CN108844492B - Microstructure morphology measurement method and device based on spectral modulation degree depth coding - Google Patents

Abstract

The invention discloses a microstructure morphology measuring method and a microstructure morphology measuring device based on spectral modulation degree depth coding. The measured element and the spatial light modulator are in object image conjugation under the central wavelength of the spectral range adopted by measurement; the light beam deflection coupler, the spatial light modulator, the collimation and beam expansion lens, the beam splitter, the axial non-achromatic microscope objective, the imaging lens and the color camera are in a common light path structure. During measurement, firstly pre-calibrating the corresponding relation of spectrum and depth of a system device, then collecting each frame of monochromatic phase-shifting fringe pattern reflected by a measured element through a measuring device to obtain the modulation degree distribution of each monochromatic fringe pattern related to the surface shape of a measured element, and acquiring a coded image; and adopting a Gaussian, quasi-Gaussian or spline model to fit and determine a 'spectrum-modulation degree' relation curve of each point on the surface to be measured, demodulating to obtain depth information of each point on the corresponding surface to be measured, and completing the mechanical-free scanning and full-field non-contact rapid high-precision measurement of the three-dimensional shape distribution microstructure shape of the element to be measured.

Description

A method for measuring microstructure topography based on spectral modulation depth coding and the same device

technical field

The invention relates to a measurement technology for microstructure topography, in particular to a microstructure topography measurement method and device based on spectral modulation depth coding, and belongs to the technical field of advanced manufacturing and detection.

Background technique

In important fields of the national economy such as semiconductor manufacturing, artificial intelligence, aerospace, etc., opto-mechanical components such as silicon-based wafers, microelectromechanical systems (MEMS), and computer-generated holography (CGH) have a wide range of application. The surfaces of these components often have complex (like) mirror microstructures formed by machining, laser/plasma etching, and sputtering coatings. Its topography distribution not only reflects the external characteristics of components, but also closely related to internal characteristics such as hardness, residual stress, service life, damage threshold and so on. As an important part of the component manufacturing and production process, testing can help pre-evaluate and control the performance of components. The detection accuracy often directly determines the quality of component processing and molding. In the past ten years, the ultra-precision detection of the surface microstructure and morphology of such components has attracted the attention and research of scientific and technological workers in related fields.

Because of its non-contact, full-field measurement, high-precision and other characteristics, optical interference microscopy has been widely used in the precise detection of the microscopic topography of opto-mechanical components. The traditional scheme mostly uses a laser with better monochromaticity as the light source, combined with phase-shifting interferometry, the measurement accuracy can reach the sub-nanometer level. However, the requirement that the optical path difference between adjacent measured points is less than one-quarter wavelength limits the single-wavelength laser interference microscopy test technology to a certain extent (like) mirror elements with complex microstructures (such as steps) on the surface. The application of device three-dimensional topography detection. Although white light interferometry has a unique zero optical path difference position and can perform absolute measurement, it is often used for high-precision detection of the surface shape of the above-mentioned components, but it requires the use of high-precision microdisplacers (such as piezoelectric ceramic stacks, piezoelectric ceramic stacks, piezoelectric transducer, PZT) makes a fine scan along the axis. As a result, the entire measurement time is long, and it is only suitable for the detection of static object surfaces, and is extremely sensitive to external airflow disturbance and vibration during the scanning process, and the system structure is also relatively complex and costly.

In contrast, the 3D topography measurement method based on fringe modulation degree coding, as an incoherent optical detection technology, has the advantages of more flexible and controllable measurement process and relatively simple system structure. Axial surface distribution still needs to use PZT for axial scanning, which also has shortcomings such as weak anti-interference ability and only suitable for static measurement. Therefore, on the basis of not significantly increasing the structural complexity and cost of the system, how to realize the fast and high-precision non-mechanical scanning, full-field non-contact three-dimensional topography distribution of opto-mechanical components with complex (like) mirror microstructures on the surface Measurement is a research hotspot and trend in this field.

SUMMARY OF THE INVENTION

Aiming at the shortcomings of the prior art, the present invention provides a device that does not require mechanical scanning components, and can realize fast and accurate measurement of (like) mirror microstructures, especially (like) mirror microstructure elements with complex and discontinuous surface changes. method and apparatus.

The technical scheme to achieve the purpose of the present invention is to provide a microstructure topography measuring device based on the depth coding of spectral modulation degree, which comprises a wide-spectrum light source, a beam coupler, a spectral modulation gate, a uniform light coupler, and a beam deflection coupling. device, spatial light modulator, collimating beam expander lens, beam splitter, axial non-achromatic microscope objective, stage, imaging lens, color camera, computer and controller; the computer is connected to the controller and the color camera respectively ; The measured element is placed on the stage, and the measured element and the spatial light modulator are conjugated to the object image at the center wavelength of the spectral range used for the measurement; beam refracting coupler, spatial light modulator, collimating beam expander The lens, beam splitter, axial non-achromatic microscope objective, imaging lens and color camera form a common optical path structure; the polychromatic light emitted by the wide-spectrum light source is uniformly incident on the spectral modulation gate through the beam coupler, and the controller's The spectral modulation output end is connected with the spectral modulation gate. The spectral modulation gate sequentially outputs monochromatic light of specific wavelengths in the measurement spectral range. The incident monochromatic light field signal is incident on the spatial light modulator; the spatial light modulator is located at the position of the front focal plane of the collimating beam expanding lens, and the coded image output end of the controller is connected to the spatial light modulator, and the spatial light modulation The beam splitter outputs a spatially encoded monochromatic sinusoidal fringe light field signal, which is then coupled to the collimating beam expanding lens by the beam refraction coupler to become parallel light incident on the surface of the beam splitter; the beam splitter reflects the parallel monochromatic sinusoidal stripe light After entering the axial non-achromatic microscope objective, it is irradiated to the surface of the measured element, and the monochromatic sinusoidal fringe light reflected by the measured surface passes through the axial non-achromatic microscope objective and the beam splitter in turn, and is coupled by the imaging lens To the target surface of the color camera, the color camera transmits the collected image data to the computer.

The spectral modulation gating device of the present invention is an acousto-optic modulator, a spectral modulation gating system based on a dispersion element and a spatial light modulator; the spatial light modulator is a digital micromirror device and a liquid crystal on silicon; the The wide spectrum light source is halogen lamp, white light LED, super continuous spectrum laser; the color camera is a color three-chip CCD or CMOS camera.

The technical solution of the present invention also provides a method for measuring the topography of a microstructure based on the depth coding of the spectral modulation degree, comprising the following steps:

The first step, the pre-calibration of the "spectrum-depth" correspondence:

(1) The polychromatic light emitted by the wide-spectrum light source is gated and filtered by the spectral modulation gating device, and the monochromatic light of a specific wavelength is output, which is uniformly irradiated to the spatial light modulator through the uniform light coupler and the beam deflection coupler;

(2) Synchronously control the spatial light modulator to output a uniformly distributed monochromatic light signal, which is irradiated to the object through a beam-refracting coupler, a collimating beam expanding lens, a beam splitter and an axial non-achromatic microscope objective. Standard flat mirror on stage;

(3) Driven by the piezoelectric ceramic microdisplacer, the standard plane mirror performs axial scanning along the optical axis of the microscope objective, and reflects the monochromatic light signal into the axial non-achromatic microscope objective and beam splitter , and then receive and measure the wavelength value of the optical signal by the spectrometer, and record the axial movement position of the piezoelectric ceramic microdisplacer when the monochromatic optical signal reaches the peak value during the scanning process;

(4) Repeat steps (1) to (3) along the short-wave to long-wave direction or in the reverse direction within the spectral range used for the measurement to obtain a set of "spectrum-depth" data, and use polynomial or spline fitting methods to obtain "spectrum" - depth" corresponding relationship curve, complete the pre-calibration;

The second step, coded image acquisition: place the component under test on the stage, and adjust the position of the stage along the axial and radial directions so that the center wavelength of the component under test and the spatial light modulator is within the spectral range used for measurement The object image is conjugated below; the polychromatic light emitted by the wide-spectrum light source is filtered along the short-wave to long-wave direction or in the reverse direction by the spectral modulation gate, and the monochromatic light of the specific wavelength is sequentially output, and the light is passed through the uniform light coupler and the beam. The refracting coupler is uniformly incident on the spatial light modulator; the spatial light modulator is synchronously controlled, and the corresponding monochromatic phase-shifted sinusoidal fringe pattern light field signal is output in turn, and then the beam refracting coupler, collimating beam expanding lens, and beam splitter and the axial non-achromatic microscope objective lens is irradiated to the surface of the component under test; the controller controls the color camera to synchronously collect each frame of monochromatic phase-shift fringe pattern reflected by the component under test, and transmit it to the computer for storage and processing;

The third step is to demodulate the coded image: use the random phase-shift algorithm to process the obtained monochromatic phase-shift fringe patterns, and obtain the modulation degree distribution of each monochromatic light fringe pattern related to the surface shape of the tested object; Gauss-like or spline model fitting determines the "spectrum-modulation" relationship curve of each point on the test surface, and uses the modulation degree of each monochromatic light fringe to reach the extreme point at the position of its focal plane (that is, the depth position of the point to be tested). According to the “spectrum-depth” relationship curve obtained by pre-calibration in the first step, the depth information of each point on the surface to be measured can be obtained by demodulation. The microstructure and topography of the component can be used to complete the fast and high-precision measurement of the three-dimensional topography distribution of the tested component without mechanical scanning and full-field contact.

In the technical scheme of the present invention, the spectral range used for the measurement is the ultraviolet waveband, the visible light waveband or the infrared waveband.

The principle of the invention is: on the basis of the traditional three-dimensional topography measurement method based on fringe modulation degree coding, the monochromatic parallel light of different wavelengths is used to focus on different axial directions one by one through the axial non-achromatic optical system. The depth position and the modulation degree of each monochromatic light stripe change with the axial depth and reach a maximum value at the position of the focal plane (ie, the depth position of the point to be measured), realizing the “modulation degree-spectrum-depth” three. unique code.

Compared with the prior art, the significant advantages of the present invention are:

1. The measuring device provided by the present invention does not require axial mechanical scanning components, and realizes the three functions of "spectrum-modulation-depth" from the system hardware by means of a spectral modulation gating module, a spatial light modulator and an axial non-achromatic microscope objective. The unique coding between them can complete the full-field, non-contact, fast and accurate measurement of (like) mirror microstructures, especially the (like) mirror microstructure elements with complex and discontinuous surface changes, which can effectively suppress the The measurement error introduced by the scanning movement of mechanical parts improves the controllability and anti-interference ability of the system.

2. The spectral modulation depth coding algorithm provided by the present invention utilizes monochromatic parallel light of different wavelengths to focus on different axial depth positions one by one through an axial non-achromatic optical system, and the modulation degree of each monochromatic light stripe varies with The axial depth changes and reaches the extreme value near its focal plane position. From the measurement principle, the unique encoding between "spectrum-modulation-depth" can be realized, thus avoiding the traditional three-dimensional encoding based on fringe modulation. In the topography measurement method, the axial mechanical scanning, which is time-consuming, is susceptible to external interference, and has low flexibility, effectively reduces the measurement error introduced thereby and improves the detection efficiency.

Description of drawings

1 is a schematic structural diagram of a microstructure topography measuring device based on spectral modulation depth coding provided by an embodiment of the present invention;

Fig. 2 is a "spectrum-depth" relationship curve provided by an embodiment of the present invention;

FIG. 3 is a “spectrum-modulation degree” relationship curve provided by an embodiment of the present invention.

Among them: 1. Broad spectrum light source; 2. Beam coupler; 3. Spectral modulation gating device; 4. Homogeneous light coupler; 5. Beam bending coupler; 6. Spatial light modulator; 7. Collimating beam expansion Lens; 8. Beam splitter; 9. Axial non-achromatic microscope objective; 10. Component under test; 11. Stage; 12. Imaging lens; 13. Color camera; 14. Data transmission control line; 15. Computer; 16. Controller.

Detailed ways

A microstructure topography measuring device and method based on spectral modulation depth coding according to the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

Example 1

Referring to FIG. 1 , it is a schematic structural diagram of a microstructure topography measuring device based on spectral modulation depth coding provided in this embodiment. The measuring device is composed of a wide-spectrum light source 1, a beam coupler 2, a spectral modulation gate 3, a uniform light coupler 4, a beam-reversing coupler 5, a spatial light modulator 6, a collimating beam expanding lens 7, and a beam splitter 8. An axial non-achromatic microscope objective lens 9 , a stage 11 , an imaging lens 12 , a color camera 13 , a data transmission control line 14 , a computer 15 , and a controller 16 are composed.

The polychromatic light emitted by the wide-spectrum light source 1 is uniformly incident on the spectral modulation gate 3 through the beam coupler 2, and the spectral modulation gate 3 sequentially outputs monochromatic light of a specific wavelength within the measurement spectral range, and passes through the uniform light coupler. 4 and the beam refraction coupler 5 to obtain a uniformly distributed incident monochromatic light field signal, which is incident to the spatial light modulator 6; the spatial light modulator 6 is located at the front focal plane of the collimating beam expander lens 7, and the controller The coded image output end of 16 is connected to the spatial light modulator 6, and the spatial light modulator 6 outputs a spatially coded monochromatic sinusoidal fringe light field signal, which is then coupled to the collimating beam expander lens 7 by the beam refracting coupler 5 to become parallel light. Incident on the surface of the beam splitter 8; the beam splitter 8 reflects the parallel monochromatic sine fringe light into the axial non-achromatic microscope objective 9, and then irradiates the surface of the measured element 10 on the stage 11, and is reflected by the measured surface The returned monochromatic sinusoidal stripe light passes through the axial non-achromatic microscope objective 9 and the beam splitter 8 in turn, and is coupled to the target surface of the color camera 13 through the imaging lens 12, and the color camera 13 transmits the collected image data to the computer. . The position of the stage 11 can be changed in the axial and radial directions, so that the measured element 10 and the spatial light modulator 6 on it are conjugated to the object image at the central wavelength in the spectral range used for the measurement; the beam is refracted and coupled 5, spatial light modulator 6, collimating beam expander lens 7, beam splitter 8, axial non-achromatic microscope objective 9, imaging lens 12 and color camera 13 are in a common optical path structure; The control line 14 is connected with the controller 16 and the color camera 13, and uses the Visual C++ 2010-based compiler programming to realize the regulation of the output light field signal of the spectral modulation gate 3 and the spatial light modulator 6, and to collect and transmit image data for the camera 13. synchronization control.

In this embodiment, the spectral modulation gate 3 is an acousto-optic modulator (AOTF), which can control the polychromatic light and output monochromatic light of specific wavelengths in sequence; the spatial light modulator 6 is a digital micromirror device ( DMD), which can realize the modulation of the spatial distribution of the incident light field; the axial non-achromatic microscope objective 9 can focus the monochromatic parallel light of different wavelengths at different depth positions along the axial direction; the wide-spectrum light source 1 is a halogen lamp, white light LED or supercontinuum laser; beam coupler 2 is a structural device composed of lenses, mirrors or optical fibers; uniform light coupler 4 is an integrating sphere or integrating rod; beam refraction coupler 5 is total internal reflection (total internal reflection, TIR) prism; the beam splitter 8 is a 1:1 transflective beam splitter prism; the color camera 13 is a color three-chip CCD camera; the spectral range used for the measurement is the ultraviolet band, the visible light band or the infrared band.

Using the device shown in FIG. 1, the present embodiment provides a method for measuring the topography of a microstructure based on spectral modulation depth coding, which includes the following three steps:

The first step is to pre-calibrate the system. Before measurement, it is necessary to pre-calibrate the "spectrum-depth" correspondence of the system device:

1) Use the spectral modulation gate 3 to gate and filter the polychromatic light emitted by the wide-spectrum light source 1, output monochromatic light of a specific wavelength, and uniformly irradiate it to the space light through the uniform light coupler 4 and the beam deflection coupler 5 modulator 6;

2) Using the software based on Visual C++ 2010 compiler programming, the spatial light modulator 6 is synchronously controlled to output a uniformly distributed monochromatic light signal, and the beam is deflected through the beam reversing coupler 5, collimating beam expanding lens 7, and beam splitter 8 and the axial non-achromatic microscope objective 9 illuminates the standard plane mirror on the stage;

3) Driven by the piezoelectric ceramic microdisplacer, the standard plane mirror performs axial scanning along the optical axis of the microscope objective 9, and reflects the monochromatic light signal into the axial non-achromatic microscope objective 9 and splits the beam. 8, the spectrometer receives and measures the wavelength value of the optical signal, and records the axial movement position of the piezoelectric ceramic microdisplacer when the monochromatic optical signal reaches the peak value during the scanning process;

4) In the spectral range used for measurement, repeat the above process along the short-wave to long-wave direction (or reverse) to obtain a set of "spectrum-depth" data, and use polynomial or spline fitting technology to determine the "spectrum-depth" of the system device. ” relationship curve to complete the system pre-calibration.

Since monochromatic parallel light with different wavelengths passes through the axial non-achromatic microscope objective 9, it will be focused at different axial depth positions in a one-to-one correspondence, that is, there is a correspondence between "spectrum-depth" as shown in the following formula (1). relation:

z = f (λ) (1)

where f (•) is a single-valued function and z is the axial depth. Referring to FIG. 2 , the “spectrum-depth” relationship curve provided by the embodiment of the present invention, the horizontal axis represents the wavelength domain λ (from left to right, the short-wave to long-wave direction), and the vertical axis is the depth z . Due to the influence of factors such as the adjustment error of optical components, nonlinear axial dispersion, etc., there is often a nonlinear correspondence between "spectrum-depth". Polynomial or spline fitting techniques can be used in the calibration process of the measurement system device. A more precise characterization leads to the single-valued function f (•).

The second step is to acquire the encoded image. During measurement, adjust the position of the stage 11 in the axial and radial directions so that the measured element 10 and the spatial light modulator 6 located thereon are in the center of the spectral range (ultraviolet, visible or infrared) used for the measurement The object image is conjugated at the wavelength; the polychromatic light emitted by the wide-spectrum light source 1 is filtered along the short-wave to long-wave direction (or reverse) by the spectral modulation gate 3, and the monochromatic light of a specific wavelength is sequentially output, and the uniform light is obtained. The coupler 4 and the beam-reflecting coupler 5 are uniformly incident on the spatial light modulator 6; the spatial light modulator 6 is synchronously controlled by the software developed based on the Visual C++ 2010 compiler, and the corresponding monochromatic phase-shifted sinusoidal fringe pattern light field signal is output in turn , and then irradiated to the surface of the measured element 10 through the beam refraction coupler 5, the collimating beam expanding lens 7, the beam splitter 8 and the axial non-achromatic microscope objective 9; the color camera 13 cooperates with the controller 16 to collect Each frame of the monochromatic phase-shift fringe pattern reflected by the element under test 10 is transmitted to the computer 15 for storage and processing;

In this embodiment, the adopted method is based on the traditional three-dimensional topography measurement method based on fringe modulation degree coding, using monochromatic parallel light of different wavelengths to pass through the axial non-achromatic microscope objective lens 9 in a one-to-one correspondence Focusing on different axial depth positions, and the modulation degree of each monochromatic light stripe varies with the axial depth and reaches a maximum value at its focal plane position (that is, the depth position of the point to be measured), realizing the “modulation degree—spectrum— Depth" unique encoding among the three.

Specifically: based on the equal-step phase-shifting technology in the time domain, by changing the light field intensity distribution of the spatial light modulator 6, and using the wide-spectrum light source 1, the beam coupler 2, the uniform light coupler 4 and the beam deflection coupler 5 , the output of the monochromatic phase-shifted sinusoidal fringe pattern light field signal is sequentially realized from the short-wave to the long-wave direction (or reverse) in the spectral range used for the measurement. The light intensity distribution of each frame of the monochromatic phase-shift fringe pattern reflected by the measured element 10 collected by the color camera 13 is shown in formula (2):

(2)

(2)

是与被测元件10的三维面形分布相关的条纹相位，

表示第m个单色光的中心波长，

，M为测量所用光谱范围内（紫外波段、可见光波段或红外波段）单色光的数目（在本实施例中M =30），

和

分别表示第m个单色光条纹图的背景分量和调制度分布，

为第n步的移相量，

，

，N为相移步数（在本实施例中N= 4）。因“光谱—深度”之间具有如式(1)所示的对应关系，故彩色相机13获得的各帧单色移相条纹图光强分布可表示为如下式（3）：Among them, ( x, y ) are the image coordinates on the target surface of the color camera 13,

is the fringe phase related to the three-dimensional surface distribution of the component under test 10,

represents the central wavelength of the mth monochromatic light,

, M is the number of monochromatic light in the spectral range (ultraviolet band, visible light band or infrared band) used for measurement ( M =30 in this embodiment),

and

represent the background component and modulation degree distribution of the mth monochromatic light fringe pattern, respectively,

is the phasor of the nth step,

,

, N is the number of phase shift steps ( N =4 in this embodiment). Since there is a corresponding relationship between “spectrum-depth” as shown in formula (1), the light intensity distribution of each frame of monochromatic phase-shift fringe pattern obtained by the color camera 13 can be expressed as the following formula (3):

(3)

(3)

为单值函数

的反函数，

为第m个单色光中心波长

对应的轴向深度。由于各单色光条纹的调制度会随轴向深度而变化，且在其焦面位置附近达到极大值。故被测元件10上任意一点所对应的波长域上条纹调制度的极大值位置即为该点的深度编码光谱信息，从而实现了“光谱——调制度——深度”三者间的唯一性编码。in,

is a single-valued function

the inverse function of ,

is the central wavelength of the mth monochromatic light

corresponding axial depth. Because the modulation degree of each monochromatic light fringe varies with the axial depth, and reaches a maximum value near its focal plane position. Therefore, the maximum value position of the fringe modulation degree in the wavelength domain corresponding to any point on the measured element 10 is the depth-encoded spectral information of the point, thus realizing the uniqueness among the three “spectrum-modulation-depth”. Sexual coding.

；基于高斯、类高斯或样条模型拟合确定待测面上各点的“光谱—调制度”关系曲线，利用各单色光条纹调制度在其焦面位置（即待测点的深度位置）达到极大这一特性，解调出各点的深度编码光谱信息

；再结合第一步预先标定获得的“光谱—深度”关系曲线

，解调出对应的待测面上各点的深度信息，最终完成被测元件10三维形貌分布的无机械式扫描、全场非接触的快速高精度测量。The third step is to demodulate the coded image. The obtained monochromatic phase-shift fringe patterns are processed by the random phase-shifting algorithm, and the modulation degree distribution of each monochromatic light fringe pattern related to the surface shape of the DUT 10 is obtained.

;Based on Gaussian, Gaussian-like or spline model fitting to determine the "spectrum-modulation" relationship curve of each point on the test surface, using the modulation degree of each monochromatic light fringe at its focal plane position (that is, the depth position of the test point ) reaches the maximum characteristic, and demodulates the depth-coded spectral information of each point

; Combined with the "spectrum-depth" relationship curve obtained from the pre-calibration in the first step

, demodulate the depth information of each point on the corresponding surface to be measured, and finally complete the fast and high-precision measurement of the three-dimensional topography distribution of the measured component 10 without mechanical scanning and full-field non-contact.

，即可得到该点的深度（高度）信息z ₁。Referring to FIG. 3 , the “spectrum-modulation degree” relationship curve B (λ) of a certain point on the measured element 10 provided by the embodiment of the present invention, the horizontal axis represents the wavelength domain λ (from left to right is the short-wave to long-wave direction ), the ordinate is the normalized fringe modulation degree. In the demodulation process, B (λ) is determined based on Gaussian, Gaussian _- like or spline model fitting, so that the spectral position λ1 corresponding to the maximum value of the curve can be obtained. , combined with the "spectrum-depth" relationship curve

, the depth (height) information z ₁ of the point can be obtained.

Claims (7)

1. A microstructure topography measuring device based on spectral modulation depth coding, characterized in that: it comprises a wide-spectrum light source (1), a beam coupler (2), a spectral modulation gate (3), a uniform light coupling (4), beam refracting coupler (5), spatial light modulator (6), collimating beam expander lens (7), beam splitter (8), axial non-achromatic microscope objective lens (9), Stage (11), imaging lens (12), color camera (13), data transmission control line (14), computer (15) and controller (16); computer (15) via data transmission control line (14) are respectively connected with the controller (16) and the color camera (13); the component under test (10) is placed on the stage (11), and the component under test (10) and the spatial light modulator (6) are measuring the spectrum used The object image is conjugated at the center wavelength of the range; beam-reversing coupler (5), spatial light modulator (6), collimating beam expander lens (7), beam splitter (8), axial non-achromatic display A common optical path structure is formed between the micro-objective lens (9), the imaging lens (12) and the color camera (13); the polychromatic light emitted by the wide-spectrum light source (1) is uniformly incident on the spectral modulation gate (2) through the beam coupler (2). 3), the spectral control output end of the controller (16) is connected to the spectral modulation gate (3), and the spectral modulation gate (3) sequentially outputs monochromatic light of a specific wavelength in the spectral range for measurement, The optical coupler (4) and the beam deflection coupler (5) obtain a uniformly distributed incident monochromatic light field signal, which is incident on the spatial light modulator (6); the spatial light modulator (6) is located at the The position of the front focal plane of the straight beam expander lens (7), the coded image output end of the controller (16) is connected to the spatial light modulator (6), and the spatial light modulator (6) outputs a spatially coded monochromatic sinusoidal fringe light field The signal is then coupled to the collimating beam expander lens (7) by the beam refracting coupler (5) to become parallel light incident on the surface of the beam splitter (8); the beam splitter (8) converts the parallel monochromatic sinusoidal stripe light After being reflected into the axial non-achromatic microscope objective (9), it is irradiated to the surface of the measured element (10), and the monochromatic sinusoidal fringe light reflected back by the measured surface passes through the axial non-achromatic microscope objective (9) in turn. ) and a beam splitter (8) are coupled to the target surface of a color camera (13) via an imaging lens (12), and the color camera (13) transmits the collected image data to a computer. 2 . The microstructure topography measuring device based on spectral modulation depth coding according to claim 1 , wherein the spectral modulation gate is an acousto-optic modulator. 3 . 3 . The microstructure topography measuring device based on spectral modulation depth coding according to claim 1 , wherein the spatial light modulator is a digital micromirror device or a liquid crystal on silicon. 4 . 4 . The microstructure topography measuring device based on spectral modulation depth coding according to claim 1 , wherein the wide-spectrum light source is a halogen lamp, a white light LED or a supercontinuum laser. 5 . 5 . The microstructure topography measuring device based on spectral modulation depth coding according to claim 1 , wherein the color camera is a color three-chip CCD or CMOS camera. 6 . 6. A method for measuring microstructure topography based on spectral modulation depth coding, characterized in that it comprises the steps: The first step, the pre-calibration of the "spectrum-depth" correspondence: (1) The polychromatic light emitted by the wide-spectrum light source is gated and filtered by the spectral modulation gating device, and the monochromatic light of a specific wavelength is output, which is uniformly irradiated to the spatial light modulator through the uniform light coupler and the beam deflection coupler; (2) Synchronously control the spatial light modulator to output a uniformly distributed monochromatic light signal, which is irradiated to the object through a beam-refracting coupler, a collimating beam expanding lens, a beam splitter and an axial non-achromatic microscope objective. Standard flat mirror on stage; (3) Driven by the piezoelectric ceramic microdisplacer, the standard plane mirror performs axial scanning along the optical axis of the microscope objective, and reflects the monochromatic light signal into the axial non-achromatic microscope objective and beam splitter , and then receive and measure the wavelength value of the optical signal by the spectrometer, and record the axial movement position of the piezoelectric ceramic microdisplacer when the monochromatic optical signal reaches the peak value during the scanning process; (4) Repeat steps (1) to (3) along the short-wave to long-wave direction or in the reverse direction within the spectral range used for the measurement to obtain a set of "spectrum-depth" data, and use polynomial or spline fitting methods to obtain "spectrum" - depth" corresponding relationship curve, complete the pre-calibration; The second step, coded image acquisition: place the component under test on the stage, and adjust the position of the stage along the axial and radial directions so that the center wavelength of the component under test and the spatial light modulator is within the spectral range used for measurement The object image is conjugated below; the polychromatic light emitted by the wide-spectrum light source is filtered along the short-wave to long-wave direction or in the reverse direction by the spectral modulation gate, and the monochromatic light of the specific wavelength is sequentially output, and the light is passed through the uniform light coupler and the beam. The refracting coupler is uniformly incident on the spatial light modulator; the spatial light modulator is synchronously controlled, and the corresponding monochromatic phase-shifted sinusoidal fringe pattern light field signal is output in turn, and then the beam refracting coupler, collimating beam expanding lens, and beam splitter and the axial non-achromatic microscope objective lens is irradiated to the surface of the component under test; the controller controls the color camera to synchronously collect each frame of monochromatic phase-shift fringe pattern reflected by the component under test, and transmit it to the computer for storage and processing; The third step is to demodulate the coded image: use the random phase-shift algorithm to process the obtained monochromatic phase-shift fringe patterns, and obtain the modulation degree distribution of each monochromatic light fringe pattern related to the surface shape of the tested object; Gauss-like or spline model fitting determines the "spectrum-modulation" relationship curve of each point on the surface to be measured, and demodulates the depth-coded spectral information of each point; according to the "spectrum-depth" relationship obtained by pre-calibration in the first step Curve, demodulate to obtain the depth information of each point on the corresponding surface to be measured, and obtain the microstructure morphology of the measured component. 7 . The method for measuring microstructure topography based on spectral modulation depth coding according to claim 6 , wherein the spectral range used for the measurement is an ultraviolet waveband, a visible light waveband or an infrared waveband. 8 .

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