A calibration method, a calibration device and a calibration system

Abstract

The present invention discloses a calibration method, a calibration device and a calibration system, which are used for position calibration of a visual inspection system. The calibration device comprises a laser module, which is lit up, and a light beam is imaged on an imaging plate through a Fresnel lens, and an industrial camera is controlled to complete a first photographing, and the industrial camera is controlled to complete a second photographing by rotating an angle; the pixel coordinates of the laser imaging points of the two photographing are calculated, so as to calculate the relationship between the angle and the pixel. The present invention solves the position calculation error caused by the installation distance error and the lens focal length error of the visual inspection system, and by using one calibration system to perform position calibration on multiple visual inspection systems, the detection consistency and measurement accuracy of each visual inspection system can be guaranteed.

Description

Technical Field

[0001] The present invention relates to the field of visual inspection applications, and in particular to a calibration method, a calibration device and a calibration system. Technical Background

[0002] During the optical testing of vehicle lights, according to regulations, the lighting performance of the headlights needs to be measured on a vertical lighting screen 25m away from the reference center of the headlights. In actual production, a lens is used to control the distance to about 1m to simulate imaging at a distance of 25m, and visual inspection methods are used to reduce the production line footprint and improve testing efficiency.

[0003] The position information in the headlight distribution report uses angle units, while the camera uses pixel units. We need to find the correspondence between angles and pixels.

[0004] Due to the processing errors and installation errors of the equipment, there will be errors between the distance from the headlight to the lens, and the distance from the lens to the imaging board and the design values. In addition, there is an error in the focal length of the lens itself. If the design values ​​are used for theoretical calculations, there will be large errors with the actual situation, and it is difficult to ensure the consistency of detection of each device. Summary of the invention

[0005] In order to find the correspondence between angles and pixels, that is, to calculate the number of pixel points within an angle unit, the present invention provides a calibration method, which solves the problem of errors in calculating the correspondence between the angles and pixels of a visual inspection system using theoretical values. The present invention can improve the accuracy of the inspection results of the visual inspection system and improve the consistency of the inspection results of multiple visual inspection systems.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A calibration method, the method comprising:

[0008] S1 lights up the laser module, and then the laser module moves to position A, and a point P1 is obtained on the imaging board, and the industrial camera is controlled to complete the first photo shooting. Then the laser module rotates by an angle θ to position B, and a point P2 is obtained on the imaging board, and the industrial camera is controlled to complete the second photo shooting.

[0009] S2 obtains two images taken by the industrial camera;

[0010] S3 processes the two images obtained and calculates the pixel coordinates of P1 and P2. The pixel coordinates of point P1 are marked as (Pix P1 , Fix P1 ), the pixel coordinates of point P2 are marked as (Pix P2 , FixP2 );

[0011] S4 calculates the number P of pixels within the angle unit.

[0012] Furthermore, the angle unit of the visual detection system is set to 1%, 1%=arctan(0.01)=0.572939 degrees.

[0013] Furthermore, if the laser module is rotated horizontally, the number of pixels P within the angle unit is calculated as follows: If the laser module is rotated vertically, the number of pixels P within the angle unit is calculated as follows:

[0014] Furthermore, the method for calculating the pixel coordinates of P1 and P2 includes:

[0015] a. Convert the two acquired images into grayscale images;

[0016] b. Perform threshold processing on the grayscale image to obtain a two-dimensional image;

[0017] c. Perform area filtering on the two-dimensional image to remove unnecessary parts;

[0018] d. dilate the image;

[0019] e. Use Gaussian line finding;

[0020] f. Merge the found lines;

[0021] g. Filter the found lines;

[0022] h. Determine whether the found lines are two lines;

[0023] i. If the found lines are two lines, continue to calculate the pixel coordinates of points P1 and P2.

[0024] In order to find the correspondence between angles and pixels, that is, to calculate the number of pixel points within an angle unit, the present invention provides a calibration device, which solves the problem of errors in calculating the correspondence between angles and pixels of a visual inspection system using theoretical values. The present invention can improve the accuracy of the inspection results of the visual inspection system and improve the consistency of the inspection results of multiple visual inspection systems.

[0025] A calibration device comprises a laser module and an imaging plate, wherein a lens is arranged between the laser module and the imaging plate, the laser module comprises a laser generator and a rotating seat, the laser generator is fixed on the rotating seat, the rotating seat is rotatably mounted on a fixed seat, a motor is fixed on the fixed seat, and the rotating seat is driven to deflect by the motor.

[0026] Furthermore, the calibration device also includes:

[0027] An industrial camera, wherein the industrial camera is used to capture images on an imaging plate;

[0028] An industrial computer is connected to the industrial camera to process and calculate the images taken by the industrial camera.

[0029] Furthermore, the calibration device also includes a support rod supporting the fixing seat and a bearing plate fixedly mounted on the support rod, and the bearing plate is detachably mounted on the detection platform.

[0030] Furthermore, the lens is a Fresnel lens. In an initial state, the center point of the Fresnel lens is on a horizontal line with the axis of the laser generator. The distance between the center of the Fresnel lens and the light-emitting point of the laser generator is 350 mm. The distance between the center of the Fresnel lens and the center of the imaging plate is 700 mm.

[0031] In order to find the correspondence between angles and pixels, that is, to calculate the number of pixel points within an angle unit, the present invention provides a calibration system, which solves the problem of errors in calculating the correspondence between angles and pixels of a visual inspection system using theoretical values. The present invention can improve the accuracy of the inspection results of the visual inspection system and improve the consistency of the inspection results of multiple visual inspection systems.

[0032] A calibration system, the device comprising:

[0033] An image generation module, used for imaging twice on an imaging plate of a calibration system;

[0034] An image acquisition module, for acquiring the two images;

[0035] An image processing module performs image processing on the two acquired images and calculates the pixel coordinates of the imaging points in the two images;

[0036] The calculation module calculates the number P of pixels within the angle unit.

[0037] Furthermore, the two imagings are performed to obtain the point P1 and the point P2 respectively, and the pixel coordinates of the point P1 and the point P2 are calculated. The pixel coordinates of the point P1 are indicated as (Pix P1 , Fix P1 ), the pixel coordinates of point P2 are marked as (Pix P2 , Fix P2 ), and then calculate the number of pixels P within the angle unit. The method for calculating the number of pixels P within the angle unit is: or

[0038] Compared with the prior art, the present invention has the following beneficial effects: the present invention uses a calibration system to calibrate the visual inspection system and finds the relationship between the angle and the pixel of the visual inspection system, thereby solving the problem in the prior art that the relationship between the angle and the pixel is calculated theoretically, which may have a large error compared with the actual situation. The present invention can eliminate the measurement error of the visual inspection system, ensure the inspection consistency of each visual inspection system, and improve the test accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A flow chart of a calibration method provided by an embodiment of the present invention;

[0040] Figure 2 A principle block diagram of a calibration system provided by an embodiment of the present invention;

[0041] Figure 3 A top view of a calibration system provided in an embodiment of the present invention. Specific embodiments

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] Figure 1 A flow chart of a calibration method provided by an embodiment of the present invention is shown. This embodiment provides a calibration method for calibrating the position of a vehicle light visual inspection system. By calculating the correspondence between the angle of the visual inspection system and the pixel, the actual pixel coordinates in the image corresponding to the test points in the national standard GB25991-2010 can be accurately found when measuring vehicle lights, thereby solving the problem of errors in the correspondence between the angle of the visual inspection system and the pixel when using theoretical value technology. The present invention can improve the accuracy of the inspection results of the visual inspection system and improve the consistency of the inspection results of multiple visual inspection systems.

[0044] Specifically, the method includes:

[0045] S1 lights up the laser module 23, and then the industrial computer 12 controls the motor 21 to drive the laser module 23 to rotate to position A. The laser beam passes through the Fresnel lens 13 to form an image on the imaging plate 14, and a point P1 is obtained on the imaging plate 14. The industrial camera 11 is controlled to complete the first photo shooting. Then the industrial computer 12 controls the motor 21 to drive the laser module 23 to rotate by an angle θ to position B. At this time, a point P2 is obtained on the imaging plate 14, and the industrial camera 11 is controlled to take the second photo shooting.

[0046] S2 obtains two images taken by the camera 11;

[0047] S3 processes the two images acquired respectively and calculates the pixel coordinates of P1 and P2. The pixel coordinates of point P1 are marked as (Pix P1 , Fix P1 ), the pixel coordinates of point P2 are marked as (Pix P2 , Fix P2 );

[0048] S4 then calculates the number P of pixels within the angle unit;

[0049] Furthermore, the angle unit of the visual inspection system is set to 1%, 1%=arctan(0.01)=0.572939 degrees.

[0050] Furthermore, if the laser module 23 rotates horizontally, the relationship between the angle and the pixel is calculated as follows: If the laser module 23 is rotated vertically, the relationship between the angle and the pixel is calculated as follows:

[0051] Furthermore, the method of calculating the pixel coordinates of P1 and P2 includes:

[0052] a. Convert the two acquired images into grayscale images;

[0053] b. Perform threshold processing on the grayscale image to obtain a two-dimensional image;

[0054] c. Perform area filtering on the two-dimensional image to remove unnecessary parts;

[0055] d. dilate the image;

[0056] e. Use Gaussian line finding;

[0057] f. Merge the found lines;

[0058] g. Filter the found lines;

[0059] h. Determine whether the found lines are two lines;

[0060] i. If the found lines are two lines, continue to calculate the pixel coordinates of points P1 and P2.

[0061] The present invention also provides a calibration device, which is used to calibrate the visual detection system. Figure 2 and Figure 3As shown, the calibration device includes a laser module 23 and an imaging plate 14, a lens 13 is provided between the laser module 23 and the imaging plate 14, the laser module 23 includes a laser generator and a rotating seat, the laser generator is fixed on the rotating seat, the rotating seat is rotatably mounted on the fixed seat, the motor 21 is fixed on the fixed seat, and the rotating seat is driven to deflect by the motor 21.

[0062] Furthermore, the calibration device also includes:

[0063] An industrial camera 11, the industrial camera 11 is used to capture an image on an imaging plate 14;

[0064] The industrial computer 12 is connected to the industrial camera 11 to process and calculate the images taken by the industrial camera 11.

[0065] Furthermore, the calibration device also includes a support rod supporting the fixed seat and a bearing plate 24 fixedly mounting the support rod, and the bearing plate 24 is detachably mounted on the visual inspection system, that is, on the inspection table.

[0066] Furthermore, the lens 13 is a Fresnel lens 13. In the initial state, the center point of the Fresnel lens 13 is on the same horizontal line as the axis of the laser generator. The distance between the center of the Fresnel lens 13 and the light-emitting point of the laser generator is 350 mm. The distance between the center of the Fresnel lens 13 and the center of the imaging plate 14 is 700 mm.

[0067] Furthermore, the visual inspection system includes a power supply 10, which supplies power to the calibration device. Specifically, the power supply 10 has a single output and active PFC regulation. The model of the power supply 10 is RSP-100-24, and its function is to output 24V voltage to power the calibration system and the industrial camera 11. The power supply 10 has the characteristics of short circuit, overload, overvoltage, and over-temperature protection.

[0068] Furthermore, the model of the industrial camera 11 is Mer-200-14gc, and its function is to collect images. The industrial camera 11 has the advantages of high resolution, high definition, low noise, small size, and easy installation.

[0069] Furthermore, the model of the industrial computer 12 is IPC-7120, and its function is to serve as the overall controller of the system, run the software, control the motor 21 and process the image.

[0070] Furthermore, the calibration device also includes a step-down module 22, the step-down module 22 is electrically connected to the power supply 10, and the laser module 23 is electrically connected to the step-down module 22. Specifically, the step-down module 22 adopts the model LM2596. The step-down module 22 has the advantages of wide voltage input, adjustable output, small size, and low cost. Its function is to supply power to the laser module 23. By adjusting the output voltage of the step-down module 22, the brightness of the laser module 23 can be adjusted.

[0071] Furthermore, the motor 21 is a serial control drive integrated stepper motor 21. The model of the motor 21 is VSMD102025T. Its function is to provide a standard input angle for the position calibration system. The motor 21 has the advantages of small size, simple wiring, and easy control.

[0072] Furthermore, the laser generator is a cross laser generator, the input voltage of the cross laser generator is 3-5V, the model of the cross laser generator is TZL2090, and its function is to produce a cross light shape on the imaging plate 14 through the Fresnel lens 13, and calculate the intersection position coordinates of the two lines, that is, the pixel coordinates.

[0073] The present invention also provides a calibration system, which is applied to the above-mentioned calibration device. Specifically, the system includes:

[0074] An image generation module, used for imaging twice on an imaging plate 14 of a calibration system;

[0075] An image acquisition module, acquiring two images;

[0076] An image processing module performs image processing on the two acquired images and calculates the pixel coordinates of the imaging points in the two images;

[0077] The calculation module calculates the number of pixels P within the angle unit.

[0078] Furthermore, the two imagings are performed to obtain the point P1 and the point P2 respectively, and the pixel coordinates of the point P1 and the point P2 are calculated. The pixel coordinates of the point P1 are indicated as (Pix P1 , Fix P1 ), the pixel coordinates of point P2 are marked as (Pix P2 , Fix P2 ), and then calculate the number of pixels P within the angle unit. The method for calculating the number of pixels P within the angle unit is: or

[0079] The present invention also provides a method for position calibration operation of a visual inspection system, which is as follows:

[0080] Connect the above calibration system to the visual inspection system, then open the system software in the industrial computer 12, then open the calibration interface, and click the one-click calibration button to obtain the relationship between the angle and the pixel.

[0081] In summary, the calibration method, calibration device and calibration system provided by the present invention calculate the relationship between the angle and pixels of the visual detection system, and then when measuring the object to be measured, calculate the position information of the test point of the actual object to be measured based on the relationship between the angle and the pixel, so as to eliminate the measurement error of the visual detection system. After each visual detection system is calibrated, the detection consistency of each visual detection system can be guaranteed, thereby improving the accuracy of the test results.

[0082] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A calibration method, characterized in that: The method comprises: S1 lights up the laser module, which is installed on the visual inspection system. Then the laser module moves to position A, and point P1 is obtained on the imaging board, which controls the industrial camera to complete the first photo. Then the laser module rotates by an angle θ to position B, and point P2 is obtained on the imaging board, which controls the industrial camera to complete the second photo. S2 obtains two images taken by the industrial camera; S3 processes the two images obtained and calculates the pixel coordinates of P1 and P2. The pixel coordinates of point P1 are marked as (Pix P1 , Fix P1 ), the pixel coordinates of point P2 are marked as (Pix P2 , Fix P2 ); S4 calculates the number P of pixels within the angle unit; The angle unit of the visual inspection system is set to 1%, 1% = arctan (0.01) = 0.572939 degrees; The S4 calculates the number of pixels P within the angle unit. Specifically, the laser module rotates horizontally. Then, the method for calculating the number of pixels P within the angle unit is: If the laser module is rotated vertically, the number of pixels P within the angle unit is calculated as follows:

2. The calibration method according to claim 1, characterized in that: The method for calculating the pixel coordinates of P1 and P2 includes: a. Convert the two acquired images into grayscale images; b. Perform threshold processing on the grayscale image to obtain a two-dimensional image; c. Perform area filtering on the two-dimensional image to remove unnecessary parts; d. dilate the image; e. Use Gaussian line finding; f. Merge the found lines; g. Filter the found lines; h. Determine whether the found lines are two lines; i. If the found lines are two lines, continue to calculate the pixel coordinates of points P1 and P2.

3. A calibration device based on the calibration method according to claim 1 or 2, characterized in that: It comprises a laser module and an imaging plate, a lens is arranged between the laser module and the imaging plate, the laser module comprises a laser generator and a rotating seat, the laser generator is fixed on the rotating seat, the rotating seat is rotatably mounted on the fixed seat, a motor is fixed on the fixed seat, and the rotating seat is driven to deflect by the motor; The calibration device also includes: An industrial camera, wherein the industrial camera is used to capture images on an imaging plate; An industrial computer is connected to the industrial camera to process and calculate the images taken by the industrial camera.

4. The calibration device according to claim 3, characterized in that: The calibration device further comprises a support rod for supporting the fixing seat and a bearing plate for fixing the support rod, and the bearing plate is detachably mounted on the detection platform.

5. The calibration device according to claim 4, characterized in that: The lens is a Fresnel lens. In an initial state, the center point of the Fresnel lens is on a horizontal line with the axis of the laser generator. The distance between the center of the Fresnel lens and the light-emitting point of the laser generator is 350 mm, and the distance between the center of the Fresnel lens and the center of the imaging plate is 700 mm.

6. A calibration system, characterized in that: include: An image generation module, used for imaging twice on an imaging plate of a calibration system; An image acquisition module is used to acquire the two images; the module includes lighting a laser module installed on the visual inspection system, first controlling the laser module to rotate to position A, and the laser beam is imaged on the imaging board to obtain point P1, and then controlling the laser module to rotate by an angle θ to reach position B, and then obtaining point P2 on the imaging board; An image processing module performs image processing on the two acquired images and calculates the pixel coordinates of the imaging points in the two images; A calculation module calculates the number of pixels P within an angle unit; The two imagings are used to obtain the points P1 and P2 respectively. The pixel coordinates of the points P1 and P2 are calculated. The pixel coordinates of the point P1 are marked as (Pix P1 , Fix P1 ), the pixel coordinates of point P2 are marked as (Pix P2 , Fix P2 ), and then calculate the number of pixels P in the angle unit. The method for calculating the number of pixels P in the angle unit is: set the angle unit of the visual inspection system to 1%, 1% = arctan (0.01) = 0.572939 degrees; When the laser module rotates horizontally, the number of pixels P within the angle unit is calculated as follows: If the laser module is rotated vertically, the number of pixels P within the angle unit is calculated as follows:

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