optical coupling portion 6 and the third waveguide through the optical coupling portion 7. Since there are two optical coupling portions for optically coupling to the optical waveguide 3, the ring waveguide 4 is housed in a region originally required for the second waveguide 3 and the third waveguide 3, and accordingly, The lateral dimension of the entire ring resonance type gyro, particularly in the drawing, is further reduced. Moreover, since the waveguide and other parts are integrated and formed on the substrate, a gyro that is stable against disturbance can be formed.

[Brief description of drawings]

FIG. 1 is a plan view showing an example of a ring resonance type gyro according to the present invention.

FIG. 2 is a plan view showing an example of a conventional ring resonance type gyro.

Claims (1)

(57) [Claims] 1. A first waveguide, a Y-shaped branching portion that divides light sent from the first waveguide into two parts, and a second branching into two Y-shaped portions from the first waveguide at the Y-shaped branching portion. The third waveguide is disposed between the waveguide and the third waveguide, and the second waveguide and the third waveguide that are branched into two, and is optically coupled to the second waveguide through the optical coupling section and the third coupling is performed through the optical coupling section. A ring waveguide optically coupled to the waveguide is integrally formed on a common substrate having an electro-optical effect, and is formed in a portion between the Y-shaped branch portion of the second waveguide or the third waveguide and the optical coupling portion. A ring resonance type gyro characterized in that a modulation electrode is attached thereto.