JPH0686022U - Fiber optic gyro - Google Patents

Abstract

(57) [Abstract] [Purpose] It is easy to attach the piezoelectric vibrator that constitutes the phase modulator of the optical fiber gyro to improve the assembly workability, and the piezoelectric vibrator is held with an appropriate elastic force to improve the detection sensitivity. Increase. [Structure] The piezoelectric vibrator 8 of the phase modulator is elastically held by a resin 11 so as to float above a member 10 to which the piezoelectric vibrator 8 is attached. The detection sensitivity is optimized by selecting the elastic coefficient of the resin 11 to be 1 kg / mm ² or less.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an optical fiber gyro, and more particularly to a phase modulation type optical fiber gyro.

[0002]

[Prior art]

 A sensor that detects angular velocity and angle by simply attaching it to a moving body without any external information and controls its posture and position is generally called a gyro. An optical fiber gyro is a gyro that detects the speed and angle of rotation by using the Sagnac effect by using an optical fiber in the light propagation path. The optical fiber gyro has recently been used in the industrial field because it has the following features. (1) Simple structure with no moving parts. (2) Startup time is short. (3) Compact and lightweight. (4) Low power consumption. (5) Wide dynamic range. (6) Suitable for mass production and cost reduction.

FIG. 1 shows a configuration diagram of a typical optical fiber gyro. This optical fiber gyro is composed of a light source 1, a light receiver 2, an optical fiber coil 3, a phase modulator 4, directional couplers 5a and 5b, a polarizer 6 and a circuit board 7 on which a signal processing circuit is mounted. The light emitted from the light source 1 passes through the directional coupler 5a, then the polarization noise is removed by the polarizer 6, and then is branched into two optical paths by the directional coupler 5b. Propagated as circular light and counterclockwise light. The optical fiber coil 3 is formed by winding an optical fiber in a coil shape, and functions as a rotation angular velocity sensor of the optical fiber gyro. When the optical fiber coil 3 rotates, a phase difference occurs between the clockwise light and the counterclockwise light, and the rotation or the like can be detected by detecting this. The phase modulator 4 is for providing a phase bias of π / 2 between the clockwise light and the counterclockwise light, and the sensitivity is optimized by this. The clockwise light and the counterclockwise light that have propagated through the optical fiber coil 3 merge at the directional coupler 5b, and become a coherent light due to the phase difference between the two. The light passes through the coupler 5a and enters the light receiver 2. The intensity of the interference light is measured by the light receiver 2, and this is sent to a signal processing circuit on the circuit board 7 and converted into a rotation amount.

[0004]

[Problems to be solved by the device]

 By the way, the phase modulator is constructed by winding an optical fiber around a cylindrical piezoelectric vibrator (PZT: lead zirconate titanate). Conventionally, this phase modulator is attached to an optical fiber gyro board by attaching a piezoelectric vibrator 14 around which an optical fiber 13 is wound as shown in FIG. 5 to two pressing plates 16, 17 via a urethane rubber cushion material 15. It was clamped with and fastened with a set screw 18, and this was separately screwed to the substrate 19 of the gyro. However, since the vibration state of the piezoelectric vibrator 14 changes depending on the tightening force, it is necessary to strictly adjust the tightening torque of the setscrew 18 in the conventional mounting structure, which is a poor assembly workability and a large cost problem. Was becoming.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to provide a novel optical fiber gyro that has low cost, mass productivity, and good detection sensitivity.

[0006]

[Means for Solving the Problems]

In order to achieve the above-mentioned object, the optical fiber gyro of the present invention is characterized in that the piezoelectric vibrator of the phase modulator is elastically held by a resin so as to be floated from the member to which it is attached. The elastic modulus of the above resin is preferably 1 kg / mm ² or less.

[0007]

[Action]

 According to the above technical means, the piezoelectric vibrator does not come into direct contact with the mounting member and is gently held by the resin, so that there is no need for the conventional work of adjusting the tightening force by screwing.

FIG. 4 shows the relationship between the modulation voltage of the piezoelectric vibrator and the elastic coefficient of the resin when the phase modulator is held by the resin having various elastic coefficients. Here, the modulation voltage indicates the minimum voltage at which a predetermined modulation signal capable of detecting the signal of the optical fiber gyro can be obtained. The modulation voltage increases as the elastic modulus of the resin increases, especially 1kg / mm²It can be seen that when the value exceeds, it rapidly increases. Therefore, the elastic modulus of the embedded resin is 1 kg / mm ² The following is optimal. As such a resin, silicone resin, urethane resin or the like can be used.

[0009]

【Example】

 Next, an embodiment of this invention will be described. Since the overall configuration of the optical fiber gyro is the same as that of FIG. 1, the phase modulator will be described here.

An embodiment of the phase modulator incorporated in the optical fiber gyro of the present invention is shown in FIG. In this phase modulator, an optical fiber 9 is wound around a cylindrical piezoelectric vibrator 8, which is suspended in a dish-shaped member 10 at a distance from the bottom surface 10a, and a resin 11 is injected into the member 10 in that state. The piezoelectric vibrator 8 is held by being suspended in the member 10. A modified silicone resin or urethane resin having an elastic coefficient of 0.01 kg / mm ² is suitable as the resin 11, but other resins having no elastic characteristic are suitable as long as the elastic coefficient is about the same. This phase modulator is mounted by screwing or adhering the dish-shaped member 10 to the housing of the optical fiber gyro. When this phase modulator was incorporated into an optical fiber gyro and the modulation voltage was examined, it was possible to modulate with a sufficiently small value, and the characteristics of the optical fiber gyro were good. Since the piezoelectric vibrator 8 is held by the soft resin 11 in this phase modulator, it is less susceptible to external vibrations and has the advantage of not transmitting the mechanical vibrations of the piezoelectric vibrator 8 to the outside.

FIG. 3 shows another embodiment of the phase modulator according to the present invention. In this phase modulator, when the piezoelectric vibrator 8 around which the optical fiber 9 is wound is attached to the member 10, a thread-like small piece 12 of an elastic material such as urethane rubber is interposed between the bottom surface 10a of the member 10 and the piezoelectric vibrator 8. It was made. By interposing the thread-like small piece 12 in this way, it is possible to surely and easily separate the piezoelectric vibrator 8 from the bottom surface 10a of the member 10, and it is possible to improve the mounting accuracy.

In the above embodiments, the structure in which only the lower portion of the piezoelectric vibrator 8 is embedded in the resin 11 is shown, but the present invention is not limited to this, and the entire piezoelectric vibrator 8 may be embedded. In that case, it is necessary to use a member deeper than the dish-shaped member 10. Further, if the corrosion preventing material of the phase modulator 4 is used for the resin 11, it is possible to prevent the electrodes of the phase modulator from corroding and prolong the life of the device.

[0013]

[Effect of device]

 In summary, the optical fiber gyro of this invention has the following excellent effects.

(1) Since the piezoelectric vibrator of the phase modulator is gently held by the resin, the characteristics of the phase modulator are always kept constant, and stable and good angular velocity detection sensitivity can be obtained.

(2) Since the elastic coefficient of the resin holding the piezoelectric vibrator is selected to be 1 kg / mm ² or less, the detection sensitivity can be optimized.

(3) When the piezoelectric vibrator is attached, the conventional adjustment work by screwing is not required, so that the assembling workability is good and the mass productivity is excellent.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an optical fiber gyro.

FIG. 2 is a vertical sectional view showing an embodiment of a phase modulator incorporated in the optical fiber gyro of the present invention.

FIG. 3 is a side sectional view showing another mounting example of the phase modulator incorporated in the optical fiber gyro of the present invention.

FIG. 4 is a graph showing a relationship between an elastic coefficient of a resin holding a piezoelectric vibrator and a modulation voltage of the piezoelectric vibrator.

FIG. 5 is a vertical sectional view showing a conventional phase modulator.

[Explanation of symbols]

 1 Light source 2 Light receiver 3 Optical fiber coil 4 Phase modulator 5a Directional coupler 5b Directional coupler 6 Polarizer 7 Circuit board 8 Piezoelectric vibrator 9 Optical fiber 10 Member 11 Resin 12 Thread-like small piece (spacer)

Claims (2)

[Scope of utility model registration request] 1. An optical fiber gyro characterized in that a piezoelectric vibrator of a phase modulator is elastically held by a resin so as to float above a member to which the piezoelectric vibrator is attached. 2. The optical fiber gyro according to claim 1, wherein the elastic modulus of the resin is 1 kg / mm ² or less.