Roughness information coupling microstructure surface dual-wavelength digital holographic detection method

Abstract

The invention belongs to the technical field of digital holographic detection and bionic microstructure detection, and discloses a roughness information coupling microstructure surface multi-wavelength digital holographic measurement method. The method comprises the following steps: respectively establishing a three-dimensional model coupled with roughness information and a reference object model, and importing the three-dimensional model coupled with the roughness information and the reference object model into ZEMAX software; a digital holographic simulation light path is established in a non-sequence mode of ZEMAX software, the three-dimensional model of the coupling roughness information and the reference object model are respectively arranged in the digital holographic simulation light path for ray tracing, and holograms of the three-dimensional model of the coupling roughness information and the reference object model are obtained by changing the light wavelength; and establishing a dual-exposure dual-wavelength digital holographic reconstruction algorithm in MATLAB software, respectively reading and reconstructing holograms of the three-dimensional model coupled with the roughness information and the reference object model, and recovering the three-dimensional shape of the roughness information model.

Description

Technical Field

[0001] The present invention relates to the technical fields of digital holographic detection and bionic microstructure detection, and particularly relates to a dual-wavelength digital holographic detection method for a microstructure surface coupling roughness information. Background Art

[0002] Digital holographic detection technology has advantages such as high precision, non-contact, and real-time measurement. Compared with single-wavelength digital holographic detection technology, dual-wavelength digital holographic detection technology has a wider longitudinal measurement range. The size of a microstructure surface with roughness information generally exceeds the detectable range of single-wavelength digital holographic detection technology. Therefore, dual-wavelength digital holographic detection technology is more suitable for detecting microstructures with roughness information.

[0003] The construction of a dual-wavelength digital holographic optical path has always been a difficult problem. The dual-exposure dual-wavelength digital holographic optical path is severely affected by the environment due to the need for two exposures. The single-exposure dual-wavelength digital holographic optical path requires the simultaneous construction of two optical paths, and the complexity of its optical path increases linearly compared with the single-wavelength digital holographic optical path. The construction difficulty is very high and it is also affected by the environment. There are problems such as difficult measurement and low measurement accuracy when measuring the surface of a microstructure with roughness information. Summary of the Invention

[0004] The purpose of the present invention is to provide a dual-wavelength digital holographic detection method for a microstructure surface coupling roughness information, so as to solve the problems of large construction difficulty, being affected by the environment, difficult measurement, and low measurement accuracy when measuring the surface of a microstructure with roughness information.

[0005] To achieve this purpose, the present invention adopts the following technical solutions:

[0006] A dual-wavelength digital holographic detection method for a microstructure surface coupling roughness information, the method comprising the following steps:

[0007] Respectively establish a three-dimensional model coupling roughness information and a reference object model, and import the three-dimensional model coupling roughness information and the reference object model into ZEMAX software;

[0008] Establish a digital holographic simulation optical path in the non-sequential mode of the ZEMAX software, respectively set the three-dimensional model coupling roughness information and the reference object model into the digital holographic simulation optical path for ray tracing, and obtain holograms of the three-dimensional model coupling roughness information and the reference object model by changing the optical wavelength;

[0009] Establish a dual-exposure dual-wavelength digital holographic reconstruction algorithm in MATLAB software, respectively read the holograms of the three-dimensional model coupling roughness information and the reference object model and reconstruct them to restore the three-dimensional morphology of the roughness information model.

[0010] Preferably, the steps of the three-dimensional model coupling roughness information include:

[0011] Use COMSOL simulation software to establish a two-dimensional rough surface and set surface parameters respectively;

[0012] Set the height value according to the actual application, adjust the position in the coordinate system to form a three-dimensional step model coupling roughness information;

[0013] Convert the three-dimensional step model coupling roughness information into STL or STEP format for export, and realize the creation of the three-dimensional model of the coupling roughness information.

[0014] Preferably, the steps of establishing the digital holographic simulation optical path include:

[0015] Model the laser model, laser beam expander model, beam splitter model, mirror model, object model, and camera model;

[0016] Modify the value of the wavelength used in the current simulation experiment.

[0017] Preferably, the laser model refers to a solid-state laser with an elliptical light spot, and the number of light rays is set to 300 million.

[0018] Preferably, the structure of the laser beam expander model is a plano-concave lens and a plano-convex lens; the beam expansion ratio M of the laser beam expander is:

[0019]

[0020] where, the focal length of the plano-concave lens is f1 and the focal length of the plano-convex lens is f2.

[0021] Preferably, the laser beam expander model includes two first rectangular detectors and a second rectangular detector arranged behind the laser beam expander, and the calculation formula of the divergence angle θ is as follows:

[0022]

[0023] where, the distance between the two rectangular detectors is D, and the sizes of the light spot diameters measured by the two rectangular detectors are D1 and D2 respectively.

[0024] The beneficial effects of the present invention: The micro-structure surface dual-wavelength digital holographic detection method coupling roughness information of the present invention starts from the perspective of simulation, uses ZEMAX software to simulate the whole process of detecting the micro-structure surface with roughness information by dual-wavelength digital holographic technology, and thus has guiding significance for the device selection, construction of the actual optical path, and establishment of the subsequent image reconstruction algorithm for image processing. Description of the Drawings

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for the description of the embodiments of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained according to the content of the embodiments of the present invention and these drawings.

[0026] Figure 1 is the flowchart of the dual-wavelength digital holographic detection method for a microstructured surface coupling roughness information of the present invention;

[0027] Table 1 Parameters of the object model coupling roughness information;

[0028] Figure 2 is the modeling diagram of the simulation optical path of the dual-wavelength digital holography for a microstructured surface coupling roughness information of the present invention;

[0029] Figure 3 is the principle diagram of the optimization of the laser beam expander model in the simulation optical path of the dual-wavelength digital holography for a microstructured surface coupling roughness information of the present invention;

[0030] Figure 4 is the structural diagram of the laser beam expander model in the simulation optical path of the dual-wavelength digital holography for a microstructured surface coupling roughness information of the present invention.

[0031] In the figure: 1. Laser model, 2. Laser beam expander model, 201. Plano-concave lens, 202. Plano-convex lens, 203. First rectangular detector, 204. Second rectangular detector, 3. First beam splitter model, 4. Mirror model, 5. Second beam splitter model, 6. Object model, 7. Third beam splitter model, 8. Fourth beam splitter model, 9. Camera model. Detailed implementation manners

[0032] The following further elaborates on the present invention in conjunction with the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. Additionally, it should be noted that for the sake of description, only the parts related to the present invention are shown in the drawings, rather than all the structures.

[0033] In the description of the present invention, unless otherwise clearly defined and limited, the terms "connected", "connected to", and "fixed" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0034] In the present invention, unless otherwise clearly specified and defined, the first feature being "on" or "under" the second feature may include direct contact between the first and second features, or may include the first and second features not being in direct contact but in contact through additional features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes the first feature being directly above and obliquely above the second feature, or merely indicating that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "beneath" and "underneath" the second feature includes the first feature being directly below and obliquely below the second feature, or merely indicating that the horizontal height of the first feature is less than that of the second feature.

[0035] In the description of this embodiment, the orientation or positional relationships such as "upper", "lower", "left", "right", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of description and simplifying the operation, 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 thus cannot be construed as a limitation to the present invention. In addition, the terms "first" and "second" are only used for distinction in description and have no special meaning.

[0036] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the drawings, in which the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present invention and should not be construed as a limitation to the present invention.

[0037] As Figure 1 shown, the present invention provides a dual-wavelength digital holographic detection method for a microstructured surface coupled with roughness information. First, a model of the object to be measured coupled with roughness information is established, specifically including: in the COMSOL software, as shown in Table 1, a two-dimensional rough surface is established, which is respectively the length r w of the rough surface, the width r h of the rough surface, the roughness S q of the rough surface, the spectral index beta and the spatial frequency resolution N to set the roughness information of the rough surface. The spectral index beta mainly affects the texture of the rough surface. When its value is large, a rough surface with a rougher texture will be created. On the contrary, when its value is small, a rough surface with a finer texture and higher detail accuracy will be created. The magnitude of the spatial frequency resolution N will affect the creation time of the rough surface. The larger its value, the longer the time to create the rough surface, which also means that the rough surface is more refined.

[0038] Table 1 Parameters of the object model to be measured coupled with roughness information

[0039]

[0040] After establishing the two-dimensional rough surface, a three-dimensional model block also needs to be established to perform a union operation with the rough surface and emboss the model of the rough surface. The length and width of the three-dimensional model block are set the same as the length and width parameters of the two-dimensional rough surface, and the height is set according to the actual situation. In this embodiment, it is set as a rectangular block with a height of 1 cm. If the position of the established two-dimensional rough surface is not adjusted, its center is at the origin of the xyz coordinate axes, while for the three-dimensional model block, the starting point of its height is at -1 on the Z axis. If the unit is centimeter, then the starting position of the Z axis of the three-dimensional model block is at -1 cm. Therefore, adjust the position of the three-dimensional model block in the positive Z-axis direction by an adjustment value of 0.5 cm to make the two-dimensional rough surface located within the three-dimensional model block. Through the operations of taking the union and deleting objects in the COMSOL software, delete the model on the two-dimensional rough surface, and finally obtain a three-dimensional model block with a coupled roughness of 0.5 cm in height.

[0041] Secondly, establish a reference object model. The length, width, and height of the reference object model are the same as those of the measured object model with coupled roughness information. Convert the reference object model and the measured object model with coupled roughness information into STL or STEP format and export them to complete the creation operation of the entire object model 6.

[0042] Establish a double-exposure dual-wavelength digital holographic optical path simulation model. The specific steps include: as Figure 2 shown, model the laser model 1, the laser beam expander 2 model, the first beam splitter 3 model, the mirror model 4, the second beam splitter model 5, the object model 6, the third beam splitter model 7, the fourth beam splitter model 8, and the camera model 9; establish an optical path using ZEMAX software. The specific operations for realizing dual-wavelength digital holographic measurement are as follows: in the simulation experiment environment, in the wavelength parameter setting list under the system option list in the non-sequential mode, modify the value of the wavelength used in the current simulation experiment to obtain holograms of the measured object model and the reference object model with coupled roughness information at different wavelengths. Use two lasers with different wavelengths to record the holograms of the measured object model and the reference object model with coupled roughness information, and through the processing of the holograms and the reconstruction of the three-dimensional morphology of the measured object, realize the process of simulating dual-wavelength digital holographic interference.

[0043] Laser model 1 is modeled. According to the size of the physical laser, a three-dimensional model of the laser is established, and the light source type, position, spot diameter, number of analysis light lines and light source position of laser model 1 are set. The actual laser referenced in this embodiment is a solid laser, and the spot is set to an elliptical spot. When the number of light lines is small, the obtained hologram is not clear and contains more noise. Although the entire simulation time is short, it cannot be used for subsequent reconstruction; when the number of light lines is large, the obtained hologram is clear and the noise is greatly reduced. The hologram can be used for subsequent reconstruction processing operations, but the entire simulation time is too long. Based on the comprehensive consideration of the requirements for subsequent processing of the hologram and the length of time the simulation model takes, the number of light lines finally selected is 300 million.

[0044] Laser beam expander model 2 is modeled as follows: Figure 3 As shown, the laser beam expander model 2 is composed of a plano-concave lens 201 and a plano-convex lens 202. Its beam expansion ratio is related to the focal lengths of the two lenses. Assuming that the focal length of the plano-concave lens is f1 and the focal length of the plano-convex lens is f2, the beam expansion ratio M of the laser beam expander is:

[0045]

[0046] The formula for the focal length of a single lens is as follows:

[0047]

[0048] Where f is the focal length of the lens, n is the refractive index of the lens material, and R T is the radius of curvature of the lens surface, R 1T is the radius of curvature of the concave lens surface, R 2T is the radius of curvature of the convex lens surface. For a plano-concave lens or a plano-convex lens, one side of the lens is a plane, and the radius of curvature can be understood as an infinitely large plane, so the focusing formula of the above single lens can be written as follows:

[0049]

[0050] According to the beam expansion ratio requirement of the optical path design, the beam expansion ratio of the laser beam expander is M. A set of concave lenses and convex lenses that meet the focal length requirements is found. The refractive index of the materials of the concave lenses and convex lenses of the focal length is consulted and substituted into the focal length formula of the deformed single lens. The radius of curvature of the non-planar side of the plano-concave lens 201 or the plano-convex lens 202 is calculated, and then the concave lens and convex lens models are established. Two first rectangular detectors 203 and second rectangular detectors 204 are placed behind the laser beam expander. The distance between the two rectangular detectors is D. The spot diameters measured by the two rectangular detectors are D1 and D2 respectively. The distance L between the two lenses is adjusted according to the spot diameter on the rectangular detectors, and then the divergence angle θ of the laser beam expander is adjusted. The calculation formula of the divergence angle θ is as follows:

[0051]

[0052] When the divergence angle θ is less than or equal to the set divergence angle, the laser beam expander optimization is completed.

[0053] Modeling of the beam splitter, establishing a model of the size of the existing physical beam splitter in ZEMAX software. The beam splitter model is composed of two right-angled prisms. Enter the two right-angled prisms in the data editing bar of ZEMAX software, and adjust the angles of the right-angled prisms to form a cubic beam splitter as Figure 4 shown. Enter the material, scaling factor, position, and coating parameters of the beam splitter model. Coat an antireflection film on the 0 surface of the beam splitter cube. The 0 surface includes four surfaces 301ADHE, 302ABCD, 303BCGF, and 305EFGH. Specifically, Figure 4 the upper and lower surfaces and the left and right surfaces in the beam splitter cube in . The purpose of coating the antireflection film is to reduce the reflection of light. Coat the film layer with the required splitting ratio on the beam splitting surface 304ADGF where the two right-angled prisms are in contact. Generally, the splitting ratio of the coated film layer is 1:1, so that the reflectivity and transmittance of the film layer are 1:1.

[0054] Modeling of the mirror model 4. The mirror model 4 is approximated by a standard surface in ZEMAX software. Therefore, select the standard surface entity in the ZEMAX data editing bar and coat the reflective film layer.

[0055] Modeling of the camera model 9. Build the shell part that plays a supporting and fixing role and the photosensitive element part that uses a rectangular detector to replace the light-receiving part according to the actual parameters. Fill in the parameters of the rectangular detector in the ZEMAX data editing bar: the half-width in the X direction, the half-width in the Y direction, the pixel size, and the position of the detector.

[0056] After building all the models, simulate the laser emitted by the laser model 1 in ZEMAX software. After passing through the laser beam expander model 2, the spot diameter is enlarged. After passing through the first beam splitter model 3, the laser is split into two beams of light, one is O1 and the other is R1. O1 propagates to the right to the third beam splitter model 7 and is split into two beams by the third beam splitter model 7, one is O2 and the other is W. O2 propagates upward to the object model 6, and then after being reflected by the object surface, it propagates downward and returns to the third beam splitter model 7 and is split into two beams of light, one of which is O3 and the other is W. O3 continues to propagate downward to the fourth beam splitter model 8 and is split into two beams of light, one is O4 and the other is W. O4 continues to propagate downward to reach the camera model 9 to form the object light required for the final interference.

[0057] R1 is split by the first beam splitter model 3, then propagates downward to the mirror model 4. After being reflected by the mirror model 4, it propagates to the second beam splitter model 5 and is split into two beams of light, one is R2 and the other is W. R2 continues to propagate to the right and reaches the fourth beam splitter model 8, where it is split into two beams of light, one is R3 and the other is W. R3 continues to propagate downward and reaches the camera model 9 to form the reference light required for the final interference. The object light and the reference light interfere on the image plane of the camera model 9 to form a hologram.

[0058] The hologram is imported into Matlab software and reconstructed using the dual-wavelength reconstruction algorithm to further restore the three-dimensional shape of the object under test.

[0059] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limiting the implementation manners of the present invention. For those of ordinary skill in the art, various obvious changes, re-adjustments and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to enumerate all the implementation manners here. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A dual-wavelength digital holographic detection method for microstructure surface coupled with roughness information, characterized in that: The method comprises the following steps: Establishing a three-dimensional model of coupled roughness information and a reference object model respectively, and importing the three-dimensional model of coupled roughness information and the reference object model into ZEMAX software; Establishing a digital holographic simulation optical path in the non-sequential mode of the ZEMAX software, respectively setting the three-dimensional model of the coupled roughness information and the reference object model to the digital holographic simulation optical path for ray tracing, and obtaining holograms of the three-dimensional model of the coupled roughness information and the reference object model by changing the wavelength of light; A double-exposure dual-wavelength digital holographic reconstruction algorithm is established in MATLAB software, and the holograms of the three-dimensional model of the coupled roughness information and the reference object model are read and reconstructed respectively to restore the three-dimensional morphology of the roughness information model.

2. The dual-wavelength digital holographic detection method for microstructure surface coupling roughness information according to claim 1 is characterized in that: The step of coupling the three-dimensional model of roughness information comprises: Use COMSOL simulation software to create a two-dimensional rough surface and set the surface parameters respectively; Set the height value according to the actual application, adjust the position in the coordinate system, and form a three-dimensional step model with coupled roughness information; The three-dimensional step model of the coupled roughness information is converted into an STL or STEP format and exported to achieve the creation of a three-dimensional model of the coupled roughness information.

3. The dual-wavelength digital holographic detection method for microstructure surface coupling roughness information according to claim 1 is characterized in that: The steps of establishing a digital holographic simulation optical path include: Modeling laser models, laser beam expander models, beam splitter models, mirror models, object models, and camera models; Modify the value of the wavelength used in the current simulation experiment.

4. The dual-wavelength digital holographic detection method for microstructure surface coupling roughness information according to claim 3 is characterized in that: The laser model refers to a solid laser with an elliptical light spot, and the number of light lines is set to 300 million.

5. The dual-wavelength digital holographic detection method for microstructure surface coupling roughness information according to claim 1 is characterized in that: The laser beam expander model structure is a plano-concave lens and a plano-convex lens; the beam expansion ratio M of the laser beam expander is: Among them, the focal length of the plano-concave lens is f1, and the focal length of the plano-convex lens is f2.

6. The dual-wavelength digital holographic detection method for microstructure surface coupling roughness information according to claim 5 is characterized in that: The laser beam expander model includes two first rectangular detectors and a second rectangular detector arranged after the laser beam expander. The calculation formula of the divergence angle θ is as follows: The distance between the two rectangular detectors is D, and the spot diameters measured by the two rectangular detectors are D1 and D2 respectively.

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