CN105701776A - Lens distortion correcting method and system used for automatic optical detection - Google Patents

Abstract

The present invention discloses a lens distortion correcting method and system used for automatic optical detection. The method comprises the processes of selecting an uneven checkerboard as a calibration board, and obtaining a distorted figure; carrying out the angular point rough extraction on the distorted figure; carrying out the accurate angular point extraction on the roughly extracted dense angular points via the erosion and dilation and the blob analysis to obtain the real angular points; calculating a distortion model parameter between the coordinates of the real angular points and the ideal diagram angular point coordinates; according to the distortion model parameter and the coordinate of each pixel point in an ideal diagram, calculating the coordinate of each pixel point in the distorted figure; obtaining a pixel value corresponding to the coordinate of each pixel point in the distorted figure according to the coordinate of each pixel point in the distorted figure. According to the present invention, with the usage of the uneven checkerboard, the edge feature points are more and denser, so that the actual situation is approached better, and the calculated distortion model parameter is more reasonable. By the erosion and dilation and the blob analysis, the real angular points are extracted, the angular point extraction precision is high, and a distortion correction effect is good.

Description

A kind of lens distortion antidote for automatic optics inspection and system

Technical field

The invention belongs to AOI Automatic Measurement Technique field, be specifically related to a kind of lens distortion antidote for automatic optics inspection and system。

Background technology

In automatic detection field and vision measurement field, the quality of camera lens directly affects detection or measurement effect, has very eurypalynous camera lens in the market, but distortion can be caused in varying degrees, even expensive again, the camera lens that effect is good again, distortion can not be evaded。So when detection and measurement, first will solve the distortion impact on subsequent treatment, correct distortion as far as possible。What existing distortion correction adopted is uniform gridiron pattern, is distributed in edge owing to distorting more, adopts the resultant error that uniform gridiron pattern calculates bigger；And being generally adopted the method rejecting redundancy angle point that angle point is removed in the process accurately extracting angle point, process is complicated, and angle point grid precision is low, and final rectification effect is poor。

Summary of the invention

The purpose of the present invention is contemplated to solve the deficiency that above-mentioned background technology exists, it is provided that a kind of lens distortion antidote for automatic optics inspection and system。

The technical solution used in the present invention is: a kind of lens distortion antidote for automatic optics inspection, comprises the following steps:

Step 1, chooses non-homogeneous gridiron pattern as scaling board, waits that correcting lens shooting scaling board obtains distortion figure；

Step 2, carries out angle point to distortion figure and slightly extracts, obtain intensive angle point；

Step 3, analyzes to the thick intensive angle point extracted carry out accurate angle point grid by corroding expansion and blob, obtain real angle point；

Step 4, calculates the distortion model parameter between real angular coordinate and ideograph angular coordinate；

Step 5, calculates the coordinate of each pixel in distortion figure according to the coordinate of pixel each in distortion model parameter and ideograph；

Step 6, obtains, according to the coordinate of each pixel in distortion figure, the pixel value that in distortion figure, each pixel coordinate is corresponding。

Further, described distortion figure is carried out the process that angle point slightly extracts it be: distortion figure is carried out binary conversion treatment and obtains bianry image, bianry image is carried out template matching, obtains intensive angle point。

Further, described distortion model parameter is obtained by method of least square and LM optimization calculating。

Further, in described distortion figure, the computational methods of the coordinate of each pixel are:

$x=\underset{i=0}{\overset{N}{\Σ}}\underset{j=0}{\overset{N-i}{\Σ}}{a}_{ij}{u}^i{v}^j$

$y=\underset{i=0}{\overset{N}{\Σ}}\underset{j=0}{\overset{N-i}{\Σ}}{b}_{ij}{v}^i{u}^j$

In formula: x, y respectively distort the transverse and longitudinal coordinate of each pixel in figure, the transverse and longitudinal coordinate of each pixel in u, v respectively ideograph, a_ij、b_ijRespectively real distortion model parameter between angular coordinate and ideograph angular coordinate, N value is 3 or 4。

Further, the pixel value that in described distortion figure, each pixel coordinate is corresponding obtains by the coordinate of each pixel in distortion figure carries out the method for bilinear interpolation in distortion figure。

A kind of lens distortion correction system for automatic optics inspection, including:

Image capture module, is used for gathering distortion figure, and sends distortion figure to the thick extraction module of angle point；

The thick extraction module of angle point, slightly extracts for the distortion figure received is carried out angle point, obtains intensive angle point, and send it to the accurate extraction module of angle point；

The accurate extraction module of angle point, for intensive angle point is analyzed carry out accurate angle point grid by being corroded expansion and blob, obtains real angle point, and sends it to distortion Coordinate generation module；

Distortion Coordinate generation module, for calculating the coordinate of each pixel in distortion figure according to each pixel parameter in real angular coordinate and ideograph；

Coordinate mapping module, for obtaining, according to the coordinate of each pixel in distortion figure, the pixel value that in distortion figure, each pixel coordinate is corresponding。

Further, described image capture module include distortion figure acquisition module, its for choose non-homogeneous gridiron pattern as scaling board after, wait correct lens shooting scaling board obtain distortion figure。

Further, described distortion Coordinate generation module includes coordinate calculation module, and it is for calculating the coordinate of each pixel in distortion figure according to distortion model, and described distortion model is:

$x=\underset{i=0}{\overset{N}{\Σ}}\underset{j=0}{\overset{N-i}{\Σ}}{a}_{ij}{u}^i{v}^j$

$y=\underset{i=0}{\overset{N}{\Σ}}\underset{j=0}{\overset{N-i}{\Σ}}{b}_{ij}{v}^i{u}^j$

In formula: x, y respectively distort the transverse and longitudinal coordinate of each pixel in figure, the transverse and longitudinal coordinate of each pixel in u, v respectively ideograph, a_ij、b_ijRespectively real distortion model parameter between angular coordinate and ideograph angular coordinate, N value is 3 or 4。

The present invention adopts chessboard heterogeneous, makes Edge Feature Points distribution more more dense, is so more nearly practical situation, and the distortion model parameter calculated is more reasonable；Expanding and the blob analysis real angle point of extraction by corroding, angle point grid precision is high, and distortion correction is effective, and robustness is higher。Poor in picture quality, noise ratio is more, can extract angle point very accurately when distorting more serious, and highly stable, whole correcting process is simple, fast and easy。

Accompanying drawing explanation

The connection diagram of the system module of Fig. 1 present invention；

Fig. 2 is control flow chart of the present invention；

Fig. 3 is the non-homogeneous tessellated schematic diagram of the present invention；

Fig. 4 is the schematic diagram that angle point of the present invention slightly extracts；

Fig. 5 is the schematic diagram that angle point of the present invention accurately extracts。

Detailed description of the invention

Below in conjunction with the drawings and specific embodiments, the present invention is described in further detail, it is simple to be well understood to the present invention, but the present invention is not constituted restriction by them。

As it is shown in figure 1, a kind of lens distortion correction system for automatic optics inspection of the present invention, including:

Image capture module, is used for gathering distortion figure, and sends distortion figure to the thick extraction module of angle point；Image capture module include distortion figure acquisition module, its for choose non-homogeneous gridiron pattern as scaling board after, wait correct lens shooting scaling board obtain distortion figure；

The thick extraction module of angle point, slightly extracts for the distortion figure received is carried out angle point, obtains intensive angle point, and send it to the accurate extraction module of angle point；

The accurate extraction module of angle point, for intensive angle point is analyzed carry out accurate angle point grid by being corroded expansion and blob, obtains real angle point, and sends it to distortion Coordinate generation module；

Distortion Coordinate generation module, for calculating the coordinate of each pixel in distortion figure according to each pixel parameter in real angular coordinate and ideograph；Distortion Coordinate generation module includes coordinate calculation module, and it is for calculating the coordinate of each pixel in distortion figure according to distortion model；

Coordinate mapping module, for obtaining, according to the coordinate of each pixel in distortion figure, the pixel value that in distortion figure, each pixel coordinate is corresponding。

As shown in Figure 2-5, to adopt above-mentioned correction system to realize the process of lens distortion antidote as follows for the present invention:

Step 1, set scaling board: the present invention chooses non-homogeneous gridiron pattern as scaling board, non-homogeneous gridiron pattern refers to that its internal blockage is the gradual change formal distribution that center (center refers to gridiron pattern center) area is big, edge area is little, namely gridiron pattern is less than comparatively dense, Area comparison near the blockage of surrounding boundary, and it is relatively decentralized near the blockage ratio of gridiron pattern middle part, Area comparison is big, as it is shown on figure 3, only give the scaling board shape of 3*3。It is distributed in border owing to distorting, by smaller for gridiron pattern edge blockage area design, then the comparison of edge angle point just distribution is many, is more nearly practical situation more。This non-homogeneous gridiron pattern can make edge angle point distribution more more dense, and the mapping relations (distortion model parameter) between the distortion figure angle point and the ideograph angle point that so calculate are just more reasonable, final distortion correction better effects if。After scaling board is selected, after correcting lens shooting scaling board and obtaining distortion figure, being stored in image capture module, distortion figure is sent to the thick extraction module of angle point by image capture module。

Step 2, the distortion figure received is carried out X-comers and slightly extracts by the thick extraction module of angle point: it is to extract a series of angle point around real angle point that angle point slightly extracts。

The distortion figure of above-mentioned acquisition is carried out angle point when slightly extracting, first distortion figure is carried out binary conversion treatment and obtain bianry image, then further according to the symmetry of gridiron pattern intensity profile, bianry image is carried out template matching, obtain the intensive angle point of some row, send to the accurate extraction module of angle point。

As shown in Figure 4, template matching refers to mates with distortion figure by arranging a rectangle template, or distortion figure is traveled through, and finds, in distortion figure, the intensive angle point being distributed in gridiron pattern intersection that satisfies condition。The intensive angle point found after distortion figure is traveled through need to meet following condition: a-quadrant angle point is consistent with the gray scale of D region angle point, B region angle point is consistent with the gray scale of C region angle point, the gray scale of a-quadrant angle point and B region angle point is inconsistent, area shared by the angle point of a-quadrant and the area equation shared by the angle point of D region, the area shared by the angle point of B region and the area equation shared by the angle point of C region。

Step 3, X-comers accurately extracts: to a series of intensive angle point obtained in step 2, owing to angle point quantity is a lot, comparatively dense is compared in distribution, but be not strictly connect together, mode according to existing rejecting redundancy angle point obtains real angle point, then processing procedure is more complicated, therefore its angle point distribution situation of present invention, these angle points are corroded and expansion process, a little intensive angle points are all linked up one connected region of formation, the angle point obtaining white as shown in Figure 5 is distributed blob block, then again blob block is carried out blob analysis, it is eventually found the particle of connected region as real angle point, after real angle point is determined, its coordinate in distortion figure may determine that。It is the image processing method of a kind of routine that blob analyzes, and blob is analyzed and is applied to during angle point accurately extracts by the present invention, and connected region is detected, by the girth of connected region, area, particle etc. feature calculation out, finally searches out connected region central point as real angle point。

Step 4, distortion model parameter calculates: real angle point grid out after, it needs to be determined that real corresponding relation between angle point and ideograph angle point, specifically it is embodied in the mapping relations between its coordinate, this key point in the process of distortion correction, the method that the present invention is optimized by method of least square and LM, calculates the distortion model parameter a between the coordinate of real angle point and the coordinate of corresponding ideograph angle point_ij、b_ij(mapping relations)。

Method of least square is the mathematical optimization techniques of a kind of routine, by minimum according to the mean square deviation sum between actual value and ideal value, calculates the distortion model parameter a between the coordinate of real angle point and the coordinate of corresponding ideograph angle point_ij、b_ij。Not being optimum owing to method of least square calculates the parameter of distortion model, when rectification effect is required higher occasion by application, the precision of distortion model parameter also corresponding requirements is higher, optimizes now by LM and can obtain optimized parameter。It is by ceaselessly recursive iteration that LM optimizes, and each iteration makes difference between angular coordinate and the actual distortion figure coordinate calculated by distortion model less, when the standard arranging a difference, when iteration repeatedly after, so that it may reach the standard of setting。

Step 5, distortion correction: by the distortion model parameter in step 4 and the coordinate of each pixel in ideograph, be updated in the distortion model of setting, coordinate x, y of each pixel in distortion figure can be obtained。The coordinate calculated by distortion model is floating number, and it does not have on all four point on distortion figure, it is therefore necessary to calculate, by ad hoc approach, the pixel value that mark is corresponding。The present invention passes through interpolation algorithm, preferably the mode of bilinear interpolation utilizes the pixel value of surrounding to calculate, as by distortion model, the gray value that coordinate is corresponding, the coordinate of each pixel being about to obtain carries out bilinear interpolation in distortion figure, can obtain the pixel value that in distortion figure, each pixel coordinate is corresponding。In distortion figure, the coordinate of each pixel and pixel value are determined, namely achieve distortion correction。

The present invention calculates the distortion model of the coordinate of each pixel in distortion figure:

$x=\underset{i=0}{\overset{N}{\Σ}}\underset{j=0}{\overset{N-i}{\Σ}}{a}_{ij}{u}^i{v}^j$

$y=\underset{i=0}{\overset{N}{\Σ}}\underset{j=0}{\overset{N-i}{\Σ}}{b}_{ij}{v}^i{u}^j$

In formula: x, y respectively distort the transverse and longitudinal coordinate of each pixel in figure, the transverse and longitudinal coordinate of each pixel in u, v respectively ideograph, a_ij、b_ijRespectively real distortion model parameter between angular coordinate and ideograph angular coordinate, N is setting value, and to ideal situation, the value of N is more big, and rectification effect is more good, but N value is crossed conference and caused calculating excessively complicated, and therefore, N value of the present invention is 3 or 4。

The foregoing is only the preferred embodiments of the present invention, it is not limited to the present invention, although the present invention being described in detail with reference to previous embodiment, for a person skilled in the art, technical scheme described in foregoing embodiments still can be modified by it, or wherein portion of techniques feature carries out equivalent replacement。All within the spirit and principles in the present invention, any amendment of making, equivalent replacement, improvement etc., should be included within protection scope of the present invention。

Claims (9)

1. the lens distortion antidote for automatic optics inspection, it is characterised in that comprise the following steps:

Step 1, chooses non-homogeneous gridiron pattern as scaling board, waits that correcting lens shooting scaling board obtains distortion figure；

Step 2, carries out angle point to distortion figure and slightly extracts, obtain intensive angle point；

Step 3, analyzes to the thick intensive angle point extracted carry out accurate angle point grid by corroding expansion and blob, obtain real angle point；

Step 4, calculates the distortion model parameter between real angular coordinate and ideograph angular coordinate；

Step 5, calculates the coordinate of each pixel in distortion figure according to the coordinate of pixel each in distortion model parameter and ideograph；

Step 6, obtains, according to the coordinate of each pixel in distortion figure, the pixel value that in distortion figure, each pixel coordinate is corresponding。

2. a kind of lens distortion antidote for automatic optics inspection according to claim 1, it is characterised in that: the blockage within described non-homogeneous gridiron pattern is the gradual change formal distribution that center area is big, edge area is little。

3. a kind of lens distortion antidote for automatic optics inspection according to claim 1, it is characterized in that, described distortion figure is carried out the process that angle point slightly extracts it be: distortion figure is carried out binary conversion treatment and obtains bianry image, bianry image is carried out template matching, obtains intensive angle point。

4. a kind of lens distortion antidote for automatic optics inspection according to claim 1, it is characterised in that: described distortion model parameter optimizes calculating by method of least square and LM and obtains。

5. a kind of lens distortion antidote for automatic optics inspection according to claim 1, it is characterised in that in described distortion figure, the computational methods of the coordinate of each pixel are:

$x=\underset{i=0}{\overset{N}{\Σ}}\underset{j=0}{\overset{N-i}{\Σ}}{a}_{ij}{u}^i{v}^j$

$y=\underset{i=0}{\overset{N}{\Σ}}\underset{j=0}{\overset{N-i}{\Σ}}{b}_{ij}{v}^i{u}^j$

In formula: x, y respectively distort the transverse and longitudinal coordinate of each pixel in figure, the transverse and longitudinal coordinate of each pixel in u, v respectively ideograph, a_ij、b_ijRespectively real distortion model parameter between angular coordinate and ideograph angular coordinate, N value is 3 or 4。

6. a kind of lens distortion antidote for automatic optics inspection according to claim 1, it is characterised in that: the pixel value that in described distortion figure, each pixel coordinate is corresponding obtains by the coordinate of each pixel in distortion figure carries out the method for bilinear interpolation in distortion figure。

7. the lens distortion correction system for automatic optics inspection, it is characterised in that: include

Image capture module, is used for gathering distortion figure, and sends distortion figure to the thick extraction module of angle point；

The thick extraction module of angle point, slightly extracts for the distortion figure received is carried out angle point, obtains intensive angle point, and send it to the accurate extraction module of angle point；

The accurate extraction module of angle point, for intensive angle point is analyzed carry out accurate angle point grid by being corroded expansion and blob, obtains real angle point, and sends it to distortion Coordinate generation module；

Distortion Coordinate generation module, for calculating the coordinate of each pixel in distortion figure according to each pixel parameter in real angular coordinate and ideograph；

Coordinate mapping module, for obtaining, according to the coordinate of each pixel in distortion figure, the pixel value that in distortion figure, each pixel coordinate is corresponding。

8. a kind of lens distortion correction system for automatic optics inspection according to claim 7, it is characterized in that: described image capture module includes distortion figure acquisition module, its for choose non-homogeneous gridiron pattern as scaling board after, wait correct lens shooting scaling board obtain distortion figure。

9. a kind of lens distortion correction system for automatic optics inspection according to claim 7, it is characterized in that: described distortion Coordinate generation module includes coordinate calculation module, it is for calculating the coordinate of each pixel in distortion figure according to distortion model, and described distortion model is:

$x=\underset{i=0}{\overset{N}{\Σ}}\underset{j=0}{\overset{N-i}{\Σ}}{a}_{ij}{u}^i{v}^j$

$y=\underset{i=0}{\overset{N}{\Σ}}\underset{j=0}{\overset{N-i}{\Σ}}{b}_{ij}{v}^i{u}^j$

In formula: x, y respectively distort the transverse and longitudinal coordinate of each pixel in figure, the transverse and longitudinal coordinate of each pixel in u, v respectively ideograph, a_ij、b_ijRespectively real distortion model parameter between angular coordinate and ideograph angular coordinate, N value is 3 or 4。