JP2008292165A - 3D shape measuring device - Google Patents

Abstract

A three-dimensional shape measuring apparatus capable of measuring a three-dimensional shape with higher accuracy is provided.
A three-dimensional shape measuring apparatus 1 according to the present invention includes an imaging optical system 30 that acquires an image obtained by dividing an image of a test object 2 into a plurality of partial images, and a predetermined value in the optical axis direction of the imaging optical system 30. The illumination unit 20 illuminates the specimen 2 from a direction substantially perpendicular to the optical axis direction (optical axis O), and the specimen light 2 is illuminated with the sheet lights I1 to I3. The image processing unit 41 is configured to calculate a three-dimensional shape of the test object 2 based on a plurality of partial images imaged and acquired by the imaging optical system 30 in the above state.
[Selection] Figure 1

Description

  The present invention relates to a shape measuring apparatus for measuring a three-dimensional shape of an object.

Various techniques for measuring the surface shape of an object such as an industrial product in a non-contact manner have been proposed, and one of them is an optical three-dimensional shape measuring apparatus. There are various types of optical three-dimensional shape measurement devices and configurations. Among them, a line shape is obtained by projecting and scanning a sheet of light from an oblique direction onto an object and scanning it. There is one that measures the three-dimensional shape of a test object based on the amount of deviation of the light from the reference position (for example, see Patent Document 1).
Japanese Patent No. 1759477

  By the way, the position of the line-shaped light obtained by projecting on the object is determined for each pixel as the position of the luminance peak in the image captured by the CCD image sensor. However, the position of the luminance peak is not necessarily located on the coordinates defined for each pixel, and may be out of the coordinates for each pixel (that is, a subpixel region), which contributes to errors. It was.

  The present invention has been made in view of such a problem, and an object thereof is to provide a three-dimensional shape measuring apparatus capable of performing three-dimensional shape measurement with higher accuracy.

  In order to achieve such an object, a three-dimensional shape measuring apparatus according to a first invention includes an imaging optical system that acquires an image obtained by dividing an image of a test object into a plurality of partial images, and an optical axis of the imaging optical system. An illumination unit that illuminates the test object from a direction intersecting the optical axis direction with illumination light having a predetermined width in the direction, and imaging by the imaging optical system in a state where the illumination light is illuminated on the test object An image processing unit that calculates a three-dimensional shape of the test object based on the plurality of acquired partial images.

  Further, in the above-described invention, a stage unit that supports the test object to be movable in the optical axis direction is provided, and the test object supported by the stage unit moves in the optical axis direction at a predetermined movement pitch. Each time the imaging optical system acquires the imaging, the image processing unit captures and acquires the plurality of portions acquired by the imaging optical system each time the test object moves at the predetermined movement pitch. It is preferable to calculate the three-dimensional shape of the test object based on the image and the position information of the test object when the imaging acquisition is performed.

  In the above-described invention, it is preferable that the imaging optical system includes a plurality of CCD imaging elements that respectively capture and acquire the plurality of partial images.

  Further, in the above-described invention, the illumination light is sheet light extending in a plane intersecting the optical axis direction, and the illumination unit includes a plurality of the optical elements arranged in the optical axis direction within a focal depth of the imaging optical system. It is preferable to be configured to illuminate the specimen with sheet light.

  The three-dimensional shape measuring apparatus according to the second invention includes an imaging optical system that captures and acquires an image of a test object, and illumination light having a predetermined width in the optical axis direction of the imaging optical system. An illumination unit that illuminates the object from a direction intersecting with the object, and based on an image of the object imaged and acquired by the imaging optical system in a state where the illumination light is illuminated on the object An image processing unit that calculates a three-dimensional shape of the test object, and the illumination unit illuminates the test object with a plurality of illumination lights arranged in the optical axis direction within a focal depth of the imaging optical system Configured as follows.

  Moreover, in the above-mentioned invention, it is preferable that the illumination light is sheet light extending in a plane intersecting the optical axis direction.

  Further, in the above-described invention, a stage unit that supports the test object to be movable in the optical axis direction is provided, and the test object supported by the stage unit moves in the optical axis direction at a predetermined movement pitch. Each time, the imaging acquisition by the imaging optical system is performed, and the image processing unit captures and acquires the object by the imaging optical system every time the object moves at the predetermined movement pitch. Preferably, the three-dimensional shape of the test object is calculated on the basis of the image and the position information of the test object when the imaging acquisition is performed.

  Furthermore, in the above-described invention, it is preferable that the predetermined movement pitch is an integral multiple of a pitch interval in the plurality of illumination lights.

  In the above-described invention, the imaging optical system is configured to capture and acquire the image of the test object by dividing it into a plurality of partial images, and the image processing unit applies the plurality of partial images to the plurality of partial images. It is preferable to calculate the three-dimensional shape of the test object based on the above.

  According to the present invention, three-dimensional shape measurement can be performed with higher accuracy.

  Hereinafter, preferred embodiments of the present invention will be described. A schematic configuration of a three-dimensional shape measuring apparatus according to the present invention is shown in FIG. 1. This three-dimensional shape measuring apparatus 1 includes a stage unit 10 that supports a test object 2, and a test that is supported by the stage unit 10. Two illumination units 20 that illuminate the object 2 from the left and right, an imaging optical system 30 that images the test object 2 illuminated by the illumination unit 20, and an image processing device 40 that calculates the three-dimensional shape of the test object 2. It is composed mainly of. Note that the two illumination units 20 are arranged symmetrically with respect to the optical axis O of the imaging optical system 30.

  The stage unit 10 includes a sample stage 11 and a Z drive unit 12. The sample stage 11 is a stage for supporting and fixing the test object 2, and it is desirable that the sample stage 11 is not subject to disturbances such as vibrations as much as possible during measurement. The Z drive unit 12 includes a drive shaft that moves the sample table 11 that supports the test object 2 in the vertical direction, so that the test object 2 moves in the vertical direction, that is, the imaging optical system 30. It is supported so as to be movable in the optical axis direction (direction in which the optical axis O faces). Further, the Z drive unit 12 has a stroke that can illuminate the entire test object 2 with illumination light from the illumination unit 20.

  It is desirable that the straightness is small, but considering the xy coordinate calibration, it is desirable that the hysteresis is small and the position reproducibility is excellent. Further, the vertical position information of the sample stage 11 (Z drive unit 12) is continuously transmitted from the Z drive unit 12 to the image processing apparatus 40 as a position information signal.

  As shown in FIGS. 3A and 3B, the illumination unit 20 mainly includes three light sources 21 to 23 and a cylindrical lens 26 that converts the light from the light sources 21 to 23 into sheet light I1 to I3, respectively. And illuminates the test object 2 from the direction substantially perpendicular to the optical axis direction of the imaging optical system 30. The sheet lights I1 to I3 extend in a plane substantially perpendicular to the optical axis direction of the imaging optical system 30 and the optical axis of the imaging optical system 30 as shown in FIGS. It has a predetermined width in the direction (sufficiently small so that the optical contour lines 2a, 2b, 2c appear on the test object 2). By using such sheet light, it is possible to illuminate the test object 2 in a wide range at a time.

  Each of the light sources 21 to 23 uses an LED, a laser, or the like, and light having high directivity is emitted from each of the light sources 21 to 23. On the optical axis of the illumination unit 20 extending in a direction substantially perpendicular to the optical axis direction of the imaging optical system 30, as shown in FIGS. And the 1st mirror 24 and the 2nd mirror 25 are arrange | positioned.

  The illumination light emitted from the first light source 21 is reflected by the first mirror 24 toward the cylindrical lens 26, passes through the cylindrical lens 26, and then becomes the first sheet light I 1 and is emitted from the illumination unit 20. The The illumination light emitted from the second light source 22 goes straight as it is to reach the cylindrical lens 26, passes through the cylindrical lens 26, and then is emitted from the illumination unit 20 as the second sheet light I 2. The illumination light emitted from the third light source 23 is reflected by the second mirror 25 toward the cylindrical lens 26, passes through the cylindrical lens 26, and then becomes the third sheet light I 3 and is emitted from the illumination unit 20.

  As shown in FIG. 3B, the first light source 21, the second light source 22, and the third light source 23 are arranged at different heights in the vertical direction, that is, in the optical axis direction of the imaging optical system 30, respectively. As shown in FIGS. 1 and 2A, the first to third sheet lights I1 to I3 are illuminated on the test object 2 along the optical axis direction (vertical direction) of the imaging optical system 30. The At this time, the first to third sheet lights I <b> 1 to I <b> 3 are arranged within the focal depth of the imaging optical system 30. Accordingly, the light contour lines 2a to 2c formed by illuminating the test object 2 with the first to third sheet lights I1 to I3 are all within the in-focus range of the imaging optical system 30, and are thus imaged. This leads to higher contrast of the optical contour lines 2a to 2c, reduction of calibration data, and the like, and more accurate three-dimensional measurement can be expected.

  The imaging optical system 30 is mainly composed of an objective lens 31 and an imaging lens 32, and four CCD imaging elements 37a to 37d, and using the four CCD imaging elements 37a to 37d, as shown in FIG. The image 43 of the test object 2 is imaged and acquired by dividing it into first to fourth partial images 43a to 43d. On the optical axis O of the imaging optical system 30 extending in the vertical direction, as shown in FIG. 1, the objective lens 31, the imaging lens 32, the third half mirror 33, the fourth half mirror 34, and the fifth The half mirror 35 and the mirror 36 are arranged in this order.

  Then, the images of the light contour lines 2a to 2c formed by illuminating the test object 2 with the first to third sheet lights I1 to I3 (which are reflected lights) are obtained by the objective lens 31 and the imaging lens 32, respectively. An image is formed on the imaging surfaces of the four CCD imaging devices 37a to 37d. At this time, a part of the light (of the light contour lines 2a to 2c) that has passed through the objective lens 31 and the imaging lens 32 from the side of the test object 2 is reflected by the third half mirror 33 and is transmitted to the first CCD image sensor 37a. The remaining light passes through the third half mirror 33.

  A part of the light transmitted through the third half mirror 33 is reflected by the fourth half mirror 34 and reaches the second CCD image pickup device 37 b, and the rest is transmitted through the fourth half mirror 34. A part of the light transmitted through the third half mirror 33 and the fourth half mirror 34 is reflected by the fifth half mirror 35 and reaches the third CCD image sensor 37 c, and the rest is transmitted through the fifth half mirror 35. The light transmitted through the third half mirror 33, the fourth half mirror 34, and the fifth half mirror 35 is reflected by the mirror 36 and reaches the fourth CCD image sensor 37d.

  Here, the first CCD image sensor 37a captures and acquires the first partial image 43a that is the upper left portion of the image 43 of the test object 2 shown in FIG. The second CCD image sensor 37b captures and acquires the second partial image 43b that is the upper right portion of the image 43 of the test object 2. The third CCD imaging device 37c captures and acquires a third partial image 43c, which is the lower right portion, of the image 43 of the test object 2. The fourth CCD image sensor 37d captures and acquires a fourth partial image 43d that is a lower left portion of the image 43 of the test object 2.

  The positions of the light contour lines 2a to 2c on the test object 2 and the positions of the CCD image pickup devices 37a to 37d are conjugate. Further, the images of the light contour lines 2a to 2c formed on the imaging surfaces of the CCD imaging elements 37a to 37d are photoelectrically converted by the CCD imaging elements 37a to 37d, and image signals are sent to the image processing device 40. It has become. Further, since the optical contour lines 2a to 2c are processed as they are as the cross-sectional shape of the test object 2, it is desirable that the lens system has as little distortion as possible. Distortion that cannot be suppressed by design can be corrected by software after system construction.

  By the way, in the method of imaging a test object using a CCD image sensor and measuring the three-dimensional shape, the required accuracy may not be satisfied depending on the relationship between the magnification of the optical system and the CCD pixel. This is because a quantization error occurs in the process of digital processing of signals, and in principle, complete information cannot be restored. Generally, about 1/20 of the object length per pixel is said to be the limit of measurement accuracy.

  Therefore, by dividing and capturing the image 43 of the test object 2 into a plurality of partial images 43a to 43d, specifically, the light contour lines 2a to 2c appearing on the surface of the test object 2 are converted into a plurality of CCDs. Although the range (field of view) that can be picked up by one CCD image pickup device is narrowed by picking up images with the image pickup devices 37a to 37d, the object length per pixel is small, so that the quantization error during signal processing is minimized. be able to. Thus, by reducing the quantization error during signal processing, it becomes possible to perform three-dimensional shape measurement with higher accuracy. In particular, a high effect can be obtained when imaging is performed using a CCD imaging device as in the present embodiment.

  For example, when a 100 mm × 100 mm field of view is imaged by four CCD image sensors 37a to 37d, the field of view (imaging range) of one CCD image sensor is 50 mm × 50 mm. When a 2000 × 2000 pixel CCD image sensor is used, the object length per pixel is 25 μm. For this reason, it is considered that measurement with an accuracy of about 1 μm is possible from general intra-pixel division performance. Note that a field of view of 100 mm × 100 mm can be picked up at once using a 4000 × 4000 pixel CCD image pickup device, but the number of pixels becomes very large and the cost becomes high.

  The image processing device 40 includes an image processing unit 41 and a console 42 including a display device (such as a monitor) and an input device (such as a keyboard). The image processing unit 41 receives image signals from the CCD imaging elements 37 a to 37 d and a position information signal from the Z driving unit 12. Then, the image processing unit 41 includes the first to fourth partial images 43a to 43d captured and acquired by the first to fourth CCD imaging elements 37a to 37d, and the sample stage 11 (that is, when the imaging acquisition is performed). The three-dimensional shape of the test object 2 is calculated based on the position information of the test object 2).

  On the console 42, a measurement instruction is issued using an input device, and a calculation result (three-dimensional shape) in the image processing unit 41 is displayed using a display device. Further, the console 42 can calculate the dimensions and the like of an arbitrary position in the test object 2 from the three-dimensional data constructed by the image processing unit 41.

  The three-dimensional shape measurement using the three-dimensional shape measuring apparatus 1 configured as described above will be described below with reference to the flowchart shown in FIG. In this measurement, first, the test object 2 is placed on the sample stage 11 of the stage unit 10 in step S101.

  Next, in step S102, measurement specifications are determined. There are two main items to be determined. The first item is the range of vertical movement of the sample stage 11, that is, the measurement range of the test object 2, and is determined by the size of the test object 2. The second item is the vertical movement pitch of the sample stage 11, that is, the measurement pitch (movement pitch) of the test object 2, and is determined by the required accuracy. Note that the measurement accuracy is improved as the measurement pitch of the test object 2 is smaller. However, since the data processing takes time, the operator decides according to the situation.

  The measurement pitch (movement pitch) of the test object 2 is preferably an integer multiple of the pitch interval in the first to third sheet lights I1 to I3 aligned in the optical axis direction of the imaging optical system 30. In this way, for example, when the measurement pitch of the test object 2 is set to one time the pitch interval in each of the sheet lights I1 to I3, the information on the light contour lines appearing on the test object 2 is three times for the same position height. As a result, it is possible to perform three-dimensional shape measurement with higher accuracy by averaging or the like. In addition, if the measurement pitch of the test object 2 is set to be twice the pitch interval in each of the sheet lights I1 to I3, information on the light contour lines appearing on the test object 2 can be obtained twice for the same position height. The measurement pitch of the test object 2 is not limited to the above, and may be smaller than the pitch interval in each of the sheet lights I1 to I3.

  Next, in step S103, measurement is started according to the measurement specifications determined in step S102. That is, the measurement at the first height position in the test object 2 is started.

  Subsequently, in step S104, the first to fourth CCD image pickup devices 37a to 37d are used to image light contour lines 2a to 2c obtained by illuminating the test object 2 with the first to third sheet lights I1 to I3. The image signals of the CCD image pickup devices 37 a to 37 d are sent to the image processing unit 41. At the same time, a position information signal of the sample stage 11 (that is, the test object 2) when the imaging is performed is sent to the image processing unit 41.

  At this time, as described above, the first CCD image sensor 37a captures and acquires the first partial image 43a, the second CCD image sensor 37b acquires and acquires the second partial image 43b, and the third CCD image sensor 37c acquires the third partial image 43a. The fourth CCD image sensor 37d captures and acquires the fourth partial image 43d (see FIG. 5). In the present embodiment, since the first to third sheet lights I1 to I3 are arranged within the depth of focus of the imaging optical system 30, as shown in FIG. Three contour lines 2a, 2b and 2c respectively generated by the sheet lights I1 to I3 appear.

  Next, in step S105, it is determined whether all the measurements in the measurement range set in step S102 have been completed. If the determination is No, the process proceeds to step S106, the sample table 11 (that is, the test object 2) is moved up and down by one pitch by the Z drive unit 12 (moved in the optical axis direction of the imaging optical system 30), and step S103 is performed again. To Step S105. On the other hand, if the determination is Yes, the process proceeds to step S107.

  After the series of measurements is completed, in step S107, the image processing unit 41 performs contour line information obtained from each of the partial images 43a to 43d captured and acquired for each measurement pitch, and when imaging acquisition is performed for each measurement pitch. Based on the position information of the test object 2, the three-dimensional shape of the test object 2 is calculated and constructed on a computer. Specifically, a point coordinate group of (x, y, z) constituting a three-dimensional shape is calculated.

  In the next step S108, the three-dimensional shape of the test object 2 is displayed on the display device of the console 42 based on the point coordinate group calculated in step S107.

  In the next step S109, the console 42 is used to calculate the size of an arbitrary position in the test object 2 from the three-dimensional data constructed by the image processing unit 41, and the process is terminated. In step S109, the dimension of the test object 2 may be compared with the design CAD data.

  FIG. 6 shows a plurality of images 44 to 46 of the test object 2 having different height positions. The image 44 of the test object 2 whose upper part is illuminated with the sheet light is obtained by synthesizing the first to fourth partial images 44a to 44d, and the contour at the upper part of the test object 2 (or a cross section of the outer shape). A contour line 2d representing is shown. The partial images 44a to 44d partially overlap each other, and the visual field of the entire test object 2 is ensured by connecting the images. Although the image contact error becomes a measurement error, it is considered that the measurement accuracy is improved as much as the quantization error due to the narrow field of view is reduced.

  Similarly, the image 45 of the test object 2 with the sheet light illuminating the middle abdomen is obtained by combining the first to fourth partial images 45a to 45d, and the contour (or the middle part of the test object 2) (or A contour line 2e representing the outer cross section) appears. Similarly, the image 46 of the test object 2 whose lower part is illuminated with the sheet light is obtained by synthesizing the first to fourth partial images 46a to 46d, and the contour (or the outside) of the lower part of the test object 2 is obtained. A contour line 2f representing the cross section of the shape appears.

  Thus, based on the information on the contour lines 2d, 2e, 2f obtained from the plurality of images 44 to 46 having different height positions, the three-dimensional shape of the test object 2 is calculated as shown on the right side of FIG. It will be built on a computer. Thereby, it is possible to calculate a highly accurate three-dimensional shape along the contour of the test object 2. The data to be measured, such as the interval between contour lines, is discrete data, but may be connected by an appropriate interpolation method according to the measurement shape.

  In the above-described embodiment, a plurality of partial images are captured and acquired using the plurality of CCD imaging elements 37a to 37d. However, the present invention is not limited to this, and the optical axis of the imaging optical system is not limited to this. A plurality of partial images may be picked up and acquired by scanning while rotating around the center. Further, instead of using the plurality of CCD image pickup devices 37a to 37d, images entering one CCD image pickup device may be switched, for example, as first to fourth partial images 44a to 44d. In addition to the CCD image sensor, an amplification type solid-state image sensor such as a CMOS sensor can also be used.

  Further, in the above-described embodiment, the two illumination units 20 are arranged symmetrically with respect to the optical axis O of the imaging optical system 30, but the present invention is not limited to this, and the optical axis of the imaging optical system is used as a reference. It may be arranged on the front, rear, left and right.

It is a schematic block diagram of a three-dimensional shape measuring apparatus. (A) is a perspective view which shows a cylindrical lens, (b) is an optical path figure of the light which permeate | transmits a cylindrical lens. (A) is a top view which shows schematic structure of an illumination part, (b) is a side view which shows schematic structure of an illumination part. It is a flowchart which shows a three-dimensional shape measurement. It is a schematic diagram which shows the image and partial image of a to-be-tested object. It is a schematic diagram which shows the example which constructed | assembled the three-dimensional shape of the to-be-tested object.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 3D shape measuring apparatus 2 Test object 10 Stage part 20 Illumination part 30 Image pick-up optical system 37a 1st CCD image pick-up element 37b 2nd CCD image pick-up element 37c 3rd CCD image pick-up element 37d 4th CCD image pick-up element 40 Image processing apparatus 41 Image processing part 43 Image 43a first partial image 43b second partial image 43c third partial image 43d fourth partial image I1 first sheet light I2 second sheet light I3 third sheet light O optical axis

Claims (9)

An imaging optical system for acquiring an image obtained by dividing an image of a test object into a plurality of partial images;
An illumination unit that illuminates the test object from a direction that intersects the optical axis direction with illumination light having a predetermined width in the optical axis direction of the imaging optical system;
An image processing unit that calculates a three-dimensional shape of the test object based on the plurality of partial images captured and acquired by the imaging optical system in a state where the illumination light is illuminated on the test object. A three-dimensional shape measuring apparatus characterized by comprising. A stage unit that supports the test object to be movable in the optical axis direction;
Each time the test object supported by the stage unit moves in the optical axis direction at a predetermined movement pitch, the imaging acquisition by the imaging optical system is performed,
The image processing unit includes the plurality of partial images captured and acquired by the imaging optical system each time the test object moves at the predetermined movement pitch, and the test object when the imaging acquisition is performed. The three-dimensional shape measuring apparatus according to claim 1, wherein the three-dimensional shape of the test object is calculated based on position information.   3. The three-dimensional shape measuring apparatus according to claim 1, wherein the imaging optical system includes a plurality of CCD imaging elements that respectively capture and acquire the plurality of partial images. The illumination light is sheet light extending in a plane intersecting the optical axis direction,
The said illumination part is comprised so that the said to-be-tested object may be illuminated with the several said sheet light arranged in the said optical axis direction within the depth of focus of the said imaging optical system. The three-dimensional shape measuring apparatus according to any one of the above. An imaging optical system that captures and acquires an image of a test object;
An illumination unit that illuminates the test object from a direction that intersects the optical axis direction with illumination light having a predetermined width in the optical axis direction of the imaging optical system;
An image processing unit that calculates a three-dimensional shape of the test object based on an image of the test object captured and acquired by the imaging optical system in a state where the illumination light is illuminated on the test object. ,
The three-dimensional shape measuring apparatus, wherein the illuminating unit is configured to illuminate the test object with a plurality of illumination lights arranged in the optical axis direction within a depth of focus of the imaging optical system.   The three-dimensional shape measuring apparatus according to claim 5, wherein the illumination light is sheet light extending in a plane intersecting the optical axis direction. A stage unit that supports the test object to be movable in the optical axis direction;
Each time the test object supported by the stage unit moves in the optical axis direction at a predetermined movement pitch, the imaging acquisition by the imaging optical system is performed,
The image processing unit includes an image of the test object acquired and acquired by the imaging optical system every time the test object moves at the predetermined movement pitch, and the test object when the imaging acquisition is performed. The three-dimensional shape measuring apparatus according to claim 5, wherein the three-dimensional shape of the test object is calculated based on the position information.   The three-dimensional shape measuring apparatus according to claim 7, wherein the predetermined movement pitch is an integral multiple of a pitch interval in the plurality of illumination lights. The imaging optical system is configured to capture and acquire an image of the test object by dividing it into a plurality of partial images,
The three-dimensional shape measurement according to any one of claims 5 to 8, wherein the image processing unit calculates a three-dimensional shape of the test object based on the plurality of partial images. apparatus.

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