CN108489401B - Split type calibration target, calibration device with target and calibration method of calibration device - Google Patents
Split type calibration target, calibration device with target and calibration method of calibration device Download PDFInfo
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- CN108489401B CN108489401B CN201810563230.7A CN201810563230A CN108489401B CN 108489401 B CN108489401 B CN 108489401B CN 201810563230 A CN201810563230 A CN 201810563230A CN 108489401 B CN108489401 B CN 108489401B
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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
- G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
- G01B11/03—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness by measuring coordinates of points
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Abstract
The invention provides a split type calibration target, which is matched with a target mirror to be used as a measurement target when a laser tracker is used for calibrating a space distance indication error of a laser scanner, and comprises the following steps: a target holder; the target mirror supporting component is provided with a taper shank, a connecting piece arranged on the taper shank and a target mirror seat arranged on the connecting piece and used for being connected with a target mirror through magnetic adsorption; and the target ball assembly is provided with a ball side taper shank, a three-dimensional adjusting mechanism arranged on the ball side taper shank and a target ball arranged on the three-dimensional adjusting mechanism, wherein the taper shank and the ball side taper shank are Morse taper shanks which have the same size and tolerance, the taper tips are downwards arranged, the target seat is provided with Morse taper sleeves, the taper tips of the Morse taper sleeves are downwards, the opening is upwards, and the Morse taper sleeves are matched with the taper shanks and the ball side taper shanks. The invention also provides a calibration device with the split type calibration target and a method for calibrating the laser scanner by using the calibration device.
Description
Technical Field
The invention relates to a calibration target, in particular to a split type calibration target, a calibration device with the split type calibration target and a calibration method for calibrating a laser scanner by using the calibration device.
Background
Along with the development of scientific technology, especially the major projects such as large aircraft manufacturing, the demands for digital accurate positioning and assembly, accurate three-dimensional measurement of large parts, product quality monitoring and reverse engineering are increasing, and the application of novel space coordinate measuring instruments such as laser trackers, laser radars, laser three-dimensional scanners, iGPS and the like is becoming wider. The space ranging precision of the instrument is a precondition of the processing precision of large parts and the assembly precision of large equipment such as automobiles, airplanes, fans and the like.
The appearance and development of three-dimensional laser measurement technology provides a brand new technical means for acquiring space three-dimensional information. The ground three-dimensional laser scanner is widely applied to the fields of surveying and mapping, archaeology, construction, forestry and the like as a high-efficiency, accurate and reliable space surveying and mapping technology. The measuring mode is similar to a laser tracker, but the non-contact active measuring mode is adopted, so that three-dimensional space coordinates of a large number of sampling points on the surface of an object can be rapidly obtained, and a target mirror is not required to be used in the measuring process. In recent years, with the development of three-dimensional laser scanning technology and the improvement of precision requirements, the requirements for calibration, performance verification and measurement traceability are also increasing.
The calibration of the laser scanner is mainly divided into radial repeatability, target repeatability, radial distance indication error, spatial distance indication error and other items. The radial distance indication error refers to the difference between the measured value and the reference value relative to the distance along the measuring axis. Radial repeatability refers to the repeatability of radial absolute distance measurements for the same fixed target. The spatial distance indication error value is used for measuring targets with different spatial distances and orientations, and the difference between the measured value of the relative distance and the reference value is measured. Target repeatability refers to the repeatability of measured values of the center coordinates (points) of the target. Wherein, radial repeatability and target repeatability can be realized by only one single target. Calibration of the radial distance indication error can be achieved with a long guide rail baseline, a laser interferometer, and a target on a mating sliding table. The calibration of the space distance indication error is relatively complex, a plurality of targets are required to be fixed on a rigid structure, and a higher-precision instrument is adopted to calibrate the center distance (sphere center distance) between any two targets as a reference value of the space distance, so that the calibration of the center distance (sphere center distance) of the targets fixed on the rigid structure is an important link for establishing the laser scanner space distance indication error calibration device.
Because of the symmetry of the spherical target in all directions, the spherical target is widely used in measurement of various three-dimensional laser scanners so as to realize conversion of laser scanning point cloud data and unification of measurement coordinate systems of different station laser scanners. The spherical target of the laser scanner needs to have diffuse reflection characteristic, is generally a matte surface, and the sphere center cannot be directly measured, and the coordinates of the sphere center are generally obtained by adopting an indirect measurement method.
The most commonly used method is to use a target lens of a laser tracker to move on a spherical target, and fit a spherical center through measurement data of the laser tracker. However, by using a laser tracker to measure the fitting method, the error of the center of the ball is influenced by the shape of the surface of the ball, the number of the measurement points is large, and the time and the labor are wasted. In addition, in order to realize the unification of the coordinates of the laser tracker and the laser scanner, so that the laser tracker with a higher spatial ranging precision level by one order of magnitude can be used for evaluating the performance index of the laser scanner, and how to make targets of the laser tracker and the laser scanner concentric is a key point. The National Institute of Standards and Technology (NIST) adopts an integrated target, and places a pyramid lens in the center of an aluminum hemisphere, so that the simultaneous application of a total station and a laser scanner is realized. However, in the method, the sphericity precision of the hemisphere is not very high, and in the second, the existing domestic processing technology is difficult to ensure that the cone mirror and the sphere center of the hemisphere have higher concentricity.
Disclosure of Invention
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a split type calibration target, a calibration device having the split type calibration target, and a method for calibrating a laser scanner using the calibration device.
The invention provides a split type calibration target, which is matched with a target mirror to be used as a measurement target when a laser tracker is used for calibrating a space distance indication error of a laser scanner, and has the characteristics that: a target holder; the target mirror supporting component is provided with a taper shank, a connecting piece arranged on the taper shank and a target mirror seat arranged on the connecting piece and used for being connected with a target mirror through magnetic adsorption; and the target ball assembly is provided with a ball side taper shank, a three-dimensional adjusting mechanism arranged on the ball side taper shank and a target ball arranged on the three-dimensional adjusting mechanism, wherein the taper shank and the ball side taper shank are Morse taper shanks which have the same size and tolerance, the taper tips are downwards arranged, the target seat is provided with Morse taper sleeves, the taper tips of the Morse taper sleeves are downwards, the opening is upwards, and the Morse taper sleeves are matched with the taper shanks and the ball side taper shanks.
In the split calibration target provided by the invention, the split calibration target can also have the following characteristics: wherein, three-dimensional adjustment mechanism is disjunctor three-dimensional translation platform.
In the split calibration target provided by the invention, the split calibration target can also have the following characteristics: the split type calibration target further comprises a nut, wherein the nut is matched with the external thread and used for rotating upwards and jacking the taper shank and the ball side taper shank.
The invention also provides a calibration device for calibrating the error of the spatial distance indication of a laser scanner, which is characterized by comprising: a target mirror; a first split calibration target having a first backing plate, a first target mirror support assembly, and a first target ball assembly having a first target ball; a second split calibration target having a second backing plate, a second target mirror support assembly, and a second target ball assembly having a second target ball; a length provider for carrying a first split calibration target and a second split calibration target; and the laser tracker is used for emitting laser and measuring coordinates of the target lens when the target lens is respectively positioned on the first target lens bearing assembly and the second target lens bearing assembly, and obtaining a distance value between the two coordinates as a standard distance value, wherein the first target ball and the second target ball are used as measuring targets of the laser scanner and are used for the laser scanner to scan to obtain a sphere center distance value between the first target ball and the second target ball, so that a difference value between the sphere center distance value and the standard distance value is calculated to obtain a space distance indication error of the laser scanner, and the first split calibration target and the second split calibration target are the split calibration targets.
In the calibration device provided by the invention, the device can also have the following characteristics: wherein the outer surface of the target ball is a matte spherical surface.
The invention also provides a calibration method for calibrating the laser scanner by using the calibration device, which is characterized by comprising the following steps: firstly, carrying out concentricity correction on a target mirror, a first target ball and a second target ball of a calibrating device by utilizing a three-coordinate measuring machine; step two, the first target seat and the second target seat are respectively arranged on the length providing piece; step three, respectively installing the first target mirror supporting component and the second target mirror supporting component on the first target seat and the second target seat; step four, placing the target lens on a first target lens seat of a first target lens bearing assembly; measuring by using a laser tracker to obtain a first target coordinate value of the target lens; step six, the target lens is taken off from the first target lens supporting component and placed on a second target lens seat of the second target lens supporting component; measuring again by using a laser tracker to obtain a second target coordinate value of the target lens; step eight, obtaining the center distance of two sets of split calibration targets as a standard distance value according to the first target coordinate value and the second target coordinate value; step nine, the first target mirror supporting component and the second target mirror supporting component are removed, and step ten, the first target ball component and the second target ball component are respectively installed on the first target seat and the second target seat; step eleven, scanning by using a laser scanner to obtain a sphere center distance value of a first target sphere of the first target sphere assembly and a second target sphere of the second target sphere assembly; and step twelve, calculating a difference value between the sphere center distance value and the standard distance value, wherein the difference value is the error of the space distance indication value of the laser scanner.
The calibration method provided by the invention can also have the following characteristics: in the first step, the correction of concentricity of the target lens and the first target ball comprises the following steps: step 1-1, fixedly arranging a first target mirror supporting component on a first target seat, and then fixing the first target seat on a workbench of a three-coordinate measuring machine; step 1-2, placing the target lens on a first target lens supporting component, and step 1-3, measuring coordinates of 5 points on the spherical outer contour of the target lens by using a three-coordinate measuring machine; step 1-4, fitting to obtain the center coordinate (x) of the spherical outer contour of the target lens according to the coordinates of 5 points on the spherical outer contour of the target lens measured in step 1-3 j ，y j ，z j ) The method comprises the steps of carrying out a first treatment on the surface of the Step 1-5, keeping the target holder fixed on the workbench of the three-coordinate measuring machineRemoving the first target support assembly without changing its position; step 1-6, mounting the first target ball assembly on a first target seat, and measuring coordinates of 5 points on the outer contour of the first target ball assembly by using a three-coordinate measuring machine; step 1-7, fitting to obtain the center coordinate (x) of the first target sphere according to the coordinates of 5 points on the outer contour of the first target sphere measured in step 1-6 q ，y q ，z q ) The method comprises the steps of carrying out a first treatment on the surface of the Step 1-8, calculating the deviation value of the center coordinate of the target lens and the center coordinate of the first target ball according to the following steps, wherein the deviation value is delta x ＝x q -x j ，△ y ＝y q -y j ，△ z ＝z q -z j The method comprises the steps of carrying out a first treatment on the surface of the Step 1-9, adjusting a first three-dimensional adjusting mechanism in the target ball assembly according to the deviation value to enable the deviation value to be equal x 、△ y 、△ z Are all smaller than 20 mu m; step 1-10, when the deviation value is delta x 、△ y 、△ z And when the two diameters are smaller than 20 mu m, locking the first three-dimensional adjusting mechanism to finish the correction of concentricity of the target lens and the first target ball.
The calibration method provided by the invention can also have the following characteristics: the step of correcting the concentricity of the target lens and the second target ball adopts the step of correcting the concentricity of the target lens and the first target ball.
The invention also provides a calibration device, which is characterized by comprising: a target mirror; at least three split calibration targets, each split calibration target having a target holder, a target mirror support assembly, and a target ball assembly having a target ball; a length provider for carrying a split calibration target; and the laser tracker is used for measuring the center coordinates of the target mirror when the target mirror is positioned on any one target mirror supporting component, obtaining the distance value between any two target mirror supporting components corresponding to any two center coordinates according to any two center coordinates to serve as a standard distance value, and obtaining the space distance indication error of the laser scanner according to the difference value of the standard distance value and the spherical center distance value between the corresponding two target balls, wherein the split type calibration target in the split type calibration targets is obtained.
Effects and effects of the invention
According to the split calibration target, because the taper shank and the ball side taper shank are Morse taper shanks with the same size and tolerance, and the Morse taper sleeve on the target seat is matched with the Morse taper shank, the target mirror supporting component and the target ball component of the split calibration target can accurately fall into the Morse taper sleeve of the target seat through the Morse taper shanks, thereby providing accurate positioning and high repeatability precision.
According to the calibration device disclosed by the invention, the target lens is used as a target of the laser tracker, the target lens supporting components of the two split calibration targets provide coordinate positions of the target lens for the laser tracker to measure to obtain a standard distance value, the two target balls are used for the laser scanner to measure a ball center distance value, and the difference between the ball center distance value and the standard distance value is calculated to obtain a space distance indication error of the laser scanner.
According to the method for calibrating the laser scanner by using the calibrating device, concentricity correction is firstly carried out on the target lens, the first target ball and the second target ball respectively, the laser scanner can be calibrated by directly using the laser tracker, and the time and labor consuming way of fitting the center of sphere by stepping the point of the target lens of the laser tracker on the target ball of the scanner is avoided. And the concentricity of the target mirror and the target ball can be ensured, so that the laser tracker is utilized to calibrate the laser scanner with higher accuracy.
Drawings
FIG. 1 is a schematic diagram of a calibration device in an embodiment of the invention;
FIG. 2 is a schematic structural diagram of a split calibration target in an embodiment of the invention.
Detailed Description
In order to make the technical means, creation characteristics, achievement purposes and effects achieved by the present invention easy to understand, the split calibration target, the calibration device with the split calibration target and the calibration method for calibrating the laser scanner by using the calibration device of the present invention are specifically described below with reference to the accompanying drawings and embodiments.
Fig. 1 is a schematic structural view of a calibration device according to an embodiment of the present invention.
As shown in fig. 1, the calibration device 100 is used for measuring the error of the spatial distance indication of the laser scanner, and includes a first split calibration target 10, a second split calibration target 20, a target lens 30, a length connector 40, and a laser tracker (not shown). The first split calibration target 10 has the same structure as the second split calibration target 20, and the first split calibration target 10 will be described in detail as an example.
FIG. 2 is a schematic structural diagram of a split calibration target in an embodiment of the invention.
As shown in fig. 2, the first split calibration target 10 is used in cooperation with the target 30 as a measurement target in calibrating a spatial distance indication error of a laser scanner using a laser tracker, and includes a first backing plate 11, a first target backing plate assembly 12, a first target ball assembly 13, and a nut 14.
As shown in fig. 2, the upper end of the first target seat 11 is provided with a morse taper sleeve 111 with a downward taper and an upward opening, and the outer side surface of the first target seat 11, which is positioned at the opening of the morse taper sleeve 111, is provided with an external thread extending vertically.
The nut 14 mates with the external threads of the first backing plate 11 and allows the user to rotate the nut 14 upwardly to facilitate removal of the first backing plate 12 and first ball assembly 13 when removing the first backing plate 12 and first ball assembly 13.
The first target backing assembly 12 has a first taper shank 121, a first connector 122, and a first target holder 123.
The first taper shank 121 is a Morse taper shank having a downward taper that mates with the Morse taper sleeve 111 and may fall into the Morse taper sleeve 111. Because the Morse taper shank is highly matched to the Morse taper sleeve 111, upon removal, the nut 14 needs to be rotated upward to remove the Morse taper shank upward against friction.
The lower end of the first connecting piece 122 is fixed to the upper end of the first taper shank 121.
The first target holder 123 is fixed at the upper end of the first connecting piece 122, and the upper end of the first target holder 123 is a conical surface, and the conical surface is connected with the target 30 through magnetic attraction.
The first target ball assembly 13 is used as a measurement target of a laser scanner in a calibration process and comprises a first ball side taper 131, a first three-dimensional adjustment mechanism 132 and a first target ball 133.
The first ball side taper 131 is a Morse taper with its tip down, mates with the Morse taper sleeve 111 and may fall into the Morse taper sleeve 111. Because the Morse taper shank is highly matched to the Morse taper sleeve 111, upon removal, the nut 14 needs to be rotated upward to remove the Morse taper shank upward against friction. The first ball side taper 131 has the same tolerances and dimensions as the first taper 121.
The first three-dimensional adjusting mechanism 132 is a compact desk-top conjoined three-dimensional translation platform, and the bottom of the compact desk-top conjoined three-dimensional translation platform is provided with a mounting hole, and can be directly mounted at the upper end of the first ball side taper shank 131 for connection and fixation.
The sliding structure of the conjoined three-dimensional translation stage adopts a crossed roller guide structure, the X, Y translation stroke is 5mm, and the Z lifting stroke is 5mm. The first three-dimensional adjustment mechanism 132 translates or lifts the platform using a differential head with a minimum resolution of 0.01 mm.
The first target ball 133 is mounted on the tabletop of the three-dimensional translation stage concentrically with the target mirror 30 under adjustment of the micro head. The outer surface of the first target ball 133 is a matte spherical surface.
The target lens 30 is used as a target of a laser tracker when calibrating the laser scanner with the laser tracker. The outer sphere of the target 30 is 1.5 inches in diameter and contains a corner cube.
The length provider 40 is used to carry the first split calibration target 10 and the second split calibration target 20. In this embodiment, the length providing member 40 is a rigid structural member.
The laser tracker is used for measuring the coordinate positions of the target lens 30 when the target lens support assembly 12 and the target lens support assembly 22 are positioned, and further, the distance value between the target lens support assembly 12 and the target lens support assembly 22 is obtained as a standard distance value, so that the spatial distance indication error of the laser scanner is obtained by comparing the spherical center distance value of the first target ball 133 in the first target ball assembly 13 and the spherical center distance value of the second target ball 233 of the second target ball assembly 23, which are scanned by the laser scanner.
Before calibrating the laser scanner by the calibration device 100, concentricity correction is first performed on the target lens 30 and the first target ball 133 in the first split calibration target 10 and the second target ball 233 in the second split target 20.
The concentricity correction of the target lens 30 and the first target ball 133 mainly includes the steps of:
step 1-1, the first backing plate support assembly 12 is fixedly positioned in the Morse taper sleeve 111 of the first backing plate 11 via the first taper shank 121, and then the first backing plate 11 is secured to the table of the three-coordinate measuring machine.
Step 1-2, the target 30 is placed on the first target holder 123 of the first target holding assembly 12.
Step 1-3, coordinates of 5 points on the spherical outer contour of the target mirror 30 are measured using a three-coordinate measuring machine.
Step 1-4, fitting to obtain the center coordinates (x) of the spherical outer contour of the target lens 30 based on the coordinates of 5 points on the spherical outer contour of the target lens 30 measured in step 1-3 j ，y j ，z j )。
In steps 1-5, the first backing plate 11 is held in place on the table of the three-coordinate measuring machine, and the first backing plate support assembly 12 is removed by rotating the nut 14 to jack up the first taper shank 121.
In steps 1-6, the first target ball assembly 13 is mounted in the Morse taper sleeve 111 of the first target holder 11 through the first ball side taper shank 131, and coordinates of 5 points on the outer contour of the first target ball 133 of the first target ball assembly 13 are measured using a three-coordinate measuring machine.
Step 1-7, fitting to obtain the center coordinates (x) of the first target sphere 133 based on the coordinates of 5 points of the outer contour of the first target sphere 133 measured in step 1-6 q ，y q ，z q )。
Step 1-8, calculating the deviation value of the center coordinates of the target lens 30 and the center coordinates of the first target ball 133 according to the following formula, wherein, delta x ＝x q -x j ，△ y ＝y q -y j ，△ z ＝z q -z j 。
Step 1-9, according to the deviation value, passing through a first three-dimensional adjusting mechanism 13 in a first target ball assembly 13The micro-head in 2 adjusts the position of the first target ball 133 such that the offset value is delta x 、△ y 、△ z Are smaller than 20 mu m.
Step 1-10, when the deviation value is delta x 、△ y 、△ z When the two diameters are smaller than 20 μm, the first three-dimensional adjusting mechanism 132 is locked, and the concentricity of the target lens 30 and the first target ball 133 is corrected.
The step of correcting the concentricity of the target mirror 30 and the second target ball 233 of the second split calibration target 20 employs the step of correcting the concentricity of the target mirror 30 and the first target ball 133.
The calibration step of calibrating the laser scanner by using the concentricity corrected calibration apparatus 100 includes the steps of:
first, the first backing plate 11 and the second backing plate 21 are mounted on the length providing member 40 at a distance.
In a second step, the first target holding assembly 12 is mounted within the Morse taper sleeve 111 of the first backing plate 11 via the first taper shank 121.
Step three, the second target holding assembly 22 is mounted in the Morse taper sleeve 211 of the second backing plate 21 via the second taper shank 221.
Step four, the target 30 is placed on the first target holder 123 of the first target holding assembly 12.
Step five, measuring by using a laser tracker to obtain a first target coordinate value of the target lens 30.
Step six, the target 30 is removed from the first backing plate 123 of the first target holding assembly 12 and then placed on the second backing plate 223 of the second target holding assembly 22.
And step seven, measuring again by using a laser tracker to obtain a second target coordinate value of the target lens 30.
Step eight, obtaining the coordinates of the centers of the two spheres when the target lens 30 is respectively positioned on the first target lens seat 123 and the second target lens seat 223 according to the first target coordinate value and the second target coordinate value, and further obtaining the center distance of the two centers of the spheres, namely the standard distance value.
In this embodiment, when the standard distance value is measured, the position of the laser tracker is adjusted and the light through hole of the target lens 30 is ensured to be always right opposite to the laser tracker, so that the central connecting line of the target lens 30 coincides with the outgoing light of the laser tracker when the target lens 30 is positioned on the first target lens base 123 and the second target lens base 223.
Step nine, the first and second backing-up-assemblies 12, 22 are removed from the first and second backing plates 11, 21, respectively.
Step ten, the first target ball assembly 13 and the second target ball assembly 23 are respectively mounted on the first target holder 11 and the second target holder 21.
In step eleven, a center-of-sphere distance value between the first target ball 133 of the first target ball assembly 13 and the second target ball 233 of the second target ball assembly 23 is obtained by scanning with a laser scanner.
And step twelve, calculating a difference value between the sphere center distance value and the standard distance value, wherein the difference value is a space distance indication error of the laser scanner.
In this embodiment, the calibration device 100 used in the calibration of the laser scanner includes a first split calibration target 10, a second split calibration target 20, a target lens 30, a length providing member 40, and a laser tracker, and in practical application, the calibration device may include a target lens, N split calibration targets, a length providing member for carrying the split calibration targets, and a laser tracker, where N is greater than or equal to 3.
The calibration method of the calibration device comprising N split calibration targets comprises the following steps: firstly, through the concentricity correction method, concentricity correction is sequentially carried out on the target lens and the target ball of each split type calibration target, then target seats of N split type calibration targets after the concentricity correction are simultaneously installed at different positions on a length connecting piece, the target lens seat supporting components of each split type calibration target are connected with the corresponding target seats, and then the coordinate positions of the target lens when the target lens is positioned on the target lens seats of each lens seat supporting component are measured by using a laser tracker.
And selecting any two targets as a group of measurement pairs, and obtaining a standard distance value according to the distance difference value of the target mirror at the coordinate positions of the two targets. And then the target mirror supporting components of the two targets are removed and replaced by target ball components corresponding to the targets, the target balls in the two target ball components are measured by using a laser scanner, the ball center distance values of the two target balls are obtained, and the difference value between the ball center distance values and the standard distance values is calculated.
And similarly, selecting two different targets as another group of measurement pairs, and calculating the difference value between the spherical center distance value and the standard distance value between the two targets in the measurement pairs until the difference value between the spherical center distance value and the standard distance value between all any two targets in the N split targets is obtained, wherein the largest value in the measured difference values is the space distance indication error of the laser scanner.
For example, when the number of the split type calibration targets is four, the four split type calibration targets are respectively marked as A, B, C, D, firstly, the difference value between the center of sphere distance value between A and B and the standard distance value is measured, then, the difference value between the center of sphere distance value and the standard distance value among A and C, between A and D, between B and C, between B and D and between C and D is sequentially measured, and finally, the largest value in the measured difference values is the error of the space distance indication value of the laser scanner.
Error analysis concerning the calibration of a laser scanner using the calibration device of the present invention is as follows:
the forming of the error component introduced by the standard distance value using the calibration device includes: the laser tracking instrument comprises a laser tracking instrument ranging error, a laser tracking instrument target lens center positioning error, a laser scanner target ball surface shape error, a target lens and scanning target ball concentricity error, a Morse cone repeated positioning error and a deviation between a laser tracking instrument target lens sphere center and a Morse cone axis.
Wherein, the error of the pure radial ranging of the laser tracker after wavelength compensation is better than 10 -6 L and L are standard distances, and when the standard distance is 3m, the error introduced when the laser tracker calibrates the standard distance is 3 mu m.
The center positioning precision of the target mirror of the laser tracker with high precision on the market is 0.0001 inch, namely 2.54 mu m. The error of the shape of the target ball surface of the laser scanner is 15 μm. The difference value of the center coordinates of the center of the target mirror of the laser tracker and the center of the scanning target ball can be adjusted within 35 mu m by a three-coordinate measuring machine and an optical calibration method. The center positioning precision (concentricity of the center of the target lens and the outline of the target ball) of the split type calibration target can reach 0.05mm.
The repeated positioning error of the Morse taper shank can be obtained by measuring by a three-coordinate machine. The target mirror of the laser tracker is placed on the Morse taper shank, the mounting target seat is fixed on a workbench of a three-coordinate machine, the spherical center three-dimensional coordinate of the target mirror is obtained each time in a three-coordinate point fitting mode, the spherical center coordinate of the target mirror after the Morse taper shank is repeatedly disassembled and assembled for a plurality of times is measured, and the Morse taper repeated positioning error can be obtained, wherein the maximum value is 10 mu m.
When the Morse taper shank is arranged in the Morse taper sleeve of the target seat, the relative position of the Morse taper shank and the target seat on the circumference cannot be guaranteed to be completely the same each time the Morse taper shank is arranged in the same axial position in the Morse taper sleeve due to the circumferential characteristic of the Morse taper shank. Therefore, when there is a deviation between the center of the target lens of the laser tracker and the axis of the Morse taper shank, errors are also introduced in providing the standard distance. The error can be ensured to be within 10 μm by machining.
Finally, the calibration device formed by the split calibration target is used, and the uncertainty of the provided standard distance can reach 0.1mm within the length range of 3 m.
Effects and effects of the examples
According to the split calibration target in this embodiment, because the taper shank and the ball-side taper shank are Morse taper shanks having the same dimensions and tolerances and the Morse taper sleeve is matched with the Morse taper shank, the target mirror support assembly and the target ball assembly of the split calibration target can accurately fall into the Morse taper sleeve of the target holder through the Morse taper shanks, providing accurate positioning and high repeatability accuracy.
According to the calibration device in this embodiment, the target lens is used as a target of the laser tracker, the two split target lens supporting components for calibrating the target lens provide coordinate positions of the target lens, the target lens is used for the laser tracker to measure and obtain a standard distance value, the two target balls are used for the laser scanner to measure a ball center distance value, and a difference value between the ball center distance value and the standard distance value is calculated to obtain a space distance indication error of the laser scanner.
According to the method for calibrating the laser scanner by using the calibrating device in the embodiment, concentricity correction is firstly carried out on the target lens and the first target ball as well as the target lens and the second target ball respectively, the laser tracker can be directly used for calibrating the laser scanner, and the time and labor consuming mode of fitting the sphere center on the target ball of the scanner by adopting the point of the target lens of the laser tracker is avoided. And the concentricity of the target mirror and the target ball can be ensured, so that the laser tracker is utilized to calibrate the laser scanner with higher accuracy.
In addition, through optical calibration, the center positioning error of the split type calibration target is within 0.05mm, which is about an order of magnitude higher than the center positioning accuracy of + -0.01 inch (+ -0.25 mm) of a scanning ball which can be matched with a target lens seat in the market, and the split type calibration target is more suitable for being used as a standard for laser scanner calibration.
In addition, the target ball component is arranged on the standard rod, so that the portable standard for calibrating the laser scanner can be formed, and the problems of on-site and outdoor long-distance calibration of the laser scanner are solved.
In addition, in the present embodiment, the nut is used as the jacking mechanism of the Morse taper shank, so that the Morse taper shank is separated from the Morse taper sleeve more quickly and easily.
The split type calibration targets can also be installed in a three-dimensional large-size space laboratory, so that the repeatability measurement and the space indication error calibration of the laser radar and the laser scanner are realized.
In addition, a multisource heterogeneous network is formed by using a plurality of large-size measuring instruments, so that field measurement applications such as digital assembly of large-size parts are realized, and the multisource heterogeneous network is one of future large-size measurement research hotspots. The standard of various measurement systems is unified, and the application of the universal target or the interchangeable target is not separated, so that the split type calibration target and the assembling and calibrating method in the embodiment are easy to expand and apply to the universal target.
In addition, the embodiment also relates to a calibration device comprising at least three split calibration targets, and a standard distance value can be formed between any two groups by utilizing a plurality of split calibration targets, so that more data references are provided for the calibration of the space distance indication errors of the laser scanner.
The above embodiments are preferred examples of the present invention, and are not intended to limit the scope of the present invention.
Claims (7)
1. The utility model provides a split type calibration target, cooperatees to be measuring the target and use for when utilizing the laser tracker to calibrate the space distance indication error of laser scanner with the target mirror, its characterized in that includes:
a target holder;
the target mirror supporting component is provided with a taper shank, a connecting piece arranged on the taper shank and a target mirror seat arranged on the connecting piece and used for being connected with the target mirror through magnetic attraction; and
the target ball component is provided with a ball side taper shank, a three-dimensional adjusting mechanism arranged on the ball side taper shank and a target ball arranged on the three-dimensional adjusting mechanism,
wherein the taper shank and the ball side taper shank are Morse taper shanks which have the same size and tolerance and the taper points are arranged downwards,
the target seat is provided with a Morse taper sleeve, the taper tip of the Morse taper sleeve is downward, the opening is upward,
the Morse taper sleeve is matched with the taper shank and the ball side taper shank, the three-dimensional adjusting mechanism is a connected three-dimensional translation table, an external thread is arranged on the outer side surface of the target seat, which is positioned at the opening of the Morse taper sleeve,
the split type calibration target further comprises a nut, wherein the nut is matched with the external thread and is used for rotating upwards and jacking the taper shank and the ball side taper shank.
2. A calibration device for calibrating a spatial distance indication error of a laser scanner, comprising:
a target mirror;
a first split calibration target having a first backing plate, a first target mirror support assembly, and a first target ball assembly having a first target ball;
a second split calibration target having a second backing plate, a second target mirror support assembly, and a second target ball assembly having a second target ball;
a length provider for carrying the first split calibration target and the second split calibration target; and
the laser tracker is used for emitting laser and measuring the coordinates of the target lens when the target lens is respectively positioned on the first target lens supporting component and the second target lens supporting component, and obtaining a distance value between the two coordinates as a standard distance value, the first target ball and the second target ball are used as measuring targets of the laser scanner and are used for the laser scanner to scan to obtain a sphere center distance value between the first target ball and the second target ball, so that a difference value between the sphere center distance value and the standard distance value is calculated to obtain a space distance indication value error of the laser scanner,
wherein the first split calibration target and the second split calibration target are both split calibration targets of claim 1.
3. The calibration device of claim 2, wherein:
wherein the outer surface of the target ball is a matte spherical surface.
4. A method of calibrating a laser scanner using the calibration device of claim 3, comprising the steps of:
firstly, carrying out concentricity correction on a target lens, a first target ball and a second target ball of the calibrating device by using a three-coordinate measuring machine;
step two, the first target seat and the second target seat are respectively arranged on the length providing piece;
step three, respectively installing the first target mirror supporting component and the second target mirror supporting component on the first target seat and the second target seat;
step four, placing a target lens on a first target lens seat of the first target lens bearing assembly;
measuring by using a laser tracker to obtain a first target coordinate value of the target mirror;
step six, the target lens is removed from the first target lens supporting component and placed on a second target lens seat of the second target lens supporting component;
measuring again by using a laser tracker to obtain a second target coordinate value of the target mirror;
step eight, obtaining the center distance of the two sets of split type calibration targets as a standard distance value according to the first target coordinate value and the second target coordinate value;
step nine, removing the first target supporting component and the second target supporting component,
step ten, respectively mounting the first target ball component and the second target ball component on the first target seat and the second target seat;
eleventh step, scanning by using the laser scanner to obtain a sphere center distance value between a first target sphere of the first target sphere assembly and a second target sphere of the second target sphere assembly;
and step twelve, calculating a difference value between the sphere center distance value and the standard distance value, wherein the difference value is a space distance indication error of the laser scanner.
5. The method of calibrating according to claim 4, wherein:
in the first step, the correction of the concentricity of the target lens and the first target ball comprises the following steps:
step 1-1, fixedly arranging the first target mirror supporting component on the first target seat, and then fixing the first target seat on a workbench of the three-coordinate measuring machine;
step 1-2, placing the target on the first target holding assembly,
step 1-3, measuring coordinates of 5 points on the spherical outer contour of the target lens by using the three-coordinate measuring machine;
step 1-4, fitting to obtain the center coordinate (x) of the spherical outer contour of the target lens according to the coordinates of 5 points on the spherical outer contour of the target lens measured in step 1-3 j ，y j ，z j ）；
Step 1-5, keeping the position of the target seat fixed on a workbench of the three-coordinate measuring machine unchanged, and taking down the first target mirror supporting component;
step 1-6, mounting the first target ball assembly on the first target seat, and measuring coordinates of 5 points on the outer contour of the first target ball assembly by using the three-coordinate measuring machine;
step 1-7, fitting to obtain the center coordinate (x) of the first target sphere according to the coordinates of 5 points of the outer contour of the first target sphere measured in step 1-6 q ，y q ，z q ）;
Step 1-8, calculating a deviation value between the center coordinates of the target lens and the center coordinates of the first target ball according to the following formula, wherein delta is calculated x =x q -x j ，△ y =y q -y j ，△ z =z q - z j ；
Step 1-9, adjusting a first three-dimensional adjusting mechanism in the target ball assembly according to the deviation value to enable the deviation value to be reduced x 、△ y 、△ z Are all smaller than 20 mu m;
step 1-10, when the deviation value is delta x 、△ y 、△ z And when the two diameters are smaller than 20 mu m, locking the first three-dimensional adjusting mechanism to finish the correction of concentricity of the target mirror and the first target ball.
6. The method of calibrating according to claim 5, wherein:
the step of correcting the concentricity of the target lens and the second target ball adopts the step of correcting the concentricity of the target lens and the first target ball.
7. A calibration device for calibrating a spatial distance indication error of a laser scanner, comprising:
a target mirror;
at least three split calibration targets, each comprising a target holder, a target mirror support assembly, and a target ball assembly having a target ball;
a length provider for carrying the split calibration target; and
the laser tracker is used for measuring the center coordinates of the target mirror when being positioned on any one target mirror supporting component, obtaining the distance value between any two target mirror supporting components corresponding to any two center coordinates according to any two center coordinates as a standard distance value, obtaining the space distance indication error of the laser scanner according to the difference value of the standard distance value and the spherical center distance value between the corresponding two target balls,
wherein the split calibration target is the split calibration target of claim 1.
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