WO2017193596A1

WO2017193596A1 - Image matching method and system for printed circuit board

Info

Publication number: WO2017193596A1
Application number: PCT/CN2016/113120
Authority: WO
Inventors: 杨铭
Original assignee: 广州视源电子科技股份有限公司
Priority date: 2016-05-13
Filing date: 2016-12-29
Publication date: 2017-11-16
Also published as: CN106023182A

Abstract

An image matching method and system for a printed circuit board. The method comprises the following steps: obtaining a template image and a test image of a target printed circuit board (S101); separately extracting feature points of the template image and the test image to obtain a first feature point set of the template image and a second feature point set of the test image (S102); calculating the similarity values between first feature points of the first feature point set and second feature points of the second feature point set, and pairing the first feature points and the second feature points according to the similarity values to obtain feature point pairs (S103); and calculating, according to the feature point pairs, a conversion matrix from the template image of the target printed circuit board to the test image thereof, and using the conversion matrix to search for an image of the printed circuit board matching the template image in the test image (S104). According to the method, an image of a printed circuit board can be quickly matched, and the accuracy of the image matching method and system for a printed circuit board is improved.

Description

Printed circuit board image matching method and system

Technical field

The present invention relates to the field of optical detection technology, and in particular, to a printed circuit board image matching method and system.

Background technique

In the Automatic Optic Inspection (AOI), it is often necessary to perform image matching on the printed circuit board so that the subsequent steps of the detection of the printed circuit board can operate normally.

For printed circuit board image matching, there are two main technical solutions: first, based on template matching; second, based on SIFT (Scale-invariant feature transform) / SURF (Speeded Up Robust Features) , acceleration robustness) operator matching method.

The method based on template matching is to match the corresponding image block and template image by sliding the image window on the input image. The common measurement method is NCC (Normalized Cross Correlation method). However, this method can only match non-rotating boards, and image matching is not possible for boards that may have varying degrees of rotational variation in an online automated optical inspection environment.

The matching method based on SIFT/SURF operator is to eliminate noise by multi-scale decomposition based on linear Gaussian pyramid, and extract significant feature points, and then match the input image with the feature points of the template to complete the image matching. However, this kind of method requires a lot of computation time and computational resources in the matching process, which not only slows the calculation, but also limits the usage scenario of the AOI, and also increases the computational hardware cost; in addition, the feature detection algorithm such as SIFT/SURF is based on linearity. The Gaussian pyramid performs multi-scale decomposition. This decomposition method sacrifices local precision, which is easy to cause boundary blur and detail loss, which leads to matching errors and other results.

In summary, the conventional printed circuit board image matching method has a slow calculation speed, a high hardware cost, and a low accuracy.

Summary of the invention

Based on this, it is necessary to solve the technical problems of slow speed, high hardware cost and low accuracy for the traditional printed circuit board image matching method, and provide a printed circuit board image matching method and system.

A printed circuit board image matching method includes the following steps:

Obtaining a template image and a test chart of the target printed circuit board; wherein the template image is an angle-corrected image of the target printed circuit board, the test chart is an angle of the target printed circuit board Corrected image;

Performing feature point extraction on the template graph and the test graph respectively, and acquiring a first feature point set of the template graph and a second feature point set of the test graph;

Calculating a similarity value between the first feature point of the first feature point set and the second feature point of the second feature point set, and pairing the first feature point and the second feature point according to the similarity value, Obtaining feature point pairs;

Calculating a conversion matrix of the template of the target printed circuit board to the test pattern according to the feature point pair, and using the conversion matrix to find a printed circuit board image in the test chart that matches the template image.

The above-mentioned printed circuit board image matching method performs feature point extraction on the template image and the test pattern of the obtained target printed circuit board, respectively, to obtain a first feature point set of the template image and a second feature point set of the test pattern. Recalculating a similarity value between the first feature point of the first feature point set and the second feature point of the second feature point set, and performing the first feature point and the second feature point according to the similarity value Pairing, obtaining a pair of feature points; calculating a conversion matrix of the template pattern of the target printed circuit board to the test pattern according to the feature point pair, and using the conversion matrix to find a printed circuit matching the template image in the test pattern Board image. Through the above technical solution, the printed circuit board image matching method of the invention realizes the fast matching of the printed circuit board image, and effectively improves the accuracy of the printed circuit board image matching method.

A printed circuit board image matching system comprising:

An acquisition module, configured to obtain a template image and a test chart of the target printed circuit board; wherein the template image is an angle corrected image of the target printed circuit board, and the test chart is the target printed circuit An unangled image of the board;

An extraction module, configured to perform feature point extraction on the template image and the test image respectively, and acquire a first feature point set of the template image and a second feature point set of the test image;

a pairing module, configured to calculate a similarity value between the first feature point of the first feature point set and the second feature point of the second feature point set, and the first feature point and the second feature point according to the similarity value Feature points are paired to obtain feature point pairs;

a matching module, configured to calculate a conversion matrix of the template map of the target printed circuit board to the test pattern according to the feature point pair, and use the conversion matrix to search for a printed circuit board image in the test chart that matches the template image .

In the above-mentioned printed circuit board image matching system, feature extraction is performed on the template image and the test pattern of the target printed circuit board acquired by the acquisition module by the extraction module, and the first feature point set and the test chart of the template image are obtained. a second feature point set; and calculating, by the pairing module, the first feature point of the first feature point set and the second feature point of the second feature point set a similarity value between the first feature point and the second feature point according to the similarity value to obtain a feature point pair; finally, the matching module is used to calculate the target printed circuit according to the feature point pair The template map of the board to the conversion matrix of the test pattern, and the conversion matrix is used to find the printed circuit board image in the test chart that matches the template image. Through the above technical solution, the printed circuit board image matching system of the invention realizes fast matching of the image of the target printed circuit board, and effectively improves the accuracy of the image matching system of the printed circuit board.

DRAWINGS

1 is a flow chart of a method for matching printed circuit board images according to an embodiment of the present invention;

2 is a flow chart of a method for matching printed circuit board images according to another embodiment of the present invention;

3 is a schematic structural diagram of a printed circuit board image matching system according to an embodiment of the present invention;

4 is a schematic structural view of a printed circuit board image matching system according to another embodiment of the present invention.

detailed description

The technical solutions of the present invention will be clearly and completely described in the following with reference to the accompanying drawings and preferred embodiments.

As shown in FIG. 1, FIG. 1 is a flowchart of a method for matching a printed circuit board image according to an embodiment of the present invention, including the following steps:

Step S101: Acquire a template image and a test chart of the target printed circuit board; wherein the template image is an angle-corrected image of the target printed circuit board, and the test chart is the target printed circuit board An image without angle correction;

In this step, the template points and test patterns of the target printed circuit board are obtained to prepare for feature point extraction in the subsequent steps.

In a specific implementation, the template image described in this step may only include an angle corrected target printed circuit board image, and the test image may include one or more target printed circuit board images, and each The image of the board is not angle corrected and may be scattered anywhere in the image; in addition, the target printed circuit board may not be included in the test chart.

In one embodiment, the printed circuit board image matching method of the present invention, the step 101 of acquiring a template image and a test pattern of the target printed circuit board may include:

Obtaining a template image and a test chart of the plurality of target printed circuit boards; wherein the template image is an angle-corrected image of the plurality of target printed circuit boards, and the test chart is printed for the plurality of targets An image without a corner correction of the board.

In a specific implementation, if the target printed circuit board is not included in the test chart, the printed circuit board image matching method of the present invention does not output any image; if the test image includes N target printed circuit boards, the present invention The printed circuit board image matching method outputs the successfully printed printed circuit board image in N times.

Step S102: performing feature point extraction on the template image and the test image respectively, and acquiring a first feature point set of the template image and a second feature point set of the test image;

In this step, the feature point detection and extraction are performed on the obtained target printed circuit board template map and the test image respectively, and the first feature point set of the template image and the second feature point set of the test image are obtained, which is convenient for subsequent The step of pairing the above feature points. In a specific implementation, the number of feature points of the first feature point set is not necessarily equal to the number of feature points of the second feature point set. For example, after the feature point detection and extraction of the template image, the first feature point set is obtained. The number of feature points is 1000. After the feature points are detected and extracted, the number of feature points of the second feature point set may be 1500. When pairing the feature points in the subsequent steps, the main purpose is The 1000 feature points of the first feature point set and the 1500 feature points of the second feature point set are searched and paired.

Step S103: calculating a similarity value between the first feature point of the first feature point set and the second feature point of the second feature point set, and the first feature point and the second feature point according to the similarity value Pairing to obtain feature point pairs;

In this step, the first feature point set and the second feature point set are extracted and matched by the first feature point set extracted in step S102, that is, by calculating the first feature point and the second feature of the first feature point set. And a similarity value between the second feature points of the point set, according to the similarity value, finding feature points corresponding to the one-to-one correspondence between the template image and the test image, and composing the first feature point set and the second feature point set Feature point pairs.

Step S104: Calculate a conversion matrix of the template of the target printed circuit board to the test pattern according to the feature point pair, and use the conversion matrix to search for a printed circuit board image in the test chart that matches the template image.

After retrieving the pairing to obtain a plurality of sets of feature point pairs in step S103, calculating a conversion matrix of the template map of the target printed circuit board to the test pattern according to the first feature point and the second feature point of the feature point pair, and The conversion matrix is used to find an image of the target printed circuit board in the test chart that matches the template image.

The above-mentioned printed circuit board image matching method performs feature point extraction on the template image and the test pattern of the obtained target printed circuit board, respectively, to obtain a first feature point set of the template image and a second feature point set of the test pattern. ; calculate the first a similarity value between the first feature point of the feature point set and the second feature point of the second feature point set, and the first feature point and the second feature point are paired according to the similarity value to obtain a feature point And calculating a conversion matrix of the template of the target printed circuit board to the test pattern according to the feature point pair, and using the conversion matrix to search for a printed circuit board image in the test chart that matches the template image. Through the above technical solution, the printed circuit board image matching method of the invention realizes the fast matching of the printed circuit board image, and effectively improves the accuracy of the printed circuit board image matching method.

In a specific implementation, if the test chart includes a plurality of target printed circuit board images, the calculation of the template of the target printed circuit board to the conversion matrix of the test image according to the feature point pair, and using the conversion The step S104 of the matrix finding the printed circuit board image matching the template image in the test chart includes:

Calculating a conversion matrix of the template image of one of the target printed circuit boards to the test pattern according to the feature point pair, and using the conversion matrix to find the one of the target printed circuit board images in the test chart that matches the template image .

After the step of using the conversion matrix to find the one of the target printed circuit board images in the test chart that matches the template image, the method further includes:

Step S105: Shielding the feature point pairs to match other printed circuit board images in the plurality of target printed circuit board images.

In the above embodiment, the test chart contains images of a plurality of printed circuit boards. After the image matching of one printed circuit board is completed, in order to avoid matching the images of other printed circuit boards, it is necessary to clear the previous pairs. Feature points involved in matching the target printed circuit board image. For example, the conversion matrix calculated by the previous round of matching can find the printed circuit board image area corresponding to the printed circuit board image in the template image in the test chart, that is, by the template image The printed circuit board image, the printed circuit board image area in the test chart obtained through the conversion matrix mapping, masks the feature points in the area, and only considers the remaining feature points when performing other printed circuit board image matching. It can not only avoid the influence of the previous round, but also improve the efficiency of matching other printed circuit board images. The technical solution of the embodiment achieves fast matching of multiple printed circuit board images and improves the working efficiency of the printed circuit board image matching method.

In one embodiment, in the printed circuit board image matching method of the present invention, the step of performing feature point extraction on the template image and the test image respectively includes:

The nonlinear scale space of a single Octave layer is constructed by using a KAZE operator, and the feature points are extracted from the template map and the test map by using the nonlinear scale space.

In practical application, the printed circuit board image matching method of this embodiment uses a KAZE operator to pass nonlinear expansion. The spatial filtering is used to construct a stable nonlinear scale space of a single Octave layer, and the feature points are extracted from the template graph and the test graph by using the nonlinear scale space, and the calculation is greatly improved under the premise that the precision is relatively unchanged. Efficiency; moreover, the KAZE operator is used to construct the nonlinear scale space of a single Octave layer, and the feature points of the rotated circuit board image can be extracted, which facilitates image matching in subsequent steps and reduces the printed circuit board. The hardware cost of the image matching method.

The nonlinear diffusion filtering method described in this embodiment considers the variation of the image brightness L of the target printed circuit board and the image brightness of the test pattern on different scales as the divergence of some form of the flow function:

Where L represents the image brightness of the template or test pattern of the target printed circuit board, t represents the scale parameter, and c(x, y, t) represents the conduction function.

In the specific implementation, in order to limit the area with a large width, the conduction function c(x, y, t) shown in the following equation can be selected:

Where c(x, y, t) represents the conduction function and t represents the scale parameter,

A gradient representing the Gaussian smoothed image L _σ and k representing a constant controlling the degree of diffusion.

In the specific implementation, the extracted feature points are represented by feature vectors, and are prepared for pairing the feature points in the subsequent steps.

In one embodiment, the printed circuit board image matching method of the present invention calculates the similarity value between the first feature point of the first feature point set and the second feature point of the second feature point set. The steps can include:

Indexing and retrieving the first feature point of the first feature point set and the second feature point of the second feature point set by using a multi-probe index function, and calculating a metric distance between the first feature point and the second feature point;

And determining a similarity value between the first feature point and the second feature point according to the metric distance.

In this embodiment, since the obtained first feature point set and the second feature point set have a large number of feature points, the feature points in the first feature point set and the second feature point set may be obtained by using, for example, a KAZE operator. The high-dimensional vector of the 64-dimensional feature is represented; and the first feature point of the first feature point set and the second feature point of the second feature point set are indexed and retrieved by using the multi-probe LSH index function, and finally the feature point pair is obtained. . Through the above technical solutions, effectively improved Retrieving pairing efficiency and pairing accuracy further improves the efficiency of the printed circuit board image matching method.

As shown in FIG. 2, FIG. 2 is a flowchart of a method for matching a printed circuit board image according to another embodiment of the present invention, and the step of obtaining feature point pairs of the first feature point set and the second feature point set is performed. After that, you can also include:

Step S106: Calculate a best matching distance and a second best matching distance between the first feature point and the second feature point in the feature point pair;

Step S107: Determine the reliability of the feature point pair by comparing the difference between the best matching distance and the sub-optimal matching distance and the preset threshold value, and filter the feature point pair according to the reliability.

In the above embodiment, in order to further improve the accuracy of the printed circuit board image matching method of the present invention, the feature points of the first feature point set and the second feature point set are searched and paired by using the multi-probe LSH index to obtain features. After the point is paired, certain measures can be taken to re-evaluate the reliability of the obtained feature point pairs. In the implementation, determining the feature point pair by comparing the difference between the best matching distance of the first feature point and the second feature point in the feature point pair and the sub-optimal matching distance and the preset threshold value Reliability, filtering the feature point pairs according to reliability, effectively improving the accuracy of the printed circuit board image matching method, and further improving the efficiency of the printed circuit board image matching method of the present invention.

In one embodiment, the printed circuit board image matching method of the present invention determines the feature point pair by comparing the difference between the best matching distance and the sub-optimal matching distance and the preset threshold value. The step S107 of filtering the feature point pairs according to the reliability may include:

If the difference between the best matching distance and the sub-optimal matching distance is greater than a preset threshold, determining that the feature point pair is reliable; otherwise, determining that the feature point pair is unreliable, and filtering the feature point pair.

In the above embodiment, the feature point pair whose difference between the best matching distance and the second best matching distance is greater than the preset threshold is retained, and the difference between the best matching distance and the second best matching distance is not greater than the preset threshold. The culling is performed to improve the accuracy of the printed circuit board image matching method of the present invention, and further improves the working efficiency of the printed circuit board image matching method of the present invention.

In one embodiment, the printed circuit board image matching method of the present invention may further include: after the step of using the conversion matrix to search for an image of the printed circuit board that matches the template image in the test image, the method further includes:

Step S108: Correcting the printed circuit board image in the test chart according to the target printed circuit board image in the template image.

In practical applications, the printed circuit board image in the test chart can be printed according to the target printed circuit board image in the template image. Image correction methods such as geometric correction, angle correction, etc., including but not limited to.

In one embodiment, the printed circuit board image matching method of the present invention, the calculating the conversion matrix of the first feature point to the second feature point of the plurality of sets of feature point pairs comprises:

Calculating a transformation matrix of the first feature point to the second feature point of the plurality of sets of feature point pairs by using a random sample set algorithm;

After the step of calculating the conversion matrix of the first feature point to the second feature point of the plurality of sets of feature point pairs by using the random sample set algorithm, the method may further include:

Selecting a set of feature points with the smallest error pair as the conversion matrix of the template map to the test chart; wherein the conversion matrix represents the target printed circuit board image in the template image to the template image The mapping relationship of the printed circuit board images in the test chart corresponding to the target printed circuit board image.

In this embodiment, a random sample set algorithm may be used to calculate a conversion matrix of a first feature point to a second feature point of a plurality of sets of feature point pairs, in order to accurately describe a template map of the target printed circuit board to a test map. Relationship, the set of feature points with the smallest selection error is the calculated conversion matrix as the template of the target printed circuit board to the conversion matrix of the test chart.

In practical applications, the first feature point and the second feature point may be represented in the form of coordinates or vectors, which is also advantageous for calculating the first feature point to the second feature point according to the first feature point and the second feature point. Conversion matrix.

In a specific implementation, if there is no image of the target printed circuit board in the test chart, and there is only one image of the target printed circuit board in the template image, it is also possible to calculate such a conversion matrix, thereby forming an incorrect pairing. Therefore, in order to further improve the accuracy of the printed circuit board image matching method of the present invention, the shape of the target printed circuit board in the test chart can be filtered a priori.

In one embodiment, the printed circuit board image matching method of the present invention may further include: after the step of using the conversion matrix to search for a target printed circuit board image that matches the template image in the test pattern,

Step S109: filtering the target printed circuit board image in the test chart that is inconsistent with the morphological feature of the target printed circuit board image in the template image by comparing the morphological features of the target printed circuit board image in the test chart and the template image. .

Since the image area of the printed circuit board is generally a convex polygon, it can be assumed that the image area of the target printed circuit board in the template image is also a convex polygon after being mapped; and, after being mapped in the test chart The area of the image area of the target printed circuit board should also be approximately equivalent to the image area of the target printed circuit board in the template image. Therefore, in practical applications, the printed circuit board image matching method of the present invention can determine whether the image area of the mapped target printed circuit board in the test chart is still a convex polygon and its area and the template image aims The image area of the printed circuit board is roughly equivalent to determine whether the match is successful. If the matching is successful, the geometrically corrected printed circuit board image that is matched this time is output, otherwise the matching process is ended.

As shown in FIG. 3, FIG. 3 is a schematic structural diagram of a printed circuit board image matching system according to an embodiment of the present invention, including:

An obtaining module 101, configured to acquire a template image and a test chart of the target printed circuit board; wherein the template image is an angle-corrected image of the target printed circuit board, and the test chart is the target printing An unangled image of the board;

In a specific implementation, the template image described in the obtaining module 101 may include only one angle corrected target printed circuit board image, and the test image may include one or more target printed circuit board images, and Each board image is not angularly corrected and may be scattered anywhere in the image; in addition, the target printed circuit board may not be included in the test chart.

In one embodiment, the printed circuit board image matching system of the present invention, the acquisition module 101 can also be used to:

In a specific implementation, if the target printed circuit board is not included in the test chart, the printed circuit board image matching system of the present invention does not output any image; if the test chart includes N target printed circuit boards, the present invention The printed circuit board image matching system outputs the successfully matched board image in N outputs.

The extracting module 102 is configured to perform feature point extraction on the template graph and the test graph, respectively, and obtain a first feature point set of the template graph and a second feature point set of the test graph;

In the above extraction module 102, the feature point detection and extraction are performed on the acquired target printed circuit board template image and the test image respectively, and the first feature point set of the template image and the second feature point set of the test image are obtained. The above feature points are paired for the subsequent steps. In a specific implementation, the number of feature points of the first feature point set is not necessarily equal to the number of feature points of the second feature point set. For example, after the feature point detection and extraction of the template image, the first feature point set is obtained. The number of feature points is 1000. After the feature points are detected and extracted, the number of feature points of the second feature point set may be 1500. When pairing the feature points in the subsequent steps, the main purpose is The 1000 feature points of the first feature point set and the 1500 feature points of the second feature point set are searched and paired.

The pairing module 103 is configured to calculate a similarity value between the first feature point of the first feature point set and the second feature point of the second feature point set, and the first feature point and the first feature point according to the similarity value Two feature points are paired to obtain feature point pairs;

In the pairing module 103, the first feature point set extracted by the extraction module 102 and the feature points in the second feature point set are search-matched, that is, by calculating the first feature point of the first feature point set and And a similarity value between the second feature points of the second feature point set, according to the similarity value, finding a feature point corresponding to the template map and the test image, and forming the first feature point set and the second feature A feature point pair of a point set.

The matching module 104 is configured to calculate a conversion matrix of the template map of the target printed circuit board to the test pattern according to the feature point pair, and use the conversion matrix to search for a printed circuit board that matches the template image in the test pattern. image.

In the above-mentioned printed circuit board image matching system, feature extraction is performed on the template image and the test pattern of the target printed circuit board acquired by the acquisition module 101 by the extraction module 102, and the first feature point set and test of the template image are obtained. a second set of feature points of the graph; and calculating, by the pairing module 103, a similarity value between the first feature point of the first feature point set and the second feature point of the second feature point set, according to the similarity value pair The first feature point and the second feature point are paired to obtain a feature point pair. Finally, the matching module 104 calculates a conversion matrix of the target printed circuit board template to the test pattern according to the feature point pair, and utilizes The conversion matrix looks for a printed circuit board image in the test pattern that matches the template map. Through the above technical solution, the printed circuit board image matching system of the invention realizes fast matching of the image of the target printed circuit board, and effectively improves the accuracy of the image matching system of the printed circuit board.

In a specific implementation, if the test chart includes multiple target printed circuit board images, the matching module 104 can also be used to:

After the matching module 104, the method may further include:

The shielding module 105 is configured to shield the feature point pairs to match other printed circuit board images in the plurality of target printed circuit board images.

In the above embodiment, the test chart contains images of a plurality of printed circuit boards, and a printed circuit board is completed. After the image is matched, in order to avoid matching the other printed circuit board images, it is necessary to clear the feature points involved in the previous matching of the target printed circuit board image. For example, the conversion matrix calculated by the previous round of matching can find the printed circuit board image area corresponding to the printed circuit board image in the template image in the test chart, that is, by the template image The printed circuit board image, the printed circuit board image area in the test chart obtained through the conversion matrix mapping, masks the feature points in the area, and only considers the remaining feature points when performing other printed circuit board image matching. It can not only avoid the influence of the previous round, but also improve the efficiency of matching other printed circuit board images. The technical solution of the embodiment achieves fast matching of multiple printed circuit board images and improves the working efficiency of the printed circuit board image matching method.

In one embodiment, the printed circuit board image matching system of the present invention, the extraction module 102 can also be used to:

In practical application, the extraction module 102 of the printed circuit board image matching system of the present embodiment constructs a stable nonlinear scale space of a single Octave layer by nonlinear diffusion filtering using a KAZE operator, and utilizes the nonlinear scale space. Feature point extraction is performed on the template graph and the test graph, and the computational efficiency is greatly improved under the premise that the precision is relatively unchanged; moreover, the nonlinear scale space of a single Octave layer is constructed by using the KAZE operator, and the rotation can also be performed. The feature points of the changed printed circuit board image are extracted, which facilitates image matching in subsequent steps, and reduces the hardware cost of the printed circuit board image matching system.

In one embodiment, the printed circuit board image matching system of the present invention, the retrieval module 103 can also be used to:

In this embodiment, since the obtained first feature point set and the second feature point set have a large number of feature points, the feature points in the first feature point set and the second feature point set may be obtained by using, for example, a KAZE operator. The high-dimensional vector of the 64-dimensional feature is represented; and the first feature point of the first feature point set and the second feature point of the second feature point set are indexed and retrieved by using the multi-probe LSH index function, and finally the feature point pair is obtained. . Through the above technical solution, the efficiency and the matching precision of the retrieval pairing are effectively improved, and the working efficiency of the printed circuit board image matching system is further improved.

As shown in FIG. 4, FIG. 4 is a schematic structural diagram of a printed circuit board image matching system according to another embodiment of the present invention. After the calculating module 103, the method further includes:

The calculating module 106 is configured to calculate a best matching distance and a second best matching distance between the first feature point and the second feature point in the feature point pair;

The determining module 107 is configured to determine the reliability of the feature point pair by comparing the difference between the best matching distance and the sub-optimal matching distance and the preset threshold value, and filter the feature point pair according to the reliability.

In the above embodiment, in order to further improve the accuracy of the printed circuit board image matching system of the present invention, the feature points of the first feature point set and the second feature point set are searched and paired by using the multi-probe LSH index to obtain features. After the point is paired, certain measures can be taken to identify the reliability of the obtained feature point pairs. In the implementation, determining the feature point pair by comparing the difference between the best matching distance of the first feature point and the second feature point in the feature point pair and the sub-optimal matching distance and the preset threshold value Reliability, filtering the feature point pairs according to reliability, effectively improving the accuracy of the printed circuit board image matching method, and further improving the efficiency of the printed circuit board image matching method of the present invention.

In one embodiment, the printed circuit board image matching system of the present invention, the determining module 107 may also For:

In the above embodiment, the feature point pair whose difference between the best matching distance and the second best matching distance is greater than the preset threshold is retained, and the difference between the best matching distance and the second best matching distance is not greater than the preset threshold. Elimination of the printed circuit board image matching system of the present invention improves the accuracy of the printed circuit board image matching system of the present invention.

In one embodiment, the printed circuit board image matching system of the present invention, after the matching module 104, further includes:

The correction module 108 is configured to correct the printed circuit board image in the test chart according to the target printed circuit board image in the template image.

In practical applications, the image correction method of the printed circuit board image in the test chart, including but not limited to geometric correction, angle correction, etc., may be performed according to the target printed circuit board image in the template image.

In one embodiment, the printed circuit board image matching system of the present invention, the matching module 104 can also be used to:

In a specific implementation, if there is no image of the target printed circuit board in the test chart, and there is only one image of the target printed circuit board in the template image, it is also possible to calculate such a conversion matrix, thereby forming an incorrect pairing. Therefore, in order to further improve the accuracy of the printed circuit board image matching method of the present invention, the target in the test chart can be printed. The shape of the board is filtered a priori.

In one embodiment, the printed circuit board image matching system of the present invention, after the matching module 104, may further include:

The shape prior module 109 is configured to compare the morphological features of the target printed circuit board image in the test chart and the template image to print the target image in the test chart that is inconsistent with the morphological feature of the target printed circuit board image in the template image. The board image is filtered.

Since the image area of the printed circuit board is generally a convex polygon, it can be assumed that the image area of the target printed circuit board in the template image is also a convex polygon after being mapped; and, after being mapped in the test chart The area of the image area of the target printed circuit board should also be approximately equivalent to the image area of the target printed circuit board in the template image. Therefore, in practical applications, the printed circuit board image matching system of the present invention can utilize the shape prior module 109 to determine whether the image area of the mapped target printed circuit board in the test chart is still a convex polygon and The area is roughly equivalent to the image area of the target printed circuit board in the template map to determine whether the match was successful. If the matching is successful, the geometrically corrected printed circuit board image that is matched this time is output, otherwise the matching process is ended.

The above-mentioned printed circuit board image matching method and system, by performing feature point extraction on the template image and the test pattern of the obtained target printed circuit board respectively, obtaining the first feature point set of the template image and the second feature of the test chart a point set; recalculating a similarity value between the first feature point of the first feature point set and the second feature point of the second feature point set, and the first feature point and the second feature according to the similarity value Pointing is performed to obtain a pair of feature points; calculating a conversion matrix of the template of the target printed circuit board to the test pattern according to the feature point pair, and using the conversion matrix to find a print matching the template image in the test chart Board image. Through the above technical solution, the printed circuit board image matching method of the invention realizes the fast matching of the printed circuit board image, and effectively improves the accuracy of the printed circuit board image matching method.

The technical features of the above-described embodiments may be arbitrarily combined. For the sake of brevity of description, all possible combinations of the technical features in the above embodiments are not described. However, as long as there is no contradiction between the combinations of these technical features, All should be considered as the scope of this manual.

The above-described embodiments are merely illustrative of several embodiments of the present invention, and the description thereof is more specific and detailed, but is not to be construed as limiting the scope of the invention. It should be noted that a number of variations and modifications may be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, the scope of the invention should be determined by the appended claims.

Claims

A printed circuit board image matching method, comprising the steps of:

Obtaining a template image and a test chart of the target printed circuit board; wherein the template image is an angle-corrected image of the target printed circuit board, the test chart is an angle of the target printed circuit board Corrected image;

Performing feature point extraction on the template graph and the test graph respectively, and acquiring a first feature point set of the template graph and a second feature point set of the test graph;

Calculating a similarity value between the first feature point of the first feature point set and the second feature point of the second feature point set, and pairing the first feature point and the second feature point according to the similarity value, Obtaining feature point pairs;

Calculating a conversion matrix of the template of the target printed circuit board to the test pattern according to the feature point pair, and using the conversion matrix to find a printed circuit board image in the test chart that matches the template image.
The printed circuit board image matching method according to claim 1, wherein the step of performing feature point extraction on the template map and the test map separately comprises:

The nonlinear scale space of a single Octave layer is constructed by using a KAZE operator, and the feature points are extracted from the template map and the test map by using the nonlinear scale space.
The printed circuit board image matching method according to claim 1, wherein the calculating a similarity value between the first feature point of the first feature point set and the second feature point of the second feature point set The steps include:

Indexing and retrieving the first feature point of the first feature point set and the second feature point of the second feature point set by using a multi-probe index function, and calculating a metric distance between the first feature point and the second feature point;

And determining a similarity value between the first feature point and the second feature point according to the metric distance.
The printed circuit board image matching method according to claim 1, further comprising: after the step of obtaining the feature point pairs of the first feature point set and the second feature point set, further comprising:

Calculating a best matching distance and a second best matching distance between the first feature point and the second feature point in the pair of feature points;

The reliability of the feature point pair is determined by comparing the difference between the best matching distance and the sub-optimal matching distance and the preset threshold value, and the feature point pair is filtered according to the reliability.
The printed circuit board image matching method according to claim 4, wherein the determining the feature point pair by comparing a difference between the best matching distance and a sub-optimal matching distance and a preset threshold value Reliability, the steps of filtering feature point pairs based on reliability include:

If the difference between the best matching distance and the sub-optimal matching distance is greater than a preset threshold, determining that the feature point pair is reliable; otherwise, determining that the feature point pair is unreliable, and filtering the feature point pair.
The printed circuit board image matching method according to claim 1, wherein the calculating the conversion matrix of the first feature point to the second feature point of the plurality of sets of feature point pairs comprises:

Calculating a transformation matrix of the first feature point to the second feature point of the plurality of sets of feature point pairs by using a random sample set algorithm;

After the step of calculating a conversion matrix of the first feature point to the second feature point of the plurality of sets of feature point pairs by using the random sample set algorithm, the method further includes:

Selecting a set of feature points with the smallest error pair as the conversion matrix of the template map to the test chart; wherein the conversion matrix represents the target printed circuit board image in the template image to the template image The mapping relationship of the printed circuit board images in the test chart corresponding to the target printed circuit board image.
The printed circuit board image matching method according to claim 1, wherein after the step of using the conversion matrix to search for an image of the printed circuit board that matches the template image in the test pattern, the method further includes:

The printed circuit board image in the test chart is corrected based on the printed circuit board image in the template map.
The printed circuit board image matching method according to claim 1, wherein the step of acquiring a template map and a test pattern of the target printed circuit board comprises:

Obtaining a template image and a test chart of the plurality of target printed circuit boards; wherein the template image is an angle-corrected image of the plurality of target printed circuit boards, and the test chart is printed for the plurality of targets An unangled image of the board;

Calculating, according to the feature point pair, a template of the target printed circuit board to a conversion matrix of the test pattern, and using the conversion matrix to search for a printed circuit board image matching the template image in the test image, including :

Calculating a conversion matrix of the template image of one of the target printed circuit boards to the test pattern according to the feature point pair, and using the conversion matrix to find the one of the target printed circuit board images in the test chart that matches the template image ;

After the step of using the conversion matrix to find the one of the target printed circuit board images in the test chart that matches the template image, the method further includes:

The feature point pairs are masked to match other printed circuit board images in the plurality of target printed circuit board images.
The printed circuit board image matching method according to claim 1, wherein after the step of using the conversion matrix to search for a target printed circuit board image matching the template image in the test pattern, the method further comprises:

By comparing the morphological features of the target printed circuit board image in the test chart and the template image, the target printed circuit board image in the test chart that is inconsistent with the morphological features of the target printed circuit board image in the template image is filtered.
A printed circuit board image matching system, comprising:

An acquisition module, configured to obtain a template image and a test chart of the target printed circuit board; wherein the template image is an angle corrected image of the target printed circuit board, and the test chart is the target printed circuit An unangled image of the board;

An extraction module, configured to perform feature point extraction on the template image and the test image respectively, and acquire a first feature point set of the template image and a second feature point set of the test image;

a pairing module, configured to calculate a similarity value between the first feature point of the first feature point set and the second feature point of the second feature point set, and the first feature point and the second feature point according to the similarity value Feature points are paired to obtain feature point pairs;

a matching module, configured to calculate a conversion matrix of the template map of the target printed circuit board to the test pattern according to the feature point pair, and use the conversion matrix to search for a printed circuit board image in the test chart that matches the template image .