JPH0834326B2 - Ring laser gyro dither mechanism - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a dither mechanism of a ring laser gyro that detects a rotational angular velocity as an inertial reference device for an aircraft or other aircraft.

BACKGROUND OF THE INVENTION A highly accurate rate gyro is used as a device for detecting the angular velocity of motion of a spacecraft. In recent years, the development of optoelectronic technologies such as lasers has led to the development of ring laser gyros and their use in inertial reference devices.

The ring laser gyro has a closed optical path that is directed in the sensing plane of the gyroscope from a laser light source, a reflecting mirror, a prism, a photodetector, and the like. The two laser beams pass through the optical path at the same time, clockwise and counterclockwise. When this device receives a clockwise rotation from the outside, for example, the path of light traveling in the clockwise direction becomes longer than the path of light traveling in the counterclockwise direction, and a difference occurs in the frequency of the light traveling in both directions.・ Detecting interference fringes of light with a detector such as a diode, it is possible to know the angular displacement, angular velocity, and rotation direction by the number of movements, velocity, and direction of the fringes.

In the ring laser gyro, as the input rotation speed decreases, the frequency difference between the two laser beams passing in opposite directions decreases, and the rotation speed of the gyro becomes less than zero. The so-called "lock-in" (lock-) that tries to vibrate at a common frequency at an early stage
in) phenomenon. As a result, the detection function for minute angular velocity is lost.

As one of the means to prevent this lock-in phenomenon,
The entire gyro is mechanically vibrated (dither) about its sensitivity axis.

The portion of the ring laser gyro through which the laser light passes is generally a triangular block made of a material such as fused quartz, which has a very small coefficient of thermal expansion in order to prevent changes in the length of the optical path due to heat. It is composed of.

The dither mechanism for giving vibration to this is arranged in the block, and usually has a cylindrical outer peripheral wall and a plurality of arms extending radially from the center of the inside.
Piezoelectric elements are attached to both sides of these arms, and the arms are deformed by applying alternating voltages of opposite phases to each other.
Angular vibration is applied to the outer peripheral wall to vibrate the block body of the ring laser gyro.

In order to mount this kind of cylindrical dither mechanism in the block of the ring laser gyro, a circular opening corresponding to the outer shape of the dither mechanism is formed in the block,
A dither mechanism is installed in this circular opening.

[Problems to be Solved] By the way, in the conventional ring laser gyro provided with the dither mechanism configured as described above, as described above, the block is made of a material whose coefficient of thermal expansion is almost zero. However, the dither mechanism must be made of a material having a larger coefficient of thermal expansion than that. Therefore, when the ambient temperature of the gyro is changed, the dimensional change due to the heat of the block is extremely small, but the dimensional change due to the heat of the dither mechanism causes the block to be distorted, which eventually leads to good oscillation of the laser. It causes a big trouble.

Further, in the conventional dither mechanism, the arm extending in the radial direction provided with the piezoelectric element has high radial rigidity of the dither mechanism at the portion where the cylindrical wall of the dither mechanism intersects with these arms. Therefore, when the ambient temperature rises, the stress acting on the block of the dither mechanism at this portion is large, which causes an obstacle to the oscillation of the laser.

In order to reduce such rigidity, it may be possible to solve it by reducing the thickness of the radial arm of the dither mechanism. However, if the arm is thin enough to be sufficiently rigid, it interferes with the frequency required to impart the desired mechanical vibration (dither) to the ring laser gyro block.

[Object of the Invention] In view of the many problems described above, the main object of the present invention is to provide a dither mechanism for a ring laser gyro that does not hinder the block even when the ambient temperature changes. To do.

An object of the present invention is to provide a dither mechanism of a ring laser gyro which is connected to a block at a portion of the dither mechanism having the lowest rigidity to give a desired minute vibration to the block.

[Configuration of the Invention] The preferred embodiments of the present invention will be described in detail with reference to the drawings. First, as shown in FIG. 1, a ring laser
The gyro is composed of a polygonal, generally triangular block 12 having a reflecting mirror 14 attached to each vertex, a prism 16 and a photodetector 18. A cathode 20 and an anode 22 are attached to the block 12, and a mixed gas of helium and neon is enclosed in the block 12 at a low pressure as a medium for laser oscillation. A high voltage is applied between the cathode 20 and the anode 22 to generate plasma discharge, and the laser medium is excited to oscillate laser light.

A dither mechanism is mounted on the block 12 in order to apply a minute vibration. The dither mechanism has a cylindrical outer peripheral wall portion 26 and an inner peripheral wall portion 26 that extends in the radial direction.
Consisting of a plurality of arms 28 supporting these arms
Piezoelectric elements on each side of 28 (not shown)
Are glued together. Usually, the dither mechanism having this cylindrical outer peripheral wall 26 is provided with a circular opening corresponding to the dither mechanism in the central portion of the block 12, the dither mechanism is fitted into the opening, and if necessary, adhered. There is.

FIG. 2 shows a first embodiment of the dither mechanism of the present invention. The dither mechanism has a cylindrical outer peripheral wall 26 and an adjacent arm.
A protrusion 32 extending radially outward from the outer surface of the outer peripheral wall 26 is formed at an intermediate portion between the connection portions 30 and 30 with the 28.

At the center of the block 12, there is formed an opening 34 having a radius of at least the radial length of the outer peripheral wall portion 26 of the dither mechanism and the radial length of the protrusion 32. The dither mechanism having the projecting portion 32 is attached to the opening 34 of the block 12 and assembled. In mounting, the ends of the protrusions 32 may be coated with an adhesive to join them, or may be simply press-fitted, or both may be used together.

FIG. 3 shows a second embodiment of the present invention. In this embodiment, the dither mechanism does not have any protrusion on the cylindrical outer peripheral wall portion 26 as in the conventional dither mechanism. Instead, the protrusion 132 corresponding to the first embodiment is formed on the inner peripheral surface of the circular opening 134 formed in the block 12. The means for mounting the dither mechanism of the second embodiment in the opening 134 with the protrusion 132 of the block 12 is the same as that of the first embodiment.

FIG. 4 is a schematic diagram illustrating a third embodiment of the present invention. In the third embodiment, neither the circular opening 34 of the block 12 nor the dither mechanism is provided with a protrusion,
The circular opening 34 in the block 12 is larger than the diameter of the dither mechanism, and at the location of the protrusion mentioned in the first and second embodiments above, a corresponding separate and independent mounting shim 232. The dither mechanism is attached to the opening 34 of the block 12 using.

According to this invention, the cut 50 is provided in the protrusion 32 of the dither mechanism of the first embodiment described above (fifth aspect).
Figure) can be done.

Further, as shown in FIG. 6 or 7, an outer peripheral wall 26 of a dither mechanism having a cylindrical outer peripheral wall 26 having no protruding portion.
A cut 52 is provided in the protrusion 132 of the opening 134 of the block 12 described in the second embodiment or the mounting portion of the mounting shim 232 of the circular opening 34 of the block 12 of the third embodiment. You can also match.

[Advantages of the Invention] The present invention has the configuration as described in detail above,
As is obvious from the contents, the dither mechanism is in contact with the block at the weakest portion in the radial direction. Therefore, the stress exerted on the block of the dither mechanism due to the change of the ambient temperature is almost ignored, and the risk of causing distortion in the block can be avoided.

Although the present invention has been described in detail with respect to the most preferable embodiment thereof, the present invention can be modified in various ways within the technical contents shown in the claims, and the block is not limited to a triangle, for example. The number of arms of the dither mechanism is not specified either.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining the outline of the structure of a ring laser gyro having a dither mechanism, FIG. 2 is a schematic diagram for explaining the first embodiment of the present invention, and FIG. 3 is a second diagram of the present invention. FIG. 4 is a schematic diagram for explaining an embodiment, FIG. 4 is a schematic diagram for explaining a third embodiment of the present invention, FIG. 5 is a schematic diagram for explaining a fourth embodiment of the present invention, and FIG. 6 and FIG. 9 is a schematic view illustrating an embodiment in which a cut is provided in the outer peripheral wall of the dither mechanism. The main reference numerals in the drawings are listed below. 12 …… Block 14 …… Reflecting mirror 16 …… Reflecting prism 18 …… Photodetector 20 …… Cathode 22 …… Anode 26 …… Outer peripheral wall 28 …… Arm 32 …… Projection 34 …… Block opening 52 ...... Discontinuity 124 ...... Dither mechanism (first embodiment) 134 ...... Block opening (second embodiment) 232 ...... Mounting shim

Claims (5)

[Claims] 1. A polygonal block is provided with a reflecting mirror at each vertex to form a closed optical path, and two laser beams are passed through the optical path in a clockwise direction and a counterclockwise direction, and a photodetector is applied to the block. A ring designed to detect the rotational movement that acts.
A laser gyro and a cylindrical outer peripheral wall for providing a minute vibration to the block by providing a circular opening in the block and mounting it on the block, and a plurality of arms extending radially from the center to the outer peripheral wall. A dither mechanism for a ring laser gyro configured to connect to a circular opening of the block at a least rigid portion of an outer peripheral wall of the dither mechanism. 2. A dither mechanism is provided with a protruding portion extending radially from the outer peripheral wall at the lowest rigidity portion of the outer peripheral wall, and the dither mechanism is connected to the circular opening of the block by the protruding portion. The ring laser gyro dither mechanism according to claim 1. 3. The ring according to claim 1, wherein a protrusion extending radially from an inner peripheral wall of the circular opening of the block is provided at a portion of the outer peripheral wall of the dither mechanism having the lowest rigidity. -Laser gyro dither mechanism. 4. A mounting shim for connecting the inner peripheral wall of the circular opening of the block and the outer peripheral wall of the dither mechanism to the lowest rigidity portion of the outer peripheral wall of the dither mechanism. The ring laser gyro dither mechanism according to item 1. 5. The dither mechanism for a ring laser gyro according to claim 1, wherein a cut is provided in a portion of the outer peripheral wall of the dither mechanism having the lowest rigidity.