JPH06117865A - Optical fiber gyro - Google Patents

Abstract

PURPOSE:To obtain a small-sized optical fiber gyro which can be remarkably improved in angular velocity detecting sensitivity and is small in power consumption. CONSTITUTION:This gyro is constituted by mounting an optical circuit which leads light from a light source 2 to both ends of a sensing coil 5 after dividing the light into two parts and performing mutual phase modulation on the light by means of a phase modulator 7 and receives the divided light rays propagated clockwise and counterclockwise after again synthesizing the light rays and a signal processing circuit which obtains angular velocity information by performing signal-processing on the output of the optical circuit on the same printed wiring board 1. The modulator 7 is constituted by winding an optical fiber band 15 around an electrostriction element 21 and mounted on the board 1 with a semisolid buffer member made of a silicone resin, etc., in between.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber gyro, and more particularly to a phase modulation type optical fiber gyro.

[0002]

2. Description of the Related Art A phase modulation type optical fiber gyro is
It is attracting attention because it has a relatively simple configuration compared to other types of optical fiber gyros. FIG. 6 shows a schematic configuration diagram of a conventional phase modulation type optical fiber gyro. Light source 11
The emitted light is a first optical coupler (for example, a directional coupler having two inputs and two outputs) 12, a polarizer 13, and a second optical coupler 1.
The light passes through 4 and enters both ends of the sensing coil 15 as clockwise light and counterclockwise light. The clockwise light and the counterclockwise light propagating through the sensing coil 15 and emitted are combined by the second coupler 14 and pass through the polarizer 13 to obtain the first optical coupler 1.
The light passes through 2 and is incident on the light receiver 17. The output from the light receiver 17 is guided to the signal processing circuit 18, where the signal is processed and the angular velocity applied to the sensing coil 15 is detected. The analyzer 14 is inserted in the optical path so that the incident light on the sensing coil 15 for propagating the left and right light can be a single polarized wave.

Here, the intensity P of the input light to the light receiver 17 is expressed by P∝coskΩ (1) where k is a constant, where k is the rotational angular velocity of the sensing coil 15.

However, according to the equation (1), the sensitivity is poor in the region where Ω is small, and the direction of the angular velocity cannot be detected. By performing phase modulation with a time lag and synchronously detecting the fundamental wave component of the drive frequency, it becomes P ∝sink Ω (2) to optimize the sensitivity and enable the direction identification of the angular velocity. .

The phase modulator 16 is, as shown in FIG.
Electrostrictive element 21 such as a piezoelectric ceramic formed in a cylindrical shape
An optical fiber 15 is wound around the electrostrictive element 2 via the lead wire 22 for ac voltage (V _pp ) shown in FIG.
As shown in FIG. 12, the electrostrictive element 21 is expanded and contracted in the radial direction (arrow A) by applying the voltage between the inside and the outside of 1. That is, when the electrostrictive element 21 is expanded or contracted, the optical fiber 15 wound around the electrostrictive element 21 is expanded or contracted to change its refractive index, whereby the propagation light in the optical fiber 15 is phase-modulated.

In the conventional phase modulator 16 of this type, as shown in FIGS. 8 and 9, an EP rubber 24 is arranged on a substrate 23 as a cushioning material, and a phase modulator (electrostrictive element 21) is arranged thereon. Place the EP rubber 24 on top of the phase modulator,
A hard upper lid 25 was placed on it, and fixed with a constant tightening force using a torque wrench with a screw or screw 26.

The optical fiber gyro having the above-mentioned structure is mounted in a casing. In the conventional case, however, the optical circuit and the signal processing circuit are separately formed as units 19 and 20 as shown in FIG. It was placed horizontally (a) or vertically (b).

[0008]

The signal for driving the phase modulator 16 in the optical circuit is generated by the internal circuit of the signal processing circuit 18. Therefore, the signal processing circuit 18
And a phase modulator 16 are connected by a lead wire,
The electromagnetic wave radiated from the lead wire 22 is coupled to another element in the signal processing circuit 18, for example, a preamplifier circuit that amplifies the output of the photodetector 17, and becomes noise, which lowers the angular velocity detection sensitivity. In order to avoid this,
It is necessary to make the lead wire 22 as short as possible. However, in the conventional optical fiber gyro, the lead line length inevitably becomes long due to the structure in which the signal processing circuit 18 and the optical circuit are separated as shown in FIG.

Further, since the phase modulator 16 is fixed to the substrate 23 with a screw or a screw 26, the pressing force against the phase modulator 16 changes depending on the tightening torque of the screw and the characteristics of the EP rubber 24. Alternatively, vibration of the electrostrictive element 21 loosens the screw 26 and the like, and it is difficult to obtain a stable modulation degree (ratio of drive voltage and expansion / contraction magnitude). Further, since the electrostrictive element 21 is held under an appropriate pressure so as not to be easily displaced by vibration, it is necessary to apply a drive voltage of 3 to 4 V or more in order to expand and contract the electrostrictive element 21 to a required size. there were. In order to reduce the driving voltage to reduce the power consumption, the length of the optical fiber wound around the electrostrictive element 21 must be increased, which increases the material cost.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide a small-sized and low-power-consumption optical fiber gyro which can greatly improve the angular velocity detection sensitivity.

[0011]

In order to achieve the above object, an optical fiber gyroscope of the present invention splits light from a light source into two parts, phase-modulates them, and guides them to both ends of the sensing coil. The same printed wiring board with an optical circuit that combines the light that propagates clockwise and the light that propagates counterclockwise to receive light and the signal processing circuit that processes the output from the optical circuit to obtain angular velocity information. It is configured to be mounted on top.

In the optical fiber gyro of the present invention,
A phase modulator formed by winding an optical fiber around an electrostrictive element is preferably mounted on a printed wiring board via a semi-solid buffer material such as silicone resin. As the cushioning material, silicone resin, silicone gel, or the like can be used.

[0013]

According to the above technical means, by mounting both the electronic component forming the signal processing circuit and the optical component forming the optical circuit on one printed wiring board, the phase modulator in the optical circuit and the phase modulator in the optical circuit are mounted. Since the length of the lead wire connecting the internal circuit of the signal processing circuit that generates the driving signal can be minimized, the emission of electromagnetic waves from the lead wire that causes noise can be suppressed and the angular velocity can be reduced. It can be detected with high sensitivity. Further, by integrating the signal processing circuit and the optical circuit, it is possible to reduce the size and weight of the optical fiber gyro and improve the productivity.

[0014]

Next, an optical fiber gyro of the present invention will be described.

As shown in FIG. 1, the optical fiber gyroscope of the present invention comprises an optical circuit comprising a light source 2, optical couplers 3, 4, a sensing coil 5, an optical fiber polarizer 6, a phase modulator 7 and a light receiver 8. It is configured by mounting a signal processing circuit including various electronic components on a common printed wiring board 1.

As the material of the printed wiring board 1, in addition to glass epoxy, polyimide, paper phenol, the surface of ceramic or iron and the through hole are covered with an insulating layer, and a conductor pattern of copper or gold is formed thereon. A so-called metal substrate is applied.

As the resin for the cushioning material, silicone resin, silicone gel, RTV rubber, plastic, acrylic, epoxy, etc. are applied.

The sensing coil 5 is not wound around a bobbin, but an optical fiber coil in a so-called bundled state without bobbin is fixed to the printed wiring board 1 with silicone resin. This is a structure adopted for the purpose of downsizing and weight reduction, and there is no particular problem in terms of performance even with a normal sensing coil with a bobbin. The optical fiber polarizer 6 is provided by being wound around the outside of the sensing coil 5.
The shaded areas 9 and 10 on the printed wiring board 1 are the electronic component mounting areas of the signal processing circuit. The mounting areas of various optical components such as the electronic component mounting areas 9 and 10 and the light source 2 and the optical couplers 3 and 4 that constitute the optical circuit are appropriately determined. The phase modulator 7 is configured by winding the optical fiber 15 of the sensing coil 5 around a cylindrical electrostrictive element 21 and applying a drive voltage to the inside and outside of the electrostrictive element 21. The lead wire 13 is connected to an electronic circuit for generating a drive signal, which is provided at a position closest to the phase modulator 7 in the electronic component mounting area 9. In this way, the signal processing circuit and the optical circuit are combined into one printed wiring board 1
Since the lead wire 13 can be remarkably shortened in length as compared with the conventional optical fiber gyro, the emission of electromagnetic waves from the lead wire 13 which causes sneak noise is suppressed. The detection sensitivity of the angular velocity can be improved.

FIG. 2 shows how the phase modulator 7 is attached to the printed wiring board 1. In the figure, an annular member 14 provided on the printed wiring board 1 is a buffer material holding member for holding the semi-solid buffer material 29 on the printed wiring board 1. In the phase modulator 7, after the silicone resin is injected into the cushioning material holding member 14, the lower portion of the electrostrictive element 21 is inserted into the cushioning material holding member 14 before the silicone resin is hardened. After the electrostrictive element 21 is floated, the resin is waited for curing, and is finally held gently on the printed wiring board 1 by the semi-solid silicone resin. Since the electrostrictive element 21 does not come into direct contact with the printed wiring board 1 but is gently held by the semi-solid buffer material 29 made of silicone resin, the mechanical vibration of the phase modulator 7 is prevented from occurring. It is possible to prevent the electronic component soldered to the solder from being detached from the substrate 1 and reduce the so-called acoustic load that suppresses the vibration of the phase modulator 7. Since there is no adjustment work and workability is good, economic efficiency is improved.

As a result of making a prototype of the optical fiber gyroscope of this embodiment, the wraparound noise of the phase modulator drive signal to the angular velocity output is eliminated, and the angular velocity detection sensitivity is more than doubled as compared with the conventional one.

Next, the phase modulator 7 will be described with reference to FIGS.
Another implementation example of will be described.

In FIG. 3, a hard core 30 is fixedly mounted on the printed wiring board 1, and the electrostrictive element 21 of the phase modulator 7 is coaxially loosely fitted to the core 30. The core 30 is the substrate 1
It is fixed to the substrate with screws or the like, or is integrated with the substrate 1 by adhesion or the like. A soft resin is injected into the gap between the phase modulator 7 and the core 30 and hardened to hold the phase modulator 7 gently. In the case of fixing with a resin, the degree of freedom of the phase modulator 7 increases, and vibration (including resonance) of the resin itself may occur. However, placing a hard core 30 in the center of the resin prevents vibration. To do. By integrally forming the substrate 1 and the core 30, the number of parts can be extremely reduced.

In FIG. 4, an annular protrusion 31 for preventing the buffer material 29 from flowing out is formed on the printed wiring board 1, and a columnar protrusion 32 is formed at the center thereof. The phase modulator 7 is installed after injecting a resin serving as the buffer material 29 between the annular protrusion 31 and the columnar protrusion 32, and is gently held.

In FIG. 5, the phase modulator 7 is installed in the annular protrusion 31 on the printed wiring board 1 and then the cushioning material 29 is applied to the entire surface thereof. Also in this case, the electrostrictive element 1
1 is gently held by the cushioning material 29 accumulated in the lower part. If a corrosion preventive material for the phase modulator 7 is used for the buffer material 29, the electrodes of the phase modulator 7 are prevented from being corroded and the life of the device is extended.

[0025]

In summary, according to the present invention, the following effects can be exhibited.

1) By mounting both the electronic components forming the signal processing circuit and the optical components forming the optical circuit on one printed wiring board, a phase modulator in the optical circuit and a signal for driving the phase modulator are provided. Since the length of the lead wire connecting to the internal circuit of the signal processing circuit that is generated can be made as short as possible, it is necessary to suppress the emission of electromagnetic waves from the lead wire that causes noise and detect angular velocity with high sensitivity. You can

2) By mounting the phase modulator on the printed wiring board via a semi-solid buffer material such as silicone resin, the phase modulator is held gently, and its mechanical vibration causes the printed wiring to move. It can be prevented from being transmitted to the substrate.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of an optical fiber gyro of the present invention.

FIG. 2 is a partially cutaway perspective view showing a main part (phase modulator mounting part) of FIG.

FIG. 3 is a side sectional view showing another mounting example of the phase modulator.

FIG. 4 is a side sectional view showing another implementation example of the phase modulator.

FIG. 5 is a side sectional view showing another mounting example of the phase modulator.

FIG. 6 is a schematic configuration diagram showing a conventional optical fiber gyro.

FIG. 7 is a conceptual diagram showing an arrangement of an optical circuit and a signal processing circuit in a conventional optical fiber gyro.

FIG. 8 is a plan view showing a mounting state of a conventional phase modulator.

9 is a vertical cross-sectional view of FIG.

FIG. 10 is a diagram showing a phase modulator.

FIG. 11 is a diagram showing an example of a drive voltage of a phase modulator.

FIG. 12 is a diagram showing expansion / contraction operation of the phase modulator.

[Explanation of symbols]

 1 Printed Circuit Board 2 Light Source 5 Sensing Coil 7 Phase Modulator 9 Electronic Component Mounting Area 10 Electronic Component Mounting Area 15 Optical Fiber 21 Electrostrictive Element 29 Buffer Material

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Norihiro Ashizuka 5-1-1 Hidakacho, Hitachi City, Ibaraki Prefecture Hitachi Cable Co., Ltd. Hidaka Plant (72) Inventor Michiya Ishikawa Hidaka, Hitachi City, Ibaraki Prefecture 5-1-1, Machi, Hitachi Cable Co., Ltd. Hidaka Plant (72) Inventor Junpei Miyazaki 5-1-1, Hidaka Town, Hitachi City, Ibaraki Hitachi Cable Co., Ltd. Hidaka Plant (72) Inventor Mitsu Sudo Taka 5-1-1, Hidaka-cho, Hitachi-shi, Ibaraki Hitachi Cable Co., Ltd. Hidaka factory

Claims (2)

[Claims] 1. The light from the light source is branched into two and then phase-modulated by a phase modulator and guided to both ends of the sensing coil.
An optical circuit that receives the combined branched light propagating clockwise and the branched light propagating counterclockwise through the sensing coil, and a signal processing circuit that processes the output from the optical circuit to obtain angular velocity information. An optical fiber gyro characterized in that and are mounted on one printed wiring board. 2. The phase modulator is formed by winding an optical fiber around an electrostrictive element, and is mounted on the printed wiring board via a semi-solid buffer material. Fiber optic gyro.