CN211042092U - Calibration device of small-hole inner and outer wall vision measurement system - Google Patents
Calibration device of small-hole inner and outer wall vision measurement system Download PDFInfo
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- CN211042092U CN211042092U CN201922362701.0U CN201922362701U CN211042092U CN 211042092 U CN211042092 U CN 211042092U CN 201922362701 U CN201922362701 U CN 201922362701U CN 211042092 U CN211042092 U CN 211042092U
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Abstract
The utility model provides a calibration device of a visual measurement system for the inner and outer walls of a small hole, wherein the calibration device takes a detected workpiece sample as a calibration piece; three through round holes with the same diameter are arranged at a set position of a workpiece sample to be detected, and connecting lines among the three through round holes form a right-angled triangle; two through round holes forming one of right-angle sides of the right-angle triangle are positioned on the same bus and are used for determining a standard sample of the pixel size in the y-axis direction; and two through round holes forming the other right-angle side of the right-angle triangle are positioned in the same circumferential direction and are used for calibrating the pixel size standard sample in the x-axis direction. The utility model discloses can realize inner wall and outer wall when demarcation and circumference and axial when demarcation to directly go on the current platform of system, have simple structure, mark effectual characteristics.
Description
Technical Field
The utility model relates to a measure and mark technical field, specifically, relate to a calibration device of aperture inside and outside wall vision measurement system.
Background
The visual images of all parts of the inner and outer walls of the workpiece are acquired through a visual measurement system, and after being processed by a digital image technology, complete expanded digital images of the inner and outer walls are presented. The basic unit of a digital image is a pixel, so to know the actual dimensions of the measured workpiece and the size and relative position information of the defect, the corresponding coefficient between the pixel and the actual physical dimensions must be determined, i.e., the specific physical dimensions represented by each pixel is determined. In machine vision inspection, calibration is a very important link, and is a precondition and a basis for image measurement.
Currently, the most common method for calibrating pixel equivalent of vision measuring system is to use calibration board or standard component method, i.e. comparing the precise physical size of calibration object with known features and the corresponding image pixel size in camera, to obtain the pixel equivalent at the object distance (see kingdom a kind of jade. qian kelong. line camera calibration method review [ J/O L ]. optics: 1-24[2019-12-04]. http:// kns. cnki. net/kcms/detai l/31.1252.o4.20191126.1528.014. html.).
For example, it is found through retrieval that:
bichao et al, in "research on method of calibrating rotation axis based on visual measurement", used a customized rectangular calibration block for calibration, which also required mechanical adjustment of the orientation of the calibration block, and had a low level of automation (see Bichao, Haowski, Liubang, House building, research on method of calibrating rotation axis based on visual measurement [ J/O L ]. Infrared and laser engineering: 1-9[2019-12-04]. http:// kns. cnki. net/kcms/tail/12.1261. tn.20191021.1456.002.html.).
Aged sunshine and the like of the building university perform robot vision calibration based on HA L CON, a calibration plate with a calibration function based on Halcon software HAs the characteristics of easy extraction of calibration points, high calibration precision, unique direction and the like, the calibration plate is an equilateral rectangular frame, 7 rows and 7 columns of black circular targets with consistent sizes are arranged in the frame, each circle center can be used as a calibration point, all the black circular targets are arranged at equal intervals, the arrangement mode is simple, the coordinates of the circle centers of the circular targets are easy to extract, the calibration algorithm of a camera is simple, the measurement precision is high, but the visual field range which can be measured by a 45-degree reflector of a vision measurement system is also small due to the small inner diameter of a small hole, and the problem is that how to mark the calibration points on the inner wall and all the required calibration points are imaged in the effective visual field range (see aged sunshine, Wang Yi, Wang based on HA L CON).
The Huoyanping et al gathers a commonly used pixel equivalent calibration method in a thesis 'pixel equivalent calibration method for vision measurement', designs a novel pixel equivalent calibration object, the calibration object consists of two black solid circles with equal diameters, the accurate physical size of the circle center distance is D, the circle center distance is D, and the adopted photographic paper with better quality is used according to the following steps of 1: 1, the calibration object is printed in proportion and is pasted on a hard and thin board, thereby ensuring higher planeness, and the measurement system is calibrated by calibrating the coefficient of the actual size and the pixel number, compared with the traditional pixel equivalent calibration object, the calibration object can obtain the required pixel equivalent calibration parameter without precise calibration auxiliary equipment, and has low manufacturing cost, no direction marking requirement, simple and convenient operation in the use process and strong anti-interference capability, but the precision and the measurement repeatability of the method are not high enough, the connecting line between two circles can be calibrated in one direction, if the calibration is carried out on the inner surface, the outer surface and different directions of each surface of a workpiece, the repeated operation is needed for multiple times (refer to Howly, Wangeyi, Liuzhonglin, a pixel equivalent calibration method for vision measurement [ J ]. nanotechnology and precise engineering, 2014,12(05):373-380.).
At present, no explanation or report similar to the technology of the utility model is found, and similar data at home and abroad are not collected yet.
SUMMERY OF THE UTILITY MODEL
The utility model discloses to current calibration method and detecting system's particularity, provide a feasible aperture inside and outside wall vision measurement system's calibration device. The calibration device takes a workpiece sample as a calibration piece, and three through holes are punched on the sample as calibration holes to mark the actual size. The calibration device is simple in structure, the calibration device is placed on the existing measurement platform, the measurement of an actual workpiece can be calibrated, the problem of marking on the inner surface of a small-caliber hole piece is solved, the simultaneous circumferential and axial calibration and the simultaneous calibration of the inner wall and the outer wall can be realized, the corresponding position relation of an expansion image measured by the inner wall and the outer wall can be determined by positioning the positions of three calibration holes, and accurate positioning is realized.
The utility model discloses a realize through following technical scheme.
A calibration device of a visual measurement system for the inner and outer walls of a small hole comprises one or more calibration pieces, wherein each calibration piece adopts a detected workpiece sample as a basic piece, three through round holes with the same diameter are arranged at a set position on the detected workpiece sample, and connecting lines among the three through round holes form a right triangle; wherein:
two through round holes forming one of right-angle sides of the right-angle triangle are positioned on the same bus and are used for determining a standard sample of the pixel size in the y-axis direction;
and two through round holes forming the other right-angle side of the right-angle triangle are positioned in the same circumferential direction and are used for calibrating the pixel size standard sample in the x-axis direction.
Preferably, three of the through circular holes are all in the measurement visual field of the vision measurement system.
Preferably, the center distances between the two groups of through round holes forming the right-angle sides are equal.
Preferably, the three through circular holes have diameters of: 200 and 300 microns.
Preferably, the distance between the centers of the two groups of through round holes forming the right-angle side is as follows: 300-500 microns.
Compared with the prior art, the utility model discloses following beneficial effect has:
the utility model provides a calibration device of aperture inside and outside wall vision measurement system, wherein, calibration device is in order to be detected the work piece appearance as the calibration piece, beat the three round hole that runs through as calibration hole mark actual size on being detected the work piece appearance, the design that runs through the round hole, not only solved how to carry out the difficult problem of mark at the little bore little deep hole spare internal surface, can also realize inner wall and outer wall standardization in the time, through the three position of demarcating the hole of location, can confirm the corresponding position relation that the expansion image was measured to the inside and outside wall, two double-phase combination between the three round hole, alright mark aperture surface circumference and axial simultaneously. The calibration device is simple in structure, simple and efficient to use and operate, more suitable for calibration under the measurement condition with a relatively small visual field, and high in precision and measurement repeatability.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
fig. 1 is a schematic structural view of a small-aperture workpiece according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a system for vision measurement of inner and outer walls of a small hole according to an embodiment of the present invention;
fig. 3 is a schematic diagram illustrating a measurement of an inner wall of a workpiece according to an embodiment of the present invention;
fig. 4 is a schematic diagram illustrating measurement of the outer wall of the workpiece according to an embodiment of the present invention;
fig. 5 is a schematic view of workpiece calibration provided in an embodiment of the present invention.
Detailed Description
The following is a detailed description of embodiments of the present invention: this embodiment is using the utility model discloses technical scheme carries out under the prerequisite, has given detailed implementation mode and specific operation process. It should be noted that, for those skilled in the art, without departing from the spirit of the present invention, several variations and modifications can be made, which are within the scope of the present invention.
The embodiment of the utility model provides a calibration device of a vision measurement system for the inner and outer walls of a small hole, which takes a detected workpiece sample as a calibration piece; the workpiece sample to be detected is provided with three through round holes with equal diameters at a set position, and connecting lines among the three through round holes form a right-angled triangle; wherein:
two through round holes forming one of right-angle sides of the right-angle triangle are positioned on the same bus and are used for determining a standard sample of the pixel size in the y-axis direction;
and two through round holes forming the other right-angle side of the right-angle triangle are positioned in the same circumferential direction and are used for calibrating the pixel size standard sample in the x-axis direction.
Specifically, the method comprises the following steps:
the preparation process of the calibration device mainly comprises three steps:
1) designing and manufacturing a detected workpiece sample as a calibration piece;
2) calibrating the calibration piece; the calibration process is to adopt the prior art to calibrate the calibration piece in advance, which is a common technical means in the field and is not described herein again.
3) The vision measuring system is calibrated by the calibrated calibration piece.
Firstly, designing and processing a calibration piece, and punching 3 through round holes with equal diameters at a set position (such as a middle thin neck position) of a detected workpiece sample piece, wherein the upper hole and the lower hole are arranged on the same bus and used for determining a calibration sample of a pixel size in the y-axis direction, and the left hole and the right hole are arranged in the same circumferential direction and used for calibrating a calibration sample of a pixel size in the x-axis direction.
Because the mirror-based inner wall detection method passes through a 45 ° plane mirror, the field of view is small. The effective imaging area needs to be taken into account when making the calibration piece, ensuring that all 3 holes need to be in the field of view of the vision measurement system when measuring the pixel distance (number of pixels) of a circle.
The embodiment of the utility model provides a calibration device, its theory of operation is:
the calibration of the vision measuring system to the workpiece is completed by establishing the proportional relation between the accurate physical dimension and the pixel number between the circle center distances of the circular holes. The calibration device has simple structure and good calibration effect, can be used as a calibration piece in a visual measurement system, can be used for determining the conversion coefficient between the pixel and the size of the visual measurement system and also can be used for determining the bus of a workpiece, and provides a foundation for intercepting and splicing subsequent images.
The technical solutions provided by the above embodiments of the present invention are further described in detail below with reference to the accompanying drawings and specific applications.
The embodiment of the utility model provides a calibration device and calibration method can be applied to and directly carry out the work piece on the current vision measurement system platform and mark.
As shown in fig. 2, the existing vision measurement system platform includes: the system comprises an area array CCD camera, a telecentric lens, an annular light source, a spherical reflector, a rotary platform and a computer; assembling a telecentric lens and a front-section lens of a CCD camera, sequentially fixing a detected workpiece on an optical bracket from top to bottom, adjusting the position of the optical bracket to enable the axis of the lens and the axis of the detected workpiece to be on the same vertical axis, placing and fixing a spherical reflector on a reflector bracket, horizontally fixing the reflector bracket on a rotating platform to realize the precise adjustment of the spatial position of the spherical reflector, adjusting the height of the rotating platform to enable the spherical reflector to go deep into a workpiece hole from the bottom of the detected workpiece, adjusting the rotating platform to enable the center of the spherical reflector to be located on the vertical axis of the detected workpiece, and connecting the CCD camera with a computer through a kilomega network line. (for a specific structure, see the Chinese patent application publication No. CN 103575748A, "optical inspection system for inner wall of workpiece with micro aperture").
As shown in fig. 1, namely, the detected workpiece is obtained, wherein the optical principle for measuring the inner wall of the small hole of the detected workpiece is shown in fig. 3, and the measuring principle for the outer wall of the detected workpiece is shown in fig. 4.
Firstly, design and processing of a calibration piece are carried out, and 3 through round holes with equal diameters are punched at the middle thin neck part of a detected workpiece sample, as shown in fig. 5. The upper and lower 2 holes are on the same bus for determining the standard sample of the pixel size in the y-axis direction, and the left and right 2 holes are on the same circumference for calibrating the standard sample of the pixel size in the x-axis direction.
Because the mirror-based inner wall detection method passes through a 45 ° plane mirror, the field of view is small. The effective imaging area therefore needs to be taken into account when making the calibration piece, ensuring that all 3 holes need to be in the field of view of the vision system when measuring the pixel distance of the circle.
The working process and the working principle of the calibration device are as follows:
the calibration of the calibration piece is completed by a vision measurement system, and the parameters required to be calibrated comprise the center distance A between the two vertical holes, the distance B between the lower round hole and the bottom surface of the workpiece, the center distance C between the two horizontal holes, an included angle α between the connecting line of the centers of the two vertical holes and the bus of the workpiece, and an included angle β between the connecting line of the centers of the two circumferential holes and the bus of the workpiece.
The workpiece is horizontally placed on a rotating platform of the vision measuring system through the clamp and is adjusted through the two-axis rotating device, so that the axis of the calibrated workpiece is parallel to the horizontal plane, the 3 through holes are opposite to the CCD camera, and the position of an optical measuring head of the CCD camera is adjusted until the image of the circular hole appears at the center of the screen.
At least 3 points (preferably more than 10 points) are selected from the edge of each through circular hole to form an enveloping circle, and the center of the circle is obtained by a least square method.
And (4) calculating the coordinates of the circle center of the through round hole, and solving the corresponding circle center distance.
When the vision measuring system is used for processing images, a rectangular area is cut out and the images are spliced by taking a bus of a workpiece as a reference, so that the obtained images are rectangular images with the outer walls expanded in a height range. If the intercepted rectangular area is not parallel to the bus, the image splicing can be shifted in the image registration and fusion process, and the visual detection effect is influenced. Therefore, the included angle between the connection line of the circle centers of the two holes in the vertical direction and the workpiece bus needs to be determined when the calibration piece is calibrated, and the direction of the workpiece bus can be determined according to the connection line and the calibrated angle when the system is calibrated. The generatrix of the workpiece is a straight line which is parallel to the axis of the workpiece and vertical to the bottom surface, the bottom surface of the workpiece is taken as a reference surface, and then the direction of the generatrix can be obtained by making a perpendicular line. The contact type measurement of the vision measurement system is not influenced by the curvature of the surface of the workpiece, and the basic geometric shape of the object can be rapidly and accurately measured by matching with a computer, so that the vision measurement system has higher accuracy and reliability. Finally, a reference surface at the bottom of the workpiece can be constructed in a point-by-point entering and exiting mode through the contact type measuring head, and therefore the direction of the workpiece bus is determined.
Before the vision measuring system runs, the pixel equivalent is calibrated to establish the corresponding relation between the pixels of the camera image and the actual size of the workpiece under the current condition. The calibration of the system pixel equivalent is completed by an experimental calibration method.
The calibration of the system is divided into the following steps:
1. opening a system and placing a calibration workpiece on a platform of an actual measurement object;
2. adjusting the focal length, the posture of the reflector and the brightness of the light source to enable the system to image clearly;
3. manually rotating the rotary platform to enable 3 round holes to appear in an imaging area;
4. calculating the number of pixels occupied between the centers of the small holes through system software;
5. and marking the direction of the workpiece bus according to the pre-corrected included angle between the connection line of the centers of the small holes and the bus. The correction method adopts the prior art, is a common technical means in the field, and is not described herein again.
6. And calculating the pixel equivalent according to the calibrated actual size and the pixels.
Assuming that the center distance is the length A and the corresponding number of pixels is N, the actual physical size corresponding to each pixel is
The desired actual size is obtained by multiplying the measured actual pixel size by the scaling factor.
The utility model discloses above-mentioned embodiment provides a calibration device of outer wall vision measurement system in aperture relates to the interior outer wall vision measurement system's of small size aperture work piece demarcation technique. Through making three through holes with connecting lines in a right-angle shape on a sample piece of a detected workpiece, the proportional relation between the accurate physical dimension between the circle center distances of the circular holes and the pixel distance can be established through the existing vision measuring system, the calibration of the system is completed, and the simultaneous calibration of the inner wall and the outer wall and the simultaneous calibration of the circumferential direction and the axial direction are realized. The calibration device can be directly carried out on the existing platform of the system, and has the characteristics of simple structure and good calibration effect.
The foregoing description of the specific embodiments of the invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes and modifications may be made by those skilled in the art within the scope of the appended claims without departing from the spirit of the invention.
Claims (5)
1. A calibration device of a visual measurement system for inner and outer walls of a small hole is characterized by comprising one or more calibration pieces, wherein each calibration piece adopts a detected workpiece sample as a basic piece, three through round holes with equal diameters are arranged at a set position on the detected workpiece sample, and connecting lines among the three through round holes form a right triangle; wherein:
two through round holes forming one of right-angle sides of the right-angle triangle are positioned on the same bus;
two through round holes forming the other right-angle side of the right-angle triangle are positioned in the same circumferential direction.
2. The calibrating device for the visual measuring system of the inner and outer walls of the small hole as claimed in claim 1, wherein in the working state, all three through circular holes are located in the measuring visual field of the visual measuring system.
3. The calibrating device for the visual measuring system of the inner and outer walls of the small hole as claimed in claim 1, wherein the distance between the centers of the two groups of through round holes forming the right-angle sides is equal.
4. The calibration device for the visual measurement system of the inner and outer walls of the small hole according to claim 1, wherein the diameters of the three through circular holes are as follows: 200 and 300 microns.
5. The calibrating device for the visual measuring system of the inner and outer walls of the small hole according to claim 3, wherein the distance between the centers of two groups of through round holes forming the right-angle edge is as follows: 300-500 microns.
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