JPH1026510A - Method for detecting position of optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the position of an optical fiber ion both the x- and y-axis directions by observing the optical fiber while the optical fiber is irradiated with light from one direction. SOLUTION: An optical fiber 1 is irradiated with elongated line light in the x-axis direction toward the fiber 1 from the y-axis direction so that the non-spot shaped image of the line light transmitted through the optical fiber 1 and the linear image of the line light transmitted through the outside of the optical fiber 1 can be formed on an image sensor installed to one side of the fiber 1 opposite to the light source. The position of the optical fiber 1 in both the y- and x-axis direction is detected from a picture obtained by means of the image sensor by detecting the formed images.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting the position of an optical fiber, which is used for aligning the optical fiber at the time of fusion splicing, or detecting the deviation of the optical fiber after fusion splicing. Things.

[0002]

2. Description of the Related Art The principle of a conventional optical fiber position detecting method is shown in FIGS. The optical fiber is formed by covering the periphery of the core with a clad. In the case of a single mode optical fiber, for example, as shown in FIG. About 0.
It has a relative refractive index difference of 3%. As shown in FIG. 12, when the optical fiber 1 is irradiated with parallel light from the side (right side in the drawing), the optical fiber 1 itself becomes a cylindrical lens, and light passing through the optical fiber 1 due to a difference in refractive index is directed toward the center. And light rays are formed in a coarse part, a dense part and other parts, and a contrast is generated. As a result, an image as shown on the left side of FIG. 12 is obtained on the focal plane. When the luminance level of this image is measured along the measurement line, a curve as shown in FIG. 13 is obtained. If the boundary between the clad 1b and air or the boundary between the core 1a and the clad 1b is detected using this curve (or the image in FIG. 12) as the original data, the position of the optical fiber can be detected.

[0003]

In order to align the optical fibers by this method, as shown in FIG. 14, two directions (x-axis) orthogonal to the axes (z-axis) of the optical fibers 1A and 1B are used.
(Axis, y-axis). In order to realize this by the conventional method, it was necessary to perform observation from two directions. Therefore, in addition to the mechanism for holding the left and right optical fibers 1A and 1B, the apparatus includes light sources 2X and 2Y for observing from two directions, and microscopes 3X and 3X.
It is necessary to arrange the Y, the image sensors 4X, 4Y, and the like with high accuracy, and it is extremely difficult to design and manufacture.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for detecting the position of an optical fiber on the x-axis and y-axis by observing from one direction, in view of the above problems. .

[0005]

First, the concept underlying the present invention will be described. As is clear from FIG. 12, the optical fiber becomes a cylindrical lens when viewed from a direction perpendicular to the axis. Cylindrical lenses have astigmatism when illuminated from a direction perpendicular to their axes, and when combined with a convergent lens, produce two mutually perpendicular line foci.

This point will be described below with reference to FIGS. 1 and 2. That is, as shown in FIG. 1, a light source 2 and a converging lens 3 irradiate a spot light on an optical fiber 1 in a direction orthogonal to the axis thereof, and an optical image generated by the light source 2 is captured by a CCD image sensor installed on the opposite side. 5 shall be observed. Then, the optical fiber 1
As a result, the optical image generated on the image sensor 5 becomes an astigmatic image as shown in FIG.
Its shape is changed as follows between the two foci P ₁ to P _2.

At the focal point P ₁ closer to the optical fiber 1, the optical fiber 1
The same direction of the fine line S ₄ and. The direction of the fine line S ₃ perpendicular to the focus P ₂ In the optical fiber 1 is further from the optical fiber 1. A circular S ₀ in the middle P ₁ and P _2. Long ellipse S ₂ to S ₄ direction between the P ₁ to the intermediate
Becomes Ellipse S ₁ long in the S ₃ direction from the middle to P ₂
Becomes

Therefore, as shown in FIGS. 3A to 3C,
Assuming that the positions of the converging lens 3 and the image sensor 5 (imaging plane) are fixed and the position of the optical fiber 1 changes between them, the shape of the image captured by the image sensor 5 is examined. From the optical fiber 1 can be detected.

For example, assuming that the position of the optical fiber 1 when the image formed on the image sensor 5 has a circular shape S ₀ as shown in FIG. 2A is the origin, the optical fiber 1 is moved from the origin as shown in FIG. If the image is shifted toward the image on the image sensor 5 becomes long ellipse S ₂ in the direction of the optical fiber 1. Also, as shown in FIG.
If the image is shifted toward the image on the image sensor 5 becomes long ellipse S ₁ in the direction perpendicular to the optical fiber 1. Therefore, the presence or absence of a shift of the optical fiber 1 and the direction of the shift, if any, can be known from the shape of the image detected by the image sensor 5. Here, l ₀ , l ₁ , and l ₂ indicate the distances between the optical fiber 1 and the image sensor 5, and l ₁ >
The relationship is l ₀ > l ₂ . L is a convergent lens 3
4 shows the distance between the image sensor 5 and the image sensor 5.

In the present invention, as shown in FIG. 5, the axial direction of the optical fiber is the z axis, and one direction perpendicular to the z axis is the y axis.
The direction perpendicular to the axis, the z-axis and the y-axis is defined as the x-axis, and when light is irradiated from the y-axis direction toward the optical fiber 1, a long line light is used in the x-axis direction. When such a line light is used, a portion where the line light is blocked by the optical fiber forms an astigmatic image, and a portion where the line light is not blocked forms a linear image. Therefore, the position of the optical fiber in the y-axis direction can be determined from the shape of the astigmatic image, and the position of the optical fiber in the x-axis direction can be determined from the position of the break in the linear image. In FIG. 5, P ₃ is the focal line of the line light passing above the optical fiber 1, and P ₃ ′ is the focal line of the line light passing below the optical fiber 1. The use of line light has the following advantages over the use of spot light. That is, in the case of spot light, it is necessary to adjust the optical axis so as to pass through the center of the optical fiber, but in the case of line light, it is not necessary, so that the design, manufacture, and handling of the apparatus are easy.

To summarize the above concept, the optical fiber position detecting method according to the present invention is as follows. That is, the axis direction of the optical fiber is the z-axis, one direction perpendicular to the z-axis is the y-axis, directions perpendicular to the z-axis and the y-axis are the x-axis, and y
A long line light is irradiated in the x-axis direction from the axial direction toward the optical fiber, and the line light is transmitted through the optical fiber onto an image sensor installed on the opposite side of the light source with the optical fiber interposed therebetween. Image and a line-shaped image formed by passing the line light out of the optical fiber. The images obtained by detecting these images with an image sensor are converted into the y-axis direction and the x-axis direction of the optical fiber. Is detected (claim 1). According to this method, by using the line light, it is possible to detect the positions of the optical fiber in two directions only by observation from one direction.

Further, according to the present invention, the same object can be achieved by using both the line light and the parallel light conventionally used. That is, another method of detecting the position of an optical fiber according to the present invention is such that the axis direction of the optical fiber is the z-axis, one direction perpendicular to the z-axis is the y-axis, and the direction perpendicular to the z-axis and the y-axis is the x-axis. While irradiating a long line light in the x-axis direction from the axial direction toward the optical fiber, z
Irradiating parallel light having a spread on the x-plane, on an image sensor installed on the opposite side of the light source across the optical fiber, the line light is transmitted through the optical fiber, astigmatic imaging, An optical fiber contour image formed by passing parallel light through an optical fiber, and detecting these images with an image sensor to detect the positions of the optical fiber in the y-axis direction and the x-axis direction from an image obtained. (Claim 2).

When the line light and the parallel light are used together, the line light and the parallel light are simultaneously irradiated with an interval in the z-axis direction, and the astigmatic image and the optical fiber contour image are simultaneously detected by the image sensor. It is desirable (claim 3). When line light and parallel light are used together, it is also possible to irradiate the line light and parallel light with a staggered time and detect the astigmatic image and the optical fiber contour image with a staggered time using an image sensor. (Claim 4).

In the present invention, as shown in FIG. 4, the distance between the intermediate point between the _two focal points P ₁ and P ₂ of the astigmatic imaging to one focal point P ₁ , that is, the astigmatic imaging is performed. It is preferable to use half of the available area. This is because the direction in which the astigmatic imaging expands and contracts can be limited to one horizontal or vertical direction, so that the design of the image sensor and the image processing system becomes simpler than when the entirety of the astigmatic imaging is used. is there.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings. [Embodiment 1] FIGS. 6 and 7 show an embodiment of the present invention. In FIG. 6, reference numeral 6 denotes a light source array in which a large number of line light sources 6a are arranged in parallel at predetermined intervals, and reference numeral 7 denotes a lens in which a large number of cylindrical lenses 7a are arranged one by one at the same interval as the line light sources 6a. The arrays 1A and 1B are optical fibers for aligning axes for fusion splicing, 4 is a microscope, and 5 is an image sensor.

The axis directions of the optical fibers 1A and 1B are the z-axis,
Assuming that one direction perpendicular to the z-axis is the y-axis and the direction perpendicular to the z-axis and the y-axis is the x-axis, the longitudinal directions of the line light source 6a and the cylindrical lens 7a are oriented in the x-axis direction. Line light source 6
The light exiting from a is converged to line light by the cylindrical lens 7a, travels in the y-axis direction, traverses the optical fiber 1, is magnified by the microscope 4, and reaches the image sensor 5.

Assuming that only one of the line light sources 6a crossing the optical fiber 1A and one of the line light sources 6a crossing the optical fiber 1B are turned on and the others are turned off. An image like FIG. 7 (A) can be captured. In this image, 11A is an astigmatic image formed by the line light crossing the optical fiber 1A passing through the optical fiber 1A, and 11B is formed by the line light crossing the optical fiber 1B passing through the optical fiber 1B. Astigmatic imaging, 12A is a line image formed by passing line light intersecting the optical fiber 1A outside the optical fiber 1A, 12B
Is a line light crossing the optical fiber 1B.
It is a line-shaped image formed by passing outside.

According to this image, the astigmatic images 11A and 1A
Since the shape of 1B is different, the optical fibers 1A and 1B
It can be seen that there is a shift in the y-axis direction. In addition, since the position of the cut 13A of one linear image 12A and the position of the cut 13B of the other linear image 12B are vertically shifted, the optical fibers 1A and 1B may also be shifted in the x-axis direction. I understand.

Then, when the positions of the optical fibers 1A and 1B in the y-axis direction are adjusted to match each other, an image captured by the image sensor 5 becomes, for example, as shown in FIG. In this image, since the shapes of the astigmatic images 11A and 11B are the same, it can be seen that the optical fibers 1A and 1B do not shift in the y-axis direction. Therefore, thereafter, the optical fibers 1A, 1
If the position of the cut 13A of the linear image 12A and the position of the cut 13B of the linear image 12B are adjusted by adjusting the position of B in the x-axis direction, the optical fibers 1A and 1B
Will be completed.

[Embodiment 2] By the way, in the apparatus shown in FIG. 6, when all of the many line light sources 6a are turned on, the optical fibers 1A and 1B are irradiated with the parallel light having spread on the xz plane in the same manner. Therefore, the image sensor 5 has optical fiber contour images 14A and 14B as shown in FIG.
Is obtained. From this image, the optical fiber 1
A and B positions in the x-axis direction can be detected. Therefore, separately from this, as in Embodiment 1, FIG.
(A) If an image like (B) is obtained, the optical fiber 1A,
The position in the y-axis direction of 1B can be detected.

[Embodiment 3] In Embodiment 2, FIG.
And the images (A) and (B) are detected with a time lag, but the third embodiment detects them simultaneously to reduce the time.

In the apparatus shown in FIG. 6, of the many line light sources 6a, one intersecting with the optical fiber 1A and one intersecting with the optical fiber 1B are turned on, and a plurality of lines on both sides thereof are turned off. Then, all the remaining line light sources 6a are turned on. That is, the line light and the parallel light are simultaneously irradiated at intervals in the z-axis direction. Then, an image as shown in FIG. 9A is obtained. That is, the astigmatic images 11A and 11B are obtained by one lit line light source 6a between the turned off line light sources 6a. Line light source 6 that is turned off
Since all the line light sources 6a outside the area a are lit, this region is similar to the case where the optical fibers 1A and 1B are irradiated with parallel light having spread on the xz plane. Missing optical fiber contour image 14
A and 14B are obtained.

Therefore, the position in the y-axis direction can be detected by the shapes of the astigmatic images 11A and 11B, and the position in the x-axis direction can be detected by the optical fiber contour images 14A and 14B. FIG. 9B shows an optical fiber 1 from the state of FIG.
The images when A and B positions in the y-axis direction are adjusted to match the positions are shown.

[Embodiment 4] FIG. 10 shows another embodiment of the present invention. In this embodiment, when the tape-shaped optical fibers 15A and 15B are fusion-spliced, the positions of the plurality of optical fibers 1A and 1B are detected collectively. 6 are given the same reference numerals.

In this embodiment, the normal to the mirror surface is between the lens array 7 and the optical fibers 1A and 1B.
The half mirror 16 is installed so as to be at an angle of 45 ° with respect to the axial direction, and the parallel light from the second light source 17 is reflected by the half mirror 16 and irradiates the optical fibers 1A and 1B. . This configuration is used in the case where all the line light sources 6a of the light source array 6 do not emit light enough to obtain the optical fiber contour images 14A and 14B as shown in FIG. This is effective for obtaining a clear optical fiber contour image with the parallel light from 17. Note that FIG.
In the configuration shown in FIG. 8, an astigmatic image 11 as shown in FIGS.
To obtain A and 11B, the same observation as in the first embodiment may be performed without turning on the second light source 17.

[0026]

As described above, according to the present invention, 1
Since the positions of the optical fiber in two directions can be detected by observing from the directions, the position detecting system of the optical fiber can be greatly simplified, and the cost can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing the principle of a position detection method according to the present invention.

FIG. 2 is an explanatory diagram showing a shape of astigmatic imaging when a spot light is applied to an optical fiber according to FIG. 1;

FIGS. 3A to 3C are explanatory diagrams of a method of detecting a position of an optical fiber by applying a spot light to the optical fiber.

FIG. 4 is an explanatory diagram showing a detection range when a position of an optical fiber is detected by applying a spot light to the optical fiber.

FIG. 5 is an explanatory diagram of a method of detecting the position of an optical fiber by irradiating the optical fiber with line light.

FIG. 6 is a perspective view showing an embodiment of an optical fiber position detecting method according to the present invention.

FIGS. 7A and 7B are explanatory diagrams showing images detected by an image sensor according to an embodiment of the present invention.

FIGS. 8A to 8C are explanatory views showing images detected by an image sensor according to another embodiment of the present invention.

FIGS. 9A and 9B are explanatory diagrams showing images detected by an image sensor according to still another embodiment of the present invention.

FIG. 10 is a perspective view showing still another embodiment of the present invention.

FIG. 11 is an explanatory diagram showing a relative refractive index difference between a core and a clad of an optical fiber.

FIG. 12 is an explanatory view showing a conventional optical fiber position detection method.

FIG. 13 is an explanatory diagram of a luminance level obtained by a conventional position detection method.

FIG. 14 is a perspective view showing a conventional optical fiber position detecting method.

[Description of Signs] 1, 1A, 1B: Optical fiber 4: Microscope 5: Image sensor 6: Light source array 6a: Line light source 7: Lens array 7a: Cylindrical lens 11A, 11B: Astigmatic imaging 12A, 12B: Line-shaped images 13A, 13B: breaks in line-shaped images 14A, 14B: optical fiber contour images

Claims (4)

[Claims] 1. An optical fiber according to claim 1, wherein the axis direction is the z-axis, one direction perpendicular to the z-axis is the y-axis, and the direction perpendicular to the z-axis and the y-axis is the x-axis. Irradiates a long line light in the direction, on an image sensor installed on the opposite side of the light source across the optical fiber, the astigmatic image formed by transmitting the line light through the optical fiber, and the line light To produce a line-shaped image that passes through the outside of the fiber,
A method for detecting the position of an optical fiber, comprising detecting the positions of the optical fiber in the y-axis direction and the x-axis direction from images obtained by detecting these images with an image sensor. 2. The optical fiber according to claim 1, wherein the axis direction is the z-axis, one direction perpendicular to the z-axis is the y-axis, and the direction perpendicular to the z-axis and the y-axis is the x-axis. Along with irradiating long line light in the direction, irradiating parallel light with spread on the zx plane, the line light passes through the optical fiber on the image sensor installed on the opposite side of the light source with the optical fiber in between And an optical fiber contour image formed by the parallel light passing through the optical fiber. These images are detected by an image sensor to obtain the y-axis of the optical fiber. A position detecting method for an optical fiber, comprising detecting a position in a direction and an x-axis direction. 3. The apparatus according to claim 2, wherein the line light and the parallel light are simultaneously irradiated with an interval in the z-axis direction, and the astigmatic image and the optical fiber contour image are simultaneously detected by the image sensor.
The method for detecting the position of an optical fiber described in the above. 4. The optical fiber according to claim 2, wherein the line light and the parallel light are irradiated with a time shift, and the astigmatic image and the optical fiber contour image are detected with a time shift by an image sensor. Position detection method.