Interference confocal measurement system based on two-dimensional dispersion and measurement method thereof

Abstract

The invention relates to the field of optical detection, in particular to an interference confocal measurement system based on two-dimensional dispersion and a measurement method thereof. White light generated by a light source is collimated into parallel light through a first collimating lens, is shaped into rectangular light through a rectangular diaphragm, and is shaped into a linear light beam through a column focusing lens and a rectangular slit; the light is divided into reference light and object light through a beam splitter, the reference light is achromatic through a first achromatic objective lens, then enters a reference plane mirror and is reflected back to the beam splitter by the reference plane mirror, the object light is focused to positions of different depths of an object to be measured after being dispersed through a dispersion lens and is reflected back to the beam splitter by the object to be measured, and the two beams of light are reconverged in the beam splitter. And after being collimated by the second collimating lens, dispersed by the dispersion grating and achromatic by the second achromatic objective lens in sequence, the light is focused on the target surface of the spectrograph for spectrum and interference analysis. According to the invention, line scanning, dispersion and interference measurement are combined, so that the measurement precision can be greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of optical detection, and in particular relates to an interference confocal measurement system based on two-dimensional dispersion and a measurement method thereof. Background Art

[0002] Three-dimensional surface measurement and imaging are becoming increasingly important in many fields, such as surface defect detection of tiny electronic components and three-dimensional structure measurement of living cells. Therefore, the demand for fast and accurate surface profile measurement technology is becoming increasingly urgent. Among the existing surface profile measurement methods, optical techniques such as optical coherence tomography and confocal microscopy have attracted much attention from scholars and researchers because they do not require direct contact and damage to the object to be measured. Compared with interferometric optical coherence tomography imaging using low numerical aperture lenses, confocal microscopy using high numerical aperture lenses combined with limited focal depth from pinholes can provide higher axial and lateral resolution. However, despite these advantages, confocal microscopy is still limited in imaging speed by its mechanical scanning process in the lateral and axial directions. Therefore, many studies have attempted to overcome this limitation by improving the scanning speed.

[0003] The spectral confocal displacement sensor is a new method proposed in recent decades to solve the problem of slow scanning speed. This method uses optical principles to eliminate the mechanical axial scanning process. The spectral confocal displacement sensor uses the chromatic aberration of the lens to generate wavelength-dependent light dispersion, so that each wavelength corresponds to a different focal length. This spectral encoding technology associates the focal length of the lens with the wavelength, thereby achieving accurate depth measurement. In this way, the spectral confocal displacement sensor not only improves the scanning speed, but also retains the advantages of high resolution and high precision, bringing new breakthroughs to 3D surface measurement technology.

[0004] However, the researchers were not satisfied with the progress of axial scanning, and the planar two-dimensional scanning became the next target of scholars. At this time, the line spectrum confocal sensor technology came into being: the line spectrum confocal technology is an extension of the point spectrum confocal technology, which can be regarded as a special multi-point confocal scanning. This technology replaces the pinhole in the point spectrum confocal system with a slit, and uses the slit to generate a line light source, which can be regarded as a collection of countless point light sources. The linear light is focused on the surface of the object to be measured, and the reflected light is received by the linear array detector. Combined with the one-dimensional displacement platform, fast three-dimensional detection can be achieved. This method not only improves the detection efficiency, but also expands the scope of application. Finally, adding an interferometric measurement unit can improve the overall resolution of the system and achieve high-precision measurement. The line spectrum confocal system significantly improves the detection efficiency, which is equivalent to adding an additional scanning dimension compared to the point spectrum confocal system. However, since the slit size in the line spectrum confocal system is much larger than the pinhole, the system is weak in filtering out stray light, and thus performs poorly in resolution. This shortcoming makes the line spectrum confocal system have certain limitations in high-precision measurement. Summary of the invention

[0005] In view of this, the present invention aims to provide an interferometric confocal measurement system based on two-dimensional dispersion and a measurement method thereof, so as to solve the problem that the measurement accuracy of the line spectrum confocal system is seriously reduced due to the relatively large slit size.

[0006] To achieve the above object, the technical solution created by the present invention is implemented as follows: An interferometric confocal measurement system based on two-dimensional dispersion includes a light source, a first collimating lens, a rectangular aperture, a cylindrical focusing lens, a slit, a beam splitter, a first achromatic objective lens, a reference plane mirror, a dispersive lens, a piezoelectric ceramic driver, a stepping drive stage, a second collimating lens, a dispersive grating, a second achromatic objective lens and a spectrometer; wherein, The light source is used to emit white light; The first collimating lens is used to collimate the white light into a parallel light beam; The rectangular aperture is used to transform a parallel light beam into a rectangular light beam; The cylindrical focusing lens and the slit are used to transform the rectangular beam into a line beam; The beam splitter is used to split the line beam into reflected light and transmitted light, the transmitted light is used as the reference light, and the reflected light is used as the object light; The first achromatic objective lens is used to perform chromatic aberration correction on the reference light; The reference plane mirror is used to reflect the reference light after chromatic aberration correction back to the beam splitter; The dispersion lens is used to decompose the object light into lights of different wavelengths. The lights of different wavelengths are focused to different depths of the object to be measured, and then reflected back to the beam splitter by the object to be measured, and then aggregated and compounded with the reference light. The second collimating lens is used for collimating the composite light; The dispersion grating is used to decompose the collimated composite light into lights of different wavelengths; The second achromatic objective lens is used to perform chromatic aberration correction on light of different wavelengths so that light of different wavelengths can be focused onto the target surface of the spectrometer; The spectrometer is used to measure the three-dimensional information of the object to be measured by adopting the principle of dispersive confocal interferometry; Piezoelectric ceramic actuator, used to change the optical path of the object light; The stepper drive stage is used to carry the object to be measured and drive the object to be measured to move in the x direction and the y direction. The x direction is the lateral direction of the object to be measured, and the y direction is the longitudinal direction of the object to be measured.

[0007] A measurement method implemented by using the above-mentioned interferometric confocal measurement system based on two-dimensional dispersion, dividing the object to be measured into different sections, comprises the following steps: S1: Move the stepper drive stage along the y direction to focus the object light onto the first section of the object to be measured, and then move the stepper drive stage along the x direction to perform line scanning on the first section; S2: by applying a phase shift of π / 2 in the x-direction and the y-direction respectively, using a spectrometer to collect 4 frames of interference images with a phase difference of π / 2, and calculating the initial phase of the object to be measured; S3: According to the initial phase of the object to be measured, the phase difference in the x direction and the y direction are wrapped respectively to obtain the wrapped phase difference: S4: unwrapping the wrapped phase difference using a least square unwrapping algorithm to obtain an unwrapped phase; S5: Calculate the height value of each position on the first slice according to the unwrapped phase; S6: Move the stepper drive stage along the y direction, repeat steps S1 to S5, calculate the height values ​​of all positions on each section, and obtain the three-dimensional information of the object to be measured.

[0008] Furthermore, the obtained 4-frame interference images are:

[0009] in, , , , are the light intensities of the interference fringes in the four interference images; is the background light intensity of the interference image; is the modulation amplitude of the interference fringes; is the initial phase of the wavefront of the object to be measured; is the coordinate of the pixel point in the interference image; then:

[0010] Furthermore, the package phase difference is:

[0011]

[0012] in, is the phase difference between the x+1 coordinate point and the x coordinate point in the x direction, is the phase difference between the y+1 coordinate point and the y coordinate point in the y direction, Indicates the object to be measured The phase value of the coordinate point, Indicates the object to be measured Phase value of the coordinate point.

[0013] Further, the unwrapping phase for:

[0014]

[0015] in, is the inverse operation of the two-dimensional Laplace operator, is the divergence of the phase gradient field, is the phase difference between the x+2 coordinate point and the x+1 coordinate point in the x direction, is the phase difference between the y+2 coordinate point and the y+1 coordinate point in the y direction.

[0016] Furthermore, the height value z of a position on the first section is:

[0017] in, is the average wave number of the light source.

[0018] Compared with the prior art, the invention can achieve the following beneficial effects: 1. Improve scanning speed: Line scanning along the X direction can simultaneously acquire a whole line of data, thereby significantly improving the image acquisition speed, which is suitable for real-time observation and rapid imaging needs.

[0019] 2. Enhanced resolution: The application of dispersive spectroscopy expands the axial resolution, which can achieve finer depth resolution capabilities, making the three-dimensional structural information of the object to be measured more accurate.

[0020] 3. Three-dimensional reconstruction capability: The introduction of interferometry enables the dispersive interferometry confocal measurement system to perform high-precision depth measurement, combined with radial and axial extended scanning capabilities to achieve high-precision three-dimensional reconstruction of the object to be measured.

[0021] 4. Improve measurement accuracy: Interferometry provides extremely high vertical resolution, usually at the nanometer level, which is very important for applications that require precise measurement of surface topography.

[0022] 5. Reduce acquisition time and improve efficiency: Through line scanning and spectrum expansion, parallel data acquisition is achieved, which reduces scanning time and improves the overall efficiency of the dispersive interferometry confocal measurement system.

[0023] 6. Suitable for dynamic processes: The dispersive interferometry confocal measurement system can quickly capture images and perform real-time analysis, which is very suitable for the observation of dynamic processes, such as the dynamic behavior analysis of biological objects to be tested. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings: Figure 1 It is a schematic structural diagram of an interferometric confocal measurement system based on two-dimensional dispersion according to an embodiment of the invention; Figure 2 is a schematic diagram of the intensity of a single-wavelength signal of an object light according to an embodiment of the invention; Figure 3 is a schematic diagram of the intensity of the interference reference signal according to an embodiment of the invention; Figure 4 is a schematic diagram of the intensity of the dispersion interference signal according to the embodiment of the invention; Figure 5 4 is a schematic diagram of interference images according to an embodiment of the invention; wherein (a) is an interference image with a phase shift of 0, (b) is an interference image with a phase shift of π / 2, (c) is an interference image with a phase shift of π, and (d) is an interference image with a phase shift of 3π / 2; Figure 6 is a schematic diagram of the position of point S in the information of the object to be measured according to an embodiment of the invention; Figure 7 It is a schematic diagram of the position of point S in the spectrum analysis described in the embodiment of the invention.

[0025] Description of reference numerals: 1. Light source; 2. First collimating lens; 3. Rectangular aperture; 4. Cylindrical focusing lens; 5. Slit; 6. Beam splitter; 7. First achromatic objective lens; 8. Reference plane mirror; 9. Dispersion lens; 10. Object to be measured; 11. Stepper drive stage; 12. Spectrometer; 13. Second achromatic objective lens; 14. Dispersion grating; 15. Second collimating lens; 16. Piezoelectric ceramic driver. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the invention more clear, the invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described here are only used to explain the invention and do not constitute a limitation of the invention.

[0027] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0028] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0029] In the description of the invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the invention can be understood according to specific circumstances.

[0030] The following will refer to Figure 1-Figure 7 The invention is described in detail with reference to the embodiments.

[0031] like Figure 1 As shown, the interferometric confocal measurement system based on two-dimensional dispersion provided by the embodiment of the present invention includes a light source 1, a first collimating lens 2, a rectangular aperture 3, a cylindrical focusing lens 4, a slit 5, a beam splitter 6, a first achromatic objective lens 7, a reference plane mirror 8, a dispersion lens 9, a stepping drive stage 11, a spectrometer 12, a second achromatic objective lens 13, a dispersion grating 14, a second collimating lens 15 and a piezoelectric ceramic driver 16.

[0032] The description of each device is as follows: Light source 1: used to output white light; The first collimating lens 2 is used to collimate the white light into parallel light; Rectangular aperture 3: used to shape parallel light into rectangular light; Cylindrical focusing lens 4: used to focus rectangular light into a straight line; Slit 5: used to control the size and shape of the light beam passing through; Beam splitter 6: used to split the light beam; First achromatic objective lens 7: used for performing dispersion correction on the light beam; Reference plane mirror 8: used for light beam reflection and optical path difference in interferometry; Dispersion lens 9: used to decompose the composite light into lights of different wavelengths; Stepper drive table 11: used to carry the object to be tested 10, and drive the object to be tested 10 to move in the x direction and the y direction, the x direction is the lateral direction of the object to be tested 10, the line scanning direction of the object to be tested 10 is the x direction, the y direction is the longitudinal direction of the object to be tested 10, the section direction of the object to be tested 10 is the y direction, and the z direction is the depth direction of the object to be tested 10. The stepper drive table 11 is a motion table that realizes micron-level stepping; Spectrometer 12: used to receive spectrum information and perform spectrum and interference analysis; the photodetector of the spectrometer 12 may be CCD or CMOS; The second achromatic objective lens 13 is used to perform chromatic aberration correction on the light of multiple wavelengths to achieve consistent focusing, so that the light of different wavelengths is focused onto the target surface of the photodetector; Dispersion grating 14: used for decomposing the composite light into lights of different wavelengths; The second collimating lens 15 is used to collimate the light beam into parallel light; Piezoelectric ceramic driver 16: The dispersion lens 9 is arranged on the piezoelectric ceramic driver 16 to change the optical path of the object light, thereby changing the optical path difference between the object light and the reference light.

[0033] The working principle of the interferometric confocal measurement system based on two-dimensional dispersion is as follows: the white light generated by the light source 1 is collimated into parallel light by the first collimating lens 2, the parallel light is shaped into a rectangular light beam by the rectangular aperture 3, the rectangular light beam is shaped into a line light beam by the cylindrical focusing lens 4 and the rectangular slit 5, the line light beam is divided into reflected light and transmitted light by the beam splitter 6, the transmitted light is used as the reference light, and the reflected light is used as the object light, the reference light is achromatized by the first achromatic objective lens 7 and then incident on the reference plane mirror 8, and then reflected back to the beam splitter 6 by the reference plane mirror 8, the object light is dispersed by the dispersive lens 9 and focused to positions at different depths of the object to be measured 10, and then reflected back to the beam splitter 6 by the object to be measured 10, the light reflected by the object to be measured 10 and the light reflected by the reference plane mirror 8 are reassembled at the beam splitter 6, and then are focused on the target surface of the photodetector after being collimated by the second collimating lens 15, dispersed by the dispersion grating 14 and achromatized by the second achromatic objective lens 13 in sequence, and then subjected to spectral and interference analysis.

[0034] When the reference plane mirror 8 is blocked, the signal intensity of the single wavelength of the object light reflected from the surface of the object 10 to be measured is as follows: Figure 2 When the object 10 to be measured is blocked, the light reflected by the reference plane mirror 8 is used as the interference reference signal. The intensity of the interference reference signal is shown in Figure 3 When the reference plane mirror 8 and the object to be measured 10 are not blocked, the light reflected from the surface of the object to be measured 10 and the light reflected from the reference plane mirror 8 can generate a dispersion interference signal. The intensity of the dispersion interference signal is shown in Figure 4 shown.

[0035] The interference signal is subjected to sinusoidal modulation with a short period of time. At least three points must be collected in each period to obtain relatively reliable data information and effective data processing. The coherence peak addressing method is proposed based on the characteristics of short coherence length and obvious coherence peak of white light signal. Taking two points of different heights as an example, coherence peaks appear in the two points in turn during the scanning measurement process. Taking the position of the peak point of the coherence peak as a reference, the difference between the peak points of the two coherence peaks in the z direction is the height difference between the two points.

[0036] The four-step phase shift method is used for solution. As a classic phase solution algorithm, the four-step phase shift method can effectively calculate the phase distribution of the ideal phase shift diagram group. Under each single wavelength and single sampling point, the height information of a certain point S on the current section of the object to be measured 10 is calculated. , Determined, then at the desired z height, the position of the dispersion lens 9 is moved by controlling the piezoelectric ceramic driver 16 to change the optical path difference between the reference light and the object light, and the phase shift is controlled to be 0, π / 2, π, and 3π / 2. During the phase shift process, the spectrometer 12 is used to collect interference images under different phase shifts. After each phase shift, one interference image is collected, and a total of 4 interference images with a phase difference of π / 2 are obtained, such as Figure 5 shown.

[0037] At this point, the sinusoidal grating intensity function of the image can be simplified to:

[0038] in, is the background light intensity of the interference image; is the modulation amplitude of the interference fringes; is the initial phase of the wavefront of the object 10 to be measured; is the shift phase value; is the coordinate information of the pixel points in the interference image.

[0039] The following four formulas are obtained through 4 frames of interference images:

[0040] in, , , , are the light intensities of the interference fringes in the four interference images.

[0041] The initial phase of the wavefront of the object to be measured can be calculated by transforming the 4 formulas and eliminating A and B. :

[0042] In actual measurement, since the range of change of the surface morphology of the object 10 to be measured varies, the phase Often exceeds the range of one cycle (2π). However, the phase distribution obtained The phase distribution diagram will be constrained within the 2π interval, so the obtained phase distribution diagram will be truncated into a step distribution. In order to splice into a phase diagram that conforms to the actual continuous distribution, the phase difference in the x direction and the y direction needs to be wrapped separately, and then the wrapped phase needs to be unwrapped.

[0043] The phase difference in the x direction and the y direction is wrapped and calculated separately to obtain the wrapped phase difference:

[0044]

[0045] in, is the phase difference between the x+1 coordinate point and the x coordinate point in the x direction, is the phase difference between the y+1 coordinate point and the y coordinate point in the y direction, Indicates the object to be measured The phase value of the coordinate point, Indicates the object to be measured Phase value of the coordinate point.

[0046] In order to make the restored phase The gradient in the x and y directions and the wrapped phase difference , As a close approximation, the present invention adopts the least squares unwrapping algorithm for unwrapping:

[0047]

[0048] in, is the inverse operation of the two-dimensional Laplace operator, is the divergence of the phase gradient field, is the phase difference between the x+2 coordinate point and the x+1 coordinate point in the x direction, is the phase difference between the y+2 coordinate point and the y+1 coordinate point in the y direction.

[0049] Finally, the height at the single wavelength point S in the line scan of the current section is calculated by the following formula:

[0050] in, is the average wave number of the light source.

[0051] The desired z is the height value of a single wavelength point S in the x direction during line scanning, and its position on the object to be measured 10 is as follows: Figure 6 As shown, the line scanning direction of the object 10 to be measured is the x direction, and the y direction is the section direction. In the spectrum analysis, the position of point S is as follows: Figure 7 As shown, the scanning direction is Figure 6 The x direction in .

[0052] After all the spectral information of the entire xz plane is calculated and all the height information of the xz plane is obtained, the object to be measured 10 is moved to the next section along the y direction by the stepping drive table 11, and a line scan is performed. The above calculation steps are repeated to finally obtain the three-dimensional information of the object to be measured 10 and achieve high-precision measurement.

[0053] The technical effect of the present invention is described by taking an example. Scan the object 10 to be measured horizontally in the x and y directions and take 100 scanning points respectively. , At the same time, 50 scanning points are taken in the z direction of the axial scanning of the object to be measured 10 Each movement of the stepping drive stage 11 takes t=0.1s, and the measurement time is negligible relative to the movement time.

[0054] Traditional point scanning takes time 50000s. The present invention uses the transverse encoding method of the line light source and combines the axial dispersion principle, and can simultaneously measure all scanning points in the x-direction and z-direction, that is, reduce the scanning in the x-direction and z-direction, and only scan in the y-direction, and the scanning time is 10s, so the scanning time required by the present invention is greatly reduced.

[0055] At the same time, the traditional point confocal microscope is simulated, using a Gaussian beam with a wavelength of 633nm and a radius of 2.24mm, and the high NA objective lens is 0.9. The axial resolution is 203nm. In the present invention, the dispersion interference method is used for calculation. When the wavelength and radius of the Gaussian beam remain unchanged, the dispersion lens uses typical BK7 glass with a moderate dispersion coefficient of about 0.0103nm. - ¹ mm - ¹, the focal length is 98mm. The dispersion effect will cause the focus position of beams of different wavelengths to shift to different degrees. The impact of axial resolution can be estimated by the dispersion of the optical system, and its axial resolution is 876nm. This is due to the focus shift introduced by the dispersion lens, and the accuracy decreases by about 331.53%.

[0056] Although the dispersion lens introduces a certain degree of accuracy reduction, resulting in a decrease in axial resolution relative to the traditional confocal microscope system (about 4 times), its advantage in measurement speed is obvious. From the previous calculation, it can be seen that the present invention significantly reduces the scanning time. Although the accuracy is reduced, this reduction in accuracy is acceptable for many high-speed scanning and dynamic process monitoring scenarios, especially when it is necessary to quickly obtain three-dimensional morphological information.

[0057] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the disclosure of the present invention can be performed in parallel, sequentially or in different orders, as long as the desired results of the technical solution disclosed in the present invention can be achieved, and this document does not limit this.

[0058] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An interferometric confocal measurement system based on two-dimensional dispersion, characterized in that: It includes a light source, a first collimating lens, a rectangular aperture, a cylindrical focusing lens, a slit, a beam splitter, a first achromatic objective lens, a reference plane mirror, a dispersive lens, a piezoelectric ceramic driver, a stepping drive stage, a second collimating lens, a dispersive grating, a second achromatic objective lens and a spectrometer; wherein, The light source is used to emit white light; The first collimating lens is used to collimate the white light into a parallel light beam; The rectangular aperture is used to transform a parallel light beam into a rectangular light beam; The cylindrical focusing lens and the slit are used to transform the rectangular beam into a line beam; The beam splitter is used to split the line beam into reflected light and transmitted light, the transmitted light is used as the reference light, and the reflected light is used as the object light; The first achromatic objective lens is used to perform chromatic aberration correction on the reference light; The reference plane mirror is used to reflect the reference light after chromatic aberration correction back to the beam splitter; The dispersion lens is used to decompose the object light into lights of different wavelengths. The lights of different wavelengths are focused to different depths of the object to be measured, and then reflected back to the beam splitter by the object to be measured, and then aggregated and compounded with the reference light. The second collimating lens is used for collimating the composite light; The dispersion grating is used to decompose the collimated composite light into lights of different wavelengths; The second achromatic objective lens is used to perform chromatic aberration correction on light of different wavelengths so that light of different wavelengths can be focused onto the target surface of the spectrometer; The spectrometer is used to measure the three-dimensional information of the object to be measured by adopting the principle of dispersive confocal interferometry; Piezoelectric ceramic actuator, used to change the optical path of the object light; The stepper drive stage is used to carry the object to be measured and drive the object to be measured to move in the x direction and the y direction. The x direction is the lateral direction of the object to be measured, and the y direction is the longitudinal direction of the object to be measured.

2. A measurement method implemented by the interferometric confocal measurement system based on two-dimensional dispersion according to claim 1, wherein the object to be measured is divided into different sections, characterized in that: The steps include: S1: Move the stepper drive stage along the y direction to focus the object light onto the first section of the object to be measured, and then move the stepper drive stage along the x direction to perform line scanning on the first section; S2: by applying a phase shift of π / 2 in the x-direction and the y-direction respectively, using a spectrometer to collect 4 frames of interference images with a phase difference of π / 2, and calculating the initial phase of the object to be measured; S3: According to the initial phase of the object to be measured, the phase difference in the x direction and the y direction are wrapped respectively to obtain the wrapped phase difference: S4: unwrapping the wrapped phase difference using a least square unwrapping algorithm to obtain an unwrapped phase; S5: Calculate the height value of each position on the first slice according to the unwrapped phase; S6: Move the stepper drive stage along the y direction, repeat steps S1 to S5, calculate the height values ​​of all positions on each section, and obtain the three-dimensional information of the object to be measured.

3. The measuring method according to claim 2, characterized in that: The 4 interferometric images obtained are: in, , , , are the light intensities of the interference fringes in the four interference images; is the background light intensity of the interference image; is the modulation amplitude of the interference fringes; is the initial phase of the wavefront of the object to be measured; is the coordinate of the pixel point in the interference image; then:

4. The measuring method according to claim 3, characterized in that: The package phase difference is: in, is the phase difference between the x+1 coordinate point and the x coordinate point in the x direction, is the phase difference between the y+1 coordinate point and the y coordinate point in the y direction, Indicates the object to be measured The phase value of the coordinate point, Indicates the object to be measured The phase value of the coordinate point.

5. The measuring method according to claim 4, characterized in that: Unwrapped Phase for: in, is the inverse operation of the two-dimensional Laplace operator, is the divergence of the phase gradient field, is the phase difference between the x+2 coordinate point and the x+1 coordinate point in the x direction, is the phase difference between the y+2 coordinate point and the y+1 coordinate point in the y direction.

6. The measuring method according to claim 5, characterized in that: The height z of a position on the first tangent plane is: in, is the average wave number of the light source.

Images