JPH06160103A - Optical gyroscope device - Google Patents

Abstract

PURPOSE:To expedite the simplifying and downsizing of whole structure in an optical gyroscope device of a passive type ring resonance system. CONSTITUTION:A laser diode 25 and photodiodes 26, 27 are mounted on a substrate 19, and rectilinear waveguides 19a to 19g of a thin film optical waveguide material are formed on a surface of the substrate 19. An optical fiber 28 is connected to the waveguides 19f, 19g and this optical fiber 28 is also connected to an optical fiber 18a of a resonance loop 18 with a coupler 29. The substrate 19 is equipped inside of the resonance loop 18 and a whole body thereof is reduced in dimensions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical gyro device used for, for example, an orientation sensor or attitude control, and more particularly to a passive ring resonance type optical gyro device using a resonance loop.

[0002]

2. Description of the Related Art An example of an optical fiber resonator used in a conventional passive ring resonance type gyro device is shown in FIG. The optical fiber resonator shown in the figure has a resonance loop 1 in which an optical fiber 1a is formed in a ring shape, and the resonance loop 1
And a light transmission / reception path 2 configured by combining an optical fiber or the like for entering a laser beam. Further, a part of the resonance loop 1 is provided with a phase modulator 3 having a structure in which a part of the optical fiber 1a is wound around a cylindrical piezoelectric element 3a.

The transmission / reception path 2 has an optical fiber 4a, one end of which is optically connected to a laser light source 4 composed of a laser diode, a coupler 5 connected to the other end of the optical fiber 4a, and this coupler. 5, an optical fiber 6 formed in a ring shape passing through 5, and optical fibers 6a, 6a whose one ends are optically connected to a part of the optical fiber 6 via couplers 7, 7, respectively. , The other end of each optical fiber 6a, 6a has a photodiode 8,
Amplifiers 11 and 11 for amplifying the detected signal are connected to the photodiodes 8 and 8, respectively. Further, the optical fiber 6 and the optical fiber 1 a forming the resonance loop 1 are optically connected via a coupler 9.

In the optical fiber resonator having the above-described structure, the laser light emitted from the laser light source 4 enters the optical fiber 1a via the optical fiber 6 as clockwise light and counterclockwise light. When the resonance loop 1 rotates with respect to the inertial space, a phase difference occurs between the clockwise light and the counterclockwise light,
Thereby, the rotation direction and the angular velocity are detected. Also,
In this method, unlike the conventional interference type optical gyro device,
Since the resonance phenomenon of light in the resonance loop 1 is used, there is an advantage that the length of the resonance loop 1 can be short.

[0005]

However, in the above-mentioned conventional structure, since the optical fiber is used as a whole, there is a limit to downsizing, and the optical structure of the laser light source and the optical fiber is limited. Even if the connection or the use of the coupler is used, the processing of the branched portions of the optical fibers is complicated, and further, the processing accuracy is lowered, and each problem remains unsolved.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an optical gyro device which can be made smaller and thinner and can be easily assembled.

[0007]

An optical gyro device according to the present invention comprises a resonance loop composed of a ring-shaped optical fiber,
A laser light source, a light transmission path for supplying the laser light emitted from the laser light source as right-handed light and left-handed light to the resonance loop, and a return light path for guiding the respective laser lights that have turned around the resonance loop. And a light receiving portion for receiving the respective laser light returned in the return light path, the light sending path and the return light path are formed by a thin film optical waveguide formed on the substrate, Further, the laser light source and the light receiving portion are mounted on the substrate.

Further, it is preferable that each part of the thin film optical waveguide is formed in a linear shape.

[0009]

In the above means, the light-transmitting and return-light paths that give the clockwise light and the counterclockwise light to the resonance loop constituted by the optical fiber and guide the return light from the resonance loop are formed on the substrate. It is composed of an optical waveguide, and a laser light source and a light receiving portion are arranged on the substrate. Therefore, for example, by arranging the substrate in the resonance loop, the entire size can be reduced. Further, since the thin film optical waveguide, the laser light source and the light receiving portion are mounted on the substrate and can be handled as one unit, the assembling work is also simplified.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1A is an enlarged plan view showing the structure of a resonator used in an optical fiber device according to the present invention, FIG. 1B is a sectional view showing a part of a substrate, and FIG. 2 is an overall configuration of an optical gyro device. It is a block diagram showing. The optical gyro device shown in FIG. 2 includes an optical fiber resonator 35 whose details will be described later, a lock-in amplifier 13 to which the detection output of the clockwise light of the resonance loop 18 in the optical fiber resonator 35 is input, and a resonance loop. The lock-in amplifier 12 to which the detection output of the counterclockwise light of 18 is input, and the phase modulator 2 that controls the resonance loop length so that the operating point of the light circulating in the resonance loop 18 coincides with the resonance point.
0, a phase controller 14 for controlling the phase modulator 20, an oscillator 15, an adder 16, and an amplification amplifier 17 are provided.

The inside of the optical fiber resonator 35 is provided with a resonance loop 18 in which an optical fiber 18a is formed in a ring shape, and a thin film optical waveguide substrate 19 which serves as a light transmitting / receiving path for the resonance loop 18. In addition, the phase modulator 20
Is constructed by winding an optical fiber 18a constituting the resonance loop 18 around a cylindrical piezoelectric element 20a. Figure 1
As shown in (A), the thin-film optical waveguide substrate 19 is provided with a laser diode 25 as a laser light source and a light-receiving unit 22 for detecting light emission intensity of the laser diode 25. The substrate 19 is also provided. The surface of the waveguide 19c for guiding the laser light from the laser diode 25
And a waveguide 19a for transmitting light, which is branched from the waveguide 19c and supplies clockwise light and counterclockwise light to the resonance loop 18,
19b is formed. Further, on the surface of the substrate 19, waveguides 19d and 19e for light reception, which are integrated with the waveguides 19a and 19b for transmitting light, are formed.
Photodiodes 26 and 27 for receiving the return light from the respective waveguides 19d and 19e are provided. At the right end of the substrate 19 in the figure, waveguides 19f and 19g are formed at which the waveguides 19a and 19b and 19d and 19e join.

The waveguides 19a to 19g are thin film optical waveguides formed on the surface of the substrate 19, the laser diode 25 is optically connected to the waveguide 19c, and the photodiodes 26 and 27 are the waveguides 19d and 19d. It is optically connected to 19e. Each of the waveguides 19a to 19
g is formed by, for example, a spin coating method. In this spin coating method, the laser diode 25 and the photodiodes 26 and 27 are previously fixed to the surface of the substrate 19 by means such as adhesion, and a fluid optical waveguide material is supplied to the surface of the substrate 19 to form a disc. The substrate 19 is placed on top and rotated. As shown in FIG. 1A, the optical waveguide material extends into a thin film due to centrifugal force and is cured. At this time, the laser diode 25 and the photodiodes 26 and 27
Are encapsulated by the optical waveguide material. Next, the waveguide material other than the waveguides 19a to 19g is removed by etching to form a thin film optical waveguide as shown in FIG.

As shown in FIG. 1B, the photodiode 27 is optically connected so as to be surrounded by the waveguide 19d, and similarly, the laser diode 25 and the waveguide 19c and the photodiode 27 and the waveguide 19e are similarly provided. And are optically connected. In addition, each of the waveguides 19a to 19
All g are formed in a linear shape, and the loss of light traveling in the waveguide is minimized. In the thin film optical waveguide substrate 19 shown in FIG. 1, the light-transmitting waveguides 19a and 19b and the light-receiving waveguides 19d and 19e are integrally connected as a branch route at the J portion. The waveguide 19a,
A coupler may be provided for coupling the waveguide b and the waveguides 19d and 19e. In addition, the waveguide 19f on the substrate 19,
An optical fiber 28 for connection is connected to the right end portion of 19g in the figure via couplers 24, 24, and this optical fiber 28 and the optical fiber 18a of the resonance loop 18 are connected via a coupler 29.

Next, the operation of the optical gyro device will be described. The laser light emitted from the laser diode 25 is branched by the waveguides 19a and 19b for transmitting light,
The light is given as right-handed light and left-handed light into the optical fiber 18a forming the resonance loop 18 via the waveguides 19f and 19g and the connecting optical fiber 28. The clockwise light of the resonance loop 18 is connected to the connecting optical fiber 28 and the waveguide 19.
From f to the photodiode 2 via the light receiving waveguide 19d
It is received by 7. This light reception output is the lock-in amplifier 13
Given to. In the lock-in amplifier 13, the oscillator 15
Lock-in amplifier 1
The output from 3 goes through the phase controller 14 and the oscillator 1
It is added to the oscillation frequency of 5 and given to the phase modulator 20. The loop length is adjusted by the phase modulator 20, and the operating point of the clockwise light in the resonance loop 18 is fixed so as to match the resonance point of the resonance loop 18.

When the optical gyro device rotates with respect to space, the operating point of counterclockwise light of the resonance loop 18 deviates from the resonance point due to the Sagnac effect. This counterclockwise light is guided from the optical fiber 28 and the waveguide 19g to the light receiving waveguide 19e.
After being received by the photodiode 26, the light is output, and the light reception output is given to the lock-in amplifier 12. In this lock-in amplifier, from the light reception output from the photodiode 26 and the oscillation frequency from the oscillator 15, resonance occurs with the operating point. An angular frequency component corresponding to the deviation from the point is detected. The rotation direction is obtained from the phase difference of the angular frequencies, and the rotation angular velocity is obtained from the amplitude.

As described above in detail, in this embodiment, the substrate 19 on which the laser diode 25 and the photodiodes 26 and 27 are mounted and the waveguides 19a to 19g are formed.
By using, it is not necessary to connect the laser diode 25 and the like to the optical fiber as in the prior art, so that the optical coupling efficiency can be improved and the assembling work can be easily performed. Further, since the above-mentioned substrate 19 has the optical waveguide formed by the spin coating method and each waveguide is optically connected to the laser diode and the photodiode, it can be formed extremely small and thin as a whole. In addition, the substrate 19 is connected to the resonance loop 1
By providing the optical gyro device 8 inside, the entire optical gyro device can be downsized.

In the above embodiment, the optical fiber 28 is connected to one end of each of the optical waveguides 19f and 19g formed on the substrate 19, and the optical fiber 18a forming the resonance loop 18 together with the optical fiber 28. Although and are optically connected by the coupler 29, as shown in FIG.
The optical fiber 28 may be eliminated. In the substrate 30 shown in FIG. 3, a waveguide 19h in which the waveguides 19a and 19b and the waveguides 19d and 19e merge is formed into a U-shaped thin film, and the waveguide 19h and the optical fiber 18a of the resonance loop 18 are formed. Is coupled at point K. The point K may be coated with a material having a refractive index different from those of the waveguide 19h and the optical fiber 18a. In this embodiment, all parts except the resonance loop 18 are formed by the waveguides on the substrate 30, so that the number of parts can be reduced and the size can be reduced.

In each of the above embodiments, the resonance loop 18
Is provided with a phase modulator 20, and the received light of the clockwise light of the resonance loop 18 is given to the phase controller 14 to control the phase modulator 20 so that the operating point of the clockwise light coincides with the resonance point. It has become. However, in the present invention, the clockwise light is applied to the frequency controller, and the laser diode 25 is modulated at the oscillation frequency based on this.
Thereby, the operating point of the clockwise light may be controlled so as to coincide with the resonance point.

[0019]

According to the first aspect of the present invention, there is provided a substrate having a laser light source, a light receiving element, an optical waveguide extending from the laser light source to a resonance loop, and an optical waveguide extending from the resonance loop to the light receiving element. By providing the device, it is possible to reduce the size and thickness of the device and to easily assemble the device.

According to the invention described in claim 2, in addition to the effect of the invention described in claim 1, the output loss in the optical waveguide can be reduced.

[Brief description of drawings]

1A is an enlarged plan view showing a structure of a resonator of an optical gyro device as an embodiment of the present invention, and FIG. 1B is a partial cross-sectional view of a substrate.

FIG. 2 is a block diagram showing the overall structure of an optical gyro device.

FIG. 3 is an enlarged view showing a resonator of another embodiment.

FIG. 4 is a block diagram showing a configuration of a conventional optical gyro device.

[Explanation of symbols]

 12, 13 Lock-in amplifier 14 Phase controller 15 Oscillator 16 Adder 17 Amplifier 18 Resonance loop 18a Optical fiber 19,30 Substrate 19a to 19h Waveguide 20 Phase modulator 25 Laser diode 26, 27 Photodiode

Claims (2)

[Claims] 1. A resonance loop formed of a ring-shaped optical fiber, a laser light source, and a light transmission path for supplying laser light emitted from the laser light source to the resonance loop as clockwise light and counterclockwise light. A return light path for guiding the respective laser light that has passed through the resonance loop and a light receiving portion for receiving the respective laser light returned by the return light path are provided, and the light sending path and the return light path are provided. Is formed by a thin film optical waveguide formed on a substrate, and a laser light source and a light receiving unit are mounted on the substrate. 2. The optical gyro device according to claim 1, wherein each part of the thin film optical waveguide is linearly formed.