CN117490571B - Double-plane mirror installation error measurement method for mirror image vision measurement system - Google Patents
Double-plane mirror installation error measurement method for mirror image vision measurement system Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/002—Measuring arrangements characterised by the use of optical techniques for measuring two or more coordinates
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/26—Measuring arrangements characterised by the use of optical techniques for measuring angles or tapers; for testing the alignment of axes
Abstract
The invention belongs to the technical field of oil and gas exploitation visual detection, and particularly relates to a method for measuring a double-plane mirror installation error of a mirror image visual measurement system. The invention provides a method for measuring the installation error of a double-plane mirror of a mirror image vision measurement system, which calibrates the incident and reflecting structure light planes in two steps, analyzes and quantifies the six-dimensional error of the double-plane mirror based on the two-step calibration, comprehensively and specifically measures the installation error of the double-plane mirror, effectively improves the measurement accuracy of the vision measurement system, and provides powerful technical support for the development of the internal (internal thread) measurement technology of an oil pipe coupling of a pipeline system. The method for measuring the mounting error of the double-plane mirror of the mirror image vision measuring system comprises the following steps: establishing a double-plane mirror installation error model; calibrating the industrial camera and the structured light respectively; judging the type of the mounting error of the double-plane mirror; and quantifying the mounting error of the biplane mirror.
Description
Technical Field
The invention belongs to the technical field of oil and gas exploitation visual detection, and particularly relates to a method for measuring a double-plane mirror installation error of a mirror image visual measurement system.
Background
The oil pipe coupling is used as a main connecting piece of an oil and gas transportation pipeline, and whether the oil pipe coupling is reliable in quality plays a critical role in guaranteeing safe operation of oil and gas transportation, so that the oil pipe coupling needs quality inspection before use. However, the internal space of the tubing coupling is limited, and the detection difficulty is high, so that higher requirements are put on a measuring system matched with the tubing coupling.
In order to solve the technical problems, a technical staff proposes a vision measurement system consisting of an industrial camera, a line laser and a double plane mirror; specifically, line lasers are transmitted to two sides of the axial section inside the oil pipe coupling (internal threads) by using a double plane mirror, so that multi-parameter integrated measurement of the inside of the oil pipe coupling (internal threads) is realized.
However, after further investigation, it was found that the mounting error of the biplane mirror is very likely to cause the line laser projected to the surface inside the tubing collar (internal thread) to shift, thereby affecting the measurement accuracy of the vision measurement system. Therefore, in order to effectively correct the pose of the double-plane mirror, technicians are required to quantize the installation error of the double-plane mirror and compensate the corresponding error, so that the detection precision of the vision measurement system is fundamentally improved.
Disclosure of Invention
The invention provides a method for measuring the installation error of a double-plane mirror of a mirror image vision measurement system, which calibrates the incident and reflecting structure light planes in two steps, analyzes and quantifies the six-dimensional error of the double-plane mirror based on the two-step calibration, comprehensively and specifically measures the installation error of the double-plane mirror, effectively improves the measurement accuracy of the vision measurement system, and provides powerful technical support for the development of the internal (internal thread) measurement technology of an oil pipe coupling of a pipeline system.
In order to solve the technical problems, the invention adopts the following technical scheme:
a method for measuring the installation error of a double-plane mirror of a mirror image vision measurement system comprises the following steps:
step (1): establishing a double-plane mirror installation error model;
step (2): calibrating the industrial camera and the structured light respectively;
step (3): judging the type of the mounting error of the double-plane mirror;
step (4): and (3) based on the determination in the step (3), obtaining the type of the mounting error of the double-plane mirror, and quantifying the mounting error of the double-plane mirror.
Preferably, the step (1) may be specifically described as:
fixed position of industrial camera, line laser and double plane mirrorSetting an intersection point between an incident structure light plane and left and right sides of the double-plane mirror as an origin, taking an axis of a line laser as a Z axis, taking an intersection edge line of the double-plane mirror as a Y axis, and establishing a coordinate system according to a right-hand rule to obtain a laser source coordinate；
Wherein the distance from the line laser light source to the intersecting edge line of the double-plane mirror isThe end point of the ridge line intersecting the biplane mirror is +.>The included angle of the double plane mirror is +.>；
The double-plane mirror has six degrees of freedom in space, namely translation along the X axis, the Y axis and the Z axis and rotation around the X axis, the Y axis and the Z axis; wherein the translational errors along the X-axis, Y-axis and Z-axis are defined as、/>、/>The rotation errors around the X-axis, Y-axis and Z-axis are defined as +.>、/>、/>。
Preferably, the process of calibrating the industrial camera in the step (2) may be specifically described as:
the method is characterized in that a Zhang's calibration method is adopted, according to standard parameter information carried on a calibration plate, internal and external parameters of an industrial camera are obtained through solving, and the specific expression of the method meets the following conditions:
formula (1);
in the formula (1) of the compound,collecting main point coordinates of an image for an industrial camera; />For the scale factors in the two axial directions of the image coordinate system, an internal reference matrix is formed>；/>For rotating matrix +.>For translation matrix, constitute the external reference matrix->；Is the three-dimensional coordinates of the object in the world coordinate system; />Pixel coordinates on an industrial camera CCD for imaging the object; />Is a scale factor.
Preferably, the process of calibrating the structured light in the step (2) may be specifically described as:
after the industrial camera is calibrated, the industrial camera is used for collecting the structured light image projected on the calibration plate, and the gray center method is adopted for extracting the line center of the structured light, so that the following conditions are satisfied:
formula (2);
in the formula (2) of the compound,is->Gray value at pixel, +.>Is the pixel point set of the area where the structured light is located, < + >>Is the extracted central coordinate of the structured light; and fitting out the structured light plane by combining with the camera calibration result to obtain the pose of the structured light plane.
Preferably, the specific process of determining the type of the mounting error of the dual-plane mirror in the step (3) includes:
obtaining normal vector of incident structural light plane according to structural light markingLeft reflecting structure light plane normal +.>Right side reflection structure light plane normal +.>Calculating vector included angle->The method comprises the following steps: />Formula (3);
if it isThen it is determined that there is a rotation error about the X-axis in the mounting of the biplane mirrorDifference or rotational error about the Z axis;
determining normal vector of incident structured light plane according to reflection theoremLeft reflecting structure light plane normal +.>Normal vector to left side plane mirror->Vector triangle relation between the two, and normal vector of incident structural light plane>Right reflecting structure light plane normal +.>Normal vector to right side mirror>The vector triangle relations between the two are respectively as follows:
， />formula (4);
according to the two-by-two perpendicular relation, calculating to obtain the direction vector of the intersecting edge line of the double-plane mirrorThe method comprises the following steps:formula (5);
calculating the direction vector of the intersecting edge line of the biplane mirrorAnd unit vector->Included angle->: if it isJudging that the rotation error around the Z axis exists in the installation of the double-plane mirror; if->And judging that the rotation error of the double plane mirror around the X axis exists in the installation.
Preferably, the specific process of determining the type of the mounting error of the dual-plane mirror in the step (3) further includes:
if it isAn included angle between the incident structure light plane and the reflecting structure light plane is no longer present, so that the installation of the double-plane mirror is eliminated that the double-plane mirror has a rotation error around an X axis or a rotation error around a Z axis;
according to the inversion method, the line laser is rotated around the axis of the line laser by a certain angle, so that the plane of the structured light is not emitted horizontally any more; at this time, the left and right side reflection structure light planes are inclined again relative to the incidence structure light plane, so as to construct a new vector triangle relationship;
combining the coordinates of a point on the intersection line of the incident structure light plane and the reflecting structure light plane to obtain a new double-plane mirror equation, and calculating the distance from the laser source of the line laser to the left and right sides of the double-plane mirrorAnd->；
If it meetsJudging that the double-plane mirror has translational error along the X axis or rotation error around the Y axis;
calculating normal vector of left and right plane mirrors、/>And unit vector->Included angle->The method comprises the steps of carrying out a first treatment on the surface of the If it meetsJudging that the double-plane mirror has translational error along the X axis; if it meets->And judging that the rotation error of the double plane mirror around the Y axis exists in the installation.
Preferably, the specific process of determining the type of the mounting error of the dual-plane mirror in the step (3) further includes: if it meetsJudging that the double-plane mirror has a translation error along the Y axis or a translation error along the Z axis;
calculating the distance from the laser source of the line laser to the biplane mirrorThe method comprises the steps of carrying out a first treatment on the surface of the If it meets->Judging that the translation error exists in the installation of the double-plane mirror along the Y axis; if it meets->And judging that the translation error along the Z axis exists in the mounting of the double-plane mirror.
Preferably, the specific process of quantifying the mounting error of the dual-plane mirror in the step (4) includes:
when the type of the error is determined to be that the double-plane mirror is installed and the translation error along the X-axis exists, the translation error along the X-axisMeasuring amountThe method comprises the following steps: />；
When the type of the error is judged to be that the double-plane mirror is installed and has a translation error along the Y axis, the translation error of the Y axis is calculatedThe method comprises the following steps: />；
Wherein,coordinates of the end points of intersecting edges of the biplane mirror, < >>Calculating the actual coordinates of the end points of the intersecting edge lines for three-dimensional reconstruction by using monocular structured light;
when the type of the error is determined to be that the double-plane mirror is installed with the translation error along the Z axis, the Z axis translation error amountThe method comprises the following steps: />；
When it is determined that the error type is that there is a rotation error about the X-axis in the double-plane mirror mounting, the X-axis rotation error amountThe method comprises the following steps: />；
When the error type is determined to be that the double-plane mirror is installed and has a rotation error around the Y-axis, the Y-axis rotation error amountThe method comprises the following steps: />；
When the error type is determined to be that the double-plane mirror is installed and has a rotation error around the Z axis, the Z axis rotation error amountThe method comprises the following steps: />；
Wherein,is the intersecting edge line direction vector of the biplane mirror, < >>Is->Is a unit vector of (a).
The invention provides a method for measuring the mounting error of a double-plane mirror of a mirror image vision measurement system, which comprises the following steps: step (1): establishing a double-plane mirror installation error model; step (2): calibrating the industrial camera and the structured light respectively; step (3): judging the type of the mounting error of the double-plane mirror; step (4): and quantifying the mounting error of the biplane mirror. Compared with the prior art, the double-plane mirror installation error measuring method with the characteristics of the steps establishes a double-plane mirror installation error model by a mode of modeling analysis and theoretical derivation, and comprehensively analyzes the mechanism of six types of double-plane mirror installation errors; on the basis, according to the physical position relation among the structured light plane, the double-plane mirror and the laser source, judging the specific type of the double-plane mirror mounting error, deducing an error calculation formula to complete quantization, and correcting the pose of the double-plane mirror and compensating the error; the measuring process is simple and clear, the feasibility is strong, the measuring precision of the inside (internal threads) of the tubing coupling of the pipeline system is improved, and an important theoretical support is provided for improving the detection level of the vision measuring system.
Drawings
The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate the invention and together with the embodiments of the invention, serve to explain the invention. In the following figures:
FIG. 1 is a schematic flow chart of a method for measuring the mounting error of a double-plane mirror of a mirror image vision measurement system;
FIG. 2 is a schematic diagram of a mirror image vision biplane mirror measurement system;
FIG. 3 (a) is a schematic diagram of an error type biplane mirror mount with translational error along the X axis;
FIG. 3 (b) is a schematic diagram of an error type biplane mirror mount with translational error along the Y-axis;
FIG. 3 (c) is a schematic diagram of an error type biplane mirror mount with translational error along the Z axis;
FIG. 3 (d) is a schematic diagram of an error type biplane mirror mount with rotational error along the X axis;
FIG. 3 (e) is a schematic diagram of an error type biplane mirror mount with rotational error along the Y axis;
FIG. 3 (f) is a schematic diagram of an error type biplane mirror mount with rotational error along the Z axis;
reference numerals: 1. an industrial camera; 2. a line laser; 3. an incident structured light plane; 4. a left reflecting structured light plane; 5. a right side reflecting structured light plane; 6. a left side plane mirror; 7. right side plane mirror.
Detailed Description
The invention provides a method for measuring the installation error of a double-plane mirror of a mirror image vision measurement system, which calibrates the incident and reflecting structure light planes in two steps, analyzes and quantifies the six-dimensional error of the double-plane mirror based on the two-step calibration, comprehensively and specifically measures the installation error of the double-plane mirror, effectively improves the measurement accuracy of the vision measurement system, and provides powerful technical support for the development of the internal (internal thread) measurement technology of an oil pipe coupling of a pipeline system.
Specifically, the invention provides a method for measuring the mounting error of a double-plane mirror of a mirror image vision measurement system, as shown in fig. 1, comprising the following steps:
step (1): and establishing a double-plane mirror installation error model.
Specifically, the step (1) may be specifically described with reference to the following:
the positions of the industrial camera, the line laser and the double-plane mirror are fixed, the intersection point between the incident structural light plane and the left side surface and the right side surface of the double-plane mirror is taken as an original point, the axis of the line laser is taken as a Z axis, the intersecting edge line of the double-plane mirror is taken as a Y axis, a coordinate system is established according to a right-hand rule, and the laser source coordinate is obtained；
Wherein the distance from the line laser light source to the intersecting edge line of the double-plane mirror isThe end point of the ridge line intersecting the biplane mirror is +.>The included angle of the double plane mirror is +.>；
The double-plane mirror has six degrees of freedom in space, namely translation along the X axis, the Y axis and the Z axis and rotation around the X axis, the Y axis and the Z axis; wherein the translational errors along the X-axis, Y-axis and Z-axis are defined as、/>、/>The rotation errors around the X-axis, Y-axis and Z-axis are defined as +.>、/>、/>。
It should be noted that, in order to facilitate understanding of the method for measuring the mounting error of the dual-plane mirror provided by the present invention, a structural diagram of a mirror-image vision dual-plane mirror measuring system is further provided herein, and the whole analysis process of the mounting error of the dual-plane mirror is analyzed in detail by combining the structural diagram. As shown in fig. 2, the mirror image vision dual-plane mirror measurement system shown in fig. 2 includes: an industrial camera 1, a line laser 2, an incident structured light plane 3, a left reflecting structured light plane 4, a right reflecting structured light plane 5, a left plane mirror 6, a right plane mirror 7.
The parameters of the above structural units can be specifically referred to as: the built mirror image vision double plane mirror measuring system selects the industrial camera 1 with resolution 1440×1080 pixels, pixel size 3.45 μm×3.45 μm and signal to noise ratio 41dB, minimum line width 50 μm and divergence angleIs provided.
According to the specific size of the biplane mirror to be measured, the relative positions of the structural units in FIG. 1 are adjusted, wherein the distance from the light source of the line laser 2 to the intersecting edge line of the biplane mirrorLaser source coordinates->Edge points of intersection of biplane mirrors +.>Included angle of biplane mirror->。
And (3) further continuing to finish the step (2) on the basis of finishing the step (1): the industrial camera 1 and the structured light are calibrated respectively.
The process of calibrating the industrial camera 1 can be specifically described as follows:
the method is characterized in that a Zhang's calibration method is adopted, according to standard parameter information carried on a calibration plate, internal and external parameters of the industrial camera 1 are obtained through solving, and the specific expression thereof meets the following conditions:
formula (1);
in the formula (1) of the compound,acquiring principal point coordinates of an image for the industrial camera 1; />For the scale factors in the two axial directions of the image coordinate system, an internal reference matrix is formed>；/>For rotating matrix +.>For translation matrix, constitute the external reference matrix->；/>Is the three-dimensional coordinates of the object in the world coordinate system; />Pixel coordinates on the industrial camera 1CCD for imaging the object; />Is a scale factor.
Specifically, in the step, a Zhang's calibration method is adopted, and the calibration process of the internal and external parameters of the industrial camera 1 is realized by combining standard parameter information carried on a calibration plate. The used calibration plate is a ceramic material solid circle calibration plate, the size reference is 10mm multiplied by 10mm, the number of solid circles is 7 multiplied by 7, the diameter of the solid circles is 0.625mm, and the space between the solid circles is 1.25mm. Finally, the reference of the internal reference matrix of the industrial camera 1 is obtained asThe external matrix is。
Then, the process of calibrating the structured light can be specifically described as:
after the calibration of the industrial camera 1 is completed, the industrial camera 1 is used for collecting the structured light image projected on the calibration plate, and the gray-scale gravity center method is adopted for extracting the line center of the structured light, so that the following conditions are satisfied:
formula (2);
in the formula (2) of the compound,is->Gray value at pixel, +.>Is the pixel point set of the area where the structured light is located, < + >>Is the extracted structured light center coordinates.
The camera calibration result is combined to further fit the two lines of the structured light into a plane, so that the pose of the structured light plane is obtained; and the positions of the incident structure light plane 3, the left reflection structure light plane 4 and the right reflection structure light plane 5 in fig. 2 are calculated respectively and used as data supports for judging the installation error types of the biplane mirrors later.
After the step (2) is finished, the steps (3) and (4) are further finished continuously. The step (3) is used for judging the type of the mounting error of the double-plane mirror; and (4) quantifying the mounting error of the double-plane mirror based on the type of the mounting error of the double-plane mirror determined in the step (3).
Specifically, since the biplane mirror has six degrees of freedom in space, translation along the X-axis, Y-axis, and Z-axis, and rotation about the X-axis, Y-axis, and Z-axis, respectively. Therefore, the determination and quantification of the installation error types of various double-plane mirrors are finally realized by combining the influence mechanisms of various types of errors on measurement. Among them are for example: rotation errors about the X-axis and rotation errors about the Z-axis can result in tilting of the reflective structure light plane; translational errors along the X-axis and rotational errors about the Y-axis result in an increase on one side and a decrease on the other side of the distance from the laser source to the biplane mirror.
Based on the analysis thought, the further detailed description of the step (3) and the step (4) can be referred as follows:
obtaining normal vector of incident structural light plane according to structural light markingLeft reflecting structure light plane normal +.>Right side reflection structure light plane normal +.>Calculating vector included angle->The method comprises the following steps: />Formula (3);
if it isIt is determined that there is a rotation error about the X-axis or a rotation error about the Z-axis in the biplane mirror mounting.
It is noted that only two errors of rotation error around the X axis or rotation error around the Z axis exist in the installation of the double-plane mirror, so that the reflection structure light plane is inclined, namely the included angle between the incidence structure light plane and the left and right reflection structure light planes is not zero, and the preliminary judgment of the installation type is realized.
On the basis, after the double-plane mirror is judged to have rotation error around X axis or Z axis, the normal vector of the incident structural light plane is determined according to the reflection theoremLeft reflecting structure light plane normal +.>Normal vector to left side plane mirror->Vector triangle relation between the two, and normal vector of incident structural light plane>Right reflecting structure light plane normal +.>Normal vector to right side mirror>The vector triangle relations between the two are respectively as follows:
，/>formula (4);
according to the two-by-two perpendicular relation, calculating to obtain the direction vector of the intersecting edge line of the double-plane mirrorThe method comprises the following steps:formula (5);
calculating the direction vector of the intersecting edge line of the biplane mirrorAnd unit vector->Included angle->: if->Judging that the rotation error around the Z axis exists in the installation of the double-plane mirror; if->And judging that the rotation error of the double plane mirror around the X axis exists in the installation.
On the other hand. If it isThe incidence structure light plane and the reflection structure light plane have no included angle, so that the rotation error around the X axis or the rotation error around the Z axis exists in the installation of the double-plane mirror is eliminated. According to the inversion method, the line laser 2 is rotated around the axis of the line laser by a certain angle, so that the structured light plane is not emitted horizontally any more; at this time, the left and right side reflection structure light planes are tilted again with respect to the incident structure light plane, thereby constructing a new vector triangle relationship.
Combining the coordinates of a point on the intersection line of the incident structure light plane and the reflection structure light plane to obtain a new double-plane mirror equation, and calculating the distance from the laser source of the line laser 2 to the left and right sides of the double-plane mirrorAnd->. If it meets->It is determined that there is a translational error along the X-axis or a rotational error about the Y-axis for the biplane mirror mounting.
It should be noted that, since the rotation error around the X-axis or the rotation error around the Z-axis is eliminated from the dual-plane mirror installation, the reflection structure light plane is no longer inclined, and the normal vector of the plane mirror cannot be determined through the vector triangle relationship. Thus, according to the inversion method, the line laser 2 is rotated about its axis by an angle such that the structured light plane is no longer emitted horizontally, thereby creating a new vector triangle relationship. Specifically, from the two-plane mirror installation error model, it is known that among six possible installation errors, only translational errors along the X-axis or rotational errors about the Y-axis can cause the distances from the laser source to the left and right side plane mirrors to be no longer equal.
On the basis, the normal vector of the left plane mirror and the right plane mirror is further calculated、/>And unit vector->Included angle->The method comprises the steps of carrying out a first treatment on the surface of the If it meets->Judging that the double-plane mirror has translational error along the X axis; if it meetsAnd judging that the rotation error of the double plane mirror around the Y axis exists in the installation.
If it meetsThen it is determined that the biplane mirror is installedTranslational errors along the Y axis or translational errors along the Z axis.
Wherein it is notable that, in the known、/>The ideal distance of the laser source of the line laser 2 from the biplane mirror +.>: i.e. < ->. According to the error model of the double-plane mirror installation, the existence of the translational error along the Y axis or the translational error along the Z axis can change the distance from the laser source to the double-plane mirror.
On the basis, the distance from the laser source of the line laser 2 to the double plane mirror is further calculatedThe method comprises the steps of carrying out a first treatment on the surface of the If it meetsJudging that the translation error exists in the installation of the double-plane mirror along the Y axis; if it meets->And judging that the translation error along the Z axis exists in the mounting of the double-plane mirror.
Thus, after the six types of installation errors are determined, the above-described errors are quantitatively analyzed.
Specifically, reference is made to fig. 3 (a) -3 (f), wherein the foregoing figures record a quantitative representation of various types of errors, in which the solid line is the actual position of the biplane mirror and the dashed line is the theoretical position of the biplane mirror.
As shown in FIG. 3 (a), when it is determined that the type of error is that there is a translational error along the X-axis in the double-plane mirror mounting, the amount of the translational error along the X-axisThe method comprises the following steps: />。
Notably, this type of error can cause the line laser 2 laser source to vary inversely with respect to the distance from the two planes of the biplane mirror. Since the biplane mirrors are symmetrically distributed, the distance from the laser source to one side of the mirror increases by the same amount as the distance from the laser source to the other side of the mirror decreases in the X-axis direction.
Substituting the correlation data to calculate and obtain the laser sourceThe distances from the left plane mirror and the right plane mirror are respectively、/>. At this time->One of two types of errors, translation along the X-axis and rotation about the Y-axis, is determined. Further calculate +.>And unit vector->Included angle->Determining the error type of the experimental double-plane mirror as translational error along the X axis, and finally obtaining the following quantification: />。
As shown in fig. 3 (b), when it is determined that the type of error is that there is a translational error along the Y-axis for the double-plane mirror mounting, the amount of the translational error along the Y-axisThe method comprises the following steps: />。
It should be noted that when the type of error is determined to be a translational error along the Y-axis in the mounting of the biplane mirror, the actual distance between the intersection edge points of the horizontal structured light plane and the biplane mirror will vary. The theoretical coordinates of the end points of intersecting edge lines of the biplane mirror are known asBecause only one intersection point exists between the structural light plane and the intersecting edge line at the moment, the endpoint coordinates cannot be calculated by directly utilizing the monocular structural light three-dimensional reconstruction, the line laser 2 is rotated around the axis of the line laser, the structural light plane is vertically projected on the intersecting edge line, and the actual coordinates of the endpoint of the intersecting edge line are calculated by utilizing the monocular structural light three-dimensional reconstruction. Substituting the related data to obtain the specific calculation, namely the laser source +.>Distance to left and right side mirrors. At this time->The type of experimental biplane mirror error is determined to be a translational error along the Y-axis.
Because the endpoint coordinates of the intersecting edge line of the biplane mirror are specifically as followsThe line laser 2 is rotated about its axis +.>Shooting an image to perform three-dimensional reconstruction to obtain the actual coordinates of the end points of the intersecting edge lines as +.>Then。
As shown in FIG. 3 (c), when it is determined that the type of error is that there is a translational error along the Z-axis for the dual-plane mirror mounting, the amount of the translational error along the Z-axisThe method comprises the following steps: />. Notably, this type of error can result in the same value of the distance change from the laser source to the left and right side mirrors. Therefore, substitution related data quantization is available, +.>。
As shown in FIG. 3 (d), when it is determined that the error type is that there is a rotation error about the X-axis in the double-plane mirror mounting, the X-axis rotation error amountThe method comprises the following steps: />. It should be noted that such errors result in a bi-plane mirror intersecting edge line direction vector +.>And unit vector->Is changed. Because the included angle of the ideal position is zero, the relative data is substituted for quantization calculation to obtain +.>。
As shown in FIG. 3 (e), when it is determined that the error type is that there is a rotation error about the Y-axis in the double-plane mirror mounting, the Y-axis rotation error amountThe method comprises the following steps: />. Notably, such errors result in left and right side mirror normal vector +.>、/>And unit vector->Is changed. Therefore, the relative data is quantitatively calculated according to the substitution of the geometric relationship, < >>。
As shown in FIG. 3 (f), when it is determined that the error type is that there is a rotation error about the Z-axis in the double-plane mirror mounting, the Z-axis rotation error amountThe method comprises the following steps: />. In particular, such errors result in a biplane crossing ridge direction vector +.>And unit vector->Since the angle of the ideal position is zero, the angle is calculated by substituting the angle into the related data>。
The invention realizes the judgment of various installation error types of the double-plane mirror and the quantification process of the installation error of the double-plane mirror.
The invention provides a method for measuring the mounting error of a double-plane mirror of a mirror image vision measurement system, which comprises the following steps: step (1): establishing a double-plane mirror installation error model; step (2): calibrating the industrial camera and the structured light respectively; step (3): judging the type of the mounting error of the double-plane mirror; step (4): and quantifying the mounting error of the biplane mirror. Compared with the prior art, the double-plane mirror installation error measuring method with the characteristics of the steps establishes a double-plane mirror installation error model by a mode of modeling analysis and theoretical derivation, and comprehensively analyzes the mechanism of six types of double-plane mirror installation errors; on the basis, according to the physical position relation among the structured light plane, the double-plane mirror and the laser source, judging the specific type of the double-plane mirror mounting error, deducing an error calculation formula to complete quantization, and correcting the pose of the double-plane mirror and compensating the error; the measuring process is simple and clear, the feasibility is strong, the measuring precision of the inside (internal threads) of the tubing coupling of the pipeline system is improved, and an important theoretical support is provided for improving the detection level of the vision measuring system.
The foregoing is merely illustrative of the present invention, and the present invention is not limited thereto, and any person skilled in the art will readily recognize that variations or substitutions are within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (4)
1. The method for measuring the mounting error of the double-plane mirror of the mirror image vision measuring system is characterized by comprising the following steps of:
step (1): establishing a double-plane mirror installation error model;
the step (1) can be specifically described as:
the positions of the industrial camera, the line laser and the double-plane mirror are fixed, the intersection point between the incident structural light plane and the left side surface and the right side surface of the double-plane mirror is taken as an original point, the axis of the line laser is taken as a Z axis, the intersecting edge line of the double-plane mirror is taken as a Y axis, and a sitting position is established according to the right hand ruleThe standard system is used for obtaining the coordinates of the laser source；
Wherein the distance from the line laser light source to the intersecting edge line of the double-plane mirror isThe end points of the intersecting edge lines of the biplane mirrors areThe included angle of the double plane mirror is +.>；
The double-plane mirror has six degrees of freedom in space, namely translation along the X axis, the Y axis and the Z axis and rotation around the X axis, the Y axis and the Z axis; wherein the translational errors along the X-axis, Y-axis and Z-axis are defined as、/>、/>The rotation errors around the X-axis, Y-axis and Z-axis are defined as +.>、/>、/>；
Step (2): calibrating the industrial camera and the structured light respectively;
the process of calibrating the industrial camera in the step (2) can be specifically described as follows:
the method is characterized in that a Zhang's calibration method is adopted, according to standard parameter information carried on a calibration plate, internal and external parameters of an industrial camera are obtained through solving, and the specific expression of the method meets the following conditions:
formula (1);
in the formula (1) of the compound,collecting main point coordinates of an image for an industrial camera; />For the scale factors in the two axial directions of the image coordinate system, an internal reference matrix is formed>；/>For rotating matrix +.>For translation matrix, constitute the external reference matrix->；Is the three-dimensional coordinates of the object in the world coordinate system; />Pixel coordinates on an industrial camera CCD for imaging the object; />Is a scale factor;
the process of calibrating the structured light in the step (2) may be specifically described as:
after the industrial camera is calibrated, the industrial camera is used for collecting the structured light image projected on the calibration plate, and the gray center method is adopted for extracting the line center of the structured light, so that the following conditions are satisfied:
formula (2);
in the formula (2) of the compound,is->Gray value at pixel, +.>Is the set of pixel points in the region where the structured light is located,is the extracted central coordinate of the structured light; fitting out a structured light plane by combining a camera calibration result to obtain the pose of the structured light plane;
step (3): judging the type of the mounting error of the double-plane mirror;
step (4): based on the step (3), judging to obtain the type of the mounting error of the double-plane mirror, and quantifying the mounting error of the double-plane mirror;
the specific process for quantifying the mounting error of the double-plane mirror in the step (4) comprises the following steps:
when the type of the error is determined to be that the double-plane mirror is installed with the translational error along the X-axis, the translational error amount of the X-axisThe method comprises the following steps:；
when the type of the error is judged to be that the double-plane mirror is installed and has a translation error along the Y axis, the translation error of the Y axis is calculatedThe method comprises the following steps:；
wherein,coordinates of the end points of intersecting edges of the biplane mirror, < >>Calculating the actual coordinates of the end points of the intersecting edge lines for three-dimensional reconstruction by using monocular structured light;
when the type of the error is determined to be that the double-plane mirror is installed with the translation error along the Z axis, the Z axis translation error amountThe method comprises the following steps:；
when it is determined that the error type is that there is a rotation error about the X-axis in the double-plane mirror mounting, the X-axis rotation error amountThe method comprises the following steps:；
when the error type is determined to be that the double-plane mirror is installed and has a rotation error around the Y-axis, the Y-axis rotation error amountThe method comprises the following steps:；
when the error type is determined to be that the double-plane mirror is installed and has a rotation error around the Z axis, the Z axis rotation error amountThe method comprises the following steps:；
wherein,is the intersecting edge line direction vector of the biplane mirror, < >>Is->Is a unit vector of (a).
2. The method for measuring the mounting error of the double-plane mirror of the mirror image vision measuring system according to claim 1, wherein the specific process for determining the type of the mounting error of the double-plane mirror in the step (3) comprises the following steps:
obtaining normal vector of incident structural light plane according to structural light markingLeft reflecting structure light plane normal +.>Right side reflection structure light plane normal +.>Calculating vector included angle->The method comprises the following steps: />Formula (3);
if it isJudging that the rotation error exists around the X axis or the rotation error exists around the Z axis in the installation of the double-plane mirror;
determining normal vector of incident structured light plane according to reflection theoremLeft reflecting structure light plane normal +.>Normal vector to left side plane mirror->Vector triangle relation between the two, and normal vector of incident structural light plane>Right reflecting structure light plane normal +.>Normal vector to right side mirror>The vector triangle relations between the two are respectively as follows: />，Formula (4);
according to the two-by-two perpendicular relation, calculating to obtain the direction vector of the intersecting edge line of the double-plane mirrorThe method comprises the following steps: />Formula (5);
calculating the direction vector of the intersecting edge line of the biplane mirrorAnd unit vector->Included angle->: if->Judging that the rotation error around the Z axis exists in the installation of the double-plane mirror; if->And judging that the rotation error of the double plane mirror around the X axis exists in the installation.
3. The method for measuring the mounting error of the double-plane mirror of the mirror image vision measuring system according to claim 2, wherein the specific process of determining the type of the mounting error of the double-plane mirror in the step (3) further comprises:
if it isAn included angle between the incident structure light plane and the reflecting structure light plane is no longer present, so that the installation of the double-plane mirror is eliminated that the double-plane mirror has a rotation error around an X axis or a rotation error around a Z axis;
according to the inversion method, the line laser is rotated around the axis of the line laser by a certain angle, so that the plane of the structured light is not emitted horizontally any more; at this time, the left and right side reflection structure light planes are inclined again relative to the incidence structure light plane, so as to construct a new vector triangle relationship;
combining the coordinates of a point on the intersection line of the incident structure light plane and the reflecting structure light plane to obtain a new double-plane mirror equation, and calculating the distance from the laser source of the line laser to the left and right sides of the double-plane mirrorAnd->；
If it meetsJudging that the double-plane mirror has translational error along the X axis or rotation error around the Y axis;
calculating normal vector of left and right plane mirrors、/>And unit vector->Included angle->The method comprises the steps of carrying out a first treatment on the surface of the If it meets->Judging that the double-plane mirror has translational error along the X axis; if it meets->And judging that the rotation error of the double plane mirror around the Y axis exists in the installation.
4. The method for measuring the mounting error of the double-plane mirror of the mirror image vision measuring system according to claim 3, wherein the specific process of determining the type of the mounting error of the double-plane mirror in the step (3) further comprises: if it meetsJudging that the double-plane mirror has a translation error along the Y axis or a translation error along the Z axis;
calculating the distance from the laser source of the line laser to the biplane mirrorThe method comprises the steps of carrying out a first treatment on the surface of the If it meets->Judging that the translation error exists in the installation of the double-plane mirror along the Y axis; if it meets->And judging that the translation error along the Z axis exists in the mounting of the double-plane mirror.
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