JP3317100B2 - Optical connector polished surface automatic inspection device and optical connector polished surface inspection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for automatically inspecting a polished surface of an optical connector used for optical communication.

[0002]

2. Description of the Related Art In an optical connector used in an optical communication system, low connection loss and low reflection at an optical connection portion are required. To achieve this, the end face of the optical connector is usually precision polished to a convex spherical shape. In particular, recently, there is a strong demand for low reflection at the connection portion of the optical connector, and a return loss of 40 dB or more is required. In order to satisfy such demands, a polishing technique for realizing ultra-low reflection and a shape inspection of a polished surface are important. In order to obtain a low-reflection polished surface, for example, a radius of curvature of a convex spherical polished surface of about 10 to 25 mm, a deviation between the center of an optical fiber of 50 μm or less and a polishing apex (hereinafter, a vertex displacement), and a ferrule polished surface of 50 nm or less. It is necessary to realize a deviation (hereinafter referred to as a step) between the apex and the center of the optical fiber, and at the same time, it is required that the polished surface be free from scratches and dirt.

On the other hand, conventionally, the measurement is performed separately using an individual measuring instrument, and the step measurement requiring high-precision measurement of several tens of nm is not a complete test but a sampling test. Hereinafter, a measuring method using a conventional measuring device will be sequentially described with reference to the drawings.

First, a measurement method using a surface roughness meter will be described. FIG. 7 illustrates a method of measuring a radius of curvature using a surface roughness meter. FIG. 7A is a diagram for explaining a method of measuring a radius of curvature and a step using a surface roughness meter.
(B) is an enlarged view of a ferrule end face seen from the Z-axis direction. FIG. 8 is an example of a chart output measured by a surface roughness meter.

In FIG. 7, reference numeral 700 denotes a ferrule to be inspected; 701, a surface plate; 702, an XY position adjusting mechanism;
Is a ferrule attachment jig, 704 is a surface roughness meter, 705 is a stylus, 706 is an arm, 707 is a position detector, 708 is a chart, 709 is an optical fiber, 710 is a core, 711
Is zirconia. 8, 800 is zirconia, 801 is an optical fiber, and 802 is an output chart.

In FIG. 7A, a ferrule 700 to be inspected is set on a ferrule mounting jig 703 provided on an XY position adjusting mechanism 702 on a surface plate 701. Next, the stylus 705 of the surface roughness meter 704 is
When the arm 706 is lowered in the Z-axis direction (Z-axis direction) until it comes into light contact with 0, and then the stylus 705 is scanned in the X direction at a constant speed V, the stylus 705 moves in the Z direction according to the shape of the ferrule 700 to be inspected. Displace. This displacement is converted into a position signal by a position detector 707 and amplified by an amplifier to obtain an enlarged displacement δz in the Z direction. By plotting the displacement L obtained from the velocity V on the horizontal axis and the δz on the vertical axis on the chart 708, an enlarged profile of the ferrule 700 to be inspected is obtained.
Can be calculated.

FIG. 8 shows an output example of the chart 708. d
Is the measurement length, and h is the vertex P from the position Po where the measurement length d was measured.
If the height is up to z, the radius of curvature R
Is represented by the following equation.

[0008]

(Equation 1)

Therefore, R can be obtained by reading d and h from the output chart 802. In addition, as for the step, zirconia 8 on the optical fiber center axis Of is used.
The difference between the virtual vertex Pz of the polished surface of No. 00 and the vertex Pf of the optical fiber 801 can be measured by reading from the output chart 802.

[0010] However, this measurement method has a drawback that the contact method is used, which may damage the sample, and that the measurement is time-consuming because of the stylus method. In order to accurately measure the radius of curvature and the step, after positioning the stylus 705 at the center position (several μm area) of the core 710 of the optical fiber 709 contained in the zirconia 711 as shown in FIG. Need to scan. However, the core 710 of the optical fiber 709 is used for visual positioning.
It is impossible to position the stylus 705 at the center position of. If a surface roughness meter for three-dimensional shape measurement that is commercially available recently is used, the entire surface of the optical fiber is scanned with a stylus, so it is not necessary to position the optical fiber at the center of the optical fiber as described above. It cannot be used as an online (ONLINE) measurement or a 100% inspection measuring instrument. Furthermore, in such a measuring method, it is necessary to perform the mounting accuracy of the ferrule mounting jig on the stylus scanning axis with high accuracy in order to detect the remaining inspection item, that is, the vertex displacement. From such a point, it is practically impossible to detect a vertex displacement by this method, and at present, it is not actually performed. Therefore, in order to detect a vertex shift, it must be used in combination with a measuring device described later.

FIG. 9 shows an example of a conventional inspection method in which interference fringes are formed by using a microscope and a parallel glass plate to detect a curvature radius and a vertex shift. 9, 900 is a microscope, 901 is an objective lens, 902 is a transparent parallel plate,
903 is a sample stage, 904 is a ferrule gripper, 9
05 is a ferrule to be inspected, 906 is a white light source, 907
Is a half mirror, 908 is a CCD, 909 is a CCD controller, 910 is a monitor, 911 is interference fringes, and 912 is an optical fiber image.

A transparent parallel plate 902 is disposed in front of an objective lens 901 of a microscope 900, and a sample stage 90
The ferrule 9 to be inspected is attached to the ferrule gripper 904 on
05 is set so that the tip physically contacts the parallel plate 902. Next, when the white light source 906 of the microscope 900 is turned on, the white light goes straight on the illumination optical path Oin, and after being deflected 90 degrees by the half mirror 907, through the objective lens 901,
The end faces of the parallel plate 902 and the ferrule 905 to be inspected are irradiated. In such a state, a so-called Newton ring interference fringe is generated between the parallel plate 902 and the inspection ferrule 905 polished to a convex spherical surface. This interference fringe is a ring fringe corresponding to a contour line at a half pitch of the measurement wavelength λ. This interference fringe is converted into an objective lens 901, a half mirror 90
7, and is received by the CCD 908.

The signal received by the CCD 908 is a CCD signal.
It is output to the monitor 910 via the controller 909. The optical fiber image 912 is displayed on the monitor 910 together with the interference fringes 911. The diameter of the interference fringes 911 has a correlation with the radius of curvature R of the convex spherical surface. Radius of curvature R
Can be obtained by the following equation using the radii a and b (a> b) of adjacent interference fringes and the height difference h (h = λ / 2) between the interference fringes.

[0014]

(Equation 2)

Next, a description will be given of a vertex shift according to this conventional example. As shown in FIG. 10A, when there is no inclination between the optical axis Oray of the optical meter and the central axis Of of the ferrule 905 to be inspected, the polished vertex coincides with the interference fringe vertex (Ix, Iy). Therefore, the deviation of the vertex, which is the deviation between the polished vertex and the center (Cx, Cy) of the optical fiber 912, is caused by the interference fringe center (Ix, Iy) and the center of the optical fiber 912 (Cx, Cy).
y) can be determined by calculating the deviation between them. However, in this measurement method, as shown in FIG. 10B, when there is an inclination φ between the optical axis Oray of the optical meter and the central axis Of of the ferrule 905 to be inspected, the interference fringe center C moves to C ′. The center of the interference fringe does not mean the vertex of the polished surface. Therefore, simply the optical fiber 9
The vertex deviation cannot be obtained from the deviation between the center (Cx, Cy) of the twelve and the center C ′ of the interference fringe 911. Therefore, in order to remove the inclination φ component, a method is adopted in which the ferrule 905 to be inspected is rotated around the Z axis, three or more points are measured, the rotation center is obtained from the coordinates of the measurement points, and the inclination component is corrected. (Shinke et al., 1988 IEICE Spring National Convention C-558, (1988) 19
One. However, in such a measuring method, since it is necessary to rotate the ferrule for three or more points to perform the measurement, it takes a long measurement time.
A constant pressing force is applied between the ferrule 905 and the parallel flat plate 902, and when the ferrule 905 to be inspected is rotated, the parallel flat plate 902 and the ferrule 905 to be inspected are separated by a force greater than the pressing force and rotated in that state, and then both contact. Complicated handling of the sample is required. Furthermore, since the contact type measurement method is used, there is a possibility that the sample may be damaged such as a scratch, and the state of contact between the inspection target ferrule 905 and the parallel flat plate 902 before and after rotation cannot be said to be the same. It is not always constant and has disadvantages such as causing measurement errors. Further, since the step cannot be measured by this measuring method, it is necessary to measure the step using a measuring device other than the measuring device as described in the above-mentioned conventional example.

[0016]

As described above, the conventional measuring method is based on a contact-type measuring method, and thus has the drawback that the sample may be damaged and the sample must be mounted with high precision. There is. Also, in the conventional method,
Since the measurement takes a long time, online (ONLINE) or 100% inspection cannot be performed at the actual assembly site, and there is a problem that sufficient quality cannot be guaranteed. In addition, since the measurement is performed using a plurality of measuring instruments, there is a problem that inspection time and inspection cost are required.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a high-speed and high-precision optical connector polished surface automatic inspection method for inspecting the shape of a polished surface without damaging a sample. An object of the present invention is to provide an inspection apparatus and an optical connector polished surface inspection method.

[0018]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to an apparatus for automatically inspecting a polished surface of a ferrule for an optical connector attached to an end of an optical cord or an optical fiber, and illuminates a white light source and a half mirror. In the light traveling direction, the illumination light is deflected by 90 degrees via a half mirror.
A magnifying objective lens is provided in the traveling direction, and the reflected light from the ferrule to be inspected disposed at the tip of the magnifying objective lens is positioned at a position where an image is formed via the magnifying objective lens and the half mirror.
A magnifying optical meter that forms an end face image of a ferrule to be inspected by arranging a CD element, and an interference filter is automatically or manually inserted on the illumination optical path between the white light source and the half mirror described above, and the light of the magnifying objective lens is further added. Switching to the interference objective lens at the same position as the axis center position by a slide-type transfer mechanism, etc., and configuring the interferometer, aligning the ferrule to be inspected at the focal position of these two enlarged and interference objective lenses.
A high resolution (100 nm) of the order of 10 nm composed of a ferrule aligning and gripping mechanism for fixing the ferrule to be inspected by spring force, etc. and an alignment part such as a V-groove to be positioned, and a piezo for applying displacement in the optical axis direction of the optical meter. And a differential stage and a contrast value of an image signal obtained by the CCD element and auto-focusing on the focal position of the enlarging and interfering objective lens, respectively. A frame memory for A / D (analog / digital) conversion of an electric signal from a CCD element which captures an enlarged image and an interference fringe image generated by an enlargement and interference optical meter, and image processing for image analysis of the interference fringe image And a micro-displacement stage that performs micro-transfer four times or more in the direction of the optical axis of the optical meter 1/8 or less of the used wavelength λ. From the obtained four or more interference fringe images, a step, which is a deviation of the optical fiber apex of the optical fiber center axis and the imaginary vertex of the zirconia part in the optical axis direction, the radius of curvature of the polished convex spherical surface, the center of the optical fiber, The optical meter between the polished surface vertices is inspected for the deviation of the vertex, which is the deviation in the optical axis direction and the vertical plane, and the end face scratches and dirt are observed by an enlarged image by the magnifying optical meter. Optical connector polished surface with a function to automatically mechanically handle the ferrule to be inspected at the optical axis center and focal position of the scale and magnifying optical meter, and after the inspection, automatically mechanically handle the ferrule to be inspected and return to the initial position It is characterized by being an automatic inspection device, and the above-mentioned interference optical meter detects the center of the interference fringe and the center of the optical fiber from the interference fringe image formed on the CCD element. Correct the angular deviation between the optical axis of the interferometer and the central axis of the optical fiber of the ferrule to be inspected, calculate the apex deviation from this correction value and the center of the interference fringe, and then move it four or more times finely by the fine displacement stage. The radius of curvature is calculated from the obtained four or more interference fringe images, the phase of the optical fiber end face and the phase of the zirconia part are calculated and converted into height information, and the height of the polished vertex height of the zirconia part and the height of the optical fiber end face are calculated. This is an optical connector polished surface inspection method characterized by detecting a step from the difference, and the inspection time can be shortened by one digit or more compared to the conventional contact method and the measurement method that was performed by combining individual measuring instruments. The non-contact type does not damage the surface to be inspected, so high-quality inspection can be performed.The inspection is automatically performed by the robot hand mechanism, auto focus function, and automatic switching of the objective lens and interference filter. Of the reduction of inspection costs Hakare and high precision and so attained
It differs from the conventional technology in that a highly reliable inspection can be performed.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows an embodiment of the present invention, and FIG. 2 shows a configuration diagram of an optical meter used in the present embodiment. In the drawing, reference numeral 100 denotes an optical cord to which a ferrule to be inspected is attached, 100a is a ferrule to be inspected, 100b is another ferrule attached to the other end of the ferrule 100a to be inspected, and 101 is an X that absorbs an attachment position error in the X direction. Stage, 102 is a minute displacement stage, 102a is a minute displacement stage controller, 103
Is a ferrule aligning and gripping tool, 103a is a V-groove made of zirconia, 103b is a holding plate having a flat plate portion 103d made of zirconia, 103c is a coil spring provided at an end of the holding plate 103b, 103e is a stopper, and 104 is a top and a bottom of the holding plate. 104a is an air pipe, 105 is an external white light source, 105a is a bundle fiber, 105b is an emission head, 106 is an interference filter, 107 is a magnifying objective lens,
108 is a mechanical slide mechanism for an objective lens, 108a is an air pipe, 109 is an interference objective lens, 109a is a reference mirror (FIG. 2), 110 is a mechanical slide mechanism for an interference filter, 110a is an air pipe, and 111 is a vibration isolation table. Surface plate, 112
Is a white light source, 112a is a light amount adjuster, 113 is a half mirror (FIG. 2), 114 is a CCD element, 114a is a CCD controller, 115 is a computer, 116 is a lens holder,
117 is a ferrule fixing jig at the other end.

The ferrule to be inspected is one whose end face is polished to a convex spherical surface, and which has a polished ferrule attached to both ends or one end of an optical cord or an optical fiber core. In the present embodiment, an example of an optical cord with both ends ferrule will be described. The ferrule on the objective lens side will be described as a ferrule to be inspected, and the ferrule attached to the other end will be described as a ferrule at the other end.
If the set positions of the two ferrules are exchanged, the other ferrule can be inspected.

First, the ferrule 100a to be inspected, which has been polished into a convex spherical shape, is set on the ferrule aligning / holding tool 103 on the minute displacement stage 102 attached to the X stage 101. The X stage 101 is for absorbing an attachment error in the X direction between the optical meter and the ferrule alignment / grip 103. Ferrule alignment and gripping tool 103
Sets the inspection target ferrule 100a to the optical axis Ora of the optical meter.
In order to grip with high precision with respect to y, the ferrule 100a to be inspected is aligned and gripped by a holding plate 103b having a flat portion 103d made of zirconia as well as a V groove 103a made of zirconia. Further, the inspection target ferrule 100a is fixed by inserting the inspection target ferrule 100a into the ferrule aligning / griping tool 103, exhausting the air of the slide mechanism 104 for holding up and down the holding plate, and setting the coil spring provided at the end of the holding plate 103b. This is performed by the elastic force of 103c. To remove the ferrule 100a to be inspected, air is injected through the presser plate up / down slide mechanism 104 and the presser plate 1 is removed.
03b is lifted.

On the other hand, the white light emitted from the external white light source 105 is guided by the bundle fiber 105a and emitted by the emission head 105b.
Is incident on the other end ferrule 100b set at. By injecting white light from the other end ferrule 100b, it is possible to simplify the detection of the center of the optical fiber of the inspection target ferrule 100a at the time of image processing, and it is also possible to check the disconnection of the optical fiber in the optical cord 100. If only the ferrule 100a to be inspected is attached to the optical cord 100 and there is no ferrule 100b at the other end, so-called pigtail type, the center position of the optical fiber is measured in advance, and this position is set as the default value of the center position of the optical fiber. By setting it in the inspection program, the inspection can be performed in the same manner as in the case of the optical cord with a ferrule for an optical connector at both ends. In this case, the disconnection of the optical fiber cannot be checked.

Next, two optical meters, a magnifying optical meter for white illumination (the same as the configuration of a normal metal microscope) and an interferometer, can be configured as optical meters used for inspection. The magnifying optical meter is configured by removing the interference filter 106 from the illumination optical path Oin, setting the magnifying objective lens 107 on the objective lens, and then switching the objective lens to the interference objective lens 109 by the mechanical slide mechanism 108 for the objective lens. At the same time, the interference filter 106 is inserted into the illumination optical path Oin by the mechanical slide mechanism 110 for the interference filter, thereby forming an interference optical meter. As a switching method of the objective lens, in addition to the switching method of the slide mechanism described here, a rotary switching method using an electric revolver is also conceivable. However, the switching mechanism of the slide mechanism type has the advantage that the mechanical interference area at the time of switching can be made smaller than that of the rotary type, so that the optical axis Oray of the optical meter is low and the optical meter is strong against external vibration and the like. The optical meter, the X stage 101, the minute displacement stage 102, and the ferrule aligning / holding tool 103 described above are set on an anti-vibration base 111 to minimize the influence of external vibration.

FIG. 2 shows the configuration of the optical meter. The white light is adjusted to an appropriate light amount by the light amount adjuster 112a and emitted from the white light source 112. The magnifying optical meter is a half mirror 11
3. Consisting of a magnifying objective lens 107 and a CCD element 114, in the interferometer, the interference filter 106 is connected to the illumination optical path O
in, and the objective lens 107 is switched to the interference objective lens 109. In the interferometer, the reflected light Pm of the reference mirror 109a in the interference objective lens 109 and the reflected light Pr from the ferrule 100a to be inspected are used.
To form an interference fringe image of the polished end face of the ferrule 100a to be inspected on the CCD element 114. In FIG. 2, the description has been made using a finite optical meter. When the optical meter is an infinite system, the CCD element 114 and the half mirror 11 shown in FIG.
Although an image forming lens is arranged between the three and an objective lens is formed as an optical meter in which an image is formed by using an infinite system lens, in this embodiment, the image formed is processed and inspected. Does not matter whether the system is infinite or finite.

Next, the entire inspection will be described with reference to FIG. 1. First, the ferrule 100a to be inspected is manually set in the V-groove 103a in the ferrule aligning / holding tool 103. At this time, air is injected into the presser plate vertical slide mechanism 104 via the air pipe 104a, and the ferrule 100a to be inspected is inserted into the V-groove 1 with the presser plate 103b lifted.
The V-groove 1 is brought into contact with a stopper 103e having a circular opening (approximately φ0.8 to 1.5) at the front end of the groove 103a.
03a. By this abutment, coarse positioning of the Z axis is performed. After that, the slide mechanism 10 for raising and lowering the holding plate
And the coil spring 103 of the holding plate 103b
The ferrule 100a to be inspected is aligned and fixed in the V-shaped groove 103a by the pressing force c, and the positioning is performed in the XY directions in the figure.

The optical meter is initially set to, for example, a magnifying optical meter, and the illumination light from the white light source 112 illuminates the end surface of the ferrule 100a to be inspected set via the magnifying objective lens 107. The reflected light from the end surface of the inspection target ferrule 100a is imaged on the CCD element 114, and the image is reflected on the computer 115 via the CCD controller 114a.
The image is taken on an image processing board (not shown) mounted in the inside. The enlarged image is subjected to image enhancement processing such as density conversion and differentiation processing, and the enhanced image together with the original image is stored in the storage device of the computer 115. Next, in order to switch to the interferometer, a computer 115 controls an electromagnetic valve (not shown) for turning on / off the air, and injects air into the mechanical slide mechanism 110 for the interference filter via the air pipe 110a. The interference filter 106 to the illumination optical path Oin.
At the same time, air is injected into the mechanical slide mechanism 108 for the objective lens through the air pipe 108a to switch from the expansion objective lens 107 to the interference objective lens 109. In this configuration, white light emitted from the white light source 112 is converted into monochromatic light by the interference filter 106,
Inspection target ferrule 10 via interference objective lens 109
Irradiate the end face of the inspection target ferrule 1 as described above.
Concentric interference fringes are imaged on the CCD element 114 due to interference between the reflected light from the end face of 00a and the reference mirror 109a of the interference objective lens 109. The interference image is captured on an image processing board (not shown) in the computer 115 via the CCD controller 114a, and the radius of curvature, the vertex deviation, and the step are calculated using the detection principle described later.

In this embodiment, the ferrule aligning / grasping device 103 is attached to the minute displacement stage 102.
The minute displacement stage 102 is a piezo-driven stage having a displacement magnification mechanism using a mechanical lever, and has a detection range of 100 μm in which a minute displacement stage controller 102a is feedback-controlled so that the displacement is constant.
m, a stage having a resolution of about 10 nm. This minute displacement stage 102 is used to realize four functions. First, by absorbing the mounting error in the optical axis Oray direction between the optical meter main body and the ferrule alignment / grip 103, the mounting error of the ferrule alignment / grip 103 or the like of about several tens of μm can be tolerated. It is easy to assemble, adjust and maintain the equipment.

Next, absorption of the mounting error between the lenses will be described. In this embodiment, two confocal objective lenses 107 and 109 are used. Usually, since the mounting of the objective lens is a screw interface, even if the two objective lenses are mounted on the lens holder 116 with high accuracy, the focal length of the two objective lenses is about 10 μm due to a machining error. Distance deviation is inevitable. On the other hand, the minute displacement stage 102 is driven by the piezo in the Z direction to individually measure the focal position of each objective lens, and a default focal position is given in the inspection program. As a result, the focal length deviation between the two objective lenses can be substantially eliminated, so that there is an economical advantage that a commercially available objective lens can be used as well as ease of assembly, adjustment, and maintenance.

Next is the autofocus function. Even if each focal length is set as described above, several μm in the focal direction (Z direction) due to temperature change in the actual use stage.
The image changes and the image becomes out of focus. To solve this, C
Based on the image signal obtained by the CD element 114, the micro-displacement stage 102 can be controlled to perform autofocus, so that a stable inspection can be performed.
As an example of autofocus of an enlarged image, a position at which a differential value of an edge portion of an end face of an optical fiber on a certain scanning line becomes maximum while a displacement is given by the minute displacement stage 102, and when a maximum value is given. Small displacement stage 102
The position can be realized by positioning the minute displacement stage 102 again at the displacement position. In addition, regarding the autofocus of the interference fringe image, the contrast value of a certain scanning line is obtained while similarly displacing the minute displacement stage 102, and the displacement value of the minute displacement stage 102 at the time when the maximum contrast is given is minutely moved again. It can be easily performed by positioning the displacement stage 102.

Finally, there is a step measurement method using a fringe scanning method described later. In the fringe scanning method, it is necessary to give a minute displacement of λ / 8 or less, and this is realized using this minute displacement stage 102.

The minute displacement stage 102 described above
Is controlled by the computer 115 via the minute displacement stage controller 102a. Hereinafter, a method of detecting each item will be briefly described.

First, a method of detecting the radius of curvature will be described with reference to FIG. The concentric circle shown in FIG.
00a represents an interference fringe on the end face, 301 is an interference fringe image, and 302 is an optical fiber image. The radius of curvature R is
From the interference fringe image 301 formed by the interference optical meter, interference fringe center (Ix, Iy) interference fringe radius r ₁ of the interference pattern center (Ix, Iy) interference based on fringe image 301 of Toko, ..., a r _n If detection is performed sequentially and the adjacent interference fringe radii a and b (a> b) are used, it can be easily calculated by the equation (2) shown above. Also, it is possible to easily obtain an average radius of curvature from three or more interference fringe radii.

Next, the measurement of the vertex shift will be described with reference to FIG. In FIG. 4, reference numeral 401 denotes a ferrule to be inspected;
2 is a V groove, 403 is an interference objective lens, 404a and 404
b and 404c are interference fringe centers, 405 is a trajectory circle, and 406 is an optical fiber.

The measurement of the vertex displacement in the present embodiment is basically different from the conventional example in that the measurement can be performed in a non-contact manner because the interference fringes are formed using the interference objective lens 403.
The measurement of the apex deviation may be obtained by determining the distance between the center of the optical fiber 406 and the apex of the polishing. However, as described in the conventional vertex displacement measurement (FIGS. 9 and 10), when the inclination φ exists between the optical fiber center axis Of of the inspection target ferrule 401 and the optical axis Oray of the interferometer, at least,
Rotate the ferrule three times or more to obtain the interference fringe center 404.
It is necessary to obtain and calculate the rotation center Cr of the locus circle 405 drawn by a, 404b, and 404c. However, the inclination φ between the central axis of the V groove 402 for aligning the ferrule to be inspected and the optical axis Oray of the optical meter is constant even when the ferrule 401 to be inspected is replaced. Therefore, the vertex displacement can be obtained from the distance between the interference fringe center and the coordinate value of the rotation center Cr by measuring the coordinate value of the rotation center Cr in advance and setting it in the inspection program. Can be.

Next, the principle of measuring the step will be described with reference to FIG. FIG. 5 is a cross-sectional view of the ferrule tip section cut along the optical axis Of, where 501 is an optical fiber, and 502 is a zirconia section.

A fringe scanning method is used as the step detecting method. Step δ
5, the center apex Pf of the optical fiber 501 on the central axis Of of the optical fiber 501 and the zirconia portion 50 as shown in FIG.
2 is the deviation from the virtual vertex Pz. In the fringe scanning method, one cycle (λ / 2) of an interference fringe is divided into N, and a transfer amount corresponding to 1 / N of λ / 2 is shifted in the optical axis Oray direction using the minute displacement stage 102 shown in FIG. Transfer. The minute displacement stage controller 102a performs feedback control so that the displacement of the minute displacement stage 102 is constant, and the computer 11
In response to the command from 5, the small displacement stage 102 is transferred N times. Generally, N = 4 is often used from the viewpoint of calculation time and the like.

The phase of each point on the end face of the ferrule to be inspected is calculated from the image signal acquired for each scan, and the height of the center vertex Pf of the optical fiber 501 and the zirconia portion 50 are calculated.
When the height of the vertex Pz of No. 2 is obtained, the step (δ = Pz−P
f) can be calculated.

First, the vertex Pf at the center of the optical fiber 501
Can be easily obtained by obtaining a phase based on N image signals obtained by moving the minute displacement stage 102 N times, and then converting the phase into height information. On the other hand, the apex of the zirconia portion 502 is lost in a state where there is a so-called stepped portion drawn by the optical fiber 501. Therefore, in order to obtain the virtual vertex Pz of the zirconia portion 502, it is necessary to estimate the luminance signal of the virtual vertex Pz from the interference fringe image. Since the zirconia portion 502 is a convex spherical surface, a so-called Newton ring image is formed. The luminance distribution I (x) of the Newton ring image is given by the following equation as a radius of curvature R, a distance x from the center, and a measurement wavelength λ.

[0039]

(Equation 3)

First, the center of the interference fringes and the radius of curvature R are determined.
Next, if the distance x of the virtual vertex Pz from the interference fringe center is obtained, the luminance signal of the virtual vertex Pz can be estimated from Expression (3). By performing this process for each N images, the phase and height information of the virtual vertex Pz is calculated, and the information is calculated from the difference between the virtual vertex Pz height of the zirconia portion 502 and the center vertex Pf of the optical fiber 501. A step can be determined.

FIG. 6 shows another embodiment. This embodiment is obtained by adding a robot hand unit for automatically handling a ferrule to be inspected to the embodiment embodiment shown in FIG. 1 earlier, and the principle of inspection of the polished surface is the same. explain. In FIG. 6, 60
0 is an optical code, and 600a is a ferrule to be inspected. 600
b is the other end ferrule, 601 is a pallet, 601a, 6
01b is a ferrule gripper, 601c is a pulley, 602
Is a white light source emission head, 603 is an automatic transport mechanism, 604
605 is a V-groove, 605b is a holding plate, 605c is a coil spring, 605d is a zirconia flat plate, 605e.
Is a stopper, 606 is an air cylinder for holding tool up and down, 60
6a is an air pipe, 607 is a computer, 608 is a white light source,
609 is a magnifying objective lens, 610 is a CCD element, 610
a is a CCD controller, 611 is a mechanical slide mechanism for an interference filter, 611a is an air pipe, 612 is an interference filter, 613 is an interference objective lens, 614 is a mechanical slide mechanism for an objective lens, 614a is an air pipe, and 615 is a vibration control. A base platen, 616 is a minute displacement stage, and 617 is an X stage.

The ferrule 600a to be inspected attached to the optical cord 600 and the ferrule 600b at the other end are ferrule grippers 601a and 601b of a dedicated pallet 601.
Is set to Ferrule gripper 6 of pallet 601
The set has been other end ferrule 600b to 01b white light emitting head 602 for incident white light is disposed.

After the ferrule 600a to be inspected placed on the pallet 601 mounted on the automatic transport mechanism 603 is gripped by the robot hand 604, the ferrule 600a is drawn toward the optical meter and inserted into the V groove 605a of the ferrule alignment / grip 605. . The method of fixing and holding the ferrule 600a to be inspected is as follows.
Similar to the method described in the embodiment of FIG. 1, the ferrule 600a to be inspected is brought into contact with a stopper 605e having a circular opening at the tip end of the V groove 605a and inserted into the V groove 605a. After that, a solenoid valve (not shown) is controlled by a command from the computer 607 to exhaust air from the presser holder vertical air cylinder 606. Thus, the flat plate portion 605d made of zirconia attached to the holding plate 605b fixes the ferrule 600a to be inspected in the V groove 605a by the pressing force of the coil spring 605c, and the positioning in the XY directions and the rough positioning in the Z direction in FIG. 6 are completed. I do. The optical meter is initially set in the magnifying optical meter, and illumination light from the white light source 608 illuminates the end face of the ferrule 600a to be inspected via the magnifying objective lens 609. This ferrule 60 to be inspected
The reflected light from the end face 0a is imaged on the CCD element 610.
The enlarged image formed on the CCD element 610 is captured on an image processing board (not shown) mounted in the computer 607 via the CCD controller 610a. This enlarged image is subjected to image enhancement processing such as density conversion and differentiation processing, and this enhanced image together with the original image is stored in the storage device of the computer 607. Next, for switching to the interferometer, the computer 607 controls an electromagnetic valve (not shown) for turning on / off the air, and injects air into the mechanical slide mechanism 611 for the interference filter via the air pipe 611a. The interference filter 612 is inserted into the illumination optical path Oin, and air is injected into the mechanical slide mechanism 614 for the objective lens via the air pipe 614a to automatically switch from the enlarged objective lens 609 to the interference objective lens 613. FIG. 6 shows a state in which an interferometer is configured. White light emitted from a white light source 608 is converted into monochromatic light by an interference filter 612, and is then transmitted through an interference objective lens 613 to the inspection target ferrule 600 a. The end face is illuminated. The interference between the reflected light from the end face of the inspection target ferrule 600a and the reference mirror in the interference objective lens 613 forms concentric interference fringes on the CCD element 610. This image is C
It is loaded on an image processing board (not shown) in the computer 607 via the CD controller 610a, and the radius of curvature, the vertex deviation, and the step are calculated using the inspection principle described in the embodiment of FIG. After the calculation, a solenoid valve (not shown) is controlled by a command from the computer 607 to inject air into the air cylinder 606 for holding and lowering the holding tool through the air pipe 606a, lift the holding plate 605b, and lift the ferrule 600a to be inspected. Release the fixation. The robot hand 604 is
The inspection target ferrule 600a is gripped and the pallet 6
After the transfer in the 01 direction, the pallet 601 is inserted into the ferrule holding portion 601a. At this time, the pulley 601c on the pallet 601 moves the optical cord 600 in the optical cord winding direction.
And the optical cord 600 is operated so as not to bend. Also, as in the embodiment of FIG. 1, the optical meter, the stage, and the gripper are set on the anti-vibration base plate 615 to minimize the influence of external vibration.

[0044]

As described above, according to the present invention, both the magnifying optical meter and the interferometric optical meter can be constituted only by switching the filter and the objective lens, and the conventional measuring method is performed by combining individual measuring instruments. Equipment and inspection costs can be reduced as compared with the measurement method. In addition, because it is a configuration that performs image analysis of magnified images and interference fringes acquired by the magnifying optical meter and the interferometer, it is one digit higher than the conventional measuring method that combines a high-quality inspection by non-contact inspection and an individual measuring instrument. As described above, the inspection time can be reduced. In addition, the robot hand mechanism, auto-focus function, and automatic switching of the objective lens and interference filter can automate inspection, reduce inspection costs, and increase
High reliability inspection is possible. In addition, a dedicated interference fringe program can be used to speed up the measurement of vertex misalignment. In addition, a high-precision step detection method using fringe scanning and curvature radius measurement are performed, and polished surface shape batch high-precision inspection and flaw image enhancement processing Facilitates the identification of scratches.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a configuration of an optical system according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram of measurement of a radius of curvature according to an embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a vertex shift according to an embodiment of the present invention.

FIG. 5 is an explanatory diagram showing step detection according to an embodiment of the present invention.

FIG. 6 is a perspective view showing another embodiment of the present invention.

FIG. 7 is a configuration diagram showing a curvature radius measuring method using a conventional surface roughness meter.

FIG. 8 is an explanatory diagram showing an example of a chart output measured by the surface roughness meter of FIG. 7;

FIG. 9 is a configuration diagram showing a method of measuring a curvature radius and a vertex shift using a conventional microscope and a parallel glass plate.

FIG. 10 is an explanatory diagram showing a method of measuring a radius of curvature and a vertex shift using a conventional microscope and a parallel glass plate.

[Description of Signs] 100: Optical cord, 100a: Ferrule to be inspected, 1
00b: other end ferrule, 101: X stage, 102
... Small displacement stage, 102a ... Small displacement stage controller, 103 ... Ferrule alignment / gripping tool, 103a
... V-groove made of zirconia, 103b ... Holding plate, 103c ...
Coil spring, 103d: flat plate made of zirconia, 103
e: stopper, 104: slide mechanism for holding plate up and down, 1
04a ... air piping, 105 ... external white light source, 105a ...
Bundle fiber, 105b emission head, 106 interference filter, 107 magnifying objective lens, 108 mechanical slide mechanism for objective lens, 108a air piping, 10
9: interference objective lens, 109a: reference mirror, 110: mechanical slide mechanism for interference filter, 110a: air pipe, 111: anti-vibration base, 112: white light source, 112a
... light amount adjuster, 113 half mirror, 114 CCD device, 114a CDD controller, 115 computer
116: lens holder, 117: other end ferrule fixing jig, 301: interference fringe image, 302: optical fiber image 401
Inspection ferrule, 402: V-groove, 403: interference objective lens, 404a, 404b, 404c: interference fringe center,
405: locus circle, 406: optical fiber, 501: optical fiber, 502: zirconia part, 600: optical cord, 60
0a: Ferrule to be inspected, 600b: Ferrule at the other end, 601: Pallet, 601a, 601b: Ferrule gripper, 601c: Pulley, 602: White light emitting head, 603: Automatic transport mechanism, 604: Robot hand, 605: Ferrule alignment・ Grip, 605a ... V
Groove, 605b ... holding plate, 605c ... coil spring, 605
d: flat plate made of zirconia, 605e: stopper, 60
6 ... Air cylinder for holding tool up and down, 606a ... Air piping,
607: Computer, 608: White light source, 609: Magnifying objective lens, 610: CCD element, 610a: CCD controller, 611: Mechanical slide mechanism for interference filter,
611a ... air piping, 612 ... interference filter, 613 ...
Interference objective lens, 614: mechanical slide mechanism for objective lens, 614a: air pipe, 615: anti-vibration table base, 61
6 ... Small displacement stage, 617 ... X stage, 700 ...
Inspection ferrule, 701: surface plate, 702: XY position adjustment mechanism, 703: ferrule mounting jig, 704: surface roughness meter, 705: stylus, 706: arm, 707: position detector, 708: chart, 709 ... optical fiber, 71
0: core, 711: zirconia, 800: zirconia,
Reference numeral 801 denotes an optical fiber, 900 denotes a microscope, 901 denotes an objective lens, 902 denotes a transparent parallel plate, 903 denotes a sample stage, 904 denotes a ferrule holder, 905 denotes a ferrule to be inspected, 906 denotes a white light source, and 907 denotes a half mirror.
8: CCD, 909: CCD controller, 910: Monitor, 911: Interference fringe, 912: Optical fiber image.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-8-2324052 (JP, A) JP-A-6-26812 (JP, A) JP-A-5-196452 (JP, A) JP-A-5-196452 118832 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01B 11/00-11/30 102 G01M 11/00-11/08 G01N 21/84-21/958

Claims (3)

(57) [Claims] 1. An automatic polishing apparatus for a polished surface of a ferrule for an optical connector attached to an end of an optical cord or an end of an optical fiber, comprising a white light source and a half mirror sequentially in a traveling direction of the illumination light, wherein the illumination light passes through the half mirror. The magnifying lens has a magnifying lens in a direction deflected and advanced by 90 degrees, and a CCD element is arranged at a position where the reflected light from the ferrule to be inspected arranged at the tip of the magnifying lens is imaged through the magnifying objective lens and the half mirror. A magnifying optical meter for forming an end face image of the ferrule to be inspected, and an interference filter inserted on the illumination optical path between the white light source and the half mirror, and switching the magnifying objective lens to the interference objective lens by mechanical switching means to cause interference. An optical meter is configured, and a ferrule to be inspected is positioned at the optical axis center of the magnifying and interferometric optical meter and at the focal position of the magnifying objective lens. A means for aligning and holding the ferrule and a micro-displacement stage for applying a displacement in the direction of the optical axis; A frame memory for A / D converting and accumulating an electric signal from the CCD element which has taken the magnified image and the interference fringe image generated by the magnifying and interferometer image, and an image processing unit for analyzing the interference fringe image; Then, from the four or more interference fringe images obtained by imparting the fine displacement four or more times in the optical axis direction by the fine displacement stage, the optical axis direction of the optical fiber vertex of the optical fiber center axis and the imaginary vertex of the zirconia portion is obtained. Step, which is the deviation of
The radius of curvature of the convex spherical polished surface, the vertex deviation, which is the deviation between the optical fiber center and the vertices of the polished surface in the vertical plane, is automatically inspected, and the end face scratches and dirt are observed by the magnified optical meter image. Characteristic optical connector polished surface automatic inspection device. 2. A means for mechanically handling the ferrule to be inspected at the center of the optical axis and the focal position of the interferometer and the magnifying optical meter, and after the inspection, mechanically handling the ferrule to be inspected and returning the ferrule to the initial position. The optical connector polished surface automatic inspection apparatus according to claim 1, wherein: 3. A step of detecting the center of an interference fringe and the center of an optical fiber from an interference fringe image formed on a CCD element using an interference optical meter of the automatic optical connector polished surface inspection apparatus according to claim 1. 2. A step of correcting an angular deviation between an optical axis of an optical meter and an optical fiber center axis of a ferrule to be inspected, and calculating a vertex deviation from a correction value obtained by the correction and the center of the interference fringes. Calculating a radius of curvature from four or more interference fringe images obtained by giving a minute displacement four or more times using a minute displacement stage of the optical connector polished surface automatic inspection apparatus described above, and an optical fiber end face and a zirconia part. Calculating a phase of the zirconia portion and detecting a step from the height of the vertex of the zirconia portion and the height of the vertex of the end face of the optical fiber.