JP4789097B2 - Method and apparatus for measuring inner diameter of ferrule hole, etc. - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and an apparatus for measuring the inner diameter of a minute hole represented by a fiber insertion hole of a ferrule used for an optical fiber connector or the like.
[0002]
[Prior art]
In general, as shown in FIG. 4, a ferrule 100 made of a material such as ZrO ₂ has a small hole 200 having a diameter of about 125 μm at the center in order to incorporate an optical fiber. The accuracy of this hole 200 determines the performance of the optical fiber connector. Therefore, a high-precision measurement technique for the hole diameter is required together with a high-precision processing technique for the hole 200.
[0003]
The following methods are usually used for measuring the pore diameter.
[0004]
One method is to photograph the ferrule 100 from the front, obtain image data of the captured ferrule hole 200, calculate the center and radius of the circular hole from this image data using the least square method, This is a method of measuring the pore diameter. When the captured hole image has no special defect and is a hole image having a shape close to the design value, the hole diameter measurement by this least square method is accurate and can be measured with a variation of about ± 0.02 μm.
[0005]
By the way, in the hole drilling process of the ferrule 100, adhesion of hole bits and dust (10-3 in FIG. 3A) due to chipping of the edge of the hole (10-2 in FIG. 3A) may occur. is there.
[0006]
When there is such hole bit 10-2 or dust adhesion 10-3, as shown in FIG. 3A, an image of hole bit or dust adhesion is added to the captured image, so-called noise information and Thus, there is a problem that accurate measurement of the hole diameter becomes impossible.
[0007]
On the other hand, as a method for extracting a circle from an image including noise information, a method using Hough transform is generally known. In this method, noise information due to the hole bit 10-2 and dust adhesion 10-3 is removed from the image 10-1 of the hole 200 having the hole bit 10-2 and dust adhesion 10-3 as described above, The center and radius of the hole can be obtained. However, in this method, since the center of the hole is obtained from all edge information of the hole to be an image, the measurement accuracy depends on the capability (resolution) of the measuring device, and is true in the same environment as the measurement by the least square method. Even when a ferrule hole close to a circle is measured, there is a problem that variation of about ± 0.5 μm occurs.
[0008]
That is, in the case where there is noise information due to partial hole bits or dust adhesion, it is impossible to measure the inner diameter of the ferrule hole with a high accuracy of about ± 0.02 μm.
[0009]
[Problems to be solved by the invention]
The present invention solves the above-mentioned problems, and its object is to measure the inner diameter of a ferrule hole or the like capable of measuring the inner diameter of a small diameter hole such as a ferrule hole or the like having a hole bit or dust attached thereto, and A device is provided.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the method for measuring the inner diameter of a ferrule hole according to the present invention calculates an imaginary center of the hole by using an imaging process for photographing the hole of the ferrule and Hough transform on the image data of the photographed hole. From the virtual center calculation step and the virtual center of the hole calculated using the Hough transform, a region other than the circular region having a constant width having a minute width in the radius design value of the hole is set as a mask region, and the hole An image processing step for performing mask processing on the image data, and an inner diameter calculation for calculating the hole diameter and the center of the hole using the least square method with respect to the image data that falls within the circular region of the constant width among the image data of the hole. a step seen including, a constant width of the annular region, is characterized in adopting the values of the accuracy of the Hough transform.
Further, in the virtual center calculation step, the captured hole image data is divided into a plurality of pixel units, and all the pixel units in which the line segment of the hole image data exists from among the plurality of divided pixel units. It is also possible to calculate the normal center of each of the holes and calculate the virtual center of the hole by using the Hough transform for the calculated normal of each line segment.
[0011]
Further, the inner diameter measuring method of the small-diameter hole of the present invention includes an imaging step of photographing a small-diameter hole, and a virtual center calculating step of calculating a virtual center of the hole using Hough transform on the image data of the photographed hole. From the virtual center of the hole calculated using the Hough transform, a region other than the annular region having a constant width obtained by adding a minute width to the radius design value of the hole is set as a mask region, and mask processing is performed on the image data of the hole. an image processing step of performing, unrealized and inner diameter calculating step of calculating the pore diameter and the center of the hole by using a least squares method to the target image data into the annular region of the constant width of the image data of the hole The value of the accuracy of the Hough transform is adopted as the constant width of the annular region .
Further, in the virtual center calculation step, the captured hole image data is divided into a plurality of pixel units, and all the pixel units in which the line segment of the hole image data exists from among the plurality of divided pixel units. It is also possible to calculate the normal center of each of the holes and calculate the virtual center of the hole by using the Hough transform for the calculated normal of each line segment.
[0012]
The ferrule hole inner diameter measuring device according to the present invention includes an imaging means for photographing the hole of the ferrule, and a virtual center calculation for calculating the virtual center of the hole using Hough transform on the image data of the hole photographed by the imaging means. Means, annular data calculation means for calculating annular data of a constant width obtained by giving a minute width to the radius design value of the hole from the virtual center of the hole calculated by the virtual center calculating means, and the annular data calculation Mask processing means for performing mask processing on the image data of the hole using a region other than the annular data calculated by the means as a mask region, and image data included in the circular data of the constant width among the image data of the hole characterized by using a least square method; and a inner diameter calculating means for calculating the pore diameter and the center of the hole, a constant width of the annular data was adopted the value of the accuracy of the Hough transform It is intended to.
In addition, the virtual center calculation unit divides the image data of the photographed hole into a plurality of pixel units, and all the pixel units in which the line segment of the image data of the hole exists from the plurality of divided pixel units. It is also possible to calculate the normal center of each of the holes and calculate the virtual center of the hole by using the Hough transform for the calculated normal of each line segment.
[0013]
In the present invention, in the measurement of the inner diameter of the hole by image processing, a highly accurate inner diameter can be obtained without receiving noise information such as dust and partial defects.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment implemented for measuring the inner diameter of a ferrule hole of the present invention will be described with reference to the drawings.
[0015]
FIG. 1 is a flowchart showing a ferrule hole inner diameter measuring method according to the present invention, FIG. 2 is a block diagram showing the configuration of the ferrule hole inner diameter measuring apparatus according to the present invention, and FIG. 3 is a ferrule hole inner diameter measuring method according to the present invention. It is explanatory drawing explaining the measurement process by this.
[0016]
In order to measure the inner diameter of the ferrule hole 200, first, the ferrule is placed on a measuring table, and the edge 10-1 of the hole 200 is photographed from the front by the imaging means 1 such as a CCD camera (step 101, hole hole). Imaging).
[0017]
Next, in step 102, the hole virtual center calculation means 2 obtains the virtual center of the hole by using the Hough transform on the image data of the photographed hole 200. That is, in step 102, in this embodiment, the captured hole image is divided by a mesh in units of 5 pixels × 5 pixels, and the line m for all meshes m _{ij in} which the line segment of the hole image exists is _displayed. The normal of the minute is calculated, and the number of normals passing therethrough (normal passing frequency) k _xy is counted for each mesh in the virtual center search area near the center of the preset design hole. .
[0018]
The normal line of the processed regular edge portion 10-1 in FIG. 3A gathers in the vicinity of the center in the virtual center search region. Further, most normal lines of the missing part 10-2 do not pass through the virtual center search region, and the normal lines of the dust adhering part 10-3 in the figure are parallel to each other in the case of dust having the shape shown in the figure. Even if it is close to a line and passes through the virtual center search area, it does not concentrate on one point. Accordingly, the normal passing frequency k _xy has a maximum value at a portion where the normals of the edge portion 10-1 are concentrated. Depending on the shape of the missing portion 10-2 and the dust adhering portion 10-3, these normals may be concentrated at different locations in the virtual center search region and show the maximum value of the normal passing frequency k _xy. The maximum value is a portion where the normal lines of the edge portion 10-1 are concentrated.
[0019]
Therefore, the center of the mesh where the normal passing frequency k _xy has the maximum value is set as a virtual center 30 (FIG. 3B) by Hough transform.
[0020]
Although the virtual center 30 is close to the actual center of the hole 200, as described in the prior art, the virtual center 30 has a variation of about ± 0.5 μm and often deviates from the accurate center. Therefore, the inner diameter is measured with higher accuracy through the following process.
[0021]
The radius of the machined hole 200 should approximate the design radius. Therefore, in the present invention, only the image data close to the design radius from the virtual center is adopted out of the image data of the hole, and the center and radius of the hole 200 are obtained by the least square method from the image data close to the design radius. is there. The method will be described in detail below.
[0022]
In general, the limit of the measurement accuracy of the inner diameter measuring device by imaging is determined by the resolution of the imaging device, and is also affected by the reproducibility of the setting of the object to be measured. In the case of measuring the ferrule inner diameter, the current measurement level has a limit of about ± 0.02 μm when the least square method is used.
[0023]
Although it is preferable to reduce the image data to be subjected to the above least square method processing to a range very close to the design radius, the accuracy required by the Hough transform is ± 0. Since it is 5 μm and a variation of about ± 0.5 μm occurs, even if it is narrowed to a range narrower than this, it becomes practically meaningless due to the above-mentioned limit of measurement accuracy.
[0024]
Therefore, in the present invention, the accuracy limit of the measuring apparatus to be used, that is, the measurement accuracy is confirmed, and a value slightly larger than this measurement accuracy, for example, ± 0.5 to 0.7 μm (± R) is set in advance. Keep it. Then, in the annular data calculation means 3 of FIG. 2, the radius design value 4 of the hole 200 is calculated from the virtual center 30 obtained by the hole virtual center calculation means 2, the above ± R, and the radius design value 4 of the hole 200. Annulus data with a minute width 2R is calculated (step 103 in FIG. 1, mask pattern calculation).
[0025]
Using the ring data, the hole image mask processing means 6 performs mask processing on the image data of the image with the areas other than the ring 40 as the mask areas 50 and 60 as shown in FIG. Thereby, the image data of the hole 10-4 configured by the arc of the portion close to the designed circle 20 is obtained in the non-masked annular region 40.
[0026]
The image data entering the ring 40 is often partially missing due to removal of noise information such as dust, but the hole calculating means (inner diameter calculating means) 7 uses the least square method for this. Thus, it is possible to obtain a hole diameter and a center with high accuracy of about ± 0.02 μm (step 105 in FIG. 1, calculating the hole by the least square method from the image of the hole left unmasked).
[0027]
In the above-described embodiment, the inner diameter measurement of the hole of the ferrule has been described. However, the present invention is also applied to the inner diameter measurement of a small hole having a diameter of about 0.1 to 1 mm, and the image data of dust etc. Noise information can be removed and highly accurate measurement can be performed.
[0028]
【The invention's effect】
As is apparent from the above description, the present invention captures a virtual hole such as a ferrule hole, obtains a virtual center of the hole using Hough transform on the image data of the captured hole, and determines the virtual of the hole. Masking is performed on the image data of the image using a region other than the ring having a minute width from the center as a design value of the radius of the hole, and the image data entering the circle of the image data is targeted. Since the least square method was used to determine the hole diameter and center, noise information due to dust adhesion and the like was removed, enabling highly accurate inner diameter measurement of minute holes.
[Brief description of the drawings]
FIG. 1 is a flowchart showing a method for measuring the inner diameter of a ferrule hole according to the present invention.
FIG. 2 is a block diagram showing the configuration of a ferrule hole inner diameter measuring apparatus according to the present invention.
FIGS. 3A to 3D are explanatory views for explaining a measurement process by a method for measuring the inner diameter of a ferrule hole according to the present invention.
4A and 4B show a general ferrule, where FIG. 4A is a longitudinal sectional view, and FIG. 4B is a front view.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Imaging means 2 Hole sparse center calculation means 3 Ring data calculation means 6 Hole image mask processing means 7 Hole calculation means 10 Hole image 10-1 Processed hole edge image 10-2 Defect portion image 10-3 Dust adhesion Image of part 10-4 Hole image in unmasked area 20 Design circle (inner diameter)
30 virtual center 40 non-masked annular region 50, 60 mask region 70 calculated by least square method 100 ferrule 200 hole

Claims (6)

An imaging process for photographing the ferrule hole;
A virtual center calculation step of calculating a virtual center of the hole using Hough transform on the image data of the photographed hole;
From the virtual center of the hole calculated by using the Hough transform, a region other than a circular region having a constant width obtained by giving a minute width to the radius design value of the hole is set as a mask region, and mask processing is performed on the image data of the hole. Image processing steps to be performed;
Look including the inner diameter calculating step of calculating the pore diameter and the center of the hole by using a least squares method to the target image data into the annular region of the constant width of the image data of the hole,
A method for measuring the inner diameter of a ferrule hole, wherein the value of the accuracy of the Hough transform is adopted as the constant width of the annular region . In the virtual center calculation step,
The image data of the photographed hole is divided into a plurality of pixel units,
The normal of each line segment is calculated for all pixel units in which the line segment of the image data of the hole exists from the plurality of divided pixel units,
The method for measuring the inner diameter of a ferrule hole according to claim 1, wherein the virtual center of the hole is calculated by using a Hough transform for the calculated normal line of each line segment. An imaging process for photographing a small-diameter hole;
A virtual center calculation step of calculating a virtual center of the hole using Hough transform on the image data of the photographed hole;
From the virtual center of the hole calculated by using the Hough transform, a region other than a circular region having a constant width obtained by giving a minute width to the radius design value of the hole is set as a mask region, and mask processing is performed on the image data of the hole. Image processing steps to be performed;
Look including the inner diameter calculating step of calculating the pore diameter and the center of the hole by using a least squares method to the target image data into the annular region of the constant width of the image data of the hole,
A method for measuring the inner diameter of a small-diameter hole, wherein the value of the accuracy of the Hough transform is adopted as the constant width of the annular region . In the virtual center calculation step,
The image data of the photographed hole is divided into a plurality of pixel units,
The normal of each line segment is calculated for all pixel units in which the line segment of the image data of the hole exists from the plurality of divided pixel units,
The method for measuring an inner diameter of a small-diameter hole according to claim 3, wherein the virtual center of the hole is calculated using a Hough transform for the calculated normal line of each line segment. Imaging means for photographing the ferrule hole;
Virtual center calculation means for calculating the virtual center of the hole using Hough transform on the image data of the hole imaged by the imaging means;
Annulus data calculating means for calculating annular data having a constant width by giving a minute width to the radius design value of the hole from the virtual center of the hole calculated by the virtual center calculating means;
Mask processing means for performing mask processing on the image data of the hole using a region other than the annular data calculated by the annular data calculation means as a mask region;
An inner diameter calculating means for calculating the hole diameter and the center of the hole using the least square method for the image data included in the circular data of the constant width among the image data of the hole ,
The ferrule hole inner diameter measuring device adopting the accuracy value of the Hough transform as the constant width of the ring data . The virtual center calculation means is
The image data of the photographed hole is divided into a plurality of pixel units,
The normal of each line segment is calculated for all pixel units in which the line segment of the image data of the hole exists from the plurality of divided pixel units,
6. The ferrule hole inner diameter measuring device according to claim 5, wherein the virtual center of the hole is calculated using a Hough transform with respect to the calculated normal line of each line segment.

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