Single-frame color stripe three-dimensional imaging method

Abstract

The invention provides a single-frame color stripe three-dimensional imaging method, and the method comprises the steps: projecting a frame of color image to an object to be measured, obtaining a color distortion image of the object through a camera, and coding two frames of phase shift sine stripes in an R channel and a B channel of the color image; separating and acquiring two frames of phase shift stripe images in R and B channels of the color distortion image from the color distortion image by adopting a color separation method; based on the obtained two frames of phase shift fringe images, phase distribution of the measured object is obtained by adopting a non-filtering elliptic algorithm; and recovering three-dimensional shape data of the object based on a phase-height mapping formula of the object according to the obtained phase distribution of the measured object. The single-frame color stripe three-dimensional imaging method is high in robustness, high in precision and rapid in imaging, more detail information of an object can be reserved, and technical support is provided for development of the high-speed three-dimensional measurement field.

Description

Technical Field

[0001] The invention relates to the technical field of three-dimensional imaging, and in particular to a single-frame color stripe three-dimensional imaging method. Background Art

[0002] With the information age where machine learning and measurement technology are increasingly abundant, as well as the continuous improvement of industrial production and manufacturing efficiency, the demand for fast and accurate measurement of the three-dimensional morphology of objects is also increasing. The actual morphology and size of objects can be restored by collecting the color, contour and edge features of objects. In the fields of automated identification, industrial online detection, robot vision, biomedicine, etc., three-dimensional measurement has become the most basic demand. Compared with the traditional contact three-dimensional measurement method, non-contact three-dimensional measurement technology has fast calculation and processing capabilities and high accuracy because it does not contact the measured object, making it the most promising three-dimensional morphology measurement method. Among the non-contact three-dimensional imaging methods based on this, the fringe projection three-dimensional imaging method based on phase measurement stands out. Its advantage is that incoherent light sources are used in the measurement process, but the measurement accuracy of coherent light sources can be achieved. By projecting a fringe image onto an object, after being modulated by the object, the distorted fringe image is captured by a CCD camera, and finally the phase information is demodulated to restore the three-dimensional surface morphology of the object.

[0003] In the fringe projection 3D imaging method based on phase measurement, multi-frame imaging methods, such as phase shift profilometry, need to collect multiple images at different times. They have the advantages of high resolution and high precision, but they require at least three frames of images and introduce dynamic errors during rapid measurement, which limits their application in the field of rapid 3D imaging. Single-frame imaging methods, such as Fourier profilometry, wavelet transform profilometry, and S transform, can calculate the 3D shape of an object using only one frame of image. They have fast measurement speeds, but for objects with complex surface shapes, it is difficult to maintain the measurement details of the object because the filtering operation will inevitably filter out useful information. At the same time, the frequency domain filtering operation also increases the complexity of the imaging algorithm. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art.

[0005] The present invention provides a single-frame color stripe three-dimensional imaging method, which comprises: projecting a frame of color image onto an object to be measured, obtaining a color distorted image of the object by a camera, wherein two frames of phase-shifted sinusoidal stripes are encoded in an R channel and a B channel of the color image; using a color separation method to separate and obtain two frames of phase-shifted stripe images in the R and B channels of the color distorted image; based on the obtained two frames of phase-shifted stripe images, using a filter-free ellipse algorithm to obtain the phase distribution of the object to be measured; according to the obtained phase distribution of the object to be measured, restoring the three-dimensional shape data of the object based on the phase-height mapping formula of the object.

[0006] Furthermore, the expression of the color distorted image is Where I represents the light intensity distribution of a frame of color distorted image captured by the camera; a r and a b Corresponds to the background intensity in the R and B channels of the color image respectively; b r and b b Respectively represent the modulation degree in the R and B channels of the color image; is the phase distribution of the object being measured; π / 3 represents the phase shift of the two frames of fringes in the R and B channels of the color image; (x, y) is the light intensity position of the color distortion image.

[0007] Furthermore, the expressions of the two frames of phase-shifted fringe images obtained separately are: and Among them, I r and I b Respectively represent the light intensity distribution of two frames of phase-shifted fringe images separated from the color distortion image; A r and A b Respectively represent the background intensity separated from the R and B channels of the color distorted image; B r and B b They represent the modulation degrees separated from the R and B channels of the color distorted image respectively; δ is the phase shift of the two frames of phase-shifted fringes separated from the R and B channels of the color distorted image.

[0008] Furthermore, the phase distribution of the object under test is: in,

[0009] Furthermore, the phase-height mapping formula of the object is Wherein, L is the vertical distance from the camera to the object in the three-dimensional imaging device; d is the distance from the projected light source to the camera; f is the frequency of the color distorted image; and h is the three-dimensional shape data of the object.

[0010] By applying the technical solution of the present invention, a single-frame color stripe three-dimensional imaging method is provided, which encodes two frames of phase-shifted sinusoidal stripes in the R and B channels of a color image, obtains a color distorted image of the object, separates and obtains two frames of phase-shifted stripe images therefrom, and uses a filter-free ellipse algorithm and the phase-height mapping formula of the object to restore the three-dimensional shape data of the object. The single-frame color stripe three-dimensional imaging method of the present invention has strong robustness, high precision, and fast imaging, and can retain more detailed information of the object, providing technical support for the development of the field of high-speed three-dimensional measurement. Compared with the prior art, the technical solution of the present invention can solve the technical problems in the prior art of using a single-frame image to reconstruct the three-dimensional shape of an object, which has complex algorithms and insufficient object measurement shape details. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The included drawings are used to provide a further understanding of the embodiments of the present invention, which constitute a part of the specification, are used to illustrate the embodiments of the present invention, and together with the text description, explain the principles of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0012] Figure 1 A schematic flow chart of a single-frame color stripe three-dimensional imaging method provided according to a specific embodiment of the present invention is shown. DETAILED DESCRIPTION

[0013] It should be noted that, in the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0014] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0015] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present invention. Meanwhile, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be considered as a part of the specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, and therefore, once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0016] like Figure 1 As shown, according to a specific embodiment of the present invention, a single-frame color stripe three-dimensional imaging method is provided, and the single-frame color stripe three-dimensional imaging method includes: projecting a frame of color image onto an object to be measured, and obtaining a color distorted image of the object by a camera, wherein two frames of phase-shifted sinusoidal stripes are encoded in the R channel and the B channel of the color image; using a color separation method to separate and obtain two frames of phase-shifted stripe images in the R and B channels of the color distorted image from the color distorted image; based on the obtained two frames of phase-shifted stripe images, using a filter-free ellipse algorithm to obtain the phase distribution of the object to be measured; according to the obtained phase distribution of the object to be measured, the three-dimensional morphology data of the object is restored based on the phase-height mapping formula of the object.

[0017] By applying this configuration, a single-frame color stripe three-dimensional imaging method is provided, which encodes two frames of phase-shifted sinusoidal stripes in the R and B channels of a color image, obtains a color distorted image of an object, separates and obtains two frames of phase-shifted stripe images, and uses a filter-free ellipse algorithm and a phase-height mapping formula of the object to restore the three-dimensional shape data of the object. The single-frame color stripe three-dimensional imaging method of the present invention has strong robustness, high precision, and fast imaging, can retain more detailed information of the object, and provides technical support for the development of the field of high-speed three-dimensional measurement.

[0018] Furthermore, in the present invention, in order to realize single-frame color stripe three-dimensional imaging, a frame of color image is first projected onto the object to be measured, and a color distorted image of the object is obtained by a camera, wherein two frames of phase-shifted sinusoidal stripes are encoded in the R channel and the B channel of the color image.

[0019] As a specific embodiment of the present invention, a projector may be used to project a frame of color image onto the object to be measured.

[0020] The expression of color distorted image is: Where I(x, y) represents the light intensity distribution of a frame of color distorted image captured by the camera; a r (x, y) and a b (x, y) corresponds to the background intensity in the R and B channels of the color image, respectively; b r (x, y) and b b (x, y) represents the modulation degree in the R and B channels of the color image, respectively; is the phase distribution of the object being measured; π / 3 represents the phase shift of the two frames of fringes in the R and B channels of the color image; (x, y) is the light intensity position of the color distortion image.

[0021] For the sake of simplicity, the present invention omits the position coordinates (x, y) and simplifies the expression of the above color distorted image to:

[0022]

[0023] Furthermore, in the present invention, after acquiring the color distorted image of the object, a color separation method is used to separate and acquire two frames of phase-shifted fringe images in R and B channels of the color distorted image.

[0024] As a specific embodiment of the present invention, the expressions of two frames of phase-shifted fringe images obtained separately are:

[0025]

[0026]

[0027] Among them, I r (x, y) and I b (x, y) represent the light intensity distribution of two frames of phase-shifted fringe images separated from the color distortion image; A r (x, y) and A b (x, y) represent the background intensity separated from the R and B channels of the color distorted image, respectively; B r (x, y) and B b (x, y) represents the modulation degree separated from the R and B channels of the color distorted image respectively; δ is the phase shift of the two frames of phase-shifted fringes separated from the R and B channels of the color distorted image.

[0028] Due to the color crosstalk of the camera, uneven background intensity and modulation will be caused, that is, A r (x, y) ≠ A b (x,y),B r (x, y) ≠ B b (x, y). In addition, color crosstalk will also cause the phase shift of the fringe patterns in the R and B channels to change, that is, δ≠π / 3.

[0029] Similarly, by simplifying the expressions (2) and (3) of the above two frames of phase-shifted fringe images, the expressions of the two frames of phase-shifted fringe images are obtained as follows:

[0030]

[0031]

[0032] Furthermore, in the present invention, after acquiring two frames of phase-shifted fringe images, a non-filtered ellipse algorithm is used based on the acquired two frames of phase-shifted fringe images to acquire the phase distribution of the object under test.

[0033] As a specific embodiment of the present invention, the two frames of phase-shifted fringe images in formulas (4) and (5) are further transformed to obtain:

[0034]

[0035]

[0036] According to cos 2 (x)+sin 2 (x) = 1, then the expression of the ellipse can be obtained:

[0037]

[0038] Expanding the above formula, we can get:

[0039]

[0040] According to the general quadratic curve equation, formula (9) can be rewritten as:

[0041] l.I r 2 +m·I r I b +n·I b 2 +r·I r +s·I b +t=0 (10)

[0042] In the above formula, l, m, n, r, s, and t are the fitting parameters of the elliptic equation:

[0043] The least squares algorithm can be used to obtain the calculation results of l, m, n, r, s, and t, but m must be satisfied. 2 -4ln<0.

[0044] At the same time, formula (10) can be rewritten as the standard expression of an ellipse:

[0045]

[0046] In the above formula, x 0 ,y 0 、a x 、a y , θ are the parameters of the standard ellipse equation; x 0 ,y 0 Indicates the offset of the ellipse; a x 、a y represents the major and minor axes of the ellipse; θ is the rotation angle of the ellipse around the x-axis.

[0047] According to the calculated l, m, n, r, s, t, the parameters of the standard ellipse expression can be obtained as follows:

[0048]

[0049]

[0050]

[0051]

[0052]

[0053] Formula (11) can be rewritten as follows:

[0054]

[0055]

[0056] According to formulas (17) and (18), the phase distribution of the object under test can be obtained:

[0057]

[0058] in,

[0059] Furthermore, in the present invention, after the phase distribution of the measured object is acquired, the three-dimensional shape data of the object is restored based on the phase-height mapping formula of the object according to the phase distribution of the measured object.

[0060] As a specific embodiment of the present invention, the phase information of the object can be obtained according to formula (19), and then the three-dimensional shape data of the object can be restored by the phase-height mapping formula. The phase-height mapping formula is as follows:

[0061]

[0062] Wherein, L is the vertical distance from the camera to the object in the three-dimensional imaging device; d is the distance from the projected light source to the camera; f is the frequency of the color distorted image; and h is the three-dimensional shape data of the object.

[0063] The present invention utilizes the advantages of single-frame three-dimensional imaging rapid measurement, and can calculate the three-dimensional shape of an object using only one frame of color image. However, for complex surface objects, due to the limitations of filtering operations in single-frame three-dimensional imaging methods, such as Fourier profilometry and wavelet transform profilometry, it is difficult to maintain the measurement details of the object. Therefore, the present invention encodes two frames of phase-shifted stripes in the R and B channels of the color image, projects a frame of color image onto the surface of the object to be measured, and captures the distorted image containing the object phase by the camera. Then, the two frames of phase-shifted stripe images of the R and B channels of the color distorted image are separated, but due to the influence caused by the color crosstalk of the color camera, the background intensity, modulation degree and phase shift amount of the two frames of phase-shifted stripe images after separation will change. Therefore, the present invention performs transformation operations on the two frames of phase-shifted stripe images, derives an ellipse expression, and finally uses the least squares algorithm to calculate the ellipse parameters, so that only one frame of image is needed and no filtering operation is required. Three-dimensional imaging can be performed, which can enable the reconstructed object to retain more detailed information, providing technical support for the field of rapid three-dimensional measurement.

[0064] The filter-free single-frame color three-dimensional imaging method of the present invention is widely used in the fields of rapid three-dimensional measurement, face recognition, robot vision, etc.

[0065] In order to further understand the present invention, the following Figure 1 The single-frame color stripe three-dimensional imaging method of the present invention is described in detail.

[0066] like Figure 1 As shown, according to a specific embodiment of the present invention, a single-frame color stripe three-dimensional imaging method is provided, which specifically includes the following steps.

[0067] Step 1: Use a projector to project a color image onto the object to be tested, encode two frames of phase-shifted sinusoidal fringes in the R channel and B channel of the color image, and obtain a color distorted image of the object by a camera.

[0068] The expression of color distorted image is:

[0069] Step 2: Use the color separation method to separate and obtain two frames of phase-shifted fringe images in the R and B channels of the color distorted image: and

[0070] Step 3: Based on the acquired two-frame phase-shift fringe image, the phase distribution of the object under test is obtained by using the non-filtered ellipse algorithm:

[0071] Step 4: According to the phase distribution of the object being measured, Recover the 3D shape data of the object.

[0072] In summary, the present invention provides a single-frame color stripe three-dimensional imaging method, which encodes two frames of phase-shifted sinusoidal stripes in the R and B channels of a color image, obtains a color distorted image of an object, separates and obtains two frames of phase-shifted stripe images, and uses a filter-free ellipse algorithm and the phase-height mapping formula of the object to restore the three-dimensional shape data of the object. The single-frame color stripe three-dimensional imaging method of the present invention has strong robustness, high precision, and fast imaging, and can retain more detailed information of the object, providing technical support for the development of the field of high-speed three-dimensional measurement.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A single-frame color stripe three-dimensional imaging method, characterized in that: The single-frame color stripe three-dimensional imaging method comprises: A frame of color image is projected onto the object to be measured, and a color distorted image of the object is acquired by a camera, wherein two frames of phase-shifted sinusoidal fringes are encoded in the R channel and the B channel of the color image; A color separation method is used to separate and obtain two frames of phase-shifted fringe images in the R and B channels of the color-distorted image; Based on the acquired two-frame phase-shift fringe images, the phase distribution of the object under test is obtained by using the non-filtered ellipse algorithm; According to the acquired phase distribution of the measured object, the three-dimensional shape data of the object is restored based on the phase-height mapping formula of the object.

2. The single-frame color stripe three-dimensional imaging method according to claim 1, characterized in that: The expression of color distorted image is: Where I represents the light intensity distribution of a frame of color distorted image captured by the camera; a r and a b Corresponds to the background intensity in the R and B channels of the color image respectively; b r and b b Respectively represent the modulation degree in the R and B channels of the color image; is the phase distribution of the object being measured; π / 3 represents the phase shift of the two-frame stripes in the R and B channels of the color image; (x, y) is the light intensity position of the color distortion image.

3. The single-frame color stripe three-dimensional imaging method according to claim 2, characterized in that: The expressions of the two phase-shifted fringe images obtained separately are: and Among them, I r and I b Respectively represent the light intensity distribution of two frames of phase-shifted fringe images separated from the color distortion image; A r and A b Respectively represent the background intensity separated from the R and B channels of the color distorted image; B r and B b They represent the modulation degrees separated from the R and B channels of the color distorted image respectively; δ is the phase shift of the two frames of phase-shifted fringes separated from the R and B channels of the color distorted image.

4. The single-frame color stripe three-dimensional imaging method according to claim 3, characterized in that: The phase distribution of the object under test is: in, 5. The single-frame color stripe three-dimensional imaging method according to claim 4, characterized in that: The phase-height mapping formula of an object is Wherein, L is the vertical distance from the camera to the object in the three-dimensional imaging device; d is the distance from the projected light source to the camera; f is the frequency of the color distorted image; and h is the three-dimensional shape data of the object.

Images