JPS6036910A - Optical splitting and synthesizing device for optical fiber gyroscope - Google Patents

Abstract

PURPOSE:To interfere efficiently the respective laser luminous flux parts emitted respectively from both open ends of an optical fiber by providing the 1st polarizing beam splitter provided with a translucent film and the 2nd polarizing beam splitter and placing said splitters to face both open ends of the optical fiber. CONSTITUTION:An optical fiber gyroscope 10 has an optical fiber 11, a laser light source 12 and a detecting circuit 13. An optical splitting and synthesizing device 20 is interposed between the fiber 11 and the source 12. Biconvex lenses 21, 22 are provided to face respective both open ends 11a, 11b. The device 20 has prisms 23-26 formed to the same triangular shape. The base 24c is superposed and fixed via a translucent film g1 on the base 23c and the base 26c to the base 25c via a translucent film g2. The side face 25a is superposed and adhered to the side face 24b by means of a transparent adhesive agent in such a way that respective ridges 24a, 25d attain about 45 deg. angle with each other.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical fiber gyroscope, and particularly to an optical fiber gyroscope suitable for being interposed between a coiled optical fiber constituting the optical fiber gyroscope and a laser light source. This invention relates to a light splitting and synthesizing device.

Conventionally, as a light splitting/synthesizing device for this dish, there is a half mirror, for example, but in this half mirror, there is a polarization plane that easily transmits the laser beam from the laser light source and a polarization plane that easily reflects the laser beam. They are at different angles.

Therefore, after the laser beam from the laser light source enters the optical fiber from the first and second opening ends as the first and second laser beams under the reflection-transmission action of the half mirror, these beams are When the second and first laser beam parts emitted from the first and second opening ends respectively reach the half mirror, the first part of the first generated laser beam passes through the half mirror, and the second part of the laser beam passes through the half mirror. A problem arises in that the eastern part of the V-the light and the part reflected by the half mirror only partially interfere with each other due to the difference in their respective planes of polarization.

In addition, in single-mode fibers that have been conventionally used as optical fibers, while the eastern parts of each laser beam propagate within the fiber, the polarization state of each eastern part of each laser beam changes depending on the curvature of the fiber and the ambient temperature. There is a problem in that the effective optical path lengths of the respective laser beams propagating in opposite directions within the fiber differ as a result of disturbances caused by external disturbances such as vibrations and vibrations.

The present invention has been made in response to these problems, and its purpose is to provide an optical fiber gyroscope that efficiently interferes the eastern parts of each laser beam emitted from the openings at both ends of the optical fiber. An object of the present invention is to provide a light splitting and synthesizing device for the purpose of the present invention.

In order to achieve this object, the structural features of the present invention are as follows:
In an optical fiber gyroscope, a light splitting/synthesizing device is installed between a Kelcoil-shaped optical fiber and a laser light source, which faces the laser light source and is located at a distance of about 45 mm with respect to its optical axis.
a first polarizing beam splitter having a semi-transparent film that intersects at an angle of 45°; and a 14m optical beam splitter arranged behind the first polarizing beam splitter, which rotates the optical axis by approximately 45°. a second polarizing beam splitter, the second polarizing beam splitter having a semi-transparent film intersecting the optical axis so as to match the spatial relationship formed between the semi-transparent film of the first polarizing beam splitter and the optical axis when The optical fiber is provided with a vine, and both surfaces of the semi-transparent film of the second polarizing beam nullifier are arranged to face the opening ends of the optical fiber.

Therefore, by configuring the present invention in this way, if the laser beam has a linearly polarized plane or a circularly polarized light d,
The laser beam passes straight through the first polarized beam splitter through its semi-transparent film while maintaining a linearly polarized plane, and enters the second polarized beam splitter, and thus the second polarized beam splitter The laser beam incident on the second polarizing beam splitter is split into two laser beams each having a linear polarization plane perpendicular to each other by the semi-transparent film of the second polarizing beam splitter, and one of these plane-splitting laser beams becomes the second polarizing beam. The beam is transmitted straight through the semi-transparent membrane of the polarizing beam printer and enters the optical fiber from one opening end thereof, and the other side of the surface-splitting laser beam passes through the semi-transparent membrane of the second polarizing beam beam printer. The one split laser beam is reflected at right angles, passes through the second polarization splitter, and enters the optical fiber from the other open end, and each of the split laser beams is directed in opposite directions within the optical fiber. After propagating, one and the other of these plane-splitting laser beams exit from the other open end and the -open end of the optical fiber, respectively, and enter the second polarized beam meplinator toward each surface of its semi-transparent membrane. The one of the split laser beams incident in this way is reflected at right angles by the semi-transparent film of the second polarizing beam splitter, and enters the first polarizing beam splitter in a straight line toward the semi-transparent film. The other divided laser beam enters as a modified split laser beam having a plane of polarization, and the other split laser beam enters the second polarization beam nulli-sota, passes straight through the semi-transparent membrane of the second polarization beam nulli-sota, and passes straight through the modified split laser beam. The first polarized beam splitter enters the first polarized beam splitter as a modified split laser beam with a linear polarization plane orthogonal to the linear polarization plane of the beam, and thus the first
Both modified split laser beams entering the polarizing beam splinter are split and reflected by the semi-transparent film of the first polarizing beam splitter, and exit from the first polarizing beam splinter as a detection laser beam having the same linear polarization plane. These rain detection laser beams effectively and efficiently interfere with each other as highly accurate and stable interference light based on the same linear polarization plane and the phase difference between the two emitted split laser beams from the optical fiber. By using the resulting intensity of the interference light, the angular velocity of the optical fiber can always be determined as a highly accurate and stable value. In addition, even if the surface-split laser beam emitted from the optical fiber is disturbed in the plane of polarization due to the external disturbance described above, the surface-split laser beam is converted into each predetermined linearly polarized beam by the second polarization beam nupritzer. Since the interference light is corrected into the corrected split laser beam having a plane, the interference light is not affected by the effective optical path length difference based on the above-mentioned disturbance of the polarization plane.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.
The figure shows a fiber optic gyroscope 10 to which the present invention is applied. The fiber optic gyroscope 10 includes an optical fiber 11, a laser light source 12, and a detection circuit 16.
Between the optical fiber 11 and the laser light source 12, a light splitting/synthesizing device 20, which constitutes the main part of the present invention, is interposed. The optical fiber 11 is made of a coiled single mode fiber, and biconvex lenses 21 and 22 constituting a light splitting and combining device are opposed to the biconvex end portions 11a and 11b of the original fiber 11, respectively. The laser light source 12 operates along its leading axis and at the same time the light splitting and combining device 20
Laser beam A towards.

emits. In this case, the laser beam A. is the linear polarization plane PA
O (see Figure 6).

As shown in FIGS. 1 and 2, the light splitting and combining device 20 includes prisms 25 and 2 formed into the same triangular prism shape.
4,25.26. The prism 26 is 90°
Both side surfaces 26a forming an apex angle of.

23b, and a bottom surface 23c opposite to the apex angle, and a ridge 23 formed by both side surfaces 23a and 23b at the apex angle.
(1 (parallel to the bottom surface 23c)) The prism 26 has an isosceles triangular cross section. In this case, the side surface 23.2 of the prism 26 is
The ridge 23 on both sides 23a, 231) is perpendicular to the course of the laser beam Ao from 2 (that is, the optical axis of the laser light source).
d is the laser beam A.

is perpendicular to the linear polarization plane PAO. The prism 24 is
Both side surfaces 24a correspond to both side surfaces 26a, 231), bottom surface 26c, and edge 23d of the prism 26, respectively.

24b, a bottom surface 24C, and a ridge 24a, and the bottom surface 24c of this prism 24 has a base 26d.

24a are polymerized and fixed to the bottom surface 23c of the prism 26 via a semi-permeable membrane GL so that they are both oriented in the same direction.

Similar to prism 24, prism 25 is similar to prism 26.
Both sides 23a, 231), bottom 23c and edge 23C1
Both sides 25/I and 25b respectively correspond to .

The prism 25 has a bottom surface 25c and an edge 25'd, and the side surfaces 25.2 of the prism 25 are arranged so that the respective sides 24ti, 25cL form an angle of about 45 degrees with each other.
41) with a transparent adhesive. Also,
The prism 26 has both sides 23a and 23b of the prism 26, as well as both prisms 24 and 25.

Both side surfaces 25 correspond to the bottom surface 230 and the edge 23d, respectively.
a, 251), has a bottom surface 25c and a ridge 25d,
The bottom surface 26C of this prism 26 is
(The bottom surface 2 of the prism 25 is
5c through a semipermeable membrane 2. In such a case, the side surface 251) of the prism 25 faces the open end 111) of the optical fiber 11 through the convex lens 22, and the side surface 26b of the prism 26 faces the open end 11a' of the optical fiber 11 through the convex lens 21. I'm facing KJJ. Note that the detection circuit 13 includes an optical sensor 13a and an amplifier 131).
have.

In this embodiment configured as above, the laser light source 1
2 to laser beam Ao (with linear polarization plane PAO)
occurs, this laser beam A. is incident on the side surface 23a of the prism 26, as shown in FIG. Then, the laser beam A. The linear polarization plane PAO of both prisms 23.2
The laser beam A is perpendicular to the beams 23d and 24d of 4. is transmitted straight through the semi-transparent membrane g1 while maintaining the same linear polarization plane PAO, and is transmitted straight through the side surface 24 of the prism 24. b
The light exits from the beam and enters the side surface 25a of the prism 25. Next, when the laser beam Ao reaches the half 3fi I part 92 of the prism 25, each part 24d of both prisms 24.25,
25t1 make an angle of about 45° to each other, so the laser beam A.

However, the semi-transparent film 92 divides the laser beam B1 almost equally into a laser beam B1 having a linear polarization plane FBI and a laser beam Pc1 having a linear polarization plane Pa+ (orthogonal to the linear polarization plane FBI). The laser beam C1 is transmitted straight toward the side surface 26b of the prism 26, while the laser beam C1 is reflected by the semi-transparent film g2 at right angles to the traveling direction of the laser beam Ao, and is transmitted straight toward the side surface 25'b of the prism 25. This means that both prisms 25, 26 and semi-transparent membrane g2 have a linear polarization plane PAo in relation to the spatial positional relationship with both prisms 26, 24 and semi-transparent membrane gl.

This means that it has strong polarization plane selectivity as a polarization beam nullifier in that it splits the laser beam into laser beams Bl and C1 having linear polarization planes PBl and Pot perpendicular to each other, respectively.

As described above, each of the laser beams B1 and C1 is directed to the side surface 261 of the prism 26 and the side surface 2 of the prism 25, respectively.
When emitted from 5b, a laser beam B is emitted.

As shown in FIG. 1, the laser beam C1 passes through the convex lens 21, enters the optical fiber 11 from its open end 1112, and propagates inside the optical fiber 11, and the laser beam C1 passes through the convex lens 22 and enters the optical fiber 11. The light enters from the open end 11b and propagates within the optical fiber 11 in the opposite direction to the laser beam B1. When the propagation in the optical fiber 11 is completed in this way, the laser beam B1 is transferred to the elliptically polarized light plane FB2.
The laser beam B2 is emitted from the open end 111) of the optical fiber 11, passes through the convex lens 22, and enters the prism 2.
The laser beam C7 enters the side surface 25b of the optical fiber 11 as a laser beam C2 having an elliptically polarized plane PO2, and exits from the open end 11a of the optical fiber 11 and passes through the convex lens 21.
and enters the side surface 26b of the prism 26. In such a case, assuming that the optical fiber 11 is rotating at an angular velocity ω, a phase difference Δφ will occur between the two laser beams B2 and 02. In addition, each elliptical polarization plane PB 2 + "C! of both laser beams "2+02" Each direction of the major axis and minor axis of No. 2 and the ellipticity are indefinite.

As described above, each of the laser beams B2 and C2 is directed to the side surface 251 of the prism 25 and the side surface 26 of the prism 26, respectively.
1), the laser beam B2 travels straight through the prism 25, is reflected by the semi-transparent film q2 at right angles (corresponding to the direction opposite to the direction of travel of the laser beam A), and forms a linear polarization plane P.
The laser beam C2 enters the side surface 24b of the prism 24 as a laser beam B21 having a polarization angle B21, and the laser beam C2 travels straight through both prisms 26, 25 from the side surface 261) to the side surface 25b, and becomes a linearly polarized plane PO21 (linearly polarized plane PB2). prism 2 as a laser beam C21 with
The light is incident on the side surface 24b of 4.

Then, each school 24d of both prisms 24.25.

25 (Since i forms an angle of about 45 degrees with each other, the laser beam B21 is divided into a laser beam B211 having a linear polarization plane PB211 and a laser beam B2+ having a linear polarization plane PE212 at the semi-transparent film 9□. The laser beam C21 is divided almost equally, and the semi-transparent film divides the laser beam C21 into a laser beam C211 having a linear polarization plane PC!211 (corresponding to the linear polarization plane "B211") and a linear polarization plane PO21.
2 (coinciding with the linear polarization plane PB2]2) and the laser beam C212 is almost equally divided. That means,
Both prisms 24 and 23 and semipermeable membrane gl are connected to both prisms 2
5°26 and the spatial positional relationship with the semi-transparent film 7□, the laser beam B21 (or C21) having the linear polarization plane FB2+ (or PC2+) is transferred to each one-page linear polarization plane PB211 (or PC2+) at right angles to each other. or PO211) and FB
Laser beam B21 having 2+2 (or "02+2")
1 (or C21□) and B212 (or 02+2
), meaning that it has strong polarization plane selectivity as a polarization beam controller.

As described above, each laser beam B21. When C21 is split together, both laser beams B212 + 0212 are transmitted straight toward the 111th surface 23d of the prism 2B and returned to the laser light source 12, while the remaining laser beams B2
11 + 0211 is the laser beam A at the semi-transparent membrane g1
.

The light is reflected perpendicularly to the traveling direction of the prism 24, passes straight through toward the side surface 24b of the prism 24, is emitted, and enters the optical sensor 13.2 of the detection circuit 16. In such a case, both laser beams B
Since the respective linear polarization planes of B211 and C211 coincide with each other, both laser beams B211 and C2,1 effectively interfere with each other due to the phase difference Δφ and form an interfering laser beam D (see Fig. 1). The light enters the sensor 13a. Also, each laser beam B2.
Since only a constant linear polarization plane of C2 is taken out, the effective optical path length difference due to disturbance of the polarization plane is reliably eliminated by the reciprocity of the laser beam, and as a result, the interference laser beam beam is Highly accurate and stable light can be obtained without being affected by external disturbances as described in .

Therefore, the intensity P of the interference laser beam is
3a, the detection circuit 16 detects the optical sensor 1.
Since an electric signal representing the intensity P is generated under the amplification effect of the detection result 6a by the amplifier 131), the relational expression Δφ=4πAω/λC due to the Sagnac effect (where A: optical path cross-sectional area of the optical fiber 11, λ: Wavelength of laser beam, C:
Based on the value P of the electrical signal, the angular velocity ω of the optical fiber 11 can always be determined as an accurate and stable value based on the speed of light in vacuum) and P, (cos2Δφ).

As explained above, in the above embodiment, in the light splitting and combining device interposed between the coiled optical fiber and the laser light source in the optical fiber Shironu Coop,
The first one is each formed into a triangular prism shape having an isosceles triangular cross section with an apex angle of 90°, both side faces forming the apex angle, and a bottom face opposite to the apex angle. Second. A sixth and a fourth transparent solid body are provided, the first transparent solid body is arranged to receive a laser beam generated from the laser light source on one of its both sides, and a ridge formed by both sides of the second transparent solid body is provided. and ridges formed by both side surfaces of the first transparent solid body], the second transparent solid body is superposed on the bottom surface of the first transparent solid body via a first semipermeable membrane so that the second transparent solid body is oriented in the same direction. and the sixth transparent
The sixth transparent solid is attached to one of its two sides so that the edge formed by both sides of the clear solid and the edge formed by both sides of the second transparent solid forms an angle of approximately 45°. A superimposed heel is formed on one of both sides of the solid. The fourth transparent solid is oriented so that the ridge formed by both sides of the fourth transparent solid and the ridge formed by both sides of the sixth transparent solid are in the same direction. The bottom surface of the sixth transparent solid body is polymerized through a second semipermeable membrane, and the other of the both sides of the sixth transparent solid body and one of the both sides of the fourth transparent solid body perpendicular thereto are This is because the openings at both ends of the optical fiber are arranged to face each other.

By configuring the present invention in this way, if the laser beam has a linearly polarized plane or a circularly polarized plane,
The laser beam maintains its polarization plane as it is,
The first and second transparent solids are passed through the overlapping surface of the first and second transparent solids, that is, the first semi-permeable membrane, from one of both sides of the first transparent solid, and the second and sixth transparent solids are The laser beam is transmitted straight toward the three-dimensional polymerization surface, and is split into two laser beams each having a linear polarization plane perpendicular to each other at the sixth and fourth polymerization surfaces, that is, the second semi-transparent film. One of the laser beams on both sides travels straight through the fourth transparent solid body, exits from one of both sides of the fourth transparent solid body, enters the optical fiber from one opening end, and enters the optical fiber into the optical fiber. The other side laser beam is aligned with the one divided laser beam by the second semi-transparent film and is perpendicularly opposite to the divided laser beam so that the output of the sixth transparent solid in the fourth transparent solid is U=t [on the 111th plane] The laser beams are emitted from one of the two orthogonal side surfaces and enter the optical fiber from its low-volume end, and after the divided laser beams propagate in opposite directions within the optical fiber, they are divided into two beams. One and the other of the side laser beams are connected to the optical fiber with a low
The one of the split lasers is emitted from the A end and the opening end, respectively, and enters the sixth and fourth transparent solids from one of the both sides thereof, and enters the sixth transparent solid. The light is reflected at right angles by the second semi-transparent film and enters the second transparent solid body as a modified split laser beam having a linear polarization plane, and the other split laser beam enters the fourth transparent solid body. The laser light beam goes straight as it is, passes through the sixth transparent solid body, and enters the second transparent solid body as a modified split laser beam having a linear polarization plane perpendicular to the linear polarization plane of the modified split laser beam, and thus Both corrected split laser beams incident on the second transparent solid body are split and reflected together by the first semi-transparent film, and are emitted from a side surface of the second transparent solid body as a detection laser beam having the same linear polarization plane. Therefore, based on the same linear polarization plane and the phase difference between the two emitted split laser beams from the optical fiber, these rain detection V-the optical beams produce highly accurate and stable interference light that effectively and efficiently interfere with each other. As a result, by using the intensity of such interference light, the angular velocity of the optical fiber can always be determined as an accurate and stable value. Furthermore, even if the plane of polarization is disturbed due to the above-mentioned external disturbance in the laser beams on both sides emitted from the optical fiber, the laser beams on both sides will not be affected by the sixth and fourth transparent solid bodies. Second, since the modified split laser beams are modified to have respective predetermined linear polarization planes, the interference light is not affected by the difference in effective optical path length due to the disturbance of the polarization planes described above.

Note that in the above embodiment, the laser beam A is the laser beam A.

An example was explained in which has a linear polarization plane IPAo, but
In place of this, laser beam A. Even if the prism has a circularly polarized plane, the laser beam incident from the prism 24 to the prism 25 is modified by the prism 23, 24 and the semi-transparent film gI so that it has a linearly polarized plane PAO. The same effect can be achieved.

Further, in the embodiment, the side surface 25a of the prism 25 is aligned with the side surface 25a of the prism 25 so that the angles 24a and 25d of the prisms 24 and 25 form an angle of about 45 degrees as shown in FIG.
An example was explained in which polymerization was adhered to the side surface 241) of
For example, the prisms 24d and 25 (1) are arranged at an angle of about 45° in the opposite direction to that in FIG.
The 1111 surface 25a of the prism 24.5 may be polymerized and bonded to the side surface 24b of the prism 24.
The joint surfaces of No. 5 are not limited to the respective side surfaces 24b and 2512.

Further, in carrying out the present invention, a first half mirror provided with a semi-transparent film facing the laser light source 12 and intersecting at about 45 degrees with respect to the optical axis thereof, and a first half mirror disposed behind the first half mirror are provided. When the first half mirror is rotated about 45 degrees about the optical axis, the first half mirror
a second semi-permeable membrane that intersects the optical axis so as to match the circular positional relationship formed between the semi-permeable membrane and the optical axis;
Even if both surfaces of the semi-permeable film of the second half mirror of the half mirror and the other half mirrors are arranged to face both open ends of the optical fiber 110, substantially the same effect as that of the embodiment described above can be obtained. It can be achieved. In such a case, the first and second
In place of the half mirror, plate-shaped first and second beam splitters are adopted, and each semi-transparent membrane of the first and second beam splitters is connected to each semi-transparent membrane of the first and second half mirror. Even if arranged in the same manner as the membrane, substantially the same effects as in the previous embodiment can be achieved.

Moreover, in the embodiment, the prisms 26 to 26 are
Each was formed into an isosceles triangular prism shape with an apex angle of 90c,
However, the present invention is not limited to this, and the apex angles of the prisms 26 to 26 may be changed to angles other than 900, or the prisms 26 to 26 may be formed into scalene triangular prism shapes.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of an optical fiber gyroscope to which the present invention is applied, FIG. 2 is an enlarged view of the device of the present invention, and FIG. 6 is an explanatory diagram showing the operation of the device of the present invention. . Explanation of symbols 11... Optical fiber, 11a, 11b... Open end portion, 12... Laser light source, 2o... Light splitting and combining device,
26...First transparent solid, 24...Second transparent solid, 2
5...Sixth transparent solid, 26...Fourth transparent solid, 23
(2, 23b, 24a, 24b, 25a. 25b, 26 (1, 26'b... 倶) J side, 2
3c, 24c. 25c, 26c...bottom, 23d, 24d, 25d. 26d...Redge, "l 1g 2 see semi-permeable membrane. Applicant Nippondenso Co., Ltd. Agent Patent attorney Teru Hase - Figure 1 7 Figure 2

Claims (1)

[Claims] In a light splitting/synthesizing device interposed between a coiled optical fiber and a laser light source in an optical fiber Shironukog, the light splitting/synthesizing device faces the laser light source and is located at a distance of about 45 mm with respect to its optical axis.
a first polarized beam printer equipped with a semi-transparent membrane that intersects at a degree of a second polarizing beam splitter having a semi-transparent film that intersects the optical axis so as to match the spatial relationship formed between the semi-transparent film of the first polarizing beam splitter and the optical axis when Sota and this second
1. A light splitting and combining device for an optical fiber gyroscope, characterized in that both surfaces of a semi-transparent film of a polarizing beam nulli-sota are opposed to both opening ends of the optical fiber.