CN102779342A - Edge detection method for voice coil motor magnet - Google Patents

Abstract

The invention provides a voice coil motor (Voice Coil Motor for short VCM) magnet edge detection method based on mathematical morphology and a canny operator, which belongs to the field of computer image recognition. The basic steps are (1) input the VCM image for background removal and binarization processing to obtain the binary image of the magnet; (2) first corrode and then dilate the binary image; and then perform dilation and then corrode; ( 3) adopt Gaussian filter to carry out smooth processing to the image that step (2) obtains; (4) carry out gradient calculation, obtain the gradient value of each pixel point; (5) carry out non-maximum value to each pixel point and gradient value Suppress to obtain preliminary edge points; (6) Perform double-threshold calculation on the preliminary edge points obtained in step (5) to obtain a complete edge. The edge of the VCM magnet can be detected stably and efficiently by adopting the method of the invention.

Description

A method for detecting the edge of a voice coil motor magnet

technical field

The invention relates to a method for detecting the edge of a voice coil motor magnet based on mathematical morphology and a canny operator, which belongs to the field of computer image recognition and is suitable for edge extraction of a voice coil motor magnet.

Background technique

Voice Coil Motor (VCM for short) is an indispensable part of the hard disk. The magnet on it will form a magnetic field, which is used to drive the read-write arm in the hard disk. Therefore, the edge information of the VCM magnet is important to ensure the quality of the hard disk. one of the factors. However, in actual detection, because the VCM shape is relatively complex, false edges often appear when collecting magnet edge information, resulting in inaccurate magnet edge positioning.

Mathematical morphology analyzes images based on geometry, and applies structural elements to the input image to obtain an output image of the same size as the input image. The basic idea is to use structural elements with a certain shape to detect and extract image features to To achieve the purpose of image analysis and recognition. Dilation, erosion, opening and closing are basic operations in mathematical morphology.

Canny operator is a multi-stage optimization operator with filtering, enhancement and detection. Canny gives three indicators for evaluating edge detection performance:

1) High signal-to-noise ratio criterion, that is, the probability of non-edge points being misjudged as edge points or edge points being misjudged as non-edge points is low, so that the output signal-to-noise ratio reaches the maximum;

2) High positioning accuracy criterion, that is, the detected image edge point should be as close as possible to the center of the actual image edge;

3) Single edge response criterion, that is, to ensure that only one pixel corresponds to a single edge, and to suppress the response of false edges to the greatest extent.

Contents of the invention

In view of the above problems, the object of the present invention is to provide a VCM magnet edge detection method based on mathematical morphology and canny operator, which can detect the edge of the VCM magnet stably and efficiently in real time.

The VCM magnet edge detection method based on mathematical morphology and canny operator comprises the following steps:

Step 1), input the TIFF image of VCM to remove the background and binarize to obtain the binary image of the magnet;

Step 2), using a disc-shaped structural element with a radius of 15 to perform a mathematical morphological operation of first corroding and then expanding on the binary image, that is, opening the operation; and then using a diamond-shaped structural element with a radius of 8 to perform the operation of first expanding and then corroding , that is, the closing operation;

Step 3), using a Gaussian filter to smooth the image obtained in step 2), and filter the image noise;

Step 4), using the canny operator to calculate the gradient, to obtain the gradient value of each pixel in the image;

Step 5), using the gradient value of each pixel in the image obtained in step 4), carrying out non-maximum suppression to each pixel and gradient value, to obtain preliminary image edge points;

Step 6), performing double threshold calculation on the preliminary edge points obtained in step 5), further refining the edge points, eliminating false edge points and filling in edge gaps to obtain a complete edge.

The present invention adopts the above-mentioned technical scheme, uses the mathematical morphology algorithm to preprocess the VCM image and extracts the image features, which can effectively remove the interference and retain the detailed information of the image, and use the canny operator to perform edge detection on the processed image to obtain a clear image. VCM magnet shape edge.

Description of drawings

Fig. 1 is a flow chart of the VCM magnet edge detection method based on mathematical morphology and canny operator.

Figure 2 is the original image of the collected VCM.

Figure 3 is a schematic diagram of the results after mathematical morphology preprocessing.

Fig. 4 is a schematic diagram of the detection result of the edge of the magnet.

Detailed ways

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

1) Input the VCM picture to be detected, perform background removal processing, extract the magnet part of interest, and perform binarization processing to obtain the binary image X of the magnet.

2) Structural elements S ₁ and S ₂ are selected, wherein S ₁ is a disc-shaped structure with a radius of 15, and S ₂ is a diamond-shaped structure with a radius of 8. Use S ₁ to perform a mathematical morphology operation on X that first erodes and then expands, that is, the opening operation Get X ₁ , and then use S ₂ to perform the mathematical morphology operation of first expansion and then corrosion, that is, the closing operation $x_1\&Center\; Dot;S_2=(x_1\⊕S_2)\mathrm{\Θ}{S}_2,$ Get X ₂ .

与X₂进行卷积运算得到

和

计算得到图像中每个像素点的梯度值 $A(i,j)=\sqrt{E_x^2(i,j)+E_y^2(i,j)}.$ 3) Using a two-dimensional Gaussian function $G(x,\mathrm{the\; y})=\frac{1}{{2\mathrm{\π\σ}}^2}{e}^{\left(\frac{-(x^2+{\mathrm{the\; y}}^2)}{{2\mathrm{\σ}}^2}\right)}$ Find the first derivative $\frac{\∂G}{\∂x}=\frac{-x}{{2\mathrm{\π\σ}}^4}{e}^{(-\frac{x^2+{\mathrm{the\; y}}^2}{{2\mathrm{\σ}}^2})},$

Convolved with X ₂ to get

and

Calculate the gradient value of each pixel in the image $A(i,j)=\sqrt{{\mathrm{E.}}_x^2(i,j)+{\mathrm{E.}}_{\mathrm{the\; y}}^2(i,j)}.$

4) Perform non-maximum suppression on each pixel point and gradient value, that is, refine the roof band of the gradient magnitude image, and only keep the point with the largest local variation in magnitude. If the edge strength A( i, j) is not less than the gradient magnitude of two adjacent pixel points in the gradient direction, then this point is judged as a possible edge point.

5) Set two thresholds τ ₁ and τ ₂ , double-threshold the non-maximum suppressed image, and get two detection results, which are the image T ₁ segmented by the low threshold τ 1 and the image T ₁ segmented by the high threshold τ ₂ Segment the resulting image T ₂ . Based on the image T ₂ to connect the edge contours, when connecting to the endpoint, use the image T ₁ as a supplement to perform edge connection to obtain the final edge detection effect map.

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention in any form. All simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention belong to the technical solution of the invention. within range.

Claims (2)

1. A voice coil motor magnet edge detection method is characterized in that: first adopt mathematical morphology to process the voice coil motor magnet image, and then use the canny operator to detect the clear magnet edge shape. 2. The method for detecting the edge of a voice coil motor magnet according to claim 1, characterized in that: the mathematical morphology used to process the image is to use a disc-shaped structural element with a radius of 15 for the binary image to corrode first and then The mathematical morphology operation of expansion is the opening operation; and then the diamond-shaped structural element with a radius of 8 is used to perform the first expansion and then corrosion operation, that is, the closing operation.

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