A measuring device and a measuring method based on coupling of spectral confocal and laser interference

Abstract

This invention relates to a measurement device and method based on spectral confocal and laser interferometric coupling. The measurement device includes: a spectral confocal measurement unit, a control unit connected to the spectral confocal measurement unit, and a data processing unit connected to the control unit. The spectral confocal measurement unit includes: an entrance aperture structure, a first lens, a beam combiner, a second lens, and a movable mirror. The entrance aperture structure, the first lens, the beam combiner, the second lens, and the movable mirror are arranged sequentially along the same spectral confocal principal optical axis. The control unit is connected to both the entrance aperture structure and the beam combiner. The control unit provides focused white light to the spectral confocal measurement unit based on the entrance aperture structure and collects the returned spectral confocal data to obtain a displacement measurement value of the movable mirror. Furthermore, the control unit provides interferometric laser light to the spectral confocal measurement unit based on the beam combiner and collects the returned interferometric laser data to obtain an axial displacement of the movable mirror.

Description

Technical Field

[0001] This invention relates to the field of optical technology, and in particular to a measurement device and method based on spectral confocal coupling and laser interferometry. Background Technology

[0002] In modern society, with the continuous advancement of science and technology, spectral analysis technology has become a crucial measurement tool in high-tech industries. Confocal spectroscopy and laser interferometry, as two important branches of spectral analysis, each possess unique advantages and application areas. In recent years, with in-depth research and technological integration, confocal spectroscopy and laser interferometry have shown significant importance and broad application prospects in high-performance, digital, and intelligent industrial production and detection. Extensive research has been conducted in many countries, including the United States, the United Kingdom, and France. Spectral measurements and research using confocal spectroscopy and laser interferometry are of great significance to laser detection. Therefore, it is urgent to find a method to break through this technological barrier.

[0003] Spectral confocal technology utilizes the physical phenomenon that a single thin lens produces different focal lengths for different monochromatic lights. Based on confocal technology, it uses special lenses to focus light of different wavelengths at different axial positions, essentially encoding the wavelengths of points on the optical axis. By analyzing the focused wavelength of the light reflected from the surface under test, the precise distance from the object to the lens can be calculated based on a pre-calibrated response curve. Therefore, it has significant advantages such as high speed, high accuracy, and strong adaptability. With the advancement of technology, spectral confocal technology has been developed into various types of sensors, among which point spectral confocal sensors are the most widely used.

[0004] Laser interferometry is a measurement method that utilizes the interference phenomenon of light waves. Two light waves with the same frequency, phase, and direction of vibration intersect in space after traveling different optical paths. When the optical path difference is an integer multiple of the wavelength, the wave crests meet and superimpose, resulting in enhanced brightness and bright interference fringes. When the optical path difference is an odd multiple of half the wavelength, the wave crests meet and troughs, resulting in diminished brightness and dark interference fringes. This phenomenon is called optical wave interference. Light emitted from the light source is split into two paths by a beam splitter. One path passes through the beam splitter and is directed to a movable mirror M1, while the other path is reflected by the beam splitter to a fixed mirror M2, and then reflected back from both mirrors M1 and M2, respectively, before being superimposed on a receiving screen. Whenever the movable mirror M1 moves by half a wavelength, the interference fringes on the receiving screen change from dark to bright or from bright to dark. By calculating the number of these changes in brightness, the amount of movement of the movable mirror M1 can be determined.

[0005] While existing technologies offer advantages such as high precision and adaptability, they also suffer from limitations including limited measurement range, decreased accuracy and linearity with increased range, and a lack of absolute displacement reference. Laser interferometry, on the other hand, offers long-range displacement measurement capabilities but suffers from difficulties in optical path alignment, poor anti-interference capabilities, inability to locate minute spot measurement points, and difficulty in detecting surface morphology. Neither technology, used alone, can simultaneously meet the comprehensive measurement requirements of long range, high precision, high stability, small spot size, and anti-interference. Furthermore, simple discrete combinations result in problems such as misaligned measurement points, optical path decoupling, and data fusion issues, leading to large measurement errors, system complexity, and difficulty in achieving high-precision collaborative measurement. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a measurement device and method based on the coupling of spectral confocal and laser interferometry, which solves the technical drawbacks of the prior art, such as short spectral confocal range, poor stability of laser interferometry, inability of dual systems to be coaxially coupled for measurement, and inability to effectively fuse data.

[0007] To achieve the above-mentioned objectives, the present invention provides a measurement device based on spectral confocal and laser interferometry coupling, comprising: a spectral confocal measurement unit, a control unit connected to the spectral confocal measurement unit, and a data processing unit connected to the control unit;

[0008] The spectral confocal measurement unit includes: an entrance aperture structure, a first lens, a beam combiner, a second lens, and a movable reflector; The entrance aperture structure, the first lens, the beam combiner, the second lens, and the movable mirror are arranged sequentially along the same spectral confocal principal optical axis; The control unit is connected to the entrance aperture structure and the beam combiner, respectively; wherein, the control unit provides focused white light to the spectral confocal measurement unit based on the entrance aperture structure and collects the returned spectral confocal data to obtain the axial displacement measurement value of the movable mirror along the principal optical axis of the spectral confocal axis; and, the control unit provides interferometric laser light to the spectral confocal measurement unit based on the beam combiner and collects the returned interferometric laser data to obtain the axial displacement of the movable mirror along the same principal optical axis of the spectral confocal axis. The data processing unit uses interferometric laser data as the long-range absolute displacement reference and spectral confocal data as the displacement correction amount to output the compensated long-range axial displacement measurement results.

[0009] According to one aspect of the present invention, the beam combiner is a parallel planar plate structure, wherein a white light broadband anti-reflection film is coated on the side of the beam combiner opposite to the first lens, and a laser high reflectivity film is coated on the other side of the beam combiner.

[0010] According to one aspect of the invention, the control unit includes: a spectral confocal controller and a laser interferometer; The spectral confocal controller is connected to the entrance aperture of the entrance aperture structure via an optical fiber; The laser interference device and the beam combiner are on the same optical path.

[0011] According to one aspect of the present invention, the spectral confocal controller includes: a white light source and a spectrometer; The output end of the white light source and the input end of the spectrometer are both coupled to the same end of the optical fiber. The other end of the optical fiber is connected to the entrance hole of the entrance hole structure through a coaxial coupling connection structure. The white light source is used to provide white light, and the spectrometer is used to receive the returned reflected light signal and obtain spectral confocal data. The laser interference device includes: a laser source, a detector, and a laser interference optical path; The laser source and the detector are respectively opposite to the laser interference optical path, and the beam combiner is connected to the laser interference optical path. The laser source is used to provide interference laser to the beam combiner, and the detector is used to receive the returned interference laser and obtain the interference laser data. The focusing data is obtained based on the peak wavelength of the optical signal; The interference laser data is obtained based on the interference fringe data of the interference laser.

[0012] According to one aspect of the present invention, the laser interference optical path includes: a beam splitter and a reflector; The laser source and the detector are located on the same side of the beam splitter and are both on the input path of the beam splitter. A reference arm is formed by connecting a fixed reflector to one beam-splitting optical path of the beam splitter, and a measurement arm is formed by connecting the other beam-splitting optical path of the beam splitter to the beam combiner. The measuring arm extends along the spectral confocal principal optical axis of the spectral confocal measuring unit.

[0013] According to one aspect of the invention, along the spectral confocal principal optical axis of the spectral confocal measurement unit, the distance L0 between the lower side of the entrance aperture structure and the upper side of the movable mirror is at least 160 mm, and the distance L1 between the beam combiner axis and the upper side of the movable mirror is at least 100 mm.

[0014] To achieve the above-mentioned objective, the present invention provides a measurement method using the aforementioned measuring device, comprising: S1. Fix the sample on the movable mirror and drive the movable mirror to move to the measurement start point and measurement end point of the sample to calibrate the measurement range and obtain the displacement of the measurement start point and measurement end point based on the laser interferometer. S2. Move the movable reflector to the measurement starting point of the sample, and control the movable reflector to move towards the measurement endpoint according to the preset step distance. At each step position, the spectral confocal controller and the laser interferometer synchronously collect spectral confocal data and interference laser data, and send them to the data processing unit. S3. The data processing unit fuses the spectral confocal data and the laser interferometric data, using the interferometric laser data as the long-range absolute displacement reference and the spectral confocal data as the displacement correction amount, and outputs the compensated long-range axial displacement measurement results.

[0015] According to one aspect of the present invention, the spectral confocal data is obtained based on the reflected light signal received by the spectrometer in the spectral confocal controller after decoding processing; wherein the decoding processing step for the reflected light signal includes: The reflected light signal is subjected to noise filtering to remove high-frequency random noise and environmental interference; the noise filtering includes median filtering and mean filtering. The reflected light signals after noise filtering are arranged according to the wavelength dimension to form a continuous spectral intensity distribution curve; The light intensity is normalized on the spectral intensity distribution curve, and the light intensity gradient consistency of each data point on the spectral intensity distribution curve is converted into light intensity gradient consistency weight, thereby eliminating the intensity drift caused by light source fluctuation and optical path loss. The peak wavelength was extracted from the normalized spectral intensity distribution curve using the weighted centroid method. By mapping the peak wavelength to the pre-calibrated wavelength-displacement response curve, the spectral confocal data is obtained and the displacement measurement value is derived.

[0016] According to one aspect of the present invention, in the step of noise filtering of the optical signal, in the step of extracting the peak wavelength using the weighted centroid method from the normalized spectral intensity distribution curve of the light intensity, the formula for calculating the peak wavelength is expressed as follows: x=

[0017] Where x is the centroid position corresponding to the peak wavelength. i For the spectrometer i 1 pixel For the first i Light intensity gradient consistency weights corresponding to each pixel.

[0018] According to one aspect of the invention, the interference laser data is obtained based on interference fringe data of the interference laser received by the laser interference device, for the purpose of obtaining the axial displacement of the movable reflector, wherein the axial displacement is obtained by phase subdivision of the interference fringes, and is expressed as: d =

[0019] in, d This represents the axial displacement of the movable reflector. λ The wavelength of the laser. N This represents the number of effective interference fringes obtained through phase subdivision.

[0020] According to one aspect of the present invention, the invention employs two systems simultaneously for measurement: a spectral confocal controller and a laser interferometer. By utilizing spectral confocal displacement measurement and laser interferometry for length measurement, two sets of results are obtained simultaneously on the sample. Through data fusion via a data processing unit, a more accurate and wider-range value can be calculated. Its outstanding advantages lie in the fact that by fusing the measurement data from two systems and compensating for each other's shortcomings, the invention achieves high precision, long measurement range, and high accuracy.

[0021] According to one aspect of the present invention, the present invention achieves high precision and long measurement range while simultaneously utilizing the fusion of measurement data from two systems to complement each other's strengths.

[0022] According to one aspect of the present invention, this approach effectively achieves coaxial, synchronous, and fusion measurement, while also taking into account numerous advantages such as long measurement range, high precision, high stability, small spot size, and anti-interference.

[0023] According to one aspect of the present invention, the present invention offers high accuracy. It utilizes a spectral confocal controller and a laser interferometer simultaneously as the measurement system, which increases the probability of detecting random errors compared to single-system measurements. This avoids operator errors caused by manual calculations and manual CNC input, thereby improving the accuracy of the measurement. The simultaneous use of spectral confocal and laser interferometry ensures the reliability of the measurement results.

[0024] According to one aspect of the present invention, the invention is highly efficient and has a fast time response. Light travels very fast in air, resulting in less measurement time and enabling high-speed measurement. Attached Figure Description

[0025] Figure 1 This is a schematic diagram illustrating the structure of a measuring device according to one embodiment of the present invention; Figure 2 This is a schematic diagram illustrating the confocal measurement principle of a spectral confocal measurement unit according to an embodiment of the present invention; Figure 3This is a schematic diagram illustrating the connection principle between a laser interferometer and a spectral confocal measurement unit according to an embodiment of the present invention; Figure 4 This is a simplified schematic diagram illustrating the technical specifications of a spectral confocal measurement unit according to one embodiment of the present invention. Detailed Implementation

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0027] In describing embodiments of the present invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer" express orientations or positional relationships based on the orientations or positional relationships shown in the relevant drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limitations on the present invention.

[0028] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The embodiments cannot be described in detail here, but the embodiments of the present invention are not limited to the following embodiments.

[0029] like Figure 1 As shown, according to one embodiment of the present invention, a measurement device based on spectral confocal and laser interferometry coupling includes: a spectral confocal measurement unit 1, a control unit 2 connected to the spectral confocal measurement unit 1, and a data processing unit 3 connected to the control unit 2. In this embodiment, the spectral confocal measurement unit 1 and the control unit 2 integrate a coaxial optical path, so that they share the measurement spot, share the measurement point, and synchronously trigger sampling, thereby ensuring that the spectral confocal data and the laser interferometry data originate from the same location and at the same time, providing a basis for subsequent high-precision data fusion and avoiding measurement errors caused by measurement point offset and time asynchrony.

[0030] In this embodiment, the spectral confocal measurement unit 1 includes: an entrance aperture structure 11, a first lens 12, a beam combiner 13, a second lens 14, and a movable reflector 15; wherein, the entrance aperture structure 11, the first lens 12, the beam combiner 13, the second lens 14, and the movable reflector 15 are located on the same optical path and are arranged sequentially along the same spectral confocal principal optical axis; specifically, along the direction close to the sample being measured, the entrance aperture structure 11, the first lens 12, the beam combiner 13, the second lens 14, and the movable reflector 15 are arranged sequentially along the same optical axis. In this embodiment, to ensure the strict coaxiality of the first lens 12 and the second lens 14, a coaxial synchronous adjustment mechanism can be used to connect the first lens 12 and the second lens 14, enabling the first lens 12 and the second lens 14 to be synchronously and concentrically adjusted in pitch and deflection, ensuring precise relative position and strict alignment of the optical axis. The coaxial synchronous adjustment mechanism includes a side support, with a first adjustment platform and a second adjustment platform respectively installed at the upper and lower ends of the side support. Further, the first adjustment platform includes a first three-dimensional platform and a first deflection adjustment platform. The first deflection adjustment platform is directly nested with the first lens 12, allowing pitch and deflection adjustment of the first lens 12 through a rotation adjustment mechanism. The first deflection adjustment platform can be configured as a coplanar / universal adjustment frame, a cross adjustment ring, or other structures. The first deflection adjustment platform is connected to the first three-dimensional platform, allowing position changes through the three-dimensional translation adjuster of the first three-dimensional platform. Similarly, the structure of the second adjustment platform is identical to that of the first adjustment platform, and will not be described further here. Furthermore, both the first and second adjustment platforms can be operated manually and / or electrically to ensure reliable and flexible adjustment.

[0031] In this embodiment, the first lens 12 and the second lens 14 can be optionally designed as a multi-lens linkage assembly to eliminate single-lens processing errors in the form of an equivalent single lens. This achieves strict coaxiality throughout the entire process from both assembly adjustment and structural compensation aspects, providing a stable structural foundation for coaxial coupling measurement. Of course, when using a multi-lens linkage assembly structure, it can also be fixed by cementing lenses after calibration to ensure structural stability and reliability during long-term use.

[0032] In this embodiment, the control unit 2 is connected to the entrance aperture structure 11 and the beam combiner 13, respectively. The control unit 2 provides focused white light to the spectral confocal measurement unit 1 based on the entrance aperture structure 11 and collects the returned spectral confocal data to determine the axial displacement measurement value of the movable mirror 15 along the principal optical axis of the spectral confocal axis. Furthermore, the control unit 2 provides interference laser light to the spectral confocal measurement unit 1 based on the beam combiner 13 and collects the returned interference laser data to obtain the axial displacement of the movable mirror 15 along the same principal optical axis of the spectral confocal axis. Further, the data processing unit 3 uses the interference laser data as a long-range absolute displacement reference and the spectral confocal data as a displacement correction value. By fusing the long-range absolute displacement reference and the displacement correction value, the compensated long-range axial displacement measurement result can be output.

[0033] like Figure 1 As shown, according to one embodiment of the present invention, the beam combiner 13 is a parallel planar plate structure, and the substrate is a low-expansion, high-uniformity optical glass. A white light broadband anti-reflection coating is deposited on the side of the beam combiner 13 opposite to the first lens 12, and a laser high-reflection coating is deposited on the other side of the beam combiner 13. Thus, the beam combiner 13 can achieve a white light transmittance of ≥97% for 400–700 nm and a laser reflectance of ≥99.5% for 632.8 nm. Furthermore, the beam combiner 13 ensures strict co-axiality, co-spot, and co-measurement of the spectral confocality and laser interference with high-precision surface parallelism and a 45° installation angle, significantly reducing optical path loss, improving the signal-to-noise ratio and measurement stability, and providing key optical guarantees for achieving high-precision, long-range, and highly interference-resistant measurements in this application.

[0034] With the above settings, high white light transmission (which is beneficial to the transmission efficiency of spectral confocal signals) and high laser reflection (which reduces optical loss in the interference optical path) are achieved at the beam combiner position, which can further promote a significant improvement in the measurement performance of this scheme.

[0035] In this embodiment, the white light broadband antireflection film can be implemented using a multi-layer structure. For example, it can be configured as three layers from top to bottom: the top layer is a SiO2 layer, the middle layer is TiO2, and the bottom layer is a SiO2 layer or a SiO2-TiO2 mixed layer. Different combinations can be used to optimize the high transmittance of white light, thereby reducing the loss during transmission. This is more beneficial for improving the displacement correction effect of this solution and effectively ensuring the measurement accuracy of this solution.

[0036] like Figure 1As shown, according to one embodiment of the present invention, the control unit 2 includes: a spectral confocal controller 21 and a laser interferometer 22; wherein, the spectral confocal controller 21 is connected to the entrance aperture of the entrance aperture structure 11 based on the optical fiber 4; the laser interferometer 22 and the beam combiner 13 are on the same optical path. In this embodiment, a window is provided on the side of the spectral confocal measurement unit 1, so that the laser interferometer 22 can be directly connected to the spectral confocal measurement unit 1. Specifically, the window is opposite to the beam combiner 13, so that the laser interferometer 22 and the beam combiner 13 are on the same optical path.

[0037] like Figure 1 As shown, according to one embodiment of the present invention, the spectral confocal controller 21 includes a white light source and a spectrometer. In this embodiment, the output end of the white light source and the input end of the spectrometer are both coupled to the same end of the optical fiber 4. The other end of the optical fiber 4 is connected to the entrance hole of the entrance hole structure 11 through a coaxial coupling connection structure, thereby realizing that the white light emission and reflected light signal reception are coaxial, co-fiber, and co-hole. With high-precision concentric positioning hole, optical fiber locking structure, coaxial reference end face and integrated incident, the optical fiber light output and the entrance hole achieve the beneficial effects of strict coaxiality, locking and fixation and no eccentricity. In this system, a white light source provides white light, and a spectrometer receives the returned light signal and obtains spectral confocal data. Furthermore, the first lens 12, beam combiner 13, and second lens 14 in the spectral confocal measurement unit 1 converge different wavelengths of light at different focal points. Further, the beam focused on the movable reflector 15 is reflected back to the spectrometer in the spectral confocal controller 21 to perform spectral detection of the wavelength light focused on the surface of the sample, thereby enabling positioning at the corresponding distance. In this embodiment, the spectral confocal data is obtained based on the peak wavelength of the returned reflected light signal. Specifically, the spectral confocal measurement unit 1 can achieve the aforementioned spectral detection based on the physical phenomenon of chromatic aberration lens errors. For different monochromatic lights, each monochromatic light has a different focal length. According to the wavelength of the light, from shortest to longest, their image points are arranged on the optical axis from near to far from the lens. Thus, the corresponding position is determined based on the different focusing positions of different monochromatic lights. (See [link to relevant documentation]). Figure 2 As shown.

[0038] In this embodiment, the laser interferometer 22 includes a laser source, a detector, and a laser interference optical path. The laser source and detector are respectively positioned opposite the laser interference optical path, and a beam combiner 13 is connected to the laser interference optical path. The laser source provides interference laser light to the beam combiner 13, and the detector receives the returned interference laser light and obtains interference laser data. In this embodiment, the interference laser data is obtained based on the interference fringe data of the interference laser. Therefore, the axial displacement of the movable reflector 15 can be calculated based on the obtained interference laser data. The laser interferometer 22 performs measurements based on the characteristics of laser interference phenomena. Specifically, it uses two beams of light, typically splitting one beam into two, which, when superimposed, form an interference pattern. Because the wavelength of visible light is very short, even slight differences in the optical paths of the two beams can be detected, and these differences will produce significant changes in the interference pattern.

[0039] With the above settings, the control unit 2, by adopting the combination of the strengths of the spectral confocal controller 21 and the laser interferometer 22, can conveniently and effectively achieve long range and high precision through data fusion.

[0040] like Figure 3 As shown, according to one embodiment of the present invention, the laser interference optical path includes: a beam splitter 221 and a reflector 222; the laser source and the detector are located on the same side of the beam splitter 221 and are both on the input path of the beam splitter 221; wherein, the reflector 222 is fixedly connected to one beam splitting optical path of the beam splitter 221 to form a reference arm, and the other beam splitting optical path of the beam splitter 221 is connected to the beam combiner 13 to form a measurement arm; the measurement arm extends along the spectral confocal principal optical axis of the spectral confocal measurement unit 1, without polarization changing devices and without parasitic interference. Specifically, a laser source emits a laser beam, which is split into two beams by a beam splitter 221. One beam is reflected to a fixed mirror 222 and then back to the beam splitter 221. The other beam is transmitted to a beam combiner 13 and reflected to a second lens 14 and a movable mirror 15. This beam is then returned to the beam splitter 221, achieving the merging and interference of the two beams. The merged beam is then sent to a detector to interfere with each other in a constructive or destructive manner. In constructive interference, the two beams are in phase, and their peaks reinforce each other, producing bright interference fringes. In destructive interference, the two beams are out of phase, and the peak of one beam is canceled out by the trough of the other beam, forming dark interference fringes.

[0041] With the above-described configuration, the spectral confocal measurement unit 1 and control unit 2 of the present invention have the advantages of simple structure and high reliability. Furthermore, the measurement arm in the laser optical path has no return optical surface except for the sample, and no polarization-changing devices (such as waveplates and polarization beam splitters), achieving the unique advantage of no parasitic interference and synchronous measurement with spectral confocal coaxiality.

[0042] In this embodiment, an adjustable incident position and angle structure can be further arranged at the location of the laser incident beam combiner. This allows for precise adjustment of the laser incident point and incident angle, ensuring that the laser, after being reflected by the beam combiner, is strictly coaxial with the principal optical axis of the spectrum. It also ensures that the laser spot and the white light spot on the measurement surface are completely coincident and concentric. This achieves coaxial coupling of the two optical paths at the spot level, ensuring that the two sets of data are measured at the same measurement point and position, fundamentally eliminating measurement point deviations and providing a true and reliable foundation for data fusion.

[0043] like Figure 4 As shown, according to one embodiment of the present invention, along the spectral confocal principal optical axis of the spectral confocal measurement unit 1, the distance L0 between the lower side of the entrance aperture structure 11 and the upper side of the movable reflector 15 is at least 160 mm, and the distance L1 between the axis of the beam combiner 13 and the upper side of the movable reflector 15 is at least 100 mm (i.e., the measuring arm extends along the spectral confocal principal optical axis and the optical path is greater than or equal to 100 mm). In this embodiment, the area where the beam combiner 13 is located is marked as area B, the area between the beam combiner 13 and the movable reflector 15 is marked as area A, and the area between the beam combiner 13 and the entrance aperture structure 11 is marked as area C. Further, the width of area A is denoted as D, the distance from the axis of the beam combiner 13 to the bottom of area A is denoted as distance L1, and the distance from the bottom of area A to the top of area C is denoted as distance L0.

[0044] In this embodiment, the sample is an uncoated glass surface, and the measurement is performed at a frequency of 5 kHz. In this embodiment, the movable reflector 15 is positioned in region A, so the sample is held in the upper-middle part of region A, and the diameter of the light spot formed on the sample is less than or equal to 5 μm. Furthermore, the diameter of region A is no greater than 40 mm, and the horizontal working distance is less than or equal to 10 mm. The beam combiner 13 is located in the middle region B, and the laser wavelength introduced is 633 nm.

[0045] With the above settings, this solution can provide a sufficiently long measurement optical path, achieving a long-range measurement effect of greater than or equal to 200μm; and effectively improve the linearity of wavelength-displacement mapping, with a linearity error of no more than ±0.5μm; especially in the ±15μm range in the middle of the measurement optical path, it achieves an ultra-high precision of no more than ±0.03μm, and the static measurement standard deviation is no more than 0.02μm.

[0046] In addition, this scheme provides space for the coaxial coupling of spectral confocality and laser interferometry, avoiding optical crosstalk; it improves the mechanical stability and temperature drift resistance of the system, enabling long-term high-precision measurement.

[0047] In addition, this solution supports a large tilt angle sample measurement range of ±30°, making it more applicable.

[0048] With the above configuration, the measurement method combining the spectral confocal measurement unit 1 and the control unit 2 of the present invention has a longer optical path, higher reliability, and higher efficiency. Furthermore, the measurement method combining the spectral confocal measurement unit 1 and the control unit 2 can also be fused using a host computer to achieve corresponding advantages and disadvantages.

[0049] like Figure 1 As shown, according to one embodiment of the present invention, the present invention provides a measurement method using the aforementioned measuring device, comprising: S1. Fix the sample on the movable reflector 15 and drive the movable reflector 15 to move to the measurement start point and measurement end point of the sample to calibrate the measurement range and obtain the displacement of the measurement start point and measurement end point based on the laser interferometer 22. S2. Move the movable reflector 15 to the measurement starting point of the sample, and control the movable reflector 15 to move towards the measurement endpoint according to the preset step distance. At each step position, the spectral confocal controller 21 and the laser interferometer 22 synchronously collect spectral confocal data and interference laser data, and send them to the data processing unit 3. S3. Data processing unit 3 fuses spectral confocal data and laser interferometric data, using the interferometric laser data as the long-range absolute displacement reference and the spectral confocal data as the displacement correction amount, and outputs the compensated long-range axial displacement measurement result.

[0050] According to one embodiment of the present invention, the spectral confocal data is obtained by decoding the reflected light signal received by the spectrometer in the spectral confocal controller 21; in this embodiment, the decoding processing steps for the reflected light signal include: The reflected light signal is subjected to noise filtering to remove high-frequency random noise and environmental interference. The noise filtering includes median filtering and mean filtering. In this embodiment, pulse noise and spike interference are first removed by median filtering, and then random noise is smoothed by mean filtering to obtain the noise-filtered reflected light signal. The reflected light signals after noise filtering are arranged according to the wavelength dimension to form a continuous spectral intensity distribution curve; The light intensity is normalized on the spectral intensity distribution curve, and the light intensity gradient consistency of each data point on the spectral intensity distribution curve is converted into light intensity gradient consistency weight, thereby eliminating the intensity drift caused by light source fluctuation, optical path loss and ambient light interference. The peak wavelength was extracted from the normalized spectral intensity distribution curve using the weighted centroid method. By mapping the peak wavelength to the pre-calibrated wavelength-displacement response curve, the spectral confocal data is obtained and the displacement measurement value is derived.

[0051] According to one embodiment of the present invention, in the step of noise filtering of an optical signal, the formula for calculating the peak wavelength in the step of extracting the peak wavelength from the normalized spectral intensity distribution curve using the weighted centroid method is expressed as follows: x=

[0052] Where x is the centroid position corresponding to the peak wavelength. i For the spectrometer i 1 pixel For the first i Light intensity gradient consistency weights corresponding to each pixel.

[0053] The above processing can obtain the peak wavelength with sub-nanometer precision and map it into a high-precision spectral confocal displacement measurement value.

[0054] According to one embodiment of the present invention, the interference laser data is obtained based on the interference fringe data of the interference laser received by the laser interference device 22, for use in obtaining the axial displacement of the movable reflector 15, wherein the axial displacement is obtained by phase subdivision of the interference fringes, and is expressed as: d =

[0055] in, d This refers to the axial displacement of the movable reflector 15. λ The wavelength of the laser. N This represents the number of effective interference fringes obtained through phase subdivision.

[0056] In this embodiment, the step of obtaining interference laser data based on interference fringe data of interference laser received by laser interferometer 22 includes the following steps for processing interference laser data: interference fringe acquisition, fringe noise reduction, direction determination, phase subdivision, fringe counting, and displacement calculation. Among these steps, a 633nm helium-neon laser is used as the interference source. After the interference fringe signal is acquired by the detector, bandpass filtering and baseline correction are first performed to eliminate environmental interference and DC drift. The movement direction of the movable reflector is distinguished by bidirectional orientation determination of the rising / falling edge of the fringes, thus avoiding false counting of fringes due to vibration. Sub-fringe precision detection is achieved by subdividing the interference fringes by λ / 8 phase. The number of quantitative interference fringes N is obtained by counting the fringes after subdivision. Therefore, in step S3, the data processing unit 3 fuses the spectral confocal data and the laser interferometric data, using the interferometric laser data as the long-range absolute displacement reference and the spectral confocal data as the displacement correction amount, and outputs the compensated long-range axial displacement measurement result. In this step, the displacement measurement value of the movable mirror 15 obtained based on the spectral confocal data and the axial displacement of the movable mirror 15 obtained based on the interferometric laser data are synchronously fused to achieve complementary output of long-range and high-precision measurement processes. The laser interferometric data is used as the long-range absolute displacement reference to ensure the measurement range; the spectral confocal data is used as the high-precision micro-displacement correction to ensure the measurement accuracy; after data fusion, a single, final, and optimal high-precision long-range axial displacement result is output, ensuring the high-precision realization of the measurement result after the complementary fusion and calculation of two sets of data collected coaxially, synchronously, and at the same measurement point.

[0057] The above description is merely an example of a specific solution of the present invention. For any devices and structures not described in detail herein, it should be understood that they are implemented using common devices and methods already available in the art.

[0058] The above description is merely one embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A measurement device based on spectral confocal coupling and laser interferometry, characterized in that, include: A spectral confocal measurement unit (1), a control unit (2) connected to the spectral confocal measurement unit (1), and a data processing unit (3) connected to the control unit (2). The spectral confocal measurement unit (1) includes: an entrance aperture structure (11), a first lens (12), a beam combiner (13), a second lens (14), and a movable reflector (15). The entrance aperture structure (11), the first lens (12), the beam combiner (13), the second lens (14), and the movable mirror (15) are arranged sequentially along the same spectral confocal principal optical axis; The control unit (2) is connected to the entrance aperture structure (11) and the beam combiner (13) respectively; wherein, the control unit (2) provides focused white light to the spectral confocal measurement unit (1) based on the entrance aperture structure (11) and collects the returned spectral confocal data to obtain the axial displacement measurement value of the movable mirror (15) along the spectral confocal principal optical axis, and the control unit (2) provides interference laser to the spectral confocal measurement unit (1) based on the beam combiner (13) and collects the returned interference laser data to obtain the axial displacement of the movable mirror (15) along the same spectral confocal principal optical axis; The data processing unit (3) uses the interferometric laser data as the long-range absolute displacement reference and the spectral confocal data as the displacement correction amount to output the compensated long-range axial displacement measurement result.

2. The measuring device according to claim 1, characterized in that, The beam combiner (13) is a parallel planar plate structure. A white light broadband anti-reflection film is coated on one side of the beam combiner (13) opposite to the first lens (12), and a laser high reflectivity film is coated on the other side of the beam combiner (13).

3. The measuring device according to claim 2, characterized in that, The control unit (2) includes: a spectral confocal controller (21) and a laser interferometer (22); The spectral confocal controller (21) is connected to the entrance aperture of the entrance aperture structure (11) via an optical fiber (4); The laser interference device (22) and the beam combiner (13) are on the same optical path.

4. The measuring device according to claim 3, characterized in that, The spectral confocal controller (21) includes: a white light source and a spectrometer; The output end of the white light source and the input end of the spectrometer are both coupled to the same end of the optical fiber (4). The other end of the optical fiber (4) is connected to the entrance hole of the entrance hole structure (11) through a coaxial coupling connection structure. The white light source is used to provide white light, and the spectrometer is used to receive the returned reflected light signal and obtain spectral confocal data. The laser interference device (22) includes: a laser source, a detector, and a laser interference optical path; The laser source and the detector are respectively opposite to the laser interference optical path, and the beam combiner (13) is connected to the laser interference optical path. The laser source is used to provide interference laser to the beam combiner (13), and the detector is used to receive the returned interference laser and obtain the interference laser data. The focusing data is obtained based on the peak wavelength of the optical signal; The interference laser data is obtained based on the interference fringe data of the interference laser.

5. The measuring device according to claim 4, characterized in that, The laser interference optical path includes: a beam splitter (221) and a reflector (222). The laser source and the detector are located on the same side of the beam splitter (221) and are both on the input path of the beam splitter (221); A fixed reflector (222) is connected to one beam splitter (221) to form a reference arm, and the other beam splitter (221) is connected to the beam combiner (13) to form a measurement arm; The measuring arm extends along the spectral confocal principal optical axis of the spectral confocal measuring unit (1).

6. The measuring device according to claim 5, characterized in that, Along the spectral confocal principal optical axis of the spectral confocal measurement unit (1), the distance L0 between the lower side of the entrance aperture structure (11) and the upper side of the movable reflector (15) is at least 160 mm, and the distance L1 between the axis of the beam combiner (13) and the upper side of the movable reflector (15) is at least 100 mm.

7. A measurement method using the measuring device according to any one of claims 1 to 6, characterized in that, include: S1. Fix the sample on the movable mirror (15) and drive the movable mirror (15) to move to the measurement start point and measurement end point of the sample to calibrate the measurement range and obtain the displacement of the measurement start point and measurement end point based on the laser interferometer (22); S2. Move the movable mirror (15) to the measurement starting point of the sample, and control the movable mirror (15) to move towards the measurement endpoint according to the preset step distance. At each step position, the spectral confocal controller (21) and the laser interference device (22) synchronously collect spectral confocal data and interference laser data, and send them to the data processing unit (3). S3. The data processing unit (3) performs complementary fusion processing on the spectral confocal data and the laser interferometric data, using the interferometric laser data as the long-range absolute displacement reference and the spectral confocal data as the displacement correction amount, and outputs the compensated long-range axial displacement measurement results.

8. The measurement method according to claim 7, characterized in that, The spectral confocal data is obtained by decoding the reflected light signal received by the spectrometer in the spectral confocal controller (21); wherein the decoding processing steps for the reflected light signal include: The reflected light signal is subjected to noise filtering to remove high-frequency random noise and environmental interference; the noise filtering includes median filtering and mean filtering. The reflected light signals after noise filtering are arranged according to the wavelength dimension to form a continuous spectral intensity distribution curve; The light intensity is normalized on the spectral intensity distribution curve, and the light intensity gradient consistency of each data point on the spectral intensity distribution curve is converted into light intensity gradient consistency weight, thereby eliminating the intensity drift caused by light source fluctuation and optical path loss. The peak wavelength was extracted from the normalized spectral intensity distribution curve using the weighted centroid method. By mapping the peak wavelength to the pre-calibrated wavelength-displacement response curve, the spectral confocal data is obtained and the displacement measurement value is derived.

9. The measurement method according to claim 8, characterized in that, In the step of noise filtering of the optical signal, the formula for calculating the peak wavelength in the step of extracting the peak wavelength from the normalized spectral intensity distribution curve using the weighted centroid method is expressed as follows: x= Where x is the centroid position corresponding to the peak wavelength. i For the spectrometer i 1 pixel For the first i Light intensity gradient consistency weights corresponding to each pixel.

10. The measurement method according to claim 9, characterized in that, The interference laser data is obtained based on the interference fringe data of the interference laser received by the laser interference device (22), and is used to obtain the axial displacement of the movable reflector (15). The axial displacement is obtained by phase subdivision of the interference fringes and is expressed as follows: d = in, d For the axial displacement of the movable reflector (15), λ The wavelength of the laser. N This represents the number of effective interference fringes obtained through phase subdivision.

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