JP2015096837A - Surface shape measuring instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve measurement accuracy of a surface shape by effectively using a light receiving surface of an image pick-up device in a surface shape measuring instrument.SOLUTION: The surface shape measuring instrument includes: light irradiation means that applies slit light 13 to a surface of a measurement object 11 having a rugged structure; image formation means M (M1 to M6) that receives light from a slit light irradiation area 14 on the surface from a direction at an angle to the irradiation direction of the slit light 13 and forms an image of a section line of rugged structure; imaging means for capturing an image of the section line of rugged structure; and image magnifying means M that is disposed on an optical path from the slit light irradiation area 14 to the imaging means and magnifies the image in the height direction of the rugged structure.

Description

  The present invention relates to a surface shape measuring apparatus that measures the shape of the surface of an article using an optical cutting method.

One method for measuring the shape of the surface of an article is a light cutting method.
The light cutting method is a method of measuring the shape by irradiating slit light so as to cut the uneven structure on the surface of the object to be measured and forming an image of the cutting line of the uneven structure on the light receiving surface of the imaging means. It is. Since the image of the cutting line of the concavo-convex structure reflects the shape of the concavo-convex structure, the image formed on the light receiving surface of the imaging means is sequentially analyzed while moving the irradiation position of the slit light on the surface of the object to be measured. As a result, the uneven shape existing on the surface of the object to be measured can be three-dimensionally measured.

Patent Document 1 describes a surface shape measuring apparatus that measures the surface shape of a substrate 101 having a concavo-convex structure 104. The principal part structure is shown in FIG.
In this apparatus, the slit light 122 is irradiated from the laser light source 121 perpendicularly to the surface of the substrate 101. Then, the light from the surface of the substrate 101 is reflected by the mirror 126A, divided by the half mirror 125A, and incident on the two CCD cameras 113a and 113b arranged so as to be shifted in the horizontal direction (direction perpendicular to the paper surface). In addition, on the opposite side across the slit light, the light from the surface of the substrate 101 is incident on two CCD cameras 113c and 113d arranged in a horizontal direction by the same path as described above. In this way, an image of the concavo-convex structure 104 is obtained by sharing the visual field by the four CCD cameras arranged so as to be shifted from each other (FIG. 2).

JP 11-37734 A

  In the surface shape measuring apparatus using the light cutting method, the surface of the object to be measured is obtained by irradiating a wide slit light so as to cut the uneven structure on the surface of the object to be measured, and obtaining an image of the cutting line of the uneven structure. If there is a high convex structure, an image of the shadowed portion cannot be obtained. Therefore, such a surface shape measuring device is often used for measuring the shape of a surface having a wide and low uneven structure, and on the light receiving surface of an imaging means such as a CCD camera, as shown in FIG. An image that is long in the width direction and short in the height direction is formed. Therefore, only the belt-like area at the center is used for the light receiving surface of the imaging means, and the other areas are wasted.

  The problem to be solved by the present invention is to effectively use the area on the light receiving surface of the imaging means and measure the accuracy in the surface shape measuring device that measures the shape of the surface of the object to be measured using the light cutting method. It is to improve.

The surface shape measuring apparatus according to the present invention made to solve the above problems is
a) a light irradiation means for irradiating the surface of the object to be measured having an uneven structure with slit light;
b) Imaging means for receiving light from the slit light irradiation region of the surface from a direction that forms an angle with respect to the irradiation direction of the slit light, and forming an image of a cutting line of the concavo-convex structure;
c) an imaging means for capturing an image of a cutting line of the concavo-convex structure;
d) an image enlarging unit that is disposed on an optical path from the slit light irradiation region to the imaging unit and that magnifies the image in the height direction of the concavo-convex structure;
It is characterized by providing.

The said slit light means the shape which passed the slit, ie, sheet-like light, and is not limited only to the light which passed the slit. Alternatively, the slit light may be obtained by scanning linear light that irradiates the surface of the workpiece with a point. When scanning linear light, light scanning and workpiece movement are performed alternately.
As the image enlarging means, for example, a cylindrical concave mirror, a cylindrical convex mirror, or a cylindrical lens can be used. A plurality of these may be combined to enlarge the image in the above direction.

  In the surface shape measuring apparatus according to the present invention, the image of the cutting line of the concavo-convex structure on the surface of the object to be measured is enlarged in the height direction of the concavo-convex structure by the image magnifying means and imaged on the light receiving surface of the imaging means. . On the light receiving surface of the imaging means, an image of the cutting line of the concavo-convex structure enlarged in the height direction is formed in an area that has not been used conventionally, so an image with higher resolution than in the past in the height direction. can get. As described above, by using the surface shape measuring apparatus according to the present invention, it is possible to effectively use a region on the light receiving surface that has not been conventionally used, and to improve the surface shape measurement accuracy.

In the surface shape measuring apparatus according to the present invention, the imaging means is
e) a plurality of reflective surfaces arranged side by side in the direction in which the cutting line extends, each being at a different height from the surface, parallel to the cutting line and at an angle to the surface A first reflecting means having a plurality of first reflecting surfaces which are a plurality of reflecting surfaces parallel to each other;
f) A plurality of reflecting surfaces that are located at an equal distance from each of the plurality of first reflecting surfaces and on which light reflected by the plurality of first reflecting surfaces is incident, and are perpendicular to the surface and parallel to each other. A second reflecting means having a plurality of second reflecting surfaces which are a plurality of reflecting surfaces;
It can comprise.

In the surface shape measuring apparatus of this aspect, light from the surface of the object to be measured is reflected by the plurality of first reflecting surfaces that are parallel to the cutting line of the concavo-convex structure on the surface and form an angle with the surface. Furthermore, the light is reflected by a plurality of second reflecting surfaces perpendicular to the surface of the object to be measured and travels toward the light receiving surface of the imaging means. The plurality of second reflection surfaces, which are located at different heights from the surface and on which light reflected by the plurality of first reflection surfaces parallel to each other, are disposed at different heights from the surface. An image formed on the light receiving surface of the imaging unit by the light reflected by the plurality of second reflecting surfaces is obtained by dividing the image of the cutting line of the concavo-convex structure into a plurality of pieces and rotating them by 90 °.
In the surface shape measuring apparatus of this aspect, since the image of the cutting line of the concavo-convex structure is divided into a plurality of images and formed on the light receiving surface, the shape of the light receiving surface of the imaging means or the shape of the image of the cutting line of the concavo-convex structure In consideration of the above, it is possible to effectively use the area on the light receiving surface of the imaging means.

The surface shape measuring apparatus of this aspect further includes
g) disposed on at least one optical path of a plurality of optical paths from the slit light irradiation region to the imaging means via the first reflecting means and the second reflecting means, and the total length of the optical paths Without changing the optical path adjusting means for changing the position incident on the imaging means,
It is desirable to provide.

  The optical path adjusting means can be constituted by, for example, a light transmitting member having a refractive index different from that of air, or a plurality of mirrors that form a detouring optical path.

  In the surface shape measuring device of this aspect, the separation distance of the images of the plurality of unit irradiation regions is adjusted by the optical path adjusting means. That is, it is possible to adjust the image separation distance in consideration of the shape and size of the light receiving surface of the imaging unit, and to use the light receiving surface of the imaging unit more efficiently. Since this optical path adjustment means does not change the total length of the optical path in which the means is arranged, the resolution of the image picked up by the image pickup means does not change.

  In the surface shape measuring apparatus according to the present invention, an image of the cutting line of the concavo-convex structure expanded in the height direction is formed on an area of the light receiving surface of the imaging unit that has not been conventionally used, and the height direction To obtain an image with increased resolution. Therefore, it is possible to effectively use the region on the light receiving surface of the image pickup means and improve the measurement accuracy of the surface shape.

The principal part block diagram of the conventional surface shape measuring apparatus. The figure which shows the condition of the visual field sharing by the four CCD cameras in the conventional surface shape measuring apparatus. The figure explaining use of the light-receiving surface of the image pick-up element in the conventional surface shape measuring apparatus. FIG. 3 is a main part configuration diagram of the surface shape measuring apparatus according to the first embodiment. FIG. 4 is a diagram for explaining rotation and enlargement of an image in the surface shape measurement apparatus according to the first embodiment. The figure which compares and demonstrates use of the light-receiving surface of the image pick-up element in the surface shape measuring apparatus of Example 1 and use of the light-receiving surface of the image pick-up element in the conventional apparatus. FIG. 6 is a diagram illustrating a configuration of an optical path adjusting unit in the surface shape measuring apparatus according to the second embodiment. FIG. 6 is a diagram illustrating an imaging position on a light receiving surface of an imaging element of a surface shape measuring apparatus according to a second embodiment.

  Embodiments of a surface shape measuring apparatus according to the present invention will be described below with reference to the drawings.

FIG. 4 shows a main configuration of the surface shape measuring apparatus according to the first embodiment.
The surface shape measuring apparatus of the present embodiment is an apparatus that measures the shape of the concavo-convex structure on the surface of the workpiece 11. The workpiece 11 is placed on the placing table 12, and sequentially moves in a predetermined step toward the right in the drawing by a moving mechanism (not shown).
Slit light 13 emitted from a light source (not shown) and passed through the slit is irradiated so as to cut the uneven structure on the surface of the work 11. The slit light irradiation region 14 is virtually divided into three (14a, 14b, 14c) in the direction in which the line (cutting line) that the slit light cuts the concavo-convex structure extends.

  Above the workpiece 11, there are six cylindrical concave mirrors M1 to M6 for causing the light from the slit light irradiation region 14 to enter the light receiving surface 15 of the CCD camera to form an image of the cutting line of the concavo-convex structure. Has been placed.

  Cylindrical concave mirrors M1, M2, and M3 are arranged vertically above the slit light irradiation regions 14a, 14b, and 14c, and at heights H1, H2, and H3 (H1 <H2 <H3), respectively. Inclined in a direction parallel to the cutting line of the structure and at an angle of 45 degrees with respect to the surface of the workpiece 11. The cylindrical concave mirrors M1, M2, and M3 are image magnifying means for enlarging the image of the cutting line of the concavo-convex structure in the height direction of the concavo-convex structure, and constitute the first reflecting means.

  Cylindrical concave mirrors M4, M5, and M6 are arranged at distances L from M1, M2, and M3 in the direction opposite to the moving direction of the work, and perpendicular to the surface of the work 11, It is inclined in a direction that forms an angle of 45 degrees with respect to the cutting line of the concavo-convex structure. The cylindrical concave mirrors M4, M5, and M6 are separated from the light receiving surface 15 of the CCD camera by D1, D2, and D3 (D1> D2> D3), respectively. Here, H1 + L + D1 = H2 + L + D2 = H3 + L + D3. That is, the light path lengths until the light from each of the three divided slit light irradiation areas 14a, 14b, and 14c is reflected by the two mirrors and reaches the light receiving surface 15 of the CCD camera are equal to each other. ing. Cylindrical concave mirrors M4, M5, and M6 constitute second reflecting means. The concave shape of the cylindrical concave mirror is the same as that of the cylindrical concave mirrors M1, M2, and M3, and the optical path bent by the cylindrical concave mirrors M1, M2, and M3 so as to enlarge the image of the concavo-convex structure in the height direction is made parallel. It also plays a role of returning to the optical path (maintaining telecentricity).

The light emitted from the slit light irradiation area 14a is reflected in the horizontal direction (the direction opposite to the moving direction of the workpiece) by the cylindrical concave mirror M1 disposed vertically above the area 14a, and further, the horizontal plane by the cylindrical concave mirror M4. After the traveling direction is changed in the vertical direction, the light enters the lower region of the light receiving surface 15 of the CCD camera.
Similarly, the light emitted from the slit light irradiation region 14b is reflected by the cylindrical concave mirrors M2 and M5 and enters the central region of the light receiving surface 15 of the CCD camera. Further, the light emitted from the slit light irradiation region 14c is similarly reflected by the cylindrical concave mirrors M3 and M6 and enters the upper region of the light receiving surface 15 of the CCD camera.

  On the surface of the workpiece 11, the image of the cutting line of the concavo-convex structure in the slit light irradiation regions 14a, 14b, and 14c is adjacent to the direction in which the cutting line extends (FIG. 5A). However, these three images are rotated 90 ° by the first reflecting means and the second reflecting means, and the images are enlarged 1.5 times in the height direction by the cylindrical concave mirrors M1, M2, and M3, and the CCD camera An image is formed on the light receiving surface 15 (FIG. 5C). In FIG. 5, for the sake of convenience, the aspect ratio is changed from the actual ratio.

  In a conventional surface shape measuring apparatus, a 90 mm square light receiving surface is required in order to form an image of a cutting line (90 mm × 5 mm) having the same concavo-convex structure on a square light receiving surface (FIG. 6B). )). Only the belt-like region at the center of the light receiving surface 15 is used, and the wide regions above and below the light receiving surface are not used.

  On the other hand, in the surface shape measuring apparatus of the present embodiment, as shown in FIG. 6A, a cut image can be obtained by forming three images side by side in a 30 mm square light receiving surface. In this way, on the light receiving surface 15 having a conventional area of 1/9, an image having a higher resolution than the conventional one can be obtained by utilizing not only the central portion on the light receiving surface 15 but also the upper and lower regions. Can do.

  More specifically, if the angles when the optical path is bent are all 90 °, the values of D1 to D3 in FIG. 4 are D1 = D2 + 30 mm = D3 + 60 mm, and the values of H1 to H3 are naturally H3 = H2 + 30 mm = H1 + 60 mm. Therefore, three images can be arranged in the 60 mm + α square light receiving surface. The difference between H3, H1, and H2 can be reduced by setting the optical path bending angle at M4 to M6 to other than 90 °, or by providing an optical path adjusting means as in Example 2 described later. Three images can be arranged in a 30 mm square light receiving surface. Even if the size of the light-receiving surface cannot be reduced so much as 60 mm + α square, it is possible to reduce the size of a device that tends to increase in the vertical direction in order to ensure the focal length of the lens by bending the optical path in the horizontal direction. There is.

  In this embodiment, cylindrical concave mirrors M1 to M6 are used, but cylindrical convex mirrors may be used instead. Alternatively, a plane mirror that rotates the image and a cylindrical lens that expands the image may be combined. In this case, the image is rotated by 90 ° by being sequentially reflected by the plane mirror constituting the first reflecting means and the plane mirror constituting the second reflecting means (FIG. 5B), and passes through the cylindrical lens. As a result, the image is enlarged in the height direction (FIG. 5C). In this configuration, the cylindrical lens may be arranged at another position on the optical path from the slit light irradiation region to the light receiving surface. Further, the above-described configurations can be used in combination.

  Next, another embodiment 2 of the surface shape measuring apparatus according to the present invention will be described. The configuration of the main part of the surface shape measuring apparatus of the present embodiment is the same as that of the first embodiment shown in FIG. 4, and therefore, description regarding the main configuration is omitted, and only differences from the first embodiment will be described.

  In the surface shape measuring apparatus according to the first embodiment, when the slit light irradiation areas 14a, 14b, and 14c are determined, the distances D1, D2, and D3 are determined, and subsequently, the heights H1, H2, and H3 are determined. Further, on the light receiving surface 15 of the CCD camera, images of the cutting lines in the slit light irradiation areas 14a, 14b, and 14c are formed at positions of heights H1, H2, and H3, respectively. That is, in the configuration of the first embodiment, when the slit light irradiation areas 14a, 14b, and 14c are determined, the imaging position on the light receiving surface 15 is fixed. In the first embodiment, as shown in FIG. 5C, there are some unused areas of the light receiving surface 15 between two vertically adjacent images on the light receiving surface 15. In such a case, if the image forming position on the light receiving surface 15 can be changed appropriately in the vertical direction to reduce (or eliminate) the unused area, for example, a slit that forms an image on the light receiving surface 15 The light irradiation region 14 can be expanded. Alternatively, when the slit light irradiation area 14 is the same, it is possible to pick up an image with a CCD camera having a smaller light receiving surface 15 than in the first embodiment. The surface shape measuring apparatus according to the second embodiment is an apparatus configured to achieve such an object.

  Specifically, in the surface shape measuring apparatus according to the second embodiment, the images of the cutting lines in the slit light irradiation regions 14b and 14c are respectively expressed as height H2-ΔL2 (H2 in the first embodiment) and height H3-ΔL3 (implementation). In Example 1, an image is formed at the position H3). Therefore, the mirrors M2 and M5 are arranged at a height H2-ΔL2 (H2 in the first embodiment), and the mirrors M3 and M6 are arranged at a height H3-ΔL3 (H3 in the first embodiment). Here, ΔL3 = ΔL2 × 2.

  When the mirror arrangement is changed as described above, the imaging position of the cutting line moves downward, but the optical path lengths of the three optical paths from the slit light irradiation regions 14a, 14b, and 14c to the light receiving surface 15 vary. Arise. Specifically, the optical path corresponding to the slit light irradiation area 14a is the longest, whereas the optical paths corresponding to the slit light irradiation areas 14b and 14c are shortened by ΔL2 and ΔL3, respectively. When the optical path length varies, the resolution of the images formed on the light receiving surface 15 also varies, and the measurement accuracy of the shape of the concavo-convex structure analyzed from these images also varies. Therefore, it is necessary to eliminate the optical path length difference (ΔL2, ΔL3) generated between the three optical paths.

  Therefore, in the surface shape measuring apparatus according to the second embodiment, an optical path adjusting unit shown in FIG. 7 is added to the configuration of the surface shape measuring apparatus according to the first embodiment. The optical path adjusting means 20 is composed of two plane mirrors M2a and M2b, and is arranged in place of the cylindrical concave mirror M2. When the plane mirrors M2a and M2b are arranged in this way, the detour optical path 21 is formed, so that the optical path length in this region is increased by ΔL2. Further, instead of the cylindrical concave mirror M3, plane mirrors M3a and M3b are arranged to form a bypass optical path in the same manner, and the optical path length in this region is increased by ΔL3. Thus, the above-described difference in optical path length is eliminated. Furthermore, instead of the cylindrical concave mirrors M1, M4, M5, and M6, plane mirrors are arranged, and cylindrical lenses for enlarging the image in the height direction of the concavo-convex structure are arranged on the three optical paths.

  In the present embodiment, the optical path adjusting means is disposed at the positions of the cylindrical concave mirrors M2 and M3 of the first embodiment, but is not necessarily limited to these positions, and the optical path adjusting means is provided at any position of M1 to M6. 20 can be arranged. By appropriately changing the arrangement of the optical path adjusting means 20 and the length of the bypass optical path, the imaging position on the light receiving surface 15 can be moved up and down by an arbitrary distance. Therefore, the entire light receiving surface 15 can be effectively used in consideration of the shape of the light receiving surface 15 of the imaging means and the shape of the slit light irradiation region. In addition, a cylindrical concave mirror or a cylindrical convex mirror may be used as a mirror constituting the optical path adjusting unit 20.

  A refractive index member can also be used as the optical path adjusting means. When a refractive index member having a refractive index n and a thickness d is arranged on the optical path, the substantial optical path length can be increased by (1-1n /) d without changing the physical length. Accordingly, the image forming position on the light receiving surface 15 can be changed without changing the optical path length by appropriately changing the refractive index n and thickness d of the member and appropriately setting the arrangement of each mirror. Can be made.

The above embodiment is merely an example, and can be appropriately changed in accordance with the spirit of the present invention.
In the first and second embodiments, the slit light irradiation area is divided into three parts, and an image of the cutting line in each is formed on the light receiving surface of the imaging unit. However, the number of divisions of the slit light irradiation area is the light receiving surface. It can be determined appropriately in consideration of the shape and the like. Alternatively, the image of the cutting line may be enlarged in the height direction of the concavo-convex structure and formed on the light receiving surface without dividing the slit light irradiation region. If the slit light irradiation area is not divided, the reflecting means for rotating the image as in the first and second embodiments may not be arranged.

  The position and tilt direction of each mirror in the configurations of the first and second embodiments can be changed as long as the image can be rotated 90 ° by reflection by the first reflecting means and the second reflecting means. A lens for correcting aberration caused by image enlargement may be arranged on each optical path. Thereby, the aberration of the image can be corrected to improve the measurement accuracy. Further, by disposing the object side telecentric lens 30 between the surface of the work 11 and the first reflecting means, an object side telecentric optical system can be configured to increase the resolution of the image (see FIG. 7). Further, a lens for reducing (or enlarging) the image may be disposed at an appropriate position on the optical path to change the size of the image of the cutting line so as to match the size of the light receiving surface of the imaging unit. .

DESCRIPTION OF SYMBOLS 11 ... Work 12 ... Mounting stand 13 ... Slit light 14, 14a, 14b, 14c ... Slit light irradiation area 15 ... Light-receiving surface 20 ... Optical path adjustment means M1-M6 ... Cylindrical concave mirror M2a, M2b, M3a, M3b ... Plane mirror 101 ... Substrate 104 ... Uneven structure 113a ... CCD camera 113c ... CCD camera 121 ... Laser light source 122 ... Slit light 125A ... Half mirror 126A ... Mirror

Claims (4)

a) a light irradiation means for irradiating the surface of the object to be measured having an uneven structure with slit light;
b) Imaging means for receiving light from the slit light irradiation region of the surface from a direction that forms an angle with respect to the irradiation direction of the slit light, and forming an image of a cutting line of the concavo-convex structure;
c) an imaging means for capturing an image of a cutting line of the concavo-convex structure;
d) an image enlarging unit that is disposed on an optical path from the slit light irradiation region to the imaging unit and that magnifies the image in the height direction of the concavo-convex structure;
A surface shape measuring device comprising: The imaging means is
e) a plurality of reflective surfaces arranged side by side in the direction in which the cutting line extends, each being at a different height from the surface, parallel to the cutting line and at an angle to the surface A first reflecting means having a plurality of first reflecting surfaces which are a plurality of reflecting surfaces parallel to each other;
f) A plurality of reflecting surfaces that are located at an equal distance from each of the plurality of first reflecting surfaces and on which light reflected by the plurality of first reflecting surfaces is incident, and are perpendicular to the surface and parallel to each other. A second reflecting means having a plurality of second reflecting surfaces which are a plurality of reflecting surfaces;
The surface shape measuring apparatus according to claim 1, wherein g) disposed on at least one optical path of a plurality of optical paths from the slit light irradiation region to the imaging means via the first reflecting means and the second reflecting means, and the total length of the optical paths Without changing the optical path adjusting means for changing the position incident on the imaging means,
The surface shape measuring device according to claim 2, comprising:   4. The surface shape measuring apparatus according to claim 1, wherein the optical system included in the image forming means is a telecentric optical system at least on the surface side of the object to be measured.

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