CN101031199A - Linear form and position adapting method based on pin - Google Patents

Abstract

The method comprises: 1) setting an interested area ROI; 2) making image process; 3) making rough positioning; 2) detecting the feature of component; 5) making fine position. In the step 2, the invention uses an improved row straight line fit method to make straight line fit for the central point of each pin of component so as to remove the deviated points. The invention can be used in a detection system of surface mount machine (SMT) to make detection and recognition for the surface-mounted components.

Description

Morpheme line fitting method based on pin

Technical field

The invention belongs to the image processing field that the chip mounter vision system in the surface mount process uses, refer in particular to a kind of morpheme line fitting method based on pin.

Background technology

Vision centering detection system is to carry out the detection of package detection and center and corner by the element that video camera utilizes image processing techniques to treat to mount, and is that chip mounter can be finished one of key technology of the task of mounting rapidly and accurately.Its main difficult point is that flying-vision (On-Fly-Vision) is the real-time of image processing; and the packing forms for the treatment of mount components is various; from miniature; miniature component; up to large-scale packaging; the detection algorithm of each encapsulated type is all different; especially some large-scale encapsulation such as QFP (Quad FlatPackage; flat packaging all around); BGA (Ball Grid Array; and its detection algorithm of thin space SMD (Surface Mount Device, element pasted on surface) difficult point especially array tin ball sealing dress) etc.; and the technology of this respect always is subjected to patent protection, and is rarely known by the people especially at home.The high-accuracy machine vision navigation system is to satisfy the effective way of placement accuracy.

Summary of the invention

Technical problem to be solved by this invention is: a kind of morpheme line fitting method based on pin is provided, and it can carry out the detection and the identification of components and parts accurately and efficiently in the process of mounting.

The invention provides a kind of morpheme line fitting method based on pin, it may further comprise the steps:

The first step, the region of interest ROI step is set, comprises the chip region and be set to region of interest ROI, and this region of interest ROI image is carried out binaryzation;

Second step, image processing step carry out preliminary treatment to above-mentioned region of interest ROI, therefrom are partitioned into each pin field of chip, judge whether number of pins meets the due number of pins of this chip;

The 3rd step, coarse positioning, the center that utilizes each pin of chip are tentatively determined the centre coordinate (s of element _x', s _y'), the pin of chip central point is carried out fitting a straight line, obtain four straight lines, calculate the angle of these four straight lines and trunnion axis deviation, averaging is θ ', and wherein maximum differential seat angle is designated as β;

The 4th step, element characteristics detect, on the image of binaryzation not, place scale component pin is measured, obtain comprising that pin is wide, pin long and the relative position information of pin, result and canonical parameter are compared, whether judgment component is qualified, then enters for the 5th step as if qualified;

The 5th step, accurate location, establishing accurate corner is θ, its (θ '-β/2, θ '+β/2) in the scope, accurate center (s _x, s _y) with (s _x', s _y') be the center, δ is within the scope of radius, and δ is the maximum possible error of coarse positioning result in the 3rd step, can rule of thumb set, and establishing the component pin center that respectively calculates in the image segmentation is a _i, the centre coordinate that can be obtained waiting pasting each corresponding pin of element by priori is c _i, for the error vector e between every pair of central point _iObtain by following formula:

$e_i=\left[\begin{array}{c}{s}_x\\ s_y\end{array}\right]+\left[\begin{array}{cc}\cos \mathrm{\θ}& -\sin \mathrm{\θ}\\ \sin \mathrm{\θ}& \cos \mathrm{\θ}\end{array}\right]\left[\begin{array}{c}{x}_{a_i}\\ y_{a_i}\end{array}\right]-\left[\begin{array}{c}{x}_{c_i}\\ y_{c_i}\end{array}\right]=\left[\begin{array}{cccc}1& 0& x_{a_i}& -y_{a_i}\\ 0& 1& y_{a_i}& x_{a_i}\end{array}\right]\left[\begin{array}{c}{s}_x\\ s_y\\ \cos \mathrm{\θ}\\ \sin \mathrm{\θ}\end{array}\right]-\left[\begin{array}{c}{x}_{c_i}\\ y_{c_i}\end{array}\right]---\left(1\right)$

If:

$\left\{\begin{array}{cc}{s}_x={s_x}^{\&prime;}+k*\mathrm{\&Delta;x}& k<\mathrm{\&delta;}/\mathrm{\&Delta;x}\\ s_y={s_y}^{\&prime;}+l*\mathrm{\&Delta;y}& l<\mathrm{\&delta;}/\mathrm{\&Delta;y}\\ \mathrm{\&theta;}={\mathrm{\&theta;}}^{\&prime;}+h*\mathrm{\&Delta;\&theta;}& h<\mathrm{\&beta;}/\mathrm{\&Delta;\&theta;}\end{array}\right.---\left(2\right)$

Search for to ask and make ∑ e _i ²Value k hour, l, the value of h can draw accurate positioning result (S according to (2) formula _x, S _y, θ).

In wherein said the 3rd step centre coordinate of X pin collection and Y pin collection being carried out the method that straight line fits may further comprise the steps:

1) concentrate the centre coordinate point of all pins that comprised to carry out the least square line match to X pin collection and Y pin, formula is Y=a ' * X+b ';

2) whether judge in the above-mentioned centre coordinate point greater than the required minimum points N of the fitting a straight line that sets _Min, if not, then withdraw from; If then obtain the distance z that each centre coordinate is put straight line _i, and judgement maximum z wherein _kWhether greater than given threshold value z _Max, if, then reject this centre coordinate point, then N-1 remaining centre coordinate point carried out least square fitting, when being not more than given slope error ξ, the slope differences of the straight line of the l time and the l-1 time match finishes;

3) Y=a*X+b that obtains a result at last.

The invention has the beneficial effects as follows: the present invention can satisfy the precision and the rate request of chip mounter element position detecting system, can carry out the detection and the identification of components and parts accurately and efficiently in the process of mounting.

Description of drawings

Fig. 1 is the schematic diagram of the area-of-interest of the present invention's setting;

Fig. 2 is the component pin collection schematic diagram of the present invention's definition;

Fig. 3 is the flow chart of the inventive method;

The present invention will be further described below in conjunction with accompanying drawing.

Embodiment

Morpheme line fitting method based on pin of the present invention may further comprise the steps:

The first step, region of interest ROI is set, as shown in Figure 1, in the chip image processing procedure, because die size has nothing in common with each other, chip shared region area in image is not very big as a rule, if entire image is carried out analyzing and processing, can waste the plenty of time.In order to improve the efficient of detection algorithm, in processing procedure, position and the movement locus of planning the placement head that comes out and the information such as size of element according to feed appliance, can roughly determine a residing zone of chip image, ignore the zone that does not comprise chip features in the image, the zone that only comprises the chip place is set to region of interest ROI, and carries out binaryzation.

Second step, image processing are carried out preliminary treatment to region of interest ROI, and therefrom are partitioned into each pin field of element.The formal parameter of considering element is known, and can determine should be in particular range corresponding to the area of pin field.Utilize this priori, to regional reference area feature and the direction character after the sign.If area that should the zone within the scope of setting, is not made as background with it, then Sheng Xia zone is each pin of counter element, and the direction of center by element and pin field can be divided into it pin on certain limit.So far can come decision element whether to lack pin by the number in zone,, think that then element is defective, pick up next element again if the due number of pins of number of regions and element does not meet.

Four limits of definition element are: NOUTH, SOUTH, EAST, WEST, as shown in Figure 2, corresponding four pin collection: NLeadset, SLeadset, ELeadset, WLeadset.

Determine according to the centre coordinate of pin and the appearance information of pin which pin collection pin belongs to, because component pin generally has leptosomatic characteristics, can use with regard to the feature of a direction like this, the angle that is to say the direction of pin of NLeadset, SLeadset pin collection and Y direction is smaller, and just bigger with the angle of directions X, be referred to as the pin of Y direction; In like manner, the pin of ELeadset, WLeadset pin collection and the angle of directions X are smaller, and just bigger with the angle of Y direction, are referred to as the pin of directions X.Direction by component pin is divided into Y direction pin and directions X pin with it, and then determines the definite ownership of each component pin in the orientation of whole element centre coordinate according to each pin centre coordinate.

The 3rd step, coarse positioning, the center that utilizes each pin are tentatively determined the center (s of element _x', s _y'), the central point of four pin collection is carried out straight line fit, can obtain four straight line NLine, SLine, ELine, WLine.And straight line ELine, WLine revolved turn 90 degrees, after the rotation in theory these four straight lines should be parallel, but the straight line that in fact fits out is not completely parallel, these four straight lines are unequal with respect to the angle of trunnion axis generally speaking, it certainly exists a differential seat angle and can average to it as coarse positioning, and the result is designated as θ '.Its maximum angle difference is designated as β.

The 4th step, element characteristics detect, and place scale on the image of binaryzation not component pin is measured, and comprise that pin is wide, pin long and the information such as relative position of pin, and result and canonical parameter are compared, and whether judgment component is qualified.

The 5th step, accurate location, the result of coarse positioning is (s _x', s _y', θ '), error is bigger, from the result in second step know rotational angle theta should (θ '-β/2, θ '+β/2) in the scope, in like manner, the accurate center (s of element _x, s _y) should be with (s _x'-s _y') be the center, δ is within the scope of radius, and δ is the maximum possible error of coarse positioning result in the 3rd step, can rule of thumb set, and establishing the component pin center that respectively calculates in the image segmentation is a _i, the centre coordinate that can be obtained waiting pasting each corresponding pin of element by priori is c _i, for the error vector e between every pair of central point _iObtain by following formula:

$e_i=\left[\begin{array}{c}{s}_x\\ s_y\end{array}\right]+\left[\begin{array}{cc}\cos \mathrm{\&theta;}& -\sin \mathrm{\&theta;}\\ \sin \mathrm{\&theta;}& \cos \mathrm{\&theta;}\end{array}\right]\left[\begin{array}{c}{x}_{a_i}\\ y_{a_i}\end{array}\right]-\left[\begin{array}{c}{x}_{c_i}\\ y_{c_i}\end{array}\right]=\left[\begin{array}{cccc}1& 0& x_{a_i}& -y_{a_i}\\ 0& 1& y_{a_i}& x_{a_i}\end{array}\right]\left[\begin{array}{c}{s}_x\\ s_y\\ \cos \mathrm{\&theta;}\\ \sin \mathrm{\&theta;}\end{array}\right]-\left[\begin{array}{c}{x}_{c_i}\\ y_{c_i}\end{array}\right]$

If:

$\left\{\begin{array}{cc}{s}_x={s_x}^{\&prime;}+k*\mathrm{\&Delta;x}& k<\mathrm{\&delta;}/\mathrm{\&Delta;x}\\ s_y={s_y}^{\&prime;}+l*\mathrm{\&Delta;y}& l<\mathrm{\&delta;}/\mathrm{\&Delta;y}\\ \mathrm{\&theta;}={\mathrm{\&theta;}}^{\&prime;}+h*\mathrm{\&Delta;\&theta;}& h<\mathrm{\&beta;}/\mathrm{\&Delta;\&theta;}\end{array}\right.$

Search for to ask and make ∑ e _i ²Value k hour, l, the value of h can accurate setting element according to following formula.

The flow chart of the inventive method as shown in Figure 3.

In addition, the present invention improves existing line fitting method, and present normally used line fitting method generally is a least square method.The shortcoming of this method is if deviation appears in the part point of participation fitting a straight line, will influence whole fitting effect.Consider the pin warpage that illumination and element may occur itself, indivedual points may not belong to this straight line, and therefore this point should not participated in fitting a straight line.Traditional least square method is difficult to remove these points.The present invention has designed a kind of more sane fitting a straight line algorithm for this reason, and it can address this problem well.Its basic thought is:

Now utilize least square fitting to draw straight line L ' according to N point, its linear equation is Y=a ' * X+b '; Judge that more whether the point that participates in fitting a straight line is greater than the required minimum points N of the fitting a straight line that sets _Min, if not, then withdraw from; If then obtain the distance z that each puts straight line L ' _i, and judgement maximum z wherein _kWhether greater than given threshold value z _Max, if illustrate that then this point does not belong to this straight line, reject this point, remaining N-1 is put carry out least square fitting then, when the slope of the straight line of the l time and the l-1 time match is not more than given slope error ξ, finish, draw accurate straight line L at last, linear equation is Y=a*X+b.

This is improved the row line fitting method apply to the 3rd step of the present invention, during the fitting a straight line of unit's line each pin central point, then in like manner, each center point coordinate is carried out the least square line match earlier, again each central point is carried out cycle criterion to the distance of default straight line, play the point that removes ultimate range, again remaining central point is carried out least square fitting, so circulation, when being not more than given slope error ξ, finishes the slope of the straight line of the l time and the l-1 time match, can accurately draw its four straight lines of X pin collection and Y pin collection at last, NLine, SLine, ELine, WLine.

This shows, the present invention is by being provided with region of interest ROI step, image processing step, coarse positioning step, element characteristics detection step and accurate positioning step, whether chip is progressively detected qualified, while is the positioning chip position accurately, also adopted improved line fitting method, make the fitting a straight line result in the coarse positioning step more accurate, thereby the positioning result that accurate positioning step is drawn is more accurate.

Claims (2)

1, a kind of morpheme line fitting method based on pin, it comprises step:

The first step, the region of interest ROI step is set, comprises the chip region and be set to region of interest ROI, and this region of interest ROI image is carried out binaryzation;

Second step, image processing step carry out preliminary treatment to above-mentioned region of interest ROI, therefrom are partitioned into each pin field of chip, judge whether number of pins meets the due number of pins of this chip;

The 3rd step, coarse positioning, the center that utilizes each pin of chip are tentatively determined the centre coordinate (s of element _x', s _y'), the pin of chip central point is carried out fitting a straight line, obtain four straight lines, calculate the angle of these four straight lines and trunnion axis deviation, averaging is θ ', and wherein maximum differential seat angle is designated as β;

The 4th step, element characteristics detect, on the image of binaryzation not, place scale component pin is measured, obtain comprising that pin is wide, pin long and the relative position information of pin, result and canonical parameter are compared, whether judgment component is qualified, then enters for the 5th step as if qualified;

The 5th step, accurate location, establishing accurate corner is θ, its (θ '-β/2, θ '+β/2) in the scope, accurate center (s _x, s _y) with (s _x', s _y') be the center, δ is within the scope of radius, and δ is above-mentioned the 3rd step coarse positioning result's a maximum possible error, and establishing the component pin center that respectively calculates in the image segmentation is a _i, the centre coordinate that can be obtained waiting pasting each corresponding pin of element by priori is c _i, for the error vector e between every pair of central point _iObtain by (1) formula:

$e_i=\left[\begin{array}{c}{s}_x\\ s_y\end{array}\right]+\left[\begin{array}{cc}\cos \mathrm{\&theta;}& -\sin \mathrm{\&theta;}\\ \sin \mathrm{\&theta;}& \cos \mathrm{\&theta;}\end{array}\right]\left[\begin{array}{c}{x}_{a_i}\\ y_{a_i}\end{array}\right]=\left[\begin{array}{cccc}1& 0& x_{a_i}& -y_{a_i}\\ 0& 1& y_{a_i}& x_{a_i}\end{array}\right]\left[\begin{array}{c}{s}_x\\ s_y\\ \cos \mathrm{\&theta;}\\ \sin \mathrm{\&theta;}\end{array}\right]-\left[\begin{array}{c}{x}_{c_i}\\ y_{c_i}\end{array}\right]---\left(1\right)$

If:

$\left\{\begin{array}{cc}{s}_x={s_x}^{\&prime;}+k*\mathrm{\&Delta;x}& k<\mathrm{\&delta;}/\mathrm{\&Delta;x}\\ s_y={s_y}^{\&prime;}+l*\mathrm{\&Delta;y}& l<\mathrm{\&delta;}/\mathrm{\&Delta;y}\\ \mathrm{\&theta;}={\mathrm{\&theta;}}^{\&prime;}+h*\mathrm{\&Delta;\&theta;}& h<\mathrm{\&beta;}/\mathrm{\&Delta;\&theta;}\end{array}\right.---\left(2\right)$

Search for to ask and make ∑ e _i ²Value k hour, l, the value of h can draw accurate positioning result (S according to (2) formula _x, S _y, θ).

2, the morpheme line fitting method based on pin as claimed in claim 1 is characterized in that, in described the 3rd step centre coordinate of each pin of chip is carried out the method that straight line fits and may further comprise the steps:

1) central point to all pins carries out the least square line match, obtains straight line L ', and its linear equation is Y=a ' * X+b ';

2) judge that whether above-mentioned central point is greater than the required minimum points N of the fitting a straight line that sets _Min, if not, then withdraw from; If, then obtain each centre coordinate put straight line L ' apart from Z _i, and judgement maximum Z wherein _kWhether greater than given threshold value Z _Max, if, then reject this centre coordinate point, then N-1 remaining centre coordinate point carried out least square fitting, when being not more than given slope error ξ, the slope differences of the straight line of the l time and the l-1 time match finishes;

3) draw precise results straight line L at last, its linear equation is Y=a*X+b.

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