CN107610183A - New striped projected phase height conversion mapping model and its scaling method - Google Patents

Abstract

The invention discloses a novel fringe projection phase-height conversion mapping model and calibration method: The calibration target is placed in the junction of the camera field of view and the projection area of the projector, and the calibration target image is taken, the projection stripe is emitted, and the image is taken at the same time; the calibration target is placed in another position, and the calibration target is different from the previous posture, repeat the above; the collection is enough Image; extract the image coordinate information of feature points, use interpolation to calculate the absolute phase value of the corresponding feature point, and calibrate the camera; convert all the coordinate values of the feature points to CCS, and use the information of the feature points to calculate each parameter in the phase-height conversion mapping model . The invention solves the problems of poor applicability in the calibration technology, strict requirements on the relative poses of the camera and the projector, high complexity of the model algorithm, complex calibration process and error accumulation.

Description

A new fringe projection phase-height conversion mapping model and its calibration method

technical field

The invention relates to optical three-dimensional detection technology, more specifically, relates to a novel fringe projection phase-height conversion mapping model and a calibration method thereof.

Background technique

System calibration technology has a great influence on the accuracy, speed and system composition of fringe projection three-dimensional measurement system. Existing calibration technology can be divided into two types: calibration technology based on stereo vision and phase-height conversion technology.

Inspired by the binocular vision system, many researchers have studied and improved stereo vision-based calibration techniques. In order to realize three-dimensional measurement, the internal parameters of the projector and the camera, as well as the rotation matrix and translation vector between the two need to be calibrated and calculated. Zhang and Huang proposed a calibration method in which a projector "shoots" an image like a camera. This method calibrates the projector and establishes the spatial relationship between the projector and the camera by projecting a series of horizontal and vertical stripes. Li et al. used the method of pre-distorting projected fringes to eliminate the influence of projector lens distortion. To further improve the measurement accuracy, Li and Zhang proposed an algorithm to estimate the optimal projection angle of the projector. Recently, Chen et al. proposed a self-calibration method to realize the online calibration of the fringe projection measurement system. Due to the need to project various patterns to calibrate the projector and calculate the spatial relationship between the projector and the camera, stereo vision-based calibration techniques are only applicable when the projector is a liquid crystal display (LCD) or a digital microlens array (DMD). However, in some cases, such as moiré fringe projection systems, fiber optic interference projection systems and scanning strobe fringe projection systems, this technique is no longer applicable because the projectors in these systems cannot be seen as "reverse" camera.

Another branch is phase-height conversion calibration technology. This model does not consider the calibration of the projector, but directly establishes the relationship between phase and height through a mathematical model. Therefore, it is not bound by the type of caster. Inspired by the interpolation method, Léandry et al. proposed a polynomial mapping model to establish the phase and height mapping relationship. In order to achieve high measurement accuracy, the degree of the polynomial needs to be not less than 4, so the measurement process is time-consuming and not suitable for real-time measurement systems. Lu et al. proposed a phase-height conversion method based on fringe geometric constraints. This method has high measurement accuracy and strong robustness, but also has the disadvantage of large amount of calculation. Du et al. used the camera pinhole model combined with ray tracing theory to establish the mapping relationship between phase and height. Huang improved the accuracy of this model by considering the distortion of the camera lens. The corresponding calibration methods require gauge blocks and reference surfaces of different heights, thus limiting their range of application. In addition, there are 34 model parameters in the literature, which is computationally intensive. Tavares et al proposed a mapping relationship between phase difference and height by using experimental experience. Zhang et al. established a one-to-one mapping formula between world coordinates and phase difference by means of polynomial mapping. The methods in the literature are essentially pixel-level calibration methods using look-up tables (LUTs). These methods rely on the precise phase value of each pixel in the phase map, so the calibration plate needs to be moved enough, and the calibration process is time-consuming. In addition, both models need a reference plane to calculate the phase difference, which will cause the problem of error accumulation.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art, by establishing a virtual camera coordinate system and analyzing the conversion relationship between the camera coordinate system and the projector coordinate system of the fringe information, providing a three-dimensional measurement system for fringe projection The improved phase-height conversion mapping model and calibration method solve the problems of poor applicability in the above-mentioned calibration technology, strict requirements on the relative pose of the camera and the projector, high complexity of the model algorithm, complex calibration process, and error accumulation, etc. The problem.

The purpose of the present invention can be achieved through the following technical solutions.

A new fringe projection phase-height conversion mapping model, the phase-height conversion mapping model is:

in,

k _ij =b ₃ p _ij +b ₄ q _ij

[uv] ^T represents the image coordinates without distortion correction; [u"v"] ^T is the transformed image coordinates _{; the dot OP in the projector coordinate system PCS represents the luminous point, and the X P axis} is parallel to the projected fringe phase change The direction of the Y _P axis is perpendicular to the direction of the phase change of the projected fringe, and the Z _P axis is perpendicular to the phase plane of the projected fringe. The coordinates of any point in the projector coordinate system PCS are expressed as [X _P Y _P Z _P ] ^T , in the projected In the sensor coordinate system PCS, the phases of the spatial points on the same ray are the same, φ, and at the same height Z _P , the phase value changes from φ ₀ to φ ₁ , and the corresponding X _P variation range is [X _P (φ ₀ ),X _P (φ ₁ )]; w is the scale factor; T _P is the translation vector, T _P ＝[t _X t _Y t _Z ] ^T ; [fu f _v ] ^T represents the focal length of the lens, [ _{u o} v _o ] ^T is the center coordinate of the image; s is the distortion coefficient of the image coordinate axis.

In order to reduce the complexity of the algorithm and realize real-time measurement, the look-up table LUT method is used to define

Then the height conversion mapping model _Zc is simplified as:

The purpose of the present invention can be achieved through the following technical solutions.

A calibration method for a novel fringe projection phase-height conversion mapping model, comprising the following steps:

Step 1, place the calibration target in the area at the junction of the camera field of view and the projection area of the projector, the camera captures the image of the calibration target, then the projector emits projection stripes, and the camera captures images at the same time;

Step 2, place the calibration target at another position in the junction of the camera field of view and the projection area of the projector, and the calibration target is different from the previous posture, repeat step 1;

Step 3, repeat step 2 until enough images are collected, usually 2 to 10 groups of images;

Step 4, extract the image coordinate information of the feature points, and use the interpolation method to calculate the absolute phase value of the corresponding feature points, and calibrate the camera;

Step 5: Convert the coordinate values of all feature points to the camera coordinate system CCS, and use the information (Z _C ; uv φ) of the feature points to calculate each parameter in the new fringe projection phase-height conversion mapping model of the present invention.

Compared with the prior art, the beneficial effects brought by the technical solution of the present invention are:

Aiming at the fringe projection measurement system, the present invention proposes an improved phase-height mapping model by establishing a virtual camera coordinate system and analyzing the conversion relationship between the projected fringe information between the projector coordinate system and the camera coordinate system. The model proposes a novel calibration method. Compared with the previous mapping model and calibration method for the fringe projection measurement system, the model proposed in this paper not only does not have strict requirements on the relative pose of the projector and the camera, but the calibration model algorithm has low complexity and can achieve fast and accurate 3D measurement. The corresponding calibration method is simple and efficient. Since the phase-height mapping model and the calibration method proposed by the present invention have the above advantages, they can be applied to field calibration.

Description of drawings

Figure 1 is a schematic diagram of the projector coordinate system PCS;

Fig. 2 is a schematic diagram of the virtual camera coordinate system CCS' and the camera coordinate system CCS;

Figure 3 is a schematic diagram of the calibration of the fringe projection phase-height conversion mapping model;

Fig. 4 is a calibration site map using the fringe projection phase-height conversion mapping model;

Fig. 5 is a schematic diagram of the measured object measured by this model;

Fig. 6 is a schematic diagram of reconstruction information of feature points used for calibration;

Figure 7 is a schematic diagram of the results of three-dimensional measurement using this model.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings.

As shown in Figure 1, a projector coordinate system PCS is established, where the dot OP represents the luminous point, the X _P axis is parallel to the direction of the phase change of the projected fringe, the Y _P axis is perpendicular to the direction of the projected fringe phase change, and the Z _P axis _is vertical on the phase plane of the projected fringes. Therefore, the coordinates of any point in the projector coordinate system PCS can be expressed as [X _P Y _P Z _P ] ^T . It can be seen from Fig. 1 that in the projector coordinate system PCS, the phases of the spatial points on the same ray are the same, all of which are φ. At the same height Z _P , the phase value changes from φ ₀ to φ ₁ , and the corresponding change range of XP is [X _P (φ ₀ ),X _{P (} φ ₁ )]. For any ray emitted from _OP , equation (1) can be obtained:

X _P ＝wZ _P (φ-φ ₀ )+X _P (φ ₀ ) (1)

where w is the scaling factor. The coordinate transformation formula from the camera coordinate system CCS to the projector coordinate system PCS is:

[X _P Y _P Z _P ] ^T ＝T _P +R _P [X _C Y _C Z _C ] ^T (2)

Among them, R _P is the rotation matrix, T _P is the translation vector, [X _C Y _C Z _C ] ^T is the coordinates in the camera coordinate system,

T _P ＝[t _X t _Y t _Z ] ^T

Here, a virtual camera coordinate system CCS' is defined so that it has the same posture as the projector coordinate system PCS and the same position as the camera coordinate system CCS, as shown in Figure 2 and formula (3).

[X _P Y _P Z _P ] ^T ＝T _P +[X _C' Y _C' Z _C' ] ^T (3)

Wherein, [X _C' Y _C' Z _C' ] ^T ＝ R _P [X _C Y _C Z _C ] ^T .

Putting formula (3) into formula (1), we can get formula (4):

X _C' +t _X ＝w(Z _C' +t _Z )(φ-φ ₀ )+X _P (φ ₀ ) (4)

Putting the camera pinhole imaging model into Equation (4), Equation (5) can be obtained:

in,

In the above formula, [X _C' Y _C' Z _C' ] ^T represents the coordinates in the camera coordinate system CCS'; [f _u f _v ] ^T represents the focal length of the lens, [u _o v _o ] ^T is the image center coordinates; s is the distortion factor for the image coordinate axes. Expand equation (3) and divide X _C' and Y _C' by Z _C ' respectively, and use the camera imaging model to obtain equation (6):

in,

Using Taylor series to expand formula (6), the result is as formula (7),

The distortion of the camera lens is corrected, and the camera lens distortion model is shown in formula (8),

Among them, [uv] ^T represents the image coordinates without distortion correction, [u _un v _un ] ^T represents the corrected image coordinates; e ₁ , e ₂ and e ₃ represent the radial distortion parameters, g ₁ and g ₂ represent the cut to the distortion parameter, Indicates the distance between the image coordinate point and the center point. In order to avoid searching for the image center coordinate [u _o v _o ] ^T , expand (8). At the same time, expand formula (7). The expanded results of Equation (7) and Equation (8) can be expressed by Equation (9), where [u"v"] ^T is the transformed image coordinate,

Considering the distortion of the camera lens in the camera coordinate system CCS, formula (9) is brought into formula (5), and the novel fringe projection phase-height conversion mapping model Z _C (u, v, φ) of the present invention is obtained, which can be expressed as for:

Among them, k _ij =b ₃ p _ij +b ₄ q _ij . Equation (10) can be considered as the case where the image coordinates in CCS are converted to image coordinates in CCS' after correction of camera lens distortion.

The parameters in formula (10) can be calculated by formula (11), where N is the total number of feature points extracted from the calibration target. Estimating the minimum value of equation (11) is a nonlinear optimization process, which can be calculated by the Levenberg-Marquardt algorithm.

Usually, when the number of parameters n in formula (10) reaches 3 or 4, a better fitting effect can be achieved. When all the parameters are estimated, the height value Z _C can be obtained by using Equation (10), while X _C and Y _C can be obtained by Z _C , Equation (8) and the camera pinhole imaging model.

In order to reduce the complexity of the algorithm and realize real-time measurement, the look-up table LUT method is considered here, and the definition formula (12) is:

Then the novel fringe projection phase-height conversion mapping model of the present invention can be simplified as:

The Z_LUT[u,v] of each pixel is pre-calculated, and the amount of calculation during measurement can be significantly reduced. Similarly, the measurement in the X and Y directions can also use this method to reduce the amount of calculation and improve the measurement speed.

The calibration method of the novel fringe projection phase-height conversion mapping model of the present invention, as shown in Figure 3, the specific steps are as follows:

Step 1: Place the calibration target in any area at the junction of the camera's field of view and the projection area of the projector. First, the projector does not need to emit any projected fringes, and the camera captures the image of the calibration target to extract the feature points of the calibration target; then, the projector emits the projected fringes, and the camera takes images at the same time to obtain the absolute phase of the feature points.

Step 2, place the calibration target at another position in the junction of the camera field of view and the projection area of the projector, and ensure that the calibration target is different from the previous posture, and repeat step 1.

Step 3, repeat step 2 until enough images are collected, generally 2 to 10 groups of images. In fact, all parameters can be calculated with only 2 sets of images. Nevertheless, usually at least 5 sets of images are required to achieve sufficient accuracy.

Step 4, extract the image coordinate information of the feature points, calculate the absolute phase value of the corresponding feature points by interpolation method, and calibrate the camera.

Step 5: Convert the coordinate values of all feature points to the camera coordinate system CCS, and use the information (Z _C ; uv φ) of the feature points to calculate each parameter in the new fringe projection phase-height conversion mapping model of the present invention.

As shown in Figure 4, the camera, projector and its bracket are installed on the optical platform as shown in the figure, and the relative pose of the camera and projector is not strictly required. As shown in Figure 3 and the process described above, the computer controls the projector to emit projection stripes, and at the same time uses the camera to shoot the calibration target image; after image processing, the image coordinates of the feature points are extracted, and the image coordinates of the feature points and the image coordinates of the feature points in the camera coordinate system are combined. The coordinates are brought into the phase-height conversion mapping model proposed by the present invention to obtain parameters; after calculating all the parameters in the model, use this model to measure the measured object as shown in Fig. 5 .

According to the above method, the model proposed by the present invention and its calibration method are experimentally verified. When the nonlinear number n=4 in the model, the reconstruction information of the feature points used for calibration is shown in Figure 6, and the results of three-dimensional measurement using this model are shown in Figure 6. As shown in Figure 7, the time taken for the measurement is 11 milliseconds.

Although the function and working process of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the above-mentioned specific functions and working process, and the above-mentioned specific implementation is only illustrative, rather than limiting. Under the enlightenment of the present invention, those skilled in the art can also make many forms without departing from the spirit of the present invention and the scope protected by the claims, and these all belong to the protection of the present invention.

Claims (3)

1. A novel fringe projection phase-height conversion mapping model is characterized in that the phase-height conversion mapping model is: <mrow><msub><mi>Z</mi><mi>C</mi></msub><mo>=</mo><mfrac><mrow><msub><mi>b</mi><mn>0</mn></msub><mo>+</mo><mi>&amp;phi;</mi></mrow><mrow><msub><mi>b</mi><mn>1</mn></msub><mo>+</mo><msub><mi>b</mi><mn>2</mn></msub><mi>&amp;phi;</mi><mo>+</mo><munderover><mo>&amp;Sigma;</mo><mrow><mi>i</mi><mo>=</mo><mn>0</mn></mrow><mi>n</mi></munderover><munderover><mo>&amp;Sigma;</mo><mrow><mi>j</mi><mo>=</mo><mn>0</mn></mrow><mrow><mi>n</mi><mo>-</mo><mi>i</mi></mrow></munderover><msub><mi>k</mi><mrow><mi>i</mi><mi>j</mi></mrow></msub><msup><mi>u</mi><mi>i</mi></msup><msup><mi>v</mi><mi>j</mi></msup></mrow></mfrac></mrow> in, k _ij =b ₃ p _ij +b ₄ q _ij <mfenced open = "{" close = ""><mtable><mtr><mtd><mrow><msup><mi>u</mi><mrow><mo>&amp;prime;</mo><mo>&amp;prime;</mo></mrow></msup><mo>=</mo><msub><mi>p</mi><mn>00</mn></msub><mo>+</mo><msub><mi>p</mi><mn>10</mn></msub><mi>u</mi><mo>+</mo><msub><mi>p</mi><mn>01</mn></msub><mi>v</mi><mo>+</mo><msub><mi>p</mi><mn>20</mn></msub><msup><mi>u</mi><mn>2</mn></msup><mo>+</mo><msub><mi>p</mi><mn>11</mn></msub><mi>u</mi><mi>v</mi><mo>+</mo><msub><mi>p</mi><mn>02</mn></msub><msup><mi>v</mi><mn>2</mn></msup><mo>+</mo><msub><mi>p</mi><mn>30</mn></msub><msup><mi>u</mi><mn>3</mn></msup><mo>+</mo><mn>...</mn><mo>=</mo><munderover><mi>&amp;Sigma;</mi><mrow><mi>i</mi><mo>=</mo><mn>0</mn></mrow><mi>n</mi></munderover><munderover><mi>&amp;Sigma;</mi><mrow><mi>j</mi><mo>=</mo><mn>0</mn></mrow><mrow><mi>n</mi><mo>-</mo><mi>i</mi></mrow></munderover><msub><mi>p</mi><mrow><mi>i</mi><mi>j</mi></mrow></msub><msup><mi>u</mi><mi>i</mi></msup><msup><mi>v</mi><mi>i</mi></msup></mrow></mtd></mtr><mtr><mtd><mrow><msup><mi>v</mi><mrow><mo>&amp;prime;</mo><mo>&amp;prime;</mo></mrow></msup><mo>=</mo><msub><mi>q</mi><mn>00</mn></msub><mo>+</mo><msub><mi>q</mi><mn>10</mn></msub><mi>u</mi><mo>+</mo><msub><mi>q</mi><mn>01</mn></msub><mi>v</mi><mo>+</mo><msub><mi>q</mi><mn>20</mn></msub><msup><mi>u</mi><mn>2</mn></msup><mo>+</mo><msub><mi>q</mi><mn>11</mn></msub><mi>u</mi><mi>v</mi><mo>+</mo><msub><mi>q</mi><mn>02</mn></msub><msup><mi>v</mi><mn>2</mn></msup><mo>+</mo><msub><mi>q</mi><mn>30</mn></msub><msup><mi>u</mi><mn>3</mn></msup><mo>+</mo><mn>...</mn><mo>=</mo><munderover><mi>&amp;Sigma;</mi><mrow><mi>i</mi><mo>=</mo><mn>0</mn></mrow><mi>n</mi></munderover><munderover><mi>&amp;Sigma;</mi><mrow><mi>j</mi><mo>=</mo><mn>0</mn></mi>mrow><mrow><mi>n</mi><mo>-</mo><mi>i</mi></mrow></munderover><msub><mi>q</mi><mrow><mi>i</mi><mi>j</mi></mrow></msub><msup><mi>u</mi><mi>i</mi></msup><msup><mi>v</mi><mi>i</mi></msup></mrow></mtd></mtr></mtable></mfenced> <mfenced open = "{" close = ""><mtable><mtr><mtd><mrow><msub><mi>b</mi><mn>0</mn></msub><mo>=</mo><mo>-</mo><msub><mi>&amp;phi;</mi><mn>0</mn></msub><mo>-</mo><mfrac><msub><mi>t</mi><mi>X</mi></msub><mrow><msub><mi>wt</mi><mn>2</mn></msub></mrow></mfrac><mo>+</mo><mfrac><mrow><msub><mi>X</mi><mi>P</mi></msub><mrow><mo>(</mo><msub><mi>&amp;phi;</mi><mn>0</mn></msub><mo>)</mo></mrow></mrow><mrow><msub><mi>wt</mi><mi>Z</mi></msub></mrow></mfrac></mrow></mtd><mtd><mrow><msub><mi>b</mi><mn>3</mn></msub><mo>=</mo><mfrac><mn>1</mn><mrow><msub><mi>f</mi><mi>u</mi></msub><msub><mi>wt</mi><mi>Z</mi></msub></mrow></mfrac></mrow></msub>mtd></mtr><mtr><mtd><mrow><msub><mi>b</mi><mn>1</mn></msub><mo>=</mo><mo>-</mo><mfrac><msub><mi>u</mi><mi>o</mi></msub><mrow><msub><mi>f</mi><mi>u</mo>mi></msub><msub><mi>wt</mi><mi>Z</mi></msub></mrow></mfrac><mo>+</mo><mfrac><mrow><msub><mi>sv</mi><mi>o</mi></msub></mrow><mrow><msub><mi>f</mi><mi>v</mi></msub><msub><mi>wt</mi><mi>Z</mi></mrow>msub></mrow></mfrac><mo>+</mo><mfrac><msub><mi>&amp;phi;</mi><mn>0</mn></msub><msub><mi>t</mi><mi>Z</mi></msub></mfrac></mrow></mtd><mtd><mrow><msub><mi>b</mi><mn>4</mn></msub><mo>=</mo><mo>-</mo><mfrac><mi>s</mi><mrow><msub><mi>f</mi><mi>v</mi></msub><msub><mi>wt</mi><mi>Z</mi></msub></mrow></mfrac></mrow></mtd></mtr><mtr><mtd><mrow><msub><mi>b</mi><mn>2</mn></msub><mo>=</mo><mo>-</mo><mfrac><mn>1</mn><msub><mi>t</mi><mi>Z</mi></msub></mfrac></mrow></mtd><mtd><mrow></mrow></mtd></mtr></mtable></mfenced> [uv] ^T represents the image coordinates without distortion correction; [u"v"] ^T is the transformed image coordinates _{; the dot OP in the projector coordinate system PCS represents the luminous point, and the X P axis} is parallel to the projected fringe phase change The direction of the Y _P axis is perpendicular to the direction of the phase change of the projected fringe, and the Z _P axis is perpendicular to the phase plane of the projected fringe. The coordinates of any point in the projector coordinate system PCS are expressed as [X _P Y _P Z _P ] ^T , in the projected In the sensor coordinate system PCS, the phases of the spatial points on the same ray are the same, φ, and at the same height Z _P , the phase value changes from φ ₀ to φ ₁ , and the corresponding X _P variation range is [X _P (φ ₀ ),X _P (φ ₁ )]; w is the scale factor; T _P is the translation vector, T _P ＝[t _X t _Y t _Z ] ^T ; [fu f _v ] ^T represents the focal length of the lens, [ _{u o} v _o ] ^T is the center coordinate of the image; s is the distortion coefficient of the image coordinate axis. 2. the novel fringe projection phase-height conversion mapping model according to claim 1 is characterized in that, in order to reduce algorithm complexity, realize real-time measurement, utilize look-up table LUT method, define <mrow><mi>Z</mi><mo>_</mo><mi>L</mi><mi>U</mi><mi>T</mi><mo>&amp;lsqb;</mo><mi>u</mi><mo>,</mo><mi>v</mi><mo>&amp;rsqb;</mo><mo>=</mo><msub><mi>b</mi><mn>1</mn></msub><mo>+</mo><munderover><mo>&amp;Sigma;</mo><mrow><mi>i</mi><mo>=</mo><mn>0</mn></mrow><mi>n</mi></munderover><munderover><mo>&amp;Sigma;</mo><mrow><mi>j</mi><mo>=</mo><mn>0</mn></mrow><mrow><mi>n</mi><mo>-</mo><mi>i</mi></mrow></munderover><msub><mi>k</mi><mrow><mi>i</mi><mi>j</mi></mrow></msub><msup><mi>u</mi><mi>i</mi></msup><msup><mi>v</mi><mi>j</mi></msup></mrow> Then the height conversion mapping model _Zc is simplified as: <mrow><msub><mi>Z</mi><mi>C</mi></msub><mo>=</mo><mfrac><mrow><msub><mi>b</mi><mn>0</mn></msub><mo>+</mo><mi>&amp;phi;</mi></mrow><mrow><msub><mi>b</mi><mn>2</mn></msub><mi>&amp;phi;</mi><mo>+</mo><mi>Z</mi><mo>_</mo><mi>L</mi><mi>U</mi><mi>T</mi><mo>&amp;lsqb;</mo><mi>u</mi><mo>,</mo><mi>v</mi><mo>&amp;rsqb;</mo></mrow></mfrac></mrow> 3. a calibration method of the novel fringe projection phase-height conversion mapping model described in claims 1 and 2, is characterized in that, comprises the following steps: Step 1, place the calibration target in the area at the junction of the camera field of view and the projection area of the projector, the camera captures the image of the calibration target, then the projector emits projection stripes, and the camera captures images at the same time; Step 2, place the calibration target at another position in the junction of the camera field of view and the projection area of the projector, and the calibration target is different from the previous posture, repeat step 1; Step 3, repeat step 2 until enough images are collected, usually 2 to 10 groups of images; Step 4, extract the image coordinate information of the feature points, and use the interpolation method to calculate the absolute phase value of the corresponding feature points, and calibrate the camera; Step 5: Convert the coordinate values of all feature points to the camera coordinate system CCS, and use the information (Z _C ; u v φ) of the feature points to calculate each parameter in the novel fringe projection phase-height conversion mapping model of the present invention.