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A 3D Surface Shape Measurement Method Based on Complex Mexican Hat Wavelet
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A technology of three-dimensional surface shape and measurement method, applied in the direction of measuring devices, complex mathematical operations, instruments, etc., can solve the problem of low precision and achieve high measurement precision and good reconstruction results
Active Publication Date: 2021-03-30
SICHUAN UNIV
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[0005] The purpose of the present invention is to solve the problem that the accuracy of the existing three-dimensional surface shape measurement method based on the complex Morlet wavelet is low, and propose a three-dimensional surface shape measurement method based on the complex Mexican hat wavelet
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experiment example 1
[0101] In this experiment example, the computer simulation of the complex Mexican hat wavelet is completed. Let the system structure parameter be L / d=1, the fundamental frequency f of the projected grating 0 =1 / 12, the simulated random noise and nonlinearity are n(x,y)=0.05*randn(512,512), R=1.5, and the image size is 512×512pixels. Figure 5 (a) is the measured phase object Z(x,y) simulated by computer, expressed as:
[0104] Z 1 (x,y)=8*sinc((x-256) / 80)*sinc((y-256) / 80),
[0105] Z 2 (x,y)=cos(2*pi*(x-256) / 1024)*cos(2*pi*(y-256) / 1024),
[0106] Z 3 (x,y)=peaks(512).
[0107] Considering the inhomogeneity of the background, the background fringes and projected fringes generated by computer simulation are expressed as:
[0108]
[0109] deformed stripes such as Figure 5 (b) shown. Use the defined complex Mexican hat wavelet to process the fringe image, and compare the ...
experiment example 2
[0114] The selected object in this experiment example is a monkey mask. The projector projects sinusoidal stripes onto the surface of the measured object, Figure 8 (a) is the deformed fringe collected by CCD, and the size after cropping is 700pixel×700pixel. Figure 8 (b) and (c) are the reconstruction results of the two methods, respectively.
[0115] In order to make the comparison clear, in this experiment example, the 350th row of the reconstruction phase is taken to zoom in, such as Figure 9 shown. It can be clearly seen that the complex Morlet wavelet reconstructs the surface shape more smoothly but loses the details of the object, while the complex Mexican hat wavelet reconstructs the results with higher accuracy and richer details.
[0116] Therefore, the present invention uses the complex Mexican hat wavelet to extract the phase information in the deformed fringes, and measures and reconstructs the three-dimensional surface shape of the measured object. It has be...
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Abstract
The invention discloses a three-dimensional surface shape measurement method based on a complex Mexico hat wavelet. The complex Mexico hat wavelet is applied to one-dimensional wavelet transformationto realize three-dimensional surface shape measurement of a measured object. In the invention, the complex Mexico hat wavelet with a positive frequency and asymmetric single side band distribution characteristic is constructed, and a tolerance condition of wavelet transformation is met. Meanwhile, the complex Mexicohat wavelet is used for extracting phase information in deformation stripes and reconstructing the three-dimensional surface shape of the measured object, and simulation and experiments prove that the complex Mexico hat wavelet constructed in the method has higher measurement precision and a better reconstruction result than those of a complex Morlet wavelet.
Description
technical field [0001] The invention belongs to the technical field of three-dimensional surface shape measurement, and in particular relates to the design of a three-dimensional surface shape measurement method based on complex Mexican hat wavelets. Background technique [0002] The fringe projection 3D surface shape measurement technology has broad application prospects in many fields, among which Fourier transform profilometry, window Fourier transform, wavelet transform profilometry and phase shift measurement profilometry are currently commonly used 3D surface shape measurement methods . Phase-shift measurement profilometry requires at least three frames of fringe images to reconstruct the three-dimensional surface information of the measured object, which is usually not suitable for dynamic process measurement. Fourier transform profilometry can reconstruct the three-dimensional surface information of an object from a frame of fringe images. It has a fast measurement ...
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