WO2006000123A1

WO2006000123A1 - System and method of 3d reconstruction of a lamellar and flexible body surface

Info

Publication number: WO2006000123A1
Application number: PCT/CN2004/000681
Authority: WO
Inventors: Jinlian Hu; Binjie Xin
Original assignee: The Hong Kong Polytechnic University
Priority date: 2004-06-23
Filing date: 2004-06-23
Publication date: 2006-01-05

Abstract

The invention relates to a system and a method used for 3D reconstruction of a lamellar and flexible body surface. Said system contains: a background light source which emits an uniform retro-diffuse reflection light with a definite brightness; a sample clamp means for holding a sample to be 3D reconstructed having a peak on which the sample is bent; an image acquisition means which acquires the side projection image of the sample on the peak; a sample drive means which drives the sample on said clamp means to smoothly pass said peak; and a computer. Said computer controls the movement of the sample drive means, receives a sequence of the side projection image of the sample acquired by the image acquisition means, processes and analyzes the image sequence, extracts information about side projection heights of each of image frames, and packs said image according to the acquisition order to obtain a 3D stereo image.

Description

System and method for three-dimensional reconstruction of sheet-type flexible body surface

The invention relates to a system and a method for three-dimensional reconstruction of an object surface, which can be widely applied to appearance detection, feature analysis and quality control of an object surface, and is particularly suitable for three-dimensional reconstruction of a sheet-type flexible body surface. Background technique

Three-dimensional reconstruction technology is widely used in various fields such as industrial production, industrial inspection, space exploration, and scientific research. In general, in order to obtain the three-dimensional shape of an object, the required measurement system can be divided into two categories: mechanical contact measurement and photoelectric non-contact measurement. Photoelectric non-contact measurement can be further divided into: binocular or multi-eye stereo measurement, structural grating, laser triangulation, laser flying spot measurement, Moir interferometry and other methods. Each type of 3D reconstruction technology has its own advantages and disadvantages.

Mechanical contact measurement is mainly applied to the continuous surface of the rigid body, with high precision and stability. For so-called sheet-type flexible bodies, which include: textiles, plastic films, paper and other freely bendable sheet-type materials, this mechanical contact measurement cannot be used. Binocular or multi-view stereo measurement in photoelectric non-contact measurement is based on binocular stereo matching algorithm and camera calibration technology. For surface surfaces without many texture details or dark colors, the measurement accuracy is poor and unstable. Structural grating measurement is based on the principle of coded grating and triangulation. For the surface of a mottled or multi-patterned object, the reconstruction algorithm will fail due to the destruction of the coding pattern of the grating. Laser triangulation and laser flying spot measurement are a point-by-point measurement method with low scanning efficiency and high cost. Mohr interferometry The amount is also not suitable for measuring the surface of mottled, multi-pattern or dark black objects, and the automation of Moiré analysis technology for complex surfaces is also a technical difficulty.

In industrial production, the surface analysis of a sheet-type flexible body material is mainly based on a two-dimensional surface image obtained by light reflection or projection, and the two-dimensional surface image cannot express three-dimensional information and features of the surface of the material. In this context, appropriate 3D reconstruction techniques are needed to extract 3D information and features from the surface of the material. Due to the complexity of the surface of the material, variegated, multi-patterned, dark or black, lack of texture details, etc. often occur. In the face of such complex sample testing types, the selection of several reconstruction techniques described above can only be applied to specific Sample type, cannot cover most sample types. There is therefore an urgent need to provide a three-dimensional reconstruction technique for a versatile flexible material surface that can be applied to various types of flexible material surfaces. Summary of the invention

In view of the above problems, an object of the present invention is to provide a technique for three-dimensional reconstruction which is not affected by factors such as color, texture and gloss of the surface of the sample, and which can quickly and accurately obtain three-dimensional information of the surface of the flexible material.

In order to achieve the above object, the present invention provides a system for three-dimensional reconstruction of a sheet-type flexible body surface, comprising: a background light source for emitting uniform diffuse reflected light having a certain brightness; and a sample holding device Holding a sample to be three-dimensionally reconstructed thereon, the sample holding device has a vertex, the sample is bent at the vertex, and the diffuse light emitted from the background light source is projected to the test An image collecting device for collecting an image of the sample to obtain a side projection image of the sample at the vertex; a sample driving device driven to be clamped in the test The sample on the gripping device passes uniformly through the apex, so that the image is taken The collecting device can sequentially obtain the side projection images at different positions on the surface of the sample; a computer controlling the movement of the sample driving device and receiving the sequence of the side projection image of the sample collected by the image collecting device, The image sequence is processed and analyzed, and the side projection height information of each frame image is extracted, and a three-dimensional stereoscopic image of the surface of the sample is obtained by splicing according to the acquisition sequence.

In another aspect of the invention, a method for three-dimensional reconstruction of a sheet-type flexible body surface is provided, comprising the steps of:

Sampling: collecting a side projection image at each position of a sample to form a side projection image sequence;

Contour extraction: processing each of the side projection images to extract side projection height information of each frame image;

Stitching: The obtained side projection height information is spliced according to the acquisition order, thereby obtaining a three-dimensional stereoscopic image of the surface of the sample.

The invention has the beneficial effects that, because the invention is based on the characteristic that the sheet-type flexible body is easy to bend, the sheet-shaped material is fixed and bent by a curved type sample holding device to obtain a strip-shaped convex surface with a certain curvature; Under the illumination of a backward diffuse reflection light source with a certain brightness, an image acquisition device is used to acquire an image to obtain a side projection image of a strip-shaped convex surface; in addition, the sample surface is continuously rotated by a computer-controlled sample driving device to obtain a sample surface. A series of side projection images of strip-shaped convex surfaces formed by continuous bending at different positions; using image processing and analysis techniques, extracting side projection height information of the sample surface of each frame image in the image series, and splicing the sample according to the acquisition sequence A three-dimensional image of the surface. Therefore, the present invention is a contactless photoelectric measuring method specifically adapted for three-dimensional reconstruction of a sheet-type flexible body surface, which is not subject to the color of the surface of the sample. The three-dimensional information of the surface of the flexible material can be obtained quickly and accurately by the influence of color, texture and gloss. It is suitable for offline detection and online inspection. It can be widely used in textile, printing, packaging and other industries.

The invention is further described below in conjunction with the drawings and specific embodiments. DRAWINGS

1 is a schematic structural view of a three-dimensional reconstruction system for a sheet-type flexible body surface of the present invention; FIGS. 2A and 2B show two embodiments of a curved-type sample holding device of the present invention; FIGS. 3A and 3B The manner of the backward illumination in the present invention is respectively shown;

Figure 4 is a side projection image of the sample after bending;

Figure 5 is a side projection height curve of the surface of the sample;

Fig. 6 is a view showing the configuration of a computer in the present invention.

The reference numerals are as follows:

Light confined space 1

Background light source 2

Sample holding device 3

Bracket 31, 31'

Roller 311

Conveyor belt 312

Chuck 32

Vertex 33

Sample 4 Image acquisition device 7

Rear mirror 80

Beam splitter 81

Computer 10

Image acquisition card 101

Motor driver 102

Image processing module 104

Contour extraction module 1041

Splicing module 1042

The invention is further described below in conjunction with the drawings and examples.

The surface three-dimensional reconstruction system of the present invention is mainly applicable to a sheet-type flexible body material. A flexible body material is defined as: A non-rigid solid material that bends with a certain curvature under a small external force. The sheet-type material is defined as: a continuum having a certain thickness and area size, a large area size which is many times larger than the thickness (usually 20 times or more), and a small difference in thickness.

Referring to Fig. 1, a system for three-dimensional reconstruction of a sheet-type flexible body surface of the present invention comprises: a background light source 2, a sample holding device 3, a sample driving device 5, an image pickup device 7, and a computer 10.

The background light source 2 is an array of point sources or point sources that emit divergent beams for emitting a uniform diffusely reflected light having a uniform brightness. In addition, the background light source 2 can also be equipped with light A system (not shown) that causes the divergent beam to emit a parallel beam or a concentrated beam after passing through the optical system. Moreover, the background light source may be a visible light source, or may be an infrared light source or an ultraviolet light source.

The sample holding device 3 is curved, and a sample 4 to be three-dimensionally reconstructed is fixed on the sample holding device 3. The sample holding device has a vertex 33 at which the sample 4 is bent. The diffused light emitted from the background light source 2 is projected onto the sample 4.

The image capture device 7 is disposed on one side of the sample 4, which may be a CCD camera, a CMOS camera, a digital camera or a digital video camera, which is connected to the computer 10, so that the computer 10 can collect the image in real time through the image capture device 7. The image of the sample 4 gives a sequence of side projection images of the sample 4 at the apex 33.

In the present embodiment, the sample driving device is a motor 5, which is preferably a stepping motor, which is connected to the computer 10, and is driven and controlled by the computer 10. The motor 5 drives the sample 4 clamped on the sample holding device 3 to uniformly pass through the apex 33. As can be seen from Fig. 1, the sample 4 is bent at a vertex 33 at a certain position in the longitudinal direction. Thus, as the sample is driven through the apex at a uniform velocity, each position of the longitudinal direction of the sample 4 can be bent at the apex 33, so that the image acquisition device 7 can sequentially obtain different surface of the sample. A side projection image at the location. In addition, the motor 5 can directly drive the sample holding device 3, and the sample holding device can also be driven by an intermediate transmission mechanism (not shown), which is generally a reduction gear set, so that The sample is moved at an appropriate speed.

The computer 10 of the system is a control center of the entire system and a processing center of the image, as shown in FIG. 6, which includes an image capture card 101, a motor driver 102, and a conventional central processing unit CPU and memory. An image processing module 104. The image capture card and The image acquisition device 7 is connected for digitizing the acquired image and storing it in a memory. The motor driver is coupled to the motor 5 for controlling the motor 5 to operate at a predetermined speed or step.

The image processing module 104 further includes a contour extraction module 1041 and a splicing module 1042, the contour extraction module 1041 is configured to extract side projection height information of each frame image, and the splicing module 1042 is configured to project the side projection The height information is spliced in the sampling order to obtain a three-dimensional image of the surface of the sample. The contour extraction module and the splicing module described above may be implemented by an electronic circuit or a software program running in the computer 10.

As shown in Figs. 2A and 2B, the sample holding device has a curved shape for the flexible material of the present invention. It may be a spike-shaped "A" type as shown in Fig. 2A or a circular-arc "0" type as shown in Fig. 2B, and may include any form formed by planar bending. A common feature of this curved form is that it has a vertex 33 so that each portion of the sample 4 can project a contour onto the image capture device 7 as it passes through the apex 33, completing the data sampling. As shown in Fig. 2A, which is a first embodiment of the sample holding device, which is composed of a holder 31 and a chuck 32, the holder 31 includes three rollers 311 arranged in an "A" shape and a conveyor belt surrounding the roller. 312. The three rollers 311 are rotated by the motor 5 so that the belt 312 is rotated around the rollers, so that the sample 4 fixed to the belt 312 by the chuck 32 also moves with the belt.

Fig. 2B shows another embodiment of the sample holding device, which is also composed of a holder 31' and a collet 32. Similarly, the holder 31' is a roller having a larger diameter, and the motor 5 drives the roller to rotate, and the sample 4 fixed to the roller by the chuck 32 rotates with the roller. The collet 32 is also available in a variety of embodiments, either as a collet chuck or as a magnetic collet. About the sample holding The device has a detailed description in the utility model patent application filed by the inventor of the present application (application number: 03207803. x, invention name: magnetic cloth sample clamping device for digital fabric appearance/surface test assessor), No longer.

In the system of the present invention, the background light source 2, the sample holding device 3 and the image pickup device 7 are configured in a manner of rearward illumination to obtain a projected image of the highest contrast. As shown in Fig. 3A, the rear illumination mode is realized by arranging the sample 4 between the background light source 2 and the image pickup device 7. Thus, the background light source 2 is illuminated from the rear of the sample 4, and a sharp outline of the sample is projected at the image capture device 7.

In addition, the backward illumination mode can also be implemented in another manner. As shown in FIG. 3B, the background light source 2 and the image acquisition device 7 are located on the same side of the sample 4, and a back reflection is disposed behind the sample 4. The mirror 80 is provided with a beam splitter 81 between the background light source 2 and the image acquisition device 7, and the back illumination is realized by back reflection.

In order to achieve an optimal image capturing effect, it is preferable to provide a sealed space 1 capable of isolating natural light, and at least the sample 4, the background light source 2, and the image capturing device 7 are disposed in the sealed space 1, so that a clearer projection can be obtained. image. The confined space 1 can be implemented as a ruled geometry or as an irregular geometry.

Fig. 4 shows a side projection image of a sample at a position of the apex 33, which clearly reflects its outline.

Using image processing and analysis techniques, the image processing module of the present system extracts the side projection height information of the sample surface of each frame image in the image sequence as shown in FIG.

Corresponding to the flexible body surface three-dimensional reconstruction system of the present invention, the present invention also provides a method for three-dimensional reconstruction of a sheet-type flexible body surface, comprising the following steps: Image sampling: collecting a side projection image at each position of a sample to form a side projection image sequence; contour extraction: processing the side projection images to extract side projection height information of each frame image; stitching: according to the collection The obtained side projection height information is sequentially spliced to obtain a three-dimensional stereoscopic image of the surface of the sample.

In addition, before the above steps, the following initialization steps are also included: System startup: The computer, motor, light source, and photoelectric camera system are in working state; System commissioning calibration: Check whether all parts of the system are working properly.

The sampling step further includes the step of: clamping the sample 4 on the sample holding device 3 such that the sample 4 is bent at a vertex 33 of the sample holding device 3; A background light source 2 is disposed on one side of the sample 4; the sample is driven to be continuously bent through the apex 33 of the sample holding device 3; and the side projection of the sample 4 at the vertex position is collected by the image acquisition device 7. An image; the side projection image is projected by the background light source 2.

The algorithm in the three-dimensional reconstruction method and system for the sheet-type flexible body surface mainly focuses on how to separate the side projection height information from the side projection image, wherein the algorithms applicable to the step include:

method 1 :

• Histogram analysis: The histogram is defined as the grayscale distribution of the image. The grayscale image of the side projection of the curved convex surface of the specimen is f (x, y), where (χ, y) is the image coordinate, and f (x, y) is the gray of the pixel at (χ, y) Degree, f (x, y) G [0, 255] o where a gray value of 0 indicates that the pixel is white, and a gray value of 255 indicates that the pixel is black. Its histogram is h ( i ), ie [0, 255]. Take a projected image in the sequence of projected images, which exists in the image Two types of regions: the background region and the sample projection region, and their gray distribution models are close to the Gaussian distribution. Assuming that the mean and variance of the two distributions are (ul, δΐ) and ( _U 2, 52), then the distribution model of the histogram is:

(Ζ·— Μ ₂ ) y{i) = A -e ¹ +A by looking for a function

The minimum value of MSE ∑[ 0-WO] ² gives the best estimate of two Gaussian distributions (ul, δΐ)

Ν ζ = 1

And (u2, δ 2),

Image segmentation: Set the threshold t u u, +u ₂ + λ{δ ~ δ ₂ according to the gray scale distribution of the background and the sample

2 λ is the empirical coefficient, and then binarized, f (x, y)

• Height extraction: In the above binarized image, the area with a pixel value of 255 is the sample, and the area with the pixel value of 0 is the background. According to this feature, the image is scanned to obtain the boundary between the sample and the background. The contour line, and determines the coordinates of each point on the boundary contour line, wherein the coordinates along the vertical boundary direction are height coordinates.

Method 2:

• Edge detection: Edge detection is performed by edge detection algorithm. Common edge detection algorithms include Marr edge detection method, Sobel operator, Robert operator, Laplacian operator and so on.

The Robert operator is an operator that uses local difference operators to find edges. It is given by:

Where / is an input image with integer pixel coordinates. The algorithm for edge detection described above is discussed in detail in the reference "Digital Image Processing, Prentice Hall, 1998" and will not be repeated here.

• Height Extraction: Scans the image and determines the coordinates of each point on the boundary contour based on the detected edge of the contour. The coordinates along the vertical boundary are the height coordinates.

Method 3: Radon Transform: The gray value is summed according to the vertical projection of the image (that is, the Norton transform in the vertical direction), and the gray scale distribution of the image in the vertical direction is obtained. Since the accumulation of gradation is linear with the thickness of the sample, the surface profile height of the sample can be obtained by dividing by a certain proportional coefficient.

Specifically, the gray value of the projected image at the (x, y) point is /(χ, where xe [l, M] is the image abscissa, and ye [l, N] is the image ordinate, then the frame The Norton transform of the image in the vertical direction? (x) = fix, ie for each position x in the horizontal direction, the gray value of the image is y = l

Accumulating the sum in the straight direction, obtaining the Norton transform R (x) at the horizontal position X, performing the above-mentioned Norton transform on all horizontal positions X ≡ [1 , M], that is, extracting the gray scale distribution of the image in the vertical direction; The cumulative RG of the gradation in the direction is linear with the thickness of the sample at the horizontal position. Therefore, by dividing the cumulative value R (x) by a certain proportional coefficient, the sample can be obtained on the abscissa (horizontal position). The height of the surface profile at X.

Further, the method for three-dimensional reconstruction of a sheet-type flexible body surface of the present invention can be used for both off-line detection and on-line detection. Industrial applicability

System and method for three-dimensional reconstruction of a sheet-type flexible body surface according to the present invention, based on a sheet type The flexible body is easy to bend, and the thin-type sample holding device is used to fix and bend the sheet-shaped material to obtain a strip-shaped convex surface with a certain curvature; the sample is contained in a sealed space capable of isolating natural light, and has uniform brightness. After the back-diffuse light source is irradiated, the image is acquired by the photoelectric imaging system to obtain a side projection image of the strip-shaped convex surface; the sample is driven continuously by the computer-driven sample driving device, and the surface of the sample is obtained at different positions. A series of side projection images of a strip-shaped convex surface formed by continuous bending; using image processing and analysis techniques, extracting side projection height information of a sample surface of each frame image in the image series, and splicing according to the acquisition sequence to obtain a three-dimensional surface of the sample surface image. It can be seen from the above that the three-dimensional reconstruction system and method proposed by the present invention are not affected by the physical properties of the surface of the sample, and the accurate three-dimensional surface of the sample can be obtained whether it is a striped sample or a dark sample. model. Therefore, the drawbacks of the prior art are effectively overcome.

Although the present invention has been disclosed in the above embodiments, the present invention is not limited to the contents of the embodiments, and those skilled in the art can make any of the present invention without departing from the spirit and scope of the invention. Change and retouch. The scope of the invention is defined by the appended claims.

Claims

Rights request

What is claimed is: 1. A system for three-dimensional reconstruction of a sheet-type flexible body surface, comprising: a background light source for emitting a uniform diffuse reflection light having a certain brightness; and a sample holding device thereon Holding a sample to be reconstructed in three dimensions, the sample holding device has a vertex, the sample is bent at the vertex, and the diffuse reflection light emitted from the background light source is projected onto the sample;

An image capture device for acquiring an image of the sample to obtain a facet projected image of the sample at the vertex;

a sample driving device that drives the sample clamped on the sample holding device to uniformly pass through the apex, so that the image capturing device can sequentially obtain a side projection image at different positions on the surface of the sample ;

a computer that controls the movement of the sample driving device, receives a sequence of side projection images of the sample collected by the image acquisition device, processes and analyzes the image sequence, and extracts a side of each frame image Projecting height information, splicing the side projection height information of each frame image according to the acquisition order to obtain a three-dimensional stereoscopic image of the sample surface.

2. The system for three-dimensional reconstruction of a sheet-type flexible body surface according to claim 1, wherein the background light source is an array of point light sources or point light sources that emit divergent beams, and may be equipped with an optical system such that The diverging beam passes through the optical system to emit a parallel beam or a concentrated beam; the background source may be a visible light source, or an infrared light source or an ultraviolet light source.

3. The system for three-dimensional reconstruction of a sheet-type flexible body surface according to claim 1, wherein the sample holding device has a bracket (31, 31') and a plurality of chucks (32), An apex is formed at a top end of the bracket, and the sample is clamped on the bracket by the collet, and is fixed The sample set on the sample holding device is bent with a certain curvature to facilitate the collection of contours at different positions of the sample.

4. A system for three-dimensional reconstruction of a sheet-type flexible body surface according to claim 3, wherein said bracket (31) comprises three rollers (311) arranged in an "A" shape and a conveyor belt 312, said conveyor belt wrapping The roller forms the bracket; the chuck clamps the sample on the conveyor belt.

A system for three-dimensional reconstruction of a sheet-type flexible body surface according to claim 3, wherein said holder (31') is a large diameter roller.

A system for three-dimensional reconstruction of a sheet-type flexible body surface according to claim 1, wherein said sample driving device is a motor (5).

7. The system for three-dimensional reconstruction of a sheet-type flexible body surface according to claim 1, wherein the image acquisition device is one selected from the group consisting of: a CCD camera, a CMOS camera, a digital camera, and a digital video camera.

8. The system of three-dimensional reconstruction of a sheet-type flexible body surface according to claim 6, wherein the computer comprises an image acquisition card, a motor driver and an image processing module.

(104); the image acquisition card is connected to the image collection device, used to digitize an image collected by the image acquisition device, and stored in a memory; the motor driver is connected to the motor, and is used for Controlling the operation of the motor.

The system for three-dimensional reconstruction of a sheet-type flexible body surface according to claim 8, wherein the image processing module (104) further comprises a contour extraction module (1041) and a splicing module (1042), The contour extraction module is configured to extract side projection height information of each frame image, and the splicing module is configured to project side height information of each of the extracted image frames The three-dimensional images of the surface of the sample are obtained by splicing in the sampling order.

10. The system for three-dimensional reconstruction of a sheet-type flexible body surface according to claim 1, wherein the background light source, the sample holding device and the image capturing device are configured in a backward illumination manner to obtain the highest contrast ratio. Projection image.

11. The system for three-dimensional reconstruction of a sheet-type flexible body surface according to claim 10, wherein the sample holding device is disposed between the background light source and the image capturing device to realize backward illumination. .

12. The system for three-dimensional reconstruction of a sheet-type flexible body surface according to claim 10, wherein the background light source and the image capturing device are located on the same side of the sample holding device, and a rear mirror (80) Provided behind the sample, a beam splitter (81) is disposed between the background light source and the image acquisition device, and the back illumination is achieved by back reflection.

13. A system for three-dimensional reconstruction of a sheet-type flexible body surface according to claim 6, wherein said motor is coupled to said sample holding device by an intermediate transmission mechanism.

14. A method for three-dimensional reconstruction of a sheet-type flexible body surface, comprising the steps of:

Stitching: The obtained side projection height information is spliced in the order of collection, thereby obtaining a three-dimensional stereoscopic image of the surface of the sample.

15. The method for three-dimensional reconstruction of a sheet-type flexible body surface according to claim 14, The sampling step further includes the following steps:

Holding the sample on a sample holding device such that the sample is bent at an apex of the sample holding device;

Providing a background light source on one side of the sample;

Driving the sample to continuously bend through the apex of the sample holding device;

A side projection image of the sample at the vertex position is acquired by an image acquisition device; the side projection image is projected by the background light source.

The method for three-dimensional reconstruction of a sheet-type flexible body surface according to claim 14, wherein the contour extraction step further comprises the following three steps:

Histogram analysis: Histogram analysis is performed on the side projection image of the curved convex surface of the sample, and the mean and variance of the Gaussian distribution of the gray background of the background and the sample are respectively obtained in the projected image; image segmentation, according to the background and the sample The mean value and variance of the gray distribution, a threshold is set, and the image is binarized according to the threshold, that is, the gray value of the pixel is greater than the threshold, and the pixel value of the pixel is 255, and the pixel If the gray value of the point is smaller than the threshold, the pixel value of the pixel is 0;

Height extraction, based on the region where the pixel value of the image is 0, the region with the pixel value of 255 is the sample, scan the image, obtain the boundary contour of the background and the sample, and determine the coordinates of each point on the boundary contour line. , where the coordinates along the vertical boundary direction are height coordinates.

17. The method for three-dimensional reconstruction of a sheet-type flexible body surface according to claim 14, wherein the contour extraction step further comprises the following two steps:

• Edge detection: Edge detection is performed by an edge detection algorithm including Marr edge detection method, Sobel operator, Robert operator, and Laplacian operator; , height extraction: scan the image, according to the detected contour edge, determine the coordinates of each point on the boundary contour line, wherein the coordinate along the vertical boundary direction is the height coordinate.

18. The method for three-dimensional reconstruction of a sheet-type flexible body surface according to claim 14, wherein the contour extraction is implemented by a Norton transform step: cumulatively summing the image-like gray values in a vertical direction, Extracting the grayscale distribution of the image in the vertical direction; for each position in the horizontal direction, since the accumulation of the grayscale in the vertical direction is linear with the thickness of the sample at the horizontal position, the cumulative value is divided by a certain value The scale factor gives the surface profile height at each horizontal position of the specimen.

19. A method for three-dimensional reconstruction of a sheet-type flexible body surface according to claim 14, wherein: the method is suitable for both offline detection and on-line detection.