阅读说明：本技术 一种基于相移条纹投影的刚性运动物体三维测量方法 (Rigid moving object three-dimensional measurement method based on phase shift fringe projection ) 是由 王玉伟 申军 蔡家旭 时国龙 刘路 王亚军 于 2021-07-23 设计创作，主要内容包括：本发明公开了一种基于相移条纹投影的刚性运动物体三维测量方法,具体包括以下步骤：步骤S1：搭建条纹投影三维测量系统,包括投影仪和摄像机；步骤S2：投影仪依次投射N幅相移条纹图案投射到运动物体表面,摄像机同步采集运动物体调制后的变形的相移条纹图像；步骤S3：利用N步相移法求解相移条纹的截断相位φ-(1)；构建组合相位；采用直方图均衡化处理组合相位得到校正的组合相位；步骤S4：构建样条插值函数f(φ-(1)),消除引入的离散性相位误差,则φ-(3)＝f(φ-(1))表示优化的截断相位；步骤S5：针对优化的截断相位φ-(3)进行相位展开,获得连续的绝对相位Φ-(3),将所述绝对相位Φ-(3)转换为高度信息,重建出运动物体的三维形貌。(The invention discloses a three-dimensional measurement method of a rigid moving object based on phase shift fringe projection, which specifically comprises the following steps: step S1: constructing a fringe projection three-dimensional measurement system which comprises a projector and a camera; step S2: the projector sequentially projects N phase shift fringe patterns to the surface of the moving object, and the camera synchronously acquires the deformed phase shift fringe patterns modulated by the moving object; step S3: method for solving truncation phase phi of phase shift stripe by using N-step phase shift method 1 (ii) a Constructing a combined phase; processing the combined phase by histogram equalization to obtain a corrected combined phase; step S4: construction of a spline interpolation function f (phi) 1 ) Removing the introduced discrete phase error, then phi 3 ＝f(φ 1 ) Represents an optimized truncated phase; step S5: truncation phase phi for optimization 3 Performing phase unwrapping to obtain continuous absolute phase phi 3 The absolute phase phi is determined 3 And converting the height information into height information, and reconstructing the three-dimensional appearance of the moving object.)

1. A three-dimensional measurement method for rigid moving objects based on phase shift fringe projection is characterized by comprising the following steps: the method specifically comprises the following steps:

step S1: the method comprises the following steps of constructing a fringe projection three-dimensional measurement system, wherein the fringe projection three-dimensional measurement system comprises a projector and a camera, the projector and the camera are triggered to start to work synchronously, and the projector, the camera and a moving object form a triangulation relation;

step S2: the projector sequentially projects N (wherein N is more than or equal to 3) phase shift stripe patterns to the surface of the moving object, the phase shift stripes are deformed due to the modulation effect of the surface appearance of the moving object, and the camera synchronously acquires the deformed phase shift stripe images modulated by the moving object;

step S3: method for solving truncation phase phi of phase shift stripe by using N-step phase shift method₁(ii) a To eliminate phase errors introduced by object motion, a combined phase [ phi ] is constructed₁,mod(φ₁+π,2π)]Where mod represents a remainder function; processing combined phase [ phi ] using histogram equalization₁,mod(φ₁+π,2π)]Obtaining a corrected combined phase [ phi ]₂,mod(φ₂+π,2π)]Wherein phi₂Represents a corrected truncated phase;

step S4: because of the corrected truncated phase phi₂Is a discrete value, uncorrected truncated phase phi₁Is a continuous value, and selects a corrected truncation phase phi to further eliminate the discreteness phase error introduced by histogram equalization₂As a function value, the uncorrected truncation phase phi₁As an independent variable, constructing a spline interpolation function f (phi)₁) Then phi is₃＝f(φ₁) Represents an optimized truncated phase;

step S5: truncation phase phi for optimization₃Performing phase unwrapping to obtain continuous absolute phase phi₃Obtaining phase-height conversion relation through system calibration process, and converting continuous absolute phase phi₃And converting the height information into height information, and reconstructing the three-dimensional appearance of the moving object.

2. The method for three-dimensional measurement of a rigidly moving object based on phase shift fringe projection as claimed in claim 1, wherein: in step S2, the intensity of the phase-shift fringe pattern projected by the projector is expressed as follows:

in the formula: n-0, 1,2,. N, N-1; (x)^p,y^p) Pixel coordinates representing a projector; t represents a fringe period; 2 π N/N represents the amount of phase shift.

3. The method for three-dimensional measurement of a rigidly moving object based on phase shift fringe projection as claimed in claim 1, wherein: in step S2, the intensity of the phase-shifted fringe image collected by the camera is expressed as follows:

I_n(x,y)＝A(x,y)+B(x,y)cos[φ₀(x,y)+2πn/N+ε_n(x,y)]；

in the formula: (x, y) represents pixel coordinates of the camera; a and B represent average intensity and modulation intensity, respectively; phi is a₀Representing the ideal truncated phase; epsilon_nRepresents the amount of additional phase shift introduced by the object motion; wherein for rigid moving objects the additional phase shift epsilon_nCan be considered as constants (Applied Optics,2018,57(36): 10364-9).

4. The method for three-dimensional measurement of a rigidly moving object based on phase shift fringe projection as claimed in claim 1, wherein: in step S3, the N-step phase shift method is used to solve the truncation phase phi of the phase shift stripe₁：

Theoretical analysis shows that the ideal truncation phase phi₀Is uniform, the truncated phase phi of the solution₁Is non-uniform (Optics Express,2019,27(22): 32047-57); phase error delta phi₁＝φ₁-φ₀Exhibits a periodic distribution with a period twice that of the phase-shifted fringe (Optics Express,2018,26(26): 34224-35);

according to the above characteristics, histogram equalization is preferably employedProcessing the combined phase [ phi ]₁,mod(φ₁+π,2π)]Obtaining a corrected combined phase [ phi ]₂,mod(φ₂+π,2π)]And extracting therefrom a corrected truncated phase phi₂The aim is to reduce the influence of the object morphology on the histogram distribution; of course, the uncorrected truncated phase φ can also be processed directly using histogram equalization₁Obtaining a corrected truncation phase phi₂。

Technical Field

The invention belongs to the technical field of three-dimensional measurement, and particularly relates to a three-dimensional measurement method of a rigid moving object based on phase shift fringe projection.

Background

The fringe projection method has the advantages of non-contact, high precision, high speed, low cost and the like, is widely applied to the field of three-dimensional measurement, and has the key point of accurately extracting the phase distribution of the fringes. The phase shift method is a relatively common phase extraction algorithm, however, when a moving object is measured, the amount of phase shift among a plurality of phase shift stripes changes, and further, a periodic phase error is introduced.

In order to solve the above problems, researchers at home and abroad have proposed some error compensation methods, which all achieve good effects (Optics and Lasers in Engineering, 2021,141: 106573). For example, object motion information is estimated by feature matching, but is not applicable to motion objects with insignificant features (Optics Express, 2013, 21(25): 30610-22; Optics Express, 2020, 28(19): 28600-11); the phase error is compensated by combining a Fourier equal frequency domain method, but the method relates to frequency domain operation, the operation amount is large, and the robustness is general (Optics Express, 2016, 24(20): 23289-.

In summary, how to accurately recover the three-dimensional morphology of the moving object still faces a great challenge.

Disclosure of Invention

The invention provides a three-dimensional measurement method of a rigid moving object based on phase shift fringe projection, which aims to solve the problems in the background technology.

In order to achieve the purpose, the invention adopts the technical scheme that: a three-dimensional measurement method for a rigid moving object based on phase shift fringe projection specifically comprises the following steps:

step S1: the method comprises the following steps of constructing a fringe projection three-dimensional measurement system, wherein the fringe projection three-dimensional measurement system comprises a projector and a camera, the projector and the camera are triggered to start to work synchronously, and the projector, the camera and a moving object form a triangulation relation;

step S2: the projector sequentially projects N (wherein N is more than or equal to 3) phase shift stripe patterns to the surface of the moving object, the phase shift stripes are deformed due to the modulation effect of the surface appearance of the moving object, and the camera synchronously acquires the deformed phase shift stripe images modulated by the moving object;

step S3: method for solving truncation phase phi of phase shift stripe by using N-step phase shift method₁(ii) a To eliminate phase errors introduced by object motion, a combined phase [ phi ] is constructed₁,mod(φ₁+π,2π)]Where mod represents a remainder function; processing combined phase [ phi ] using histogram equalization₁,mod(φ₁+π,2π)]Obtaining a corrected combined phase [ phi ]₂,mod(φ₂+π,2π)]Wherein phi₂Represents a corrected truncated phase;

step S4: because of the corrected truncated phase phi₂Is a discrete value, uncorrected truncated phase phi₁Is a continuous value, and selects a corrected truncation phase phi to further eliminate the discreteness phase error introduced by histogram equalization₂As a function value, the uncorrected truncation phase phi₁As an independent variable, constructing a spline interpolation function f (phi)₁) Then phi is₃＝f(φ₁) Represents an optimized truncated phase;

step S5: truncation phase phi for optimization₃Performing phase unwrapping to obtain continuous absolute phase phi₃Obtaining phase-height conversion relation through system calibration process, and converting continuous absolute phase phi₃And converting the height information into height information, and reconstructing the three-dimensional appearance of the moving object.

Further, in step S2, the intensity of the phase shift fringe pattern projected by the projector is expressed as follows:

in the formula: n-0, 1,2,. N, N-1; (x)^p,y^p) Pixel coordinates representing a projector; t represents a fringe period; 2 π N/N represents the amount of phase shift.

Further, in step S2, the intensity of the phase-shifted fringe image collected by the camera is expressed as follows:

I_n(x,y)＝A(x,y)+B(x,y)cos[φ₀(x,y)+2πn/N+ε_n(x,y)]；

in the formula: (x, y) represents pixel coordinates of the camera; a and B represent average intensity and modulation intensity, respectively; phi is a₀Representing the ideal truncated phase; epsilon_nRepresents the amount of additional phase shift introduced by the object motion; wherein for rigid moving objects the additional phase shift epsilon_nCan be considered as constants (Applied Optics,2018,57(36): 10364-9).

Further, in step S3, the truncation phase Φ of the phase-shift fringe is solved by using N-step phase shift method₁：

Theoretical analysis shows that the ideal truncation phase phi₀Is uniform, the truncated phase phi of the solution₁Is non-uniform (Optics Express,2019,27(22): 32047-57); phase error delta phi₁＝φ₁-φ₀Exhibits a periodic distribution with a period twice that of the phase-shifted fringe (Optics Express,2018,26(26): 34224-35);

in view of the above, the combined phase [ phi ] is preferably processed using histogram equalization₁,mod(φ₁+π,2π)]Obtaining a corrected combined phase [ phi ]₂,mod(φ₂+π,2π)]And extracting therefrom a corrected truncated phase phi₂The aim is to reduce the influence of the object morphology on the histogram distribution; of course, the uncorrected truncated phase φ can also be processed directly using histogram equalization₁Obtaining a corrected truncation phase phi₂。

The beneficial effect of adopting above technical scheme is:

1. according to the three-dimensional measurement method for the rigid moving object based on the phase shift fringe projection, provided by the invention, only N pieces of phase shift fringe patterns are required to be projected onto the surface of the moving object in sequence, and the three-dimensional measurement speed is high.

2. According to the rigid moving object three-dimensional measurement method based on phase shift fringe projection, estimation of object motion information of complex algorithms such as feature matching, frequency domain operation and the like is not needed, histogram equalization is easy to achieve, and flexibility of three-dimensional measurement is greatly improved.

Drawings

FIG. 1 shows the results of a simulation experiment of a planar moving object; (a) - (c) three-step phase-shifting stripes; (d) - (f) truncation of the phase phi₁,φ₂,φ₃；

FIG. 2 shows the phase error Δ φ of a planar moving object₁,Δφ₂,Δφ₃；

FIG. 3 shows simulation experiment results of a complex moving object; (a) - (c) three-step phase-shifting stripes; (d) - (f) truncation of the phase phi₁,φ₂,φ₃；

FIG. 4 shows the phase error Δ φ of a complex moving object₁,Δφ₂,Δφ₃；

FIG. 5 shows the results of a real experiment on a moving object; (a) - (c) three-step phase-shifting stripes; (d) - (f) truncation of the phase phi₁,φ₂，φ₃(ii) a (g) - (i) absolute phase Φ₁，Φ₂，Φ₃；

Detailed Description

The following detailed description of the embodiments of the present invention will be given with reference to the accompanying drawings for a purpose of helping those skilled in the art to more fully, accurately and deeply understand the concept and technical solution of the present invention and to facilitate its implementation.

As shown in fig. 1 to 5, the present invention is a three-dimensional measurement method for a rigid moving object based on phase shift fringe projection, which introduces a simulation experiment for a planar moving object, a simulation experiment for a complex moving object, and a real experiment for a plurality of moving objects in sequence by taking a three-step phase shift method as an example, and specifically includes the following steps:

example 1:

step S1: the method comprises the following steps of constructing a fringe projection three-dimensional measurement system, wherein the fringe projection three-dimensional measurement system comprises a projector and a camera, the projector and the camera are triggered to start to work synchronously, and the projector, the camera and a moving object form a triangulation relation;

step S2: the projector sequentially projects three phase-shift fringe patterns to the surface of a moving object, the phase-shift fringes deform under the modulation action of the surface appearance of the moving object, and the camera synchronously acquires the deformed phase-shift fringe images modulated by the moving object; FIGS. 1(a) - (c) are simulated phase shift fringe images of a planar moving object; FIGS. 3(a) - (c) are simulated phase shift fringe images of a complex moving object; FIGS. 5(a) - (c) are true phase shifted fringe images of multiple moving objects;

step S3: method for solving truncation phase phi of phase shift stripe by using three-step phase shift method₁(ii) a FIG. 1(d) shows the truncated phase phi of a planar moving object₁(ii) a FIG. 3(d) shows the truncated phase φ of a complex moving object₁(ii) a FIG. 5(d) shows truncated phases φ of a plurality of moving objects₁(ii) a As can be seen from the figure, the above-mentioned truncated phase phi₁The linearity of (2) is poor, and the phase error is large; to eliminate phase errors introduced by object motion, a combined phase [ phi ] is constructed₁,mod(φ₁+π,2π)]Where mod represents a remainder function; processing combined phase [ phi ] using histogram equalization₁,mod(φ₁+π,2π)]Obtaining a corrected combined phase [ phi ]₂,mod(φ₂+π,2π)]Wherein phi₂Represents a corrected truncated phase; FIG. 1(e) shows the truncated phase φ of a planar moving object₂(ii) a FIG. 3(e) shows the truncated phase φ of a complex moving object₂(ii) a FIG. 5(e) shows truncated phases φ of a plurality of moving objects₂(ii) a As can be seen from the figure, the above-mentioned truncated phase phi₂The linearity is better, and the phase error is obviously reduced;

step S4: because of the corrected truncated phase phi₂Is a discrete value, uncorrected truncated phase phi₁Is a continuous value, and selects a corrected truncation phase phi to further eliminate the discreteness phase error introduced by histogram equalization₂As a function value, the uncorrected truncation phase phi₁As an independent variable, constructing a spline interpolation function f (phi)₁) Then phi is₃＝f(φ₁) Represents an optimized truncated phase; drawing (A)1(f) is the truncation phase phi of the planar moving object₃(ii) a FIG. 3(f) shows the truncated phase φ of a complex moving object₃(ii) a FIG. 5(f) shows truncated phases φ of a plurality of moving objects₃. Respectively truncate the phase phi₁，φ₂，φ₃Subtracting the truncation phase phi₀To obtain a corresponding phase error delta phi₁，Δφ₂，Δφ₃. FIG. 2 shows the phase error Δ φ of a planar moving object₁，Δφ₂，Δφ₃(ii) a FIG. 3 shows the phase error Δ φ of a complex moving object₁，Δφ₂，Δφ₃(ii) a It can be seen from the figure that the phase error delta phi₁The amplitude of (3) is large; phase error delta phi₂Is smaller but has more burrs; phase error delta phi₃Is the smallest and has fewer spikes.

Step S5: truncation phase phi for optimization₃Performing phase unwrapping to obtain continuous absolute phase phi₃Obtaining phase-height conversion relation through system calibration process, and converting continuous absolute phase phi₃And converting the height information into height information, and reconstructing the three-dimensional appearance of the moving object. FIGS. 5(g) - (i) are diagrams of absolute phases Φ of a plurality of moving objects₁，Φ₂,Φ₃. It can be seen from the figure that the phase with respect to absolute phi₁Absolute phase phi₂,Φ₃The phase error is obviously reduced, and the three-dimensional appearance of the reconstructed moving object is smoother.

The present invention has been described in connection with the accompanying drawings, and it is to be understood that the invention is not limited to the specific embodiments described above, but is intended to cover various insubstantial modifications of the invention based on the principles and technical solutions of the invention; the present invention is not limited to the above embodiments, and can be modified in various ways.