A blind hole profile detection method and system

Abstract

The application discloses a blind hole profile detection method and system, which comprises the following steps: in the process of laser processing of a blind hole, the blind hole is scanned in real time by an optical coherence imaging system to obtain interference light intensity data corresponding to the current blind hole profile; a point cloud graph of the blind hole profile is constructed based on the interference light intensity data; a blind hole profile model is generated according to the point cloud graph of the blind hole profile; and blind hole profile parameters are obtained based on the blind hole profile model. In the process of preparing the blind hole, the blind hole is scanned in real time by the optical coherence imaging system, the blind hole profile model is generated through the point cloud, and the corresponding blind hole profile parameters are obtained through the blind hole profile model, so that the stability and consistency of the subsequent blind hole processing quality are ensured.

Description

Technical Field

[0001] This invention relates to the field of laser processing technology, and in particular to a method and system for detecting the contour of blind holes. Background Technology

[0002] Existing technologies have developed technical solutions for preparing blind holes based on laser equipment. However, due to complex physical processes such as heat accumulation and non-uniform material vaporization during laser processing, the actual contour of the blind hole is prone to deformation (such as uncontrolled cone angle and bottom depression). Currently, it is impossible to detect the deformation of the blind hole in real time during processing. The blind hole can only be destructively inspected after processing is completed. For example, the workpiece is removed from the production line, and after resin embedding and curing, the cross-section of the blind hole is physically cut. Then, two-dimensional morphological data is obtained by scanning electron microscopy. However, the detection results only reflect the geometric features of a single cross-section, and the blind hole needs to be structurally destroyed, resulting in low detection efficiency. At the same time, since the above solution can only be performed after processing, it cannot reflect the changes in the morphological structure of the blind hole during processing in real time. This makes it impossible to complete the laser processing parameter adjustment process in a timely manner, resulting in the inability to guarantee the processing qualification rate. Summary of the Invention

[0003] The purpose of this invention is to provide a blind hole contour detection method and system, which can scan the blind hole in real time based on an optical coherence imaging system during the blind hole preparation process, generate a blind hole contour model through point cloud, and further obtain the corresponding blind hole contour parameters through the blind hole contour model to ensure the stability and consistency of the subsequent blind hole processing quality.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] On the one hand, a blind hole contour detection method is provided, which includes the following steps:

[0006] During the laser processing of blind holes, the blind holes are scanned in real time using an optical coherence imaging system to obtain interference light intensity data corresponding to the current shape of the blind holes.

[0007] A point cloud map of the blind hole morphology is constructed based on the interference light intensity data;

[0008] Generate a blind hole contour model based on the point cloud map of the blind hole morphology;

[0009] Furthermore, the blind hole contour parameters are obtained based on the blind hole contour model.

[0010] On the other hand, a blind hole contour detection system is also provided, which includes:

[0011] The spectral acquisition module is used to scan the blind hole in real time during the blind hole preparation process to obtain interference light intensity data corresponding to the current blind hole morphology;

[0012] A data processing module is used to perform noise removal on the interference light intensity data to obtain first preprocessed light intensity data, and to perform spectral shaping on the first preprocessed light intensity data to obtain second preprocessed light intensity data.

[0013] The point cloud acquisition module is used to perform a fast Fourier transform on the second preprocessed light intensity data to generate a point cloud map of the blind hole morphology.

[0014] A contour generation module is used to generate a blind hole contour model based on the point cloud map of the blind hole morphology.

[0015] And an evaluation module, which obtains blind hole contour parameters based on the blind hole contour model.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] This invention eliminates the need for destructive testing of blind holes after processing. Instead, during the blind hole fabrication process, the blind hole is scanned in real time using an optical coherence imaging system, and a blind hole contour model is generated from point clouds. The corresponding blind hole contour parameters can then be obtained from the blind hole contour model, and the laser processing parameters can be adjusted and optimized in real time based on these parameters. This achieves real-time closed-loop feedback control for blind hole laser processing, ensuring the stability and consistency of subsequent blind hole processing quality. Attached Figure Description

[0018] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0019] Figure 1 This is a flowchart illustrating the blind hole contour detection method in this application;

[0020] Figure 2 This is a schematic diagram of the optical coherent imaging system in this application;

[0021] Figure 3 This is a point cloud diagram of the blind hole morphology in this application;

[0022] Figure 4 This is a schematic diagram of the blind hole contour detection system in this application. Detailed Implementation

[0023] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0024] The following detailed description is exemplary and intended to provide further detailed explanation of the invention. Unless otherwise specified, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this invention is for describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention.

[0025] Example 1

[0026] like Figure 1 As shown, this embodiment provides a blind hole contour detection method, including the following steps:

[0027] S100. Based on laser processing equipment, blind holes are prepared on the workpiece, and during the blind hole preparation process, the blind holes are scanned in real time by an optical coherence imaging system to obtain interference light intensity data corresponding to the current blind hole morphology.

[0028] Specifically, such as Figure 2 As shown, the optical coherent imaging system includes:

[0029] The light source module includes: a broadband light source 1, which is used to output beams of multiple wavelengths. In this embodiment, the broadband light source 1 can be a superluminescent diode with a center wavelength of 840nm and a bandwidth of 50nm; and an optical fiber isolator 2, which is disposed in the optical path of the broadband light source 1. For example, in this embodiment, the optical fiber isolator 2 can be connected in series with the broadband light source 1 through an optical fiber patch cord, and the insertion loss of the optical fiber isolator 2 is ≤0.5dB and the return loss is ≥50dB.

[0030] Fiber optic coupler 3, which can be manufactured using a fused taper process, has a beam splitting ratio of 50:50;

[0031] The reference arm system includes: a first polarizer 4, a first collimating lens 5, a first focusing lens 6 and a reflector 7 arranged sequentially along the optical path; in this embodiment, the focal length of the first collimating lens 5 is 20mm, the focal length of the first focusing lens 6 is 50mm, and the side of the reflector 7 facing the first focusing lens 6 is coated with a dielectric film with a reflectivity ≥98%.

[0032] The sample arm system includes: a second polarizer 8, a second collimating lens 9, a two-dimensional galvanometer 10, and a second focusing lens 11 arranged sequentially along the optical path; in this embodiment, the focal length of the second collimating lens 9 is 20mm, the focal length of the second focusing lens 11 is 30mm, and the scanning angle range of the two-dimensional galvanometer 10 is ±15°.

[0033] The dichroic mirror 15 has a first coating on the side facing the second focusing lens 11 of the sample arm system and a second coating on the side facing the laser beam. The first coating has a reflectivity of ≥92% for light in the wavelength range of 800-900nm, and the second coating has a transmittance of ≥95% for the laser beam.

[0034] And, a data acquisition module, which includes: a spectrometer 12; a data acquisition card 13, which is communicatively connected to the spectrometer 12; and a display 14, which is electrically connected to the data acquisition card 13;

[0035] The first port of the fiber optic coupler 3 is connected to the fiber optic isolator 2 and the spectrometer 12 via optical fibers, and the second port is connected to the reference arm system and the sample arm system via optical fibers.

[0036] The light emitted by the broadband light source 1 enters the fiber coupler 3 through the fiber isolator 2 and is split into two paths by the fiber coupler 3. One path of light enters the reference arm system as reference light and passes through the first polarizer 4, the first collimating lens 5, and the first focusing lens 6 in sequence. It is then reflected by the mirror 7, passes through the first focusing lens 6, the first collimating lens 5, and the first polarizer 4 in sequence, and returns to the fiber coupler 3. The other path of light enters the sample arm system as sample light and passes through the second polarizer 8, the second collimating lens 9, the two-dimensional galvanometer 10, and the second focusing lens 11 in sequence. It is then reflected by the dichroic mirror 15. The reflected beam is coaxial with the laser beam L (output by the laser) transmitted through the dichroic mirror 15 and is combined with the laser beam L to form a combined beam Lf acting on the surface of the workpiece 16 (such as a PCB board). After the broadband light source 1 emits light, the two-dimensional galvanometer 10 continuously scans in the XY plane with a step size of 10μm and a scanning range of 1mm×1mm to deflect the sample light in real time.

[0037] Furthermore, the combined light beam Lf acts on the surface of the workpiece to form a blind hole. At the same time, as the blind hole is formed, the combined light beam Lf undergoes backscattering within the blind hole. The scattered light then passes sequentially through the dichroic mirror 15, the second focusing lens 11, the two-dimensional galvanometer 10, the second collimating lens 9, and the second polarizer 8 before returning to the fiber coupler 3.

[0038] Furthermore, the two beams returning to the light coupler 3 interfere with each other, and the interference light intensity data is collected by the spectrometer 12 and sent to the data acquisition card 13 and displayed on the display 14. In this embodiment, the detection wavelength range of the spectrometer 12 is 810-870nm.

[0039] Therefore, in this embodiment, the coaxial output and beam combining of the laser beam L and the sample light can be achieved through the dichroic mirror 15. This allows the blind hole to be processed by the beam combining light, while the scattered light scattered by the blind hole returns to the light coupler 3 to interfere with the reference light, so as to obtain the interference light intensity data corresponding to the current blind hole morphology in real time.

[0040] S200. Constructing a point cloud map of the blind hole morphology based on the interference light intensity data, specifically including the following steps:

[0041] S210. Using a wavenumber space equal division model, the interference light intensity data is converted from wavelength space to wavenumber space, and uniform wavenumber interval sampling is performed through interpolation calculation to obtain several discrete wavenumbers. The wavenumber space equal division model is as follows:

[0042]

[0043] Where, λ N λ is the maximum wavelength of the output beam from broadband light source 1, λ is the minimum wavelength of the output beam from broadband light source 1, and N is the total number of pixels in the photodetector array of spectrometer 12; k t k1, k N Let be the t-th discrete wavenumber, the starting wavenumber, and the ending wavenumber, respectively, where t is the index of the wavenumber sequence and t = 1, 2, ..., N;

[0044] S220. Noise removal is performed on the interference light intensity data to obtain first preprocessed light intensity data;

[0045] Specifically, the noise cancellation includes DC term cancellation and autocorrelation term cancellation, wherein the DC term cancellation includes the following steps:

[0046] The DC component is eliminated by changing the phase of the reference arm system by moving the reference arm system and taking the difference between the interference light intensity I(k) before and after the phase change. For example, in this embodiment, the reflector 7 of the reference arm system can be moved by 210nm to change the interference phase by π / 2, and the difference between the two sets of interference light intensities before and after the phase change can be taken.

[0047] Specifically, the interference light intensity I(k) before and after the phase change can be calculated based on the following formula:

[0048]

[0049] In the formula, T r Let T be the transmission efficiency coefficient of the reference arm system, and T r =P3 / P1, where P1 and P3 are the optical power of the reference light not entering the reference arm system and the optical power of the reference light illuminating the end of the reference arm system, respectively; T s Let T be the transfer efficiency coefficient of the sample arm system, and T s=P4 / P2, where P4 and P2 are the optical power of the sample light not entering the sample arm system and the optical power of the sample light illuminating the end of the sample arm system, respectively; S(k) is the spectral density distribution of broadband light source 1; k represents the discrete wavenumber; h is the distance between the virtual image of the reference mirror and the first backscattering point in the blind aperture; P(h) is the backscattering coefficient of the backscattering point in the blind aperture at a distance h from the virtual image of the reference mirror; h' is the distance between the virtual image of the reference mirror and the second backscattering point in the sample; P(h') is the backscattering coefficient of the backscattering point in the blind aperture at a distance h' from the virtual image of the reference mirror; n is the group refractive index; i is the imaginary unit; d is the differential sign;

[0050] The elimination of autocorrelation terms includes the following steps:

[0051] Before blind hole processing, the reference arm system is blocked so that the reference light cannot enter the reference arm system. Only the intensity of the light beam output by the spectrometer 12 after being reflected by the dichroic mirror 15 and passing through the sample arm system and the light coupler 3 is collected as an autocorrelation term. Wavenumber correction and Fourier transform are performed on the light intensity to obtain the depth signal corresponding to the autocorrelation term.

[0052] Furthermore, wavenumber correction and Fourier transform are also performed on the interference light intensity data to obtain the original depth signal. The depth signal corresponding to the autocorrelation term is subtracted from the original depth signal to complete the autocorrelation term elimination.

[0053] Thus, the autocorrelation term can be attenuated to a negligible level (e.g., reduced to below -40dB) through the above operations. The attenuation to a negligible level is an indicator well known to those skilled in the art and will not be described in detail here.

[0054] S230. Perform spectral shaping on the first preprocessed light intensity data to obtain the second preprocessed light intensity data, which specifically includes the following steps:

[0055] The spectral correction coefficient is calculated based on the proportional relationship of the spectral density distribution, wherein the proportional relationship of the spectral density distribution can be obtained by the following formula:

[0056] c(λ i )=S g (λ i ) / S a (λ i )

[0057] In the formula, c(λ) i ) represents the proportional relationship of spectral density distribution; S g (λ i S is the spectral density function of a Gaussian light source. a (λ i ) is the spectral density function of broadband light source 1; λi The wavelength of the i-th type of beam generated by broadband light source 1;

[0058] The spectral correction coefficient d(λ) is calculated based on the proportional relationship. i ), and the spectral correction coefficient d(λ) i The spectral correction coefficient d(λ) is multiplied by the first preprocessed light intensity data to complete spectral shaping, thereby compensating for light source non-uniformity and system transmission loss. The product is then used as the second preprocessed light intensity data. i The result is obtained by calculating using the following formula:

[0059]

[0060] Where max[·] represents taking the maximum value;

[0061] S240. Perform a Fast Fourier Transform (FFT) on the second preprocessed light intensity data to generate a point cloud map of the blind hole morphology. This specifically includes the following steps:

[0062] The second preprocessed light intensity data is subjected to a Fast Fourier Transform based on the following formula to extract the interference light intensity I(z) at the axial depth z of the blind hole:

[0063]

[0064] In the formula, I(z) is the interference light intensity at the axial depth z of the blind aperture obtained after fast Fourier transform; z is the axial depth of the blind aperture, used to describe the depth of the blind aperture; Γ(z) is the self-coherence function of broadband light source 1; R r Let δ(0) be the reflectivity of mirror 7 in the reference arm system, and let δ(0) be the reflection peak of the reference arm system, serving as the measurement reference; δ(·) be the Dirac function, and δ(z±Δl) be the reflectivity of mirror 7 in the reference arm system. i ) indicates that the optical path difference is Δl i The reflection or scattering source at the axial depth of the time; δ(z±Δl) ij ) indicates that the optical path difference is Δl ij The source of reflection or scattering at the axial depth of the time; R i R j Let be the reflectance of the i-th layer and the j-th layer of the inner wall of the blind hole, respectively. Since the inner wall of the blind hole is usually a sloping structure, different light reflection signals correspond to different depths on the sloping surface, i.e., the depths of different layers on the inner wall of the blind hole. The number of layers on the inner wall of the blind hole = axial depth z / axial resolution; Δl i Δl represents the optical path difference between the i-th layer of the blind hole inner wall and the reference arm system. ij The optical path difference between the i-th and j-th layers of the inner wall of the blind hole;

[0065] The z value is obtained based on the interference signal intensity I(z) at the axial depth z of the blind hole, and the point cloud map of the blind hole is constructed by combining it with the two-dimensional scanning position coordinates of the corresponding two-dimensional galvanometer 10. The point cloud coordinates in the point cloud map are (x,y,z), where (x,y) are the two-dimensional scanning position coordinates of the two-dimensional galvanometer 10 when the interference signal intensity I(z) at the axial depth z of the blind hole is obtained.

[0066] Specifically, the two-dimensional galvanometer 10 deflects according to the time sequence to scan in the XY plane, and each scanning position corresponds to a unique set of two-dimensional coordinates (x, y). At the same time, at each two-dimensional coordinate (x, y), the interference light intensity I(z) at the axial depth z is acquired synchronously. The actual axial depth z at each z position is calculated based on the interference light intensity I(z). By stitching the two-dimensional coordinates (x, y) and z, a three-dimensional point cloud (x, y, z) can be obtained.

[0067] S300. Reconstruct the blind hole contour curve based on the point cloud map of the blind hole morphology to generate a blind hole contour model, which specifically includes the following steps:

[0068] S310. In the point cloud map, the depth position corresponding to the maximum point cloud density in the depth direction (i.e., z direction) is determined as the bottom of the blind hole. At the same time, discrete point clouds located below the bottom of the blind hole (most of which are optical multiple reflection artifacts, so they need to be removed) are removed to avoid interference.

[0069] S320. Extract all point cloud coordinates above the bottom of the blind hole to use as point cloud data for the inner wall of the blind hole;

[0070] S330. Fit the point cloud data of the bottom and sidewalls of the blind hole to generate a blind hole contour model (e.g., Figure 3 (as shown)

[0071] S400. Obtain blind hole contour parameters based on the blind hole contour model. The blind hole contour parameters include one or more of the following: upper opening diameter D1, bottom diameter D2, inner wall taper T, actual blind hole depth H, bottom flatness σ, etc. The blind hole processing quality is evaluated based on the blind hole contour parameters, and the laser processing parameters are adjusted based on the evaluation results.

[0072] Furthermore, in this embodiment, the maximum lateral span at the upper opening of the blind hole is taken as the upper opening diameter D1, and the maximum lateral span at the bottom of the blind hole is taken as the bottom diameter D2.

[0073] Simultaneously, based on the upper opening diameter D1, the bottom diameter D2, and the actual depth H of the blind hole, the inner wall taper T, which characterizes the inclination of the inner wall of the blind hole, is calculated. The specific calculation formula is as follows:

[0074]

[0075] In the formula, D1 is the diameter of the upper opening, D2 is the diameter of the bottom, and H is the actual depth of the blind hole;

[0076] Furthermore, the bottom flatness σ is obtained based on the following formula:

[0077]

[0078] In the formula, σ is the standard deviation of the depth values ​​(i.e., z values) of all points at the bottom of the blind hole, and this standard deviation is used as the bottom flatness; z is the average depth value of all points at the bottom of the blind hole. k Let N be the depth value of the k-th point at the bottom of the blind hole, and N be the total number of points at the bottom of the blind hole.

[0079] Based on this, the processing quality of the blind hole is evaluated based on the blind hole contour parameters, and the laser processing parameters are adjusted in real time based on the evaluation results. For example, if the actual depth H of the blind hole is less than the preset value and the inner wall taper T exceeds the preset value, the blind hole processing quality is considered unqualified. Furthermore, the laser processing parameters are adjusted based on the blind hole contour parameters to perform closed-loop adjustment. For example, when the upper opening diameter D1 and the bottom diameter D2 exceed the tolerance, the defocus amount is updated; when the inner wall taper T is too large, the laser power is reduced; when the bottom flatness σ is insufficient, the laser scanning speed is reduced and the number of laser pulses is increased; when the bottom diameter is insufficient, the pulse overlap rate is increased, etc.

[0080] Repeat the above detection and laser processing parameter adjustment process until the blind hole shape meets the processing standards.

[0081] Therefore, this embodiment achieves real-time scanning of the blind hole during the blind hole preparation process using an optical coherence imaging system. This eliminates the need for destructive testing of the blind hole after processing and the generation of a blind hole contour model from point clouds. Furthermore, the corresponding blind hole contour parameters can be obtained from the blind hole contour model, and the laser processing parameters can be adjusted and optimized in real time based on the blind hole contour parameters to complete the closed-loop feedback control of blind hole laser processing. This ensures that the shape of the blind hole contour in subsequent processing approaches the target contour, ultimately achieving stability and consistency in processing quality.

[0082] Example 2

[0083] This embodiment provides a blind hole contour detection system, which is used to implement the blind hole contour detection method described in Embodiment 1, such as... Figure 4 As shown, the blind hole contour detection system includes:

[0084] A spectral acquisition module is used to scan the blind hole in real time during the blind hole preparation process to obtain interference light intensity data corresponding to the current blind hole morphology; in this embodiment, the spectral acquisition module includes the optical coherence imaging system in Embodiment 1;

[0085] The data processing module is used to perform noise removal on the interference light intensity data to obtain first preprocessed light intensity data, and to perform spectral shaping on the first preprocessed light intensity data to obtain second preprocessed light intensity data, the process of which is the same as in Embodiment 1.

[0086] The point cloud acquisition module is used to perform a fast Fourier transform on the second preprocessed light intensity data to generate a point cloud map of the blind hole morphology, and the process is the same as in Example 1.

[0087] The contour generation module is used to generate a blind hole contour model based on the point cloud map of the blind hole morphology, and the process is the same as in Embodiment 1.

[0088] And an evaluation module, which obtains blind hole contour parameters based on the blind hole contour model, and evaluates the processing quality of the blind hole based on the blind hole contour parameters.

[0089] In summary, this invention eliminates the need for destructive testing of blind holes after processing. Instead, during the blind hole fabrication process, the blind hole is scanned in real time using an optical coherence imaging system, and a blind hole contour model is generated from point clouds. The corresponding blind hole contour parameters can then be obtained from the blind hole contour model, and the laser processing parameters can be adjusted and optimized in real time based on these parameters. This achieves real-time closed-loop feedback control for blind hole laser processing, ensuring the stability and consistency of subsequent blind hole processing quality.

[0090] As is known from common technical knowledge, this invention can be implemented through other embodiments that do not depart from its spirit or essential characteristics. Therefore, the disclosed embodiments described above are merely illustrative in all respects and are not the only ones. All modifications within the scope of this invention or its equivalents are included in this invention.

[0091] 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 it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A method for detecting the contour of a blind hole, characterized in that, Includes the following steps: During the laser processing of blind holes, the blind holes are scanned in real time using an optical coherence imaging system to obtain interference light intensity data corresponding to the current shape of the blind holes. A point cloud map of the blind hole morphology is constructed based on the interference light intensity data; Generate a blind hole contour model based on the point cloud map of the blind hole morphology; Furthermore, the blind hole contour parameters are obtained based on the blind hole contour model.

2. The blind hole contour detection method as described in claim 1, characterized in that, The optical coherent imaging system includes: Broadband light source, which is used to output beams of multiple wavelengths; Fiber optic coupler; The reference arm system includes: a first polarizer, a first collimating lens, a first focusing lens and a reflector arranged sequentially along the optical path, wherein the side of the reflector facing the first focusing lens is coated with a dielectric film with a reflectivity ≥98%. The sample arm system includes: a second polarizer, a second collimating lens, a two-dimensional galvanometer, and a second focusing lens arranged sequentially along the optical path; A dichroic mirror has a first coating on the side facing the second focusing lens of the sample arm system and a second coating on the side facing the laser beam. The first coating has a reflectivity of ≥92% for light in the wavelength range of 800-900nm, and the second coating has a transmittance of ≥95% for the laser beam. And, spectrometer; The first port of the fiber optic coupler is connected to the fiber optic isolator and the spectrometer via optical fibers, and the second port is connected to the reference arm system and the sample arm system via optical fibers; and interference light intensity data is acquired by the spectrometer.

3. The blind hole contour detection method as described in claim 1, characterized in that, Constructing a point cloud map of the blind hole morphology based on the interference light intensity data includes the following steps: The interference light intensity data is subjected to DC term elimination and autocorrelation term elimination to obtain the first preprocessed light intensity data; The first preprocessed light intensity data is spectrally shaped to obtain the second preprocessed light intensity data. Additionally, a fast Fourier transform is performed on the second preprocessed light intensity data to generate a point cloud map of the blind hole morphology.

4. The blind hole contour detection method as described in claim 3, characterized in that, The DC term elimination includes the following steps: The DC component is eliminated by changing the phase of the reference arm system and taking the difference between the interference light intensity I(k) before and after the phase change. The interference light intensity I(k) before and after the phase change can be calculated based on the following formula: In the formula, T r Let T be the transmission efficiency coefficient of the reference arm system. r =P3 / P1, where P1 and P3 are the optical power of the reference light not entering the reference arm system and the optical power of the reference light illuminating the end of the reference arm system, respectively; T s Let T be the transfer efficiency coefficient of the sample arm system, and T s =P4 / P2, where P4 and P2 are the optical power of the sample light not entering the sample arm system and the optical power of the sample light illuminating the end of the sample arm system, respectively; S(k) is the spectral density distribution of broadband light source 1; k represents the discrete wavenumber; h is the distance between the virtual image of the reference mirror and the first backscattering point in the blind aperture; P(h) is the backscattering coefficient of the backscattering point in the blind aperture at a distance h from the virtual image of the reference mirror; h' is the distance between the virtual image of the reference mirror and the second backscattering point in the sample; P(h') is the backscattering coefficient of the backscattering point in the blind aperture at a distance h' from the virtual image of the reference mirror; n is the group refractive index; i is the imaginary unit; d is the differential sign.

5. The blind hole contour detection method as described in claim 3, characterized in that, The elimination of autocorrelation terms includes the following steps: Only the light intensity of the beam output after passing through the sample arm system and the optical coupler is collected as an autocorrelation term, and wavenumber correction and Fourier transform are performed on the light intensity to obtain the depth signal corresponding to the autocorrelation term. Furthermore, wavenumber correction and Fourier transform are also performed on the interference light intensity data to obtain the original depth signal. The depth signal corresponding to the autocorrelation term is subtracted from the original depth signal to complete the autocorrelation term elimination.

6. The blind hole contour detection method as described in claim 3, characterized in that, The first preprocessed light intensity data is subjected to spectral shaping to obtain the second preprocessed light intensity data, which includes the following steps: The spectral correction coefficient is calculated based on the proportional relationship of the spectral density distribution, wherein the proportional relationship of the spectral density distribution is obtained by the following formula: c(λ i )=S g (l i ) / S a (l i ) In the formula, c(λ) i ) represents the proportional relationship of spectral density distribution; S g (λ i S is the spectral density function of a Gaussian light source. a (λ i ) represents the spectral density function of the broadband light source in the optical coherent imaging system; λ i The wavelength of the i-th beam generated by the broadband light source of the optical coherent imaging system; Based on the proportional relationship of spectral density distribution c(λ) i Calculate the spectral correction coefficient d(λ) i ), and the spectral correction coefficient d(λ) i The spectral correction coefficient d(λ) is multiplied by the first preprocessed light intensity data to obtain the second preprocessed light intensity data. i The result is obtained by calculating using the following formula: Where max[·] represents taking the maximum value.

7. The blind hole contour detection method as described in claim 3, characterized in that, The second preprocessed light intensity data is subjected to a Fast Fourier Transform to generate a point cloud map of the blind hole morphology, including the following steps: The second preprocessed light intensity data is subjected to a Fast Fourier Transform based on the following formula to extract the interference light intensity I(z) at the axial depth z of the blind hole: In the formula, I(z) is the interference light intensity at the axial depth z of the blind aperture obtained after fast Fourier transform; z is the axial depth of the blind aperture; Γ(z) is the self-coherence function of the broadband light source of the optical coherent imaging system; R r Let δ(0) be the reflectivity of the mirror in the reference arm system of the optical coherent imaging system, and δ(·) be the reflection peak of the reference arm system of the optical coherent imaging system. δ(z±Δl) is the Dirac function. i ) indicates that the optical path difference is Δl i The source of reflection or scattering at the axial depth of the time; δ(z±Δl ij ) indicates that the optical path difference is Δl ij The source of reflection or scattering at the axial depth of the time; R i R j These represent the reflectance of the i-th layer and the j-th layer of the inner wall of the blind hole, respectively; Δl i Δl represents the optical path difference of the i-th layer of the inner wall of the blind hole and the reference arm system of the optical coherence imaging system. ij The optical path difference between the i-th and j-th layers of the inner wall of the blind hole; The z value is obtained based on the interference signal intensity I(z) at the axial depth z of the blind hole, and the two-dimensional scanning position coordinates of the two-dimensional galvanometer of the optical coherent imaging system are stitched together with the z value to obtain the point cloud map of the blind hole.

8. The blind hole contour detection method as described in claim 3, characterized in that, Generate a blind hole contour model based on the point cloud image of the blind hole morphology, including the following steps: In the point cloud image, the depth position corresponding to the maximum point cloud density in the depth direction is determined as the bottom of the blind hole, and discrete point clouds located below the bottom of the blind hole are removed. Extract all point cloud coordinates above the bottom of the blind hole to serve as point cloud data for the inner wall of the blind hole; The point cloud data of the bottom and sidewalls of the blind hole are fitted to generate the blind hole contour model.

9. The blind hole contour detection method as described in claim 1, characterized in that, The blind hole profile parameters include one or more of the following: upper opening diameter, bottom diameter, inner wall taper, actual depth of the blind hole, and bottom flatness.

10. A blind hole contour detection system, characterized in that, include: The spectral acquisition module is used to scan the blind hole in real time during the blind hole preparation process to obtain interference light intensity data corresponding to the current blind hole morphology; A data processing module is used to perform noise removal on the interference light intensity data to obtain first preprocessed light intensity data, and to perform spectral shaping on the first preprocessed light intensity data to obtain second preprocessed light intensity data. The point cloud acquisition module is used to perform a fast Fourier transform on the second preprocessed light intensity data to generate a point cloud map of the blind hole morphology. A contour generation module is used to generate a blind hole contour model based on the point cloud map of the blind hole morphology. And an evaluation module, which obtains blind hole contour parameters based on the blind hole contour model.

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