Optical detection system and zero point positioning detection method thereof

Abstract

The present invention relates to an optical detection system and a zero-point positioning detection method thereof. First, several positioning fixtures are prefabricated and a zero-point mark is preset on one of the fixtures, and its shape and radius value are recorded. The positioning fixture is installed on a workbench of the optical detection system, and an industrial control camera is used to take a photo to obtain a color image containing the preset zero-point mark on the fixture. The color image is recognized by a main control computer, and the zero-point positions of the preset zero-point mark on the X and Y axes are determined. A clarity evaluation value is calculated, and the zero-point position of the preset zero-point mark on the Z axis is determined to obtain the zero-point position of the optical detection system. Finally, an object to be detected is placed on the workbench and fixed with a fixture. The optical imaging system and the workbench are adjusted to move along the X, Y, and Z axes of a three-axis motion system so that the center point position of the object to be detected coincides with the zero-point position of the optical detection system, thereby obtaining the zero-point detection position of the object to be detected. The method is simple and convenient, and has high positioning accuracy.

Description

Technical Field

[0001] The present invention relates to the field of machine vision detection, and in particular to an optical detection system driven by an open-loop stepping motor and a zero-point positioning detection method thereof. Background Art

[0002] Machine vision-based inspection systems are widely used in the field of appearance inspection of items. For example, after chip packaging, they undergo appearance inspection to ensure that there are no obvious defects on the chip surface and to guarantee chip quality. These inspection systems typically use high-resolution, small-field-of-view cameras to capture detailed images. Because different items vary in size and height, once the inspection system is activated, a three-axis motion system is required to move the industrial control camera to the appropriate position (position represented by three-dimensional X, Y, and Z coordinates) to align it with the inspection area and capture a clear image.

[0003] The camera's three-dimensional X, Y, and Z coordinate positions require a corresponding reference zero point. Some optical inspection systems use open-loop stepper motors, employing limit switches and zero-point switches to detect the three-axis position of the motion system. This increases hardware and wiring complexity, and results in low positioning accuracy, typically in the millimeter range. Some optical inspection systems use more expensive, high-precision closed-loop servo stepper motors, which can directly determine the current motion position. Therefore, for the open-loop stepper motor-driven optical inspection systems currently in use, there is an urgent need to find a low-complexity, high-precision detection method to achieve high-precision positioning detection for these open-loop stepper motor-driven optical inspection systems. Summary of the Invention

[0004] The present invention provides an optical detection system and a zero-point positioning detection method thereof, so as to solve the technical problems in the prior art of using an open-loop stepper motor-driven optical detection system to realize three-axis position detection of the motion system using limit switches and zero-point switches, resulting in complex hardware and wiring and low positioning accuracy.

[0005] To achieve the above object, the present invention provides a zero point positioning detection method for an optical detection system, which specifically includes the following steps:

[0006] S1. Prefabricate several positioning fixtures, preset a zero mark on one of the fixtures, record the shape and radius of the zero mark, and install the several positioning fixtures on the workbench of the optical inspection system;

[0007] S2. Use the industrial control camera in the optical inspection system to take a photo and obtain a color image including the preset zero point mark on the fixture;

[0008] S3, using a main control computer in the optical detection system to recognize the acquired color image containing the preset zero point mark on the fixture, and determine the X-axis zero point position and the Y-axis zero point position of the preset zero point mark on the fixture;

[0009] S4. Calculate the clarity evaluation value of the preset zero mark on the fixture using the main control computer in the optical detection system, determine the Z-axis zero position of the preset zero mark on the fixture using a hill climbing algorithm, and obtain the zero position of the optical detection system;

[0010] S5. Place the object to be inspected on the workbench of the optical inspection system and fix it with several positioning fixtures. Adjust the optical imaging system and the workbench in the optical inspection system to move along the X, Y, and Z axes of the three-axis motion system so that the center point position of the object to be inspected coincides with the zero point position of the optical inspection system, thereby obtaining the zero point detection position of the object to be inspected.

[0011] Preferably, the color image acquired in step S2 includes a plurality of images similar to the preset zero mark on the fixture, and step S3 recognizes the acquired color image including the preset zero mark on the fixture to determine the X-axis zero point position and the Y-axis zero point position of the preset zero point mark on the fixture, specifically comprising the following steps:

[0012] S31, a main control computer in the optical detection system receives and processes a color image including a preset zero point mark on the fixture, and calculates the center position and radius value of multiple similar images obtained;

[0013] S32, comparing the radius values ​​of the multiple similar images with the radius value of the preset zero mark on the fixture, and identifying the image with a radius error smaller than the preset value as the preset zero mark on the fixture;

[0014] S33. Record the center position of the preset zero point mark on the fixture as the X-axis zero point position and the Y-axis zero point position of the preset zero point mark on the fixture.

[0015] Preferably, in step S4, a main control computer in the optical detection system is used to calculate the clarity evaluation value of the preset zero point mark on the fixture, which specifically includes the following steps:

[0016] S41, extracting a color image of the preset zero point mark on the fixture according to the X-axis zero point position and the Y-axis zero point position and the radius value of the preset zero point mark on the fixture;

[0017] S42, gray-scaling the color image of the preset zero point mark on the fixture to obtain a grayscale image;

[0018] S43, using the Sobel operator to calculate the gradient of the grayscale image;

[0019] S44. Calculate the average value of the gradient of the grayscale image as the clarity evaluation value of the preset zero point mark on the fixture.

[0020] Preferably, in step S4, the Z-axis zero point position of the preset zero point mark on the fixture is determined according to the hill climbing algorithm to obtain the zero point position of the optical detection system, specifically:

[0021] S45, using a controller in the optical detection system to drive the three-axis motion system to move, so that the optical imaging system fixed on the Z axis moves along a single direction on the Z axis with a preset motion step length;

[0022] S46. The optical imaging system obtains an image clarity evaluation value every time it moves a motion step, and records the maximum value of the motion steps of the optical imaging system on the Z axis and the currently obtained image clarity evaluation value;

[0023] S47. Repeat step S46 until a maximum point in the image clarity evaluation value is found. This maximum point corresponds to the Z-axis zero position of the preset zero point mark on the fixture. The three-dimensional coordinates of the preset zero point mark on the fixture at this position are used as the zero position of the optical detection system.

[0024] Preferably, step S5 specifically includes:

[0025] S51. Place the object to be inspected on the workbench of the optical inspection system, using the inner corner of a positioning fixture with a preset zero point mark as a reference, so that the corners of the object to be inspected and the inner corners of the positioning fixture with a preset zero point mark coincide with each other, with the surface to be inspected facing the industrial control camera;

[0026] S52, turning on the LED ring light source and adjusting the brightness through a controller in the optical inspection system to obtain an image of the object to be inspected taken by the industrial control camera;

[0027] S53, calculating the height of the object to be inspected in the Z-axis direction in the optical inspection system based on the height of the positioning fixture and the height of the object to be inspected, thereby calculating the number of steps the optical imaging system needs to move in the Z-axis, and controlling the optical imaging system to move the corresponding number of steps to reach the corresponding position on the Z-axis through the controller;

[0028] S54. Obtain the X-axis and Y-axis position coordinates of the preset zero point mark on the fixture at this time through the main control computer in the optical detection system, calculate the deviation between the X-axis and Y-axis position coordinates of the preset zero point mark on the fixture and the X-axis and Y-axis position coordinates of the center of the image of the object to be detected, drive the X-axis and Y-axis of the three-axis motion system through the controller, and move the workbench along the X-axis and Y-axis so that the center point position of the object to be detected coincides with the zero point position of the optical detection system. The position of the object to be detected at this time is the zero point detection position of the object to be detected.

[0029] Preferably, in step S54, the deviations between the X-axis and Y-axis position coordinates of the preset zero point mark on the fixture and the X-axis and Y-axis position coordinates of the center of the image of the object to be inspected are calculated in the following manner:

[0030] S541. Set the preset zero point mark on the fixture as point A, set the point where the two right-angled sides on the inner side of the positioning fixture with the preset zero point mark as point B, mark the center point of the object to be inspected as point C, set the distance from point A to point B as L1, and the distance from point B to point C as L2;

[0031] S542. Draw a rectangle with the line connecting points A and B as the diagonal line. By measuring, the length L1 in the X direction can be obtained. 1x and the length L in the Y direction 1y ;

[0032] S543. The dimensions of the object to be tested can be obtained from the product data, and the distance L2 in the X direction can be obtained from the dimensions. 2x and the distance L in the Y direction 2y ;

[0033] S544, by performing the L obtained in step S542 1x and L obtained in step S543 2x Sum the distance from point C to point A in the X direction, which is the deviation between the X-axis position coordinate of the preset zero point mark on the fixture and the X-axis position coordinate of the center of the image of the object to be inspected;

[0034] S545, by performing the L obtained in step S542 1y and L obtained in step S543 2y The sum is calculated to obtain the distance from point C to point A in the Y direction, which is the deviation between the Y-axis position coordinates of the preset zero point mark on the fixture and the Y-axis position coordinates of the center of the image of the object to be inspected.

[0035] Preferably, the pre-positioning fixtures in step S1 are all provided with screw mounting holes, and several positioning fixtures are detachably mounted on a workbench in the optical detection system.

[0036] An optical detection system using a zero-point positioning detection method includes an open-loop stepper motor, a three-axis motion system, a main control computer, a controller, an optical imaging system, an LED ring light source, a workbench, and several positioning fixtures, one of which is provided with a zero-point mark.

[0037] The open-loop stepper motor is electrically connected to the three-axis motion system, the main control computer is electrically connected to the optical imaging system, one end of the controller is electrically connected to the main control computer, and the other end is electrically connected to the three-axis motion system and the LED ring light source respectively. The workbench is located on the support surface of the three-axis motion system. The plane defined by the X-axis and Y-axis of 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 coincides with the Z-axis of the three-axis motion system. The positioning fixture is installed on the workbench, wherein:

[0038] Open-loop stepper motors are used to power the three-axis motion system;

[0039] Controller, used to control the movement of the three-axis motion system and control the switch and brightness of the LED ring light source

[0040] adjust;

[0041] LED ring light source is used to provide lighting for the object to be inspected;

[0042] The optical imaging system is used to obtain images of the objects to be inspected on the workbench;

[0043] The workbench is used to install the positioning fixture and place the items to be inspected;

[0044] The positioning fixture is used to fix the position of the object to be inspected.

[0045] Preferably, the optical imaging system includes an industrial control camera and an optical lens, and the LED ring light source is fixed around the optical lens. The central axes of the industrial control camera, optical lens and LED ring light source coincide to form an optical center axis, and the optical center axis coincides with the Z axis.

[0046] Preferably, the controller includes a light source controller and a motion controller, the light source controller is used to control the switching and brightness of the LED ring light source, and the motion controller is used to control the motion of the three-axis motion system.

[0047] The above-mentioned optical inspection system and its zero-point positioning detection method first prefabricate several positioning fixtures and preset a zero-point mark on one of the fixtures and record the shape and radius value of the zero-point mark, then install the several positioning fixtures on the workbench of the optical inspection system, then use the industrial control camera in the optical inspection system to take pictures to obtain a color image containing the preset zero-point mark on the fixture, then use the main control computer in the optical inspection system to recognize the obtained color image containing the preset zero-point mark on the fixture, determine the X-axis zero point position and Y-axis zero point position of the preset zero point mark on the fixture, then calculate the clarity evaluation value of the preset zero point mark on the fixture, determine the Z-axis zero point position of the preset zero point mark on the fixture according to the hill climbing algorithm, and obtain the zero point position of the optical inspection system, finally place the object to be inspected on the workbench of the optical inspection system and fix it with several positioning fixtures, and adjust the optical imaging system and the workbench in the optical inspection system to move along the X, Y, and Z axes of the three-axis motion system so that the center point position of the object to be inspected coincides with the zero point position of the optical inspection system, thereby obtaining the zero point detection position of the object to be inspected. This method uses a preset zero point mark on the detection fixture to find the optimal detection position of the object to be detected during optical detection. It does not require additional hardware and wiring, is simple and convenient, and has high positioning accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 Flowchart of a zero-point positioning detection method of an optical detection system in one embodiment of the present invention;

[0049] Figure 2 Schematic diagram of the installation position of the positioning fixture in one embodiment of the present invention;

[0050] Figure 3 Schematic diagram of determining the optimal object distance using a hill climbing algorithm in one embodiment of the present invention;

[0051] Figure 4 A schematic diagram of calculating the positional deviation between the zero mark and the image center of the object to be inspected in one embodiment of the present invention;

[0052] Figure 5 Schematic diagram of the connection relationship between a computer and other components in one embodiment of the present invention.

[0053] Description of reference numerals:

[0054] 1. Main control computer; 2. Controller; 3. Optical imaging system; 4. LED ring light source; 5. Stage; 6. Three-axis motion system; 51. Workbench; 52. Positioning fixture; 53. Positioning fixture; 54. Positioning fixture; 55. Positioning fixture; 56. Object to be inspected; 59. Zero point mark. DETAILED DESCRIPTION

[0055] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0056] In one embodiment, a zero-point positioning detection method for an optical detection system includes the following steps:

[0057] S1. Prefabricate several positioning fixtures, preset a zero mark on one of the fixtures, record the shape and radius of the zero mark, and install the several positioning fixtures on the workbench of the optical inspection system;

[0058] S2. Use the industrial control camera in the optical inspection system to take a photo and obtain a color image including the preset zero point mark on the fixture;

[0059] S3, using a main control computer in the optical detection system to recognize the acquired color image containing the preset zero point mark on the fixture, and determine the X-axis zero point position and the Y-axis zero point position of the preset zero point mark on the fixture;

[0060] S4. Calculate the clarity evaluation value of the preset zero mark on the fixture using the main control computer in the optical detection system, determine the Z-axis zero position of the preset zero mark on the fixture using a hill climbing algorithm, and obtain the zero position of the optical detection system;

[0061] S5. Place the object to be inspected on the workbench of the optical inspection system and fix it with several positioning fixtures. Adjust the optical imaging system and the workbench in the optical inspection system to move along the X, Y, and Z axes of the three-axis motion system so that the center point position of the object to be inspected coincides with the zero point position of the optical inspection system, thereby obtaining the zero point detection position of the object to be inspected.

[0062] Specifically, see Figure 1 and Figure 2 , Figure 1 Flowchart of a zero-point positioning detection method of an optical detection system in one embodiment of the present invention; Figure 2 Schematic diagram of the installation position of the positioning fixture in one embodiment of the present invention.

[0063] A zero point positioning detection method for an optical detection system, firstly, four positioning fixtures 52, 53, 54, 55 are preset, the inner side of the positioning fixture has two right-angled sides, and a zero point mark 59 is preset on one of the positioning fixtures 52, the zero point mark 59 and the positioning fixtures 52, 53, 54, 55 bodies adopt contrasting colors with large brightness differences, preferably the color of the zero point mark 59 is black, and the color of the positioning fixtures 52, 53, 54, 55 bodies is white, the zero point mark 59 can be set to a circle (or a square or other shape) with a radius of 0.5 mm, and the shape and radius value of the preset figure are recorded in the system, and the four positioning fixtures 52, 53, 54, 55 are set to the zero point mark 59. 5 is mounted on the workbench 51 of the optical inspection system. Then, an industrial control camera in the optical inspection system is used to capture a color image containing the preset zero mark on the fixture. Because this color image may contain multiple images similar to the preset zero mark on the fixture, the main control computer in the optical inspection system needs to perform zero mark recognition on the acquired color image, determine the X-axis zero position and Y-axis zero position of the preset zero mark on the fixture, calculate the clarity evaluation value of the preset zero mark on the fixture, and determine the Z-axis zero position of the preset zero mark on the fixture using a hill climbing algorithm. The three-dimensional coordinates of the preset zero mark on the fixture at this position correspond to the zero position of the optical inspection system. Based on this, the object to be inspected is fixed to the workbench 51 using positioning fixtures 52, 53, 54, and 55. By adjusting the optical imaging system and the workbench in the optical inspection system to move along the X, Y, and Z axes of the three-axis motion system, the center point position of the object to be inspected and the zero position of the optical inspection system are aligned. This results in the zero detection position of the object to be inspected, which is the optimal imaging position of the object to be inspected. This method uses a preset zero-point mark to find the optimal detection position for the object during optical inspection. This method requires no additional hardware or wiring, is simple and convenient, and offers high positioning accuracy. Furthermore, once the zero point of the optical inspection system is determined, subsequent adjustments are unnecessary; the zero-point detection position of the object can be directly determined based on this, effectively representing the optimal imaging position for the object. Sudden failures, such as power outages or malfunctions in the main control computer system, can cause the optical inspection system to misalign its positioning, necessitating a re-zero-point detection.

[0064] In one embodiment, the color image acquired in step S2 includes multiple images similar to the preset zero mark on the fixture, and step S3 recognizes the acquired color image including the preset zero mark on the fixture to determine the X-axis zero point position and the Y-axis zero point position of the preset zero point mark on the fixture, specifically including the following steps:

[0065] S31, a main control computer in the optical detection system receives and processes a color image including a preset zero point mark on the fixture, and calculates the center position and radius value of multiple similar images obtained;

[0066] S32, comparing the radius values ​​of the multiple similar images with the radius value of the preset zero mark on the fixture, and identifying the image with a radius error smaller than the preset value as the preset zero mark on the fixture;

[0067] S33. Record the center position of the preset zero point mark on the fixture as the X-axis zero point position and the Y-axis zero point position of the preset zero point mark on the fixture.

[0068] Specifically, first, a color image containing a preset zero point mark on the fixture is received by a main control computer in an optical detection system and obtained by an industrial control camera. The color image is grayscaled, histogram equalized, Gaussian blurred, threshold segmented, and circle fitted. The center positions and radius values ​​of all figures similar to the preset circles are calculated, and the radii of the obtained multiple similar figures are compared with the radius of the preset circle. The radius error value is set to 10%. Through comparison, among the multiple similar circles obtained, the circle with a radius error of less than 10% is identified as the preset zero point mark on the fixture, and the center position of the circle is recorded as the X-axis zero point position and Y-axis zero point position of the preset zero point mark on the fixture.

[0069] In one embodiment, step S4 uses a main control computer in an optical detection system to calculate the clarity evaluation value of a preset zero point mark on the fixture, which specifically includes the following steps:

[0070] S41, extracting a color image of the preset zero point mark on the fixture according to the X-axis zero point position and the Y-axis zero point position and the radius value of the preset zero point mark on the fixture;

[0071] S42, gray-scaling the color image of the preset zero point mark on the fixture to obtain a grayscale image;

[0072] S43, using the Sobel operator to calculate the gradient of the grayscale image;

[0073] S44. Calculate the average value of the gradient of the grayscale image as the clarity evaluation value of the preset zero point mark on the fixture.

[0074] Specifically, the calculation process of the clarity evaluation value of the preset zero-point mark on the fixture is as follows: first, the position and radius of the preset zero-point mark on the fixture are used to extract the color image of the zero-point mark, and then the color image is grayscaled to obtain a grayscale image. Then, the Sobel operator is used to calculate the gradient of the grayscale image, and finally, the average value of the image gradient is calculated as the clarity evaluation value of the preset zero-point mark on the fixture. The larger the evaluation value, the clearer the image.

[0075] In one embodiment, in step S4, the Z-axis zero point position of the preset zero point mark on the fixture is determined according to the hill climbing algorithm to obtain the zero point position of the optical detection system, specifically:

[0076] S45, using a controller in the optical detection system to drive the three-axis motion system to move, so that the optical imaging system fixed on the Z axis moves along a single direction on the Z axis with a preset motion step length;

[0077] S46. The optical imaging system obtains an image clarity evaluation value every time it moves a motion step, and records the maximum value of the motion steps of the optical imaging system on the Z axis and the currently obtained image clarity evaluation value;

[0078] S47. Repeat step S46 until a maximum point in the image clarity evaluation value is found. This maximum point corresponds to the Z-axis zero position of the preset zero point mark on the fixture. The three-dimensional coordinates of the preset zero point mark on the fixture at this position are used as the zero position of the optical detection system.

[0079] Specifically, see Figure 3 , Figure 3 FIG. 1 is a schematic diagram of determining the optimal object distance using a hill climbing algorithm in one embodiment of the present invention.

[0080] The principle of using the hill climbing algorithm to obtain the optimal object distance is that when the object distance of the industrial control camera changes, the resulting image clarity curve has a single peak and monotonic characteristics, similar to a parabola. The extreme point of the curve corresponds to the position where the industrial control camera image is clearest. When leaving this position, whether in the forward or reverse direction, the clarity curve shows a monotonically decreasing trend.

[0081] The process of using the hill climbing algorithm to obtain the Z-axis zero point position (i.e., the optimal object distance) of the preset zero point mark on the fixture is as follows: the motion controller in the optical motion system drives the optical imaging system fixed on the Z-axis of the three-axis motion system to move in a single direction on the Z-axis with a preset motion step length, and the image clarity evaluation value climbs along the direction shown by A→B→C→Peak→D→E. The image clarity evaluation value is obtained every time the optical imaging system moves one step, and the maximum value of the number of motion steps of the optical imaging system on the Z-axis and the currently obtained image clarity evaluation value is recorded. As the optical imaging system continues to move on the Z-axis, if two consecutive steps are reached, the image clarity evaluation value is obtained. If the secondary clarity evaluation value is less than the currently recorded maximum image clarity evaluation value, it is considered that the optical imaging system has crossed the optimal object distance position. When it crosses the Peak point and reaches point E, since the clarity evaluation values ​​of positions D and E are both less than the clarity evaluation value of the Peak position, the Peak point position is the optimal object distance position. According to the recorded number of moving steps (E is two steps away from the Peak), the controller drives the three-axis motion system to make the optical imaging system move in the opposite direction to the Peak point position. This maximum point corresponds to the Z-axis zero point position of the preset zero point mark on the fixture, and the three-dimensional coordinates of the zero point mark at this position are used as the zero point position of the optical detection system.

[0082] In one embodiment, step S5 specifically includes:

[0083] S51. Place the object to be inspected on the workbench of the optical inspection system, using the inner corner of a positioning fixture with a preset zero point mark as a reference, so that the corners of the object to be inspected and the inner corners of the positioning fixture with a preset zero point mark coincide with each other, with the surface to be inspected facing the industrial control camera;

[0084] S52, turning on the LED ring light source and adjusting the brightness through a controller in the optical inspection system to obtain an image of the object to be inspected taken by the industrial control camera;

[0085] S53, calculating the height of the object to be inspected in the Z-axis direction in the optical inspection system based on the height of the positioning fixture and the height of the object to be inspected, thereby calculating the number of steps the optical imaging system needs to move in the Z-axis, and controlling the optical imaging system to move the corresponding number of steps to reach the corresponding position on the Z-axis through the controller;

[0086] S54. Obtain the X-axis and Y-axis position coordinates of the preset zero point mark on the fixture at this time through the main control computer in the optical detection system, calculate the deviation between the X-axis and Y-axis position coordinates of the preset zero point mark on the fixture and the X-axis and Y-axis position coordinates of the center of the image of the object to be detected, drive the X-axis and Y-axis of the three-axis motion system through the controller, and move the workbench along the X-axis and Y-axis so that the center point position of the object to be detected coincides with the zero point position of the optical detection system. The position of the object to be detected at this time is the zero point detection position of the object to be detected.

[0087] Specifically, the process of confirming the zero-point detection position of the object to be detected is as follows:

[0088] 1) Place the object to be inspected on the workbench of the optical inspection system, using the inner corner of the positioning fixture with a zero point mark as a reference, so that the corners of the object to be inspected and the inner corners of the positioning fixture with a zero point mark coincide with each other, with the surface to be inspected facing the industrial control camera;

[0089] 2) Turn on the LED ring light source and adjust the brightness through the controller in the optical detection system;

[0090] 3) Calculating the height of the object to be inspected in the Z-axis direction of the optical inspection system based on the height of the positioning fixture and the height of the object to be inspected, thereby calculating the number of steps the optical imaging system needs to move in the Z-axis, and controlling the optical imaging system to move the corresponding number of steps to the corresponding Z-axis position through the controller;

[0091] For example, the motion step length is set to 0.1mm, the positioning fixture height is 2mm, and the chip to be tested height is 5mm. Since the positioning fixture and the chip to be tested are both located on the workbench of the optical detection system, relative to the zero position of the optical detection system, the Z-axis height of the chip to be tested is 3mm. Through the preset motion step length of 0.1mm, it can be calculated that the optical imaging system needs to move 30 steps upward on the Z-axis. At this time, the controller controls the optical imaging system to move 30 steps to the corresponding position.

[0092] 4) The main control computer in the optical inspection system calculates the deviation between the center coordinates of the preset zero point mark on the fixture and the center coordinates of the image of the object to be inspected. The controller drives the X and Y axes of the three-axis motion system so that the center point position of the object to be inspected coincides with the zero point position of the optical inspection system. At this time, the position of the object to be inspected is the zero point detection position of the object to be inspected, and the industrial control camera can obtain the clearest image of the object to be inspected.

[0093] In one embodiment, in step S54, the deviations between the X-axis and Y-axis position coordinates of the preset zero mark on the fixture and the X-axis and Y-axis position coordinates of the center of the image of the object to be inspected are calculated as follows:

[0094] S541. Set the preset zero point mark on the fixture as point A, set the point where the two right-angled sides on the inner side of the positioning fixture with the preset zero point mark as point B, mark the center point of the object to be inspected as point C, set the distance from point A to point B as L1, and the distance from point B to point C as L2;

[0095] S542. Draw a rectangle with the line connecting points A and B as the diagonal line. By measuring, the length L1 in the X direction can be obtained. 1x and the length L in the Y direction 1y ;

[0096] S543. The dimensions of the object to be tested can be obtained from the product data, and the distance L2 in the X direction can be obtained from the dimensions. 2x and the distance L in the Y direction 2y ;

[0097] S544, by performing the L obtained in step S542 1x and L obtained in step S543 2x Sum the distance from point C to point A in the X direction, which is the deviation between the X-axis position coordinate of the preset zero point mark on the fixture and the X-axis position coordinate of the center of the image of the object to be inspected;

[0098] S545, by performing the L obtained in step S542 1y and L obtained in step S543 2yThe sum is calculated to obtain the distance from point C to point A in the Y direction, which is the deviation between the Y-axis position coordinates of the preset zero point mark on the fixture and the Y-axis position coordinates of the center of the image of the object to be inspected.

[0099] Specifically, see Figure 4 , Figure 4 Schematic diagram of calculating the positional deviation between the zero mark and the image center of the object to be inspected in one embodiment of the present invention.

[0100] First, set the preset zero point mark on the fixture as point A, set the point where the two right-angled sides on the inner side of the positioning fixture with the preset zero point mark as point B, mark the center point of the object to be detected as point C, set the distance from point A to point B as L1, and the distance from point B to point C as L2; ​​then draw a rectangle with the line connecting points A and B as the diagonal line, and the length L1 in the X direction can be obtained by measurement. 1x and the length L in the Y direction 1y Then, we can find out the dimensions of the object to be tested according to the product manual (or we can get it by measurement). Let the length of the object to be tested be a and the width be b, and we can get the distance L2 in the X direction. 2x =a / 2, the distance L in the Y direction 2y =b / 2; finally, the obtained L 1x and L 2x By summing, we can get the distance from point C to point A in the X direction, that is, the deviation between the X axis of the preset zero point mark on the fixture and the X axis position coordinate of the center of the image of the object to be detected; by calculating the obtained L 1y and L 2y The sum of these values ​​gives the Y-axis distance from point C to point A, which is the deviation between the Y-axis coordinates of the zero mark on the fixture and the Y-axis coordinates of the center of the image of the object being inspected. It should be noted that multiple objects can also be placed on a dedicated tray for inspection. The deviation calculation also needs to take the tray size into account. The specific calculation method is not detailed here.

[0101] In one embodiment, the plurality of positioning fixtures prefabricated in step S1 are all provided with screw mounting holes, and the plurality of positioning fixtures are detachably mounted on a workbench in the optical detection system.

[0102] Specifically, the positioning fixture 52 with a zero point mark 59 is fixed to the lower left of the workbench 51 by screws, and the remaining positioning fixtures 53, 54, and 55 are installed at several other corners of the workbench 51 by screws. When fixing the objects to be inspected, it is only necessary to adjust the positioning fixtures 53, 54, and 55 to meet the optical inspection of objects of different sizes or multiple objects to be inspected.

[0103] In one embodiment, an optical inspection system using a zero-point positioning inspection method includes an open-loop stepper motor, a three-axis motion system, a main control computer, a controller, an optical imaging system, an LED ring light source, a workbench, and several positioning fixtures, one of which is provided with a zero-point positioning mark.

[0104] The open-loop stepper motor is electrically connected to the three-axis motion system, the main control computer is electrically connected to the optical imaging system, one end of the controller is electrically connected to the main control computer, and the other end is electrically connected to the three-axis motion system and the LED ring light source respectively. The workbench is located on the support surface of the three-axis motion system. The plane defined by the X-axis and Y-axis of 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 coincides with the Z-axis of the three-axis motion system. The positioning fixture is installed on the workbench, wherein:

[0105] Open-loop stepper motors are used to power the three-axis motion system;

[0106] Controller, used to control the movement of the three-axis motion system and control the switching and brightness adjustment of the LED ring light source;

[0107] LED ring light source is used to provide lighting for the object to be inspected;

[0108] The optical imaging system is used to obtain images of the objects to be inspected on the workbench;

[0109] The workbench is used to install the positioning fixture and place the items to be inspected;

[0110] The positioning fixture is used to fix the position of the object to be inspected.

[0111] As a further improvement of this embodiment, the optical imaging system includes an industrial control camera and an optical lens, and an LED ring light source is fixed around the optical lens. The central axes of the industrial control camera, optical lens and LED ring light source coincide to form an optical center axis, and the optical center axis coincides with the Z axis.

[0112] As another improvement of this embodiment, the controller includes a light source controller and a motion controller. The light source controller is used to control the switching and brightness of the LED ring light source, and the motion controller is used to control the motion of the three-axis motion system.

[0113] Specifically, see Figure 2 and Figure 5 , Figure 2 Schematic diagram of the installation position of the positioning fixture in one embodiment of the present invention. Figure 5 Schematic diagram of the connection relationship between a computer and other components in one embodiment of the present invention.

[0114] The optical detection system includes an open-loop stepper motor, a main control computer 1, a controller 2, an optical imaging system 3, an LED ring light source 4, a stage ( Figure 5 (not shown) and a three-axis motion system 6, the main control computer 1 is electrically connected to the controller 2 and the optical imaging system 3, the controller 2 is electrically connected to the three-axis motion system 6 and the LED ring light source 4; the stage is located on a support surface in the three-axis motion system 6, the plane defined by the X-axis and Y-axis in the three-axis motion system 6 is parallel to the surface of the stage, and the Z-axis in the three-axis motion system 6 coincides with the central axis of the optical imaging system 3;

[0115] Furthermore, the optical imaging system 3 includes a high-resolution industrial control camera and an optical lens. The main control computer is connected to the industrial control camera in the optical imaging system 3 via Ethernet, and is used to set the working parameters of the industrial control camera and obtain the captured images. The LED ring light source 4 is fixed around the optical lens. The central axes of the industrial control camera, optical lens and LED ring light source coincide with each other, which is called the optical center axis.

[0116] Furthermore, the controller 2 includes a light source controller and a motion controller. The main control computer 1 is connected to the light source controller and the motion controller via a USB interface. The light source controller is used to control the switch and brightness of the LED ring light source 4, and the motion controller is used to control the movement of the three-axis motion system.

[0117] Furthermore, the stage includes a workbench 51 and positioning fixtures 52, 53, 54, and 55. The object to be inspected (such as a single chip or a tray for storing multiple chips) is placed on the workbench 51, and one corner of the object to be inspected is fixed tightly against the corner of the positioning fixture 52, and the surface to be inspected is facing the optical imaging system 3. Depending on actual needs, the remaining positioning fixtures 53, 54, and 55 are used to fix other parts of the object to be inspected.

[0118] The above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art who is familiar with the technical field can easily think of changes or replacements within the technical scope disclosed by the present invention, which should be included in the scope of protection of the present invention. In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention. Therefore, the scope of protection of the present invention shall be based on the scope of protection of the claims.

Claims

1. A zero point positioning detection method for an optical detection system, characterized in that: The method comprises the following steps: S1. Prefabricate several positioning fixtures, preset a zero mark on one of the fixtures, record the shape and radius of the zero mark, and install the several positioning fixtures on a workbench of an optical detection system; S2, taking a photo using an industrial control camera in an optical inspection system to obtain a color image including a preset zero point mark on the fixture; S3, using a main control computer in an optical detection system to recognize the acquired color image containing the preset zero point mark on the fixture, and determine the X-axis zero point position and the Y-axis zero point position of the preset zero point mark on the fixture; S4. Calculate the clarity evaluation value of the preset zero mark on the fixture using a main control computer in the optical detection system, determine the Z-axis zero position of the preset zero mark on the fixture using a hill climbing algorithm, and obtain the zero position of the optical detection system; S5. Placing the object to be inspected on a workbench of the optical inspection system and securing it using the plurality of positioning fixtures, and adjusting the optical imaging system and the workbench in the optical inspection system to move along the X, Y, and Z axes of the three-axis motion system so that the center position of the object to be inspected coincides with the zero point position of the optical inspection system, thereby obtaining a zero point inspection position for the object to be inspected; The color image acquired in step S2 includes a plurality of images similar to the preset zero mark on the fixture, and step S3 recognizes the acquired color image including the preset zero mark on the fixture to determine the X-axis zero point position and the Y-axis zero point position of the preset zero point mark on the fixture, specifically comprising the following steps: S31, a main control computer in the optical detection system receives and processes the color image including the preset zero point mark on the fixture, and calculates the center position and radius value of multiple similar images obtained; S32, comparing the radius values ​​of the multiple similar images with the radius value of a preset zero mark on the fixture, and identifying an image with a radius error smaller than the preset value as the preset zero mark on the fixture; S33. Record the center position of the preset zero point mark on the fixture as the X-axis zero point position and the Y-axis zero point position of the preset zero point mark on the fixture.

2. The zero-point positioning detection method of the optical detection system according to claim 1, characterized in that: In step S4, the main control computer in the optical detection system is used to calculate the clarity evaluation value of the preset zero point mark on the fixture, which specifically includes the following steps: S41, extracting a color image of the preset zero point mark on the fixture according to the X-axis zero point position and the Y-axis zero point position and the radius value of the preset zero point mark on the fixture; S42, gray-scaling the color image of the preset zero point mark on the fixture to obtain a grayscale image; S43, using a Sobel operator to calculate the gradient of the grayscale image; S44. Calculate the average value of the gradient of the grayscale image as the clarity evaluation value of the preset zero point mark on the fixture.

3. The zero-point positioning detection method of the optical detection system according to claim 2, characterized in that: In step S4, the Z-axis zero point position of the preset zero point mark on the fixture is determined according to the hill climbing algorithm to obtain the zero point position of the optical detection system, specifically: S45, using a controller in the optical detection system to drive the three-axis motion system to move, so that the optical imaging system fixed on the Z axis moves along a single direction on the Z axis with a preset motion step length; S46. The optical imaging system obtains an image clarity evaluation value every time it moves a motion step, and records the maximum value of the motion steps of the optical imaging system on the Z axis and the currently obtained image clarity evaluation value; S47. Repeat step S46 until a maximum point in the image clarity evaluation value is found. This maximum point corresponds to the Z-axis zero position of the preset zero point mark on the fixture. The three-dimensional coordinates of the preset zero point mark on the fixture at this position are used as the zero position of the optical detection system.

4. The zero-point positioning detection method of the optical detection system according to claim 3, characterized in that: The step S5 specifically includes: S51. Place the object to be inspected on the workbench of the optical inspection system, using the inner corner of a positioning fixture with a preset zero point mark as a reference, so that the corners of the object to be inspected and the inner corners of the positioning fixture with a preset zero point mark coincide with each other, with the surface to be inspected facing the industrial control camera; S52, turning on the LED ring light source and adjusting the brightness through a controller in the optical inspection system to obtain an image of the object to be inspected taken by the industrial control camera; S53, calculating the height of the object to be inspected in the Z-axis direction in the optical inspection system based on the height of the positioning fixture and the height of the object to be inspected, thereby calculating the number of steps the optical imaging system needs to move in the Z-axis, and controlling the optical imaging system to move the corresponding number of steps to reach the corresponding position on the Z-axis through the controller; S54. Obtain the X-axis and Y-axis position coordinates of the preset zero point mark on the fixture at this time through the main control computer in the optical detection system, calculate the deviation between the X-axis and Y-axis position coordinates of the preset zero point mark on the fixture and the X-axis and Y-axis position coordinates of the center of the image of the object to be detected, drive the X-axis and Y-axis of the three-axis motion system through the controller, and move the workbench along the X-axis and Y-axis so that the center point position of the object to be detected coincides with the zero point position of the optical detection system. The position of the object to be detected at this time is the zero point detection position of the object to be detected.

5. The zero point positioning detection method of the optical detection system according to claim 4, characterized in that: In step S54, the deviations between the X-axis and Y-axis position coordinates of the preset zero point mark on the fixture and the X-axis and Y-axis position coordinates of the center of the image of the object to be inspected are calculated. The specific calculation method is as follows: S541. Set the preset zero point mark on the fixture as point A, set the point where the two right-angled sides on the inner side of the positioning fixture with the preset zero point mark as point B, mark the center point of the object to be inspected as point C, set the distance from point A to point B as L1, and the distance from point B to point C as L2; S542. Draw a rectangle with the line connecting points A and B as the diagonal line. By measuring, the length L1 in the X direction can be obtained. 1x and the length L in the Y direction 1y ; S543. The dimensions of the object to be tested can be obtained from the product data, and the distance L2 in the X direction can be obtained from the dimensions. 2x and the distance L in the Y direction 2y ; S544, by performing the L obtained in step S542 1x and L obtained in step S543 2x Sum the distance from point C to point A in the X direction, which is the deviation between the X-axis position coordinate of the preset zero point mark on the fixture and the X-axis position coordinate of the center of the image of the object to be inspected; S545, by performing the L obtained in step S542 1y and L obtained in step S543 2y The sum is calculated to obtain the distance from point C to point A in the Y direction, which is the deviation between the Y-axis position coordinates of the preset zero point mark on the fixture and the Y-axis position coordinates of the center of the image of the object to be inspected.

6. The zero-point positioning detection method of the optical detection system according to claim 1, wherein: The pre-positioning fixtures in step S1 are all provided with screw mounting holes, and a plurality of the positioning fixtures are detachably mounted on a workbench in the optical detection system.

7. An optical detection system, characterized in that: The zero-point positioning detection is performed using the method according to any one of claims 1 to 6, wherein the optical detection system comprises an open-loop stepper motor, a three-axis motion system, a main control computer, a controller, an optical imaging system, an LED ring 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 stepper motor is electrically connected to the three-axis motion system, the main control computer is electrically connected to the optical imaging system, one end of the controller is electrically connected to the main control computer, and the other end is electrically connected to the three-axis motion system and the LED ring light source respectively. The workbench is located on the support surface of the three-axis motion system, the plane defined by the X-axis and Y-axis of 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 coincides with the Z-axis of the three-axis motion system, and the positioning fixture is installed on the workbench, wherein: Open-loop stepper motors are used to power the three-axis motion system; Controller, used to control the movement of the three-axis motion system and control the switching and brightness adjustment of the LED ring light source; LED ring light source is used to provide lighting for the object to be inspected; The optical imaging system is used to obtain images of the objects to be inspected on the workbench; The workbench is used to install the positioning fixture and place the items to be inspected; The positioning fixture is used to fix the position of the object to be inspected.

8. The optical detection system according to claim 7, wherein: The optical imaging system includes an industrial control camera and an optical lens. The LED ring light source is fixed around the optical lens. The central axes of the industrial control camera, the optical lens and the LED ring light source coincide to form an optical center axis. The optical center axis coincides with the Z axis.

9. The optical detection system according to claim 7, wherein: The controller includes a light source controller and a motion controller. The light source controller is used to control the switch and brightness of the LED ring light source, and the motion controller is used to control the motion of the three-axis motion system.

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