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The height estimation of the target object is an important research direction in the field of computer vision. The three-dimensional reconstruction of structured light has the characteristics of high precision, noncontact, and simple structure and is widely used in military simulation and cultural heritage protection. In this paper, the height of the target object is estimated by using the word structure light. According to the height dictionary, the height under the offset is estimated by the movement of the structured light to the object. In addition, by effectively preprocessing the captured structured light images, such as expansion, seeking skeleton, and other operations, the flexibility of estimating the height of different objects by structured light is increased, and the height of the target object can be estimated more accurately.

In recent years, with the development of science and technology, three-dimensional reconstruction technology as an important part of machine vision has attracted more and more attention, especially in industrial product design and cultural heritage protection. However, based on the three-dimensional reconstruction of the surface of the structured light, it is possible to reconstruct the surface of the object by laser scanning without touching the object, which can greatly protect the original culture from damage in the cultural heritage. This can make a great contribution to the excavation of ancient excellent culture and the spread of Chinese civilization. Therefore, the three-dimensional reconstruction based on structured light has important practical significance for the protection of cultural heritage and the design of industrial products [

3D surface reconstruction is to rebuild the actual shape of the real life of the object, which has become an important topic in computer vision. And researchers from all over the world have made considerable achievements in this regard. The structure of three-dimensional reconstruction system for structured light mainly includes cameras and lasers; you can use the ordinary camera to complete the task of detection, but because of the different structure of the light, the experimental results will be affected. According to the laser projection of different ways can be divided into point, line, and multiline structure of light. Point structure light for the laser projector projection of a beam of light, measured the surface of the measured object a point; the camera can only get this photo of the three-dimensional coordinates of the information; the amount of information is too small; a word line structure light projector projects a light plane; the intersection of the light plane and the measurement object can draw a cross section information; the algorithm is easy to use; multirow structured light projects multiple light planes; the surface of the object forms multiple laser lines; pictures can give us multiple cross-section information, which is large amount of information; however, it is necessary to increase the matching of light bars, which greatly improves the difficulty and complexity of the algorithm and is still in the stage of experimental research [

At home and abroad for the 3D surface reconstruction conducted in-depth study, Horn [

In the process of 3D reconstruction of structured light, in order to reconstruct the 3D structure of the 2D image taken by the camera, the camera parameter must be calibrated and the geometric model of camera imaging should be built; that is, the camera’s internal and external parameters should be measured. Then, the correspondence between the image and the spatial point is constructed; that is, the laser plane equation is calibrated. This paper mainly used Zhenyou Zhang camera calibration method [

The camera model is very similar to the model used by Heikkila and Silven of the University of Oulu in Finland. We especially recommend their CVPR'97 paper: the function of the four-step camera calibration program with an implicit image correction [

In the camera model, the parameters are as follows:

Focal length: stored in pixels in 2

Main points: the coordinates of the primary point are stored in the 2

Skew factor: define the skew factor for the angle between the

Distortion: the image distortion factor (radial and tangential distortion) is stored in the 5

Let

Let

Let

Therefore,

Once the distortion is applied, the final pixel coordinates of the P on the projection plane are

Thus, the pixel coordinate vector

In reconstructing the surface height of the object, we are using triangles similar to the surface reconstruction of the object. In the case of similar judgments, the degree of use of the triangles is the same. But when the triangles are similar, we use the same degree of the angle of the two similar triangles [

In order to obtain the three-dimensional information of the object in the structured light measurement, the basic idea is to use the geometric information in the structured light image to help provide the geometric information in the scene [

As shown in Figure

Dimensional reconstruction of structured light.

A′ is the image of A in the world coordinate system; the line of sight OA′ is

In the world coordinate system, the plane equation of structured light is

Because

The inverse relationship is

Thus, it can be learned that the correspondence between pixel points and world coordinate points is

As shown in Figure

Schematic diagram of experimental laser photography.

Due to shooting methods and other reasons, there is a certain amount of noise in the loaded laser mask. Here to solve the two main noises, other light source interference and laser line breakage, the main method is to filter the connected domain to remove other light source interference, through the expansion of the skeleton to avoid laser line breakage.

Filtering the connected domain is to keep the connected domain in the image and remove those nonconnected pixels. Here is the use of bwareaopen function; this function is also called delete the minimum area function; you can set the minimum size of the connected domain, which has the default value of 8. In the experiment, this value is set to 2 in this paper. In the design of the function, after loading the laser mask, the image will be converted to a black and white image; the image matrix is shown as 0-1 matrix. However, due to other light sources, there are some interference points in the image (as shown in Figure

With interference laser mask.

These interference points do not exist in the form of communication, but in the form of pixels scattered in the image, so you can filter the connection domain and remove these interference points, and this operation will have a sharp effect on the laser itself. That is, around the laser line “burr” will be deleted, which will make the reconstruction results more smooth. The effect after screening is shown in Figure

Remove the interference after the laser mask.

Laser mask image screening connection domain processing will be loaded; the laser line itself will be interference. The biggest problem is that the laser line is broken. In view of this situation, first of all, we have carried out the expansion operation and first broken the laser line through the expansion of the connection; the effect is shown in Figure

The effect after expansion.

After the laser line is inflated; the laser light becomes thicker. Obviously, we cannot use this inflated image directly to a high degree of reconstruction. All we have to do is to get a thin continuous laser line, and we cannot change the shape of the original laser line. So we took the skeleton operation. This operation will be the same as the original laser line shape of the laser line, and this laser line is a single row of pixels of the laser line, which is in line with our requirements. The effect is shown in Figure

The effect after seeking skeleton operations.

The main content of this part is taking the main process after rebuilding a single laser height: superposition and interpolation. The superposition is mainly a comprehensive display of each reconstructed laser height. Interpolation is the linear interpolation of the resulting discrete data, making it appear continuously and smoothly.

This paper is designed to reconstruct the height of the surface of the object by using a single word structure, but a laser can only reproduce the height of the laser line (Figure

Single laser height reconstruction.

Therefore, if the we use word structure of light on the surface of the three-dimensional reconstruction, there are two ways. One is to take the image into video and then a frame of a video of the laser line in a high degree of reconstruction, which will get a relatively smooth surface of the object, but this method is more difficult to shoot, the data being many. The second is that the isometric image is highly reconstructed and then interpolated. This method is relatively simple. No matter what method is used, the final reconstruction is a section of the height matrix. Therefore, to sum up the height of each reconstruction, each height matrix in a world coordinate system is displayed (shown in Figure

Multiple poststack height reconstruction.

Because we need to ensure the laser line and the location of the mandrel and their angle in the shooting of the image, we can only be moving objects when we shoot an object. Only in this way can we ensure the same angle between the laser line plane and the camera object, in order to accurately rebuild the height of the object, that is, to ensure that the angle between XcOw and OcOw. Therefore, when shooting a number of laser lights to rebuild the height we can only move the object to shoot, but the image will be in the same position if we shoot laser line. Then, the reconstruction of the laser height will be superimposed. Therefore, it is necessary for man-made reconstruction of the laser height according to the distance when the object is moving evenly distributed such that each height line is shown to be scattered (shown in Figure

As the design uses a word structure of light on the surface of the three-dimensional reconstruction of the object, the word structure of light can only rebuild a laser line under a height. After the above superposition, we will get a lot of high degrees of reconstruction, but these are not continuous but a height line. In order to rebuild these lines into the surface, there are two ideas: one is to take a lot of height lines for superposition; the other is to take a limited height line for superposition and then interpolation. These two methods can get a smooth surface reconstruction of the object, but the former method of workload is too large; here we use the second method, the height of the superposition of the interpolation operation, and the superposition of the use of the griddata function and of the discrete height of the linear interpolation to get a smooth surface of the object and the effect is shown in Figure

The results of the reconstruction after interpolation.

This chapter is mainly to reconstruct the experimental results according to the physical comparison and analyze the advantages and disadvantages of the reconstruction of the experimental results.

In order to better test the continuity of reconstruction of a high degree, this paper is selected as a hemisphere, because the hemisphere in the rise or fall is continuous, so this can better reflect the effect of reconstruction. And in order to reduce the reflection of interference that the laser irradiation on the surface of the object caused, we then select the rough diffuse reflector to take pictures. As can be seen from Figure

Hemispherical picture taken in kind.

The three-dimensional reconstruction of structured light is based on the degree of deviation of the laser line and then multiplied by the height of the offset to reconstruct the height of the object. But in the process of readding because the reconstruction of the height is too small, basically we do not see the surface of the reconstruction of the object.

Therefore, this article will rebuild the height in accordance with a certain proportion of the amplification. But for the comparison of the actual object and the reconstruction height, it can be seen that the height of the reconstruction is higher than the actual height. The results are shown in Figures

Highest height of reconstruction.

Height of the actual object.

From the comparison to the hemisphere reconstruction results and the actual object, the reconstruction results have been reconstructed out of the hemisphere, but for the reconstruction of the hemisphere there is a certain error. For example, the hemisphere is not very standard, and there is an error in the reconstructed hemisphere surface. First of all, from Figure

The design of this paper, from the beginning has been the use of the hemisphere for debugging and a series of operations; when the program is completed introducing a number of other objects, the compatibility of the program was tested. The first is to introduce a rectangular model (shown in Figure

Rectangular physical photograph.

The laser data taken in the program according to the experimental data taken in Figure

Laser height reconstruction.

Actual cuboid height.

Figures

According to the actual height of the object measurement results and reconstruction results to do a comparison, as shown in Table

Comparison of actual height and reconstruction height.

Hemisphere | rectangular | Half column | |
---|---|---|---|

Actual height | 3.4 | 1.8 | 2.4 |

| |||

Reconstruction height | 3.45 | 1.89 | 2.37 |

In this paper, we deeply study the using of word structure of light on the object surface reconstruction. Given an image for denoising, we can minimize the impact of other lights to the photographic picture by increasing the compatibility of the given photos. To get each of the height lines of the sum and interpolation operations, we then get a smooth three-dimensional reconstruction of the surface of the object. The latter part of the research process will focus on three-dimensional high-precision, high-speed, and real-time reconstruction for further study.

The datasets used in the experiment are from previously reported studies and datasets, which have been cited.

The authors declare that they have no conflicts of interest.

The study was supported by a Project of Shandong Province Higher Educational Science and Technology Program (no. J14LN64).