JPH0328807A - Multifiber optical rotary joint - Google Patents

Abstract

PURPOSE:To reduce the transmission lass by providing a variable speed gear mechanism which drives and rotates a trapezoidal prism at the angular velocity of a half as fast as that of a rotary body and a reflecting body which reflects and guides the light in an area outside the diameter of the trapezoidal prism to the trapezoidal prism. CONSTITUTION:Converging lenses 9a, 9b, 9c ... i receptacles 15a, 15b, 15c ...are provided on the side of the incidence surface 3a of the trapezoidal prism 3 on an axis parallel to the prism optical axis, and rhomboid prisms 30a, 30b, 30c ... are disposed on a fixed body 1 as reflecting bodies between the trapezoidal prism 3 and converging lenses Similarly, converging lenses 10a, 10b, 10c ...and rhomboid prisms 31a, 31b, and 31c are disposed on the rotary body 2 on the side of the projection surface 3. Further, the variable speed gear mechanism 22 reduces the angular velocity of the rotation of the rotary body 2 to a half. Consequently, the distance between optical fibers 14 and 5 is shortened by the short-sized trapezoidal prism 3.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to a multi-core optical rotary join that optically connects a plurality of optical fibers installed on a rotating body and a fixed body using a trapezoidal prism. It concerns l. [Prior Art] Conventionally, a multi-core optical rotary joint shown in FIG. 6 (Japanese Utility Model Application No. 61-6818) has been known. ing.
As shown in the figure, a rotating body 2 and a prism holder 4 that supports a trapezoidal prism 3 are rotatably provided coaxially within the fixed #1. The output side optical fibers 5a, 5b are coupled to the entrance surface 3a of the trapezoidal prism 3 by ferrules 6a, 6b attached to the fixed body 1 and collimating rod-shaped converging lenses 9a, 9b, and the input side optical fiber 14a ．． 14b is the exit surface 3c of the trapezoidal prism 3 by the ferrules 13a, 13b attached to the rotating body 2 and the collimating focusing lenses 10a, 10b.
is connected to. Between the rotating body 2, the prism holder 4, and the fixed body 1, there are speed change gears 40, 41, and 42 as a speed change gear mechanism for decelerating the rotation of the rotating body 2 to an angular velocity of 172 and transmitting it to the prism holder 4. and transmission gear shaft 4
3 are provided. The light emitted from the output photometric fiber 5a is converted into a thousand lines by the converging lens 9a, enters the entrance surface 3a of the trapezoidal prism 3, is refracted there, is totally reflected at the bottom surface 3b, and is further refracted at the exit surface 3C. The light is emitted, is focused by the focusing lens 10b, and enters the input side optical fiber 14b. Further, the output side optical fiber 5b and the input side optical fiber 14a are connected in the same way. In this optical rotary joint, even if the rotating body 2 rotates, the trapezoidal prism 3 rotates in the same direction at 1/2 the angular velocity, and acts to optically cancel the rotation of the rotating body 2. The connection relationships between the output side optical fiber 5a and the input side optical fiber 14b and between the output side optical fiber 5b and the input side optical fiber 14a are guaranteed. Also, Figure 7 (Jet Application 1986-1)
57843) has also been proposed. The multi-core optical rotary joint 1 shown in FIG. 7 is an improved version of the multi-core optical rotary joint shown in FIG. Similarly, rotating body 2
An intermediate optical fiber 11 and a focusing lens 10 are installed between the input side optical fiber 14 and the trapezoidal prism 3. Between the rotating body 2, the prism holder 4 and the fixed body 1,
As shown in the figure, a speed change gear 23, 24, 25, 26 and a speed change gear shaft 7 are provided as a speed change gear m for decelerating the rotation of the rotating body 2 to an angular velocity of 172 and transmitting it to the prism holder 4. ．． Also, there is a connector fil! for fittingly connecting the optical fiber 5 and the optical fiber 8 on the output side. (receptacle 18 and plaque 15) and a connector mechanism (receptacle 19 and plug 46) for fitting and connecting the optical fiber 14 and optical fiber 10 of the input opening, light is connected from the output opening to the input opening. There is. [Problem to be Solved by the Invention] As shown in FIG. 6, the relationship of an inverted fi image between the incident image and the output image with respect to the optical axis is caused by changing the aperture of the trapezoidal prism 3. S, the length is J=4.23xS (in the case of prism material BK-7). Further, the outer diameter of optical connectors (receptacles 15, 16, etc.) is usually 6 to 101 Il, and for example, in a 4-core optical rotary joint, S. =15~20flfl, J + =
It becomes 63.5 to 84.61. However, as shown in Figure 5, the coupling loss between optical fibers increases rapidly when the distance between the focusing lenses exceeds 50 mm.When J, = 63.5 to 84.6 nm, the coupling loss is 3 to 7 dB. and increases significantly. Also plug 20
If there is a slight angle bend when the lenses a and 20b are attached to the receptacles 15a and 15b, the light beam will be expanded by the entrance surface 3a, bottom surface 3b, and exit surface 3c of the trapezoidal prism 3, which will deteriorate the rotational characteristics of the multi-core optical rotary joint. Let. In particular, as the length 1 of the trapezoidal prism 3 becomes longer, the expansion of the luminous flux due to this angular bending becomes more significant, so it is better to make the prism length as short as possible. In order to improve these problems, an intermediate optical fiber 8 is inserted between the receptacle 18, 19 and the trapezoidal prism 3 as shown in FIG.
and 11 to improve the packaging density, but if the intermediate optical fiber 8.11 is bent excessively, the loss will be large.
Moreover, there is a risk of it breaking, so it needs to be a certain length. Therefore, even though the length j2 of the trapezoidal prism 3 has become shorter, the overall length of the rotary joint +
becomes very large, making it difficult to connect to rotating parts.
Furthermore, the end of the intermediate optical fiber 8.10 needs to be terminated to a connector ferrule and polished, which increases manufacturing costs and increases the number of connection points by two, increasing connection loss. [Means for Solving the Problems] The present invention includes a trapezoidal prism that is rotatably provided coaxially with the rotating body between a rotating body and a fixed body, and a trapezoidal prism that transmits the rotation of the rotating body to the trapezoidal prism. A speed change gear t! for rotationally driving the rotating body at an angular velocity of 172. a reflector, which is provided on each of the entrance and exit surfaces of the trapezoidal prism and reflects light in an area outside the aperture of the trapezoidal prism and guides it to the trapezoidal prism as light within the aperture along the axial direction of the trapezoidal prism; A plurality of pairs of converging lenses are installed on a rotating body and a fixed body so as to optically face the entrance and exit surfaces of the trapezoidal prism through a reflector, and are optically opposed to each other, and these lenses and exit surfaces. The input and
It is equipped with an output side optical fiber. [Function] The output light of the output curved optical fiber is converted into parallel light by a converging lens located outside the aperture of the trapezoidal prism, and is reflected by a reflector to become light along the axial direction of the trapezoidal prism, forming a trapezoidal shape. The light is incident on the entrance surface of the prism. The light that enters the trapezoidal prism from its entrance surface is changed in its course by the trapezoidal prism, which creates an inverted mirror image relationship between the input image and the output image with respect to the optical axis, and the light travels along the axial direction of the trapezoidal prism. The light is emitted from the exit surface. The light emitted from the exit surface of the trapezoidal prism is reflected by a reflector, guided to a focusing lens located outside the aperture of the trapezoidal prism, and coupled to the incident curved optical fiber by the focusing lens. Since the trapezoidal prism is rotated at an angular velocity of 172 times that of the rotating body, the rotated image on the rotational body side is made into a static image by the trapezoidal prism and transmitted to the fixed body side. Or fixed. The static image on the body side is converted into a rotating image with the same angular velocity as the rotating body by a trapezoidal prism and is transmitted to the rotating body side. Therefore, even if the rotating body rotates, the connection between the corresponding input and output optical fibers on the rotating body side and the fixed body side, which face each other via the trapezoidal prism, is maintained. [Example] An actual example of the present invention will be explained below based on the drawings. In FIG. 1, reference numeral 1 denotes a fixed body, into which a part of a rotating body 2 is inserted and supported rotatably. Further, a prism holder 4 for supporting a trapezoidal prism 3 is provided on the fixed body 1 on the rotation axis of the rotary body 2. The ends of the prism holder 4 are supported by the fixed body 1 and the rotating body 2 via bearings, respectively. Incidence surface 3a of trapezoidal prism 3
On the side, there is a receptacle 15a on the prism parallel to the optical axis.
Convergent lenses 9a, housed in 15b, 15c...
9b, 9c, .
0b, 30c... are installed on the fixed body 1. The long rhombic prism 30 is provided so that both end faces are total reflection surfaces giving an angle of 90". Similarly, the output surface of the trapezoidal prism 3 has a prism optical axis. and receptacles 16a, 16b, 16c on parallel axes.
The focusing lenses 10a. 10b,10
c..., and between the prism 3 and the converging lens 10, long rhombic prisms 31a, 3lb, and 31c are connected to the rotary tree 2.
It is installed in Focusing lenses 9, 10 housed in receptacles 15.16 and output photometric fiber 5 housed in plugs 20.21 and held by ferrules 6.13
, and the input side optical fiber 14 are optically coupled by screwing a plug 20.21 to a receptacle 15.16. A variable speed gear mechanism 22 is provided within the fixed body 1 of the prism holder 4 that opens outward, and that reduces the rotation of the rotating body 2 to an angular velocity of 172 (rotation in the same direction) and transmits the speed to the prism holder 4. The variable speed gear mechanism 22 includes a gear 23 attached to the outer periphery of the rotating body 2 and teeth II attached to a shaft 27 rotatably supported within the fixed body 1 and meshing with the gear 23.
24, and a gear 25 that is provided on the shaft 27 and meshes with a gear 26 at the center outer circumference of the prism holder 4. The gears 24 and 25 of the intermediate gear are divided into two parts 24a, 24b and 25a, 25b so that there is a relative rotational deviation in the rotational direction, and between the two divided gears there is a groove in a direction that causes a rotational deviation in these parts. A resilient member such as a resilient spring is provided.

Note that 28 is a rotating part that transmits the rotation of the rotating part to the rotating body 2 for optical transmission. The light emitted from the output side optical fiber 5a is converted into a parallel beam by a converging lens 9a, and enters a long rhombic prism 30a from its surface. The light incident on the long rhombic prism 30a is totally reflected by the end face located outside the aperture of the trapezoidal prism 3, changes its course at right angles, and returns to the long rhomboid prism 3.
0a (radial direction of the trapezoidal prism 3), is totally reflected vertically at the end face located inside the diameter of the trapezoidal prism 3, and is emitted from the stamp surface of the long rhombic prism 30a.
The light is incident on the entrance surface 3a of the trapezoidal prism 3 parallel to the axis of the trapezoidal prism 3. The light from the incident surface 3a is totally reflected by the bottom surface 3b, refracted by the exit surface 3C, and becomes a thousand lines of light along the optical axis.
The light enters the long rhombic prism 3lb, is totally reflected twice within the prism as described above, and is propagated from the focusing lens 10b to the incident side optical fiber 14b. The same applies to the other input and output optical fibers. When the rotating body 2 rotates at an angular velocity of ω, the prism holder 4 and the trapezoidal prism 3 are driven to rotate in the same direction at an angular velocity of 1/2 ω by the variable speed gear mechanism 22. It is designed to be
As detailed in the publication, the image of the rotating body 2 is in a stationary state when viewed from the fixed body 1, so regardless of the rotation of the rotating body 2, the multiple pairs of output and input optical fibers 5 , 14 connections are possible. In Figure 1, if the optical fiber has 4 cores, the plug 20
Considering the space for inserting and removing the plugs, the installation pitch of the plugs 20 is 16nn, and when the 5ll square long rhombic prism 30 is inserted, the aperture S3 of the trapezoidal prism 3 is 1211mm.
'l, length II s Cj = 4.23xS)
becomes 50.8In. A long rhombic prism 30.
Adding the optical path length in 31, the spacing between the focusing lenses 910 becomes 68n+n. Therefore, the coupling loss is 3.3 dB from Fig. 5, and when the input and output side optical fibers are directly connected to the trapezoidal prism with an optical connector as shown in Fig. 6 (in the case of 4 cores, j = 8 All, the coupling loss is 6 dB). ~7 dB
), the coupling loss can be reduced to about 172.

Next, if the optical fiber has 6 cores, the spacing between the optical connectors is 22
1i1, the aperture S of the trapezoidal prism is 13nn, and adding the optical path length of the long rhombic prism, the distance between the focusing lenses in Fig. 5 becomes 70ni, and the coupling loss is 4.0.
dB. When multi-core fibers are used as the intermediate optical fiber 811 in FIG. 7, the diameter S of the trapezoidal prism becomes 13 l in the same way with 6 fibers, and the coupling loss at that time is 2.0 dB.
Although it is small, there are two optical connector connections at the input and output ends of the intermediate optical fiber 8.11, and the connection loss is 2 dB (usually,
(The optical connector connection is 1 dB/1 location), and the total insertion loss is 4 dB, which is the same as that using the long rhombic prism in Figure 1, but the total length of the rotary joint L1 in Figure 7 is the intermediate optical fiber length (taking into account workability during production and providing an optimal offset) 60 to 8
If 0nn is added, the length becomes three times the length j2 of the trapezoidal prism 3, and the intermediate optical fiber type is disadvantageous in terms of handling and price compared to the reflection type of the present invention. In addition, the intermediate gears 24 and 25 of the speed change gear mechanism 22 are divided into two parts in an overlapping state, and the two divided gears are caused to have a relative rotational deviation due to a spring or the like. gear 24.
25's engagement always hits and no puck rush occurs. Therefore, even if the rotating body 2 rotates in the forward and reverse directions, optical axis misalignment between the input and output optical fibers is prevented, and optical transmission performance can be improved. In the above embodiment, the variable speed gear mechanism ellipse 22 is a combination of spur gears, but a planetary gear mechanism as shown in FIG. 6 may be used to further reduce the size. Next, another embodiment of the present invention will be briefly described.

In Fig. 2, a mirror 32 is installed as a reflector between the trapezoidal prism 3 and the output side optical fiber 5, and the optical fiber 5 is placed at an angle θ (between 0 and 90°) with respect to the parallel optical axis of the trapezoidal prism 3. and a converging lens 9 are arranged to reflect the light beam from the converging lens 9 onto the thousand line optical axis of the trapezoidal prism 3.A mirror is similarly provided on the output surface 3c side of the trapezoidal prism 3.Mirror 32 By providing the trapezoidal prism 3, a large number of optical fibers 5 can be installed even if the aperture S of the trapezoidal prism 3 is small, and the distance between the positive focusing lenses 9 and 10 can be shortened, reducing coupling loss. A prism 33, which is a cone-shaped integrated prism of the long rhombic prism described in the figure, is installed between the trapezoidal prism 3 and the input/output photometric fibers 5, l4. One prism 33 is installed for each optical fiber, but if the prism 33 is used, one prism 33 only needs to be installed no matter how many optical fibers there are, making optical axis adjustment easier and reducing the number of parts. Therefore, it is possible to reduce costs.

In FIG. 4, mirrors 3-4.35 having conical reflective surfaces are arranged at different levels between the optical fiber 5 and the trapezoidal prism 3, and the light from the optical fiber 5 is collimated by the converging lens 9. The first stage mirror 34 reflects the luminous flux inwardly, the second stage mirror 34 reflects the luminous flux inward, and the second stage mirror 35 directs it to the thousand-line optical axis of the trapezoidal prism 3. versus·
and the light flux is made parallel. In this case, it becomes possible to bring the focusing lens 9 close to the open trapezoidal prism, and the length L2 of the entire rotary joint can be shortened. [Effects of the Invention] According to the present invention, there are the following effects. (1) Since a reflector is provided to expand the optical path of the input and output parts of the trapezoidal prism to the outside of the trapezoidal prism's aperture, even a small and short trapezoidal prism can be connected to a multi-core optical fiber using a conventional optical connector. In addition to the short trapezoidal prism, the distance between optical fibers can be shortened, and optical transmission loss can be reduced.

(2) Since the trapezoidal prism is small and short, even if the number of optical fibers increases, the outer diameter and length of the multi-core optical rotary joint will not increase, making it lightweight and compact, and reducing the cost. This makes it possible to reduce friction, improve handling, and increase speed by reducing the gear diameter of the transmission gear mechanism.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of the multi-core optical rotary joint according to the present invention, and FIGS. 2 to 4 show other embodiments of the reflector of the multi-core optical rotary joint of the present invention. A cross-sectional view, FIG. 5 is a diagram showing the relationship between the spacing between focusing lenses and coupling loss, and FIGS. 6 and 7 show a conventional multi-core optical rotary joint! ! This is a cross-sectional view. In the figure, 1 is a fixed body, 2 is a rotating body, 3 is a trapezoidal prism, 14 is a prism holder, 5 is an output side optical fiber, 6 and 13 are ferrules, 9 and 10 are convergent lenses, and 14 is an incident curved optical fiber. , 15.16 is a receptacle, 20.21 is a plug, 22 is a speed change gear mechanism, 28 is a rotating gear, 30.31
is a long rhombic prism, 32 is a mirror, 33 is a prism,
34.35 is a mirror. 7...Fixed body 9,70...Father 5Eλ birth>zu-

Claims (1)

[Claims] 1. A trapezoidal prism is rotatably installed coaxially with the rotating body between the rotating body and the fixed body, and the rotation of the rotating body is transmitted to the trapezoidal prism, and the trapezoidal prism is driven to rotate at 1/2 the angular speed of the rotating body. A variable speed gear mechanism is provided on the entrance and exit surfaces of the trapezoidal prism to reflect light outside the aperture of the trapezoidal prism and guide it to the trapezoidal prism as light within the aperture along the axial direction of the trapezoidal prism. a reflector, a plurality of pairs of converging lenses that are installed on a rotating body and a fixed body so as to optically face the entrance and exit surfaces of the trapezoidal prism through the reflector and optically face each other; A multi-core optical rotary joint with input and output optical fibers coupled to focusing lenses on the input and output sides, respectively.