JPH0792536B2 - Rotating optical coupler - Google Patents

Description

Description: TECHNICAL FIELD The present invention generally relates to an optical coupler that couples at least a pair of optical transmission media at their ends, and in particular, the optical couplers are arranged so as to face each other. At least one of the media forming the optical axis is rotated about a predetermined axis with respect to the other, and the relative angular relationship between the two is changed to optically couple at least a pair of optical transmission media. is there.

2. Description of the Related Art A rotary type optical coupler that optically couples a pair of optical fibers, in which one of the pair of optical fibers rotates around its longitudinal axis with respect to the other, is known. A typical conventional rotary optical coupler is shown schematically in FIG. 1, which, as shown, comprises a pair of first and second optical fibers 1a and 1a 'and a pair of first optical fibers.
And second 1/4 pitch gradient index rods 2a and 2a '. These 1/4 pitch gradient index rods are commercially available under the trade name "SELFOC" lenses and are also referred to as graded index rods. In a "selfoc" lens, the index of refraction varies from the center of the rod to the perimeter, and in particular the index decreases from the center to the perimeter to focus the light. In the configuration shown in FIG.
One end of the first optical fiber 1a is bonded to one end of the first 1/4 pitch gradient index rod 2a, and similarly, one end of the second optical fiber 1a is second
Is attached to one end of a 1/4 pitch gradient index rod 2a '.

Therefore, in the case of the rotary type optical coupler configured as shown in FIG. 1, the light directed from the first optical fiber 1a into the first 1/4 pitch gradient index rod 2a is the first rod. Collimated (parallel) emitted from 2a. The light thus collimated is then directed into a second 1/4 pitch gradient index rod 2a ', where it is directed to a rod 2a' having a second optical fiber 1a 'bonded thereto. The light is refocused as it approaches the end face, and the light thus refocused enters the second optical fiber 1a '. Due to the reversibility of light, it is also possible to transmit light from the second optical fiber 1a 'to the first optical fiber 1a. Thus, a pair of spaced optical fibers 1
Optical information can be transmitted between a and 1a '.

In the configuration shown in FIG. 1, the transmitted light is 1/4
When ejected from either of the pitch gradient index rods 2a and 2a ', it is collimated,
It is possible to rotate either or both of the gradient index rods 2a and 2a 'about their respective longitudinal axes. For example, it is possible to rotate the other rod 2a around its longitudinal axis while keeping the rod 2a 'fixed. Even in such a case, it is possible to transmit light between the two optical fibers 1a and 1a '. However, the configuration shown in FIG. 1 only allows a pair of optical fibers 1a and 1a 'to be coupled, and therefore its use and application are limited.

Aim The present invention mainly aims to solve the above-mentioned drawbacks of the prior art and to provide an improved rotary optical coupler. Another object of the present invention is to provide a rotary optical coupler which can couple a relatively large number of pairs of optical fibers and which can be manufactured easily and accurately. Yet another object of the present invention is to provide a multi-fiber (multi-core) rotary optical coupler having a simple structure. Still another object of the present invention is to provide a rotary type optical coupler whose coupling state can be easily adjusted. Still another object of the present invention is to provide a rotary optical coupler which is compact in structure, robust, and operationally reliable.

Structure FIG. 2 schematically shows a telemetry system to which the present invention can be preferably applied. As shown, a perforation 15 is bored from the ground surface 14 into the ground, and a casing 16 is inserted into the perforation 15. A measurement probe 17 is fixed to one end of a multi-fiber cable 13b composed of a plurality of optical fibers, and the probe 17 is arranged in the hole 15 so that the probe 17 can be moved up and down. ing.
The multi-fiber cable 13b is wound around the drum 12 of the winch 10 placed on the ground surface 14, and the other end of the rotary optical coupler 6 is constructed according to one embodiment of the present invention. It is connected to one end. The coupler 6 includes a bearing 5
At the same time, it also functions as a bearing for rotatably supporting the drum 12. Therefore, when the drum 12 is driven and rotated in the clockwise direction or the counterclockwise direction, the cable 13b is wound on or unwound from the drum 12, and the perforation 15 is formed.
The measurement probe 17 rises and falls inside.

The other end of the rotary optical coupler 6 is connected to another multi-fiber cable 13a, and the cable 13a is also composed of a plurality of optical fibers.
Has been extended to. The data processing device 18 typically comprises a computer for processing the data collected by the measuring probe 17. As will be understood, in such an application example, the rotary type optical coupler 6 is provided and the pair of multi-fab cables 13a and 13b are optically jointed or connected in a relationship in which their ends face each other. Have been established.
The multi-fiber cable 13a is connected to the stationary side of the rotary optical coupler 6, while the other cable 13b is connected to the drum 1
It is connected to the rotating side of a coupler 6 which rotates with 2.

In such a telemetry system, it is most desirable that the rotary optical coupler 6 be capable of coupling a relatively large number of pairs of optical fibers and capable of transmitting a large number of optical signals. Further, the rotary optical coupler 6
Are required to be highly reliable in operation and easy to install, maintain and adjust. In particular,
It is most desirable that the coupling efficiency can be adjusted easily and with high accuracy.

FIG. 3 schematically shows a multi-fiber rotary optical coupler 20 constructed according to the first embodiment of the present invention. The configuration of FIG. 3 is further shown in perspective view in FIG. As shown in the figure, the combiner 20 is generally composed of three parts, namely, the first collimator / focusing part 20a.
And an image rotation unit 20b and a second collimator / focusing unit 20c. In the configuration shown in FIG. 3, the first and second collimator / focusing parts 20a and 20c are symmetrical in structure, so that the corresponding elements in the second collimator / focusing part 20c are indicated by a dash. It is indicated by a number. A plurality of first collimator / focusing units 20a (4 in the illustrated example)
) With approximately 1/4 pitch gradient index rods 21a to 21d, which are arranged symmetrically around a first predetermined central axis, each of which faces toward FIG. It functions as a collimator lens for collimating light when light passes from left to right, and as a focusing lens when light passes in the opposite direction. Furthermore,
Four first optical fibers 23a to 23d are provided, which are rods via connectors 22a to 22d, respectively.
Operationally connected to 21a-21d. In the preferred embodiment, each optical fiber connector 22a through 22d comprises a stainless steel or ceramic tube and an epoxy resin filled with a corresponding optical fiber partially extending within the tube. The corresponding optical fiber is embedded in the epoxy resin and its tip is located at the center of the end face of the connector. These connectors 22a to 22d are preferably of identical construction and of the same diameter as the first rods 21a to 21d. Therefore, these connectors 22a-2
2d is simply arranged in such a manner that the ends of the 2d and the corresponding first rods 21a to 21d face each other.
It is possible to optically couple 23a to 23d with the corresponding first rods 21a to 21d. The optical fibers 23a to 23d extending from the connectors 22a to 22d are bundled to form a first multi-fiber cable 23.

As can be readily seen from FIG. 3, the second collimator and focus section 20c is similarly constructed, that is, it has four second approximately 1/4 pitch gradient index rods 21a'-21d. ', Which are the first rod 21
The patterns corresponding to a to 21d are arranged symmetrically with respect to the second predetermined central axis. Each of the optical fiber connectors 22a 'to 22d' is connected to one of the four second optical fibers 23a 'to 23d', and the ends thereof are opposed to the corresponding second rods 21a 'to 21d'. They are arranged adjacent to each other. Second optical fiber
23a 'to 23d' are also bundled to form a second multi-fiber cable 23 '. It should be understood that the second 1/4 pitch gradient index rod 21a '
Reference numerals 21 to 21d 'function as a collimator lens for light passing from right to left and a focusing lens for light passing from left to right. Although the optical fiber connector 22 is used in the configurations shown in FIGS. 3 and 4, the optical fiber 23 can be directly bonded to the corresponding rod 21 if desired. One of the important features of the configuration shown in FIGS. 3 and 4 is that in this embodiment, each of the 1/4 pitch gradient index rods 21 arranged axially symmetrically with respect to a predetermined center line is provided. On the other hand, one optical fiber 23 is provided.

In the embodiment shown in FIGS. 3 and 4, the image rotator 20b includes a dove prism 24. As shown schematically in Figures 5a and 5c, the dove prism 24 has unique optical properties that, when it is rotated about its major axis, i.e., the axis parallel to its longitudinal sides, The image rotates at twice the angular frequency of the rotation of prism 24. For example, 5b
As shown, when the dove prism 24 is rotated 45 degrees, the letter "F" is rotated 90 degrees. The image forming characteristic of the dove prism 24 is shown in FIG. 5a, and after the light image from the erect "F" enters the entrance surface 24a and is reflected by the reflecting surface 24c,
It is ejected from the ejection surface 24b to form an inverted image. This inverted image is kept unchanged even if the light image input into the dove prism 24 is rotated, as long as the dove prism 24 is rotated at an angular frequency that is half the rotation of the original image. It should be noted that due to the reversibility of light, the entrance and exit surfaces
It is possible to exchange 24a and 24b.

Therefore, in the configuration shown in FIG. 3 and FIG. 4, since the dove prism 24 is used as the image rotation unit 20b, the angular frequencies of the portions 20a, 20b, 20c are ω ₁ , ω ₂ , ω. _Three
Then, in order to maintain an operational relationship between the corresponding first and second 1/4 pitch gradient index rods, eg 21a and 21d ′, ω ₂ = (ω ₁
We must keep the relationship of + ω ₃ ) / 2. In the present embodiment, the first center line defined in the centers of the four first 1/4 pitch gradient index rods 21a to 21d passes through the center of the Dove prism, and the center lines are The second 1/4 pitch gradient index rods 21a 'to 21d' are defined by the second
Aligned with the centerline. Therefore, ω ₂ = (ω ₁ + ω ₃ )
As long as the three parts 20a, 20b, 20c are rotated in the same or opposite directions while maintaining the / 2 relationship, the operational relationship between the corresponding first and second rods, eg 21a and 21d '. Therefore, even if the relative positional relationship between the first and second rods changes due to rotation at different angular frequencies, the four first quarter pitches can be maintained. Specific one of gradient index rods 21a-21d
One of the four second 1/4 pitch gradient index rods 21a 'to 21d', e.g. Can be transmitted to.

It should be noted that the three parts 20a, 20b, 20c
It is possible to hold any one of them in a non-rotating state. In other words, it is possible to set any one of ω ₁ , ω ₂ , and ω ₃ to zero. For example, it is possible to set ω ₃ to zero, in which case the second portion 20c having the second 1/4 pitch gradient index rods 21a 'to 21d' is kept stationary or non-rotating. . This is because the rotary optical coupler 20 shown in FIGS.
2 is applied to the telemetry system shown in FIG. 2, in which case cables 23 and 23 'are respectively connected to cable 13
Corresponds to b and 13a.

The configurations shown in FIGS. 3 and 4 are particularly suitable for manufacturing because only a single optical fiber 23 is connected to the corresponding 1/4 pitch gradient index rod 21. It is possible to replace the four first 1/4 pitch gradient index rods 21a to 21d with a single 1/4 pitch gradient index rod, but in this case, a plurality of optical fibers are used. It is difficult to connect to one end face of a single rod with high accuracy. In the present invention, a plurality of 1/4 pitch gradient index rods are provided in axial symmetry with respect to a predetermined center line to define the collimator / focusing unit, and the plurality of optical Since the fibers are individually connected to the corresponding rods, such difficulties are not encountered. And, the advantage of this feature is significantly enhanced by using an adapter that holds the collimator and focusing elements in the particular pattern desired, as described below.

FIG. 6 shows another embodiment of the present invention, which is ω ₂
It has a unique differential gear mechanism for maintaining a predetermined angular frequency relationship of = (ω ₁ + ω ₃ ) / 2. Referring to FIG. 6, the illustrated rotary optical coupler has a first sleeve 30 having a flange 30a and an outer casing.
31 is fixed to the flange 30a. Outer casing 31
Is rotatably connected via a ball bearing 32 to a second sleeve 33 aligned with the first sleeve 30. A first bevel gear 34, which has a substantially ring shape and is rotatable coaxially with the sleeve 30, is fixed to the flange 30a by bolts. Similarly, a ring-shaped second bevel gear 37 is fixed to the flange 33 a of the second sleeve 33.

Further provided is a spider shaft 36 having a sleeve portion 36a and a pair of protruding portions 36b, 36b, the protruding portions 36b, 36b projecting radially from the center of the sleeve portion 36a in opposite directions. The spider shaft 36 is arranged with its rotation axis aligned with the rotation axis of each of the first and second sleeves 30 and 33, and has four ball bearings 38a to 38a.
It is rotatably supported by bevel gears 34 and 37 which are arranged to face each other via 8d. Also, a pair of ball bearings 39a and 39a
A pinion 35a is provided rotatably supported around one of the protruding portions 36b via 9b. Another pinion 35b is rotatably provided around the other protruding portion 36b via another pair of ball bearings 39c and 39d. These pinions 35a and 35b are sandwiched between the bevel gears 34 and 37 and mesh with them.

A sectional structure taken along line VI-VI in FIG. 6 is shown in FIG. As can be easily understood from FIG. 8, the bevel gear 37
The relative angular relationship between the spider shaft 36 and the bevel gear 37 changes via the meshing between the pinion 35a and the pinion 35b. Thus, the pair of bevel gears 34 and 37 arranged to face each other and the pinions 35a and 35b that are held and meshed between the bevel gears 34 and 37 constitute a differential gear mechanism. Therefore, it is possible to rotate the sleeves 30 and 33 and the spider shaft 36 in a predetermined angular frequency relationship as described above. Unlike the reduction gear system, in such a differential gear system, the number of teeth provided on each gear and pinion has nothing to do with the relative rotational speed between the gears. That is, in the differential gear system, the speed of the main drive member becomes equal to the algebraic average value of the rotation speeds of the two rotary shafts.

The dove prism 24 is housed within the sleeve portion 36a of the spider shaft 36 and thus rotates integrally with the spider shaft 36. In the preferred embodiment, the dove prism 24 includes a sleeve portion 36, as described below.
It is provided so that the position can be adjusted in a. The first collimator / focusing unit, for example, the first portion 20a and the first sleeve 30 shown in FIG. Similarly, the second collimator
A focusing unit, for example the second part 20c shown in FIG. 3, can be fixedly provided in the second sleeve 33. Therefore, when the first and second sleeves 30 and 33 are driven and rotated at the angular frequencies ω ₁ and ω ₃ around their respective rotation axes in the same or opposite directions, the bevel gears 34 and 37 are also driven and rotated at the respective angular frequencies. Then, the spider shaft 36 and thus the dove prism 24 are rotated at a predetermined angular frequency, that is, ω ₂ = (ω ₁ + ω ₃ ) / 2, via the pinions 35a and 35b. This can be easily understood because the differential gear mechanism is used in this embodiment.

In such a structure, a plurality of first optical fibers connected to the first collimator / focusing unit inserted in the first sleeve 30 are inserted into the second collimator It is possible to optically couple a plurality of second optical fibers connected to the focusing unit, in which case the corresponding first and second optical fibers
It is possible to maintain an operational relationship between optical fibers. Therefore, the second collimator mounted in the second sleeve 33 under the condition that the first sleeve is in the non-rotating state and the second sleeve 33 is in the rotating state.
The optical image from the focusing unit is first transmitted through the Dove prism 24.
When transmitted to the mounted first collimator / focus unit in the sleeve 30, the optical image transmitted to the first collimator / focus unit in the first sleeve 30 has a second collimator / focus unit. Even if it is rotating when it is ejected from the unit, it does not rotate and maintains the same directionality.

FIG. 7 shows an example of a structure for attaching the collimator / focusing unit when the collimator / focusing unit 20c shown in FIG. 3 is applied to the rotary type optical coupler of FIG.
As shown, this mounting structure has an adapter 40, which has a generally cylindrical shape.
40 has a cylindrical portion 41, which is a sleeve
Can be inserted tightly in 33 and is arranged axially symmetrically about its central axis and extends in the longitudinal direction 4
Individual through holes 42a to 42d are formed. Further, the adapter 40 is a flange portion formed at one end of the cylindrical portion 41.
Has 43. Therefore, the adapter 40 has the second sleeve 33 until its flange portion 43 abuts against the end of the second sleeve 33.
It is possible to set it at a predetermined position by inserting it into 33. As shown in FIG. 7, the 1/4 pitch gradient index rods 21a 'to 21d' are fixedly mounted in the through holes 42a to 42d, respectively, and the optical fiber connectors 22a 'to 22d' are also penetrated. Fixedly mounted in holes 42a to 42d, with the respective end faces having the tips of the corresponding optical fibers 23a 'to 23d' as indicated by the black dots being associated with a 1/4 pitch gradient index rod 21a '. To 21d '. Therefore, when assembled, a collimator / focus unit in which the four optical fibers 23a 'to 23d' are connected is formed. To complete this rotary optical coupler,
Firstly, another collimator / focusing unit having the same configuration is used.
It is necessary to be fixedly inserted and provided in the sleeve 30.

When assembling, the adapter 40 having the 1/4 pitch gradient index rod and the optical fiber connector inserted into the mounting holes 42a to 42d is inserted into the sleeve 30, and another adapter 40 is inserted into the other sleeve 33. Let Then the adapter by any fixing means
One of the 40 40 is fixed to the corresponding sleeve by, for example, a bolt or an adhesive, and then the other adapter 40 is rotated in the corresponding sleeve, and the corresponding 1/4 pitch gradient index rod is arranged. Get the angular correspondence between. Next, the other adapter 40 is fixed to the corresponding sleeve with, for example, a bolt or an adhesive.

However, it should be noted that the rotary optical coupler shown in FIG. 6 can be used with a collimator / focus unit of a type other than that shown in FIG. Furthermore, it is possible to provide any number of optical fibers 23 connected to the unit shown in FIG.
FIG. 9 shows another embodiment, in this case eight 1 /
4 pitch gradient index rod 50a to 50h
Are arranged, for example, in a circular shape to form a collimator / focusing unit, and eight optical fibers 52a are formed.
Through 52h are operatively connected through optical fiber connectors 51a through 51h. In this way, multiple 1/4
It is also possible to bond the pitch gradient index rods integrally in a desired arrangement and insert them into the first or second sleeve 30 or 33.

Referring now to FIGS. 10 and 11, in this embodiment, the sleeve portion 36 of the spider shaft 36 is
A structure for adjusting the position of the dove prism 24 in a is provided, and this structure can be suitably applied to the rotary optical coupler shown in FIG. Sleeve part 36
The adjusting structure for adjusting the position of the dove prism 24 in a includes a set screw 55 screwed into a screw hole 52 formed in the sleeve portion 36a extending in the radial direction, and a dove prism. Dove prism to push 24 against set screw 55
An urging spring 58 is provided so as to be interposed between 24 and the sleeve portion 36a. As shown in FIG. 11, in the preferred embodiment, two setscrews 55 and 56 are provided remote from each other in the longitudinal direction of the dove prism 24. In this configuration, by rotating the set screws 55 and 56 as appropriate, the reflective surface 24c of the dove prism 24 is
Dove prism in sleeve part in a direction perpendicular to
It is possible to adjust 24 positions. Since it is not necessary to adjust the position of the dove prism 24 in the direction parallel to the surface 24c,
Only the adjustments described above are necessary to align with the center or axis of rotation of 33. Preferably, after the adjustment is completed, the dove prism 24 is filled by at least partially filling the gap between the dove prism 24 and the sleeve 36a with an adhesive, for example, except for a region through which light carrying information passes. It is fixed to the sleeve 36a.

Effect As described above in detail, according to the present invention, a rotary type optical coupler having a simple structure and easy to manufacture, which is capable of optically coupling a pair of optical fibers at the same time, is provided. An optical coupler is provided. In particular, one of the
According to the embodiment, one collimator / focusing element, which is usually composed of a 1/4 pitch gradient index rod, is provided for one optical fiber, so that the connection between these elements is made. It is possible to establish with certainty. Further, by using the unique differential gear mechanism, it is possible to effectively transmit the driving force to the movable portion of the present coupler, and it is possible to reduce the overall configuration. The shape can be symmetrical and this latter effect is particularly beneficial for mounting the present rotary optocoupler to a support structure. Further, by providing an adjusting mechanism, it is possible to properly adjust the image rotating prism, which is typically a dove prism, to position the image rotating prism at an optimum position, and as a result, it is possible to cause misalignment. With some coupling loss.

The present invention should not be limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the technical scope of the present invention described in the claims.

[Brief description of drawings]

FIG. 1 is a schematic view showing a typical conventional rotary type optical coupler, and FIG. 2 is a schematic view showing a telemetry system having a winch 10 to which the present rotary type optical coupler can be suitably applied. 3 and 4 are schematic views showing a rotary type optical coupler constructed according to one embodiment of the present invention, and FIG. 4 is a schematic perspective view of the configuration of FIG. 3 when viewed in a perspective direction, 5a and 5b are schematic perspective views useful for explaining the function of the dove prism 24, and FIG. 6 is a detailed view of a rotary optical coupler equipped with a unique differential gear mechanism embodying the present invention. FIG. 7 is a schematic perspective view showing a collimator / focusing unit which can be effectively used in the structure shown in FIG. 6, and FIG. 8 is shown in FIG. A cross-sectional view taken along line VI-VI, FIG. 9 is a schematic perspective view showing another embodiment of the collimator / focusing unit, and FIG. 10 is An enlarged cross-sectional view showing a mechanism for adjusting the position of the dove prism 24 with respect to a constant rotation axis, FIG. 11 is a vertical cross-sectional view showing a preferred embodiment of the mechanism for adjusting the position of the dove prism 24, Is. (Description of symbols) 21: 1/4 pitch gradient index rod 22: Optical fiber connector 23: Optical fiber 24: Dove prism 30, 33: Sleeve 34, 37: Bevel gear 35a, 35b: Pinion 36: Spider shaft 40: Adapter 55, 56: Set screw 58: Spring

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-59-105608 (JP, A) JP-A-60-164707 (JP, A) Actually opened 59-33014 (JP, U)

Claims (10)

[Claims] 1. A rotary optical coupler for optically coupling at least a pair of light transmission media, wherein first holding means holds a first collimator / focus unit connectable to at least one first light transmission medium. At least 1
Second holding means for holding a second collimator / focusing unit connectable to the two second light transmission media, wherein the second holding means includes the second collimator / focusing unit for the first collimator / focusing unit. The focusing unit is opposed to the focusing unit, is spaced apart from the focusing unit, is held in alignment with a common rotation axis, and is supported rotatably around the common rotation axis relative to the first holding means, and is aligned with the common rotation axis. In addition, a third holding means for holding the image rotating means is provided between the first and second collimator / focusing units, and is operated between the first, second and third holding means. A differential gear mechanism is provided which is connected and is configured to maintain a relationship in which the rotation speed of the third holding means is equal to the algebraic average value of the rotation speeds of the first and second holding means, The third holding hand Has a sleeve portion for holding the image rotating means and at least two protruding portions radially protruding from the sleeve portion, and the differential gear mechanism is fixed to the first holding means. 1 bevel gear, a second bevel gear fixed to the second holding means, and at least two pinions rotatably supported by the protruding portion, respectively, the pinion being the first and second umbrellas. A rotary optical coupler characterized by being meshed between gears. 2. The method according to claim 1, wherein
And a second holding means, and a casing is provided surrounding the third holding means and the differential gear mechanism, and the casing is fixed to one of the first and second holding means. In addition, the rotary optical coupler is characterized in that it is rotatably coupled to the other of the first and second holding means via a rotary bearing. 3. The image rotating means according to claim 2, wherein the image rotating means has a dove prism housed in the sleeve portion, and the angular frequencies of the first, second and third holding means are respectively set. When ω ₁ , ω ₂ , and ω ₃ , the first and second
And at least two of the third holding means are ω ₂ = (ω ₁ + ω
₃ ) A rotating optical coupler characterized by rotating while maintaining the relationship of 2) / 2. 4. The device according to claim 3, wherein each of the first and second holding means has a sleeve, and each of the first and second collimator / focusing units is inserted into a corresponding sleeve. And an adapter having a plurality of mounting holes, and a plurality of collimator / focusing elements respectively connectable to the plurality of optical fibers inserted in the mounting holes. Rotating optical coupler. 5. The rotary optical coupler according to claim 4, wherein the mounting hole is a through hole extending from one end to the other end of the adapter. 6. The adapter according to claim 4, wherein the adapter is formed on a tubular portion that can be inserted into the sleeve and one end of the tubular portion, and engages with one end of the sleeve. A rotary optical coupler having a flange portion for setting an adapter at a predetermined position. 7. The third aspect of the present invention according to claim 1
A rotary optical coupler, wherein the holding means is provided with adjusting means for adjusting the position of the image rotating means with respect to the common rotation axis. 8. The third aspect according to claim 7
The holding means has a sleeve portion, and the image rotating means is a dove prism housed in the sleeve portion, and the adjusting means is screwed into a screw hole formed in the sleeve portion in a radial direction. At least one set screw and biasing means arranged between the inner wall of the sleeve portion and the dove prism for biasing the dove prism with respect to the at least one set screw, A rotary optical coupler, wherein the position of the dove prism is adjusted with respect to the common rotation axis by rotating the at least one set screw. 9. The set screw according to claim 8, wherein the set screw is provided in each screw hole formed in the sleeve portion in a radial direction and spaced from each other in a longitudinal axis direction of the sleeve portion. 2. A rotary optical coupler, wherein two bottoms of the two are engaged with a dove prism pressed by the bias means. 10. The rotary optical coupler according to claim 8, wherein the bias means is a spring.