RETRACTED ARTICLE: Image processing algorithm of Hartmann method aberration automatic measurement system with tensor product model

Abstract

Nowadays, the society has entered the digital information age, and the information contained in the image is far more than the sum of the information contained in other media. In the Internet industry, image processing technology can be used to quickly find the required picture information. Other applications include disaster prevention, industrial automation production lines, semiconductor, electronics, tobacco, and food industries. After the meter glyph spot image is collected, there are several spots in the image, and the corresponding pixel values are stored in memory. In order to process images, they should be distinguished and marked so that the spot has definite eigenvalues. To this end, this paper proposes an image processing method. Firstly, an image denoising method combining self-snake model and P-M model is introduced. Secondly, the recursive HOSVD dimensionality reduction algorithm based on tensor product model is used to further process the image. The center of the Hartmann aperture image is solved by the centroid of all the spots, and the center overlap algorithm for determining the centroid distance of the aperture image by the symmetry of the centroid of the spot centroid can reduce the number of calculations. The experimental results show that this method can effectively identify and process the spot of the image and greatly reduce the time complexity and computational complexity of the algorithm.

1 Introduction

With the rapid development of information technology and digital technology, devices such as digital camera and smartphone are becoming more and more popular, which makes it more and more convenient for people to obtain digital information such as image, video, and audio. In these digital information, because the content image presented by the image is intuitionistic, easy to distinguish and identify visually, and easy to store and transmit, the use of image is very common. As a convenient means of information exchange, image has been applied in all aspects of human society and life, including work, study, and social.

Kumar et al. [1] developed a new open source software called cisTEM (a computational imaging system for transmission electron microscopy) to process high-resolution electron and low-temperature microscopes and single particle average data. cisTEM has a graphical user interface for submitting jobs, monitor their progress, and display results. The system implements a complete processing process, including movie processing, image defocusing determination, automatic particle pickup, 2D classification, generation of ab-initio 3D maps from random parameters, 3D classification, and high resolution thinning and reconstruction. Some of these steps implement newly developed algorithms; others are adapted from previously published algorithms. The software is optimized to process typical data sets (2000 microscopic photos, 200k–300k particles) on high-end workstations based on CPU in half a day or less, comparable to GPU-accelerated processing. You can also use flexible running profiles to schedule jobs on a large computer cluster, which can be used in most computing environments.

There are various aspects of health care. Image processing, medical image analysis, computer vision, pattern recognition, and machine learning contribute to the development of health care. Automatic understanding of human health and disease has a huge need for prevention, management, and treatment. This understanding, from low-level image processing to advanced analysis, is evolving. So, Zhang et al. [2] introduced a special problem to prove the progress of imaging, vision, and related issues in healthcare development.

Alfaroalmagro et al. [3] summarized the research progress of digital image processing technology in wood defect detection, wood structure, and wood esthetics and analyzed its shortcomings. The results show that the digital image processing technology can quickly and accurately identify insect holes, junctions, and decay defects. Image analysis of wood structure has some reference value for the study of climate change, wood growth, and mechanical properties (Table 1). The unique wood texture pattern can be extracted by digital image processing technology. Finally, the application prospect of digital image processing technology in wood science is expounded, which can create great commercial value in wood defect automatic detection, category identification, and esthetic research.

Table 1 Comparison of image processing results with different methods

Based on the application characteristics of digital image processing process, Grant et al. [4] introduced the engineering example in time according to the relevant chapter theory and made a deep analysis on it. At the same time, it excavates the engineering application of teaching content and forms the teaching mode of “engineering guidance-case introduction-class explanation-project design”. The image processing technology is introduced into the teaching. Through practice, the model can arouse the students’ interest in the course, effectively guide them to participate in the engineering project design, and improve the students’ practical application ability.

Image processing and recognition technology is an important product of the information age; its main function is to use computer to process a large amount of physical information can effectively save manpower. Image processing and recognition technology has been widely used in many fields in China and has made important contributions to the development of society.

Robertson et al. [5] mainly analyzes the characteristics and applications of image processing and recognition technology, and then briefly describes the development direction of image processing and recognition technology, which creates favorable conditions for promoting the development of image processing and recognition technology in China. Traditional virtual role reconstruction method can reconstruct role, but the efficiency of virtual role reconstruction is poor. Therefore, Brezis et al. [6] proposed an improved method of virtual role reconstruction based on 3D image processing. Key nodes are reconstructed using 3D images to capture and mark standard points for virtual role reconstruction. The edge operator of 3D virtual character image is determined, and the reconstructed contour area is divided to highlight the effect of reconstruction background. The rendering process of 3D virtual character image is optimized to reduce the virtual shadow effect of texture mapping on reconstructed image. In order to increase the texture ratio of the reconstructed image and realize the reconstruction of virtual characters, the contrast of image effect is carried out. The simulation results show that the improved virtual role reconstruction method has a good 3D reconstruction effect.

The rapid development of computer science, cloud computing, Internet of things, and mobile Internet have become the symbol of the times. The rapid development of these software technologies has challenged the reliability and hardware performance of self-verification. The performance requirements for hardware ultimately fall on the reliability of hardware integrated circuits. However, in the course of hardware development, verification of the correctness and reliability of integrated chips has been a bottleneck. The verification method based on simulation is widely used in the field of verification, which has irreparable shortcomings, that is, it can only prove that the system is wrong, but it can not prove the correctness of the system design. In software, the verification of reliability is still in the stage of no specific specification. Therefore, it is meaningful to verify the reliability of software or hardware.

In the past two decades, the semi-tensor product (STP) of matrices has attracted more and more attention in control theory and engineering. Niazian et al. [7] reviewed the application of the STP method in engineering. First, we review some preliminary results about the STP method. Secondly, some applications of STP in engineering are reviewed, including gene regulation, power system, wireless communication, smart grid, information security, internal combustion engine, and vehicle control. Finally, some potential applications of the STP method are predicted.

The tensor rank of a tensor t is the smallest number r such that t can be decomposed as a sum of r simple tensors. Let s be a k-tensor and let t be an l tensor. The tensor product of s and t is a (k + l) tensor. Tensor rank is sub-multiplicative under the tensor product. We revisit the connection between restrictions and degenerations. A result of their study is that tensor rank is not in general multiplicative under the tensor product. This answers a question of Draisma and Saptharishi. Specifically, if a tensor t has border rank strictly smaller than its rank, then the tensor rank of t is not multiplicative under taking a sufficiently hight tensor product power. The “tensor Kronecker product” from algebraic complexity theory is related to our tensor product but different, namely, it multiplies two k tensors to get a k tensor. Nonmultiplicativity of the tensor Kronecker product has been known since the work of Strassen. It remains an open question whether border rank and asymptotic rank are multiplicative under the tensor product. Interestingly, lower bounds on border rank obtained from generalized flattenings (including Young flattenings) multiply under the tensor.

Taha et al. [8] applied the model Petri net method based on matrix semi-tensor product to colored Petri nets. Firstly, the label evolution equation of colored Petri nets is established by using the semiconductor product of matrix. Then, we define the concept of controllability and the control label adjacency matrix of colored Petri nets. A sufficient and necessary condition for the reachability and controllability of colored Petri nets is given based on the label evolution equation and the control label adjacency matrix. An algorithm to verify the reachability of colored Petri nets is presented, and the computational complexity of the algorithm is analyzed. Finally, an example is given to illustrate the validity of the proposed theory. The significance of this study is to apply the model Petri net method based on matrix half product to colored Petri nets. This is a convenient way to verify whether one tag can be reached from another and to find all trigger sequences between any two reachable tags. In addition, this method lays a foundation for the analysis of other properties of colored Petri nets.

The granular cascade feedback shift register (FSR) is regarded as the semi-tensor product (STP) of the (BN), a matrix of two Boolean networks to convert the valley-like cascaded FSR into an equivalent linear equation. Based on STP, J Lu et al., a new method is proposed to study the nonsingularity of granular cascaded FSR. Firstly, the properties of the state transfer matrix of granular cascade FSR are studied. Then, we put forward their sufficient and necessary non-odd heterosexual conditions. Next, the valley-like cascaded FSR is regarded as a Boolean control network (BCN) and further provides sufficient conditions for its nonsingularity. Finally, two examples are provided to illustrate the results obtained by the method.

Precise angle measurement and transmission techniques have been widely used in precision measurement, aerospace, military, biomedicine, and other equipment based on polarized light and magneto-optic modulation. The method has the advantages of no rigid connection, long distance transmission, and high precision. However, the azimuth information measurement method needs to assist the complex servo tracking system according to the orthogonal extinction principle of the polarization prism, and the measurement time is longer, which reduces the reliability and the sensitivity of the system. In order to improve the measurement accuracy and rapid response of the system, a fast spatial angular measurement method is proposed by using the Wollaston prism polarization beam splitter, and the azimuth angle is calculated directly according to the two kinds of light intensity. By using magneto-optic modulation technology, the measuring time can be shortened and the accuracy can be improved. The fast spatial angle measurement system needs to realize the measurement function in a certain translation range, which requires the beam to have a certain coverage area in the receiving unit. However, the system is limited by the size and volume of the equipment; we can only choose to expand the incident beam. Therefore, when the beam is incident to the receiving unit, some incident angles and azimuths, that is, non-perpendicular incidence, will be generated. However, the polarization of the non-perpendicular incident light will change and there will be polarization aberration, which will lead to measurement error. Ramalakshmi and Kompala [9] proposed that the beam passes through the polarization prism in a certain range of azimuth and incidence angle and uses the polarized light tracking method and the boundary conditions of the electromagnetic field to study and simulate the polarization variation and distribution of the beam. The change of azimuth and angle can be simulated by the translation of the receiving unit, and the azimuth can be indirectly measured by using the self-collimating theodolite and the right-angle prism. The influence of polarization aberration on angle measurement system and the correctness of theoretical analysis are verified by comparing the measured azimuth angles under the conditions of translation and centering. It can be concluded that when the azimuth angle is 0°, the measurement error is smaller, and when the azimuth angle is 90°, the measurement error is the largest, and the measurement error will increase with the increase of the translation distance (that is, the incident angle). According to the comparison between the experimental data and the simulation results, the existing problems are pointed out, and the corresponding improvement measures are put forward. The results of this work have a certain significance for guiding the optimization of the system structure and the further improvement of the system performance.

2 Proposed method

2.1 Image denoising based on partial differential equation

The general expression of image processing for partial differential equations is

$$ \left\{\begin{array}{l}\frac{\partial u\left(t,x,y\right)}{\partial t}+F\left(x,y,u\left(t,x,y\right),{\nabla}_{\left(x,y\right)}u\left(t,x,y\right),{\nabla}_{\left(x,y\right)}u\left(t,x,y\right)\right)=0\kern1em t\in \left(0,T\right)\times \left(x,y\right)\in \Omega \\ {}u\left(0,x,y\right)={u}_0\left(0,x,y\right)\kern18em \left(x,y\right)\in \Omega \end{array}\right. $$

(1)

where Ω ⊂ R² is a plane bounded open region and is the domain of the image function; u₀(x, y)is the original image; F function depends on the image pixel position, the surrounding image itself, and the first-order and second-order directional derivatives of the image. The specific expression needs to be designed according to the specific application of image processing. For the application of the denoising method of partial differential equation image discussed in this paper, the designed F function needs to remove noise and preserve the image edge, texture, detail, and other functions. To achieve the desired processing effect, different denoising models according to the F design can be divided into linear diffusion, nonlinear diffusion, anisotropic diffusion, and the like [10].

In this paper, a de-noising method combining self-serpent model and P-M model is introduced. P-M model uses the function inversely proportional to the gradient as the diffusion coefficient and controls the size of the diffusion coefficient according to the gradient modulus value of different regions of the image. However, the image edge is blurred by diffusing the detail information. The self-snake model has the property of directional diffusion with edge stopping function and impulse filter which can better keep edge sharpness. It lays a good foundation for further image processing.

For the denoising model, it is ideal to keep the original edge information of the denoised image and eliminate the noise. Therefore, it is necessary to know clearly the controlling factors of diffusion in each direction during the diffusion process [11]. The diffusion term of the above mixed model is analyzed below.

$$ \frac{\partial u}{\partial t}{\displaystyle \begin{array}{l}=\alpha \mid \nabla u\mid \operatorname{div}\left[{g}_1\left(|\nabla u|\frac{\nabla u}{\mid \nabla u\mid}\right)\right]+\beta \operatorname{div}\left[{g}_2\left(|\nabla u|\right)\nabla u\right]\\ {}=\alpha {g}_1\left(|\nabla u|\right)\frac{\partial^2u}{\partial {\xi}^2}+{\alpha g}^{\prime}\left(|\nabla u|\right)\mid \nabla u\mid \frac{\partial^2u}{\partial {\eta}^2}\\ {}+\beta g{\prime}_2\left(|\nabla u|\right)\mid \nabla u\mid \frac{\partial^2u}{\partial {\eta}^2}+\beta {g}_2\left(|\nabla u|\right)\mid \nabla u\mid \left(\frac{\partial^2u}{\partial {\xi}^2}+\frac{\partial^2u}{\partial {\eta}^2}\right)\\ {}=\left[\alpha {g}_1\left(|\nabla u|\right)+\beta {g}_2\left(|\nabla u|\right)\right]\frac{\partial^2u}{\partial {\xi}^2}+\alpha g{\prime}_1\left(|\nabla u|\right)\mid \nabla u\mid \\ {}+\beta {g}_2\left(|\nabla u|\right)+g{\prime}_2\left(|\nabla u|\right)\mid \nabla u\mid \frac{\partial^2u}{\partial {\eta}^2}\end{array}} $$

(2)

where η is the unit vector of the gradient direction, ξ is the unit vector perpendicular to the gradient direction [12], and

$$ {u}_{\xi \xi}=\frac{u_{xx}{u}_x^2-2{u}_x{u}_y{u}_{xy}+{u}_{yy}{u}_y^2}{{\left|\nabla u\right|}^2} $$

(3)

The margin stop function and the control parameters are set to.

$$ {g}_1\left(|\nabla u|\right)=\exp \left[-{\left(\frac{\mid \nabla u\mid }{k}\right)}^2\right] $$

(4)

$$ {g}_2\left(|\nabla u|\right)=\frac{k^2}{k^2+{\left|\nabla u\right|}^2} $$

(5)

$$ \alpha =\frac{k^2}{k^2+{\left|\nabla u\right|}^2} $$

(6)

$$ \beta =\frac{{\left|\nabla u\right|}^2}{k^2+{\left|\nabla u\right|}^2} $$

(7)

where k is the gradient threshold, and its selection refers to the Canny operator to extract the high threshold of the edge and bring them into the image.

$$ \frac{\partial u}{\partial t}=H\left(|\nabla u|\right){u}_{\xi \xi}+G\left(|\nabla u|\right) u\eta \eta +\lambda \left(u-{u}_0\right) $$

(8)

The edge direction diffusion coefficient H(| ∇u| ) in Eq. (8) is

$$ H\left(|\nabla u|\right)=\frac{k^2}{k^2+{\left|\nabla u\right|}^2}\exp \left(-{\left(\frac{\mid \nabla u\mid }{k}\right)}^2\right)+{\left(\frac{k\mid \nabla u\mid }{k^2+{\left|\nabla u\right|}^2}\right)}^2 $$

(9)

Gradient directional diffusion coefficient G(| ∇u| ) as

$$ G\left(|\nabla u|\right)=\frac{2{\left|\nabla u\right|}^2}{k^2+{\left|\nabla u\right|}^2}\exp \left(-{\left(\frac{\mid \nabla u\mid }{k}\right)}^2\right)+{\left(\frac{k\mid \nabla u\mid }{k^2+{\left|\nabla u\right|}^2}\right)}^2-\frac{2{k}^2{\left|\nabla u\right|}^4}{{\left({k}^2+{\left|\nabla u\right|}^2\right)}^3} $$

(10)

According to Formula (10), the diffusion behavior of the whole diffusion process in different regions of the image is analyzed. Firstly, in the edge region of the image, that is, the region with larger gradient modulus ∣ ∇ u∣, the diffusion coefficient along the edge direction is as large as possible to ensure the elimination of the edge near the edge. The noise is such that the diffusion coefficient W satisfies a constant greater than zero, while the direction of the vertical edge desirably has a diffusion coefficient as small as possible. When it is negative, it contributes to the sharpening of the edge, and the diffusion coefficient G satisfies this requirement. Secondly, in the gradual area of the image, that is, the area where ∣ ∇ u∣ is smaller, it is desirable that the diffusion coefficient is larger along the edge direction, and the diffusion along the gradient direction is best to protect the texture details, that is, H(| ∇u| ) ≈ 1, G(| ∇u| ) <  < 1.

2.2 Tensor product model

Tensor cut apart is to segment tensor product along a certain order of tensor product. The following figure is a third-order tensor cut apart diagram, as shown in Fig. 1. Figure 1 is a schematic diagram of the division of a third-order tensor. The third-order tensor is divided into four blocks. When dividing the tensor, it is equally divided as much as possible, so that the size of each small tensor block is similar. Let T be an N-order tensor, 1 2.... Assuming that it is divided into n blocks along a certain order, the number of divided blocks can be expressed by the following formula, see Eqs. (11) and (12).

$$ {S}_{\mathrm{start}}=\left\{\begin{array}{l}\left\lfloor \frac{I_1}{n}\right\rfloor \ast \left(i- 1\right)+i\kern3em i\le {I}_1\%n\\ {}\left\lfloor \frac{I_1}{n}\right\rfloor \ast \left(i- 1\right)+{I}_1\%n\kern2em i>{I}_1\%n\end{array}\right. $$

(11)

$$ {S}_{\mathrm{end}}=\left\{\begin{array}{l}\left\lfloor \frac{I_1}{n}\right\rfloor \ast i+i\kern3em i\le {I}_1\%n\\ {}\left\lfloor \frac{I_1}{n}\right\rfloor \ast i+{I}_1\%n\kern1.36em i>{I}_1\%n\end{array}\right. $$

(12)

Fig. 1

Tensor product segmentation diagram

where 0 < i ≤ ⌊I₁/n⌋ is the ith dicing

S_start is the superscript of the ith dicing block

S_end is the subscript of the ith dicing block

After dividing the tensor with the map function, each tensor block of the segmentation is divided into workers. How to combine the last calculated result with the newly arrived data to reduce the calculation amount is a problem that needs to be solved currently [13]. Therefore, this paper proposes a recursive HOSVD dimensionality reduction algorithm.

When the data increases along a certain order of the tensor, take the third-order tensor as an example, as shown in Fig. 4a and b, where the blue cube is the original tensor and the red cube below the blue is the newly added tensor. In the tensor segmentation, it is analyzed how to divide the modular expansion matrix into the modular expansion matrix that constitutes the original tensor. Here, the new tensor expansion matrix is also added to the original tensor expansion matrix by approximation.

In the incremental HOSVD process, the original tensor and the new tensor are first expanded, the order of the two is extended to be consistent, and then the extended original tensor is HOSVD to obtain the left matrix and the core tensor (Fig. 2). The expanded new tensor is expanded according to the model, and the expanded matrix is subjected to iterative high-order singular value decomposition using the recursive matrix HOSVD algorithm. The updated tensor of the matrix and the original matrix using the iterative matrix HOSVD algorithm is used. Fusion is performed to obtain an approximate tensor that can replace the original tensor.

Fig. 2

Incremental HOSVD process

2.3 Hartmann method aberration automatic measuring system

Hartmann apertures are small aperture apertures arranged in meters. After passing through the Hartmann aperture, the parallel light emitted by the expanded collimation system is divided into a number of fine beams with different incident heights, which are directed towards the measured lens 6, and the resulting image is a speckle with a meter zigzag distribution. Each fine beam of light can be equivalent to a ray passing through the centroid of the spot. If there is an aberration in the measured lens, fine beams with different incident heights will intersect in different positions after passing through the measured lens [14]. Two cross sections are made near the focal point, and the meter-shaped spot on E₁ and E₂ is measured. The center distance of each corresponding point is bn₁ and bn₂. By pressing the formula, the position coordinates of the focal point Fn corresponding to the light at different incident heights of hn in the image space can be calculated as follows:

$$ Sn=\frac{bn_1}{bn_1+{bn}_2}d $$

(13)

where d is the distance between the two sections E₁ and E₂. The position coordinate of the focus F′₀ of the paraxial ray on the image space is S₀. The incident height hn is concentrically concentrated by the spherical aberration δ_L = S₀ − S_n of the beam, and the spherical aberration distribution of the optical system can be calculated.

Hartmann spherical aberration automatic detection system consists of image measurement, displacement control, and measurement. The area array CCD is used as the image sensor for image measurement.

3 Experiments

3.1 Image edge extraction based on weighted structure tensor product

The traditional structure tensor product is the average of the tensor product of the gradient in the local space. In the classical structure tensor product, each point in the neighborhood window has the same contribution to this average value, but in fact, it cannot get a better effect. Therefore, we can consider weighting each pixel in the neighborhood window, whose weight is related to the “similarity” of the gradient of the point relative to the gradient vector of the center point [15].

Given a remote sensing image, assuming that there are L bands, L two-dimensional images, then the formula can be used to represent its initial structural tensor, where N = L. However, the initial structural tensor J₀ of this form is meaning that the structural tensor at each pixel (x_i, y_i) contributes the same gradient information from the images of all L bands.

However, in remote sensing images, the information contained in different bands is not completely the same. Therefore, using the completely average method to calculate the structure tensor will amplify some information and reduce the effect of other information [16]. Taking a hyperspectral image of the University of Pavia as an example, the grayscale image of any one of the bands is shown in Fig. 3a. Take the two different bands and calculate the gradient vectors of the two channels, which are marked as red and green, respectively, as shown in Fig. 3b. It can be seen from the figure that the gradients of the two bands do not completely overlap, even there is a big difference, which means that the local structural information provided by the different channels to the structural tensor is not completely equal. Using the structural tensor to unify the uniform gradient, see Fig. 3c.

Fig. 3

Gradient display of different channel images. a Any band gray image. b Any two different band gradient detection edge. c Structural tensor product unified edge detection

Tensor product’s strict definition is described by linear mapping. Similar to the vector, tensor product is defined as a set of ordered numbers which satisfy a certain coordinate transformation relationship when some coordinate systems change. From a geometric point of view, it is a real geometric quantity, that is, it is something that does not change with the coordinate transformation of the frame of reference (in fact, the change of the basis vector). The result is that the combination of the base vector and the components on the corresponding basis vector (that is tensor product) remains invariant, for example, the first-order tensor product (vector) a can be expressed as a = x × i + y × j. Because the basis vector can have a rich combination, the tensor product table can show a very rich physical quantity [17].

Matrix theory is the only branch of mathematics originating in China. The modern matrix theory is suitable for dealing with linear or bilinear arrays, but due to the limitation of matrix multiplication on the dimension of factors, it is incompetent to deal with trilinear or even multilinear arrays. The theory of matrix semi-tensor product, which was put forward and developed by Chinese scholars in the last two decades, has broken through the restriction of dimension and become a powerful tool for dealing with multilinear arrays [18]. At present, this method has been applied in the research of logic system, finite game, fuzzy control, graph theory, and coding, as well as the engineering problems of biological system, power system, hybrid vehicle, and ship. The report introduces the establishment, development, and development of the subject. Look and discuss the enlightenment it gives.

The structure tensor product (structure tensor) is mainly used to distinguish the flat region, the edge region, and the corner area of the image (Fig. 4). The tensor product here is a structural matrix about the image [19]. The structure of the matrix is as follows: Rx, Ry is the horizontal and vertical gradient of the image, and then the determinant K and trace (trace) H of matrix T are obtained.

Fig. 4

Tensor product image processing effect diagram. a Original map. b Edge. c Relationship graph between determinant and trace in edge region

According to the relation between K and H, the flatness, edge, and corner region of the distinguishing image are obtained [20].

Flat area: H = 0;

Marginal region: H > 0 && K = 0;

Corner region: H > 0 && K > 0;

The practical application examples of this method are as follows [21]:

According to the characteristics of different channels providing unequal structural information, and the structural tensor eigenvalues represent the characteristics of local geometries [22], this paper proposes a structure sheet that uses the eigenvalues of different bands to weight the initial structure tensor of the corresponding band. Quantitatively [23], the structure tensor has been improved.

3.2 Implementation of HOG feature extraction algorithm

Compared with other feature description methods, HOG has many advantages [24]. Firstly, because HOG operates on the local lattice of the image, it can keep good invariance to the geometric and optical deformation of the image, and these two kinds of deformation will only appear in the larger spatial domain. Secondly, under the conditions of coarse airspace sampling, fine direction sampling, and strong local optical normalization, as long as the pedestrian is able to maintain an upright position in general, some minor adjustments can be allowed [25]. These subtle actions can be ignored without affecting the detection effect. Therefore, this paper uses HOG to extract image features. The HOG feature extraction method is to take a image (the target you want to detect or scan the window):

• 1. Grayscale (think of the image as a 3D image of XY)

• 2. The gamma correction method is used to standardize the color space of the input image in order to adjust the contrast of the image, reduce the influence caused by the local shadow and illumination change of the image [26], and at the same time, suppress the noise interference

• 3. Calculate the gradient (including size and direction) of each pixel in the image, primarily to capture contour information while further attenuating the interference of light

• 4. Divide the image into small cells (for example, 6 × 6 pixels/cell)

• 5. The descriptor of each cell can be formed by counting the gradient histogram of each cell (the number of different gradients)

• 6. Each cell is composed of a block (for example, 3 × 3 cell/block), and all cell feature descriptor in a block is concatenated to obtain the HOG feature descriptor. of the block

• 7. The HOG feature descriptor of the image can be obtained by concatenating all the HOG features descriptor of the block in the image [27]. This is the final feature vector available for classification

4 Results and discussion

4.1 Accuracy comparison

In order to more intuitively compare the accuracy of the BRISK algorithm and the feature point matching of the algorithm in the case of changes in scale, angle of view, rotation, and illumination, the correct matching rate is used to evaluate the performance of the algorithm, and the correct matching rate [28]is defined as:

$$ p=\frac{N_c}{N}\times 100\% $$

Among them, C_N and N represent the correct matching point logarithm and all matching point logarithm after the RANSAC algorithm. In this paper, the image size, accuracy, time-consuming, and other experimental results are compared, and the results are as follows.

4.2 Time complexity comparison

In the experiment, the Hartmann pupil consists of n spots, where n = 8n − 1 (n is the logarithm of the spot symmetry about the center of gravity of the Hartmann pupil on the diagonal, and 4n is the amount of the center distance to be sought [19] The general method requires n × (n − 1)/2 complex calculations to complete the solution. The central overlap algorithm for spot distance measurement in Hartmann pupil images is only (n − 1)/2 times. Compared with the previous related methods, the method in this paper is simple to calculate, which greatly reduces the time complexity and computational complexity of the algorithm. Image classification has become an important research content in the field of image processing. Traditional vector-based classification algorithms require vectorization of images. In order to distinguish between scalars, vectors, matrices, and high-dimensional tensors, scalars, one-dimensional vectors, two-dimensional matrices, and three-dimensional tensors (three-dimensional matrices) are distinguished in different forms. The white body represents a scalar, such as a; the lowercase black body represents a one-dimensional vector, such as a; the uppercase black body represents a two-dimensional matrix, such as A; and the flower body represents a three-dimensional tensor, such as A. The expansion model of high dimensional tensors is an important step in HOSVD. A matrix expansion of a tensor is also a matrix representation of tensors, and all column (or row) vectors are stacked one after the other. For the three-dimensional tensor, the top-down is the expansion of mode 1, the mode 2, and mode 3, respectively. The process of vectorization leads to the loss of image space information and the generation of high dimensional vector data. In order to solve the problem caused by vectorization, tensor as a natural expression of images has become a research hotspot of image classification.

4.3 Comparison of extraction effect of feature points

By referring to the method of edge detection and avoiding the influence of threshold factors, the algorithm extracts the feature points of the image based on the edge image, which can reduce the candidate points of interference to some extent and improve the quality of the feature points. In the matching stage, the two-way Hamming distance matching method and the RANSAC algorithm are used to eliminate the mismatched point pairs and the matching effect is obviously improved. By constructing classification experiments on two second-order grayscale datasets and two third-order motionmap datasets, it is verified that the proposed method is not only better than the vector-based classification algorithm in image classification accuracy, but also better than the currently popular tensor classification algorithm. Experimental results show that the proposed algorithm solves the BRISK algorithm with many mismatched pairs and the matching effect is not ideal [29]. The problem, compared with the BRISK algorithm, is that the proposed algorithm is slightly more robust, which can explain the feasibility of the improved method proposed in this paper.

5 Conclusions

This paper proposes an image processing algorithm for the automatic measurement system of Hartmann’s aberration considering the tensor product model. The algorithm applies an image denoising method based on PM model and self-snake model. This model overcomes the shortcomings of the PM model in removing image edge information and poor ability to remove salt and pepper noise while removing Gaussian noise and makes up for the self-snake model’s insufficiency. The experimental comparison results show that the method can effectively remove the noise and maintain the shape of the image and improve the visual effect of the image. The effectiveness of the method is further verified by the rice-shaped spot image processing experiment.