A method and device for online three-dimensional shape precision measurement

Abstract

The present invention discloses an online three-dimensional shape precision measurement method and device, the measurement method comprises the following steps: 1) obtaining interference pattern; 2) pattern preprocessing, preprocessing the interference pattern to improve the pattern quality; 3) phase extraction: using a phase numerical reconstruction method to obtain the phase distribution of the interference pattern, and then using a quality-guided phase unwrapping algorithm to perform phase unwrapping to obtain the phase information of the interference pattern; 4) three-dimensional reconstruction: combining the parameter information of the optical system to convert the phase information into the three-dimensional surface shape of the object to be measured, and then using computer vision technology to optimize the three-dimensional surface shape through surface fitting, and improve the surface detail representation capability of the three-dimensional surface shape. The present invention realizes non-contact measurement while measuring quickly and accurately, meets the needs of online three-dimensional measurement, and has important application value and practical significance.

Description

Technical Field

[0001] The present invention relates to the technical field of three-dimensional shape measurement, and in particular to an online three-dimensional shape precision measurement method and device. Background Art

[0002] In modern industrial production, scientific research and medical diagnosis, there is an increasing demand for precise three-dimensional measurement of the surface or internal structure of objects. This measurement technology is crucial for material defect analysis, precision component manufacturing, biological tissue imaging and other fields. However, traditional measurement methods such as interferometry, scanning measurement, confocal microscopy and laser triangulation technology have certain limitations in terms of measurement accuracy, three-dimensional reconstruction speed, non-contact and online measurement capabilities.

[0003] Interferometry uses a coherent light source to achieve high-precision and high spatial resolution measurements through interference fringe analysis. However, this method requires multiple steps, is complex to operate, is sensitive to environmental vibration and noise, is not suitable for online real-time measurement, and the measurement process is time-consuming.

[0004] Scanning measurement collects surface data point by point through a probe (such as an atomic force microscope) or laser scanning to achieve high-precision measurement, but it is not suitable for samples of different sizes and materials, and the scanning process takes a long time and cannot be measured online. In addition, the probe may damage the surface of the sample being measured, and the complex operation and calibration requirements limit its scope of application.

[0005] The confocal microscope used for confocal position measurement can provide nanometer-level vertical resolution and micrometer-level lateral resolution, and can be combined with fluorescent markers to achieve multi-dimensional imaging. However, its scanning speed is slow, it is not suitable for large-area rapid measurement, and the measurement depth is limited.

[0006] In summary, existing measurement methods are unable to cope with complex and ever-changing measurement requirements. In particular, the shortcomings of traditional methods are more obvious in application scenarios that require fast, accurate, and non-contact online real-time three-dimensional measurement. Therefore, the development of an online three-dimensional morphology precision measurement method and device that can efficiently solve the above problems has important application value and practical significance. Summary of the invention

[0007] In view of the above-mentioned defects or deficiencies in the prior art, it is desired to provide an online three-dimensional morphology precision measurement method and device, which can realize non-contact measurement while measuring quickly and accurately, meet the needs of online three-dimensional measurement, and have important application value and practical significance.

[0008] The present invention provides an online three-dimensional shape precision measurement method, comprising the following steps:

[0009] 1) Obtaining interference pattern;

[0010] 11) The laser emits a plane wave after being expanded by a beam expander, and the plane wave generates two beams of light through a beam splitter;

[0011] 12) After a beam of light is reflected by the reflector, it is reflected by the beam splitter as reference light and irradiates the target surface of the CCD camera;

[0012] 13) Another beam of light is directed toward the object to be measured. The reflected light of the object is incident on the target surface of the CCD camera after passing through the beam splitting environment, and interferes with the reference light.

[0013] 14) adjusting the angle of the reflector according to the reflected light, that is, adjusting the interference condition between the reference light and the reflected light to maximize the contrast and clarity of the interference pattern; then collecting information through a CCD camera and forming a digital interference pattern;

[0014] 2) pattern preprocessing, preprocessing the interference pattern to improve the pattern quality;

[0015] 3) Phase extraction;

[0016] A phase numerical reconstruction method is used to obtain the phase distribution of the interference pattern, and then a quality-guided phase unwrapping algorithm is used to perform phase unwrapping to obtain the phase information of the interference pattern;

[0017] The phase numerical reconstruction method comprises the following steps:

[0018] 31) The numerical reconstruction formula of the complex amplitude on the image plane is:

[0019] U I (x,y,z)=DFT -1 {G(m,n,0)·H z (m,n)};

[0020] Among them, z is the reconstruction distance; m and n are the horizontal and vertical coordinates in the frequency domain respectively;

[0021] G(m,n,0) is the frequency domain expression of the product of the virtual image light wave field of the object and the conjugate reference light wave;

[0022] H z (m,n) is the discrete transfer function of the angular spectrum;

[0023] 32)

[0024] Among them, j is the imaginary unit, that is,

[0025] λ is the wavelength;

[0026] M, N are the number of image pixels, Δx, Δy are the pixel sizes;

[0027] 33) Phase distribution of the object under test for:

[0028]

[0029] 4) 3D reconstruction;

[0030] The phase information is converted into the three-dimensional surface morphology of the object under test in combination with the parameter information of the optical system, and then the three-dimensional surface morphology is optimized by surface fitting using computer vision technology to improve the surface detail representation capability of the three-dimensional surface morphology.

[0031] Furthermore, in the step 2), the pattern preprocessing includes the following steps:

[0032] 21) performing wavelet transform image denoising processing on the interference pattern to reduce the noise in the interference pattern;

[0033] 22) Performing background correction on the interference pattern to eliminate the non-uniform background brightness caused by the light source or the environment and ensure the clarity of the interference fringes.

[0034] Furthermore, the phase distribution The phase information after unfolding using the mass-guided phase unwrapping algorithm is expressed as φ'(x, y); the three-dimensional surface morphology z(x, y) is:

[0035]

[0036] Where θ is the angle between the reference light and the reflected light.

[0037] In addition, the present invention also provides a measuring device for the above-mentioned online three-dimensional shape precision measurement method, including a detection platform, a light source mechanism, a beam splitter, a reflector and an image acquisition device;

[0038] The light source mechanism is arranged above the detection platform and is used to emit plane waves;

[0039] The beam splitter is arranged above the detection platform and located on the emission path of the light source mechanism, and is used to split the plane wave into two beams of light, so that one beam of light is emitted to the object to be detected on the detection platform, and the other beam of light is emitted to the reflector;

[0040] The reflector is arranged above the detection platform, located on the side of the beam splitter away from the light source mechanism, and is used to reflect the light beam so that it is reflected by the beam splitter and then directed to the image acquisition device;

[0041] The image acquisition device is arranged above the beam splitter and is used for acquiring image information.

[0042] Furthermore, the light source mechanism includes a laser and a beam expander arranged at the emitting end of the laser.

[0043] Furthermore, the reflector is installed above the detection platform through an angle adjustment mechanism.

[0044] Furthermore, the image acquisition device is a CCD camera.

[0045] Compared with the prior art, the beneficial effects of the present invention are:

[0046] The present invention improves the accuracy and resolution of measurement by obtaining the optimal interference pattern. A fast image processing and three-dimensional reconstruction algorithm for digital holograms is developed and introduced to quickly extract accurate three-dimensional surface morphology information from the interference pattern, greatly improving the speed of measurement and analysis. High-precision, high-speed and non-contact online three-dimensional morphology measurement is achieved, meeting the needs of online three-dimensional measurement, and is applicable to a wide range of materials and complex surface morphologies, with important application value and practical significance.

[0047] It should be understood that the contents described in the summary of the invention are not intended to limit the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0049] Figure 1 A flowchart of the measurement method is shown;

[0050] Figure 2 Schematic diagram of the measurement device.

[0051] Numbers in the figure: 1. Test table; 2. Light source mechanism; 3. Beam splitter; 4. Reflector; 5. Image acquisition device; 6. Object to be tested;

[0052] 21. Laser; 22. Beam expander. DETAILED DESCRIPTION

[0053] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It should also be noted that, for ease of description, only the parts related to the invention are shown in the accompanying drawings.

[0054] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0055] Example 1

[0056] Please refer to Figure 1-2 The embodiment of the present invention provides an online three-dimensional shape precision measurement method, comprising the following steps:

[0057] 1) Obtaining interference pattern;

[0058] 11) The laser emits a plane wave after being expanded by a beam expander, and the plane wave generates two beams of light through a beam splitter;

[0059] 12) After a beam of light is reflected by the reflector, it is reflected by the beam splitter as reference light and irradiates the target surface of the CCD camera;

[0060] 13) Another beam of light is directed toward the object to be measured. The reflected light of the object is incident on the target surface of the CCD camera after passing through the beam splitting environment, and interferes with the reference light.

[0061] 14) Adjust the angle of the reflector according to the reflected light, that is, adjust the interference condition between the reference light and the reflected light, maximize the contrast and clarity of the interference pattern, and help improve the accuracy and resolution of the measurement; then collect information through the CCD camera and form a digital interference pattern;

[0062] 2) Pattern preprocessing: preprocess the interference pattern to improve the pattern quality;

[0063] 21) Perform wavelet transform image denoising on the interference pattern to reduce the noise in the interference pattern and retain more effective information;

[0064] 22) Perform background correction on the interference pattern to eliminate the non-uniform background brightness caused by the light source or environment and ensure the clarity of the interference fringes;

[0065] 3) Phase extraction;

[0066] Phase information is the key basis for 3D surface topography reconstruction. The purpose of phase extraction is to accurately extract the phase change of the object surface from the optical interference pattern.

[0067] The phase distribution of the interference pattern is obtained by using the phase numerical reconstruction method;

[0068] 31) The numerical reconstruction formula of the complex amplitude on the image plane is:

[0069] U I (x,y,z)=DFT -1 {G(m,n,0)·H z(m,n)};

[0070] Among them, z is the reconstruction distance; m and n are the horizontal and vertical coordinates in the frequency domain respectively;

[0071] G(m,n,0) is the frequency domain expression of the product of the virtual image light wave field of the object and the conjugate reference light wave;

[0072] H z (m,n) is the discrete transfer function of the angular spectrum;

[0073] 32)

[0074] Among them, j is the imaginary unit, that is,

[0075] λ is the wavelength;

[0076] M, N are the number of image pixels, Δx, Δy are the pixel sizes;

[0077] 33) Phase distribution of the object under test for:

[0078]

[0079] The phase at this time is a wrapped phase, and then the quality-guided phase unwrapping algorithm is used to unwrap the phase to obtain the phase information φ'(x, y) of the interference pattern; this effectively avoids the wrong unwrapping path and ensures the continuity of the phase;

[0080] 4) 3D reconstruction;

[0081] The phase information is converted into a three-dimensional surface morphology z(x,y) of the object under test by combining the parameter information of the optical system (such as the wavelength of the light source and the geometric characteristics of the imaging system);

[0082]

[0083] Where θ is the angle between the reference light and the reflected light;

[0084] Then, computer vision technology is used to optimize the three-dimensional surface morphology through surface fitting to improve the surface detail representation capability of the three-dimensional surface morphology.

[0085] In this embodiment, the application obtains the optimal interference pattern by adjusting the interference conditions between the reference light and the reflected light, thereby improving the accuracy and resolution of the measurement. A fast image processing and three-dimensional reconstruction algorithm for digital holograms has been developed and introduced to quickly extract accurate three-dimensional surface morphology information from the interference pattern, greatly improving the speed of measurement and analysis. High-precision, high-speed and non-contact online three-dimensional morphology measurement is achieved, meeting the needs of online three-dimensional measurement, and is applicable to a wide range of materials and complex surface morphologies, with important application value and practical significance.

[0086] Example 2

[0087] Please refer to Figure 2 , an embodiment of the present invention further provides a measuring device for the above-mentioned online three-dimensional shape precision measurement method, comprising a detection platform 1, a light source mechanism 2, a beam splitter 3, a reflector 4 and an image acquisition device 5;

[0088] The light source mechanism 2 is arranged above the detection platform 1, and includes a laser 21 and a beam expander 22 arranged at the emission end of the laser 21, and is used to emit a plane wave;

[0089] The beam splitter 3 is arranged above the detection platform 1 and located on the emission path of the light source mechanism 2, and is used to split the plane wave into two beams of light, so that one beam of light is emitted to the object to be measured 6 on the detection platform 1, and the other beam of light is emitted to the reflector 4;

[0090] The reflector 4 is installed above the detection platform 4 through an angle adjustment mechanism, and is located on the side of the beam splitter 3 away from the light source mechanism 2, and is used to reflect the light beam so that it is reflected by the beam splitter 3 and then emitted to the line image acquisition device 5;

[0091] The image acquisition device 5 is arranged above the beam splitter 3 and is used to acquire image information; preferably, the image acquisition device is a CCD camera.

[0092] In this embodiment, the present application adopts a "cross" optical path. The reflection angle of the reflector 4 can be adjusted by an angle adjustment mechanism, and then the interference conditions are adjusted according to the surfaces of different objects to be measured to obtain interference patterns with high contrast and clarity.

[0093] The test bench 1 is provided with a mounting frame for mounting optical devices. In some embodiments, the angle adjustment mechanism includes a bracket, a fixing seat and a locking member; the reflector 4 is fixedly mounted on one side of the bracket, and a connecting seat is provided on the other side of the bracket, and the connecting seat is rotatably connected to the fixing seat through a shaft, and the locking member is provided between the connecting seat and the fixing seat. After loosening the locking member, the bracket can be rotated to adjust the reflection angle of the reflector 4. After the adjustment is completed, the locking member is tightened to lock the connecting seat and the fixing seat, which is convenient for adjustment and stable for support.

[0094] When measuring the three-dimensional shape of the object to be measured, first start the light source mechanism 2 and adjust the light intensity, adjust the beam splitter 3 so that the split light is focused on the surface of the object to be measured, and ensure that the image acquisition device 5 is in the correct position to clearly record the holographic image; then adjust the angle of the reflector 4 to ensure that the image acquisition device 5 obtains a clear interference pattern. Then, through fast image processing and three-dimensional reconstruction algorithms, accurate three-dimensional surface shape information is quickly extracted from the interference pattern, greatly improving the speed of measurement and analysis.

[0095] In the description of this specification, the terms "connection", "installation", "fixation" and the like should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0096] In the description of this specification, the description of the terms "one embodiment", "some embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0097] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An online three-dimensional shape precision measurement method, characterized in that: The steps include: 1) Obtaining interference pattern; 11) The laser emits a plane wave after being expanded by a beam expander, and the plane wave generates two beams of light through a beam splitter; 12) After a beam of light is reflected by the reflector, it is reflected by the beam splitter as reference light and irradiates the target surface of the CCD camera; 13) Another beam of light is directed toward the object to be measured. The reflected light of the object is incident on the target surface of the CCD camera after passing through the beam splitting environment, and interferes with the reference light. 14) adjusting the angle of the reflector according to the reflected light, that is, adjusting the interference condition between the reference light and the reflected light to maximize the contrast and clarity of the interference pattern; then collecting information through a CCD camera and forming a digital interference pattern; 2) pattern preprocessing, preprocessing the interference pattern to improve the pattern quality; 3) Phase extraction; A phase numerical reconstruction method is used to obtain the phase distribution of the interference pattern, and then a quality-guided phase unwrapping algorithm is used to perform phase unwrapping to obtain the phase information of the interference pattern; The phase numerical reconstruction method comprises the following steps: 31) The numerical reconstruction formula of the complex amplitude on the image plane is: U I (x,y,z)=DFT -1 {G(m,n,0)·H z (m,n)}; Among them, z is the reconstruction distance; m and n are the horizontal and vertical coordinates in the frequency domain respectively; G(m,n,0) is the frequency domain expression of the product of the virtual image light wave field of the object and the conjugate reference light wave; H z (m,n) is the discrete transfer function of the angular spectrum; 32) Among them, j is the imaginary unit, that is, λ is the wavelength; M, N are the number of image pixels, Δx, Δy are the pixel sizes; 33) Phase distribution of the object under test for: 4) 3D reconstruction; The phase information is converted into the three-dimensional surface morphology of the object under test in combination with the parameter information of the optical system, and then the three-dimensional surface morphology is optimized by surface fitting using computer vision technology to improve the surface detail representation capability of the three-dimensional surface morphology.

2. The online three-dimensional shape precision measurement method according to claim 1 is characterized in that: In the step 2), the pattern preprocessing includes the following steps: 21) performing wavelet transform image denoising processing on the interference pattern to reduce the noise in the interference pattern; 22) Performing background correction on the interference pattern to eliminate the non-uniform background brightness caused by the light source or the environment and ensure the clarity of the interference fringes.

3. The online three-dimensional shape precision measurement method according to claim 1 is characterized in that: The phase distribution The phase information after unfolding using the mass-guided phase unwrapping algorithm is expressed as φ'(x, y); the three-dimensional surface morphology z(x, y) is: Where θ is the angle between the reference light and the reflected light.

4. A measuring device for the online three-dimensional shape precision measurement method according to any one of claims 1 to 3, characterized in that: It comprises a detection platform (1), a light source mechanism (2), a beam splitter (3), a reflector (4) and an image acquisition device (5); The light source mechanism (2) is arranged above the detection platform (1) and is used to emit plane waves; The beam splitter (3) is arranged above the detection platform (1) and located on the emission path of the light source mechanism (2), and is used to split the plane wave into two beams of light, so that one beam of light is emitted to the object to be detected (6) on the detection platform (1), and the other beam of light is emitted to the reflector (4); The reflector (4) is arranged above the detection platform (4) and is located on a side of the beam splitter (3) away from the light source mechanism (2), and is used to reflect the light beam so that it is reflected by the beam splitter (3) and then emitted to the image acquisition device (5); The image acquisition device (5) is arranged above the beam splitter (3) and is used for acquiring image information.

5. The measuring device according to claim 4, characterized in that The light source mechanism (2) comprises a laser (21) and a beam expander (22) arranged at the emission end of the laser (21).

6. The measuring device according to claim 4, characterized in that The reflector (4) is installed above the detection platform (1) via an angle adjustment mechanism.

7. The measuring device according to claim 4, characterized in that The image acquisition device (5) is a CCD camera.

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