CN115575409A - Optical detection system and zero positioning detection method thereof - Google Patents
Optical detection system and zero positioning detection method thereof Download PDFInfo
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- CN115575409A CN115575409A CN202211194749.5A CN202211194749A CN115575409A CN 115575409 A CN115575409 A CN 115575409A CN 202211194749 A CN202211194749 A CN 202211194749A CN 115575409 A CN115575409 A CN 115575409A
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Abstract
The invention relates to an optical detection system and a zero point positioning detection method thereof, which comprises the steps of prefabricating a plurality of positioning fixtures, presetting a zero point mark on one fixture, recording the shape and the radius value of the zero point mark, installing the positioning fixtures on a workbench of the optical detection system, taking a picture by using an industrial control camera, obtaining a color image containing the preset zero point mark on the fixture, identifying the color image by using a main control computer, determining the zero point positions of an X axis and a Y axis of the preset zero point mark, calculating a definition evaluation value, determining the zero point position of a Z axis of the preset zero point mark, obtaining the zero point position of the optical detection system, finally placing an object to be detected on the workbench, fixing the object to be detected by using the fixture, adjusting the optical imaging system and the workbench to move along the X axis, the Y axis and the Z axis of a three-axis motion system, and enabling the center point position of the object to be detected to coincide with the zero point position of the optical detection system, thus obtaining the zero point detection position of the object to be detected. The method is simple and convenient, and has high positioning precision.
Description
Technical Field
The invention relates to the field of machine vision detection, in particular to an optical detection system driven by an open-loop stepping motor and a zero point positioning detection method thereof.
Background
The detection system based on machine vision is widely applied to the field of article appearance detection, for example, no obvious flaw on the surface of a chip is ensured through an appearance detection link after the chip is packaged, and the quality of the chip is ensured. Such detection systems typically employ high resolution, small field of view cameras to capture images with sharp details. Because different types of articles are different in size and height, after the detection system is started, the industrial control camera needs to be moved to a proper position (the position is represented by three-dimensional X, Y and Z coordinates) through the three-axis motion system to align to the area to be detected and shoot a clear image.
The three-dimensional X, Y and Z coordinate positions of the camera need corresponding reference zero points, some optical detection systems are driven by open-loop stepping motors, and the three-axis position detection of the motion system is realized by adopting limit switches and zero point switches, so that the complexity of hardware and wiring is increased, the positioning precision is not high, and the camera is usually in a millimeter level. Some optical detection systems are driven by expensive high-precision closed-loop servo stepping motors, and can directly acquire the current movement position. Therefore, for the optical detection system driven by the open-loop stepping motor still used at present, a detection method with low complexity and high detection precision is urgently needed to be found so as to realize the high-precision positioning detection of the optical detection system driven by the open-loop stepping motor.
Disclosure of Invention
The invention provides an optical detection system and a zero positioning detection method thereof, which are used for solving the technical problems of complex hardware and connecting lines and low positioning accuracy caused by the fact that an optical detection system driven by an open-loop stepping motor in the prior art adopts a limit switch and a zero switch to realize three-axis position detection of a motion system.
In order to achieve the above object, the present invention provides a zero point positioning detection method for an optical detection system, which specifically comprises the following steps:
s1, prefabricating a plurality of positioning fixtures, presetting a zero mark on one fixture, recording the shape and the radius value of the zero mark, and installing the plurality of positioning fixtures on a workbench of an optical detection system;
s2, taking a picture by using an industrial control camera in the optical detection system to obtain a color image containing a preset zero mark on the clamp;
s3, identifying the obtained color image containing the zero point mark preset on the fixture by adopting a main control computer in the optical detection system, and determining the X-axis zero point position and the Y-axis zero point position of the zero point mark preset on the fixture;
s4, calculating a definition evaluation value of the preset zero mark on the clamp by adopting a main control computer in the optical detection system, and determining the zero position of the Z axis of the preset zero mark on the clamp according to a hill climbing algorithm to obtain the zero position of the optical detection system;
and S5, placing the object to be detected on a workbench of the optical detection system and fixing the object to be detected by using a plurality of positioning clamps, and adjusting the optical imaging system and the workbench in the optical detection system to move along the X, Y and Z axes of the three-axis movement system so that the position of the center point of the object to be detected is superposed with the position of the zero point of the optical detection system to obtain the zero point detection position of the object to be detected.
Preferably, the color image obtained in step S2 includes images of a plurality of similar fixtures with preset zero marks, and the step S3 identifies the obtained color image including the preset zero marks on the fixtures to determine the X-axis zero position and the Y-axis zero position of the preset zero marks on the fixtures, and specifically includes the following steps:
s31, a main control computer in the optical detection system receives and processes a color image containing a preset zero mark on the fixture, and calculates the central positions and radius values of the obtained multiple similar images;
s32, comparing the radius values of the plurality of similar images with the radius value of the zero mark preset on the fixture, and determining the image with the radius error smaller than the preset value as the zero mark preset on the fixture;
and S33, recording the central position of the preset zero mark on the clamp as the X-axis zero position and the Y-axis zero position of the preset zero mark on the clamp.
Preferably, the step S4 of calculating the sharpness evaluation value of the preset zero mark on the fixture by using a main control computer in the optical detection system specifically includes the following steps:
s41, extracting a color image of the preset zero mark on the clamp through the X-axis zero position, the Y-axis zero position and the radius value of the preset zero mark on the clamp;
s42, graying the color image of the preset zero mark on the clamp to obtain a gray image;
s43, calculating the gradient of the gray image by using a Sobel operator;
and S44, calculating the average value of the gradients of the gray level images as the definition evaluation value of the preset zero point mark on the clamp.
Preferably, in step S4, the zero point position of the Z axis of the preset zero point mark on the fixture is determined according to a hill climbing algorithm, so as to obtain the zero point position of the optical detection system, specifically:
s45, driving the three-axis motion system to move by adopting a controller in the optical detection system, so that the optical imaging system fixed on the Z axis moves along a single direction on the Z axis by a preset movement step length;
s46, acquiring an image definition evaluation value once when the optical imaging system moves by one movement step, and recording the maximum value of the number of movement steps of the optical imaging system in the Z axis and the currently acquired image definition evaluation value;
and S47, repeating the step S46 until a maximum value point in the image definition evaluation value is searched, wherein the maximum value point corresponds to the Z-axis zero point position of the preset zero point mark on the clamp, and the three-dimensional coordinate of the preset zero point mark on the clamp at the position is used as the zero point position of the optical detection system.
Preferably, step S5 specifically includes:
s51, placing an article to be detected on a workbench of an optical detection system, and enabling the corner of the article to be detected and the inner side corner of the positioning clamp with the preset zero point mark to be superposed by taking the inner side corner of the positioning clamp with the preset zero point mark as a reference standard, wherein the surface to be detected faces the industrial control camera;
s52, turning on an LED annular light source and adjusting the brightness through a controller in the optical detection system to obtain an image of the to-be-detected object shot by the industrial control camera;
s53, calculating the height of the article to be detected in the Z-axis direction in the optical detection system through the height of the positioning clamp and the height of the article to be detected, calculating the number of steps of the optical imaging system which need to move in the Z axis according to the height, and controlling the optical imaging system to move corresponding steps to reach the position corresponding to the Z axis through the controller;
s54, acquiring the position coordinates of the X axis and the Y axis of the preset zero mark on the clamp at the moment through a main control computer in the optical detection system, calculating the deviation between the position coordinates of the X axis and the Y axis of the preset zero mark on the clamp and the position coordinates of the X axis and the Y axis of the image center of the object to be detected, driving the X axis and the Y axis of the three-axis motion system through a controller, enabling the workbench to move along the X axis and the Y axis, enabling the position of the center point of the object to be detected to coincide with the position of the zero point of the optical detection system, and enabling the position of the object to be detected to be the zero point detection position of the object to be detected at the moment.
Preferably, in step S54, the deviation between the position coordinates of the X-axis and the Y-axis of the preset zero mark on the fixture and the position coordinates of the X-axis and the Y-axis of the center of the image of the object to be detected is calculated in the following specific calculation manner:
s541, setting a preset zero point mark on the clamp as a point A, setting a point where two right-angle sides at the inner side of the positioning clamp with the preset zero point mark meet as a point B, marking the center point of the article to be detected as a point C, and setting the distance from the point A to the point B as a point L 1 The distance from point B to point C is set as L 2 ；
S542, drawing a rectangle by using the connecting line of the points A and B as a diagonal line, and obtaining L through measurement 1 Length L in X direction 1x And a length L in the Y direction 1y ；
S543, obtaining the overall dimension of the object to be detected according to the product data, and obtaining L from the overall dimension 2 Distance L in X direction 2x And a distance L in the Y direction 2y ；
S544, tongOver-comparing L obtained in step S542 1x And L obtained in step S543 2x Summing to obtain the distance from the point C to the point A in the X direction, namely the deviation of the X axis of the preset zero point mark on the clamp and the X axis position coordinate of the center of the to-be-detected article image;
s545, by comparing L obtained in step S542 1y And L obtained in step S543 2y And summing to obtain the distance from the point C to the point A in the Y direction, namely the deviation of the position coordinates of the Y axis of the preset zero point mark on the clamp and the Y axis of the center of the image of the object to be detected.
Preferably, the prefabricated positioning clamps in step S1 are all provided with screw mounting holes, and a plurality of positioning clamps are detachably mounted on a workbench in the optical detection system.
An optical detection system using a zero point positioning detection method comprises an open-loop stepping motor, a three-axis motion system, a main control computer, a controller, an optical imaging system, an LED annular light source, a workbench and a plurality of positioning fixtures, wherein one positioning fixture is provided with a zero point mark,
open loop stepper motor and triaxial moving system electrical connection, main control computer and optical imaging system electrical connection, controller one end and main control computer electrical connection, the other end respectively with triaxial moving system and LED annular light source electrical connection, the workstation is located the holding surface in the triaxial moving system, the plane that X axle and Y axle in the triaxial moving system confirmed is parallel with the surface of workstation, optical imaging system fixes on the Z axle of triaxial moving system, can follow Z axle direction motion, the central axis of optical imaging system coincides with the Z axle in the triaxial moving system, positioning fixture installs on the workstation, wherein:
the open-loop stepping motor is used for providing power for the three-axis motion system;
a controller for controlling the motion of the three-axis motion system and controlling the on-off and brightness of the LED annular light source
Adjusting;
the LED annular light source is used for providing an illumination light source for the object to be detected;
the optical imaging system is used for acquiring an image of an article to be detected on the workbench;
the workbench is used for mounting the positioning clamp and placing an article to be detected;
the positioning fixture is used for fixing the position of an article to be detected.
Preferably, the optical imaging system comprises an industrial control camera and an optical lens, the LED annular light source is fixed on the optical lens in a surrounding mode, central axes of the industrial control camera, the optical lens and the LED annular light source are overlapped to form an optical central axis, and the optical central axis is overlapped with the Z axis.
Preferably, the controller comprises a light source controller and a motion controller, wherein the light source controller is used for controlling the on-off and the brightness of the LED annular light source, and the motion controller is used for controlling the motion of the three-axis motion system.
The optical detection system and the zero point positioning detection method thereof are characterized in that a plurality of positioning fixtures are prefabricated, a zero point mark is preset on one fixture, the shape and the radius value of the zero point mark are recorded, the plurality of positioning fixtures are installed on a workbench of the optical detection system, an industrial control camera in the optical detection system is used for photographing to obtain a color image containing the zero point mark preset on the fixture, a main control computer in the optical detection system is used for identifying the obtained color image containing the zero point mark preset on the fixture, the X-axis zero point position and the Y-axis zero point position of the zero point mark preset on the fixture are determined, the definition evaluation value of the zero point mark preset on the fixture is calculated, the Z-axis zero point position of the zero point mark preset on the fixture is determined according to a climbing algorithm to obtain the zero point position of the optical detection system, finally, an article to be detected is placed on the workbench of the optical detection system and fixed by using a plurality of positioning fixtures, and the detection position of the article to be detected is obtained by adjusting the coincidence of the position of the zero point position of the optical imaging system and the zero point position of the optical detection system and the workbench along the movement system. The method searches for the optimal detection position of the object to be detected in the optical detection process by presetting the zero mark on the detection clamp, does not need to increase hardware and connecting wires, and is simple, convenient and high in positioning precision.
Drawings
Fig. 1 is a flowchart of a zero point positioning detection method of an optical detection system according to an embodiment of the invention;
FIG. 2 is a schematic view of an exemplary embodiment of a positioning fixture;
FIG. 3 is a schematic diagram illustrating an embodiment of determining an optimal object distance using a hill-climbing algorithm;
FIG. 4 is a schematic diagram illustrating a calculation of a positional deviation between a zero marker and a center of an image of an object to be detected according to an embodiment of the present invention;
fig. 5 is a schematic diagram of the connection relationship between the computer and other components according to an embodiment of the present invention.
Description of the reference numerals:
1. a main control computer; 2. a controller; 3. an optical imaging system; 4. an LED annular light source; 5. an object stage; 6. a three-axis motion system; 51. a work table; 52. positioning a clamp; 53. positioning a clamp; 54. positioning a clamp; 55. positioning a clamp; 56. detecting an article; 59. and marking a zero point.
Detailed Description
The invention is further described in detail below with reference to the drawings and specific embodiments.
In one embodiment, a zero point positioning detection method of an optical detection system specifically includes the following steps:
s1, prefabricating a plurality of positioning fixtures, presetting a zero mark on one fixture, recording the shape and the radius value of the zero mark, and installing the plurality of positioning fixtures on a workbench of an optical detection system;
s2, taking a picture by using an industrial control camera in the optical detection system to obtain a color image containing a preset zero mark on the clamp;
s3, identifying the obtained color image containing the preset zero mark on the clamp by adopting a main control computer in the optical detection system, and determining the X-axis zero position and the Y-axis zero position of the preset zero mark on the clamp;
s4, calculating a definition evaluation value of the preset zero mark on the clamp by adopting a main control computer in the optical detection system, and determining the zero position of the Z axis of the preset zero mark on the clamp according to a hill climbing algorithm to obtain the zero position of the optical detection system;
and S5, placing the object to be detected on a workbench of the optical detection system and fixing the object to be detected by using a plurality of positioning clamps, and adjusting the optical imaging system and the workbench in the optical detection system to move along the X, Y and Z axes of the three-axis movement system so that the position of the center point of the object to be detected is superposed with the position of the zero point of the optical detection system to obtain the zero point detection position of the object to be detected.
Specifically, referring to fig. 1 and fig. 2, fig. 1 is a flowchart of a zero point positioning detection method of an optical detection system according to an embodiment of the present invention; fig. 2 is a schematic view of an installation position of the positioning fixture in an embodiment of the invention.
A zero point positioning detection method of an optical detection system comprises the steps of presetting 4 positioning fixtures 52, 53,54 and 55, wherein the inner sides of the positioning fixtures are provided with two right-angle sides, a zero point mark 59 is preset on one positioning fixture 52, the contrast color with large brightness difference is adopted by the zero point mark 59 and the positioning fixtures 52, 53,54 and 55, the color of the zero point mark 59 is preferably black, the color of the positioning fixtures 52, 53,54 and 55 is white, the zero point mark 59 can be set to be circular (square or other shapes), the radius is 0.5 mm, the shape and the radius value of a preset graph are recorded in the system, the 4 positioning fixtures 52, 53,54 and 55 are installed on a workbench 51 of the optical detection system, then a color image containing the zero point mark preset on the zero point fixture is obtained through an industrial control camera in the optical detection system, images of the zero point mark preset marks on a plurality of similar fixtures are obtained, therefore, zero point mark zero point identification is needed to be carried out on the obtained through a main control computer in the optical detection system, the position of the zero point mark on the preset fixture is determined, and the position of an optical axis X axis is determined according to the evaluation value of the preset mark on the fixture, and the three-dimensional detection system, and the evaluation value of the clamp on the preset graph is calculated according to determine the position of the preset mark on the three-dimensional detection system. On the basis, an article to be detected is fixed on the workbench 51 through the positioning clamps 52, 53,54 and 55, and the position of the center point of the article to be detected is superposed with the position of the zero point of the optical detection system by adjusting the optical imaging system in the optical detection system and the workbench to move along the X, Y and Z axes of the three-axis movement system, so that the zero point detection position of the article to be detected is obtained, namely the optimal imaging position of the article to be detected. In addition, once the zero point of the optical detection system is determined, the zero point detection position of the article to be detected can be directly determined on the basis that the zero point detection position is the optimal imaging position of the article to be detected without adjusting the subsequent use. If sudden faults occur, such as power failure, abnormality of the master control computer system, etc., which may cause abnormal positioning of the optical detection system, the zero point position detection of the optical detection system needs to be performed again.
In one embodiment, the color image obtained in step S2 includes images of preset zero marks on a plurality of similar jigs, and the step S3 identifies the obtained color image including the preset zero marks on the jigs, and determines the X-axis zero position and the Y-axis zero position of the preset zero marks on the jigs, and specifically includes the following steps:
s31, a main control computer in the optical detection system receives and processes a color image containing a preset zero mark on the fixture, and calculates the central positions and radius values of the obtained multiple similar images;
s32, comparing the radius values of the plurality of similar images with the radius value of the preset zero mark on the clamp, and determining the image with the radius error smaller than the preset value as the preset zero mark on the clamp;
and S33, recording the center position of the preset zero mark on the clamp as the X-axis zero position and the Y-axis zero position of the preset zero mark on the clamp.
Specifically, a main control computer in an optical detection system receives a color image which is acquired by an industrial control camera and contains a preset zero mark on a fixture, graying, histogram equalization, gaussian blur, threshold segmentation and circle fitting are carried out on the color image, the center positions and radius values of all graphs similar to a preset circle are obtained through calculation, the radius of the obtained multiple similar graphs is compared with the radius of the preset circle, the radius error value is set to 10%, the circle with the radius error smaller than 10% in the acquired multiple similar circles is determined as the preset zero mark on the fixture through comparison, and the circle center position of the circle is recorded as the X-axis zero position and the Y-axis zero position of the preset zero mark on the fixture.
In an embodiment, the step S4 of calculating the sharpness evaluation value of the preset zero mark on the fixture by using a main control computer in the optical detection system specifically includes the following steps:
s41, extracting a color image of the preset zero mark on the clamp through the X-axis zero position, the Y-axis zero position and the radius value of the preset zero mark on the clamp;
s42, graying the color image of the preset zero mark on the clamp to obtain a gray image;
s43, calculating the gradient of the gray image by using a Sobel operator;
and S44, calculating the average value of the gradients of the gray level images to be used as the definition evaluation value of the preset zero mark on the clamp.
Specifically, the calculation process of the sharpness evaluation value of the preset zero mark on the jig is as follows: firstly, extracting a zero mark color image by using the position and radius of a preset zero mark on a clamp, then carrying out graying on the color image to obtain a gray image, then calculating the gradient of the gray image by using a Sobel operator, and finally calculating the average value of the image gradient to be used as a definition evaluation value of the preset zero mark on the clamp, wherein the image is clearer when the evaluation value is larger.
In one embodiment, in step S4, the zero point position of the Z axis of the preset zero point mark on the fixture is determined according to a hill climbing algorithm, and the zero point position of the optical detection system is obtained, specifically:
s45, driving the three-axis motion system to move by adopting a controller in the optical detection system, so that the optical imaging system fixed on the Z axis moves along a single direction on the Z axis by a preset movement step length;
s46, acquiring an image definition evaluation value once when the optical imaging system moves by one movement step, and recording the maximum value of the number of movement steps of the optical imaging system in the Z axis and the currently acquired image definition evaluation value;
and S47, repeating the step S46 until a maximum value point in the image definition evaluation value is searched, wherein the maximum value point corresponds to the Z-axis zero point position of the preset zero point mark on the clamp, and the three-dimensional coordinate of the preset zero point mark on the clamp at the position is used as the zero point position of the optical detection system.
Specifically, referring to fig. 3, fig. 3 is a schematic diagram illustrating an embodiment of the present invention that uses a hill-climbing algorithm to determine an optimal object distance.
The principle of obtaining the optimal object distance by adopting the hill climbing algorithm is that when the object distance of the industrial control camera changes, the obtained image definition curve has the characteristics of single peak and monotony, is similar to a parabola, the extreme point of the curve corresponds to the position where the industrial control camera images clearest, and when the position is away, the definition curve shows a monotonous decreasing trend no matter in the forward direction or in the reverse direction.
The process of acquiring the zero position (i.e. the optimal object distance) of the Z axis of the preset zero mark on the clamp by adopting the hill climbing algorithm is as follows: the optical imaging system fixed on a Z axis in the three-axis motion system is driven by a motion controller in the optical motion system to move along a single direction on the Z axis in a preset motion step length, an image definition evaluation value climbs along the direction shown by A → B → C → Peak → D → E, the optical imaging system acquires the image definition evaluation value once per moving step, the maximum value of the motion step number of the optical imaging system on the Z axis and the currently acquired image definition evaluation value is recorded, the optical imaging system is considered to cross the optimal object distance position if the definition evaluation values of two times are smaller than the currently recorded maximum image definition evaluation value as the optical imaging system continues to move on the Z axis, when the optical imaging system crosses the Peak point to reach the E point, the zero point D and the definition evaluation value of the E are both smaller than the definition evaluation value of the Peak position, the Peak position is the optimal object distance position, the controller drives the three-axis motion system to enable the zero point to move to the opposite direction, and the optical imaging system marks the position of the optical imaging system on the position as the position of the clamp, and the mark of the position of the Z axis is marked on the position of the clamp.
In an embodiment, step S5 specifically includes:
s51, placing an article to be detected on a workbench of an optical detection system, and enabling the corner of the article to be detected and the inner side corner of the positioning fixture with the zero mark to be superposed by taking the inner side corner of the positioning fixture with the zero mark as a reference standard, wherein the surface to be detected faces an industrial control camera;
s52, turning on an LED annular light source and adjusting the brightness through a controller in the optical detection system to obtain an image of the to-be-detected object shot by the industrial control camera;
s53, calculating the height of the article to be detected in the Z-axis direction in the optical detection system through the height of the positioning clamp and the height of the article to be detected, calculating the number of steps of the optical imaging system, which need to move in the Z axis, and controlling the optical imaging system to move corresponding steps to reach the position corresponding to the Z axis through the controller;
s54, acquiring the position coordinates of the X axis and the Y axis of the preset zero point mark on the clamp at the moment through a main control computer in the optical detection system, calculating the deviation between the position coordinates of the X axis and the Y axis of the preset zero point mark on the clamp and the position coordinates of the X axis and the Y axis of the image center of the object to be detected, driving the X axis and the Y axis of the three-axis motion system through a controller, enabling the workbench to move along the X axis and the Y axis, enabling the position of the center point of the object to be detected to coincide with the position of the zero point of the optical detection system, and enabling the position of the object to be detected to be the position of the zero point detection position of the object to be detected at the moment.
Specifically, the confirmation process of the zero point detection position of the article to be detected is as follows:
1) Placing an article to be detected on a workbench of an optical detection system, and enabling the corner of the article to be detected and the inner side corner of the positioning fixture with the zero point mark to be superposed by taking the inner side corner of the positioning fixture with the zero point mark as a reference standard, wherein the article to be detected faces an industrial control camera;
2) The LED annular light source is started and the brightness is adjusted through a controller in the optical detection system;
3) Calculating the height of the article to be detected in the Z-axis direction in the optical detection system through the height of the positioning clamp and the height of the article to be detected, calculating the number of steps of the optical imaging system which need to move in the Z axis according to the height, and controlling the optical imaging system to move corresponding number of steps to reach the position corresponding to the Z axis through the controller;
for example, the movement step length is set to be 0.1mm, the height of the positioning fixture is 2mm, the height of the chip to be tested is 5mm, the positioning fixture and the chip to be tested are both positioned on a workbench in the optical detection system, the height of the chip to be tested in the Z axis is 3mm relative to the zero point position of the optical detection system, the height can be calculated by the preset movement step length being 0.1mm, the optical imaging system needs to move upwards for 30 steps in the Z axis, and the controller controls the optical imaging system to move for 30 steps to reach the corresponding position.
4) The deviation between the center coordinates of the preset zero point mark on the clamp and the center coordinates of the image of the object to be detected is calculated through a main control computer in the optical detection system, the X axis and the Y axis of the three-axis motion system are driven through the controller, the position of the center point of the object to be detected is superposed with the position of the zero point of the optical detection system, the position where the object to be detected is located is the zero point detection position of the object to be detected, and the industrial control camera can obtain the clearest image of the object to be detected at the moment.
In one embodiment, in step S54, the deviation between the position coordinates of the X-axis and the Y-axis of the preset zero mark on the fixture and the position coordinates of the X-axis and the Y-axis of the center of the image of the object to be detected is calculated in the following specific manner:
s541, setting a preset zero point mark on the clamp as a point A, setting a point where two right-angle sides at the inner side of the positioning clamp with the preset zero point mark meet as a point B, marking the center point of the article to be detected as a point C, and setting the distance from the point A to the point B as a point L 1 The distance from point B to point C is set as L 2 ；
S542, drawing a rectangle by using the connecting line of the points A and B as a diagonal line, and obtaining L through measurement 1 Length L in X direction 1x And a length L in the Y direction 1y ；
S543, obtaining the overall dimension of the object to be detected according to the product data, and obtaining L from the overall dimension 2 Distance L in X direction 2x And a distance L in the Y direction 2y ；
S544, comparing L obtained in step S542 1x And L obtained in step S543 2x Summing to obtain the distance from the point C to the point A in the X direction, namely the deviation of the X axis of the preset zero point mark on the clamp and the X axis position coordinate of the center of the to-be-detected article image;
s545, by comparing L obtained in step S542 1y And L obtained in step S543 2y And summing to obtain the distance from the point C to the point A in the Y direction, namely the deviation of the position coordinates of the Y axis of the preset zero point mark on the clamp and the Y axis of the center of the image of the object to be detected.
Specifically, referring to fig. 4, fig. 4 is a schematic diagram of calculating a position deviation of the zero point mark from the center of the image of the object to be detected according to an embodiment of the present invention.
Firstly, a zero mark preset on a clamp is set as a point A, a point where two right-angle sides inside a positioning clamp preset with the zero mark meet is set as a point B, a central point of an article to be detected is marked as a point C, and the distance from the point A to the point B is set as a point L 1 And the distance from the point B to the point C is set as L 2 (ii) a Then drawing a rectangle by using the connecting line of the points A and B as a diagonal line, and obtaining L by measurement 1 Length L in X direction 1x And length L in Y direction 1y (ii) a Then, the overall dimension of the object to be detected can be found (or obtained by measurement) according to the product manual, and the length of the object to be detected is set as a, the width of the object to be detected is set as b, so that L can be obtained 2 Distance L in X direction 2x Distance L in Y direction of = a/2 2y = b/2; finally, by pairing the obtained L 1x And L 2x Summing to obtain the distance from the point C to the point A in the X direction, namely the deviation of the X axis of the preset zero point mark on the clamp and the X axis position coordinate of the center of the to-be-detected article image; by pairing the obtained L 1y And L 2y Summing to obtain the distance from point C to point A in Y direction, i.e. presetting a zero mark on the fixtureAnd recording the deviation of the Y-axis position coordinate of the center of the image of the object to be detected and the Y-axis position coordinate of the center of the image of the object to be detected. It should be noted that, a plurality of articles to be detected may also be placed in the special tray for detection, and the size of the tray needs to be taken into consideration when calculating the deviation, and the specific calculation method is not described herein again.
In one embodiment, the plurality of positioning jigs prefabricated in step S1 are each provided with a screw mounting hole, and the plurality of positioning jigs are detachably mounted on a workbench in the optical detection system.
Specifically, the positioning fixture 52 provided with the zero point mark 59 is fixedly installed at the lower left of the workbench 51 through screws, and the other positioning fixtures 53,54 and 55 are installed at other corners of the workbench 51 through screws, so that when fixing an object to be detected, only the positioning fixtures 53,54 and 55 need to be adjusted, and optical detection of objects to be detected with different sizes or multiple objects to be detected can be met.
In one embodiment, the optical detection system using the zero point positioning detection method comprises an open-loop stepping motor, a three-axis motion system, a main control computer, a controller, an optical imaging system, an LED annular light source, a workbench and a plurality of positioning fixtures, wherein one positioning fixture is provided with a zero point positioning mark,
open loop stepper motor and triaxial moving system electrical connection, main control computer and optical imaging system electrical connection, controller one end and main control computer electrical connection, the other end respectively with triaxial moving system and LED annular light source electrical connection, the workstation is located the holding surface in the triaxial moving system, the plane that X axle and Y axle in the triaxial moving system confirmed is parallel with the surface of workstation, optical imaging system fixes on the Z axle of triaxial moving system, can follow Z axle direction motion, the central axis of optical imaging system coincides with the Z axle in the triaxial moving system, positioning fixture installs on the workstation, wherein:
the open-loop stepping motor is used for providing power for the three-axis motion system;
the controller is used for controlling the three-axis motion system to move and controlling the on-off and brightness adjustment of the LED annular light source;
the LED annular light source is used for providing an illumination light source for the object to be detected;
the optical imaging system is used for acquiring an image of an article to be detected on the workbench;
the workbench is used for installing the positioning clamp and placing an article to be detected;
the positioning fixture is used for fixing the position of an article to be detected.
As a further improvement of the embodiment, the optical imaging system comprises an industrial control camera and an optical lens, the LED annular light source is fixed on the optical lens in a surrounding mode, the central axes of the industrial control camera, the optical lens and the LED annular light source are coincident to form an optical central axis, and the optical central axis is coincident with the Z axis.
As a further improvement of the embodiment, the controller comprises a light source controller and a motion controller, the light source controller is used for controlling the on-off and the brightness of the LED annular light source, and the motion controller is used for controlling the motion of the three-axis motion system.
Specifically, referring to fig. 2 and 5, fig. 2 is a schematic diagram of an installation position of the positioning fixture in an embodiment of the present invention, and fig. 5 is a schematic diagram of a connection relationship between a computer and other components in an embodiment of the present invention.
The optical detection system comprises an open-loop stepping motor, a main control computer 1, a controller 2, an optical imaging system 3, an LED annular light source 4, an object stage (not shown in figure 5) and a three-axis motion system 6, wherein the main control computer 1 is electrically connected with the controller 2 and the optical imaging system 3, and the controller 2 is electrically connected with the three-axis motion system 6 and the LED annular light source 4; the object stage is positioned on a supporting surface in the three-axis motion system 6, a plane determined by an X axis and a Y axis in the three-axis motion system 6 is parallel to the surface of the object stage, and a Z axis in the three-axis motion system 6 is coincided with the central axis of the optical imaging system 3;
furthermore, the optical imaging system 3 comprises a high-resolution industrial control camera and an optical lens, a main control computer is connected with the industrial control camera in the optical imaging system 3 through an Ethernet and is used for setting working parameters of the industrial control camera and acquiring a shot image, the LED annular light source 4 is fixed on the optical lens in a surrounding mode, and the central axes of the industrial control camera, the optical lens and the LED annular light source are overlapped and are called as an optical central axis.
Further, the controller 2 comprises a light source controller and a motion controller, the main control computer 1 is connected with the light source controller and the motion controller through a USB interface, the light source controller is used for controlling the on-off and the brightness of the LED annular light source 4, and the motion controller is used for controlling the motion of the three-axis motion system.
Further, the stage includes a working platform 51 and positioning fixtures 52, 53,54,55, an object to be detected (such as a single chip or a tray storing a plurality of chips) is placed on the working platform 51, one corner of the object to be detected is tightly attached to the corner of the positioning fixture 52 for fixing, the surface to be detected faces the optical imaging system 3, and other parts of the object to be detected are fixed by using the remaining positioning fixtures 53,54,55 according to actual needs.
The above description is only an embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of changes or substitutions within the technical scope of the present invention, and all such changes or substitutions are included in the scope of the present invention. Moreover, the technical solutions in the embodiments of the present invention may be combined with each other, but it is necessary to be able to be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, the combination of the technical solutions should be considered to be absent, and is not within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (10)
1. A method for zero-point positioning detection in an optical detection system, the method comprising the steps of:
s1, prefabricating a plurality of positioning fixtures, presetting a zero mark on one fixture, recording the shape and the radius value of the zero mark, and installing the plurality of positioning fixtures on a workbench of an optical detection system;
s2, taking a picture by using an industrial control camera in an optical detection system to obtain a color image containing a preset zero mark on the clamp;
s3, identifying the obtained color image containing the zero point mark preset on the fixture by adopting a main control computer in an optical detection system, and determining the zero point position of the X axis and the zero point position of the Y axis of the zero point mark preset on the fixture;
s4, calculating a definition evaluation value of a preset zero mark on the clamp by adopting a main control computer in the optical detection system, and determining the zero position of the Z axis of the preset zero mark on the clamp according to a hill climbing algorithm to obtain the zero position of the optical detection system;
and S5, placing the object to be detected on a workbench of the optical detection system and fixing the object to be detected by using the plurality of positioning clamps, and adjusting the optical imaging system and the workbench in the optical detection system to move along the X, Y and Z axes of the three-axis movement system so that the central point position of the object to be detected coincides with the zero point position of the optical detection system to obtain the zero point detection position of the object to be detected.
2. The zero-point positioning detection method for optical detection system according to claim 1, wherein the color image obtained in step S2 includes images of the preset zero-point marks on a plurality of similar jigs, and the step S3 identifies the obtained color image including the preset zero-point marks on the jigs, and determines the X-axis zero-point position and the Y-axis zero-point position of the preset zero-point marks on the jigs, and includes the following steps:
s31, a main control computer in the optical detection system receives and processes the color image containing the preset zero mark on the clamp, and calculates the central positions and the radius values of the obtained multiple similar images;
s32, comparing the radius values of the plurality of similar images with the radius value of a preset zero mark on the clamp, and determining the image with the radius error smaller than the preset value as the preset zero mark on the clamp;
and S33, recording the central position of the preset zero mark on the clamp as the X-axis zero position and the Y-axis zero position of the preset zero mark on the clamp.
3. The zero point positioning detection method of the optical detection system as claimed in claim 2, wherein the step S4 of calculating the evaluation value of the definition of the preset zero point mark on the fixture by using a main control computer in the optical detection system specifically comprises the following steps:
s41, extracting a color image of the preset zero mark on the clamp according to the X-axis zero position, the Y-axis zero position and the radius value of the preset zero mark on the clamp;
s42, graying the color image of the preset zero mark on the clamp to obtain a gray image;
s43, calculating the gradient of the gray image by using a Sobel operator;
and S44, calculating the average value of the gradients of the gray level images, and taking the average value as the definition evaluation value of the preset zero point mark on the clamp.
4. The zero-point positioning detection method of the optical detection system according to claim 3, wherein in the step S4, the zero-point position of the Z-axis of the preset zero-point mark on the fixture is determined according to a hill-climbing algorithm, so as to obtain the zero-point position of the optical detection system, specifically:
s45, driving the three-axis motion system to move by adopting a controller in the optical detection system, so that the optical imaging system fixed on the Z axis moves along a single direction on the Z axis by a preset movement step length;
s46, acquiring an image definition evaluation value once when the optical imaging system moves by one movement step, and recording the maximum value of the number of movement steps of the optical imaging system in the Z axis and the currently acquired image definition evaluation value;
and S47, repeating the step S46 until a maximum value point in the image definition evaluation value is searched, wherein the maximum value point corresponds to the Z-axis zero point position of the preset zero point mark on the clamp, and the three-dimensional coordinate of the preset zero point mark on the clamp at the position is used as the zero point position of the optical detection system.
5. The zero point positioning detection method of the optical detection system according to claim 4, wherein the step S5 specifically includes:
s51, placing an article to be detected on a workbench of an optical detection system, and enabling the corner of the article to be detected and the inner side corner of the positioning fixture with the zero mark to be superposed by taking the inner side corner of the positioning fixture with the zero mark as a reference standard, wherein the surface to be detected faces an industrial control camera;
s52, turning on an LED annular light source and adjusting the brightness through a controller in the optical detection system to obtain an image of the to-be-detected object shot by the industrial control camera;
s53, calculating the height of the article to be detected in the Z-axis direction in the optical detection system through the height of the positioning clamp and the height of the article to be detected, calculating the number of steps of the optical imaging system which need to move in the Z axis according to the height, and controlling the optical imaging system to move corresponding steps to reach the position corresponding to the Z axis through the controller;
s54, acquiring the position coordinates of the X axis and the Y axis of the preset zero mark on the clamp at the moment through a main control computer in the optical detection system, calculating the deviation between the position coordinates of the X axis and the Y axis of the preset zero mark on the clamp and the position coordinates of the X axis and the Y axis of the image center of the object to be detected, driving the X axis and the Y axis of the three-axis motion system through a controller, enabling the workbench to move along the X axis and the Y axis, enabling the position of the center point of the object to be detected to coincide with the position of the zero point of the optical detection system, and enabling the position of the object to be detected to be the zero point detection position of the object to be detected at the moment.
6. The zero point positioning detection method for optical detection system according to claim 5, wherein the deviation between the position coordinates of the X-axis and the Y-axis of the preset zero point mark on the fixture and the position coordinates of the X-axis and the Y-axis of the center of the image of the object to be detected is calculated in step S54 by:
s541, setting a preset zero point mark on the clamp as a point A, setting a point where two right-angle sides on the inner side of the positioning clamp with the preset zero point mark meet as a point B, marking the central point of the object to be detected as a point C, and setting the distance from the point A to the point B as a point L 1 And the distance from the point B to the point C is set as L 2 ；
S542, drawing by using the connection line of the two points A and B as a diagonal lineA rectangle, L is obtained by measurement 1 Length L in X direction 1x And a length L in the Y direction 1y ；
S543, obtaining the overall dimension of the object to be detected according to the product data, and obtaining L from the overall dimension 2 Distance L in X direction 2x And a distance L in the Y direction 2y ；
S544, L obtained by the step S542 1x And L obtained in step S543 2x Summing to obtain the distance from the point C to the point A in the X direction, namely the deviation of the X axis of the preset zero point mark on the clamp and the X axis position coordinate of the center of the to-be-detected article image;
s545, obtaining L through the step S542 1y And L obtained in step S543 2y And summing to obtain the distance from the point C to the point A in the Y direction, namely the deviation of the position coordinates of the Y axis of the preset zero point mark on the clamp and the Y axis of the center of the image of the object to be detected.
7. The zero point positioning detection method of optical inspection system according to claim 1, wherein each of the prefabricated positioning jigs in step S1 has a screw mounting hole, and a plurality of the positioning jigs are detachably mounted on a table in the optical inspection system.
8. An optical inspection system, which is characterized in that the method of any one of claims 1 to 7 is used for zero point positioning inspection, the optical inspection system comprises an open loop stepping motor, a three-axis motion system, a main control computer, a controller, an optical imaging system, an LED annular light source, a workbench and a plurality of positioning fixtures, wherein one of the positioning fixtures is provided with a zero point positioning mark,
the open-loop stepping motor is electrically connected with the three-axis motion system, the main control computer is electrically connected with the optical imaging system, one end of the controller is electrically connected with the main control computer, the other end of the controller is electrically connected with the three-axis motion system and the LED annular light source respectively, the workbench is positioned on a supporting surface in the three-axis motion system, a plane determined by an X axis and a Y axis in the three-axis motion system is parallel to the surface of the workbench, the optical imaging system is fixed on the Z axis of the three-axis motion system and can move along the Z axis direction, the central axis of the optical imaging system is superposed with the Z axis in the three-axis motion system, and the positioning clamp is installed on the workbench, wherein:
the open-loop stepping motor is used for providing power for the three-axis motion system;
the controller is used for controlling the three-axis motion system to move and controlling the on-off and brightness adjustment of the LED annular light source;
the LED annular light source is used for providing an illuminating light source for the object to be detected;
the optical imaging system is used for acquiring an image of an article to be detected on the workbench;
the workbench is used for installing the positioning clamp and placing an article to be detected;
the positioning fixture is used for fixing the position of an article to be detected.
9. The optical inspection system of claim 8 wherein the optical imaging system includes an industrial camera and an optical lens, the LED ring light source is circumferentially fixed on the optical lens, and the central axes of the industrial camera, the optical lens and the LED ring light source coincide to form an optical central axis, and the optical central axis coincides with the Z-axis.
10. The optical inspection system of claim 8 wherein the controller includes a light source controller for controlling the switching and brightness of the LED ring light and a motion controller for controlling the motion of the three axis motion system.
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| CN202211194749.5A CN115575409A (en) | 2022-09-29 | 2022-09-29 | Optical detection system and zero positioning detection method thereof |
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| CN202211194749.5A CN115575409A (en) | 2022-09-29 | 2022-09-29 | Optical detection system and zero positioning detection method thereof |
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