Image measurement machine and program

Abstract

To provide an image measurement machine capable of restoring an image without disturbances such as jiggling or blurring, without sequentially recording a light quantity change and a movement locus during imaging.SOLUTION: The image measurement machine includes: a stage which has a measurement workpiece placing area in which a measurement workpiece which is a measurement object is placed and a reference workpiece placing area in which a reference workpiece is placed; a measurement workpiece imaging part which images a measurement workpiece image which is an image of the measurement workpiece placed in the measurement workpiece placing area; a reference workpiece imaging part which images a reference workpiece image which is an image of the reference workpiece placed in the reference workpiece placing area, at the same time when the measurement workpiece image is imaged by the measurement workpiece imaging part; and a correction part which corrects the measurement workpiece image imaged by the measurement workpiece imaging part on the basis of the reference workpiece image imaged by the reference workpiece imaging part and a standard reference workpiece image which is the image of the reference workpiece.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an image measuring instrument and a program for measuring the shape of a measurement object in a non-contact manner based on an image obtained by capturing an image of the measurement object. [Background technology]

[0002] An image measuring instrument is a device that takes an image of the object to be measured (hereafter referred to as the "workpiece"), analyzes the image, extracts shapes such as lines, circles, polygons, etc., and obtains measurement results such as distance, inclination, diameter, width, etc. of the extracted shapes.

[0003] When capturing an image of a workpiece with an image measuring machine, in order to prevent image blurring, the stage is generally moved so that each measurement point is within the field of view of the image, and then the image is captured after the stage is stopped. If the stage is not sufficiently stationary or is moving, the captured image of the workpiece will be blurred, leading to measurement errors. Image distortion due to an unstable light amount can also be a cause of measurement errors.

[0004] Ideally, it would be desirable to keep the stage completely still and completely eliminate any fluctuations in light intensity, but in reality, it is difficult to completely eliminate fluctuations in stage movement and fragrance due to external vibrations, power supply noise, etc. Also, depending on the environment in which the image measuring instrument is installed, it may be subject to strong external disturbances, which could result in significant measurement errors.

[0005] On the other hand, as a technique for suppressing such image distortion, there is a technique for removing image blur caused by deconvolution and restoring an image without distortion (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6742783 Summary of the Invention [Problem to be solved by the invention]

[0007] However, to restore an unblurred image through deconvolution, it is necessary to know the change in light intensity during imaging and the movement trajectories of the stage and camera in chronological order. However, if the change in light intensity and the movement trajectories were to be recorded one by one for this purpose, it would lead to increased costs.

[0008] An object of the present invention is to provide an image measuring instrument that can restore an image that is free from distortions such as blurring and fading, without recording the change in light amount and the movement trajectory during imaging one by one. [Means for solving the problem]

[0009] In order to solve the above problems, an image measuring machine according to an embodiment of the present invention comprises a stage having a measurement work placing area on which a measurement work, which is the object to be measured, is placed, and a reference work placing area on which a reference work is placed, a measurement work imaging unit that captures a measurement work image, which is an image of the measurement work placed in the measurement work placing area, a reference work imaging unit that captures a reference work image, which is an image of the reference work placed in the reference work placing area, simultaneously with capturing the measurement work image by the measurement work imaging unit, and a correction unit that corrects the measurement work image captured by the measurement work imaging unit based on the reference work image captured by the reference work imaging unit and a standard reference work image, which is the reference work.

[0010] In the present invention, the measurement workpiece image is MWI, the reference workpiece image is RWI, and the reference reference workpiece image is RWI ref , and the application of the Fourier transform is the function F(), and the application of the inverse Fourier transform is the function F -1 The corrected measured workpiece image data MWI is expressed as (). correct , MWI correct =F -1 (F(MWI) · F(RWI ref ) / F(RWI)).

[0011] In the present invention, it is preferable to further provide a light source that irradiates the measurement workpiece and the reference workpiece with light under common illumination conditions when capturing the measurement workpiece image and the reference workpiece image.

[0012] In the present invention, it is preferable to further include a high-rigidity connecting member that connects the measurement work imaging unit and the reference work imaging unit.

[0013] In the present invention, it is preferable that the measurement work imaging section and the reference work imaging section are realized by sharing one set of imaging element and optical system.

[0014] In the present invention, the reference reference workpiece image may be an image of the reference workpiece captured under ideal imaging conditions, or may be an image generated from design data of the reference workpiece.

[0015] A program according to an embodiment of the present invention is characterized in that it causes a computer to function as a correction unit in the above-mentioned image measuring device. [Brief description of the drawings]

[0016] [Figure 1] 1 is a functional block diagram showing the configuration of an image measuring instrument 1 in a first embodiment. [Diagram 2] FIG. 2 is a block diagram showing the configuration of a computer main unit 160. [Diagram 3] FIG. 11 is a functional block diagram showing the configuration of an image measuring instrument 1 in a second embodiment. [Figure 4] 1 is a schematic diagram showing an example in which a plurality of reference works RW are placed on the stage 14 in correspondence with a plurality of measurement points of the measurement work WM. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] [First embodiment] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, the same members are designated by the same reference numerals, and the description of members that have already been described will be omitted as appropriate.

[0018] [Configuration of the image measuring device] 1 is a functional block diagram showing the configuration of an image measuring machine 1 in the first embodiment. The image measuring machine 1 includes a stage 14, an imaging unit 10, a light source 13 that irradiates light onto a measurement workpiece MW and a reference workpiece RW, and a computer system 16.

[0019] The stage 14 is arranged so that its upper surface (mounting surface) is a horizontal plane. On the upper surface, there are provided a measurement work mounting area on which the measurement work MW, which is the object to be measured, is mounted, and a reference work mounting area on which the reference work RW is mounted. The reference work RW is a work having a known shape. An ideal image (standard reference work image) of the reference work RW and a reference work image captured simultaneously with the image of the measurement work are used in the correction process described below. The stage 14 has driving means in the X-axis direction and the Y-axis direction, and is movable in the X-axis direction and the Y-axis direction under the control of the computer system 16.

[0020] The imaging unit 10 includes a measurement work imaging section 11 that captures an image of a measurement work MW, and a reference work imaging section 12 that captures an image of a reference work RW.

[0021] The measurement workpiece imaging unit 11 captures a measurement workpiece image, which is an image of the measurement workpiece MW. The measurement workpiece imaging unit 11 has an imaging element 111 and an optical system 112. The measurement workpiece imaging unit 11 is arranged so that at least a part of the measurement workpiece placement area 141 on the stage 14 where the measurement workpiece MW is placed is included in the imaging field of view. The imaging element 111 is, for example, a two-dimensional image sensor such as a CCD or a CMOS. The optical system 112 forms an image of the measurement workpiece MW on the light receiving surface of the imaging element 111. The optical system 112 is, for example, a combination of multiple lenses and apertures to form a telecentric optical system. In the telecentric optical system, the principal ray can be regarded as parallel light, so the dimensions in the captured image do not depend on the position in the Z-axis direction (height direction). For this reason, it is suitable for measuring a measurement workpiece MW that has undulations (for example, steps, holes, etc.). The image of the measurement workpiece MW is converted into an image (image data) by the imaging element 111 and is taken into the computer system 16.

[0022] The reference work imaging unit 12 captures a reference work image, which is an image of the reference work RW. The reference work imaging unit 12 has a similar configuration to the measurement work imaging unit 11. That is, the reference work imaging unit 12 includes an imaging element 121 similar to the imaging element 111, and an optical system 122 similar to the optical system 112. The reference work imaging unit 12 is disposed so that at least a part of the reference work placement area 142 on the stage 14, where the reference work RW is placed, falls within the imaging field of view. The optical system 122 forms an image of the reference work RW on the light receiving surface of the imaging element 121. The image of the reference work RW is converted into an image (image data) by the imaging element 121, and is taken into the computer system 16.

[0023] The light source 13 irradiates the measurement work MW and the reference work RW with light under common illumination conditions when capturing images of the measurement work MW and the reference work RW. Therefore, if there is a fluctuation in the light amount of the light source 13 during imaging by the measurement work imaging unit 11 and the reference work imaging unit 12, the image captured by the measurement work imaging unit 11 and the image captured by the reference work imaging unit 12 are affected by the fluctuation in the light amount in the same way.

[0024] The reference work imaging unit 12 is disposed so that the optical axis of the optical system 122 is parallel to the optical axis of the optical system 112. Furthermore, the measurement work imaging unit 11 and the reference work imaging unit 12 are disposed at equidistant positions from the stage 14. The measurement work imaging unit 11 and the reference work imaging unit 12 are configured so that they can move up and down integrally in the height direction (Z-axis direction) under the control of the computer system 16. With this configuration, the measurement work imaging unit 11 and the reference work imaging unit 12 are equally susceptible to image disturbance (blurring) that accompanies the movement of the stage 14 during imaging.

[0025] 1, the measurement work imaging unit 11 and the reference work imaging unit 12 are preferably connected by a connecting member 15 formed of a highly rigid material. The connecting member 15 should have a high enough rigidity to have a resonance frequency higher than the frequency of vibration expected during measurement with the image measuring device 1. In this way, the measurement work imaging unit 11 and the reference work imaging unit 12 vibrate in conjunction with each other, so that even if a movement such as vibration occurs on the imaging unit 10 side rather than the stage 14 side during imaging, the correction method of the present invention can remove image blurring caused by vibration.

[0026] The computer system 16 includes a computer main unit 160, a keyboard 161, a mouse 162, and a display 163. Fig. 2 is a block diagram showing the configuration of the computer main unit 160. The computer main unit 160 includes a CPU (Central Processing Unit) 164 which serves as the center of control, a storage unit 165, a work memory 166, interfaces (indicated as "IF" in Fig. 2) 167 and 168, and a display control unit 169 which controls the display on the display 163.

[0027] Operator instruction information input from the keyboard 161 or mouse 162 is input to the CPU 164 via the interface 167. The interface 168 is connected to the imaging unit 10, the light source 13, the stage 14, etc., and supplies various control signals from the CPU 164 to the imaging unit 10, the light source 13, the stage 14, etc., and receives various status information and measurement results from the imaging unit 10, the light source 13, the stage 14, etc. and inputs them to the CPU 164.

[0028] The display control unit 169 displays the image captured by the imaging unit 10 on the display 163. Furthermore, the display control unit 169 displays on the display 163, in addition to the image captured by the imaging unit 10, a user interface for inputting control instructions to the image measuring instrument 1, a user interface of a tool for analyzing the captured image, and the like.

[0029] The work memory 166 provides a working area for various processes of the CPU 164. The storage unit 165 is configured with, for example, a hard disk drive, a RAM, etc., and stores programs executed by the CPU 164, image data captured by the imaging unit 10, etc. The storage unit 165 also stores a correction program for executing a correction process described below, and a reference-referenced work image used in the correction process.

[0030] The CPU 164 controls each part of the image measuring machine 1 based on various input information via each interface, instructions from the operator, a measurement definition program (part program) stored in the memory unit 165, etc., and performs various processes such as setting the movement path of the stage 14, adjusting the movement speed and exposure time, adjusting the light intensity of the light source 13, imaging by the measurement work imaging unit 11 and reference work imaging unit 12, and correcting the measurement work image.

[0031] In the following, the capturing of an image using the above-mentioned image measuring machine 1 and the correction process for the measured workpiece image obtained by this capturing will be described.

[0032] [Image capture] Prior to imaging, the measurement work MW is placed in the measurement work placing area 141 of the stage 14, and the reference work RW is placed at a position in the reference work placing area 142 corresponding to the position where the measurement work MW is placed. "A position in the reference work placing area 142 corresponding to the position where the measurement work MW is placed" means a position that is the center of the imaging field of the reference work imaging unit 12 when the measurement work MW is positioned at the center of the imaging field of the measurement work imaging unit 11. As a result, the measurement work MW is included in the imaging field of the measurement work imaging unit 11, and the reference work RW is included in the imaging field of the reference work imaging unit 12.

[0033] Next, the measurement work MW and the reference work RW placed on the stage 14 are simultaneously imaged by the measurement work imaging unit 11 and the reference work imaging unit 12. When imaging, the measurement work MW and the reference work RW are irradiated with illumination light from a common light source 13. In addition, the measurement work imaging unit 11 and the reference work imaging unit 12 image under the same imaging conditions such as the magnification of the optical system, the height position, the exposure timing, and the exposure time. The image of the measurement work MW (hereinafter referred to as the measurement work image) and the image of the reference work RW (hereinafter referred to as the reference work image) obtained by imaging under such conditions are equally affected by the vibration of the stage 14 and the imaging unit 10 and the light amount fluctuation of the light source 13. The measurement work image and the reference work image are taken into the computer system 16, and correction processing is performed on the measurement work image.

[0034] [Correction Processing] The computer system 16 executes a correction program to correct the measurement work image based on the reference work image captured simultaneously with the measurement work image as described above and the standard reference work image previously stored in the storage unit 165, and performs correction processing to remove disturbances (i.e., blur, shaking, etc.) from the measurement work image. In other words, the computer system 16 functions as the correction unit in the present invention.

[0035] Here, the reference reference work image used in the correction process is an image of the reference work RW that is ideal and free of blurring or blurring. The reference reference work image may be an image of the reference work RW that is actually captured under ideal imaging conditions (for example, using a stage and imaging unit with sufficiently suppressed vibrations and a light source with a stable amount of light). Alternatively, it may be an image of the reference work RW that is generated from design data such as CAD data of the reference work RW.

[0036] In the following explanation, the image data of the measurement workpiece image is referred to as MWI, the image data of the reference workpiece image is referred to as RWI, and the image data of the standard reference workpiece image is referred to as RWI ref The corrected image data of the measured workpiece is called MWI correct Then, the Fourier transform of these image data is called function F(), and the inverse Fourier transform is called function F -1 For example, the Fourier transform of the measured workpiece image MWI is expressed as F(MWI). The Fourier transform and inverse Fourier transform can be efficiently determined using a fast Fourier transform (FFT) algorithm.

[0037] In the correction process in this embodiment, the measurement workpiece image MWI, the reference workpiece image RWI, and the standard reference workpiece image RWI ref Based on this, the corrected measurement workpiece image MWI correct , MWI correct =F -1 (F(MWI) · F(RWI ref ) / F(RWI)

[0038] Measurement workpiece image MWI corrected using the above formula correct The reason why is explained below. The influence of the movement during imaging (movement, vibration, etc.), the light amount fluctuation, etc. is K, and the reference work image RWI is the standard reference work image RWI ref and K, it can be expressed as equation (1). RWI=K*RWI ref …(1) Here, * means convolution.

[0039] The convolution of equation (1) is expressed as follows in the frequency domain: ref Therefore, if we Fourier transform both sides of equation (1), we get equation (2). F(RWI) = F(K) F(RWI ref ) …(2)

[0040] Solving equation (2) for F(K) gives equation (3). F(K)=F(RWI) / F(RWI ref ) …(3)

[0041] Equation (3) expresses the influence of movement during imaging, light intensity fluctuation, etc., K (more precisely, its Fourier transform), as the function of the reference work image RWI and the standard reference work image RWI ref This means that it can be inferred from

[0042] During imaging, the measurement workpiece image MWI is also affected by the same movements and light intensity fluctuations as the reference workpiece image RWI. Therefore, an ideal measurement workpiece image (i.e., a measurement workpiece image MWI with blur and blur removed by correction) is correct ) plus the influence of movement, light intensity fluctuation, etc., K, results in the measured workpiece image MWI. This can be expressed mathematically as equations (4) and (5), similar to equations (1) and (2) for the reference workpiece image. MWI=K*MWI correct …(4) F(MWI) = F(K) F(MWI correct ) …(5)

[0043] Equation (5) is expressed as F(MWI correct ) gives equation (6). F(MWI correct ) = F(MWI) / F(K) …(6)

[0044] Substituting equation (3) into equation (6) gives equation (7). F(MWI correct )=F(MWI)·F(RWI ref ) / F(RWI) …(7)

[0045] Next, by performing an inverse Fourier transform on both sides of equation (7), the measured workpiece image MWI with blur and blur removed is obtained. correct is expressed as equation (8). MWI correct =F -1 (F(MWI) · F(RWI ref ) / F(RWI))…(8)

[0046] Using this formula (8), the corrected measured workpiece image MWI correct The measurement workpiece image MWI and the reference workpiece image RWI obtained by imaging, and the known reference workpiece image RWI ref It can be calculated using:

[0047] The computer system 16 outputs the corrected image of the measured workpiece MW (MWI correct ) is displayed on the display 163. Then, a measurement tool for analyzing the image displayed on the display 163 is applied to the image by a user operation or automatic processing by a program, and measurements are made at desired locations.

[0048] According to the image measuring device 1 of this embodiment described above, by performing correction processing to compare the standard reference work image with the imaged reference work, it is possible to estimate the effects of changes in light intensity during imaging and movements (movement, vibration, etc.) of the stage 14 and imaging unit 10, and to remove disturbances (blurring, shaking, etc.) in the measured work image.

[0049] Second Embodiment In the above-described first embodiment, the measurement work imaging unit 11 and the reference work imaging unit 12 each had an imaging element (111, 121) and an optical system (112, 122). That is, two sets of imaging elements and optical systems were provided for imaging the measurement work MW and for imaging the reference work RW. In contrast, the image measuring machine 1 according to the second embodiment is characterized in that one set of imaging elements and optical system is shared for imaging the measurement work MW and for imaging the reference work RW. Note that other than that, it is the same as the image measuring machine 1 of the first embodiment, so a description thereof will be omitted here.

[0050] 3 is a functional block diagram showing the configuration of the image measuring machine 1 in the second embodiment. The image measuring machine 1 includes a stage 14, an imaging unit 10, a light source 13 that irradiates light onto the measurement workpiece MW and the reference workpiece RW, and a computer system 16.

[0051] The imaging unit 10 of this embodiment has an imaging element 101 and an optical system 102. The imaging unit 10 is disposed so that both a measurement work placement area 141 on the stage 14 where the measurement work MW is placed, and a reference work placement area 142 on which the reference work RW is placed, are within the imaging field of view. The imaging element 101 is, for example, a two-dimensional image sensor such as a CCD or CMOS. The optical system 102 forms images of the measurement work MW and the reference work RW on the light receiving surface of the imaging element 101. The images of the measurement work MW and the reference work RW are converted into images (image data) by the imaging element 101 and are taken into the computer system 16.

[0052] Therefore, the imaging unit 10 realizes a measurement work imaging section 11 that captures an image of the measurement work MW and a reference work imaging section 12 that captures an image of the reference work RW by using a pair of imaging element 101 and optical system 102. With this configuration, the image obtained by imaging using the imaging element 101 includes both the measurement work image and the reference work image, so the imaging conditions for the measurement work MW and the imaging conditions for the reference work RW by the reference work imaging section 12 can be automatically matched. In addition, there is no need to provide a connecting member 15 for making the measurement work imaging section 11 and the reference work imaging section 12 vibrate in the same way, and the configuration of the image measuring machine 1 can be simplified.

[0053] In the computer system 16, a portion of the image captured by the imaging unit 10 that includes the measurement workpiece MW is cut out as a measurement workpiece image, and a portion of the image of the reference workpiece RW is cut out as a reference workpiece image. Then, using the measurement workpiece image and reference workpiece image cut out in this way, a correction process similar to that in the first embodiment is performed to remove disturbances in the measurement workpiece image (blurring, shaking, etc.).

[0054] The computer system 16 displays the corrected image of the measurement workpiece MW on the display 163. Then, a measurement tool for analyzing the image displayed on the display 163 is applied to the image by a user operation or automatic processing by a program, and the desired location is measured.

[0055] In the image measuring machine 1 of this embodiment configured as described above, like the image measuring machine 1 of the first embodiment, it is possible to estimate the effects of changes in light intensity during imaging and the movements (movement and vibration) of the stage 14 and imaging unit 10, and to remove disturbances (blurring, shaking, etc.) in the measured work image.

[0056] [Modifications of the embodiment] The present invention is not limited to the above-described embodiment, and the present invention includes modifications and improvements within the scope of the present invention that can achieve the object of the present invention.

[0057] In each of the above embodiments, an example has been described in which one reference work RW is placed in the reference work placing area 142 of the stage 14, but multiple reference workpieces RW may be placed in the reference work placing area 142. For example, as shown in Fig. 4, when there are multiple measurement points (points to be imaged) on the measurement work MW, it is advisable to place the reference work RW at each position in the reference work placing area 142 corresponding to each measurement point of the measurement work MW placed in the measurement work placing area 141. In the example of Fig. 4, there are three measurement points (MP1 to MP3) on the measurement work MW, and three reference works RW1 to RW3 are placed in the reference work placing area 142 corresponding to each measurement point.

[0058] Then, based on a measurement definition program (part program) or the like, the stage 14 may be moved and images may be taken sequentially at each measurement point without stopping. In this way, since there is no need to stop at each measurement point, the time required for imaging can be shortened. Also, when each measurement point enters the imaging field of the measurement work imaging unit 11, the reference work RW at the corresponding position enters the imaging field of the reference work imaging unit, so that the reference work image can be reliably imaged together with the measurement work image. And, the blurring of the measurement work image caused by moving without stopping during imaging can be removed by correction processing to obtain a clear measurement work image.

[0059] In addition, in the above second embodiment, the computer system 16 extracts a measurement work image and a reference work image from the image captured by the imaging unit 10, but the imaging unit 10 may output the image obtained in a single imaging session separately as a measurement work image and a reference work image.

[0060] Furthermore, those embodiments or specific examples in which a person skilled in the art has appropriately added or deleted components or modified the design are also included within the scope of the present invention as long as they incorporate the gist of the present invention. [Explanation of symbols]

[0061] 1. Image measuring device 10. Imaging unit 11 Measurement workpiece imaging unit 12 Reference workpiece imaging unit 101, 111, 121 Image sensor 102, 112, 122 optical system 13 Light source 14 Stages 15 Connecting members 16 Computer Systems MW measurement workpiece RW Reference Work

Claims

1. a stage having a measurement work placement area on which a measurement work, which is a measurement object, is placed and a reference work placement area on which a reference work is placed; a measurement work imaging unit that captures a measurement work image that is an image of the measurement work placed in the measurement work placement area; a reference work imaging unit that captures a reference work image, which is an image of the reference work placed in the reference work placement area, at the same time as the measurement work image is captured by the measurement work imaging unit; A correction unit that corrects the measurement work image captured by the measurement work imaging unit based on the reference work image captured by the reference work imaging unit and a standard reference work image of the reference work; An image measuring machine comprising:

2. The measurement workpiece image is MWI, the reference workpiece image is RWI, and the standard reference workpiece image is RWI ｒｅｆ , the application of the Fourier transform is represented by the function F(), and the application of the inverse Fourier transform is represented by the function F －１ The corrected image data MWI of the measured workpiece image is expressed as () ｃｏｒｒｅｃｔ of, M.O.W. ｃｏｒｒｅｃｔ =F －１ (F(MWI)・F(RWI) ｒｅｆ ) / F(RWI)) 2. The image measuring instrument according to claim 1, wherein the measurement is performed by the following formula:

3. 3. The image measuring machine according to claim 1, further comprising a light source that irradiates the measurement workpiece and the reference workpiece with light under common illumination conditions when capturing the measurement workpiece image and the reference workpiece image.

4. 3. The image measuring machine according to claim 1, further comprising a highly rigid connecting member that connects the measurement work imaging unit and the reference work imaging unit.

5. 3. The image measuring machine according to claim 1, wherein the measurement workpiece imaging section and the reference workpiece imaging section are realized by sharing a set of imaging element and optical system.

6. 3. The image measuring instrument according to claim 1, wherein the standard reference workpiece image is an image of the reference workpiece captured under ideal imaging conditions.

7. 3. The image measuring machine according to claim 1, wherein the standard reference workpiece image is an image generated from design data of the reference workpiece.

8. A program for causing a computer to function as the correction unit according to claim 1 or 2.

Images