A method and system for three-dimensional surface topography measurement

Abstract

The application provides a kind of three-dimensional surface topography measurement method and system, the method comprises: the structure light of a group of preset phase shift stripe patterns is sequentially projected to the surface of vertical scanning object to be measured, to obtain a group of capture images carrying object height information;Intensity value of any pixel position in a group of capture images is extracted, to obtain the intensity curve of any pixel position in the vertical scanning process;According to the intensity curve of each pixel position in the vertical scanning process, the envelope curve of each corresponding pixel position is obtained;One of all envelope curves is taken as a reference envelope curve, and the other envelope curves are taken as matching envelope curves, the reference envelope curve is matched with each matching envelope curve, and the relative height information of the corresponding each pixel position is determined.The three-dimensional surface topography measurement method and system provided by the application have the advantages of high measurement efficiency and high measurement accuracy compared with the prior art.

Description

Technical Field

[0001] This invention relates to the field of three-dimensional surface topography measurement technology, and in particular to a three-dimensional surface topography measurement method and system. Background Technology

[0002] Structured light illumination microscopy is a suitable method for high-precision reconstruction of complex surface morphology. This method achieves non-point scanning, incoherent illumination, and pinhole-free measurement of microscopic surface morphology. The technique utilizes a three-dimensional wide-field-of-view and high-resolution tomographic imaging method and apparatus. Structural patterns and planar patterns are loaded onto a digital micromirror device (DMD). Structured light is sequentially generated by illuminating the DMD with a light source and relayed onto the sample. Structured light illumination images captured by the objective lens are analyzed to obtain optical tomographic images. Further peak extraction of the tomographic curves at each point yields the reconstructed surface morphology.

[0003] However, since the reconstruction of surface morphology depends on the calculation of tomographic images, multiple phase-shifting structured light illumination images are often required to be projected at the same axial position during vertical scanning, resulting in low system measurement efficiency. In addition, the accuracy of sample measurement in existing technologies depends heavily on peak localization algorithms. Although the commonly used Gaussian fitting algorithm has the characteristics of high accuracy, it has a large computational load, which affects system efficiency and the measurement accuracy is not high.

[0004] Therefore, there is an urgent need for a technical solution for measuring three-dimensional surface morphology with high measurement efficiency and accuracy. Summary of the Invention

[0005] This invention provides a three-dimensional surface topography measurement method and system to address the shortcomings of low efficiency and accuracy in existing three-dimensional surface topography measurement methods, and achieves high-precision and high-efficiency measurement of three-dimensional surface topography.

[0006] In a first aspect, the present invention provides a method for measuring three-dimensional surface topography, comprising:

[0007] Structured light with a pre-set set of phase-shifting fringe patterns is sequentially projected onto the surface of the vertically scanned object to obtain a set of captured images carrying the object's height information. During the vertical scan, the vertical scan of the object is synchronized with the switching of the phase-shifting fringe patterns, and each vertical scan position corresponds to a phase-shifting fringe pattern.

[0008] By extracting the intensity values ​​of any pixel location in a set of captured images, the intensity curve of that pixel location during the vertical scanning process is obtained;

[0009] Based on the intensity curve of each pixel position during the vertical scanning process, obtain the envelope curve of each pixel position.

[0010] One of the envelope curves is used as the reference envelope curve, and the others are used as matching envelope curves. The reference envelope curve is matched with each matching envelope curve to determine the relative height information of each pixel position.

[0011] This invention provides a three-dimensional surface topography measurement method, which, based on the intensity curve of any pixel position during the vertical scanning process, yields the envelope curve of each pixel position, including: obtaining the envelope curve of the intensity curve using the Hilbert transform method or the Fourier transform method.

[0012] The present invention provides a three-dimensional surface topography measurement method, wherein the phase-shifted fringe pattern is a four-step phase-shifted sinusoidal fringe, and there is a phase shift between each adjacent phase-shifted fringe pattern.

[0013] This invention provides a method for measuring three-dimensional surface topography. Based on the matching degree between a reference envelope curve and any matching envelope curve, the relative height information of the pixel position corresponding to any matching envelope curve is determined. The method includes: selecting a reference sequence containing n discrete data points from the reference envelope curve; wherein the position index of the first point in the reference sequence during the vertical scanning process is F. a The envelope strength value corresponding to each sampling point is I. ai ;

[0014] The degree of matching between the reference sequence and the matching sequence is obtained by calculating the correlation coefficient ix; where the matching sequence is a segment of the matching envelope curve with the same length as the reference sequence, and the envelope strength value of each sampling point in the matching sequence is I. bi ;

[0015] The specific formula for calculating the correlation coefficient is as follows:

[0016]

[0017] in, and These are the mean intensity values ​​of all points in the reference sequence and the matched sequence, respectively.

[0018] Starting from the beginning position of any matching envelope curve, the reference sequence is extracted sequentially by sliding matching, and the correlation coefficient corresponding to each matching sequence of any matching envelope curve is calculated.

[0019] The matching sequence corresponding to the correlation coefficient of the maximum value is taken as the optimal matching sequence;

[0020] Calculate the relative height information of the pixel position corresponding to any matching envelope curve; specifically:

[0021] h=(F a -Fb )*depth;

[0022] Among them, F b is the index of the first point in the optimal matching sequence during the vertical scan, and depth is the vertical scan step.

[0023] This invention provides a three-dimensional surface topography measurement method, in which, when using an image acquisition device for vertical scanning, the difference between the stripe width and the pixel size of the image acquisition device is less than a preset threshold.

[0024] This invention provides a three-dimensional surface topography measurement method, wherein the intensity curve represents the function of the intensity value at a pixel position changing with the vertical scanning position z;

[0025]

[0026] Where I(z) represents the intensity value at the pixel position, I0(z) is the background light intensity, and C0(z) is the contrast at the vertical scan position z. It is a constant at pixel position (x, y).

[0027] Secondly, the present invention also provides a three-dimensional surface topography measurement system, comprising:

[0028] The image capture module is used to sequentially project a set of pre-set phase-shifting fringe patterns onto the surface of the vertically scanned object to obtain a set of captured images carrying the object's height information. During the vertical scan, the vertical scan of the object is synchronized with the switching of the phase-shifting fringe patterns, and each vertical scan position corresponds to a phase-shifting fringe pattern.

[0029] The intensity curve determination module is used to obtain the intensity curve of any pixel location during the vertical scanning process by extracting the intensity values ​​of any pixel location in a set of captured images.

[0030] The envelope curve determination module is used to obtain the envelope curve of each pixel position based on the intensity curve of each pixel position during the vertical scanning process.

[0031] The height information determination module is used to take one of the envelope curves as a reference envelope curve and the other envelope curves as matching envelope curves, and to perform envelope matching between the reference envelope curve and each matching envelope curve to determine the relative height information of each pixel position.

[0032] Thirdly, the present invention provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps of any of the three-dimensional surface topography measurement methods described above.

[0033] Fourthly, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of any of the three-dimensional surface topography measurement methods described above.

[0034] Fifthly, the present invention also provides a computer program product, comprising a computer program, characterized in that, when the computer program is executed by a processor, it implements the steps of any of the three-dimensional surface topography measurement methods described above.

[0035] The three-dimensional surface morphology measurement method and system provided by this invention, compared with the traditional structure illumination microscope, reduces the number of structure illumination image projection acquisitions during axial scanning, omits the step of obtaining tomographic images, and improves information utilization and system measurement efficiency.

[0036] This invention provides a peak localization algorithm based on envelope correlation matching, which improves measurement efficiency while retaining the high resolution characteristic of structured illumination measurement. Envelope matching has the characteristics of high speed and high precision, and is suitable for three-dimensional surface topography measurement. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0038] Figure 1 This is a flowchart illustrating the three-dimensional surface topography measurement method provided by the present invention;

[0039] Figure 2 This is a schematic diagram of the structure of an optical path system provided by the present invention;

[0040] Figure 3 This is a schematic diagram of the axial data provided by the present invention and the fitting curve obtained by using envelope matching to locate the peak.

[0041] Figure 4 This is a schematic diagram of the structure of the three-dimensional surface topography measurement system provided by the present invention;

[0042] Figure 5 This is a schematic diagram of the structure of the electronic device provided by the present invention. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0044] It should be noted that, in the description of the embodiments of the present invention, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0045] The following is combined with Figures 1-5 This invention describes the three-dimensional surface topography measurement method and system provided in the embodiments of the present invention.

[0046] Figure 1 This is a flowchart illustrating the three-dimensional surface topography measurement method provided by the present invention, as shown below. Figure 1 As shown, including but not limited to the following steps:

[0047] Step 101: Project a set of pre-set phase-shifting fringe patterns of structured light onto the surface of the vertically scanned object to obtain a set of captured images carrying the object's height information; wherein, during the vertical scanning process, the vertical scanning of the object is synchronized with the switching of the phase-shifting fringe patterns, and each vertical scanning position corresponds to a phase-shifting fringe pattern.

[0048] As an optional embodiment, the following is combined with Figure 2 The process of acquiring a captured image of a phase-shifted fringe pattern by vertical scanning according to the present invention will be described. Figure 2 This is a schematic diagram of the structure of an optical path system provided by the present invention, as shown below. Figure 2 As shown, the illumination source generated by the Kohler illumination module 1 is directed to the digital micromirror array 3 by the total internal reflection prism 2. The digital micromirror array modulates the light source into pre-programmed structured light. The structured light entering the first sleeve lens 4 is projected onto the surface of the sample 7 through the beam splitter prism 5 and the objective lens 6. After being reflected or scattered by the sample surface, it is imaged onto the area array CMOS camera 9 by the second sleeve lens 8.

[0049] Optionally, based on the above-described optical path system, the present invention provides a device for acquiring the captured image. The device includes a device support, a lead screw mechanism, a stage, an L-shaped platform, the above-described optical path system, a DMD (Digital Micromirror Array), a piezoelectric ceramic driver, a motor, and a CMOS camera.

[0050] The device support frame is arch-shaped and used to securely support the entire instrument. The lead screw mechanism is fixed to the top of the support frame, and a slider is mounted on the lead screw. The forward and reverse rotation of the lead screw controls the up-and-down movement of the slider. The L-shaped platform is fixed to the slider of the lead screw mechanism and is used to house the optical path system. The stage is placed on the platform of the support frame to hold the sample to be tested. The motor is fixed to the upper part of the lead screw mechanism, and the motor shaft is connected to the lead screw of the lead screw mechanism via bearings. The forward and reverse rotation of the motor drives the lead screw of the lead screw mechanism to rotate in both directions, thereby controlling the rise and fall of the L-shaped platform connected to the slider of the lead screw mechanism. The optical path system is arranged on the L-shaped platform.

[0051] The DMD modulates the collimated illumination light reflected from the total internal reflection prism and reflects the modulated structured light into the first sleeve lens 4. The piezoelectric ceramic actuator is mounted between the objective lens and the optical path system to drive the objective lens's vertical movement. The CMOS camera is mounted after the second sleeve lens 8 of the optical path system to capture image information of the structured light reflected from the sample surface.

[0052] Preferably, the external trigger port of the DMD is located near the external trigger receiving port of the camera, and is used to transmit the trigger signal output by the DMD to the receiving end of the CMOS camera.

[0053] Preferably, a field stop is provided on the side of the optical path system near the LED light source to adjust the size of the area to be measured on the sample surface.

[0054] Preferably, an aperture stop is provided on the side of the optical path system near the LED light source to adjust the light intensity in the optical path system.

[0055] Preferably, the pixel size of the CMOS camera is smaller than the micromirror size of the DMD.

[0056] Preferably, the plane containing the CMOS camera's photosensitive element and the plane containing the DMD are conjugate focal planes.

[0057] The steps for image acquisition using the above-mentioned device are as follows:

[0058] (a) Select a set of sinusoidally modulated structured lighting patterns, which consist of sinusoidal fringes, with a phase shift between adjacent lighting patterns.

[0059] Preferably, in step (a), the stripes are sinusoidal stripes with four-step phase shift.

[0060] When using an image acquisition device for vertical scanning, the stripe width is set such that the difference between the stripe width and the pixel size of the image acquisition device is less than a preset threshold.

[0061] Preferably, the stripe width is similar to the pixel size of a CMOS camera, and the period of the sinusoidal stripes is preferably a structured lighting pattern of 8 pixels.

[0062] (b) The structured lighting pattern is loaded into the DMD in sequence, and the light source is emitted by the LED. The light is directed onto the DMD by the total internal reflection prism in the optical path system. The relayed light is modulated into structured light of the lighting pattern by the modulation effect of the DMD.

[0063] (c) The structured light is projected onto the sample surface using the first sleeve lens, beam splitter, and objective lens in the optical path system. The structured light reflected back from the sample surface is imaged onto the photosensitive element of the CMOS camera by the second sleeve lens in the optical path system and is finally collected by the CMOS camera.

[0064] Optionally, in steps (b) and (c) above, the present invention adjusts the light source intensity of the LED lamp to keep the maximum intensity value of the structured light pattern acquired by the CMOS camera at about 90% of the theoretical maximum value.

[0065] (d) During the vertical scanning process, at each position of the piezoelectric ceramic step, the DMD only needs to load one image from the structured illumination pattern, and the CMOS camera acquires the structured light pattern reflected back from the sample surface.

[0066] (e) Repeat step (d) to perform axial scanning of the sample and acquire structured illumination images at each vertical scanning position to obtain a high-resolution stack of three-dimensional images, i.e., captured images.

[0067] Step 102: By extracting the intensity values ​​of any pixel location in a set of captured images, the intensity curve of the any pixel location during the vertical scanning process is obtained.

[0068] It is understandable that the intensity curve can be a function with the vertical scan position as the independent variable and the intensity value at any pixel position (x,y) as the dependent variable.

[0069] Suppose that n images are captured after scanning, and the intensity of each pixel is amplitude modulated, with the light intensity distribution as shown in the following formula:

[0070]

[0071] Among them, I p (x,y,z0) is the modulation value at pixel (x,y) of the image captured by the camera at the vertical scanning position z0, I0(x,y) is the background light intensity, C0(x,y) is the contrast at z0, f0 is the spatial frequency of the projected stripes, and P is the phase shift number.

[0072] Therefore, the light intensity curve of a certain pixel (x,y) can be obtained by taking the intensity value of the pixel (x,y) of each image acquired by axial scanning, and can be expressed as a function that varies with the vertical scanning position z:

[0073]

[0074] Where I0(z) is the background light intensity, and C0(z) is the contrast at the vertical scan position z. It is a constant at pixel (x, y).

[0075] Step 103: Based on the intensity curve of each pixel position during the vertical scanning process, obtain the envelope curve of each pixel position.

[0076] The signal I(z) is similar to the correlation plot in white-light interferometry, and its envelope curve can be solved using well-established methods. There are many different implementation methods, such as Hilbert transform and Fourier transform, which are essentially based on the same principle.

[0077] The Hilbert transform method for obtaining the envelope curve involves constructing an analytic signal, transforming the real signal into a complex signal, taking the original signal as the real part, and the signal after the Hilbert transform as the imaginary part, resulting in:

[0078]

[0079]

[0080] The absolute value of the analytical signal is the required envelope signal.

[0081] For example, Figure 3 This is a schematic diagram of the axial data provided by the present invention and the fitted curve obtained by fitting the peak position using envelope matching. The original signal represents the intensity curve, and the axial response curve of the envelope matching is the envelope curve obtained from the intensity curve. Step 104: Take one of all the envelope curves as the reference envelope curve and the others as the matching envelope curves. Perform envelope matching between the reference envelope curve and each matching envelope curve to determine the relative height information of each corresponding pixel position.

[0082] Optionally, the method provided by the present invention, which determines the relative height information of the pixel position corresponding to any matching envelope curve based on the matching degree between the reference envelope curve and any matching envelope curve, can be called a peak localization algorithm based on envelope correlation matching. Specific steps include:

[0083] Select a reference sequence containing n discrete data points from the reference envelope curve; assign the position number F of the first point in the reference sequence during the vertical scan process. a The envelope strength value corresponding to each sampling point is I. ai ;

[0084] The degree of matching between the reference sequence and the matching sequence is obtained by calculating the correlation coefficient ix; where the matching sequence is a segment of the matching envelope curve with the same length as the reference sequence, and the envelope strength value of each sampling point in the matching sequence is I. bi ;

[0085] The specific formula for calculating the correlation coefficient is as follows:

[0086]

[0087] in, and These are the mean intensity values ​​of all points in the reference sequence and the matched sequence, respectively.

[0088] Starting from the beginning position of any matching envelope curve, the reference sequence is extracted sequentially by sliding matching, and the correlation coefficient corresponding to each matching sequence of any matching envelope curve is calculated.

[0089] The matching sequence corresponding to the correlation coefficient of the maximum value is taken as the optimal matching sequence;

[0090] Calculate the relative height information h of the pixel position corresponding to any matching envelope curve; specifically:

[0091] h=(F a -F b )*depth (6)

[0092] Among them, F b is the index of the first point in the optimal matching sequence during the vertical scan, and depth is the vertical scan step.

[0093] Taking two points A and B on the measurement surface as an example, a vertical scan measurement is performed to obtain two sets of discrete intensity curves. The envelope curves of the intensity curves are then obtained using the Hilbert transform described earlier. The envelope curve of A is used as the reference envelope curve, and the envelope curve of B is used as the matching envelope curve.

[0094] First, select a sequence containing n discrete data points from the envelope curve of point A. This selected sequence must contain the main features of the envelope curve of point A and will be used as a reference sequence. The first point of this reference sequence is marked with its position number F during the vertical scan process. a The envelope strength corresponding to each sampling location is I. ai The segment of the envelope curve at point B that has the same length as the reference sequence is the matched sequence. The envelope strength value at each sampling point in the matched sequence is I. bi The matching degree of the envelope curve is obtained by using formula (5) to calculate the correlation coefficient ix.

[0095] Starting from the beginning of the envelope curve of the signal at point B, the reference sequence is slid along the x-axis (vertical scan position axis), and matching sequences are extracted sequentially and the correlation coefficient ix is ​​calculated. When the correlation coefficient ix reaches its maximum value, the theoretically optimal matching sequence is obtained. The relative height between points A and B can then be calculated using formula (6).

[0096] In summary, the measurement method provided by this invention reduces the number of structural illumination image projection acquisitions during axial scanning compared to traditional structural illumination microscopy, omits the step of obtaining tomographic images, and improves information utilization and system measurement efficiency.

[0097] This invention provides a peak localization algorithm based on envelope correlation matching, which improves measurement efficiency while retaining the high resolution characteristic of structured illumination measurement. Envelope matching has the characteristics of high speed and high precision, and is suitable for three-dimensional surface topography measurement.

[0098] Figure 4 This is a schematic diagram of the structure of the three-dimensional surface topography measurement system provided by the present invention, as shown below. Figure 4 As shown, the system includes:

[0099] The image capture module 401 is used to sequentially project a set of pre-set phase-shifted stripe patterns of structured light onto the vertically scanned surface of the object to be measured in order to obtain a set of captured images carrying the height information of the object.

[0100] During the vertical scanning process, the vertical scanning of the object is synchronized with the switching of the phase-shifting fringe pattern, and a phase-shifting fringe pattern corresponds to each vertical scanning position.

[0101] The intensity curve determination module 402 is used to obtain the intensity curve of any pixel position during the vertical scanning process by extracting the intensity values ​​of any pixel position in a set of captured images.

[0102] The envelope curve determination module 403 is used to obtain the envelope curve of each pixel position based on the intensity curve of each pixel position during the vertical scanning process.

[0103] The height information determination module 404 is used to take one of the envelope curves as a reference envelope curve and the other envelope curves as matching envelope curves, and perform envelope matching between the reference envelope curve and each matching envelope curve to determine the relative height information of each pixel position.

[0104] It should be noted that the three-dimensional surface topography measurement system provided in this embodiment of the invention can execute the three-dimensional surface topography measurement method described in any of the above embodiments during specific operation, which will not be elaborated in this embodiment.

[0105] Figure 5 This is a schematic diagram of the structure of the electronic device provided by the present invention, such as... Figure 5 As shown, the electronic device may include: a processor 510, a communication interface 520, a memory 530, and a communication bus 540, wherein the processor 510, the communication interface 520, and the memory 530 communicate with each other through the communication bus 540. The processor 510 can call logic instructions in the memory 530 to execute a three-dimensional surface topography measurement method. This method includes: sequentially projecting structured light with a preset set of phase-shifting fringe patterns onto the surface of a vertically scanned object to obtain a set of captured images carrying object height information; wherein, during the vertical scan, the vertical scan of the object is synchronized with the switching of the phase-shifting fringe patterns, and each vertical scan position corresponds to a phase-shifting fringe pattern; obtaining the intensity curve of any pixel position during the vertical scan by extracting the intensity value of any pixel position in the captured images; obtaining the envelope curve of each pixel position based on the intensity curve of each pixel position during the vertical scan; using one of all envelope curves as a reference envelope curve and the others as matching envelope curves, performing envelope matching between the reference envelope curve and each matching envelope curve to determine the relative height information of each corresponding pixel position.

[0106] Furthermore, the logical instructions in the aforementioned memory 530 can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, essentially, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0107] On the other hand, the present invention also provides a computer program product, the computer program product including a computer program stored on a non-transitory computer-readable storage medium, the computer program including program instructions, when the program instructions are executed by a computer, the computer is able to execute the three-dimensional surface topography measurement method provided in the above embodiments, the method including: projecting a set of preset phase-shifting fringe patterns of structured light sequentially onto the surface of a vertically scanned object to obtain a set of captured images carrying object height information; wherein, during the vertical scanning process, the vertical scanning of the object is synchronized with the switching of the phase-shifting fringe patterns, and each vertical scanning position corresponds to a phase-shifting fringe pattern; by extracting the intensity value of any pixel position in a set of captured images, the intensity curve of the any pixel position during the vertical scanning process is obtained; according to the intensity curve of each pixel position during the vertical scanning process, the envelope curve of each corresponding pixel position is obtained; one of all the envelope curves is used as a reference envelope curve, and the other envelope curves are used as matching envelope curves, and the reference envelope curve is matched with each matching envelope curve to determine the relative height information of each corresponding pixel position.

[0108] In another aspect, the present invention also provides a non-transitory computer-readable storage medium storing a computer program thereon. When executed by a processor, the computer program implements the three-dimensional surface topography measurement method provided in the above embodiments. The method includes: sequentially projecting structured light with a preset set of phase-shifting fringe patterns onto the surface of a vertically scanned object to obtain a set of captured images carrying object height information; wherein, during the vertical scanning process, the vertical scanning of the object is synchronized with the switching of the phase-shifting fringe patterns, and each vertical scanning position corresponds to a phase-shifting fringe pattern; obtaining the intensity curve of the arbitrary pixel position during the vertical scanning process by extracting the intensity value of any pixel position in the set of captured images; obtaining the envelope curve of each pixel position according to the intensity curve of each pixel position during the vertical scanning process; using one of all the envelope curves as a reference envelope curve and the other envelope curves as matching envelope curves, performing envelope matching between the reference envelope curve and each matching envelope curve to determine the relative height information of each pixel position.

[0109] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for measuring three-dimensional surface topography, characterized in that, include: Structured light with a pre-set set of phase-shifting fringe patterns is sequentially projected onto the surface of the vertically scanned object to obtain a set of captured images carrying the object's height information. During the vertical scan, the vertical scan of the object is synchronized with the switching of the phase-shifting fringe patterns, and each vertical scan position corresponds to a phase-shifting fringe pattern. By extracting the intensity values ​​of any pixel location in a set of captured images, the intensity curve of that pixel location during the vertical scanning process is obtained; Based on the intensity curve of each pixel position during the vertical scanning process, obtain the envelope curve of each pixel position. One of the envelope curves is used as the reference envelope curve, and the other envelope curves are used as matching envelope curves. The reference envelope curve is matched with each matching envelope curve to determine the relative height information of each pixel position. Specifically, based on the matching degree between the reference envelope curve and any matching envelope curve, the relative height information of the pixel position corresponding to any matching envelope curve is determined, including: Select a segment from the reference envelope curve that contains n A reference sequence of discrete data; the position number of the first point in the reference sequence during the vertical scan is... The envelope strength value corresponding to each sampling point is ; By calculating the correlation coefficient ix The matching degree between the reference sequence and the matching sequence is obtained; where the matching sequence is a segment of the matching envelope curve with the same length as the reference sequence, and the envelope strength value of each sampling point in the matching sequence is... ; The specific formula for calculating the correlation coefficient is as follows: ； in, and These are the mean intensity values ​​of all points in the reference sequence and the matched sequence, respectively. Starting from the beginning position of any matching envelope curve, the reference sequence is extracted sequentially by sliding matching, and the correlation coefficient corresponding to each matching sequence of any matching envelope curve is calculated. The matching sequence corresponding to the correlation coefficient of the maximum value is taken as the optimal matching sequence; Calculate the relative height information of the pixel position corresponding to any matching envelope curve; specifically: ； in, This is the index of the first point in the optimal matching sequence during the vertical scan. This is the vertical scan step size.

2. The three-dimensional surface topography measurement method according to claim 1, characterized in that, Based on the intensity curve of any pixel location during the vertical scanning process, the envelope curve of each pixel location includes: The envelope curve of the intensity curve can be obtained using the Hilbert transform or Fourier transform method.

3. The three-dimensional surface topography measurement method according to claim 1, characterized in that, The phase-shifting fringe pattern is a four-step phase-shifting sinusoidal fringe, with a phase shift between each adjacent phase-shifting fringe pattern.

4. The three-dimensional surface topography measurement method according to claim 3, characterized in that, When using an image acquisition device for vertical scanning, the stripe width is set such that the difference between the stripe width and the pixel size of the image acquisition device is less than a preset threshold.

5. The three-dimensional surface topography measurement method according to claim 1, characterized in that, The intensity curve represents the function of how the intensity value at a pixel location changes with the vertical scan position z; ； in, Indicates the intensity value at the pixel location. It is the background light intensity. It is the contrast at the vertical scan position z. At pixel position The constant at the point is P, which is the phase shift number.

6. A three-dimensional surface topography measurement system for implementing the three-dimensional surface topography measurement method as described in any one of claims 1 to 5, characterized in that, include: The image capture module is used to sequentially project a set of pre-set phase-shifting fringe patterns onto the surface of the vertically scanned object to obtain a set of captured images carrying the object's height information. During the vertical scan, the vertical scan of the object is synchronized with the switching of the phase-shifting fringe patterns, and each vertical scan position corresponds to a phase-shifting fringe pattern. The intensity curve determination module is used to obtain the intensity curve of any pixel location during the vertical scanning process by extracting the intensity values ​​of any pixel location in a set of captured images. The envelope curve determination module is used to obtain the envelope curve of each pixel position based on the intensity curve of each pixel position during the vertical scanning process. The height information determination module is used to take one of the envelope curves as a reference envelope curve and the other envelope curves as matching envelope curves, and to perform envelope matching between the reference envelope curve and each matching envelope curve to determine the relative height information of each pixel position.

7. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the three-dimensional surface topography measurement method as described in any one of claims 1 to 5.

8. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the three-dimensional surface topography measurement method as described in any one of claims 1 to 5.

9. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the three-dimensional surface topography measurement method as described in any one of claims 1 to 5.

Images