JPH10186170A - Optical coupling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a structure which has only its focus adjusted and can have the focus adjusted from outside after the assembly and is small-sized and large in thermal capacity by providing a 1st cylinder which is an internal-surface hollow cylinder and coupled with an optical fiber at one end and has 1st and 2nd lenses and a 2nd cylinder wherein an optical detector is fitted. SOLUTION: The optical fiber 1 is inserted into one end of the 1st cylinder 3 and connected. The lenses 1a and 1b are provided in the 1st cylinder 3 and the optical detector 5 is provided in the 2nd cylinder 4. The internal surface of the 2nd cylinder 4 threadably engages the outer peripheral surface of the 1st cylinder 3 so that it can slide, so the lenses 1a and 1b and a photodetecting element 10 can be set on the optical axis and the focal length is easily adjusted to prevent misalignment. The 1st and 2nd cylinders 3 and 4 are made of aluminum and then the structure is made compact. Further, aluminum is large in heat capacity, so the photodetecting element 10 is protected against thermal variation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an optical coupling device for connecting an optical fiber and a photodetector.

[0002]

2. Description of the Related Art A commercially available coupling connector is used for connection between optical fibers, and this is used. However, there is no commercially available connection between an optical fiber and a photodetector. A connecting device in which a collimator, a concentrator, and a photodetector are connected by a light shielding portion as shown in the drawing was prepared and used.
A connection fitting is provided at the end of the optical fiber, and the tip of the optical fiber is inserted into the collimator and coupled. The collimator includes a lens that converts light from the optical fiber into parallel light. The light collector focuses the parallel light on a light receiving element of the photodetector. For this reason, the light collector is moved in the optical axis direction so that the focus can be adjusted. The light-shielding portion blocks the entry of external light and electromagnetic waves that cause noise.

[0003]

In order for the light from the light collector to be focused on the light receiving element, not only the adjustment in the optical axis direction but also the vertical direction in FIG. Adjustment) is also required. That is, three-dimensional adjustment is required. In addition, since the collimator, the light collector, and the photodetector are connected by the light-shielding portion, the overall length becomes longer. Focus adjustment is performed by moving the lens before assembly, and cannot be adjusted after assembly.

The present invention has been made in view of such a problem, and has a structure in which only the focus needs to be adjusted, and further, can be adjusted from the outside after assembly. In addition, the overall size is reduced. It is another object of the present invention to provide a structure made of metal and having a large heat capacity.

[0005]

In order to achieve the above object, according to the first aspect of the present invention, an inner surface of a hollow cylindrical body is connected to an optical fiber at one end, and the light from the optical fiber is converted into parallel light on the inner surface. The first lens and the second
A first cylindrical body having a lens, the outer peripheral surface of which is threaded, and a part of the inner surface of the inner hollow cylindrical body, which is threaded and screwed with the outer peripheral thread portion of the first cylindrical body; The other part is a second cylindrical body fitted with a photodetector for receiving the light condensed by the second lens, and the second cylindrical body is screwed with an outer peripheral thread part of the first cylindrical body. And a lock nut for suppressing the movement of the lock.

[0006] A first lens and a second lens are fixed to the first cylindrical body, and are screwed together with a second cylindrical body to which a photodetector is attached. As described above, the distance between the second lens for condensing light and the photodetector can be easily adjusted after the assembling from the outside since the two lenses are connected by the screw. Further, in order to engage with each other with screws, since all are manufactured symmetrically with respect to the optical axis by machining, there is almost no deviation in a plane orthogonal to the optical axis. Further, by forming the first and second cylindrical bodies with metal, the heat capacity can be increased, and the photodetector is protected from internal and external temperature changes. Further, since the first cylindrical body and the second cylindrical body are used, a compact structure is obtained.

According to the second aspect of the present invention, the first lens is a hollow cylindrical body having one end coupled to the optical fiber at one end, and the first lens for collimating the light from the optical fiber on the inner surface and the first lens for condensing the parallel light. A first cylindrical body having two lenses, and a hollow cylindrical body having an inner surface, a part of the inner surface being fitted to the outer periphery of the first cylinder, and the other part of the inner surface being condensed by the second lens A second cylindrical body fitted with a photodetector for receiving the reflected light, and screwed into a screw hole provided in the second cylindrical body to suppress relative movement between the first cylindrical body and the second cylindrical body. A lock screw.

In the first aspect of the present invention, the first cylindrical body and the second cylindrical body are screwed with each other, but the present invention has a structure of fitting and sliding. This makes it possible to easily adjust the distance between the converging second lens and the photodetector and to assemble it from outside. Other properties are the same as those of the first aspect.

According to the third aspect of the present invention, the photodetector is a second photodetector.
A third cylindrical body fitted to the inner surface of the cylindrical body, and an end plate provided on an end face of the third cylindrical body opposite to the first cylindrical body and having an outer diameter larger than that of the third cylindrical body; The first of the second cylinder
The end surface on the side opposite to the cylindrical body is partially chamfered toward the inside, and an O-ring is provided in a space having a triangular cross section constituted by the outer periphery of the third cylindrical body, the end plate and the chamfer, A pressing plate for pressing the O-ring toward the first cylindrical body via the end plate is attached to the end surface of the second cylindrical body.

The outer shape of the photodetector is cylindrical and is fitted to the inner surface of the second cylindrical body. However, there is a certain gap between the two, which causes a backlash and causes the light receiving element to be slightly deviated from the optical axis. However, the O-ring is provided in a space formed by chamfering the end surface of the second cylindrical body, the outer periphery of the third cylindrical body, and the end plate in a triangular space, and pressing the end plate to press the O-ring so as to crush the light. The displacement of the vessel can be corrected.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view showing the configuration of the embodiment of the present invention. A connection fitting 2 is provided at the end of the optical fiber 1, and the tip is inserted into one end of the first cylindrical body 3 and connected. A collimator lens 7a for converting light from the optical fiber 1 into parallel light is provided inside the first cylindrical body 3.
And a condenser lens 7b for condensing this parallel light on the light receiving element 10 of the photodetector 5 are positioned by the spacer 9 and fixed by the lens holding nut 8. The outer peripheral surface of the first cylindrical body 3 is entirely threaded.

The second cylindrical body 4 has a screw portion 4a at about half of the inner surface on the first cylindrical body 3 side in the optical axis direction, and is screwed with the screw portion 3a on the outer periphery of the first cylindrical body 3. . The remaining part of the inner surface is fitted with the outer surface of the photodetector 5. The optical axis side of the end surface of the second cylinder 4 opposite to the first cylinder 3 is a chamfer 12.
I have. A lock nut 6 is screwed into the thread portion 3a on the outer periphery of the first cylindrical body 3 to fix the relative position of the second cylindrical body 4 whose focus adjustment has been completed with respect to the first cylindrical body 3. The photodetector 5 includes a third cylindrical body 5a fitted to the inner surface of the second cylindrical body 4, and an outer surface provided on an end surface of the third cylindrical body 5a opposite to the first cylindrical body 3 and larger than the third cylindrical body 5a. And an end plate 5b having a diameter. The light receiving element 10 having a center line on the optical axis in the third cylindrical body 5a is attached to the end plate 5b. Light receiving element 10
Has a cylindrical shape, and the focal length is adjusted by rotating the second cylindrical body 4 with respect to the first cylindrical body 3 so that the light from the condenser lens 7b is contained within this cylindrical diameter as the light receiving surface.

An O-ring 13 is provided in a space having a triangular cross section constituted by the outer periphery of the third cylindrical body 5a, the surface of the end plate 5b on the first cylindrical body 3 side, and the chamfer 12, and the O-ring 13 is provided through the end plate 5b. A pressing plate 14 for pressing the ring 13 toward the first cylindrical body 3 is attached to the second cylindrical body end face 4b with a set screw 14a. The holding plate 14 is tightened with the set screw 14a so that the surface of the end plate 5a opposite to the first cylindrical body 3 and the end surface 4b of the second cylindrical body are the same. The diameter of the cross section of the O-ring 13 is large enough to be contracted and contracted. Outer circumference of third cylindrical body 5a and second cylindrical body 4
However, there is a certain amount of clearance between the two 5a and 4 and backlash occurs, and the light receiving element 10 slightly shifts with respect to the optical axis. However, the O-ring 13 is provided in the space having the triangular cross-section, and the O-ring 13 is pressed toward the first cylindrical body 3 via the end plate 5b, whereby the photodetector 5
Of the light receiving element 10 can be corrected.

The relationship between the diameter of the light receiving element 10 and the diameter of the optical fiber 1 satisfies the following relational expressions (1) to (3). This will be described with reference to FIG. The end face of the optical fiber 1 is the focal length fa of the collimator lens 7a.
(Distance from the principal point Ha), the light emitted from the optical fiber 1 is adjusted to be parallel light after passing through the collimator lens 7a. Assuming that the focal length of the condenser lens 7b is fb (distance from the principal point Hb), the combined focal length fr of the optical system composed of the collimator lens 7a and the condenser lens 7b is as follows.

Fr = fa × fb / (fa + fb) (1) Assuming that the diameter of the optical fiber 1 is Da, the diameter Db of the image formed at the focal position of the condenser lens 7b is expressed by the following equation. You. Db / Da = (fb−fr) / (fa−fr) (2) When the diameter of the light receiving element 10 is Dc, the optical coupling between the optical fiber 1 and the light receiving element 10 is efficiently performed. Must satisfy the following equation. Dc ≧ Db (3) When the focal lengths of the collimator lens 7a and the condenser lens 7b are selected so as to satisfy the above equations (1) to (3), it is possible to correspond to any diameter of the light receiving element 10.

Next, a second embodiment will be described. FIG. 2 shows the second
It is a longitudinal section showing the composition of an embodiment. In the first embodiment, the connection between the outer peripheral surface of the first cylindrical body 3 and the inner surface of the second cylindrical body 4 is a screw. However, in the second embodiment, the fitting and sliding are performed. Condensing lens 7
The focus is adjusted by adjusting the distance between b and the light receiving element 10. Further, the lock cylinder 6 is replaced with the second cylindrical body 4.
The first cylindrical body 3 and the second cylindrical body 4 are fixed by a lock screw 15 in the radial direction. Other than the above, it is the same as the first embodiment.

[0017]

As is apparent from the above description, the present invention provides a lens in the first cylinder, a photodetector in the second cylinder, and a second cylinder on the outer peripheral surface of the first cylinder. Since the inner surface is screwed or slidably fitted, the lens and the light receiving element can be set on the optical axis, the focal length can be easily adjusted, and misalignment can be prevented. In addition, since the first cylinder and the second cylinder are made of a metal such as aluminum or brass, a compact structure is obtained, and a light shielding and electromagnetic shielding performance is provided, thereby preventing noise. Further, aluminum and brass have high thermal conductivity and large heat capacity, so that the light receiving element can be protected against internal and external heat fluctuations. This enables stable optical reception.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a configuration of a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing a configuration of a second embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a relationship between a diameter of an optical fiber and a diameter of a light receiving element.

FIG. 4 is a structural view of a conventional coupling connector for connecting an optical fiber and a photodetector.

[Explanation of symbols]

 Reference Signs List 1 optical fiber 2 connection fitting 3 first cylindrical body 4 second cylindrical body 4b second cylindrical body end face 5 photodetector 5a third cylindrical body 5b end plate 6 lock nut 7a collimator lens (first lens) 7b condenser lens ( 2nd lens) 8 lens holder 9 spacer 10 light receiving element 11 wire 12 chamfer 13 O-ring 14 holding plate 14a set screw 15 lock screw

Claims (3)

[Claims] An inner hollow cylindrical body coupled to an optical fiber at one end, and a first lens for collimating the light from the optical fiber and a second lens for condensing the parallel light on the inner surface. A first cylindrical body having an outer peripheral surface threaded, and an inner hollow cylindrical body having a part of an inner surface threaded and screwed with an outer peripheral thread portion of the first cylindrical body, and another part of the inner surface. Is screwed with a second cylindrical body in which a photodetector for receiving light collected by the second lens is fitted, and with an outer peripheral thread portion of the first cylindrical body to move the second cylindrical body. An optical coupling device, comprising: a lock nut for pressing. 2. A first lens having a hollow inner surface, which is coupled to an optical fiber at one end, and a first lens for collimating light from the optical fiber on an inner surface and a second lens for condensing the parallel light. A first cylindrical body having a hollow cylindrical inner surface, a part of the inner surface being fitted to the outer periphery of the first cylindrical body, and the other part of the inner surface receiving light collected by the second lens. A second cylindrical body in which a light detector to be fitted is fitted, and a lock screw that is screwed into a screw hole provided in the second cylindrical body to suppress relative movement between the first cylindrical body and the second cylindrical body. An optical coupling device, comprising: 3. The photodetector according to claim 1, wherein the third cylinder is fitted on the inner surface of the second cylinder, and the photodetector is provided on an end surface of the third cylinder opposite to the first cylinder, and is larger than the third cylinder. An end plate having an outer diameter, an end face of the second cylinder opposite to the first cylinder is partially chamfered inward, and an outer periphery of the third cylinder and the end An O-ring is provided in a space having a triangular cross section constituted by a plate and the chamfer, and a holding plate for pressing the O-ring toward the first cylinder through the end plate is attached to an end surface of the second cylinder. 3. A method according to claim 1, wherein
The optical coupling device as described in the above.