A single-axis dispersion line confocal measurement system and method based on a spatial bandpass filter structure

Abstract

The application provides a single-axis dispersion line confocal measurement system and method based on a spatial band-pass filter structure, and belongs to the technical field of optical precision measurement and chromatic confocal imaging. The application reconstructs a system spatial filter chain while retaining the advantages of single-axis structure large inclination adaptability and high-throughput line scanning, and cooperatively introduces an inverse slit and a spatial band-pass filter. The inverse slit introduces a central obstruction in the axial response main lobe region, reshapes the system return response into an inverse Gaussian distribution, thereby enhancing the axial discrimination ability and resolution. The spatial band-pass filter is used for enhancing the spatial selectivity in the line direction, and effectively suppressing the signal crosstalk between adjacent sampling points. The application retains the advantages of large inclination adaptability and high throughput while improving the measurement accuracy and stability of the system.

Description

Technical Field

[0001] This invention relates to a single-axis dispersion line confocal measurement system and method based on a spatial bandpass filter structure, belonging to the field of optical precision measurement and chromatic aberration confocal imaging technology. Background Technology

[0002] Precision surface measurement technology is widely used in semiconductor, electronic manufacturing, and precision machining. Chromatic confocal measurement, with its advantages of non-contact operation, high axial resolution, and rapid spectral demodulation, has become an important technique for precision topography measurement. To improve the efficiency of three-dimensional topography measurement, chromatic confocal technology has expanded from point scanning to line scanning, forming a single-axis chromatic confocal imaging system. This system enables parallel acquisition of multiple points along the line direction and increases measurement throughput.

[0003] Existing single-axis chromatic aberration linear confocal imaging systems typically include an illumination channel, a dispersive focusing unit, a beam splitting unit, a line slit, and a spectral detection unit. They utilize broadband light, after axial dispersion, to establish a one-to-one correspondence between different wavelengths and different focal positions, and acquire the height information of the measured surface by analyzing the reflection spectrum. However, these systems usually employ a spatial filtering structure centered on the line slit. While the line slit provides strong confocal constraint primarily in the vertical direction, its spatial constraint capability in the linear direction is weak, easily leading to aliasing of diffuse reflection signals from adjacent sampling points. This results in increased background signal, broadened axial response, and decreased measurement accuracy. Although biaxial chromatic aberration linear confocal imaging structures can reduce crosstalk to some extent by separating the illumination and detection optical paths, they still suffer from limitations in the tilt angle of the measurable surface and decreased dynamic response performance. Therefore, current technology still lacks a system framework that retains the high throughput and large tilt angle adaptability advantages of single-axis structures while simultaneously enhancing axial constraint and improving spatial selectivity in the linear direction. Summary of the Invention

[0004] The purpose of this invention is to provide a single-axis dispersive line confocal measurement system and method based on a spatial bandpass filter structure, which improves the measurement accuracy and stability of the system while retaining the advantages of large tilt angle adaptability and high throughput.

[0005] To achieve the above objectives, the present invention employs the following technical solution: A single-axis dispersive line confocal measurement system based on a spatial bandpass filter structure includes an illumination optical path and a detection optical path. The illumination optical path includes a white light source, a slit, a first collimating lens group, a beam splitter, a spatial bandpass filter, and a chromatic aberration objective. The broadband light emitted by the white light source is shaped into a linear beam after passing through the slit. The linear beam is collimated by the collimating lens and transmitted to the beam splitter. It is then guided by the spatial bandpass filter to the chromatic aberration objective. After being dispersed and focused by the chromatic aberration objective, it illuminates the surface of the object under test, forming a chromatic aberration distribution with different wavelengths corresponding to different focal positions along the optical axis. The detection optical path includes a second collimating lens group, an inverse slit, a third collimating lens group, a reflection grating, an imaging mirror group, and a CMOS detector. The returned light signal from the beam splitter is collected by the chromatic aberration objective lens and then spatially filtered sequentially through the second collimating lens group and the inverse slit. The light signal filtered by the inverse slit is converged by the third collimating lens group and transmitted to the reflection grating. The reflection grating performs spectral dispersion expansion on the light signal, and after passing through the imaging mirror group, it is acquired and recorded by the CMOS detector.

[0006] Preferably, the high-temperature resistant quartz glass with inverted slits serves as the device substrate, and a light-shielding film layer is deposited on its surface, including two light-transmitting areas symmetrically arranged along the linear direction, with a central blocking gap between the two light-transmitting areas.

[0007] Preferably, the spatial bandpass filter adopts a dual-window bandpass structure symmetrically arranged along the linear direction, with each bandpass window respectively disposed in the collimating optical path region between the beam splitter and the chromatic lens; the spatial bandpass filter is used to apply bandpass constraint to the system optical field and enhance the spatial selectivity in the linear direction.

[0008] Preferably, the spatial bandpass filter works in conjunction with the inverse slit to suppress signal crosstalk between adjacent sampling points and reduce the interference of diffuse reflection component fluctuations on the detection signal.

[0009] Preferably, the beam splitter is used to direct the illumination light to the surface of the object being measured and to guide the return light into the detection optical path containing the reverse slit.

[0010] Preferably, the spectral signal acquired by the CMOS detector is subjected to peak wavelength extraction and wavelength demodulation to obtain the height information of the surface of the object being measured.

[0011] A method for measuring uniaxial dispersive line confocality based on a spatial bandpass filter structure includes the following steps: Broadband light emitted from a white light source is shaped into a linear beam through a slit, collimated, and then focused by a chromatic aberration objective lens onto the surface of the object being measured. The light signal reflected from the surface of the object under test is collected by a chromatic aberration objective lens and spatially filtered through an inverse slit. The inverse slit introduces a central blockage in the main lobe region of the axial response, reshaping the echo response into an inverse Gaussian distribution. The optical signal, after being filtered by the inverse slit, is converged by the third collimating lens group, its spectrum is expanded by the reflection grating, and then acquired by the CMOS detector. The acquired spectral signals are demodulated to extract characteristic wavelengths, and the height information of the surface of the object under test is obtained based on the calibration relationship between wavelength and axial displacement.

[0012] Preferably, the demodulation processing of the acquired spectral signal, extraction of characteristic wavelengths, and obtaining the height information of the surface of the object under test based on the calibration relationship between wavelength and axial displacement are carried out in the following manner: CMOS detectors acquire two-dimensional spectral images containing spatial and spectral information. The spectral pixels of the two-dimensional spectral image are converted into the reflectance spectra corresponding to each position on the measurement line; The reflectance spectrum is analyzed to extract the characteristic wavelengths at each spatial location; Based on the pre-calibrated wavelength-axial displacement relationship, the characteristic wavelength is converted into a height value corresponding to the spatial position to obtain a single height profile; The three-dimensional shape of the measured surface is reconstructed by scanning the object and stitching together the height profiles obtained from different scanning positions.

[0013] Preferred methods for extracting characteristic wavelengths at each spatial location include peak search, centroid calculation, or curve fitting.

[0014] Preferably, the process of establishing the wavelength-axial displacement calibration relationship is as follows: a high-precision displacement stage is used to drive the standard reflecting surface to move along the optical axis, and the characteristic wavelengths corresponding to different known axial positions are recorded, thereby establishing a mapping function between wavelength and axial displacement.

[0015] The advantages of this invention are as follows: This method reconstructs the spatial filter chain of a single-axis chromatic aberration confocal imaging system by synergistically introducing an inverse slit and a spatial bandpass filter structure. While retaining the advantages of the single-axis structure in adapting to large tilt angles and high-throughput line scanning, this method can effectively suppress spatial crosstalk between adjacent sampling points in the line direction, reduce the interference of diffuse reflection fluctuations on the detection signal, and reshape the diffusion response of the system detection points into an inverse Gaussian intensity distribution with a smaller full width at half maximum (FWHM), thereby improving the system's signal-to-noise ratio, axial resolution, and anti-interference stability. Attached Figure Description

[0016] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0017] Figure 1 This is a schematic diagram of the system structure of the present invention.

[0018] Figure 2 This is a schematic diagram of the method flow of the present invention.

[0019] Figure 3 This is a schematic diagram of a space bandpass filter structure.

[0020] Figure 4 This is a schematic diagram of the inverted slit structure.

[0021] In the figure, 1 is a white light source, 2 is a slit, 3 is the first collimating lens group, 4 is a beam splitter, 5 is a spatial bandpass filter, 6 is a chromatic aberration lens, 7 is the surface of the object being measured, 8 is the second collimating lens group, 9 is the reverse slit, 10 is the third collimating lens group, 11 is a reflection grating, 12 is an imaging mirror group, and 13 is a CMOS detector. Detailed Implementation

[0022] 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 embodiments of the present invention, and not all embodiments. 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.

[0023] Example 1 Single-axis dispersive line confocal measurement systems have significant limitations in axial selectivity: their large full width at half maximum (FWHM) and insufficient energy attenuation slope in the defocus region make it difficult to effectively suppress diffuse reflection signals and sidelobe energy, which subsequently accumulate as background at the detector. Furthermore, while single-axis dispersive line confocal measurement systems provide a linear field of view, they also weaken spatial selectivity along the linear direction. These two effects spatially superimpose, making crosstalk between echoes from adjacent sampling locations more likely during detection, ultimately resulting in a decreased signal-to-noise ratio and increased axial inversion error.

[0024] Therefore, if we wish to further improve measurement accuracy and stability while retaining the structural advantages of a single-axis dispersive line confocal measurement system—namely, a larger measurable tilt angle range and high-throughput line scanning capability—relying solely on the existing spatial filtering link is insufficient. System optimization must revolve around two dimensions: first, enhancing axial constraint capabilities to improve defocus suppression; and second, improving spatial selectivity in the line direction to suppress crosstalk.

[0025] To address the aforementioned requirements, this paper restructures the detection channel of a single-axis dispersive line confocal measurement system, using the spatial filtering link as the core design variable. Figure 2 As shown. The proposed scheme integrates the inverse slit with a spatial bandpass filter: on the one hand, the inverse slit introduces controllable central blocking in the main lobe region of the axial response, reshaping the echo response from the traditional Gaussian distribution to an inverse Gaussian distribution, thereby enhancing the system's axial discrimination and feature localization capabilities; on the other hand, the common-path constraint provided by the SBF enhances the spatial selectivity along the line direction, effectively suppressing crosstalk between adjacent sampling points and reducing the interference caused by diffuse reflection component fluctuations on the detection signal. Figure 1As shown, a single-axis chromatic aberration line confocal imaging system based on an inverse slit and a spatial bandpass filter forms a measurement system that combines large tilt angle adaptability, high throughput and low crosstalk characteristics, thereby effectively reducing signal aliasing between adjacent sampling points and effectively improving the system's signal-to-noise ratio, measurement accuracy and stability.

[0026] Includes the illumination optical path and the detection optical path; The illumination optical path includes a white light source 1, a slit 2, a first collimating lens group 3, a beam splitter 4, and a chromatic aberration objective lens 6. The broadband light emitted by the white light source 1 is shaped into a linear beam after passing through the slit 2. The linear beam is collimated by the collimating lens 3 and then transmitted to the beam splitter 4. It is then guided by the spatial bandpass filter 5 to the chromatic aberration objective lens 6. After being dispersed and focused by the chromatic aberration objective lens 6, it illuminates the surface 7 of the object under test, forming a chromatic aberration distribution with different wavelengths corresponding to different focal positions in the optical axis direction, so as to achieve linear scanning illumination of the surface of the object under test.

[0027] The detection optical path includes a second collimating lens group 8, an inverse slit 9, a third collimating lens group 10, a reflection grating 11, an imaging mirror group 12, and a CMOS detector 13. The returned light signal from the beam splitter 4 is collected by the chromatic aberration objective lens 6 and then spatially filtered sequentially through the second collimating lens group 8 and the inverse slit 9. The inverse slit 9 works in conjunction with the spatial bandpass filter 5 in the illumination optical path to enhance the axial selectivity of the system and improve the spatial constraint capability in the linear direction. The light signal filtered by the inverse slit 9 is converged by the third collimating lens group 10 and transmitted to the reflection grating 11. The reflection grating 11 performs spectral dispersion expansion on the light signal, and after passing through the imaging mirror group 12, it is acquired and recorded by the CMOS detector 13.

[0028] By demodulating the acquired spectral signals, the height information of the surface of the object under test is obtained, thereby realizing the imaging measurement of the surface morphology.

[0029] As a refinement of the above embodiment, the broadband light emitted by the white light source 1 is shaped into a linear beam after being shaped by the slit 2.

[0030] The reverse slit 9 is configured in conjunction with the third collimating lens group 10 to perform linear shaping and collimating transmission of broadband light, thereby improving the directional consistency and illumination uniformity of the illumination beam.

[0031] As a refinement of the above embodiments, such as Figure 4As shown, the inverse slit 9 uses high-temperature resistant quartz glass with good thermal stability, low coefficient of thermal expansion, and high optical transmittance as the device substrate, and a light-shielding film is deposited on its surface. Through photolithography processes such as coating, exposure, development, and etching, light-transmitting and blocking areas with predetermined sizes and spatial distributions are formed. By precisely designing the width of the light-transmitting window (100µm) and the central blocking size (20µm), the light field distribution passing through the device can be selectively modulated. After processing, the photolithographic device and the spatial bandpass filter 5 are coaxially assembled at predetermined positions, so that they match each other in spatial position and light transmission direction, together forming a composite spatial filter structure.

[0032] The inverse slit 9 includes two light-transmitting regions symmetrically arranged along the linear direction, with a central blocking gap between the two light-transmitting regions. By introducing a central blocking gap in the main lobe region of the system's axial response, the inverse slit 9 can reshape the energy distribution of the returned light field, transforming the system's returned response from a traditional Gaussian distribution to an inverse Gaussian distribution. This enhances the system's axial discrimination and feature localization capabilities, and helps reduce the full width at half maximum (FWHM) of the axial response, thereby improving the system's axial resolution.

[0033] As a refinement of the above embodiments, such as Figure 4 As shown, the spatial bandpass filter 5 adopts a dual-window bandpass structure symmetrically arranged along the linear direction. Each bandpass window is respectively set in the collimated optical path region between the 4 beam splitting elements and the 6 chromatic aberration lenses, and has a preset bandwidth (3.25 mm). The spatial bandpass filter 5 is used to apply bandpass constraint to the system optical field, enhance the spatial selectivity in the linear direction, and effectively separate the discrete diffuse reflection components from adjacent sampling positions, thereby reducing signal aliasing and background accumulation, and improving the signal-to-noise ratio and measurement stability of the detection signal.

[0034] The spatial bandpass filter 5 works in conjunction with the inverse slit 9 to suppress signal crosstalk between adjacent sampling points and reduce the interference of diffuse reflection component fluctuations on the detection signal. The inverse slit 9 and the spatial bandpass filter 5 are sequentially arranged on the return light propagation path.

[0035] As a refinement of the above embodiment, the beam splitter 4 is used to guide the illumination light to the surface 7 of the object under test and to guide the return light into the detection optical path including the reverse slit 9.

[0036] The spectral signal acquired by the CMOS detector 13 is processed by peak wavelength extraction and wavelength demodulation to obtain the height information of the surface 7 of the object under test.

[0037] It should be noted that: To quantitatively characterize the improvement in the system's axial response performance caused by the above reconstruction, the improved axial response function of the system is further derived under the assumption of a uniform pupil function: First, define the rectangle function as follows: , in, For rectangular window functions, The spatial coordinates of the rectangular window function. This represents the full width of the rectangular window.

[0038] A spatial bandpass filter is introduced into the illumination optical path to selectively modulate the spatial spectrum of the incident illumination field. This method can enhance the contribution of the effective signal near the focal plane while achieving coaxial incidence, thereby improving the system's measurement stability, anti-interference capability, and axial resolution.

[0039] like Figure 2 As shown, the spatial bandpass filter is designed as a symmetrical dual bandpass window (its center is located at...). The width of a single window is The corresponding equivalent pupil function can be written as: , in, Represents the original pupil function. Let be the coordinates along the window arrangement direction within the pupil plane where the spatial bandpass filter is located. To and Orthogonal pupil plane coordinates, The width of a single bandpass window. This represents the primitive pupil function. The entrance pupil diameter is 10 mm, where... It is 3.25mm. It is 1.35mm.

[0040] right Performing a one-dimensional Fourier transform, we obtain: , in, This represents the equivalent pupil function in the illumination optical path. It is the singer function, which is often used in Fourier optics to describe the frequency domain distribution of rectangular aperture, slit, or window functions after Fourier transform. This represents the one-dimensional Fourier transform operator. Indicates and Conjugate spatial frequency variables, For the effective focal length, The wavelength of light is [wavelength]. The inverse slit consists of two [slits] with a width of [width]. It consists of a transmission area, with a width of [missing information]. The center gap is separated.

[0041] Similarly, the pupil function of the inverse slit is expressed as: , in, This represents the equivalent pupil function in the detection optical path. This is the width of the central gap of the reverse slit. It is 20um. It is 100um.

[0042] An inverse slit filter structure is incorporated into the measurement optical path to spatially filter and constrain the measurement light field returned from the measured surface, enabling the probe channel to selectively respond to specific spatial regions or specific spatial frequency components. The echo signal filtered by the inverse slit filter can reduce the influence of off-focal surface scattered light, background stray light, and lateral neighborhood crosstalk on the spectral response, thereby improving the stability and high inversion accuracy of spectral peak extraction in dispersive line confocal measurements.

[0043] According to confocal imaging theory, in the coordinate system of a uniaxial dispersive line confocal probe... In the system, the point spread function This can be expressed as the product of the point spread functions of the illumination and detection optical paths. Let... and Let the point spread functions of the illumination and detection optical paths be represented respectively, then we have: , in, It is the working wavelength of light. These are the coordinates of the probe's own coordinate system.

[0044] The point spread function of the illumination and detection optical paths is derived in detail below: , in, This represents the axial defocusing amount of the observation point relative to the ideal focal plane. The imaginary unit, Indicates the effective focal length of the optical system. This represents the equivalent pupil function in the illumination optical path, which is the illumination end aperture function formed after introducing the spatial bandpass filter. This represents the equivalent pupil function in the detection optical path, which is the detection end aperture function formed after adding the inverse slit filter structure.

[0045] The integral in the formula represents the superposition of the light field across the entire pupil plane. The light field at each pupil plane position carries certain phase information and coherently superimposes in the focal region, ultimately forming a complex amplitude distribution near the focal point. This complex amplitude distribution is the point spread function.

[0046] in, This is the axial defocus phase factor. It reflects the different optical path differences that light rays at different pupil positions will produce when the observation point deviates from the ideal focal plane. It is the transverse spatial phase factor. It describes the pupil plane coordinates. Horizontal coordinates of the focal area The Fourier transform relationship between them.

[0047] This indicates that the final confocal response depends not only on the focusing characteristics of the illumination field but also on the spatial filtering selectivity of the detection optical path. Through analysis of... and By designing the system, the spatial frequency response of both the illumination and detection ends can be controlled simultaneously, thereby improving the axial selectivity of the system, suppressing off-focal stray light, and enhancing the stability of spectral peak extraction.

[0048] Therefore, under the assumption of a uniform pupil function, the axial response function of the entire system can be expressed as: , in, Indicates the axial position of the system and wavelength The response intensity or response amplitude at the specified values; The point spread function of the illumination light path describes the spatial distribution of the illumination light field in the focal region; To detect the point spread function of the optical path, we describe the receiver selectivity of the detection channel for the optical field in the focal region.

[0049] The spatial bandpass filter alters the point spread function of the illumination path, while the inverse slit filter alters the point spread function of the detection path. Both together determine the system's confocal response. By integrating their product laterally, the response distribution of the system at different axial positions and wavelengths can be obtained. Since different wavelengths in a dispersive confocal system correspond to different axial focusing positions, when the measured surface is near the optimal focal plane for a certain wavelength, the response at that wavelength... The peak value is obtained. By extracting the wavelength corresponding to the peak response, the axial height can be inverted.

[0050] Example 2 like Figure 2 As shown, a method for measuring uniaxial dispersion lines confocally based on a spatial bandpass filter structure includes the following steps: S1: The broadband light emitted by the white light source 1 is shaped into a linear beam by the slit 2, and after collimation and spatial bandpass filtering, it is dispersed and focused by the chromatic aberration objective 6 onto the surface 7 of the object under test. S2: The light signal reflected from the surface 7 of the object under test is collected by the chromatic aberration objective lens 6 and spatially filtered through the inverse slit 9. The inverse slit 9 introduces a central blockage in the main lobe region of the axial response, reshaping the echo response into an inverse Gaussian distribution. S3: The light signal filtered by the inverse slit 9 is converged by the third collimating lens group 10, the spectrum is expanded by the reflection grating 11, and the light is collected by the CMOS detector 13. S4: Demodulate the acquired spectral signal, extract the characteristic wavelength, and obtain the height information of the surface of the object under test based on the calibration relationship between wavelength and axial displacement.

[0051] As a refinement of the above embodiments, step S4 specifically includes: S401: CMOS detector (13) acquires two-dimensional spectral images containing spatial and spectral information.

[0052] The continuous spectrum emitted by the broadband light source is shaped into a linear beam by a slit, then converted into approximately parallel light by a collimating lens, and finally guided into the chromatic aberration objective 6 by a beam splitter. The chromatic aberration objective 6 exhibits a significant and controllable axial chromatic aberration; different wavelengths of light have different effective focal lengths after passing through the chromatic aberration objective, thus focusing at different axial positions along the optical axis. Let the incident light wavelength be... The corresponding axial focal position is Then a definite mapping relationship can be established between the two: , in, This represents the wavelength-axial focal position mapping function of the chromatic aberration objective. Within the effective measurement range of the system, this mapping relationship typically remains monotonic, meaning that each axial position corresponds to a specific wavelength, and each wavelength also corresponds to a definite focal position. Thus, after broadband light passes through the chromatic aberration objective 6, it forms a continuously distributed sequence of spectral focal points along the optical axis, achieving wavelength encoding of the axial position.

[0053] On the two-dimensional CMOS detector 13, one direction is used to record the spatial position on the measurement line, and the other direction is used to record the spectral information after grating expansion. Let the coordinates of the measurement line direction be... The pixel coordinates in the spectral direction of the detector are Then the two-dimensional spectral image acquired by the camera can be represented as: in, This represents the light intensity at different spatial locations and spectral pixels. Represents the pixel coordinates of the detector's spectral direction. The corresponding actual wavelength, This represents the pixel-wavelength conversion relationship obtained through spectral calibration.

[0054] S402: Convert the spectral pixels of the two-dimensional spectral image into the reflectance spectra corresponding to each position on the measurement line.

[0055] Using the calibration relationships in S401, the spectral pixel coordinates on the detector can be converted into actual wavelengths, thereby obtaining the reflectance spectra corresponding to each position on the measurement line. .

[0056] S403: Analyze the reflection spectrum and extract the characteristic wavelength at each spatial location.

[0057] For any position on the measurement line, the corresponding light intensity distribution is extracted along the spectral direction of the detector, and its characteristic wavelength is determined using methods such as peak search, centroid calculation, or curve fitting. For traditional uniaxial dispersive line confocal systems, the position of the maximum response in the reflection spectrum is usually taken as the focusing wavelength. , in, Indicates the spatial position of the measurement line The focusing feature wavelength extracted at that location, Indicates the wavelength variable Increase the intensity of the reflected spectrum The wavelength corresponding to the attainment of the maximum value.

[0058] S404: Based on the pre-calibrated wavelength-axial displacement relationship, the characteristic wavelength is converted into a height value corresponding to the spatial position to obtain a single height profile.

[0059] The characteristic wavelength reflects the axial height at the corresponding measurement position, but cannot be directly used as the height measurement result. During system calibration, a high-precision displacement stage is used to drive the standard reflecting surface to move along the optical axis, recording the characteristic wavelengths corresponding to different known axial positions, thereby establishing a calibration relationship between wavelength and axial displacement. During actual measurement, the extracted characteristic wavelengths are substituted into this calibration relationship to obtain the height distribution along the measurement line. , in, This represents the axial height value at this spatial location obtained by substituting the characteristic wavelength into the calibration function. Since the area array camera can simultaneously record the spectral information of multiple spatial locations along the measurement line, the height profile of the entire measurement line can be obtained in parallel with a single exposure, resulting in higher data acquisition efficiency than point-based chromatic aberration confocal measurement.

[0060] S405: By scanning the object under test and stitching together the height profiles obtained from different scanning positions, the three-dimensional shape of the surface under test is reconstructed.

[0061] After obtaining a single height profile, the measured object or measurement system is controlled to perform a relative scan along a direction perpendicular to the measurement line, and the line profiles obtained from different scanning positions are stitched together in spatial order to reconstruct the three-dimensional morphology of the measured surface. Thus, the system completes the entire process from two-dimensional spectral image and feature wavelength extraction to line profile measurement and three-dimensional morphology reconstruction.

[0062] To experimentally verify the effectiveness of the proposed filtering link in improving the performance of the uniaxial dispersion line confocal measurement system, a test platform for the uniaxial dispersion line confocal measurement system was built. Its main components and key parameters are summarized in Table 1. This platform achieved an axial measurement range of 2mm under a field of view of 3.5mm.

[0063] Table 1 Parameter Table This disclosure also provides a single-axis dispersion line confocal measurement device based on a spatial bandpass filter structure, including a processor and a memory. Optionally, the device may further include a communication interface and a bus. The processor, communication interface, and memory can communicate with each other via the bus. The communication interface can be used for information transmission. The processor can call logical instructions in the memory to execute the single-axis dispersion line confocal measurement method based on the spatial bandpass filter structure described in the above embodiments.

[0064] Furthermore, the logical instructions in the aforementioned memory can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium.

[0065] Memory, as a computer-readable storage medium, can be used to store software programs and computer-executable programs, such as the program instructions / modules corresponding to the methods in the embodiments of this disclosure. The processor executes the program instructions / modules stored in the memory to perform functional applications and data processing, thereby realizing the single-axis dispersion line confocal measurement method based on the spatial bandpass filter structure in the above embodiments.

[0066] The memory may include a program storage area and a data storage area. The program storage area may store the operating system and applications required for at least one function; the data storage area may store data created based on the use of the terminal device. Furthermore, the memory may include high-speed random access memory and may also include non-volatile memory.

[0067] This disclosure provides a computer-readable storage medium storing computer-executable instructions configured to perform the above-described single-axis dispersion line confocal measurement method based on a spatial bandpass filter structure.

[0068] The aforementioned computer-readable storage medium may be a transient computer-readable storage medium or a non-transitory computer-readable storage medium.

[0069] The technical solutions of this disclosure can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes one or more instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the method described in this disclosure. The aforementioned storage medium can be a non-transitory storage medium, including: a USB flash drive, a portable hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk, and other media capable of storing program code. It can also be a transient storage medium.

[0070] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A single-axis dispersive line confocal measurement system based on a spatial bandpass filter structure, comprising an illumination optical path and a detection optical path, characterized in that: The illumination optical path includes a white light source (1), a slit (2), a first collimating lens group (3), a beam splitter (4), a spatial bandpass filter (5), and a chromatic aberration objective (6). The broadband light emitted by the white light source (1) is shaped into a linear beam after passing through the slit (2). The linear beam is collimated by the collimating lens (3) and transmitted to the beam splitter (4). It is then guided by the spatial bandpass filter (5) to the chromatic aberration objective (6). After being dispersed and focused by the chromatic aberration objective (6), it illuminates the surface (7) of the object under test, forming a chromatic aberration distribution with different wavelengths corresponding to different focal positions in the optical axis direction. The detection optical path includes a second collimating lens group (8), an inverse slit (9), a third collimating lens group (10), a reflection grating (11), an imaging mirror group (12), and a CMOS detector (13). The return light signal from the beam splitter (4) is collected by the chromatic aberration objective (6) and then spatially filtered by the second collimating lens group (8) and the inverse slit (9). The light signal filtered by the inverse slit (9) is converged by the third collimating lens group (10) and transmitted to the reflection grating (11). The reflection grating (11) performs spectral dispersion expansion on the light signal, and after passing through the imaging mirror group (12), it is collected and recorded by the CMOS detector (13).

2. The single-axis dispersive line confocal measurement system based on a spatial bandpass filter structure according to claim 1, characterized in that, The reverse slit (9) is a high-temperature resistant quartz glass used as the device substrate, with a light-shielding film layer deposited on its surface, including two light-transmitting areas symmetrically arranged along the line direction, and a central blocking gap between the two light-transmitting areas.

3. The single-axis dispersive line confocal measurement system based on a spatial bandpass filter structure according to claim 1, characterized in that, The spatial bandpass filter (5) adopts a dual-window bandpass structure symmetrically arranged along the linear direction. Each bandpass window is respectively set in the collimated optical path region between the 4 beam splitter and the 6 chromatic aberration lens. The spatial bandpass filter (5) is used to apply bandpass constraint to the system optical field and enhance the spatial selectivity in the linear direction.

4. The single-axis dispersive line confocal measurement system based on a spatial bandpass filter structure according to claim 1, characterized in that, The spatial bandpass filter (5) works in conjunction with the inverse slit (9) to suppress signal crosstalk between adjacent sampling points and reduce the interference of diffuse reflection component fluctuations on the detection signal.

5. The single-axis dispersive line confocal measurement system based on a spatial bandpass filter structure according to claim 1, characterized in that, The beam splitter (4) is used to direct the illumination light to the surface (7) of the object under test and to guide the return light into the detection optical path containing the reverse slit (9).

6. The single-axis dispersive line confocal measurement system based on a spatial bandpass filter structure according to claim 1, characterized in that, The spectral signal collected by the CMOS detector (13) is extracted by peak wavelength and demodulated by wavelength to obtain the height information of the surface (7) of the object under test.

7. A method for measuring uniaxial dispersive lines based on a spatial bandpass filter structure using the system described in any one of claims 1-6, characterized in that, Includes the following steps: The broadband light emitted by the white light source (1) is shaped into a linear beam through the slit (2), and after collimation and spatial bandpass filtering, it is dispersed and focused by the chromatic aberration objective (6) onto the surface (7) of the object under test. The light signal reflected from the surface (7) of the object under test is collected by the chromatic aberration objective (6) and spatially filtered through the inverse slit (9). The inverse slit (9) introduces a central blockage in the main lobe region of the axial response, reshaping the echo response into an inverse Gaussian distribution. The light signal filtered by the inverse slit (9) is converged by the third collimating lens group (10), the spectrum is expanded by the reflection grating (11), and the light is collected by the CMOS detector (13). The acquired spectral signals are demodulated to extract characteristic wavelengths, and the height information of the surface of the object under test is obtained based on the calibration relationship between wavelength and axial displacement.

8. The method for measuring uniaxial dispersion lines confocally based on a spatial bandpass filter structure according to claim 7, characterized in that, The acquired spectral signal is demodulated to extract characteristic wavelengths. The height information of the surface of the object under test is obtained based on the calibration relationship between wavelength and axial displacement. The specific method is as follows: The CMOS detector (13) acquires two-dimensional spectral images containing spatial and spectral information; The spectral pixels of the two-dimensional spectral image are converted into the reflectance spectra corresponding to each position on the measurement line; The reflectance spectrum is analyzed to extract the characteristic wavelengths at each spatial location; Based on the pre-calibrated wavelength-axial displacement relationship, the characteristic wavelength is converted into a height value corresponding to the spatial position to obtain a single height profile; The three-dimensional shape of the measured surface is reconstructed by scanning the object and stitching together the height profiles obtained from different scanning positions.

9. The method for measuring uniaxial dispersion lines confocally based on a spatial bandpass filter structure according to claim 8, characterized in that, Methods for extracting characteristic wavelengths at each spatial location include peak search, centroid calculation, or curve fitting.

10. The method for measuring uniaxial dispersion lines confocally based on a spatial bandpass filter structure according to claim 7, characterized in that, The process of establishing the wavelength-axial displacement calibration relationship is as follows: a high-precision displacement stage is used to drive the standard reflecting surface to move along the optical axis, and the characteristic wavelengths corresponding to different known axial positions are recorded, thereby establishing a mapping function between wavelength and axial displacement.

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