Optical interferometric three-dimensional topography measurement method and system based on multi-frame interferogram registration

Abstract

The application belongs to the technical field of optical image processing, and particularly relates to an optical interference three-dimensional topography measurement method and system based on multi-frame interference image registration. A linear displacement stage is moved, and interference images of a sample on the linear displacement stage are collected at a preset sampling interval to obtain an original interference image sequence; actual sampling interval errors between adjacent frames are calculated to obtain an error accumulation amount of each frame; spatial coordinate compensation is performed on horizontal coordinates of each frame to obtain modified discrete horizontal coordinates; based on the discrete horizontal coordinates, a linear interpolation method is used to rearrange the original interference image sequence to obtain a registered interference image sequence; pixel points are extracted and recombined to obtain interference signals; and phase demodulation is performed on the interference signals to obtain a three-dimensional surface topography of the sample. The application uses a sampling error accumulation amount quantization and linear interpolation method to reconstruct the interference image sequence, realizes sub-pixel level pattern registration, and realizes high-precision and large-field three-dimensional topography measurement.

Description

Technical Field

[0001] This invention belongs to the field of optical image processing technology, specifically relating to an optical interferometric three-dimensional topography measurement method and system based on multi-frame interferometric image registration. Background Technology

[0002] With the development of microsystems technology, the demand for measurements at the decimeter scale, micrometer-level lateral resolution, and nanometer-level vector resolution is becoming increasingly prominent, and measurement capability is increasingly becoming a bottleneck restricting the development of modern equipment manufacturing. High-precision measurement has wide applications in many fields such as aerospace, IC manufacturing, national defense, biomedicine, MEMS manufacturing, and information storage. The characteristic parameters such as the size and morphology of microstructures are directly related to the functionality, stability, and reliability of components, requiring comprehensive assurance from multiple aspects such as manufacturing processes, manufacturing quality, and performance testing. High-precision measurement of microstructure dimensions is an indispensable and important technology for ensuring the functional quality of microstructure surfaces.

[0003] Optical interferometry is one of the most commonly used optical surface measurement methods for 3D surface reconstruction of microstructures in modern manufacturing processes. Optical interferometry methods include laser interferometry, white light interferometry, transverse shearing interferometry, phase-shifting interferometry, confocal interferometry, Fourier interferometry, polarization interferometry, spatial frequency interferometry, and structured light projection interferometry. Primarily based on the principle of light interference, it obtains the microscopic morphology of an object's surface by analyzing interference fringes or phase information. Optical interferometry is widely used in precision manufacturing, semiconductor testing, and biomedicine due to its ultra-high precision, non-contact measurement, and dynamic monitoring potential. However, its limited field of view restricts its application in industrial manufacturing process monitoring. Therefore, image stitching methods have emerged as one solution because they can achieve a larger field of view. However, image stitching methods involve some key issues, such as pixel misalignment and unpatterned intersection areas.

[0004] To address the aforementioned image stitching problem, traditional optical scanning interferometry is inefficient and cannot meet the measurement needs of large-area samples. Therefore, a transverse scanning interferometry technique was proposed. This technique measures the interference signal by the off-axis motion of a transversely moving linear platform. The sample is placed on the linear platform to obtain the morphology of a larger area without the need for image stitching.

[0005] Although transverse scanning interferometry is crucial for large field-of-view optical inspection, traditional transverse scanning interferometry is highly sensitive to environmental vibrations. The straightness, levelness, and velocity uniformity of the linear translation stage can severely impact the stability of the sampling interval in the interferometric image, even causing tilting of the interference fringes and deformation of the interference signal, leading to reduced accuracy in the measurement of the three-dimensional topography of microstructures. The non-uniformity of the linear translation stage velocity is a fundamental problem limiting measurement accuracy. This leads to sub-pixel-level pattern shifts after pixel reordering due to non-uniform sampling intervals, gray-scale anomalies in the scanning direction, and nonlinear distortion in phase calculations due to accumulated time sampling errors, resulting in topography errors exceeding thresholds in nanoscale measurement scenarios. Existing solutions rely on high-precision translation stages (such as closed-loop control), but these cannot eliminate disturbances such as mechanical vibration and motor response hysteresis, and significantly increase hardware costs. Summary of the Invention

[0006] The purpose of this invention is to provide an optical interferometric three-dimensional topography measurement method and system based on multi-frame image registration. The method uses time sampling error accumulation quantization and linear interpolation to reconstruct the interferometric image sequence, achieving sub-pixel-level pattern registration, thereby realizing high-precision, large-field-of-view three-dimensional topography measurement.

[0007] To achieve the above objectives, according to a first aspect of the present invention, an optical interferometric three-dimensional topography measurement method based on multi-frame interferometric image registration is provided, comprising the following steps:

[0008] S1. Move the linear displacement stage and acquire interference images of the sample on the linear displacement stage at preset sampling intervals to obtain the original interference image sequence;

[0009] S2. Calculate the actual sampling interval between adjacent frames of the original interferometric image sequence, and then obtain the sampling interval error accumulation of each frame based on the actual sampling interval.

[0010] S3. Based on the accumulated sampling interval error, spatial coordinate compensation is performed on the horizontal coordinates of each frame to obtain the corrected discrete horizontal coordinates.

[0011] S4. Based on the corrected discrete horizontal coordinates, the original interferometric image sequence is rearranged using linear interpolation to obtain the registered interferometric image sequence.

[0012] S5. Extract pixels from the registered interferometric image sequence and reassemble them to obtain the interferometric signal;

[0013] S6. Perform phase calculation on the interference signal to obtain the three-dimensional surface morphology of the sample.

[0014] Furthermore, in step S1, the preset sampling interval and the moving speed of the linear displacement stage satisfy the following relationship:

[0015] Δu = VM / FS

[0016] Where Δu is the preset sampling interval, representing the number of pixels between two adjacent interferometric images, in units of pixels; V is the moving speed of the linear displacement stage, in units of μm / s; F is the camera frame rate, in units of frames per second; S is the pixel size of the camera, in units of μm; and M is the magnification of the imaging system.

[0017] Furthermore, the preset sampling interval is 1-5 pixels; the moving speed of the linear displacement stage is 0.1-2 mm / s.

[0018] Furthermore, step S2 specifically includes:

[0019] S201. Select the first frame in the original interferometric image sequence as the reference frame I0, and the remaining frames as the frames to be registered I0. k ;

[0020] S202, Extract reference frame I0 and frame to be registered I0 k The key feature point set is used to eliminate mismatched point pairs through random sampling consistency, retain the matching point set, and calculate the mean displacement vector based on the matching point set to obtain the actual sampling interval between two adjacent interferometric images.

[0021] S203. Calculate the accumulated sampling interval error c of the i-th frame of the interferometric image according to the following formula. i :

[0022]

[0023] Among them, u j The actual sampling interval between frame j and frame j-1 is given by u1, where u1 represents the sampling interval between frame 1 and frame 0, and u1 is a preset sampling interval. j+1 is the actual sampling interval between frame j+1 and frame j, and n represents the total number of frames in the original interferometric image sequence.

[0024] Furthermore, in step S3, the corrected discrete horizontal coordinate of the i-th frame of the interferometric image is x. i =Nx-c i i = 1, 2, ..., n;

[0025] Nx is the total number of pixels in the horizontal direction of the original interferometric image, and c i denoted as the accumulated sampling interval error of the i-th frame, and n represents the total number of frames in the original interferometric image sequence.

[0026] Furthermore, in step S4, the registered interferometric image sequence consists of linearly interpolated interferometric images, and the i-th frame interpolated interferogram is represented as:

[0027]

[0028] I represents the light intensity of the interpolated interferogram in the i-th frame. i (x,y) represents the light intensity of a pixel in the original interferogram of the i-th frame.

[0029] Furthermore, step S5 specifically includes the following steps:

[0030] S501. In the scanning direction, select a set of fixed spatial position pixels that completely pass through the interference fringe area. Extract the gray value of each pixel in all frames from the frame sequence axis to form a time-intensity curve. With a preset sampling interval as the step size, arrange the pixel intensity of the same spatial position in time order to generate a set of reconstructed images so that each reconstructed image reflects the evolution of interference fringes at the same physical position.

[0031] S502. After pixel stitching, the intensity sequence of each reconstructed image is the interference signal, and the intensity of the interference signal can be expressed as:

[0032]

[0033] Among them, I B Let λ represent the background light intensity, γ represent the fringe contrast, g(z) represent the envelope equation of the interference signal, λ0 represent the center wavelength, z represent the optical path difference introduced by movement along the measurement direction, and z0 represent the perpendicular position where the reference beam and the target beam have the same length. The initial phase relative to the reference plane.

[0034] Furthermore, the methods for acquiring the interference images include: laser interference, white light interference, transverse shearing interference, phase-shifting interference, confocal interference, Fourier interference, polarization interference, spatial frequency interference, or structured light projection interference.

[0035] According to a second aspect of the present invention, an optical interferometric three-dimensional topography measurement system based on multi-frame interferometric image registration is provided, comprising:

[0036] The interferometric image acquisition unit is used to move the linear displacement stage and acquire the interferometric images of the sample at preset sampling intervals to obtain the original interferometric image sequence;

[0037] The image sampling compensation unit is used to calculate the accumulated sampling interval error of each frame, and to perform spatial coordinate compensation on the horizontal coordinate of each frame based on the accumulated sampling interval error to obtain the corrected discrete horizontal coordinate.

[0038] The interferometric image rearrangement unit is used to rearrange the original interferometric image sequence based on the corrected discrete horizontal coordinates using a linear interpolation method to obtain the registered interferometric image sequence.

[0039] The interference signal extraction and reconstruction unit is used to extract pixels from the registered interference image sequence and reconstruct them to obtain the interference signal; the phase of the interference signal is calculated to obtain the three-dimensional surface morphology of the sample.

[0040] Furthermore, the interferometric image acquisition unit includes an illumination optical path system, an interferometric optical path system, a linear displacement stage, and a camera;

[0041] The interference optical path system includes a beam splitter, objective lens one, a reflecting mirror, and objective lens two. The light emitted by the illumination optical path system is split into two beams after passing through the beam splitter. One beam is transformed into a plane wave after passing through objective lens one and illuminates the reflecting mirror to form a reference light. The other beam is transformed into a plane wave after passing through objective lens two and illuminates the sample to be measured placed on a linear displacement stage to form an object light. The object light returns and passes through objective lens two and the beam splitter, and is then converged by a tube lens onto an industrial camera to complete the imaging.

[0042] Preferably, the system includes a memory and a processor. The memory stores a computer program that implements the functions of the interferometric image acquisition unit, the image sampling compensation unit, the interferometric image rearrangement unit, and the interferometric signal extraction and reconstruction unit. The processor executes the computer program.

[0043] According to a third aspect of the present invention, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the optical interferometric three-dimensional topography measurement method based on multi-frame interferometric image registration as described above.

[0044] In summary, compared with the prior art, the above-described technical solutions conceived by this invention mainly possess the following technical advantages:

[0045] 1. The present invention provides an optical interferometric three-dimensional topography measurement method based on multi-frame image registration. By accurately calculating the sampling interval between adjacent frame images, obtaining the corrected discrete horizontal coordinates, and rearranging the interferometric images, the scanned interferometric images are aligned to reduce the influence of the linear displacement stage straightness and velocity uniformity, and to obtain the light intensity signal of each point after stitching more accurately. This helps to achieve topography reconstruction with a large field of view, high precision, and low hardware dependence.

[0046] 2. This invention uses a time error accumulation quantization model to break through the limitations of traditional single-frame registration, compensates for the horizontal position, eliminates sub-pixel level deviations in the scanning direction, and uses linear interpolation to reorder the interference image based on the compensation coordinates, thus ensuring the alignment accuracy of the scheme.

[0047] 3. Unlike traditional optical interferometry algorithms, linear platform speeds are typically on the order of μm / s, requiring a high-precision translation stage. This significantly increases hardware costs to handle disturbances such as mechanical vibration and motor response hysteresis. The method provided in this invention utilizes a high-speed camera, achieving linear translation stage speeds on the order of mm / s. This satisfies the requirements of high-speed moving samples, enabling high-precision, large-field-of-view three-dimensional topography measurement while effectively improving cost-effectiveness.

[0048] 4. The image registration method and system of this invention are widely applicable to various types of optical interferometry techniques, including but not limited to: registration and reconstruction of multi-frame interferometric images acquired by interferometric systems such as laser interferometry, white light interferometry, transverse shearing interferometry, phase-shifting interferometry, confocal interferometry, Fourier interferometry, polarization interferometry, spatial frequency interferometry, and structured light projection interferometry. Through a unified time error accumulation quantization model and interpolation reconstruction strategy, the image registration accuracy and 3D reconstruction quality of the aforementioned interferometric systems under dynamic measurement or unstable conditions can be significantly improved. Attached Figure Description

[0049] Figure 1 This is a flowchart illustrating a three-dimensional optical interferometric topography measurement method based on multi-frame image registration, as described in an embodiment of the present invention.

[0050] Figure 2 This is a structural framework diagram of an optical interferometric three-dimensional topography measurement system based on multi-frame image registration, as described in an embodiment of the present invention.

[0051] Figure 3 This is a schematic diagram of the optical path structure of the optical interference system used in the embodiments of the present invention.

[0052] Figure 4 This is a schematic diagram of the misalignment of the interference image of the sample provided in an embodiment of the present invention.

[0053] Figure 5 This is a schematic diagram of the contour curve of the sample's three-dimensional shape recovery without image registration algorithm in a traditional optical interferometry embodiment of the present invention.

[0054] Figure 6 This is a schematic diagram of the three-dimensional shape contour curve of a sample after image registration and three-dimensional reconstruction in an embodiment of the present invention. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0056] This invention provides a method for measuring three-dimensional optical interferometric topography based on multi-frame interferometric image registration, comprising the following steps:

[0057] S1. Move the linear displacement stage and acquire interference images of the sample on the linear displacement stage at preset sampling intervals to obtain the original interference image sequence;

[0058] S2. Calculate the actual sampling interval between adjacent frames of the original interferometric image sequence, and then obtain the sampling interval error accumulation of each frame based on the actual sampling interval.

[0059] S3. Based on the accumulated sampling interval error, spatial coordinate compensation is performed on the horizontal coordinates of each frame to obtain the corrected discrete horizontal coordinates.

[0060] S4. Based on the corrected discrete horizontal coordinates, the original interferometric image sequence is rearranged using linear interpolation to obtain the registered interferometric image sequence.

[0061] S5. Extract pixels from the registered interferometric image sequence and reassemble them to obtain the interferometric signal;

[0062] S6. Perform phase calculation on the interference signal to obtain the three-dimensional surface morphology of the sample.

[0063] This invention aligns the scanned interferometric images by accurately calculating the actual sampling interval between adjacent frames, obtaining the corrected discrete horizontal coordinates, and rearranging the interferometric images. This reduces the influence of the linear displacement stage's straightness and velocity uniformity, thereby obtaining the light intensity signals of each point after stitching more accurately. This improves the image registration accuracy and 3D reconstruction quality under dynamic measurement or unstable conditions.

[0064] Example

[0065] like Figure 1 As shown, an optical interferometric three-dimensional topography measurement method based on multi-frame interferometric image registration includes the following steps:

[0066] Step S1: Move the linear displacement stage at a preset moving speed to acquire a series of scanned interference images. The sampling interval between adjacent interference images is a set value Δu, where Δu is an integer number of pixels.

[0067] Preferably, in step S1, the method for acquiring the interferogram of the area to be tested is to acquire the interferogram of the area to be tested in real time based on the optical path system, or to retrieve it from a storage medium storing the interferogram of the area to be tested acquired based on the optical path system.

[0068] More specifically, interferometric image acquisition refers to acquiring interferograms of the sample under test. These interferograms include interferograms of the test region and a reference region. The reference region is the interferogram acquired without the sample in the optical path system, or the interferogram of a relatively clean, patternless area within the sample (i.e., the background interferogram). The test region is the interferogram acquired with the sample in the optical path system. Acquiring the interferogram of the reference region is to eliminate aberrations in the optical path system, thereby enhancing the contrast of the interferogram of the test region and making the image clearer. Interferogram acquisition includes all methods applicable to interferometry, including but not limited to laser interferometry, white light interferometry, transverse shearing interferometry, phase-shifting interferometry, confocal interferometry, Fourier interferometry, polarization interferometry, spatial frequency interferometry, and structured light projection interferometry.

[0069] Specifically, based on the relationship between the camera frame rate and the scanning speed of the linear translation stage, the number of pixels moved between two frames can be controlled by setting the speed of the linear translation stage. The number of pixels moved can be expressed as:

[0070] Δu = VM / FS

[0071] Wherein, Δu is the number of pixels between two frames, preferably 1-5 pixels; V is the linear displacement stage moving speed, preferably 0.1-2 mm / s; F is the camera frame rate (frames per second, fps), preferably 800-1500 fps; S is the camera pixel size, preferably 1-10 μm; M is the magnification of the imaging system (an optical imaging system composed of objective lenses, tube lenses and other optical devices), preferably 20-100 times.

[0072] Step S2: Perform image registration on the original interferometric image sequence and calculate the actual sampling interval between adjacent frames. Using the first frame as a reference, calculate the accumulated temporal sampling error of the i-th frame;

[0073] More specifically, the cumulative deviation quantification includes the following steps:

[0074] Step S201: Select the first frame from the multi-frame image as the reference frame I0, and the remaining frames as the frames to be registered I0. k ;

[0075] Step S202, for reference frame I0 and frame I to be registered k Extract key feature point sets, eliminate mismatched point pairs through random sampling consistency, retain robust matching point sets, calculate the mean displacement vector based on the matching point sets, and obtain the actual sampling interval u between two adjacent frames. i ;

[0076] Step S203, calculate the accumulated temporal sampling error of the i-th frame:

[0077] Preferably, the accumulated sampling time error of the i-th frame can be obtained by integrating the difference between the displacement difference between images and the theoretical interval Δu, which reflects the global position offset caused by the non-uniform speed of platform scanning.

[0078]

[0079] Among them, u j The actual sampling interval between frame j and frame j-1 is given by u1, where u1 represents the sampling interval between frame 1 and frame 0, and u1 is a preset sampling interval. j+1 is the actual sampling interval between frame j+1 and frame j, and n represents the total number of frames in the original interferometric image sequence.

[0080] Step S3: Perform spatial coordinate compensation, correct the horizontal coordinates of the i-th frame according to the sampling error, and obtain the corrected discrete horizontal coordinates.

[0081] More specifically, the accumulated time sampling error obtained from S2 is used for spatial coordinate compensation, which is then used to generate a horizontal interferogram to obtain the corrected discrete horizontal position. The compensated horizontal coordinates of the i-th frame can be expressed as:

[0082] x i =Nx-c i i = 1, 2, ..., n

[0083] Where, x i Let Nx be the horizontal coordinate value of the i-th frame interferogram after correction, i.e., the coordinate value along the direction of linear displacement stage movement (scanning direction), and let c be the total number of pixels in the horizontal direction of the original image. i Let c be the accumulated temporal sampling error of the i-th frame, and n represent the total number of frames in the original interferometric image sequence. i =0, which means that the horizontal coordinate value of the i-th frame interferogram has no deviation. i If the coordinates are not equal to Nx, then coordinate compensation is required.

[0084] Step S4: The interferometric image sequence is rearranged based on the corrected discrete horizontal coordinate compensation result using a linear interpolation method to obtain a registered multi-frame interferometric image sequence.

[0085] More specifically, the linear interpolation (LI) method is used to rearrange the interferometric image sequence based on the corrected discrete horizontal coordinate compensation results, resulting in a registered multi-frame interferometric image sequence. The interpolated interferogram of the i-th frame can be represented as:

[0086]

[0087] This represents the interpolated interferogram of the i-th frame, where (x, y) represents the coordinates of a pixel, x is the horizontal coordinate (scanning direction), and y is the coordinate of the interference fringe direction. i (x,y) represents the light intensity of the i-th frame of the original interferogram, and n represents the total number of frames in the original interferogram sequence.

[0088] Step S5: Process the registered image, extract the pixels with the same scanning interval Δu after registration and reassemble them. Ensure that the pattern is consistent in each reassembled image to obtain the interference signal.

[0089] More specifically, it includes the following steps:

[0090] Step S501: In the scanning direction, select a set of fixed spatial position pixels that completely pass through the interference fringe region. Extract the gray value of each pixel in all frames using the frame sequence axis to form a time-intensity curve. With the scanning interval (Δu) as the step size, arrange the pixel intensities of the same spatial position in chronological order to generate a set of reconstructed images (i.e., each reconstructed image corresponds to the intensity sequence of a fixed spatial position at all time points), ensuring that each reconstructed image reflects the evolution of interference fringes at the same physical position.

[0091] In step S502, after pixel stitching, the intensity sequence of each reconstructed image is the interference signal, which is physically a function of the sample height change. The intensity of the interference signal can be expressed as:

[0092]

[0093] Where I B Let λ represent the background light intensity, γ represent the fringe contrast, g(z) represent the envelope equation of the interference signal, λ0 represent the center wavelength, z represent the optical path difference introduced by movement along the measurement direction, and z0 represent the perpendicular position where the reference beam and the target beam have the same length. The initial phase relative to the reference plane.

[0094] Step S6: Perform phase calculation on the signal to generate a high-precision three-dimensional surface morphology.

[0095] To better implement the optical interferometric three-dimensional topography measurement method based on multi-frame image registration in the embodiments of the present invention, based on the optical interferometric three-dimensional topography measurement method based on multi-frame image registration, correspondingly, as follows: Figure 2 As shown, the present invention also provides a measurement system for optical interference three-dimensional topography based on multi-frame image registration, including an interference image acquisition unit 1, an image sampling compensation unit 2, an interference image rearrangement unit 3, and an interference signal extraction and reconstruction unit 4.

[0096] In another embodiment, to verify the feasibility of the method for measuring three-dimensional topography using optical interferometry based on multi-frame image registration, a constructed optical interferometry system was used to measure a microscopic sample. The optical path of the optical interferometry system is as follows: Figure 3 As shown, the optical interference system includes: an LED light source 1, a first lens 2, a pinhole filter 3, a second lens 4, a field stop 5, a beam splitter 6, a first objective lens 7, a reflecting mirror 8, a second objective lens 9, a sample 10, a linear displacement stage 11, a tube lens 12, and an industrial camera 13. The LED light source 1, the first lens 2, the pinhole filter 3, the second lens 4, and the field stop 5 constitute the Kohler illumination optical path system 100, and the beam splitter 6, the first objective lens 7, the reflecting mirror 8, and the second objective lens 9 constitute the interference optical path system 200.

[0097] The working principle of the optical interference system is as follows: When the light beam emitted by the LED light source 1 passes sequentially through the first lens 2, the pinhole filter 3, the second lens 4, and the field stop 5, it forms collimated and converged illumination light. After passing through the beam splitter 6, it is split into two beams. One beam passes through the first objective lens 7 and is transformed into a plane wave, which illuminates the reflecting mirror 8 to form the reference light. The other beam passes through the second objective lens 9 and is transformed into a plane wave, which illuminates the sample 10 to be measured placed on the linear displacement stage 11 to form the object light. The object light returns and passes through the second objective lens 9 and the beam splitter 6, and is converged by the tube lens 12 to the industrial camera 13 to complete the imaging. The reference light is reflected by the reflecting mirror 8, passes through the second objective lens 7, the beam splitter 6, and the tube lens 12, and enters the industrial camera 13 in parallel, interfering with the object light. The interference intensity reaches its maximum when the optical path difference between the object light and the reference light is equal.

[0098] The sample to be tested 10 can be driven by the linear displacement stage 11 to select the measurement position.

[0099] Specifically, a series of scanned interferometric images are generated, with a set interval of 3 pixels between the images, a pixel size of 9μm, a light source wavelength of 455nm, and a system magnification of 27.06. An industrial high-speed camera is used for image capture, with its frame rate set to 1000fps, thereby obtaining a scanning speed of 0.9978mm / s for the linear displacement stage.

[0100] A circular array, self-etched on a gallium arsenide (GaAs) wafer, was selected as the substrate. The array had a spacing of 62 μm and a diameter of 50 μm. Before image registration, the interferometric image showed a significant positional shift (e.g., ...). Figure 4 (As shown). Figure 5 The image shows the sample contour curve obtained without image matching processing. Due to the stage speed error, the spatial alignment of the scanning interferogram was inaccurate during the rearrangement process. The unregistered 3D contour exhibited abrupt changes in the edge region, affecting the accuracy of the topography reconstruction. In detail, Figure a shows the reconstructed 3D topography, and Figure b shows the edge height curve of the profile contour taken from the dashed line. Figure 6 The contour curves of the etched array obtained by processing the proposed multi-frame image matching method are shown, significantly reducing edge errors. In detail, Figure a shows the reconstructed 3D topography, and Figure b shows the edge height curves of the cross-sectional contour taken from the dashed lines. Figure 5 As shown, the 3D contours obtained by traditional unregistered methods exhibit significant edge undulations, while... Figure 6 As shown, after registration, the edge curves are continuous and smooth, verifying the effectiveness of the registration method of this invention in improving topographic accuracy. This system enables continuous, non-stop, rapid scanning and higher-precision 3D topographic measurement, while effectively addressing hardware issues related to non-uniform sampling intervals and reducing hardware costs.

[0101] In some embodiments of the present invention, when the processor executes a multi-frame image-based optical interferometric three-dimensional topography measurement program stored in memory, the following steps can be implemented:

[0102] Acquire a series of interference images of the scanned sample;

[0103] Image registration is performed on the original interferometric image sequence, and the actual sampling interval between adjacent frames is calculated.

[0104] Spatial coordinate compensation is performed to obtain the corrected discrete horizontal coordinates;

[0105] The interferometric image sequence is rearranged based on the corrected discrete horizontal coordinate compensation results using a linear interpolation method.

[0106] Interference signals are obtained by recombining pixels with the same scanning interval after registration.

[0107] Phase decoding is performed on the signal to generate a high-precision three-dimensional surface topography.

[0108] It should be understood that when the processor executes the optical interferometric three-dimensional topography measurement program for multiple frames of images in memory, in addition to the functions mentioned above, it can also perform other functions, such as necessary data preprocessing and postprocessing.

[0109] Accordingly, this application also provides a computer-readable storage medium for storing computer-readable programs or instructions. When the programs or instructions are executed by a processor, they can realize the optical interferometric three-dimensional topography measurement method based on multi-frame images provided in the above embodiments.

[0110] A three-dimensional optical interferometric topography measurement system based on multi-frame images is disclosed. The system includes a memory and a processor. The memory stores a computer program, and the processor executes the computer program to perform the three-dimensional optical interferometric topography measurement method based on multi-frame images as described above.

[0111] In summary, this invention provides a method and system for optical interferometric three-dimensional topography measurement based on multi-frame image registration. By acquiring multiple frames of images, reconstructing pixel images, calculating the cumulative amount of time sampling error, compensating for spatial coordinates, and reconstructing the interferometric image sequence, it effectively solves the dependence on the small field of view and high environmental requirements of traditional optical interferometric measurement and lateral scanning interferometry. It achieves efficient and accurate high-precision, large-field-of-view three-dimensional topography measurement while reducing hardware costs.

[0112] The above description is only a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All interferometric measurement methods that use multiple interferometric images for registration, including but not limited to laser interferometry, white light interferometry, transverse shearing interferometry, phase shifting interferometry, confocal interferometry, Fourier interferometry, polarization interferometry, spatial frequency interferometry and structured light projection interferometry, and other interferometric imaging methods involving image reordering and three-dimensional morphology extraction, should be included within the scope of protection of the present invention.

[0113] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for measuring three-dimensional optical interferometric topography based on multi-frame interferometric image registration, characterized in that, Includes the following steps: S1. Move the linear displacement stage and acquire interference images of the sample on the linear displacement stage at preset sampling intervals to obtain the original interference image sequence; S2. Calculate the actual sampling interval between adjacent frames of the original interferometric image sequence, and then obtain the sampling interval error accumulation of each frame based on the actual sampling interval. S3. Based on the accumulated sampling interval error, spatial coordinate compensation is performed on the horizontal coordinates of each frame to obtain the corrected discrete horizontal coordinates. S4. Based on the corrected discrete horizontal coordinates, the original interferometric image sequence is rearranged using linear interpolation to obtain the registered interferometric image sequence. S5. Extract pixels from the registered interferometric image sequence and reconstruct them to obtain the interferometric signal; step S5 specifically includes the following steps: S501. In the scanning direction, select a set of fixed spatial position pixels that completely pass through the interference fringe area. The frame sequence axis extracts the gray value of each pixel in all frames with a preset sampling interval as the step size to form a time-intensity curve. The pixel intensity of the same spatial position is arranged in time order to generate a set of reconstructed images so that each reconstructed image reflects the evolution of interference fringes at the same physical position. S502. After pixel stitching, the intensity sequence of each reconstructed image is the interference signal, and the intensity of the interference signal can be expressed as: in, Indicates background light intensity. Indicates stripe contrast. The equation representing the envelope of the interference signal. The wavelength is represented by , and z represents the optical path difference introduced by movement along the measurement direction. This indicates a perpendicular position where the reference beam and the target beam have the same length at the starting position. The initial phase relative to the reference plane; S6. Perform phase calculation on the interference signal to obtain the three-dimensional surface morphology of the sample.

2. The optical interferometric three-dimensional topography measurement method based on multi-frame interferometric image registration according to claim 1, characterized in that, In step S1, the preset sampling interval and the moving speed of the linear displacement stage satisfy the following relationship: in, The preset sampling interval represents the number of pixels between two adjacent frames of the interference image, in units of pixels; V is the moving speed of the linear displacement stage, in units of μm / s; F is the camera frame rate, in units of frames per second; S is the pixel size of the camera, in units of μm; and M is the magnification of the interference image.

3. The optical interferometric three-dimensional topography measurement method based on multi-frame interferometric image registration according to claim 2, characterized in that, The preset sampling interval is 1-5 pixels; the moving speed of the linear displacement stage is 0.1-2 mm / s.

4. The optical interferometric three-dimensional topography measurement method based on multi-frame interferometric image registration according to any one of claims 1-3, characterized in that, Step S2 specifically includes: S201. Select the first frame in the original interferometric image sequence as the reference frame. The remaining frames are used as frames to be registered. ; S202, Extract the reference frame and the frame to be registered The key feature point set is used to eliminate mismatched point pairs through random sampling consistency, retain the matching point set, and calculate the mean displacement vector based on the matching point set to obtain the actual sampling interval between two adjacent interferometric images. S203. Calculate the accumulated sampling interval error c of the i-th frame of the interferometric image according to the following formula. i : in, The actual sampling interval between frame j and frame j-1. is the actual sampling interval between frame j+1 and frame j, and n represents the total number of frames in the original interferometric image sequence.

5. The optical interferometric three-dimensional topography measurement method based on multi-frame interferometric image registration according to claim 4, characterized in that, In step S3, the corrected discrete horizontal coordinates of the i-th frame of the interferometric image are: ; Nx is the total number of pixels in the horizontal direction of the original interferometric image. denoted as the accumulated sampling interval error of the i-th frame, and n represents the total number of frames in the original interferometric image sequence.

6. The optical interferometric three-dimensional topography measurement method based on multi-frame interferometric image registration according to claim 5, characterized in that, In step S4, the registered interferometric image sequence consists of linearly interpolated interferometric images, and the i-th frame interpolated interferogram is represented as: This represents the light intensity of the interpolated interferogram in the i-th frame. This represents the light intensity of a pixel in the original interferogram of the i-th frame.

7. The optical interferometric three-dimensional topography measurement method based on multi-frame interferometric image registration according to claim 1, characterized in that, The methods for acquiring the interference images include: laser interference, white light interference, transverse shearing interference, phase-shifting interference, confocal interference, Fourier interference, polarization interference, spatial frequency interference, or structured light projection interference.

8. An optical interferometric three-dimensional topography measurement system based on multi-frame interferometric image registration, employing the method described in any one of claims 1-7, characterized in that, include: The interferometric image acquisition unit is used to move the linear displacement stage and acquire the interferometric images of the sample at preset sampling intervals to obtain the original interferometric image sequence; The image sampling compensation unit is used to calculate the accumulated sampling interval error of each frame, and to perform spatial coordinate compensation on the horizontal coordinate of each frame based on the accumulated sampling interval error to obtain the corrected discrete horizontal coordinate. The interferometric image rearrangement unit is used to rearrange the original interferometric image sequence based on the corrected discrete horizontal coordinates using a linear interpolation method to obtain the registered interferometric image sequence. The interference signal extraction and reconstruction unit is used to extract pixels from the registered interference image sequence and reconstruct them to obtain the interference signal; the phase of the interference signal is calculated to obtain the three-dimensional surface morphology of the sample.

9. The optical interferometric three-dimensional topography measurement system based on multi-frame interferometric image registration according to claim 8, characterized in that, The interferometric image acquisition unit includes an illumination optical path system, an interferometric optical path system, a linear displacement stage, and a camera; The interference optical path system includes a beam splitter, objective lens one, a reflecting mirror, and objective lens two. The light emitted by the illumination optical path system is split into two beams after passing through the beam splitter. One beam is transformed into a plane wave after passing through objective lens one and illuminates the reflecting mirror to form a reference light. The other beam is transformed into a plane wave after passing through objective lens two and illuminates the sample to be measured placed on a linear displacement stage to form an object light. The object light returns and passes through objective lens two and the beam splitter, and is then converged by a tube lens onto an industrial camera to complete the imaging.

10. A computer-readable storage medium, characterized in that, It stores a computer program, which, when executed by a processor, implements the optical interferometric three-dimensional topography measurement method based on multi-frame interferometric image registration as described in any one of claims 1-7.

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