Integrated imaging method for surface diffuse reflectance and three-dimensional topography based on oblique stripe patterns

Abstract

The method for integrated imaging of surface diffuse reflectance and three-dimensional topography based on oblique stripe patterns belongs to the technical field of structured light three-dimensional imaging; this method generates cosine oblique stripe patterns with different frequencies, forms cosine oblique stripe images under a fixed light wave on a diffuse reflection plate and a sample respectively, then performs Fourier transform to obtain the image spectrum, and performs filtering and inverse Fourier transform to obtain the spatial domain expression forms of the DC component and the first-order spectrum component, thereby obtaining the surface diffuse reflectance and the wrapped phase corresponding to the image pixel points of the sample surface, unwrapping the wrapped phase to obtain the absolute phase and calculating the three-dimensional coordinates of the sample surface corresponding to the image pixel points, and finally realizing the integrated imaging of the surface diffuse reflectance and three-dimensional topography of the sample; compared with the traditional Fourier transform three-dimensional imaging method using positive stripe patterns, the present invention improves the measurement accuracy of the three-dimensional coordinates of the sample surface, realizes the measurement of the surface diffuse reflectance of the sample, and further realizes the integrated imaging of the diffuse reflectance and three-dimensional topography.

Description

Technical Field:

[0001] The method for integrated imaging of surface diffuse reflectance and three-dimensional topography based on oblique stripe patterns of the present invention belongs to the technical field of structured light three-dimensional imaging. Background Art:

[0002] The structured light three-dimensional imaging method based on digital stripe projection is a modern optical imaging method applied to the precise measurement and positioning of spatial geometric dimensions. It has the advantages of non-contact, high accuracy, and high efficiency, and is widely used in many fields such as industrial inspection, reverse engineering, virtual reality, and biomedicine. As a typical structured light three-dimensional imaging method, the Fourier transform three-dimensional imaging method can achieve three-dimensional surface topography imaging by projecting only a few or even one stripe pattern, and is the most real-time in principle. Therefore, it is particularly suitable for occasions with high real-time requirements such as dynamic three-dimensional imaging and online three-dimensional imaging. The Fourier transform three-dimensional imaging method needs to perform Fourier transform, filtering, and inverse transform on the stripe image to achieve three-dimensional imaging. The three-dimensional topography of the measured surface is only characterized by the first-order spectral component of the stripe image. However, currently, the Fourier transform three-dimensional imaging method generally projects a cosine positive stripe pattern, and can only perform one-dimensional segmentation and extraction on the cosine positive stripe image, resulting in poor quality of the first-order spectral component extraction, and ultimately leading to low measurement accuracy of the three-dimensional coordinates of the measured surface.

[0003] The diffuse reflectance of the sample surface, as a physical quantity characterizing the properties of the sample, is an important optical index. Currently, the integrating sphere method is generally used to measure diffuse reflectance. This method overcomes the influence of random factors in diffuse reflectance measurement through the integrating sphere, improving the stability and repeatability of the measurement. However, the integrating sphere method can only achieve single-point diffuse reflectance measurement, cannot achieve diffuse reflectance imaging of the sample surface, and the measurement equipment is expensive. Summary of the Invention:

[0004] In order to improve the measurement accuracy of the three-dimensional coordinates of the sample surface and simultaneously realize the function of diffuse reflectance imaging of the sample surface, the present invention discloses a method for integrated imaging of surface diffuse reflectance and three-dimensional topography based on oblique stripe patterns. Compared with the traditional Fourier transform three-dimensional imaging method using positive stripe patterns, the method of the present invention uses oblique stripe patterns to achieve two-dimensional segmentation and extraction of the spectrum of the stripe image, effectively alleviating the aliasing between the first-order spectral component and the zero-order spectral component and the second-order spectral component, effectively improving the quality of the first-order spectral component extraction, and improving the measurement accuracy of the three-dimensional coordinates of the sample surface. The method of the present invention can also measure the diffuse reflectance of the sample surface, and thus realizes the integrated imaging of the diffuse reflectance and three-dimensional topography of the sample surface.

[0005] The object of the present invention is achieved as follows:

[0006] The method for integrated imaging of surface diffuse reflectance and three-dimensional topography based on oblique stripe patterns includes the following steps:

[0007] Step a: The computer generates three two-dimensional cosine skew stripe patterns with different frequencies:

[0008]

[0009]

[0010]

[0011] where (x, y) are the coordinates of the pattern pixel points; I1(x, y) is the pixel intensity of the first two-dimensional cosine skew stripe pattern, I2(x, y) is the pixel intensity of the second two-dimensional cosine skew stripe pattern, and I3(x, y) is the pixel intensity of the third two-dimensional cosine skew stripe pattern; I DC is the average intensity of the two-dimensional cosine stripe pattern; I AC is the modulation intensity of the two-dimensional cosine stripe pattern; and are the frequencies of the two-dimensional cosine skew stripe pattern I1(x, y) along the x-axis and y-axis respectively, and are the frequencies of the two-dimensional cosine skew stripe pattern I2(x, y) along the x-axis and y-axis respectively, and are the frequencies of the two-dimensional cosine skew stripe pattern I3(x, y) along the x-axis and y-axis respectively;

[0012] Step b: The computer controls the horizontally placed projector to vertically project the first cosine skew stripe pattern I1(x, y) in step a onto a standard diffuser with a 98% diffuse reflectance in the visible light band. The optical axis of the CCD camera intersects with the optical axis of the projector to form an angle α. The cosine skew stripe image formed on the standard diffuser is filtered by a filter and then imaged onto the CCD camera to form a cosine skew stripe image under a fixed light wave

[0013]

[0014] where (x0, y0) are the coordinates of the image pixel points; MTF system is the modulation transfer function of the imaging system; R ref is the diffuse reflectance of the standard diffuser, R ref = 0.98; and are the spatial carrier frequencies of the cosine skew stripe image along the x0-axis and y0-axis of the camera image plane coordinate system respectively;

[0015] Step c: The computer controls the horizontally placed projector to sequentially project the three two-dimensional cosine oblique stripe patterns I1(x,y), I2(x,y), and I3(x,y) in Step a vertically onto the surface of the sample to be measured. The spatial depth position of the surface of the sample to be measured is the same as that of the standard diffuse reflection plate. The cosine oblique stripe images formed on the surface of the sample to be measured are filtered by a filter and then imaged onto a CCD camera to form three cosine oblique stripe images under a fixed light wave.

[0016]

[0017]

[0018]

[0019] where (x0,y0) are the coordinates of the image pixel points; MTF system is the modulation transfer function of the imaging system; R(x0,y0) is the diffuse reflectivity of the surface of the sample to be measured corresponding to the image pixel point (x0,y0); and are respectively the spatial carrier frequencies of the cosine oblique stripe image along the x0-axis and y0-axis of the camera image plane coordinate system; and are respectively the spatial carrier frequencies of the cosine oblique stripe image along the x0-axis and y0-axis of the camera image plane coordinate system; and are respectively the spatial carrier frequencies of the cosine oblique stripe image along the x0-axis and y0-axis of the camera image plane coordinate system;

[0020] Step d: Perform two-dimensional Fourier transform on the cosine oblique stripe image in Step b and the cosine oblique stripe images and in Step c to obtain the image spectrum:

[0021]

[0022]

[0023]

[0024]

[0025] where is the two-dimensional Fourier transform operation; Is a cosine oblique stripe image The spectrum after Fourier transform, Is a cosine oblique stripe image The spectrum after Fourier transform, Is a cosine oblique stripe image The spectrum after Fourier transform, Is a cosine oblique stripe image The spectrum after Fourier transform; And Are the spatial frequencies of the cosine oblique stripe image along the x0-axis and y0-axis respectively; Is The first-order spectrum component of, and Is The first-order spectrum component of, and Is The first-order spectrum component of, and Is The first-order spectrum component of, and Is The complex conjugate of, Is The complex conjugate of, Is The complex conjugate of, Is The complex conjugate of;

[0026] Step e, using a two-dimensional frequency-domain low-pass filter to separate and extract the zero-order spectrum components of And In step d And Then perform two-dimensional inverse Fourier transform on And To obtain the cosine oblique stripe images And The DC component MTF system ·R ref ·I DC And MTF system ·R(x0,y0)·I DC ; Then use a two-dimensional frequency-domain band-pass filter to separate and extract the first-order spectrum components of And In step d And Then perform two-dimensional inverse Fourier transform on And To obtain the corresponding spatial domain expression forms And

[0027] Step f: Based on the cosine skew stripe image obtained in step e of the DC component MTF system ·R ref ·I DC and the DC component MTF of the cosine skew stripe image calculate the diffuse reflectance R(x0, y0) of the sample surface corresponding to the image pixel point (x0, y0); system ·R(x0,y0)·I DC

[0028]

[0029] Step g: Based on what is obtained in step e and obtain the wrapped phase of the cosine skew stripe image and where atan{} is the arctangent function; Im[] is the function of taking the imaginary part; Re[] is the function of taking the real part; and

[0030]

[0031]

[0032]

[0033]

[0034] Step h: Based on the wrapped phase obtained in step g and and use the three-frequency time phase unwrapping method based on number theory to unwrap the wrapped phase into the absolute phase φ(x0, y0), and then calculate the three-dimensional coordinates X(x0, y0), Y(x0, y0) and Z(x0, y0) of the sample surface corresponding to the image pixel point (x0, y0) according to the triangulation principle using the absolute phase φ wrapped (x0,y0);

[0035] Step i: Realize the integrated imaging of the diffuse reflectance and three-dimensional topography of the sample surface based on the diffuse reflectance R(x0, y0) of the sample surface obtained in step f and the three-dimensional coordinates X(x0, y0), Y(x0, y0) and Z(x0, y0) of the sample surface obtained in step h.

[0036] Beneficial effects:

[0037] ​​First, compared with the traditional Fourier transform three-dimensional imaging method using positive stripe patterns, the method of the present invention uses oblique stripe patterns to achieve two-dimensional segmentation extraction of the stripe image spectrum, effectively alleviating the aliasing between the first-order spectrum component and the zero-order and second-order spectrum components, effectively improving the extraction quality of the first-order spectrum component, and improving the measurement accuracy of the three-dimensional coordinates of the sample surface.

[0038] Second, the method of the present invention realizes the diffuse reflection measurement of the sample surface through the DC components of the oblique stripe image formed on the standard diffuse reflection plate and the DC components of the oblique stripe image formed on the sample surface.

[0039] Third, the method of the present invention realizes the integrated imaging of the diffuse reflectance and three-dimensional topography of the sample surface. Description of the Drawings:

[0040] Figure 1 Schematic diagram of an integrated imaging system for surface diffuse reflectance and three-dimensional topography based on oblique stripe patterns;

[0041] Figure 2 Cosine oblique stripe image formed on the reference plane photographed by the camera in Experiment 1

[0042] Figure 3 The first cosine oblique stripe image formed on the measured horizontal plane photographed by the camera in Experiment 1

[0043] Figure 4 The second cosine oblique stripe image formed on the measured horizontal plane photographed by the camera in Experiment 1

[0044] Figure 5 The third cosine oblique stripe image formed on the measured horizontal plane photographed by the camera in Experiment 1

[0045] Figure 6 Integrated imaging result of the diffuse reflectance and three-dimensional topography of the measured horizontal plane obtained by the method of the present invention in Experiment 1 (the gray scale in the figure represents the diffuse reflectance value);

[0046] Figure 7 Depth imaging error map of the measured horizontal plane obtained by the traditional Fourier transform three-dimensional imaging method using positive stripe patterns in Experiment 1;

[0047] Figure 8 Depth imaging error map of the measured horizontal plane obtained by the method of the present invention in Experiment 1;

[0048] Figure 9 Diffuse reflectance imaging error map of the measured horizontal plane obtained by the method of the present invention in Experiment 1;

[0049] Figure 10 The cosine oblique stripe image formed on the reference plane photographed by the camera in Experiment 2

[0050] Figure 11 The first cosine oblique stripe image formed on the measured inclined plane photographed by the camera in Experiment 2

[0051] Figure 12 The second cosine oblique stripe image formed on the measured inclined plane photographed by the camera in Experiment 2

[0052] Figure 13 The third cosine oblique stripe image formed on the measured inclined plane photographed by the camera in Experiment 2

[0053] Figure 14 The integrated imaging result of the diffuse reflectivity and three-dimensional topography of the measured inclined plane obtained by the method of the present invention in Experiment 2 (the gray scale in the figure represents the diffuse reflectivity value);

[0054] Figure 15 The depth imaging error map of the measured inclined plane obtained by the traditional Fourier transform three-dimensional imaging method using a positive stripe pattern in Experiment 2;

[0055] Figure 16 The depth imaging error map of the measured inclined plane obtained by the method of the present invention in Experiment 2;

[0056] Figure 17 The diffuse reflectivity imaging error map of the measured plane obtained by the method of the present invention in Experiment 2;

[0057] Wherein: 1 - projector, 2 - CCD camera, 3 - computer, 4 - filter, 5 - standard diffuse reflection plate, 6 - measured sample, 7 - two-dimensional cosine oblique stripe pattern, 8 - cosine oblique stripe image under a fixed light wave. Specific embodiments

[0058] The following further describes in detail the specific embodiments of the present invention with reference to the accompanying drawings. Specific embodiment 1

[0060] The following is the theoretical embodiment of the integrated imaging method for surface diffuse reflectivity and three-dimensional topography based on an oblique stripe pattern of the present invention.

[0061] The integrated imaging method for surface diffuse reflectivity and three-dimensional topography based on an oblique stripe pattern in this specific embodiment includes the following steps:

[0062] Step a, the computer generates 3 two-dimensional cosine oblique stripe patterns with different frequencies:

[0063]

[0064]

[0065]

[0066] Among them, (x, y) are the coordinates of the pattern pixel points; I1(x, y) is the pixel intensity of the first two-dimensional cosine oblique stripe pattern, I2(x, y) is the pixel intensity of the second two-dimensional cosine oblique stripe pattern, and I3(x, y) is the pixel intensity of the third two-dimensional cosine oblique stripe pattern; I DC is the average intensity of the two-dimensional cosine stripe pattern; I AC is the modulation intensity of the two-dimensional cosine stripe pattern; and are the frequencies of the two-dimensional cosine oblique stripe pattern I1(x, y) along the x-axis and y-axis respectively, and are the frequencies of the two-dimensional cosine oblique stripe pattern I2(x, y) along the x-axis and y-axis respectively, and are the frequencies of the two-dimensional cosine oblique stripe pattern I3(x, y) along the x-axis and y-axis respectively;

[0067] Step b: The computer controls the horizontally placed projector to vertically project the first cosine oblique stripe pattern I1(x, y) in step a onto a standard diffuser with a diffuse reflectance of 98% in the visible light band. The optical axis of the CCD camera intersects with the optical axis of the projector to form an angle α. The cosine oblique stripe image formed on the standard diffuser is imaged onto the CCD camera after passing through a filter to form a cosine oblique stripe image under a fixed light wave

[0068]

[0069] Among them, (x0, y0) are the coordinates of the image pixel points; MTF system is the modulation transfer function of the imaging system; R ref is the diffuse reflectance of the standard diffuser, R ref = 0.98; and are the spatial carrier frequencies of the cosine oblique stripe image along the x0-axis and y0-axis of the camera image plane coordinate system respectively;

[0070] Step c: The computer controls the horizontally placed projector to sequentially project the three two-dimensional cosine skew stripe patterns I1(x,y), I2(x,y), and I3(x,y) in Step a vertically onto the surface of the sample to be measured. The spatial depth position of the surface of the sample to be measured is the same as that of the standard diffuse reflection plate. The cosine skew stripe images formed on the surface of the sample to be measured are filtered by a filter and then imaged onto a CCD camera to form three cosine skew stripe images under a fixed light wave.

[0071]

[0072]

[0073]

[0074] where (x0,y0) are the coordinates of the image pixel points; MTF system is the modulation transfer function of the imaging system; R(x0,y0) is the diffuse reflectivity of the surface of the sample to be measured corresponding to the image pixel point (x0,y0); and are respectively the spatial carrier frequencies of the cosine skew stripe image along the x0-axis and y0-axis of the camera image plane coordinate system; and are respectively the spatial carrier frequencies of the cosine skew stripe image along the x0-axis and y0-axis of the camera image plane coordinate system; and are respectively the spatial carrier frequencies of the cosine skew stripe image along the x0-axis and y0-axis of the camera image plane coordinate system;

[0075] Step d: Perform two-dimensional Fourier transforms on the cosine skew stripe image in Step b and the cosine skew stripe images and in Step c to obtain the image spectra:

[0076]

[0077]

[0078]

[0079]

[0080] where is the two-dimensional Fourier transform operation; Is a cosine oblique stripe image The spectrum after Fourier transform, Is a cosine oblique stripe image The spectrum after Fourier transform, Is a cosine oblique stripe image The spectrum after Fourier transform, Is a cosine oblique stripe image The spectrum after Fourier transform; And Are the spatial frequencies of the cosine oblique stripe image along the x0-axis and y0-axis respectively; Is The first-order spectrum component of, and Is The first-order spectrum component of, and Is The first-order spectrum component of, and Is The first-order spectrum component of, and Is The complex conjugate of, Is The complex conjugate of, Is The complex conjugate of, Is The complex conjugate of;

[0081] Step e, Use a two-dimensional frequency-domain low-pass filter to separately extract the zero-order spectrum components of and in step d And Then perform two-dimensional inverse Fourier transform on and to obtain the DC component MTF of the cosine oblique stripe images And Then And Perform two-dimensional inverse Fourier transform to obtain the cosine oblique stripe images And The DC component MTF; Then use a two-dimensional frequency-domain band-pass filter to separately extract the first-order spectrum components of and in step d system ·R ref ·I DC And MTF system ·R(x0,y0)·I DC ; Then perform two-dimensional inverse Fourier transform on and to obtain the corresponding spatial domain expression forms And The first-order spectrum components of And Then And Perform two-dimensional inverse Fourier transform to obtain the corresponding spatial domain expression forms And

[0082] Step f: Based on the cosine oblique fringe image obtained in step e of the DC component MTF system ·R ref ·I DC and the DC component MTF of the cosine oblique fringe image calculate the diffuse reflectance R(x0, y0) of the sample surface corresponding to the image pixel point (x0, y0); system ·R(x0,y0)·I DC Calculate the diffuse reflectance R(x0, y0) of the sample surface corresponding to the image pixel point (x0, y0);

[0083]

[0084] Step g: Based on those obtained in step e and obtain the wrapped phases of the cosine oblique fringe images and where atan{} is the arctangent function; Im[] is the function of taking the imaginary part; Re[] is the function of taking the real part; and

[0085]

[0086]

[0087]

[0088] where atan{} is the arctangent function; Im[] is the function of taking the imaginary part; Re[] is the function of taking the real part;

[0089] Step h: Based on the wrapped phases obtained in step g and and use the three-frequency temporal phase unwrapping method based on number theory to unwrap the wrapped phase into the absolute phase φ(x0, y0), and then calculate the three-dimensional coordinates X(x0, y0), Y(x0, y0) and Z(x0, y0) of the sample surface corresponding to the image pixel point (x0, y0) according to the triangulation principle using the absolute phase φ wrapped (x0,y0);

[0090] Step i: Realize the integrated imaging of the diffuse reflectance and three-dimensional topography of the sample surface based on the diffuse reflectance R(x0, y0) of the sample surface obtained in step f and the three-dimensional coordinates X(x0, y0), Y(x0, y0) and Z(x0, y0) of the sample surface obtained in step h. Specific Embodiment 2

[0092] The following is the simulation experiment implementation of the integrated imaging method for the surface diffuse reflectance and three-dimensional topography based on the oblique fringe pattern of the present invention.

[0093] The following is a simulation imaging experiment to prove that the method for integrated imaging of surface diffuse reflectance and three-dimensional topography based on oblique fringe patterns in the present invention has the technical advantage of improving the measurement accuracy of the three-dimensional coordinates of the sample surface compared with the traditional Fourier transform three-dimensional imaging method using positive fringe patterns, and the method of the present invention can realize the diffuse reflectance measurement of the sample surface and the technical advantage of integrated imaging of the diffuse reflectance and three-dimensional topography of the sample surface.

[0094] The simulation imaging experimental system used is constructed in the 3DMAX simulation environment. The system consists of a projector with a resolution of 1024×768 pixels, a camera with a resolution of 2048×1536 pixels, and a uniform reference plane with a known diffuse reflectance of 0.98; the uniform reference plane with a known diffuse reflectance of 0.98 is used as a standard diffuse reflectance plate. The optical axis of the camera intersects with the optical axis of the projector to form an angle of 25°. The projector projects monochromatic red light to simulate the function of the filter.

[0095] The method of the present invention and the traditional Fourier transform three-dimensional imaging method using positive fringe patterns are implemented using the simulation imaging experimental system. Among them, the frequencies of the three oblique fringe patterns along the x-axis are 1 / 18 pixel -1 , 1 / 20 pixel -1 and 1 / 22 pixel -1 , and the frequencies along the y-axis are 1 / 18 pixel -1 , 1 / 20 pixel -1 and 1 / 22 pixel -1 ; the frequencies of the three positive fringe patterns along the x-axis are 1 / 18 pixel -1 , 1 / 20 pixel -1 and 1 / 22 pixel -1 , and the frequencies along the y-axis are all 0; these projection patterns are respectively used for simulation measurement of a uniform horizontal plane with a diffuse reflectance of 0.4 and a uniform inclined plane with a diffuse reflectance of 0.6. The measured horizontal plane and the measured inclined plane have the same spatial depth position as their corresponding reference planes, and the normal angle between the measured horizontal plane and the measured inclined plane is 25°. According to the method of the present invention, the diffuse reflectance and spatial three-dimensional coordinates of the measured horizontal plane and the measured inclined plane are obtained, and integrated imaging of the diffuse reflectance and three-dimensional topography of the measured horizontal plane and the measured inclined plane is realized.

[0096] It should be noted that the traditional Fourier transform three-dimensional imaging method using positive fringe patterns is a common method in the field of structured light three-dimensional imaging technology. Those skilled in the art are fully aware of it and can implement it independently according to professional knowledge. There is no need to describe it specifically in the present invention.

[0097] Experiment 1. Simulation imaging experiment of the horizontal plane

[0098] The experimental process is as Figures 2 to 5As shown, the integrated imaging results of the diffuse reflectance and three-dimensional topography of the measured horizontal plane obtained by the method of the present invention are as follows Figure 6 As shown, the gray scale in the figure represents the diffuse reflectance value, and the depth imaging error map of the measured horizontal plane obtained by the traditional Fourier transform three-dimensional imaging method using a positive stripe pattern is as follows Figure 7 As shown, the depth imaging error map and the diffuse reflectance imaging error map of the measured horizontal plane obtained by the method of the present invention are respectively as follows Figure 8 and Figure 9 As shown. For the quantitative evaluation of the depth imaging error of the measured horizontal plane, refer to Table 1:

[0099] Table 1 Depth imaging error of the horizontal plane

[0100]

[0101] For the quantitative evaluation of the diffuse reflectance of the measured horizontal plane obtained by the method of the present invention, refer to Table 2:

[0102] Table 2 Diffuse reflectance imaging error of the horizontal plane

[0103]

[0104] Experiment 2. Inclined plane simulation imaging experiment

[0105] The experimental process is as follows Figures 10 to 13 As shown, the integrated imaging results of the diffuse reflectance and three-dimensional topography of the measured inclined plane obtained by the method of the present invention are as follows Figure 14 As shown, the gray scale in the figure represents the diffuse reflectance value, and the depth imaging error map of the measured inclined plane obtained by the traditional Fourier transform three-dimensional imaging method using a positive stripe pattern is as follows Figure 15 As shown, the depth imaging error map and the diffuse reflectance imaging error map of the measured inclined plane obtained by the method of the present invention are respectively as follows Figure 16 and Figure 17 As shown. For the quantitative evaluation of the depth imaging error of the measured inclined plane, refer to Table 1:

[0106] Table 3 Depth imaging error of the inclined plane

[0107]

[0108] For the quantitative evaluation of the diffuse reflectance of the measured inclined plane obtained by the method of the present invention, refer to Table 2:

[0109] Table 4 Diffuse reflectance imaging error of the inclined plane

[0110]

[0111] It can be seen from Figure 6 and Figure 14 that the method of the present invention can realize the integrated imaging of the diffuse reflectance and three-dimensional topography of the surface of the measured sample; by comparing respectively Figure 7 andFigure 8 , Figure 15 and Figure 16 It can be seen from Table 1 and Table 3 that compared with the traditional Fourier transform three-dimensional imaging method using a positive stripe pattern, the depth mean absolute error, root mean square error, and maximum absolute error of the method of the present invention are all significantly reduced, improving the measurement accuracy of the three-dimensional coordinates of the sample surface. This is because the traditional Fourier transform three-dimensional imaging method using a positive stripe pattern only extracts the first-order spectral components by separating them in the one-dimensional frequency direction, while the method of the present invention extracts the first-order spectral components by separating them in the two-dimensional frequency direction. This effectively alleviates the aliasing between the first-order spectral components and the zero-order and second-order spectral components, and effectively improves the extraction quality of the first-order spectral components; from Figure 9 , Figure 17 , Table 2 and Table 4, it can be seen that the method of the present invention can measure the diffuse reflectivity of the sample surface and has high measurement accuracy; the results of the simulation experiment verify the beneficial effects of the method of the present invention.

[0112] Finally, it should be noted that the technical field corresponding to the technical solution of the present invention is the field of structured light three-dimensional measurement technology. For those skilled in the art, they can select and apply the specific parameters of each step and the instruments and equipment used in the method of the present invention according to their professional knowledge; in step h of the present invention, according to the wrapped phase and using a three-frequency time phase unwrapping method based on number theory to unwrap the wrapped phase into the absolute phase φ(x0, y0), and then using the absolute phase φ wrapped (x0, y0) to calculate the three-dimensional coordinates X(x0, y0), Y(x0, y0), Z(x0, y0) of the sample surface according to the triangulation principle, which belongs to the well-known and mature technology in the field. Those skilled in the art can fully implement it independently, and the present invention has been fully disclosed.

Claims

1. An integrated imaging method for surface diffuse reflectance and three-dimensional topography based on oblique stripe patterns, characterized in that, Including the following steps: Step a: The computer generates three two-dimensional cosine oblique stripe patterns with different frequencies: Among them, (x, y) are the coordinates of the pattern pixel points; I1(x, y) is the pixel intensity of the first two-dimensional cosine oblique stripe pattern, I2(x, y) is the pixel intensity of the second two-dimensional cosine oblique stripe pattern, and I3(x, y) is the pixel intensity of the third two-dimensional cosine oblique stripe pattern; I DC is the average intensity of the two-dimensional cosine stripe pattern; I AC is the modulation intensity of the two-dimensional cosine stripe pattern; and are the frequencies of the two-dimensional cosine oblique stripe pattern I1(x, y) along the x-axis and y-axis respectively, and are the frequencies of the two-dimensional cosine oblique stripe pattern I2(x, y) along the x-axis and y-axis respectively, and are the frequencies of the two-dimensional cosine oblique stripe pattern I3(x, y) along the x-axis and y-axis respectively; Step b: The computer controls the horizontally placed projector to vertically project the first cosine oblique stripe pattern I1(x, y) in step a onto a standard diffuser with a 98% diffuse reflectance in the visible light band. The optical axis of the CCD camera intersects with the optical axis of the projector to form an angle α. The cosine oblique stripe image formed on the standard diffuser is imaged onto the CCD camera after passing through a filter to form a cosine oblique stripe image under a fixed light wave. Among them, (x0, y0) is the coordinate of the image pixel point; MTF system is the modulation transfer function of the imaging system; R ref is the diffuse reflectance of the standard diffuse reflection plate, R ref = 0.98; and are respectively the spatial carrier frequencies of the cosine oblique stripe image along the x0-axis and y0-axis of the camera image plane coordinate system; Step c: The computer controls the horizontally placed projector to sequentially project the three two-dimensional cosine oblique stripe patterns I1(x,y), I2(x,y), and I3(x,y) in Step a onto the surface of the sample to be measured in sequence. The spatial depth position of the surface of the sample to be measured is the same as that of the standard diffuse reflection plate. The cosine oblique stripe images formed on the surface of the sample to be measured are imaged onto the CCD camera after being filtered by the filter to form three cosine oblique stripe images under the fixed light wave. Among them, (x0, y0) is the coordinate of the image pixel point; MTF system is the modulation transfer function of the imaging system; R(x0, y0) is the diffuse reflectivity of the surface of the measured sample corresponding to the image pixel point (x0, y0); and are respectively the spatial carrier frequencies of the cosine oblique fringe image along the x0-axis and y0-axis of the camera image plane coordinate system; and are respectively the spatial carrier frequencies of the cosine oblique fringe image along the x0-axis and y0-axis of the camera image plane coordinate system; and are respectively the spatial carrier frequencies of the cosine oblique fringe image along the x0-axis and y0-axis of the camera image plane coordinate system; Step d: For the cosine oblique stripe image in step b and the cosine oblique stripe image in step c and perform two-dimensional Fourier transform to obtain the image spectrum: Among them, is a two-dimensional Fourier transform operation; is the cosine oblique stripe image after Fourier transform, is the cosine oblique stripe image after Fourier transform, is the cosine oblique stripe image after Fourier transform, is the cosine oblique stripe image after Fourier transform; and are the spatial frequencies of the cosine oblique stripe image along the x0 axis and y0 axis respectively; is the first-order spectral component of, and is the first-order spectral component of, and is the first-order spectral component of, and is the first-order spectral component of, and is the complex conjugate of, is the complex conjugate of, is the complex conjugate of, is the complex conjugate of; Step e: Use a two-dimensional frequency-domain low-pass filter to separately extract the zero-order spectral components of and in step d. and Then perform an inverse two-dimensional Fourier transform on and to obtain the cosine fringe image and of the DC component MTF system ·R ref ·I DC and MTF system ·R(x0,y0)·I DC ; Then use a two-dimensional frequency-domain band-pass filter to separately extract the first-order spectral components of and in step d. and Then perform an inverse two-dimensional Fourier transform on and to obtain the corresponding spatial domain representation and Step f: Based on the cosine oblique stripe image obtained in step e of the DC component MTF system ·R ref ·I DC and the DC component MTF of the cosine oblique stripe image ·R(x0, y0)·I system DC calculate the diffuse reflectance R(x0, y0) of the sample surface corresponding to the image pixel point (x0, y0);​ Step g, according to what is obtained in step e and obtain the cosine oblique stripe image and the wrapped phase and Where atan{} is the arctangent function; Im[] is the function of taking the imaginary part; Re[] is the function of taking the real part; Step h, according to the wrapped phase obtained in step g and and use the three-frequency time phase unwrapping method based on number theory to unwrap the wrapped phase into the absolute phase φ(x0, y0), and then use the absolute phase φ wrapped (x0, y0) to calculate the three-dimensional coordinates X(x0, y0), Y(x0, y0) and Z(x0, y0) of the sample surface corresponding to the image pixel point (x0, y0); Step i: Based on the sample surface diffuse reflectance R(x0, y0) obtained in step f and the three-dimensional coordinates X(x0, y0), Y(x0, y0), and Z(x0, y0) of the sample surface obtained in step h, integrated imaging of the sample surface diffuse reflectance and three-dimensional topography is realized.

Images