A multi-interface measurement system for transparent matter based on spectral domain interferometry

Abstract

The application discloses a transparent substance multi-interface measurement system based on spectral domain interference and relates to the technical field of transparent substance measurement.The system comprises a broadband light source module, a line illumination interference module, a scanning module, a spectral light detection module and a data processing and control module electrically connected with the spectral light detection module.The application completely solves the problem that the multi-interface signals in traditional white light interference cannot be distinguished and eliminates the interference of crosstalk false peaks.Single measurement can obtain multi-dimensional parameters, realizes the functional integration of "one device replacing three devices" and satisfies the measurement speed of industrial online detection.

Description

Technical Field

[0001] This invention relates to the field of transparent material measurement technology, and in particular to a multi-interface measurement system for transparent materials based on spectral domain interferometry. Background Technology

[0002] White light interferometry, due to its nanometer-level vertical resolution, non-contact characteristics, and rapid measurement capabilities, has become the standard method for precision surface topography inspection. However, when the object being measured is a transparent material, traditional white light interferometry faces a fundamental technical obstacle: multi-interface reflection of light within the material causes interference signal aliasing, producing spurious interference peaks and making it impossible to accurately identify the true positions of each surface. Specific technical problems include: 1. Multi-interface signal aliasing: Each optical interface of a transparent material (such as the upper surface, lower surface, and internal layer interface) generates an interference signal. When the interface spacing is less than the coherence length of the light source, the interference envelopes completely overlap, and the traditional peak detection algorithm fails. 2. Crosstalk interference spurious peaks: The reflected light from different interfaces interferes with each other, producing "ghost peaks" that correspond to the real surface, interfering with the measurement results; 3. Insufficient signal-to-noise ratio: The reflectivity of a single interface of transparent materials such as glass is only about 4%, which is much lower than that of opaque materials (30-40%), resulting in weak interference signals that are easily drowned out by noise. 4. Measurement bias introduced by dispersion: The dispersion effect of transparent materials causes differences in optical path length of light of different wavelengths. Traditional monochromatic light or narrow-band light sources cannot correct this bias, affecting the accuracy of thickness measurement.

[0003] Existing solutions such as laser confocal microscopy can measure transparent materials, but they suffer from problems such as slow measurement speed and sensitivity to tilted surfaces; spectral reflectance methods can measure film thickness but cannot obtain three-dimensional morphology; although multi-wavelength interferometers have been reported, they mostly use time-sequence switching methods, resulting in long measurement times, which are difficult to meet the cycle time requirements of industrial online inspection.

[0004] In summary, developing a novel transparent material measurement system to meet the non-contact, high-precision measurement needs of transparent or semi-transparent materials such as glass substrates, polymer films, and sapphire wafers has become a research topic that urgently needs to be addressed by those skilled in the art. Summary of the Invention

[0005] This invention provides a multi-interface measurement system for transparent materials based on spectral domain interferometry, comprising: The system comprises a broadband light source module (1), a line illumination interference module (2), a scanning module (3), a spectral detection module (4), and a data processing and control module electrically connected to the spectral detection module (4); wherein the light output end of the broadband light source module (1) is coupled to the light incident end of the line illumination interference module (2); the interference signal output end of the line illumination interference module (2) is connected to the light incident end of the scanning module (3); and the light output end of the scanning module (3) is coupled to the light incident end of the spectral detection module (4).

[0006] The transparent material multi-interface measurement system based on spectral domain interference as described above, wherein the broadband light source module (1) is used to generate broadband illumination light covering the 400-900nm wavelength band; along the optical path propagation direction, the broadband light source module (1) sequentially includes a broadband light source (11), a first collimating lens (12), a cylindrical lens (13) and a first imaging slit (14).

[0007] The transparent material multi-interface measurement system based on spectral domain interference as described above, wherein the line illumination interference module (2) includes, in sequence along the propagation direction of the incident light path, a microscope objective (21), a beam splitter (22), and a reference mirror (23) coupled to the optical path of the beam splitter (22).

[0008] As described above, in the transparent material multi-interface measurement system based on spectral domain interference, the beam splitter (22) splits the linear illumination beam calibrated by the microscope objective (21) into two beams: one is a reference beam that is incident on the reference mirror (23); the other is a measurement beam that is incident on the surface of the sample to be measured. The reference beam of the reference beam and the sample return beam of the measurement beam return along the original beam path to the beam splitter (22) and are combined to generate a broadband interference signal carrying the multi-interface information of the sample to be measured. The interference signal is output from the output end of the line illumination interference module (2) and incident on the scanning module (3).

[0009] As described above, in the transparent material multi-interface measurement system based on spectral domain interference, the scanning module (3) is located in the interference signal transmission optical path between the line illumination interference module (2) and the spectral spectrophotometer (4), and is used to drive the imaging field of the interference signal and the detection field of the spectral spectrophotometer (4) to generate a relative displacement, so that the linear illumination spot traverses the entire test area of ​​the sample.

[0010] The transparent material multi-interface measurement system based on spectral domain interference described above has a semi-transparent and semi-reflective mirror inside the scanning module (3), which is fixed at a 45° angle to the output optical axis of the broadband light source module (1).

[0011] The transparent material multi-interface measurement system based on spectral domain interference as described above, wherein along the propagation direction of the interference signal light path, the spectral beam detection module (4) sequentially includes a second imaging slit (41), a second collimating lens (42), a dispersive element (43), a focusing lens (44), and an area array detector (45).

[0012] The above-described transparent material multi-interface measurement system based on spectral domain interference, wherein the dispersive element (43) adopts a volume holographic transmission grating with a grating line density of 600 lines / mm.

[0013] As described above, in the transparent material multi-interface measurement system based on spectral domain interference, the X direction of the pixel array of the area array detector (45) is parallel to the length direction of the second imaging slit (41), corresponding to the one-dimensional spatial position of the linear illumination spot on the sample being measured; the Y direction of the pixel array is parallel to the beam splitting direction of the dispersive element (43), corresponding to different spectral wavelength channels.

[0014] This invention also provides a multi-wavelength dispersion decoupling method for multi-interface transparent materials based on spectral domain interferometry, applied to the data processing and control module of a multi-interface transparent material measurement system based on spectral domain interferometry, including: Step S21: Preprocess the received interference spectral data to eliminate systematic errors and noise; Step S22: Perform frequency domain transformation on the preprocessed interferometric spectral data to select a candidate interface set; Step S23: Divide the preprocessed interference spectrum data into M continuous wavelength sub-bands, and perform frequency domain analysis on each wavelength sub-band to obtain the peak position dataset corresponding to each sub-band; Step S24: For each candidate interface in the candidate interface set, extract its corresponding peak position in each sub-band and construct its dispersion characteristic vector; Step S25: Based on the dispersive feature vector, identify the authenticity of the candidate interface set and distinguish between the real interfaces and crosstalk pseudo-peaks. Step S26: Calculate the position of the identified real interface, and calculate the thickness of the transparent layer and the refractive index distribution of the sample under test based on the calculated position information.

[0015] The beneficial effects achieved by this invention are as follows: it completely solves the problem of indistinguishable multi-interface signal aliasing in traditional white light interferometry and eliminates crosstalk spurious peak interference; it can acquire multi-dimensional parameters in a single measurement, realizing the functional integration of "one device replacing three devices"; and its measurement speed meets the requirements of industrial online detection. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present 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 only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0017] Figure 1 , Figure 2 This is a schematic diagram of a multi-interface measurement system for transparent materials based on spectral domain interferometry, provided in Embodiment 1 of this application; Figure 3 This is a flowchart of a multi-interface, multi-wavelength dispersion decoupling method for transparent materials based on spectral domain interference, provided in Embodiment 2 of this application. Detailed Implementation

[0018] The technical solutions of the embodiments of the present 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 the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Example 1 like Figure 1 As shown, Embodiment 1 of this application provides a multi-interface measurement system for transparent materials based on spectral domain interferometry, including: a broadband light source module 1, a line illumination interferometry module 2, a scanning module 3, a spectral spectrophotometer detection module 4, and a data processing and control module electrically connected to the spectral spectrophotometer detection module 4; wherein, the light output end of the broadband light source module 1 is optically coupled to the light incident end of the line illumination interferometry module 2; the interference signal output end of the line illumination interferometry module 2 is optically connected to the light incident end of the scanning module 3; and the light output end of the scanning module 3 is optically coupled to the light incident end of the spectral spectrophotometer detection module 4.

[0020] refer to Figure 2 The broadband light source module 1 is used to generate broadband illumination light covering the 400-900nm wavelength band; along the optical path propagation direction, the broadband light source module 1 includes a broadband light source 11, a first collimating lens 12, a cylindrical lens 13 and a first imaging slit 14 in sequence. The first collimating lens 12 is used to collimate the divergent beam output by the broadband light source 11 into a parallel beam; the cylindrical lens 13 is used to compress the parallel light into a linear illumination spot perpendicular to the scanning direction, with a line length covering a 3.5mm field of view and a line width of less than 20μm; the first imaging slit 14 is disposed in the outgoing light path of the cylindrical lens 13, with a slit width of 10μm-50μm, used to limit the spatial divergence angle of the light source and filter out stray light. The shaped linear illumination beam is emitted from the first imaging slit 14 and coupled to the line illumination interference module 2 via reflection from the scanning module 3.

[0021] The line illumination interference module 2 is used to receive the line illumination beam reflected by the scanning module 3, construct the Michelson interference optical path, so that after the line beam illuminates the transparent sample under test, a broadband interference signal carrying the height and thickness information of the sample's multiple interfaces is generated; the line illumination interference module 2 includes a microscope objective 21, a beam splitter 22, and a reference mirror 23 coupled to the optical path of the beam splitter 22 in sequence along the propagation direction of the incident optical path. The beam splitter 22 is used to split the linear illumination beam calibrated by the microscope objective 21 into two beams: one is a reference beam that is incident on the reference mirror 23; the other is a measurement beam that is incident on the surface of the sample to be measured. The reference beam of the reference beam and the sample return beam of the measurement beam return along the original beam path to the beam splitter 22 and are combined to generate a broadband interference signal carrying multi-interface information of the sample to be measured. This interference signal is output from the output end of the line illumination interference module 2 and incident on the scanning module 3.

[0022] The scanning module 3 is located in the interference signal transmission optical path between the line illumination interference module 2 and the spectral dispersive detection module 4. It is used to drive the imaging field of the interference signal and the detection field of the spectral dispersive detection module 4 to generate a relative displacement, so that the linear illumination spot traverses the entire test area of ​​the sample. It has a semi-transparent and semi-reflective mirror inside, which is fixed at a 45° angle to the output optical axis of the broadband light source module 1. The semi-transparent and semi-reflective mirror has a dual optical path control function: first, it reflects the linear illumination light emitted from the broadband light source module 1 and couples the beam to the microscope objective 21 of the line illumination interference module 2 to complete the turning and transmission of the illumination optical path; second, it transmits the broadband interference signal returned by the illumination interference module 2 to the spectral spectrophotometer detection module 4 to complete the transmission of the interference signal.

[0023] The spectral detection module 4 is used to simultaneously decouple the interference signal in spatial and spectral dimensions, obtain a two-dimensional interference spectrum, and convert the optical signal into an electrical signal for transmission to the data processing and control module. Along the propagation direction of the interference signal optical path, the spectral detection module 4 includes, in sequence, a second imaging slit 41, a second collimating lens 42, a dispersive element 43, a focusing lens 44, and an area array detector 45. The second imaging slit 41 is located in the transmitted light output path of the scanning module 3, and the slit width is 10μm-25μm. The second collimating lens 42 has a focal length range of 50mm-200mm and is used to collimate the interference signal passing through the second imaging slit 41 into a parallel beam, which is then incident on the dispersive element 43. The dispersive element 43 is a volume holographic transmission grating (VPH). A transmission grating (with a line density of 600 lines / mm) is used to disperse the incident parallel interference signal according to different wavelengths in a dimension perpendicular to the length direction of the second imaging slit 41, so that light of different wavelengths exits at different angles, achieving spectral separation. The focusing lens 44 is used to focus the dispersed interference signal separated by wavelength onto the photosensitive surface of the area array detector 45. The area array detector 45 adopts a high-speed CMOS camera or CMOS camera, and the X direction (row direction) of its pixel array is parallel to the length direction of the second imaging slit 41, corresponding to the one-dimensional spatial position of the linear illumination spot on the sample under test. The Y direction (column direction) of the pixel array is parallel to the spectral separation direction of the dispersive element 43, corresponding to different spectral wavelength channels. The area array detector 45 can acquire the complete interference spectrum information corresponding to all spatial sampling points in the linear illumination field of view in a single exposure, forming a two-dimensional interference spectrum, realizing synchronous parallel acquisition of spatial and spectral dimensions.

[0024] In this embodiment, the optical path propagation and hardware coordination process of the measurement system during operation is as follows: Under the control of the light source driving unit, the broadband light source 11 outputs a broadband divergent light covering the 400nm-900nm wavelength band. After being collimated into a circular parallel beam by the first collimating lens 12, it is incident on the cylindrical lens 13. The cylindrical lens 13 compresses and shapes the circular parallel beam into a linear illumination beam in a dimension perpendicular to the scanning direction. After being filtered by the first imaging slit 14 to remove stray light and limit the spatial divergence angle, it is incident on the semi-transparent and semi-reflective mirror of the scanning module 3. The semi-transparent and semi-reflective mirror reflects the incident linear illumination light to the microscope objective 21 of the linear illumination interference module 2. After optical correction by the microscope objective 21, the light is incident on the beam splitter 22. The beam splitter 22 splits the linear beam into two beams: one beam is incident on the reference mirror 23 along the reference light path and is reflected to form the reference light; the other beam is directly incident on the surface of the sample to be measured along the measurement light path. The incident light beam is reflected at the upper surface, lower surface and internal optical interfaces of the sample. The reflected light from each interface returns to the beam splitter 22 along the original measurement optical path. It is combined with the reference light reflected by the reference mirror 23 and returned along the original optical path to generate a broadband interference signal carrying information about the multiple interfaces of the sample. The combined broadband interference signal exits from the line illumination interference module 2 and is incident again on the semi-transparent and semi-reflective mirror of the scanning module 3. After being transmitted through the semi-transparent and semi-reflective mirror, it is incident on the spectral detection module 4. After the interference signal enters the spectral detection module 4, it first passes through the second imaging slit 41 for field-of-view limitation and stray light filtering, and then is collimated into a parallel beam by the second collimating lens 42 before being incident on the dispersive element 43. The dispersive element 43 disperses the interference signal according to the wavelength in the dimension perpendicular to the length direction of the second imaging slit 41. The interference light of different wavelengths is focused by the focusing lens 44 and imaged onto the photosensitive surface of the array detector 45. Meanwhile, the scanning module 3 moves at a constant speed along the scanning direction, causing the linear illumination spot to traverse the entire test area of ​​the sample. The area array detector 45 is exposed synchronously and continuously to acquire two-dimensional interference spectral data of the complete measurement field of view and transmit it to the data processing and control module. The data processing and control module performs a multi-wavelength dispersion decoupling method on the received interference spectral data and outputs the multi-interface three-dimensional morphology, film thickness distribution and refractive index distribution of the sample under test.

[0025] Example 2 like Figure 3 As shown, Embodiment 2 of this application provides a multi-interface, multi-wavelength dispersion decoupling method for transparent materials based on spectral domain interferometry, which is applied to the data processing and control module of the multi-interface measurement system for transparent materials based on spectral domain interferometry.

[0026] In this embodiment, the core terms in the entire text are first uniformly defined to ensure that the scheme is clearly expressed and unambiguous: Interference spectral data: refers to the digital two-dimensional matrix data output to the data processing and control module after the area array detector 45 in Example 1 completes photoelectric conversion and analog-to-digital conversion. The X direction of the two-dimensional matrix corresponds to the spatial sampling position of the sample under test, and the Y direction corresponds to the spectral wavelength channel. Each data unit contains light intensity information at the corresponding spatial position and wavelength. Candidate interface: refers to the object to be tested that is suspected to be the optical interface of the sample under test, corresponding to the peak value in the optical path difference domain that exceeds the preset threshold obtained by frequency domain analysis. Each candidate interface corresponds to a unique initial value of optical path difference position. Candidate interface set: refers to the set of all candidate interfaces after frequency domain analysis of the full-spectrum interferometric data.

[0027] This embodiment of a method for multi-interface, multi-wavelength dispersion decoupling of transparent materials based on spectral domain interference specifically includes: Step S21: Preprocess the received interference spectral data to eliminate systematic errors and noise; The preprocessing operations include, but are not limited to: dark field subtraction, reference normalization, wavelength calibration, and wavenumber resampling. Wavelength calibration refers to calibrating the spectral detection module using a standard light source with known characteristic wavelengths, establishing a one-to-one mapping between the pixel coordinates of the spectral dimension of the area array detector and the actual wavelength, completing the wavelength dimension calibration of the spectral signal, and ensuring the accuracy of subsequent wavelength sub-band division. Wavenumber resampling refers to converting the originally equally spaced spectral data into equally spaced spectral data through linear interpolation, eliminating the influence of wavelength nonlinearity on subsequent fast Fourier transform operations, and meeting the operational requirements of frequency domain analysis.

[0028] Step S22: Perform frequency domain transformation on the preprocessed interferometric spectral data to select a candidate interface set; First, a window function is applied to the preprocessed spectral data to suppress spectral sidelobes. In this embodiment, the Hanning window function is used to reduce the interference of spectral leakage on peak detection. Second, a fast Fourier transform is performed on the windowed spectral data to convert the spectral domain data to the optical path difference domain, obtaining the complex spectrum and amplitude data corresponding to the optical path difference domain. Finally, all peaks with amplitudes exceeding 5 times the noise floor are detected in the optical path difference domain, and the optical path difference positions corresponding to each peak are recorded as the initial values ​​of the optical path difference positions of the candidate interfaces. All candidate interfaces corresponding to peaks that meet the conditions are summarized to form a candidate interface set.

[0029] Step S23: Divide the preprocessed interference spectrum data into M continuous wavelength sub-bands, and perform frequency domain analysis on each wavelength sub-band to obtain the peak position dataset corresponding to each sub-band; In this embodiment, the interference spectral data covers the 400nm-900nm band, with M=4, and the specific subband division method is as follows: Subband 1: Wavelength range 400nm to 525nm, center wavelength λ1=462.5nm; Subband 2: Wavelength range 525nm to 650nm, center wavelength λ2=587.5nm; Subband 3: Wavelength range 650nm to 775nm, center wavelength λ3=712.5nm; Subband 4: Wavelength range from 775nm to 900nm, center wavelength λ4=837.5nm.

[0030] As a preferred embodiment, a wavelength overlap region of 10% to 20% is set between adjacent subbands to improve the stability of subsequent dispersion fitting and avoid fitting errors caused by insufficient signal-to-noise ratio of subband edge data.

[0031] In other alternative implementations, the number of sub-bands M can be adjusted according to the number of interface layers of the sample being tested and the measurement accuracy requirements. The value of M ranges from 3 to 8, and the wavelength range of the sub-bands can be adapted and adjusted according to the dispersion characteristics of the material being tested.

[0032] For the interference spectral data corresponding to each wavelength sub-band, independent windowing and fast Fourier transform operations are performed to obtain the optical path difference domain amplitude data corresponding to each sub-band. In the optical path difference domain of each sub-band, the peak position is detected and the optical path difference position corresponding to each peak is recorded to form the peak position dataset corresponding to each sub-band.

[0033] Step S24: For each candidate interface in the candidate interface set, extract its corresponding peak position in each sub-band and construct its dispersion characteristic vector; For the i-th candidate interface in the candidate interface set, obtain its initial value of optical path difference position; in the peak position dataset of each sub-band, search for a matching peak whose deviation from the initial value of optical path difference position is less than a preset tolerance; in this embodiment, the preset tolerance is set to 0.2 μm, and in other optional embodiments, it can be adjusted according to the system measurement range and spectral resolution; if a matching peak that meets the deviation requirement is found in the m-th sub-band, record the optical path difference position corresponding to the matching peak, denoted as . If no matching peak is found, the corresponding position of that sub-band is recorded as a null value; based on the optical path difference positions of the matching peaks recorded in each sub-band, a dispersive feature vector is constructed for the candidate interface: The dispersion feature vector characterizes the variation of the apparent wavelength difference position of the candidate interface with wavelength, serving as the core basis for subsequent interface authenticity identification.

[0034] Step S25: Based on the dispersive feature vector, identify the authenticity of the candidate interface set and distinguish between the real interfaces and crosstalk pseudo-peaks. Based on the dispersive physical properties of transparent materials, this method distinguishes between the real interface and crosstalk spurious peaks, eliminates false interference data, and achieves accurate separation between the real interface and crosstalk spurious peaks. The specific process is as follows: First, clarify the differences in core dispersion characteristics between the real interface and the crosstalk pseudo-peak: For real optical interfaces, their wavelength The following table shows the difference in sightseeing routes and locations. It satisfies the dispersion physical laws of transparent materials, and its characteristic equation is: ,in, Let L be the actual geometric location of the interface, and L be the number of transparent layers above the interface. For the first The geometric thickness of the transparent material layer For the first Transparent material at wavelength The refractive index of transparent materials; the refractive index of transparent materials The relationship between wavelength and dispersion is described by the Sellmeier dispersion equation, expressed as: ,in and The Sellmeier coefficient of the material being tested can be obtained from a material database or determined through pre-calibration of the system. Crosstalk spurious peaks are essentially "ghost peaks" generated by the cross-interference between reflected light from different real interfaces, and their wavelengths vary. The following table shows the difference in sightseeing routes and locations. The characteristic equation for the optical path difference between the two real interfaces is half that of the optical path difference between them: ,in For the real interface i at wavelength The following table shows the differences in sightseeing routes and locations. For the real interface j at wavelength The following table shows the difference in location between the sightseeing routes, and ; Therefore, it can be seen that the dispersion characteristics of the crosstalk pseudo-peak are a linear combination of the dispersion characteristics of two real interfaces, which does not conform to the Sellmeier dispersion model of a single transparent material. This can be used as the core criterion for authenticity identification.

[0035] Subsequently, a least-squares fitting model was established to analyze the dispersive feature vectors of each candidate interface in the candidate interface set. The fitting is performed, and the objective function is expressed as: ,in The position of the matching peak optical path difference of the i-th candidate interface in the m-th sub-band is, i.e. The m-th component in Let λ be the center wavelength of the m-th sub-band, where m ranges from 1 to M, and M is the total number of sub-bands. Calculate the residual of the fitting result of each candidate interface. If the residual is less than the preset threshold (0.2μm in this embodiment), the candidate interface is determined to be a real interface and included in the real interface set R. If the residual is greater than or equal to the preset threshold, the candidate interface is determined to be a suspected crosstalk pseudo-peak and included in the pseudo-peak set G to be verified. For each suspected pseudo-peak in the pseudo-peak set G to be verified, further verification is performed to determine whether it satisfies the characteristic equation of the aforementioned crosstalk pseudo-peak. The specific verification process is as follows: Traverse all pairs of real interfaces in the real interface set R, substitute the dispersion characteristics of each pair of real interfaces into the characteristic equation of the crosstalk pseudo-peak, and calculate the dispersion characteristics of the theoretical pseudo-peak, that is, the apparent path difference position of the theoretical pseudo-peak at the corresponding wavelength. If the deviation between the dispersion characteristics of the theoretical pseudo-peak and the dispersion characteristics of the suspected pseudo-peak (i.e., the apparent path difference position of the suspected pseudo-peak at the corresponding wavelength) is less than the verification threshold, it is confirmed as a crosstalk pseudo-peak and directly removed; if no matching theoretical pseudo-peak dispersion characteristics are found after traversal, the suspected pseudo-peak is re-determined as a real interface and added to the real interface set R.

[0036] When a peak is identified as a crosstalk spurious peak, the following method is used: , Records can be kept for data traceability.

[0037] Step S26: Calculate the position of the identified real interface, and calculate the thickness of the transparent layer and the refractive index distribution of the sample under test based on the calculated position information; For each real interface in the real interface set R, the phase calculation method is used to further improve the position measurement accuracy. The specific process is as follows: Extract the complex spectrum data obtained by fast Fourier transform of the full interference spectrum data, and obtain the phase value at the corresponding peak position of the real interface. The initial value of the optical path difference position of the real interface is corrected with high precision using a phase refinement formula, resulting in the precise position of the refined interface. ,Right now ,in This is the initial value of the optical path difference position obtained by positioning the actual interface using the envelope peak. The center wavelength of the full interference spectrum; After the phase refinement described above, the accuracy of interface height measurement can be improved from approximately 100nm in envelope positioning to 1nm-5nm, achieving sub-nanometer vertical resolution.

[0038] Based on the precise locations of each real interface in the real interface set R, and combined with the material refractive index results obtained from dispersion fitting in step S25, the thickness and refractive index distribution of each transparent layer of the tested sample are calculated. The specific process is as follows: Based on the precise height difference between two adjacent real interfaces, the optical thickness of the transparent layer between the two interfaces is calculated. The formula for calculating the optical thickness is as follows: ,in For the first The optical thickness of the transparent layer, These are the precise locations of two adjacent real-world interfaces; Combined with the refractive index of the material at the center wavelength obtained from the dispersion fitting in step S25 Calculate the geometric thickness of the transparent layer. ,Right now ; Traverse all adjacent real interfaces to complete the thickness distribution calculation of each transparent layer in the entire field of view, and output the refractive index distribution map of each transparent layer.

[0039] After completing the above steps, the data processing and control module outputs the full measurement results of the upper surface three-dimensional morphology, lower surface three-dimensional morphology, three-dimensional morphology of each internal interface, thickness distribution of each transparent layer, and material refractive index distribution of the sample under test.

[0040] The multi-wavelength dispersion decoupling method in this embodiment utilizes the dispersion differences of transparent materials as an "optical fingerprint." By extracting multi-subband dispersion features and fitting them with the Sellmeier physical model, it completely solves the technical problems of multi-interface signal aliasing and crosstalk spurious peak interference in traditional white light interferometry. The spurious peak identification accuracy can reach over 99.9%. At the same time, sub-nanometer-level measurement accuracy is achieved through phase refinement. A single measurement can simultaneously acquire multi-dimensional parameters such as morphology, thickness, and refractive index. The measurement speed meets the cycle time requirements of industrial online inspection and is suitable for the high-precision measurement needs of various transparent / semi-transparent materials such as glass substrates, polymer films, and sapphire wafers.

[0041] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made on the basis of the technical solution of the present invention should be included within the scope of protection of the present invention.

Claims

1. A multi-interface measurement system for transparent materials based on spectral domain interferometry, characterized in that, include: The system comprises a broadband light source module (1), a line illumination interference module (2), a scanning module (3), a spectral detection module (4), and a data processing and control module electrically connected to the spectral detection module (4); wherein the light output end of the broadband light source module (1) is coupled to the light incident end of the line illumination interference module (2); the interference signal output end of the line illumination interference module (2) is connected to the light incident end of the scanning module (3); and the light output end of the scanning module (3) is coupled to the light incident end of the spectral detection module (4).

2. The transparent material multi-interface measurement system based on spectral domain interferometry according to claim 1, characterized in that, The broadband light source module (1) is used to generate broadband illumination light covering the 400-900nm wavelength band; along the optical path propagation direction, the broadband light source module (1) includes a broadband light source (11), a first collimating lens (12), a cylindrical lens (13) and a first imaging slit (14) in sequence.

3. The transparent material multi-interface measurement system based on spectral domain interferometry according to claim 1, characterized in that, The line illumination interference module (2) includes, in sequence, a microscope objective (21), a beam splitter (22) along the propagation direction of the incident light path, and a reference mirror (23) coupled to the optical path of the beam splitter (22).

4. The transparent material multi-interface measurement system based on spectral domain interferometry according to claim 3, characterized in that, The beam splitter (22) splits the linear illumination beam calibrated by the microscope objective (21) into two beams: one is a reference beam that is incident on the reference mirror (23); the other is a measurement beam that is incident on the surface of the sample to be measured. The reference beam of the reference beam and the sample return beam of the measurement beam return along the original beam path to the beam splitter (22) and combine to generate a broadband interference signal carrying multi-interface information of the sample to be measured. The interference signal is output from the output end of the line illumination interference module (2) and incident on the scanning module (3).

5. The transparent material multi-interface measurement system based on spectral domain interferometry according to claim 1, characterized in that, The scanning module (3) is located in the interference signal transmission optical path between the line illumination interference module (2) and the spectral detection module (4). It is used to drive the imaging field of the interference signal and the detection field of the spectral detection module (4) to generate a relative displacement, so that the linear illumination spot traverses the entire test area of ​​the sample.

6. The transparent material multi-interface measurement system based on spectral domain interferometry according to claim 5, characterized in that, The scanning module (3) has a semi-transparent and semi-reflective mirror inside, which is fixed at a 45° angle with the output optical axis of the broadband light source module (1).

7. The transparent material multi-interface measurement system based on spectral domain interferometry according to claim 1, characterized in that, Along the direction of propagation of the interference signal light path, the spectral detection module (4) includes, in sequence, a second imaging slit (41), a second collimating lens (42), a dispersive element (43), a focusing lens (44), and an area array detector (45).

8. The transparent material multi-interface measurement system based on spectral domain interferometry according to claim 7, characterized in that, The dispersive element (43) is a volume holographic transmission grating with a grating line density of 600 lines / mm.

9. The transparent material multi-interface measurement system based on spectral domain interferometry according to claim 7, characterized in that, The X direction of the pixel array of the area array detector (45) is parallel to the length direction of the second imaging slit (41), corresponding to the one-dimensional spatial position of the linear illumination spot on the sample under test; the Y direction of the pixel array is parallel to the beam splitting direction of the dispersive element (43), corresponding to different spectral wavelength channels.

10. A method for multi-interface, multi-wavelength dispersion decoupling of transparent materials based on spectral domain interferometry, applied to the data processing and control module of the transparent material multi-interface measurement system based on spectral domain interferometry as described in any one of claims 1-9, comprising: Step S21: Preprocess the received interference spectral data to eliminate systematic errors and noise; Step S22: Perform frequency domain transformation on the preprocessed interferometric spectral data to select a candidate interface set; Step S23: Divide the preprocessed interference spectrum data into M continuous wavelength sub-bands, and perform frequency domain analysis on each wavelength sub-band to obtain the peak position dataset corresponding to each sub-band; Step S24: For each candidate interface in the candidate interface set, extract its corresponding peak position in each sub-band and construct its dispersion characteristic vector; Step S25: Based on the dispersive feature vector, identify the authenticity of the candidate interface set and distinguish between the real interfaces and crosstalk pseudo-peaks. Step S26: Calculate the position of the identified real interface, and calculate the thickness of the transparent layer and the refractive index distribution of the sample under test based on the calculated position information.

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