CN1664492A - Method for accurately measuring length of a work piece by double camera digital imaging - Google Patents
Method for accurately measuring length of a work piece by double camera digital imaging Download PDFInfo
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- CN1664492A CN1664492A CN 200510020591 CN200510020591A CN1664492A CN 1664492 A CN1664492 A CN 1664492A CN 200510020591 CN200510020591 CN 200510020591 CN 200510020591 A CN200510020591 A CN 200510020591A CN 1664492 A CN1664492 A CN 1664492A
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Abstract
The invention provides a method for measuring the length of the work-piece precisely by the double-cameras digital imaging, which comprises the following steps: a) setting the work-piece between two measuring sides of the gage, the axis of the work-piece is vertical to the measuring sides; b) setting two digital cameras and two negative light sources on each side of the axis individually, and the cameras are connected with the image processing device, c) shooting the images which is projected to the negative light sources using two digital cameras, the images are corresponding with the distance from the end-face of the work-piece to the measuring surface; d) computing the distances of two end-faces to the corresponding measuring surfaces through the digital image processing technique, and converting the length. The measured value has no relation to the end-face diameter, and cannot be affected when the axis deviating the digital camera or source. The image has small size and dense pixel distribution, and the distance of the pixel is mall, so the value is precise.
Description
Technical field
The invention belongs to noncontact length detection technique field, specifically, relate to a kind of method of on the automatic high speed detection line, using double camera digital imagery precision measurement Workpiece length.
Background technology
At present, on automatic inspection line, high speed and precision to picture straight pin and so on Workpiece length detects, can adopt the digital imagery length detecting method, promptly be placed on the both sides of axis of workpiece respectively, photograph the projection image of workpiece on backlight with digital camera with a planar array type CCD digital camera and backlight.Because of planar array type CCD is made up of pixel (photosensitive NP knot) matrix, during shooting, the distribution of illumination is become the distribution of pixel electric weight, the gray-scale value of the electric weight represent pixel of pixel, form digital picture through mould/number conversion again, through transmission, storage and Digital Image Processing, calculate the length value of workpiece by image processing apparatus, and make comparisons with the standard workpiece length value and judge the whether qualified of Workpiece length.Its shortcoming is: measured value is relevant with the end face diameter of the large and small end of workpiece, when workpiece axle center alignment camera or backlight skew, the Workpiece length value of measuring is with bigger than normal or less than normal, influential to the length of measuring workpiece, in addition, because the projected image breadth that digital camera is photographed is big, the pixel distribution in the unit length is less, pel spacing makes the precision resolution of measured value on the low side from greatly.
Summary of the invention
It is irrelevant to the purpose of this invention is to provide a kind of measured value and workpiece both ends of the surface diameter, and axis of workpiece does not have influence to measurement result when digital camera or backlight skew, measures the high method with double camera digital imagery precision measurement Workpiece length of precision.
For achieving the above object, the method with digital camera precision measurement Workpiece length provided by the invention comprises:
(1), workpiece is placed between two measurement faces of gauge, the measured workpiece axis is vertical with gauge measurement face, and be respectively arranged with digital camera and backlight in the both sides of axis of workpiece, one of them digital camera is in a side of axis of workpiece, another digital camera is at the opposite side of axis of workpiece, each digital camera all has a backlight corresponding with it, and digital camera links to each other with image processing apparatus;
(2), two digital cameras are photographed between corresponding workpiece end face and the gauge measurement face image apart from projection on corresponding backlight respectively;
(3) above-mentioned projected image transfers to image processing apparatus, calculates distance value between workpiece both ends of the surface and the corresponding gauge two measurement faces by image processing apparatus utilization digital image processing techniques;
(4), image processing apparatus deducts above-mentioned two distance value sums with the length between gauge two measurement faces and calculates Workpiece length, and itself and standard workpiece length made comparisons, and according to the error range that allows, judges whether Workpiece length is qualified.
Described gauge two is measured on the axial line that is centered close to workpiece of face; The digital camera optical center overlaps with corresponding workpiece end face to the vertical line of corresponding backlight; Two digital cameras equate that with the distance of workpiece axial line two backlights equate with the distance of workpiece axial line.
Owing to adopt two digital cameras respectively the both ends of the surface of workpiece to be carried out the projection shooting with the distance between the corresponding gauge measurement face among the present invention in the both sides of axis of workpiece, the image form length of side need be greater than Workpiece length, only need to the distance between the corresponding gauge measurement face greater than workpiece end face, then the distance between the projected image neighbor will be littler, when digital picture is handled, the utilization interpolation process method is surveyed long resolution and can be reached very high precision.The length of gauge is certain, and the length of gauge deducts above-mentioned two apart from sum, is the measured value of Workpiece length, makes measured value almost irrelevant with the diameter of both ends of the surface; When workpiece axle center alignment digital camera or backlight skew, (little) bigger than normal amount of two digital camera measured values is with the value contrary sign, and finally the length measurment value to workpiece does not influence.Adopt such scheme, measure the method for Workpiece length with traditional single digital camera and compare, have following remarkable result:
(1), the diameter of measured value and workpiece both ends of the surface is irrelevant;
(2), during the skew of workpiece axle center alignment digital camera or backlight, to the not influence of length of measuring workpiece;
(3), the image form photographed of digital camera is little, the pixel distribution in the unit length is more, pel spacing is from little, measured value precision resolution height.
Description of drawings
Fig. 1 is the embodiment process flow diagram of the inventive method;
Fig. 2 is that traditional single digital camera is surveyed rectangular ratio juris figure;
Fig. 3 is the schematic diagram of the inventive method;
Fig. 4 is the arrangement synoptic diagram of the inventive method the best.
Embodiment
The present invention is described in further detail below in conjunction with drawings and Examples:
Method with double camera digital imagery precision measurement Workpiece length provided by the invention, be utilization planar array type CCD imaging, during shooting, the distribution of illumination become the distribution of pixel electric weight, the gray-scale value of pixel electric weight represent pixel forms digital picture through mould/number conversion again.Through transmission, store and handle and obtain length value to be measured, below in conjunction with accompanying drawing 1, a kind of the length of the workpiece 1 of small end face and large end face is arranged is example to measure on automatic inspection line, it is as follows that its step is described in detail in detail:
(1), workpiece 1 is placed between two measurement faces of semi-circular gauge 2, measured workpiece 1 axis is vertical with gauge 2 measurement faces, and be respectively arranged with digital camera and backlight in the both sides of workpiece 1 axis, one of them digital camera 3 is in a side of workpiece 1 axis, another digital camera 4 is at the opposite side of workpiece 1 axis, digital camera 3 has backlight 5 corresponding with it with backlight 6 respectively with digital camera 4, and digital camera 3 all links to each other with image processing apparatus 7 with digital camera 4;
(2), digital camera 3 and digital camera 4 are photographed between corresponding 1 two end faces of workpiece and the gauge 2 measurement faces image apart from projection on corresponding backlight 5 and backlight 6 respectively;
(3) above-mentioned projected image transfers to image processing apparatus 7, calculates distance value between 2 liang of measurement faces of workpiece 1 both ends of the surface and corresponding gauge by image processing apparatus 7 utilization digital image processing techniques;
(4), image processing apparatus 7 deducts the length that above-mentioned two distance value sums calculate workpiece 1 with the length between 2 liang of measurement faces of gauge, and itself and standard workpiece length made comparisons, and according to the error range that allows, judges whether Workpiece length is qualified.
Below in conjunction with Fig. 2, Fig. 3 and relevant formula, the measuring accuracy that traditional single digital camera is surveyed rectangular method and the inventive method compares analysis (supposing that the measuring accuracy that workpiece 1 requires is 10 microns):
(1), traditional single digital camera is surveyed rectangular method analysis of measurement errors:
As shown in Figure 2, workpiece 1 places between digital camera and the backlight.If the projected length of workpiece 1 on backlight is L and forms (is the separatrix to the vertical line of backlight with the digital camera optical center) by two sections LR, Lr; The length of workpiece 1 is l, and by two sections l
R, l
rForm (is the separatrix to the vertical line of backlight with the digital camera optical center); The radius of workpiece 1 small end face is r, and the large end face radius is R; Workpiece 1 axial line is h to the distance of backlight, and digital camera is H to the distance of backlight.
The long L=LR+Lr of workpiece 1 projection
Because of the long L of projection greater than the long l of workpiece, the order
K is a projection coefficient
L=k * L then
In actual measurement,, kL=l is got final product to the k assignment.
When tradition single digital camera methods was surveyed length, the image form length of side should be greater than Workpiece length, and for example workpiece 1 length is 30 millimeters, and then getting image form is 51.2 * 51.2 millimeters, supposes that pixel is 512 * 512, and then the neighbor distance is 0.1 millimeter.When Flame Image Process, use interpolation processing again, calculate in four neighbors certain any gray-scale value, survey long resolution (display precision) and can reach 0.01 millimeter.
With master body digital camera parameter is set earlier, set the k value simultaneously.
During actual measurement, workpiece 1 size has been compared some changes with exemplar, and also there is change the measuring position of workpiece 1, and k will change and be that k ', actual (tube) length are k ' * L, but measured value still press the calculating of k value, so traditional single digital camera is surveyed the measuring error of rectangular method:
Δ＝(k-k′)L
Can get the long error of survey of workpiece 1 with above-mentioned Error Calculation formula.
Example: H=210 l=25 h=35 R=3 r=1 l
r=12.5 l
R=12.5 o'clock:
R=1 ± 0.1 Δ=± 0.0071 error is less than License Value
R=3 ± 0.1 Δ=± 0.0073 error is less than License Value
L=25 ± 0.2 Δ=± 0.0012 error is very little
It is more that h=35 ± 0.1 Δ=± 0.0145 error exceeds License Value
l
r=12.5 ± 0.2 Δ=± 0.0023 error is very little
During workpiece 1 axis axial dipole field ± 0.2 millimeter, survey long error only ± 0.0023 millimeter.
(2), the inventive method analysis of measurement errors:
As shown in Figure 3, the length of establishing workpiece 1 is l, and the distance between 2 liang of measurement faces of gauge is L, and the radius of workpiece 1 small end face is r, and the radius of large end face is R, and 2 liang of half height of measuring face of gauge are h
3 Digital camera 3 is H to the distance of backlight 5
1, digital camera 4 is H to the distance of backlight 6
2, workpiece 1 and gauge 2 concentrics, workpiece 1 axial line is h to the distance of backlight 5
1, be h to the distance of backlight 6
2 Digital camera 3 optical centers are l to backlight 5 vertical lines with distance between corresponding gauge 2 measurement faces
13, and the distance between workpiece 1 small end face is l
1r, digital camera 4 optical centers are l to backlight 6 vertical lines with distance between corresponding gauge 2 measurement faces
23, and the distance between workpiece 1 large end face is l
2R, the projected length of distance on backlight 5 and backlight 6 between gauge 2 measurement faces and workpiece 1 end face, wherein the section near gauge 2 measurement faces is respectively L
13And L
23(is the separatrix to the vertical line of backlight with the digital camera optical center) is respectively L near the section of workpiece 1 end face
1rAnd L
2R(is the separatrix to the vertical line of backlight with the digital camera optical center), the length l of workpiece 1 be the length between 2 liang of measurement faces of gauge deduct distance between workpiece 1 both ends of the surface and the gauge 2 corresponding two measurement faces and, promptly
l＝L-(l
1r+l
13)-(l
2R+l
23)
Make projection coefficient
l＝L-k
1(L
1r+L
13)-k
2(L
2R+L
23)
If 3 millimeters of the image form length of sides, then getting image form is 5.12 * 5.12 millimeters, supposes that pixel is 512 * 512, and then the neighbor distance is 0.01 millimeter.When Flame Image Process, use interpolation processing again, survey long resolution (display precision) and can reach 0.001 millimeter.With master body the parameter of digital camera 3 and digital camera 4 is set earlier.Set k simultaneously
1, k
2Value.
During actual measurement, workpiece 1 size has been compared some changes with exemplar, and also there are change, k in the measuring position of workpiece 1
1, k
2To change and be k
1', k
2', actual (tube) length is k ' * L, but measured value is still pressed the calculating of k value, so the inventive method measuring error:
Δ＝Δ
1+Δ
2＝(k
1-k
1′)(L
1r+L
13)+(k
2-k
2′)(L
2R+L
23)
The workpiece size relevant with measuring error is the length l of workpiece 1, large end face diameter R, small end face diameter r.
Can obtain the long error of survey of workpiece 1 with above-mentioned Error Calculation formula.
Example: L=27 l=25 H=75 h=35 R=3 r=1 l
r=0.5 l
R=0.5 o'clock:
R=1 ± 0.1 Δ=± 0.0012 error is very little
R=3 ± 0.1 Δ=± 0.0011 error is very little
L=25 ± 0.2 Δ=± 0.0020 error is very little
H=35 ± 0.1 Δ=± 0.0000 error is zero
l
r=0.5 ± 0.1 Δ=± 0.0055 error is less than License Value
From above analytical calculation data, can obtain as drawing a conclusion:
A, workpiece 1 small end face diameter r change ± 0.05, large end face diameter R change ± 0.05 can be ignored all less than 4 microns with length change ± 0.20 measuring error that causes, the long error of the survey of classic method and the inventive method;
B, workpiece 1 axis are to digital camera or ± 0.1 millimeter measuring error that causes of backlight skew, and it is 14.5 microns that traditional single digital camera is surveyed rectangular method, surpasses measuring accuracy and requires more.And in the inventive method because Δ
1With Δ
2Only 0.1 micron of offset result, error can be ignored, and therefore workpiece 1 axis height and the positioning accuracy request to measuring system is not high;
The measuring error that c, workpiece 1 axis shaft cause to shift in position ± 0.1, it is less that traditional single digital camera is surveyed rectangular method, and the inventive method is about 5.5 microns, still less than License Value;
D, the measuring error that causes when above-mentioned Several Parameters changes simultaneously, the inventive method are 4.7 microns;
E, the inventive method survey when long, and image form is less, and the neighbor distance is 0.01 millimeter, survey long resolution (display precision) and can reach 0.001 millimeter, and traditional single digital camera are surveyed rectangular method resolution and only are 0.01 millimeter;
F, survey rectangular method Error Calculation result relatively with traditional single digital camera, every error of the inventive method is less.
Fig. 4 is the arrangement of the inventive method the best, on the axial line that is centered close to workpiece 1 of 2 liang of measurements of gauge face, digital camera 3 and digital camera 4 optical centers overlap with corresponding workpiece 1 both ends of the surface respectively to the vertical line of corresponding backlight 5 and backlight 6, two digital cameras 3 and 4 equate with the distance of workpiece axial line, two backlights 5 and 6 also equate with the distance of workpiece 1 axial line, arrange like this make workpiece 1 big small end face to measurement result without any influence, and simplify and calculate, improve the precision of measurement.
Claims (2)
1, a kind of method with double camera digital imagery precision measurement Workpiece length is characterized in that comprising:
(1), workpiece is placed between two measurement faces of gauge, the measured workpiece axis is vertical with gauge measurement face, and be respectively arranged with digital camera and backlight in the both sides of axis of workpiece, one of them digital camera is in a side of axis of workpiece, another digital camera is at the opposite side of axis of workpiece, each digital camera all has a backlight corresponding with it, and digital camera links to each other with image processing apparatus;
(2), two digital cameras are photographed between corresponding workpiece end face and the gauge measurement face image apart from projection on corresponding backlight respectively;
(3) above-mentioned projected image transfers to image processing apparatus, calculates distance value between workpiece both ends of the surface and the corresponding gauge two measurement faces by image processing apparatus utilization digital image processing techniques;
(4), image processing apparatus deducts above-mentioned two distance value sums with the length between gauge two measurement faces and calculates Workpiece length, and itself and standard workpiece length made comparisons, and according to the error range that allows, judges whether Workpiece length is qualified.
2, a kind of method according to claim 1 with double camera digital imagery precision measurement Workpiece length, it is characterized in that: gauge two is measured on the axial line that is centered close to workpiece of face; The digital camera optical center overlaps with corresponding workpiece end face to the vertical line of corresponding backlight; Two digital cameras equate that with the distance of workpiece axial line two backlights equate with the distance of workpiece axial line.
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| Application Number | Priority Date | Filing Date | Title |
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| CN 200510020591 CN1291214C (en) | 2005-03-24 | 2005-03-24 | Method for accurately measuring length of a work piece by double camera digital imaging |
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|---|---|---|---|
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| CN1291214C CN1291214C (en) | 2006-12-20 |
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Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100432621C (en) * | 2006-12-01 | 2008-11-12 | 上海电缆研究所 | Method for precision measuring dimension of object using optical imaging measuring system |
| CN101539406B (en) * | 2009-05-06 | 2011-04-20 | 北京科技大学 | Method and device for measuring shape and size of workpiece with high-temperature end and low-temperature end on line |
| CN101685002B (en) * | 2008-09-25 | 2011-07-06 | 比亚迪股份有限公司 | Method of length detection and system thereof |
| CN103217128A (en) * | 2013-04-22 | 2013-07-24 | 钟兴辉 | Twin-lens measuring system |
| CN103913119A (en) * | 2013-01-09 | 2014-07-09 | 扬州中誉数控机械有限公司 | Workpiece length online measuring system and method |
| CN104864808A (en) * | 2015-04-15 | 2015-08-26 | 浙江工业大学 | Method for precisely measuring size of workpiece along transmission direction in rolling transmission process |
| CN106152946A (en) * | 2015-03-31 | 2016-11-23 | 酷派软件技术（深圳）有限公司 | A kind of method of Measuring Object length and terminal |
| CN108050944A (en) * | 2018-01-05 | 2018-05-18 | 湖北汽车工业学院 | A kind of automobile tube beam measuring device and method based on image procossing |
-
2005
- 2005-03-24 CN CN 200510020591 patent/CN1291214C/en not_active Expired - Fee Related
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100432621C (en) * | 2006-12-01 | 2008-11-12 | 上海电缆研究所 | Method for precision measuring dimension of object using optical imaging measuring system |
| CN101685002B (en) * | 2008-09-25 | 2011-07-06 | 比亚迪股份有限公司 | Method of length detection and system thereof |
| CN101539406B (en) * | 2009-05-06 | 2011-04-20 | 北京科技大学 | Method and device for measuring shape and size of workpiece with high-temperature end and low-temperature end on line |
| CN103913119A (en) * | 2013-01-09 | 2014-07-09 | 扬州中誉数控机械有限公司 | Workpiece length online measuring system and method |
| CN103217128A (en) * | 2013-04-22 | 2013-07-24 | 钟兴辉 | Twin-lens measuring system |
| CN106152946A (en) * | 2015-03-31 | 2016-11-23 | 酷派软件技术（深圳）有限公司 | A kind of method of Measuring Object length and terminal |
| CN106152946B (en) * | 2015-03-31 | 2019-08-02 | 酷派软件技术（深圳）有限公司 | A kind of method and terminal measuring object length |
| CN104864808A (en) * | 2015-04-15 | 2015-08-26 | 浙江工业大学 | Method for precisely measuring size of workpiece along transmission direction in rolling transmission process |
| CN108050944A (en) * | 2018-01-05 | 2018-05-18 | 湖北汽车工业学院 | A kind of automobile tube beam measuring device and method based on image procossing |
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| CN1291214C (en) | 2006-12-20 |
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