JP2000171237A - Method for measuring v-shaped groove - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly and highly accurately calculate a positional relation in a V-shaped groove for fixing an optic fiber by repeating linear approximation of a V-shaped groove side face until such a condition that an approximation error in an approximation range is within required accuracy and a contact point with an approximation line of an approximately cylindrical member fixed to the V-shaped groove is within the approximation range is satisfied. SOLUTION: A substrate 3 made of a glass material equipped with a plurality of V-shaped grooves 2 for supporting an optic fiber in parallel is mounted on a stage 4. On the other hand, a probe 7 extends downward from a tip of an arm 6 which extends sideward from a form measuring device body 5. At the time of measurement, the probe 7 is lowered and relatively moved sideward in an arrow direction while being in contact with the V-shaped groove 2 to measure a form of the groove 2. Then data analysis approach having an algorithm which repeats linear approximation of a side face of the V-shaped groove 2 until such a condition is satisfied that 1) an approximation error in an approximation range is within required accuracy and 2) a contact point with an approximation line of the optic fiber fixed in the groove 2 is within the approximation range is used to measure a form of the V-shaped groove.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring a V-groove formed in, for example, an optical fiber connector and a connector molding die.

[0002]

2. Description of the Related Art Conventionally, in a connector for connecting optical fibers to each other, in order to make a connection in a precise positional relationship, as shown in a perspective view in FIG. A structure is employed in which the optical fiber 1 is fixed to a plurality of V grooves 2 arranged in parallel. Note that the left and right and rear portions are omitted in FIG. In this case, the positional relationship between the V-groove, for example, where the center of the optical fiber comes, and the positional relationship between the optical fibers are important. Therefore, it is possible to actually place the optical fiber in the V-groove and measure its position. However, since the optical fiber itself has a shape error, it is necessary to know the standard positional relationship of the optical fiber with respect to the V-groove. Can not.

Therefore, as described in, for example, Japanese Patent Publication No. 6-79098, the shape of the V-groove is measured using a contact-type shape measuring device that is relatively easy to measure. An approximate straight line of the surface to be obtained is obtained, and the positional relationship is specified thereby.
This means that the stylus of the shape measuring machine is moved perpendicularly to the longitudinal direction of the V-groove, and at least 20 points on the surface are measured per V-groove. The edge portion and the bottom portion of the groove are each removed over a length of at least 10 μm, and the side shape of the V-groove is calculated by a least square method or the like based on measurement data having an effective measurement length of 40 μm or more. It is calculated as a shape formed by straight lines.

As another method, for example, as described in Japanese Patent Application Laid-Open No. 6-185982, a pin or a sphere of a predetermined shape is placed in a V-groove, observed with an image sensor by reflected illumination, and the output signal is obtained. Image processing is performed to obtain the center position of a pin or a sphere.

[0005]

However, in the method described in Japanese Patent Publication No. 6-79098, when the approximation section is long, the approximation becomes poor due to the undulation and distortion of the V-groove side surface, and the optical fiber May cause an error in the order of microns. Specifically, for example, as shown in FIG. 8A, an approximate straight line la indicated by a broken line calculated by a calculation method such as the least square method is analyzed by a broken line circle touching at a contact point a by analysis. Even if the optical fiber position 1a is derived by
The actual shape of the side surface of the V-groove undulates like lb, and the actual optical fiber position 1b indicated by the solid line circle contacting at the actual contact point b is the optical fiber position 1 by analysis.
It is conceivable that there is a large deviation from a.

In order to avoid such a situation, it is necessary to shorten the approximate section to some extent. In this case, FIG.
As shown in FIG.
In addition, with respect to the actual shape lb, each of the contact points a and b deviates from the approximate range N, and the actual optical fiber position 1b may further deviate from the analyzed optical fiber position 1a. In this way, when the purpose is to grasp the shape of the V-groove, in order to know the positional relationship of the optical fiber, processing such as approximation of measured data is required,
A calculation error is added.

In the method described in Japanese Patent Application Laid-Open No. 6-185982, a pin or ball, which is a dummy of an optical fiber, is actually placed in a V-groove and its position is measured. Since the dummy itself has a shape error, the measurement accuracy is reduced accordingly. In addition, in this method, measurement is usually performed using image processing or the like, but there is an error due to the image processing, and when a pin is used as a dummy, the upper end thereof is measured. Measurement accuracy decreases. Furthermore, the measurement work is troublesome as a whole.

The present invention has been made in view of the above problems, and provides a V-groove measuring method for quickly and highly accurately calculating the positional relationship between the V-grooves for fixing an optical fiber and the shape measurement results. Aim.

[0009]

In order to achieve the above object, the present invention employs a data analysis method having an algorithm for repeating a linear approximation of the side surface of a V-groove until the following condition is satisfied. (1) The approximation error within the approximation range is within the required accuracy. (2) The point of contact of the substantially cylindrical member fixed to the V-groove with the approximate straight line is within the approximate range. However, when (1) is not satisfied, the approximation range is narrowed,
When the condition (2) is not satisfied, the approximation range is taken again before and after the contact point.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the V of the present invention.
It is a perspective view which shows typically the structure at the time of the measurement by the contact-type shape measuring device used by a groove measuring method. As shown in the figure,
A substrate 3 made of a glass material or the like in which a plurality of V grooves 2 for supporting optical fibers are arranged in parallel with each other is mounted on a stage 4. On the other hand, a stylus 7 extends downward from a tip of an arm 6 extending laterally from the main body 5 of the shape measuring machine. At the time of measurement, while the stylus 7 is lowered and brought into contact with the V-groove 2, it is relatively moved to the side perpendicular to the longitudinal direction of the V-groove 2 as indicated by an arrow, and the shape of the V-groove 2 is changed. Measure.

The measurement location is mainly near the center of each V-groove 2, but may be measured at both ends or at other locations as needed. As the stylus 7 moves sideways, V
Since it moves up and down along the shape of the groove 2, it is detected by a strain gauge or a laser measuring device (not shown) incorporated in the main body 5, and is electrically converted into shape measurement data.

Incidentally, the measurement by such a shape measuring instrument has been conventionally performed, and is not limited to the contact type, and other methods, such as photographing a V-groove shape with a CCD camera,
A method of processing this image may be used. As a method of finding a direction perpendicular to the longitudinal direction of the V-groove 2, a method of comparing the longitudinal direction of the V-groove 2 with the relative movement direction of the stylus 7 by using a CCD camera, or the method of precisely moving the stage 4 by a predetermined angle. There is one that rotates and grasps the vertical direction in the manner of triangulation.

FIG. 2 shows the V-groove measuring method according to the present invention.
It is a figure which shows the principle of the analysis of shape measurement data typically.
FIG. 3 is a flowchart showing the flow of an algorithm for analyzing shape measurement data. In FIG. 2, first,
It is assumed that the optical fiber 1 whose cross section is indicated by a broken line having a circular shape is placed in the V groove 2. And both sides 2 of the V-groove 2
Approximate ranges N ₁ and N ₂ are respectively taken on a and 2b, and approximate straight lines l ₁ and l ₂ in the respective approximate ranges are obtained. These approximate straight lines are calculated by the least square method based on the shape measurement data in each approximate range.

The setting of these approximation ranges is as follows. First, as shown in the above-mentioned prior art, for example, the edge portion and the bottom portion of the V-groove are each removed over a length of at least 10 μm, and the effective measurement length is reduced. The measurement data may be 40 μm or more. Incidentally, R in the figure indicates the radius of the optical fiber 1, and here, a design value or an average value of the radius of the optical fiber fixed to the V-groove is assumed.

The procedure of analyzing the shape measurement data will be described below with reference to the flowchart of FIG. When the analysis is started, in step # 5, a straight line l _'1, l' ₂ intersections moved parallel to the inside of the approximate line l _1, l _2, respectively only the radius R of the optical fiber 1 V groove 2 and point C (See FIG. 2). Next, in step # 10, a straight line l '
Intersections (legs) s ₁ , s _{2 of} perpendiculars dropped to ₁ and l ′ ₂ respectively
Is determined within the approximate ranges N ₁ and N ₂ , respectively, and if so, the process proceeds to step # 15.

In step # 15, it is determined whether or not the mean square error of each approximation line by the method of least squares satisfies the required accuracy, that is, whether or not the accuracy required for the product is met. If so, the process proceeds to step # 20, and the analysis is completed with the point C as the center of the optical fiber 1.

In step # 10, the perpendicular legs s ₁ ,
If s ₂ does not exist within the approximate ranges N ₁ and N ₂ respectively,
Proceeding to step # 25, approximate ranges N ₁ and N ₂ are re-taken before and after s ₁ and s ₂ , and approximate straight lines l ₁ and l ₂ are recalculated.
Return to step # 5. Also, in step # 15,
If the root-mean-square error does not satisfy the required accuracy, the process proceeds to step # 30, where the approximate range of the approximate straight line is narrowed, and then the process returns to step # 5.

As a specific method of narrowing the approximation range, for example, a certain percentage of the current approximation range is determined according to the surface roughness or the surface undulation of the side surface 2a or 2b of the V-groove 2 obtained from the shape measurement data. It is done to narrow the range so that In this way, the contact point and the center of the optical fiber based on the V-groove shape measurement data are specified to the required accuracy.

FIG. 4 is a diagram showing an example of a calculation result of an optical fiber position when approximating a result obtained by actually measuring a V-groove having a surface waviness. As shown in FIG. 6 (a), the center C ₁ of the optical fiber of the analysis of the shape measurement data of the present invention, the center C of the optical fiber in the case of linear approximation for all shape data of a first approximation range described in FIG. 2 Comparing the positions with _2, it can be seen that there is an error of 0.7 μm vertically and 0.4 μm horizontally.

At this time, when FIG. 2B is enlarged, the vicinity of the contact point between the optical fiber indicated by * 1 and the V groove is observed.
There is a considerable deviation between the curve (measured value) connecting the actual measurement data and the shape approximation in the above-mentioned whole shape data. It can be seen that a considerable error occurs between the shape measurement data and the position of the optical fiber according to the analysis method of the present invention. It can be seen that the position of the optical fiber according to the analysis method in the present invention is clearly closer to the state of contact with the curve connecting the actual measurement data. This confirms that the V-groove measuring method of the present invention is effective.

FIG. 5 is a perspective view showing an example of another V-groove measuring method. Here, a shape measuring machine having another configuration is used. In FIG. 2A, an arm 14 is attached to a movable portion 11a on a Z stage 11 that drives in a Z-axis direction indicated by an arrow Z so as to be slidable in the Z-axis direction. The stylus 15 extends downward. Also,
The movable stage 12a on the X stage 12, which is driven in the X-axis direction indicated by the arrow X, is provided with a θ stage 13 rotatably around the Z-axis direction, on which the substrate 3 is placed. ing. The movement of the stylus 15 in the X-axis and Z-axis directions is
It is measured with high accuracy using a laser length measuring device not shown.

FIG. 2B is an enlarged view of a portion A indicated by a broken-line circle near the substrate 3. As shown in FIG.
At the lower end of the stylus 15, a sphere 16 having the same diameter as the optical fiber and having a high sphericity is attached. The V-groove 2 is traced in the direction by the X stage 12 as shown by the arrow B. Note that the adjustment to make the X-axis direction perpendicular to the longitudinal direction of the V-groove 2 is θ
This is performed by the stage 13.

FIG. 6 is a diagram schematically showing the measurement principle of this embodiment. As shown in the figure, the ball 16 attached to the lower end of the stylus 15 indicates the arrow B in the X-axis direction, which is the direction perpendicular to the longitudinal direction of the V-grooves 2 juxtaposed on the substrate 3. When the V groove 2 is traced as follows, the center O of the sphere 16 becomes
A measurement trajectory L indicated by a broken line is drawn. Here, since the radius R of the sphere 16 indicated by the dimension line is also the radius of the optical fiber, the lowest point O ₁ in each V groove 2 of the measurement trajectory L is determined as the center position of the optical fiber.

In this embodiment, since the positional relationship between the optical fibers can be directly grasped without using linear approximation or image processing, it is possible to perform highly accurate measurement without requiring complicated calculation processing and analysis. . In addition, since the measurement operation only needs to be traced using a shape measuring instrument, the measurement can be performed in a short time. Further, since all the V-grooves are measured with one sphere, there is no influence from a shape error between the dummies as in the case of using the optical fiber dummies shown in the above-mentioned conventional technology.

The substantially cylindrical member referred to in the claims is:
It corresponds to the optical fiber in the embodiment.

[0026]

As described above, according to the present invention,
A V-groove measuring method for quickly and accurately calculating these positional relationships from the V-groove shape measurement results for fixing the optical fiber can be provided.

That is, in the case of the conventional simple linear approximation, V
If the shape accuracy of the groove is poor, the calculated optical fiber position and the actual optical fiber position may deviate significantly, but in the case of the present invention, the approximation error within the range of the data used for the linear approximation is required accuracy. Is satisfied, and that the contact point is within the approximate range is guaranteed.
The position of the optical fiber fixed to the groove is calculated with high accuracy.

What is important in the V-groove is the positional relationship of the optical fibers. By using the present invention, it is possible to allow a certain amount of undulation, etc., so that even if the shape of the V-groove is bad, if it is considered that the position of the optical fiber should be the same, the position of the optical fiber can be adjusted with less processing correction than usual from the feedback of the measurement result. Within the required accuracy.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing a configuration at the time of measurement by a contact type shape measuring instrument.

FIG. 2 is a diagram schematically showing the principle of analysis of shape measurement data.

FIG. 3 is a flowchart showing a flow of analysis of shape measurement data.

FIG. 4 is a diagram showing an example of a calculation result of an optical fiber position.

FIG. 5 is a perspective view showing an example of another V-groove measurement method.

FIG. 6 is a diagram schematically showing a measurement principle of this example.

FIG. 7 is a perspective view showing a structure for fixing an optical fiber in the connector.

FIG. 8 is a diagram showing a deviation between an optical fiber position and an actual position according to a conventional analysis.

[Explanation of symbols]

 Reference Signs List 1 optical fiber 2 V groove 3 substrate 4 stage 5 body 6 arm 7 stylus 11 Z stage 12 X stage 13 θ stage 14 arm 15 stylus 16 ball

Claims (1)

[Claims] 1. A V-groove measuring method using a data analysis method having an algorithm for repeating a linear approximation of the side surface of a V-groove until the following conditions are satisfied: (1) An approximation error within an approximation range is within required accuracy. (2) The point of contact of the substantially cylindrical member fixed to the V-groove with the approximate straight line is within the approximate range. However, when (1) is not satisfied, the approximation range is narrowed,
When the condition (2) is not satisfied, the approximation range is taken again before and after the contact point.