JPH0942920A - Device for automatically checking polished surface of optical connector and method of checking polished surface of optical connector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To check a shape of a polished surface at a high speed with a high degree of accuracy without damaging a sample, by constituting both magnifying optical system and interference optical system only by changing over a filter and an objective lens. SOLUTION: A white light beam emitted from an white light source 112 is converted by an interference filter 106 into a monochromatic light beam which is then applied onto an end face of a ferrule 100a to be checked, through an interference objective lens 109. A reflected beam from the end face of the ferrule 100a interferes with a reference mirror 1.09a in the interference objective lens 109 so as to form concentric circular interference fringes on a CCD element 114. This interference image is taken into an image processing board in a computer 115 through a CCD controller 114a so as to speed up the measurement of a deviation of an apex. Further, a highly accurate step detecting method using a fringe scanning process and the measurement of a radius of curvature are carried out, it is thereby possible to facilitate the checking of a shape of a polished surface in batch, the recognition of a damage by intensifying an image of the damage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing surface automatic inspection device and a polishing surface inspection method for an optical connector used for optical communication.

[0002]

2. Description of the Related Art An optical connector used in an optical communication system is required to have a low connection loss and a low reflection in an optical connecting portion. To achieve this, the end face of the optical connector is usually precision-polished into a convex spherical shape. Particularly in recent years, there has been a strong demand for lower reflection at the connecting portion of the optical connector, and a return loss of 40 dB or more is required. In order to meet such requirements, it is important to use a polishing technique that achieves ultra-low reflection and shape inspection of the polished surface. 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 an optical fiber center of 50 μm or less and a polishing vertex (hereinafter referred to as a vertex deviation), 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 is free from scratches and stains.

On the other hand, in the past, the individual measurement was separately carried out by using individual measuring instruments, and the level difference measurement requiring high-precision measurement of several tens of nm was not the total number but the sampling inspection. The measuring method using a conventional measuring instrument will be sequentially described below with reference to the drawings.

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

In FIG. 7, reference numeral 700 is a ferrule to be inspected, 701 is a surface plate, 702 is an XY position adjusting mechanism, and 703.
Is a ferrule mounting 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. Further, in FIG. 8, reference numeral 800 is zirconia, 801 is an optical fiber, and 802 is an output chart.

In FIG. 7A, the ferrule 700 to be inspected is set on the ferrule mounting jig 703 provided on the XY position adjusting mechanism 702 on the surface plate 701. Next, the stylus 705 of the surface roughness meter 704 is connected to the ferrule 70 to be inspected.
When the arm 706 is lowered in the Z-axis direction until it slightly contacts 0 (Z-axis direction), 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 the position detector 707 and amplified by the amplifier to obtain the Z-direction enlarged displacement δz. If the displacement L obtained from the velocity V is plotted on the horizontal axis and δz is plotted on the vertical axis on the chart 708, an enlarged profile of the ferrule 700 to be inspected is obtained. From this profile, the ferrule 700 to be inspected is obtained.
The radius of curvature and the step can be calculated.

FIG. 8 shows an output example of the chart 708. d
Is the measured length and h is the measured length d.
Given the height 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. Regarding the step, the zirconia 8 on the optical fiber central axis Of is used.
It can be measured by reading the difference between the virtual vertex Pz of the polishing surface of 00 and the vertex Pf of the optical fiber 801 from the output chart 802.

However, this measuring method has a drawback that it may damage the sample because it is of a contact type, and that it takes time to measure because it is a stylus type. Further, 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. 7B. , Need to scan. However, because of the visual positioning, the core 710 of the optical fiber 709 is
It is impossible to position the stylus 705 at the center position of the. If a surface roughness meter for three-dimensional shape measurement, which 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 it at the center of the optical fiber, but it takes several tens of minutes or more for measurement. , Cannot be used as an online measurement or 100% inspection measuring instrument. Further, in such a measuring method, in order to detect the vertex deviation which is the remaining inspection item, it is necessary to highly accurately attach the ferrule attaching jig to the stylus scanning axis. From this point of view, the vertex shift detection by this method is practically impossible, and is not actually performed at present. Therefore, in order to detect the apex shift, it must be used in combination with a measuring device described later.

FIG. 9 shows a conventional example of detecting a radius of curvature and a deviation of a vertex by forming interference fringes by using a microscope and a parallel glass plate, which is an example of a conventional inspection method. In FIG. 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 gripping tool, 9
Reference numeral 05 is an inspection target ferrule, 906 is a white light source, and 907.
Is a half mirror, 908 is a CCD, 909 is a CCD controller, 910 is a monitor, 911 is an interference fringe, and 912 is an optical fiber image.

A transparent parallel plate 902 is arranged in front of the objective lens 901 of the microscope 900, and the sample stage 90
The ferrule 9 to be inspected on the ferrule holding tool 904 on
05 is set so that its 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, is deflected by the half mirror 907 by 90 degrees, and then passes through the objective lens 901.
The end faces of the parallel plate 902 and the inspection target ferrule 905 are irradiated. In such a state, so-called Newton's ring interference fringes are generated between the parallel plate 902 and the inspection target ferrule 905 polished into a convex spherical surface. The interference fringes are ring fringes corresponding to contour lines at 1/2 pitch of the measurement wavelength λ. This interference fringe is used for the objective lens 901 and the half mirror 90.
The light is received by the CCD 908 via 7.

The signal received by the CCD 908 is the CCD
It is output to the monitor 910 via the controller 909. An optical fiber image 912 is simultaneously displayed on the monitor 910 together with the interference fringe 911. The diameter of the interference fringe 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, b (a> b) of the adjacent interference fringes and the height difference h (h = λ / 2) between the interference fringes.

[0014]

[Equation 2]

Next, the vertex shift according to this conventional example will be described. 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 inspection target ferrule 905, the polishing apex and the interference fringe apex (Ix, Iy) coincide with each other. Therefore, the vertex shift, which is the deviation between the polishing vertex and the center (Cx, Cy) of the optical fiber 912, is the center of the interference fringe (Ix, Iy) and the center of the optical fiber 912 (Cx, C).
It can be obtained by calculating the deviation between y). 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 center axis Of of the ferrule 905 to be inspected, the center C of the interference fringe moves to C ′. The center of the interference fringe does not mean the apex of the polished surface. Therefore, simply
It is not possible to obtain the vertex shift from the difference between the center (Cx, Cy) of 12 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 to measure three or more points, the rotation center is obtained from the coordinates of these measurement points, and the inclination component is corrected. Shinya et al., 1988 IEICE Spring National Convention C-558, (1988) 19
One. However, in such a measuring method, it is necessary to rotate and measure the ferrule by 3 points or more, so that it takes a long measuring time.
05 and a parallel flat plate 902 are applied with a certain pressing force, and when the inspection target ferrule 905 is rotated, the parallel flat plate 902 and the inspection target ferrule 905 are separated by a force equal to or greater than the pressing force and rotated in that state, and then both are brought into contact with each other. It requires complicated handling of the sample. Furthermore, since the contact-type measurement method is used, the sample may be damaged, and the contact state between the ferrule 905 to be inspected and the parallel plate 902 before and after the rotation cannot be said to be the same. Since it is not always constant, there are drawbacks such as measurement error. Further, since the step cannot be measured by this measuring method, it is necessary to measure the step using a measuring device other than this measuring device as described in the conventional example.

[0016]

As described above, since the conventional measuring method is basically the contact type measuring method, there is a drawback that the sample may be damaged and the sample must be attached with high accuracy. There is. Also, in the conventional method,
Since it takes a long time to perform measurement, online (ONLINE) or 100% inspection cannot be performed at the actual assembly site, so there is a problem that sufficient quality cannot be guaranteed. Further, since a plurality of measuring instruments are used, there is a problem that inspection time and inspection cost are required.

The present invention has been made in view of the above circumstances, and is capable of inspecting the shape of the polishing surface at high speed and with high accuracy without damaging the sample, such as scratches, and is economical. An object is to provide an inspection device and an optical connector polishing surface inspection method.

[0018]

In order to achieve the above object, the present invention illuminates a white light source and a half mirror in an apparatus for automatically inspecting a polished surface of a ferrule for an optical connector attached to an optical cord end or an optical fiber core end. It has sequentially in the light traveling direction, and this illumination light is deflected 90 degrees through the half mirror.
A magnifying objective lens is provided in the traveling direction, and the reflected light from the ferrule to be inspected arranged at the tip of the magnifying objective lens is imaged through the magnifying objective lens and the half mirror at a position C
A magnifying optics for arranging a CD element to form an end face image of a ferrule to be inspected, and an interference filter is automatically or manually inserted in the illumination optical path between the white light source and the half mirror described above. An interferometer is constructed by switching to an interference objective lens at the same position as the axial center position by means of a slide type transfer mechanism, etc., and the ferrule to be inspected is aligned at the focal position of these two magnifying and interference objective lenses.
High resolution on the order of 10 nm and 100 μm composed of an alignment part such as a V-groove for positioning, a ferrule alignment / holding mechanism for fixing the ferrule to be inspected by spring force, etc., and a piezo for giving displacement in the optical axis direction of the optical meter. The micro-displacement stage which has a high dynamic range is used, and by using the micro-displacement stage and the differential value and the contrast value of the image signal obtained by the CCD element, the focus positions of the magnifying and interference objective lenses are auto-focused respectively. Then, a frame memory for A / D (analog / digital) converting and accumulating the electric signal from the CCD device that captured the magnified image and the interference fringe image generated by the magnifying and interference optics and the image processing for image analysis of the interference fringe image With a micro-displacement stage, micro-transfer is performed in the optical axis direction of the optical meter 1/8 or less of the used wavelength λ and 4 times or more. From the obtained four or more interference fringe images, the difference in the optical axis direction between the optical fiber apex of the optical fiber center axis and the virtual apex of the zirconia portion, the radius of curvature of the convex spherical surface, and the optical fiber center An optical meter between the apexes of the polishing surface is inspected for an apex deviation which is a deviation in a plane perpendicular to the optical axis direction, and an end surface scratch and stain are observed by an enlarged image by the magnifying optics. Optical connector polished surface that has the function of automatically mechanically handling the ferrule to be inspected at the center of the optical axis and the focal position of the optics and magnifying optical meter, and then returning the ferrule to be inspected to the initial position automatically after the inspection is completed. It is characterized by being an automatic inspection device. Further, in the above-mentioned interferometer, the center of the interference fringe and the center of the optical fiber are detected from the interference fringe image formed on the CCD element. Corrects the angular deviation between the optical axis of the interferometer and the optical fiber center axis of the ferrule to be inspected, calculates the vertex deviation from this correction value and the center of the interference fringe, and further finely transfers it four times or more using the minute displacement stage. The radius of curvature is calculated from the obtained four or more interference fringe images, and the phase of the optical fiber end face and the zirconia portion is calculated and converted into height information, and the polishing vertex height of the zirconia portion and the height of the optical fiber end face are calculated. It is an optical connector polishing surface inspection method characterized by detecting a step from the difference, and the inspection time can be shortened by one digit or more compared with the conventional contact type measurement method which is performed by combining individual measuring instruments. Since it is a non-contact type, it does not damage the surface to be inspected, so high-quality inspection can be performed. The robot hand mechanism, autofocus function, automatic switching of the objective lens and interference filter enables automatic inspection. Of the reduction of inspection costs Hakare and high precision and so attained
It differs from the prior art in that it can perform highly reliable inspection.

[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 this embodiment. In the figure, 100 is 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 to be inspected 100a, 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 / holding 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 the end of the holding plate 103b, 103e is a stopper, 104 is the top and bottom of the holding plate. Slide mechanism, 104a for air piping, 105 for an external white light source, 105a for a bundle fiber, 105b for an emission head, 106 for an interference filter, 107 for 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 half mirror (FIG. 2), 114 is a CCD element, 114a is a CCD controller, 115 is a calculator, 116 is a lens holder,
117 is a ferrule fixing jig at the other end.

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

First, the ferrule 100a to be inspected, which is polished into a convex spherical shape, is set on the ferrule aligning / grasping tool 103 on the micro 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 / holding tool 103. Ferrule aligning / holding tool 103
Is the ferrule 100a to be inspected and 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 the holding plate 103b having the V groove 103a made of zirconia and the flat plate portion 103d made of zirconia. The ferrule 100a to be inspected is fixed by inserting the ferrule 100a to be inspected into the ferrule aligning / grasping tool 103, exhausting the air from the holding plate up / down slide mechanism 104, and providing a coil spring provided at the end of the holding plate 103b. The elastic force of 103c is used. Further, the ferrule 100a to be inspected is removed by injecting air through the holding plate up-and-down slide mechanism 104.
03b by lifting.

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 emitting head 105b, and the other end ferrule fixing jig 117.
It is incident on the other end ferrule 100b set to. By injecting white light from the other end ferrule 100b, the detection of the center of the optical fiber of the inspection target ferrule 100a at the time of image processing can be simplified and the disconnection of the optical fiber in the optical cord 100 can be checked. In the case of a so-called pigtail type in which only the inspection target ferrule 100a is attached to the optical cord 100 and the other end ferrule 100b is not provided, the optical fiber center position is measured in advance and this position is set as the default value of the optical fiber center position. By setting it in the inspection program, it is possible to inspect as in the case of the optical cord with ferrule for both-end optical connector. In this case, it is not possible to check the above-mentioned optical fiber breakage.

As an optical meter to be used for inspection, two optical meters, a magnifying optical meter for white illumination (same as the structure of an ordinary metallurgical microscope) and an interference optical meter, can be configured. The magnifying optics is configured by removing the interference filter 106 from the illumination optical path Oin and setting the magnifying objective lens 107 on the objective lens, and then switching the objective lens to the interference objective lens 109 by the objective lens mechanical slide mechanism 108. At the same time, the interference filter 106 is inserted into the illumination optical path Oin by the interference filter mechanical slide mechanism 110 to form an interference optical meter. In addition to the slide mechanism type switching system described here, a rotary type switching system using an electric revolver can also be considered as the objective lens switching system. However, the slide mechanism type switching method has an advantage that the optical axis Oray of the optical meter is low and strong against external vibration and the like because the mechanical interference region at the time of switching can be made smaller than that of the rotating type. The optical meter, the X stage 101, the minute displacement stage 102, and the ferrule aligning / grasping tool 103 described above are set on the vibration isolation table surface plate 111 in order to remove the influence of external vibration as much as possible.

FIG. 2 shows the structure of the optical meter. The white light is adjusted to have an appropriate light quantity by the light quantity adjuster 112 a and is emitted from the white light source 112. The magnifying optics is Half Mira 11
3, the magnifying objective lens 107 and the CCD element 114 are provided.
It is configured by inserting it into the in and switching the magnifying objective lens 107 to the interference objective lens 109. In the interference optics, the reflected light Pm of the reference mirror 109a in the interference objective lens 109 and the reflected light Pr of the inspection target ferrule 100a.
Are made to interfere with each other to form an interference fringe image of the polished end surface of the inspection target ferrule 100a on the CCD element 114. In FIG. 2, a finite system optical meter has been described. When the optical meter is an infinite system, the CCD element 114 and the half mirror 11 shown in FIG.
An imaging lens is arranged between the three lenses, and the objective lens also has an infinite system lens for imaging. However, in the present embodiment, the imaged image is processed and inspected. Can be an infinite system or a finite system.

Next, the entire inspection will be described with reference to FIG. 1. First, the inspection target ferrule 100a is manually set in the V groove 103a in the ferrule aligning / holding tool 103. At this time, air is injected into the holding plate up-and-down slide mechanism 104 through the air pipe 104a, and the ferrule 100a to be inspected is placed in the V groove 1 while the holding plate 103b is lifted.
V groove 1 in a state of abutting against a stopper 103e having a circular opening (about φ0.8 to 1.5) at the tip of 03a.
Insert into 03a. By this abutting, rough positioning of the Z axis is performed. After that, the slide mechanism 10 for holding the presser plate up and down
4 air is exhausted and the coil spring 103 of the pressing plate 103b is discharged.
The ferrule 100a to be inspected is aligned and fixed in the V groove 103a by the pressing force of c, and positioning is performed in the XY directions in the drawing.

The optical meter is initially set in the magnifying optical meter, for example, and the illumination light from the white light source 112 illuminates the end surface of the inspection target ferrule 100a set through the magnifying objective lens 107. The reflected light from the end surface of the ferrule 100a to be inspected is imaged on the CCD element 114, and the computer 115 is operated via the CCD controller 114a.
It is captured on an image processing board (not shown) mounted inside. This magnified image is subjected to image enhancement processing such as density conversion and differential processing, and the enhanced image is stored in the storage device of the computer 115 together with the original image. Next, in order to switch to the interferometer, a computer 115 controls a solenoid valve (not shown) for turning the air on and off, and air is injected into the mechanical slide mechanism 110 for the interference filter through the air pipe 110a. The interference filter 106 to the illumination optical path Oin
And the objective mechanical slide mechanism 108 is injecting air through the air pipe 108a to switch from the magnifying objective lens 107 to the interference objective lens 109. In this configuration, the white light emitted from the white light source 112 is converted into monochromatic light by the interference filter 106,
The ferrule 10 to be inspected via the interference objective lens 109.
Irradiate the end face of 0a, and the ferrule 1 to be inspected as described above
Due to the interference between the reflected light from the end surface of 00a and the reference mirror 109a in the interference objective lens 109, concentric interference fringes are imaged on the CCD element 114. This 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 shift, and the step are calculated using the detection principle described later.

In the present embodiment, the ferrule aligning / holding tool 103 is attached to the micro displacement stage 102.
The micro-displacement stage 102 is a piezo-drive type stage having a displacement magnifying mechanism using a mechanical lever, and the micro-displacement stage controller 102a feedback-controls the displacement so that the displacement is constant.
m, resolution is about 10 nm. The micro displacement stage 102 is used to realize four functions. First, by absorbing the mounting error of the optical meter main body and the ferrule alignment / grasping tool 103 in the optical axis Oray direction, a mounting error of the ferrule alignment / grasping tool 103 or the like of about several tens of μm can be tolerated. The point is that the device can be easily assembled, adjusted, and maintained.

Next is the absorption of the mounting error between the lenses. In this embodiment, two confocal objective lenses 107 and 109 are used. Normally, the objective lens is attached by a screw interface, so even if the two objective lenses are attached to the lens holder 116 with high precision, 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 fine displacement stage 102 is driven in the Z direction by a piezo to measure the focal position of each objective lens individually, and each 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, which is not only easy to assemble, adjust, and maintain, but also has an economical merit that a commercially available objective lens can be used.

Next is the autofocus function. Even if each focal length is set as described above, in the actual use stage, it is several μm in the focal direction (Z direction) due to temperature change.
It changes and the image becomes out of focus. To solve this, C
Since the fine displacement stage 102 can be controlled to be in autofocus based on the image signal obtained by the CD element 114, stable inspection can be performed.
As an example of autofocusing the magnified image, a position at which the differential value of the edge portion of the optical fiber end face on a certain scanning line is detected while the displacement is given by the minute displacement stage 102, and the maximum value is given Small displacement stage 102
This can be realized by positioning the fine displacement stage 102 again at the displacement position of. Also, for auto-focusing of the interference fringe image, while similarly displacing the fine displacement stage 102, the contrast value of a certain scanning line is obtained, and the displacement position of the fine displacement stage 102 at the time when the maximum contrast is given is again finely adjusted. This can be easily performed by positioning the displacement stage 102.

Finally, there is a step measuring method using a stripe 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 by using this minute displacement stage 102.

The minute displacement stage 102 described above is used.
Are controlled by the computer 115 via the minute displacement stage controller 102a. The detection method of each item will be briefly described below.

First, the method of detecting the radius of curvature will be described with reference to FIG. The concentric circles shown in FIG.
This is a representation of the interference fringes on the end face of 00a, where 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 optics, the center (Ix, Iy) of the interference fringe and the interference fringe radii r ₁ , ..., R _n of the interference fringe image 301 are calculated based on the center (Ix, Iy) of the interference fringe. If the interference fringe radii a and b (a> b) adjacent to each other are sequentially detected and the adjacent fringe radii are used, the calculation can be easily performed by the above-described formula (2). Further, it is possible to easily obtain an average radius of curvature from three or more interference fringe radii.

Next, the measurement of the vertex displacement will be described with reference to FIG. In FIG. 4, 401 is a ferrule to be inspected, 40
2 is a V groove, 403 is an interference objective lens, and 404a and 404.
Reference numerals b and 404c are centers of interference fringes, 405 is a locus circle, and 406 is an optical fiber.

The measurement of the vertex shift in this embodiment is fundamentally different from the conventional example in that it can be measured in a non-contact manner because the interference fringes are formed using the interference objective lens 403.
To measure the deviation of the vertex, the distance between the center of the optical fiber 406 and the polishing vertex may be obtained. However, as described in the measurement of the vertex shift of the conventional example (FIGS. 9 and 10), when the inclination φ exists between the optical fiber center axis Of of the inspected ferrule 401 and the optical axis Oray of the interferometer, at least,
Rotate the ferrule three or more times to center the interference fringes 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 inspection target ferrule and the optical axis Oray of the optical meter is constant even if the inspection target ferrule 401 is replaced. Therefore, by measuring the coordinate value of the rotation center Cr in advance and setting it in the inspection program, the vertex deviation can be obtained from the distance between the center of the interference fringe and the coordinate value of the rotation center Cr. Therefore, the vertex deviation can be measured by one measurement. You can

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 portion cut along the optical axis Of, where 501 is an optical fiber and 502 is a zirconia portion.

A stripe scanning method is used for the step detection method. Step δ
Is the central 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.
It is a deviation from the virtual vertex Pz of 2. In the fringe scanning method, one cycle (λ / 2) of interference fringes is divided into N, and a transfer amount corresponding to 1 / N of λ / 2 is moved in the optical axis Oray direction using the minute displacement stage 102 shown in FIG. Transfer. The micro displacement stage controller 102a performs feedback control so that the displacement of the micro displacement stage 102 becomes constant, and the computer 11
In response to the command from 5, the micro displacement stage 102 is transferred N times. Generally, N = 4 is often used because of the calculation time.

The phase of each point on the end surface of the ferrule to be inspected is calculated from the image signal acquired for each scan, and the height of the central vertex Pf of the optical fiber 501 and the zirconia portion 50 are calculated from this.
If the height of the apex Pz of 2 is calculated, a step (δ = Pz−P
f) can be calculated.

First, the central vertex Pf of the optical fiber 501.
The height can be easily obtained by obtaining the phase based on N image signals obtained by moving the fine 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 missing in a state where there is a so-called step difference that the optical fiber 501 pulls in. 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, it forms a so-called Newton's ring image. The luminance distribution I (x) of the Newton's ring image is given by the following equation as the radius of curvature R, the distance x from the center, and the measurement wavelength λ.

[0039]

(Equation 3)

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

FIG. 6 shows another embodiment. In the present embodiment, a robot hand unit for automatically handling the ferrule to be inspected is added to the embodiment shown in FIG. 1, and since the principle of inspecting the polished surface is the same, the operation of the robot hand unit will be mainly described. explain. In FIG. 6, 60
0 is an optical code, 600a is a ferrule to be inspected. 600
b is the other end ferrule, 601 is a pallet, 601a, 6
01b is a ferrule grip, 601c is a pulley, 602
Is a white light source emitting head, 603 is an automatic transport mechanism, 604
Is a robot hand, 605 is a ferrule aligning / holding tool, 605a is a V groove, 605b is a holding plate, 605c is a coil spring, 605d is a flat plate portion made of zirconia, 605e.
Is a stopper, 606 is an air cylinder for lifting the presser foot, 60
6a is an air pipe, 607 is a computer, 608 is a white light source,
Reference numeral 609 is a magnifying objective lens, 610 is a CCD element, and 610.
a is a CCD controller, 611 is a mechanical slide mechanism for interference filters, 611a is air piping, 612 is an interference filter, 613 is an interference objective lens, 614 is a mechanical slide mechanism for objective lenses, 614a is air piping, and 615 is vibration isolation. A base table, 616 is a minute displacement stage, and 617 is an X stage.

The ferrule 600a to be inspected and the other end ferrule 600b attached to the optical cord 600 are ferrule gripping portions 601a and 601b of a dedicated pallet 601.
Is set to Ferrule grip 6 of pallet 601
A white light source emitting head 602 for injecting white light is arranged on the entire surface of the other end ferrule 600b set to 01b, as in the above embodiment.

After the ferrule 600a to be inspected installed on the pallet 601 mounted on the automatic transport mechanism 603 is gripped by the robot hand 604, it is drawn into the optical meter side and inserted into the V groove 605a of the ferrule aligning / gripping tool 605. . The method of fixing and gripping the ferrule 600a to be inspected is
Similar to the method described in the embodiment of FIG. 1, the ferrule 600a to be inspected is inserted into the V groove 605a by abutting against the stopper 605e having a circular opening at the tip of the V groove 605a. After that, a solenoid valve (not shown) is controlled by a command from the computer 607 to exhaust the air from the presser foot up / down air cylinder 606. Thereby, 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 direction and the rough positioning in the Z direction in FIG. 6 are completed. To do. The optical meter is initially set in the magnifying optical meter, and the illumination light from the white light source 608 illuminates the end surface of the ferrule 600a to be inspected via the magnifying objective lens 609. This inspection target ferrule 60
The reflected light from the end surface of 0a is imaged on the CCD element 610.
The magnified 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 magnified image is subjected to image enhancement processing such as density conversion and differential processing, and the enhanced image is stored in the storage device of the computer 607 together with the original image. Next, when switching to the interference optical meter, a computer 607 controls an electromagnetic valve (not shown) for turning on / off the air, and injects air into the mechanical slide mechanism for interference filter 611 through 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 for objective lens 614 through the air pipe 614a to automatically switch from the magnifying objective lens 609 to the interference objective lens 613. Note that FIG. 6 shows a state in which an interferometer is configured, in which white light emitted from the white light source 608 is converted into monochromatic light by the interference filter 612, and then the white light emitted from the white light source 608 is transferred to the inspection target ferrule 600a via the interference objective lens 613. Irradiate the end face. Due to the interference between the reflected light from the end face of the ferrule 600a to be inspected and the reference mirror in the interference objective lens 613, concentric interference fringes are imaged on the CCD element 610. This image is C
It is loaded onto an image processing board (not shown) in the computer 607 through the CD controller 610a, and the radius of curvature, vertex deviation, and step are calculated using the inspection principle described in the embodiment example of FIG. After the calculation, a solenoid valve (not shown) is controlled by a command from the computer 607 to inject air into the presser foot upper / lower air cylinder 606 through the air pipe 606a, lift the presser plate 605b, and remove the ferrule 600a to be inspected. Release the lock. The robot hand 604 is
Grasping the ferrule 600a to be inspected, the pallet 6
After transferring in the 01 direction, the pallet 601 is inserted into the ferrule gripping portion 601a. At this time, the pulley 601c on the pallet 601 moves the optical cord 600 in the optical cord winding direction.
To pull the optical cord 600 so that it does not bend. Further, as in the embodiment shown in FIG. 1, the optical meter, the stage, and the gripping tool are set on the anti-vibration base plate 615 in order to remove the influence of external vibration as much as possible.

[0044]

As described above, according to the present invention, both the magnifying optics and the interferometer optics can be constructed only by switching the filter and the objective lens, and the conventional measuring instruments are combined. Compared with the measurement method, the cost of the device and inspection can be reduced. In addition, since the configuration is such that the magnified image and interference fringes acquired by the magnifying optics and the interferometric optics are image-analyzed, compared to the conventional measurement method that combines high quality inspection by non-contact inspection and individual measuring instruments, As a result, the inspection time can be shortened. In addition, the robot hand mechanism, autofocus function, automatic switching of the objective lens and the interference filter allows automation of inspection, reducing inspection cost and high accuracy.
Highly reliable inspection is possible. In addition, a dedicated interference fringe program can be used to speed up the measurement of vertex displacement. In addition, the high precision step detection method using the fringe scanning method and the curvature radius measurement can be performed, and the polishing surface shape batch high precision inspection and scratch image enhancement processing can be performed. This makes it easier to identify scratches.

[Brief description of drawings]

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

FIG. 2 is a structural explanatory view 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 exemplary embodiment of the present invention.

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

FIG. 5 is an explanatory diagram showing step detection according to an exemplary 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.

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

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

[Explanation of symbols]

100 ... Optical code, 100a ... Inspected ferrule, 1
00b ... other end ferrule, 101 ... X stage, 102
... micro displacement stage, 102a ... micro displacement stage controller, 103 ... ferrule alignment / grasping tool, 103a
... V groove made of zirconia, 103b ... Holding plate, 103c ...
Coil spring, 103d ... Flat plate part made of zirconia, 103
e ... stopper, 104 ... slide mechanism for holding plate up / down, 1
04a ... Air piping, 105 ... External white light source, 105a ...
Bundle fiber, 105b ... Ejection head, 106 ... Interference filter, 107 ... Magnifying objective lens, 108 ... Mechanical sliding mechanism for objective lens, 108a ... Air piping, 10
Reference numeral 9 ... Interference objective lens, 109a ... Reference mirror, 110 ... Mechanical slide mechanism for interference filter, 110a ... Air piping, 111 ... Anti-vibration base plate, 112 ... White light source, 112a
... light intensity adjuster, 113 ... half mirror, 114 ... CCD element, 114a ... CDD controller, 115 ... calculator,
116 ... Lens holder, 117 ... Other end ferrule fixing jig, 301 ... Interference fringe image, 302 ... Optical fiber image 401 ...
Inspection target 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 code, 60
0a ... ferrule to be inspected, 600b ... ferrule on the other end, 601 ... pallet, 601a, 601b ... ferrule gripping portion, 601c ... pulley, 602 ... white light source emitting head, 603 ... automatic transport mechanism, 604 ... robot hand, 605 ... ferrule alignment・ Gripping tool, 605a ... V
Groove, 605b ... Holding plate, 605c ... Coil spring, 605
d ... Flat plate part made of zirconia, 605e ... Stopper, 60
6 ... Air cylinder for holding tool up / down, 606a ... Air piping,
607 ... Calculator, 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 piping, 615 ... Anti-vibration base platen, 61
6 ... Micro displacement stage, 617 ... X stage, 700 ...
Inspection target ferrule, 701 ... Surface plate, 702 ... XY position adjusting 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 ... Sirconia,
801 ... Optical fiber, 900 ... Microscope, 901 ... Objective lens, 902 ... Transparent parallel plate, 903 ... Sample stage, 904 ... Ferrule gripping tool, 905 ... Inspection target ferrule, 906 ... White light source, 907 ... Half mirror, 90
8 ... CCD, 909 ... CCD controller, 910 ... Monitor, 911 ... Interference fringes, 912 ... Optical fiber image.

Claims (3)

[Claims] 1. A device for automatically inspecting 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, wherein a white light source and a half mirror are sequentially provided in an illumination light traveling direction, and the illumination light passes through the half mirror. Has a magnifying objective lens in the direction in which it is 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 objective lens is imaged through the magnifying objective lens and half mirror. Then, an interference filter is inserted in the illumination optical path between the white light source and the half mirror to form an end face image of the ferrule to be inspected, and the enlargement objective lens is switched to the interference objective lens by the 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 interfering optical meter and at the focal position of the magnifying objective lens. And a micro-displacement stage for giving a displacement in the optical axis direction, and means for automatically focusing on the focal positions of the magnifying and interference objective lenses, respectively. Then, a frame memory for A / D converting and accumulating the electric signal from the CCD device that has captured the magnified image and the interference fringe image generated by the magnifying and interference optics and an image processing unit for image-analyzing the interference fringe image are provided. Then, from the four or more interference fringe images obtained by applying the minute displacement four or more times in the optical axis direction by the minute displacement stage, the optical fiber direction of the optical fiber apex of the optical fiber center axis and the virtual apex of the zirconia part is obtained. Step, which is the deviation of
To automatically inspect the radius of curvature of the convex spherical surface, the deviation between the optical fiber center and the apex of the optical surface, which is the deviation within the plane perpendicular to the optical axis, and observe the end surface scratches and stains with the magnifying optical image. A featured optical connector polishing surface automatic inspection device. 2. A means for mechanically handling the ferrule to be inspected at the center of the optical axis of the interferometer and the magnifying optics and at the focal position, and after the inspection, mechanically handling the ferrule to be inspected and returning it to the initial position. The automatic connector polishing surface automatic inspection device according to claim 1, wherein 3. The 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 by using the interference optics of the optical connector polishing surface automatic inspection device according to claim 1, and the interference. The step of correcting the angular deviation between the optical axis of the optical meter and the central axis of the optical fiber of the ferrule to be inspected, the step of calculating the vertex deviation from the correction value obtained by the correction and the center of the interference fringes, and A step of calculating a radius of curvature from four or more interference fringe images obtained by applying a minute displacement four times or more using the minute displacement stage of the optical connector polishing surface automatic inspection device described in (1), and an optical fiber end face and a zirconia part. Is calculated and converted into height information, and a step is detected from the height of the apex of the zirconia portion and the height of the apex of the end face of the optical fiber.