A system and method for precise automatic alignment of optical lens and negative pressure fixture

Abstract

The invention belongs to the field of optical lens processing, and discloses a system and method for precise automatic alignment of an optical lens and a negative pressure fixture, comprising a linear displacement platform, an image acquisition device, a negative pressure fixture, a servo electric cylinder, a rotary displacement platform, a two-axis linear displacement platform, a fixture fixing frame, an image processing system and a control system; the negative pressure fixture is used to install the optical lens, a positioning reference hole, a first characteristic plane and an image acquisition observation hole are arranged on the negative pressure fixture, an optical positioning point and a second characteristic plane are arranged on the optical lens, the first characteristic plane and the second characteristic plane are used for preliminary positioning of the optical lens and the negative pressure fixture, and the positioning reference hole and the optical positioning point are used for precise positioning of the optical lens and the negative pressure fixture; a servo electric cylinder is installed on the fixture fixing frame for adjusting the position of the optical lens relative to the negative pressure fixture; the automation of lens alignment is ensured, and the cost of alignment using an eccentricity instrument device is greatly reduced.

Description

Technical Field

[0001] The invention belongs to the field of optical lens processing, and in particular relates to a system and method for precise automatic alignment of an optical lens and a negative pressure fixture. Background Art

[0002] An aspheric lens refers to a curved lens with an aspheric refractive surface. Compared with a spherical lens, an aspheric lens has the advantages of eliminating aberrations, reducing the volume and mass of the optical system, and improving the image quality. A combined lens formed by bonding two aspheric lenses together through a bonding process is an effective method to achieve short focal length, high magnification, and good image quality. It has been widely used in optical products such as astronomical telescopes, VR glasses, and image acquisition devices. With the continuous improvement of the imaging quality requirements of optical systems, the bonding of aspheric lenses has put forward higher requirements for optical axis alignment accuracy, fewer defects, and faster bonding speed. Among them, ensuring that the optical axes of each aspheric lens are on the same axis can prevent the generation of aberrations such as coma, astigmatism, and dispersion, which is one of the most important technical requirements for lens bonding. The methods for achieving centering include instrument centering, automatic centering, and fixture centering.

[0003] The instrument centering method can ensure a high centering accuracy, but it needs to be equipped with a special centering device, the equipment cost is high, the centering time is long, and it is difficult to realize the automation of the entire gluing process;

[0004] Automatic centering relies on the gravity of the lens to achieve the coincidence of the optical axis. It is low-cost but has poor accuracy and is suitable for glass lenses with larger mass.

[0005] Using ultra-precision aspheric negative pressure suction cups to absorb the lens to be glued, and indirectly realizing the alignment of the lens to be glued through the positioning reference between the negative pressure suction cups, is an effective solution to ensure alignment accuracy, improve alignment efficiency, reduce alignment costs, improve the degree of automation of gluing, and maintain the stability of lens spacing during the gluing process. Patent CN202410209961.7 discloses a method and system for controlling the photocuring deformation of double glued lenses, which discloses a lens negative pressure suction cup, but the patent focuses on proposing a method of using an electric variable aperture diaphragm to control the ultraviolet light curing process of the lens, and does not introduce a method for centering the lens and the negative pressure suction cup; Patent CN202411486218.2 discloses a glass-plastic composite fixture for regulating the surface shape of glued lenses, and proposes a method for using an ideal surface shape suction cup to regulate the surface shape of the lens to achieve the purpose of actively adjusting the surface shape of the lens. The negative pressure fixture used in this patent has the same design idea as that of the patent, but the patent focuses on regulating the surface shape of the lens, and does not introduce a method for centering the lens and the negative pressure suction cup. Summary of the invention

[0006] In order to solve the technical problems existing in the prior art, the present invention proposes a system and method for precise automatic alignment of an optical lens and a negative pressure fixture, which adopts a binocular vision acquisition system to capture the relative position of the lens to be glued and the corresponding negative pressure fixture, calculates the lens adjustment amount by using Matlab, and changes the relative position relationship between the lens and the fixture through the precise displacement system on the negative pressure fixture to achieve precise alignment of the optical axis of the lens to be tested and the negative pressure fixture, and achieves precise alignment of the negative pressure fixtures through the relative positioning mechanism of the two negative pressure fixtures, thereby achieving precise alignment of the optical axes of the two lenses to be glued.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] In a first aspect, the present invention discloses a precise automatic alignment system for an optical lens and a negative pressure fixture, comprising a linear displacement platform, two image acquisition devices, a negative pressure fixture, a servo electric cylinder, a rotary displacement platform, a two-axis linear displacement platform, a fixture fixing frame, an image processing system and a control system;

[0009] The negative pressure fixture is used to install the optical lens. A positioning reference hole, a first characteristic plane and an image acquisition observation hole are provided on the negative pressure fixture. An optical positioning point and a second characteristic plane are provided on the optical lens. The first characteristic plane and the second characteristic plane are used for preliminary positioning of the optical lens and the negative pressure fixture. The positioning reference hole and the optical positioning point are used for precise positioning of the optical lens and the negative pressure fixture. The negative pressure fixture is installed on a fixture fixing frame, and a servo electric cylinder is installed on the fixture fixing frame to adjust the position of the optical lens relative to the negative pressure fixture. The fixture fixing frame is fixed on a rotary displacement platform, and the rotary displacement platform is installed on a two-axis linear displacement platform.

[0010] Two image acquisition devices are installed on the linear displacement platform, and the two image acquisition devices are located above the negative pressure clamp. The two image acquisition devices are used to shoot the outer edge contour image of the positioning reference hole and the outer edge contour image of the optical positioning point through the image acquisition observation hole; and transmit them to the image processing system. The control system controls the servo electric cylinder according to the processing information of the image processing system.

[0011] As a further technical solution, a backlight source is also installed on the fixture fixing frame.

[0012] As a further technical solution, four optical positioning points are provided; and four positioning reference holes are also provided;

[0013] As a further technical solution, the servo electric cylinder is provided one in each of the four directions of the front, back, left, and right of the optical lens.

[0014] As a further technical solution, a vacuum adsorption hole is also provided on the negative pressure fixture, and the vacuum adsorption hole is connected to a negative pressure vacuum pump for adsorbing the lens to be aligned.

[0015] As a further technical solution, the two-axis linear displacement platform includes an X-direction displacement platform and a Y-direction displacement platform. The X-direction displacement platform drives the Y-direction displacement platform, and the rotary displacement platform is installed on the Y-direction displacement platform.

[0016] As a further technical solution, the rotary translation stage can rotate in a horizontal plane.

[0017] In the second aspect, the present invention further provides a method for aligning an optical lens with a negative pressure fixture based on the above-mentioned precise automatic alignment system for an optical lens and a negative pressure fixture, which is specifically as follows:

[0018] Step 1: placing the lens to be aligned on the negative pressure fixture, and aligning the second characteristic plane of the lens to be aligned with the first characteristic plane on the negative pressure fixture along the normal direction, so as to achieve preliminary alignment between the lens to be aligned and the negative pressure fixture;

[0019] Step 2: Preliminary fixation of the position of the lens to be aligned;

[0020] Step 3: Use an image acquisition device to capture the outer edge contour of the optical positioning point and the outer edge contour of the positioning reference hole of the negative pressure fixture, and then transmit it to the image processing system. The image processing system processes the image to obtain the distance that the servo electric cylinder needs to move, and sends it to its control system;

[0021] Step 4: The control system controls the servo electric cylinder to move according to the distance to adjust the position of the lens to be aligned;

[0022] Step 5: After completing the movement in step 4, use the image acquisition device again to capture the outer edge contour of the optical positioning point and the outer edge contour of the positioning reference hole of the negative pressure fixture, and repeat steps 3-4 until the distance between the two circle centers is less than the set threshold, indicating that the alignment of the lens and the fixture is completed.

[0023] As a further technical solution, the specific control process of step 3 is as follows:

[0024] Step 3-1 compress the image;

[0025] Step 3-2: binarize the image and extract the image boundary by combining the edge detection algorithm;

[0026] Step 3-3 uses Hough transform to perform circle fitting and preliminarily screens the graph using preset values;

[0027] Step 3-4 combines the Kmeans clustering algorithm to select the target circle, and automatically calculates the distance between the center of the outer edge contour of the optical positioning point and the center of the outer edge contour of the positioning reference hole of the negative pressure fixture after the recognition is completed;

[0028] Step 3-5 calculates the distance that each of the two orthogonally distributed servo electric cylinders needs to extend based on the calculated distance between the two circle centers, and sends the information to its control system.

[0029] As a further technical solution, in step 2, the lens to be aligned is adsorbed by a vacuum pump to fix its position.

[0030] The beneficial effects of the present invention are as follows:

[0031] The present invention utilizes binocular vision cameras and micro servo electric cylinders to realize precise measurement and adjustment of the positions of lenses and fixtures. The entire process requires manual operation only when disassembling and installing ultra-precision adjustment modules, thereby ensuring the automation of lens alignment. Under the premise of ensuring that the alignment accuracy meets the lens alignment requirements, the adjustment and alignment of the lens and the fixture center can be realized by using only binocular cameras, micro servo electric cylinders, light sources, and tooling fixtures, thereby greatly reducing the cost of alignment using eccentricity equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A front view of a lens having an optical positioning point;

[0033] Figure 2 is a schematic diagram of a three-dimensional structure of a lens having optical positioning points;

[0034] Figure 3 is a side view of a lens having an optical positioning point;

[0035] Figure 4 A three-dimensional view of the lens with optical positioning points;

[0036] Figure 5 Schematic diagram of the three-dimensional structure of the negative pressure fixture Figure 1 ;

[0037] Figure 6 Schematic diagram of the three-dimensional structure of the negative pressure fixture Figure 2 ;

[0038] Figure 7 Schematic diagram of the structure of the precision automatic alignment system Figure 1 ;

[0039] Figure 8 Schematic diagram of the structure of the precision automatic alignment system Figure 2 ;

[0040] Fig. 9 It is a schematic diagram of the negative pressure fixture module and the servo electric cylinder;

[0041] Fig.10 It is a picture of the lens optical positioning point and the negative pressure fixture positioning reference hole taken by the camera;

[0042] Fig.11 The image is binarized and combined with the edge detection algorithm to extract the lens optical positioning points and the negative pressure fixture positioning reference hole boundary.

[0043] Fig.12 This is a schematic diagram of the distribution of micro servo electric cylinders;

[0044] Fig.13 These are pictures of the lens optical positioning point and the negative pressure fixture positioning reference hole before and after adjustment; (a), (b), (c) and (d) are pictures before adjustment; (e), (f), (g) and (h) are pictures after adjustment;

[0045] In the figure: 1. lens; 1-1. optical positioning point; 1-2. second characteristic plane;

[0046] 2. Negative pressure fixture; 2-1. Positioning reference hole; 2-2. First characteristic plane; 2-3. Vacuum adsorption hole, 2-4. Image acquisition observation hole;

[0047] 3-1. Linear displacement platform; 3-2. Camera; 3-3. Negative pressure fixture module; 3-4. Servo electric cylinder; 3-5. Blue parallel light source; 3-6. Rotary displacement platform; 3-7. Two-axis linear displacement platform; 3-8. Control system;

[0048] 5-1. Upper fixing seat; 5-2. Connecting rod, 5-3. Lower fixing seat, 5-4. Connecting hole;

[0049] 6-1. Outer edge contour circle of the optical positioning point; 6-2. Contour circle of the positioning reference hole. DETAILED DESCRIPTION

[0050] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0051] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless otherwise explicitly stated in the present invention, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "include" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof;

[0052] For the convenience of description, if the words "up", "down", "left" and "right" appear in the present invention, they only indicate that they are consistent with the up, down, left and right directions of the drawings themselves, and do not limit the structure. They are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0053] Terminology explanation section: The terms "install", "connect", "connect", "fixed" and the like in the present invention should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral whole; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be an internal connection between two elements, or an interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0054] In the prior art, a fiducial mark (optical positioning point), also commonly known as a mark point, is often used for optical positioning of parts, providing a common measurable reference point for all steps in the assembly process, and is usually circular for easy identification.

[0055] This implementation is as follows Figure 1 , Figure 2 The lens 1 with four circular optical positioning points 1-1 shown is the test object, and blue parallel light is used for illumination. The binocular vision camera 3-2 is used to collect the position image of the lens 1 and the negative pressure fixture, and the position parameters of the optical positioning point 1-1 and the positioning reference hole 2-1 of the negative pressure fixture are detected by Hough circle transformation. The central axis of the lens 1 and the negative pressure fixture are fitted by matlab software, and the central axis offset distance and the moving distance of the lens 1 aligned with the central axis in two orthogonal directions are solved. The parameters are sent to the micro servo electric cylinder 3-4 to control the movement of the lens 1, so as to achieve the precise alignment of the optical axis of the lens 1 with the central axis of the negative pressure fixture. Further, after the precise alignment of the optical axis of the lens 1 with the negative pressure fixture is achieved, the steps can be repeated to achieve the alignment of another lens 1 with the corresponding negative pressure fixture 2, and the alignment of the two negative pressure fixtures 2 is completed by the positioning pin, and finally the precise alignment of the optical axes of the two lenses 1 to be glued is achieved. This alignment method can avoid the use of high-cost optical centering instruments while ensuring the alignment accuracy, and the process is simple and easy to achieve full automation.

[0056] Specifically, the optical lens 1 and the negative pressure fixture 2 precision automatic alignment system proposed in this embodiment is as follows: Figure 7 , Figure 8As shown; including a linear displacement platform 3-1, two image acquisition devices, a negative pressure fixture 2, a servo electric cylinder 3-4, a rotary displacement platform 3-6, a two-axis linear displacement platform 3-7, a fixture fixing frame, an image processing system and a control system 3-8;

[0057] Wherein, the negative pressure fixture 2 is used to install the optical lens 1, such as Figure 5 , Figure 6 As shown, a positioning reference hole 2-1, a first characteristic plane 2-2 and an image acquisition observation hole 2-4 are provided on the negative pressure fixture 2.

[0058] like Figure 1 , Figure 2 , Figure 3 , Figure 4 As shown, an optical positioning point 1-1 and a second characteristic plane 1-2 are set on the optical lens 1, the first characteristic plane 2-2 and the second characteristic plane 1-2 are used for preliminary positioning of the optical lens 1 and the negative pressure fixture 2, and the positioning reference hole 2-1 and the optical positioning point 1-1 are used for precise positioning of the optical lens 1 and the negative pressure fixture 2; as a further technical solution, four optical positioning points 1-1 are set; and four positioning reference holes 2-1 are also set;

[0059] The negative pressure fixture 2 is installed on the fixture fixing frame, and a servo electric cylinder 3-4 is installed on the fixture fixing frame for adjusting the position of the optical lens 1 relative to the negative pressure fixture 2; and the fixture fixing frame is fixed on the rotation displacement stage 3-6, and the rotation displacement stage 3-6 is installed on the two-axis linear displacement platform 3-7;

[0060] Two image acquisition devices are installed on the linear displacement platform 3-1, and the two image acquisition devices are located above the negative pressure clamp 2. The two image acquisition devices are used to capture the outer edge contour of the positioning reference hole 2-1 and the outer edge contour of the optical positioning point 1-1 through the image acquisition observation hole 2-4; and transmit them to the image processing system. The control system controls the servo electric cylinder 3-4 according to the processing information of the image processing system.

[0061] As a further technical solution, a backlight source is also installed on the fixture fixing frame. In this embodiment, the backlight source adopts blue parallel light sources 3-5. Of course, other light sources can also be used as the backlight source.

[0062] As a further technical solution, the servo electric cylinder 3-4 is arranged one in each of the four directions of the front, back, left, and right of the optical lens 1.

[0063] As a further technical solution, a vacuum adsorption hole 2 - 3 is further provided on the negative pressure fixture 2 , and the vacuum adsorption hole 2 - 3 is connected to a negative pressure vacuum pump for adsorbing the lens 1 to be aligned.

[0064] As a further technical solution, the two-axis linear displacement platform 3-7 includes an X-direction displacement platform and a Y-direction displacement platform. The X-direction displacement platform drives the Y-direction displacement platform, and the rotary displacement platform 3-6 is installed on the Y-direction displacement platform.

[0065] As a further technical solution, the rotary translation stage 3-6 can rotate in a horizontal plane.

[0066] Furthermore, the fixture fixing frame is as follows Fig. 9 As shown, it includes an upper fixing seat 5-1, a connecting rod 5-2, a lower fixing seat 5-3, and a connecting hole 5-4; the upper fixing seat 5-1 and the lower fixing seat 5-3 are installed up and down, and are connected by the connecting rod 5-2 to form a whole, the negative pressure fixture 2 is fixed on the upper fixing seat 5-1, and the blue parallel light source 3-5 is fixed on the lower fixing seat, and a plurality of connecting holes 5-4 are also provided on the lower fixing seat, and the connecting holes 5-4 are used to connect the fixture fixing frame and the rotary displacement table 3-6. Further, the above-mentioned servo electric cylinder 3-4 is also installed on the upper fixing seat 5-1.

[0067] The specific operation method is as follows:

[0068] 1. Ultra-precision machining of fixture positioning reference hole 2-1

[0069] As a reference for the alignment of the lens 1, the position accuracy and shape accuracy of the positioning reference hole 2-1 of the negative pressure fixture 2 directly affect the alignment accuracy of the lens 1. Therefore, the negative pressure fixture 2 is ultra-precision machined using an ultra-precision machining machine. After the processing of the adsorption surface of the negative pressure fixture 2 is completed by ultra-precision turning, the position of the machine tool spindle and the center axis of the negative pressure fixture 2 can be accurately located. Then, according to the distribution of the optical positioning points 1-1 of the lens 1, a consistent number (4 in this embodiment) of positioning reference holes 2-1 are drilled at the corresponding positions of the negative pressure fixture 2. This method ensures that the position and shape accuracy of the positioning reference holes 2-1 are sufficient to meet the alignment requirements of the lens 1.

[0070] 2. Ultra-precision alignment platform construction

[0071] As described above, the ultra-precision alignment platform of this embodiment mainly includes a linear displacement platform 3-1, a camera 3-2, a negative pressure fixture module 3-3, a servo electric cylinder 3-4, a blue parallel light source 3-5, a rotary displacement platform 3-6, and a two-axis linear displacement platform 3-7;

[0072] Two high-resolution industrial cameras 3-2 are required to collect the positions of the optical positioning point 1-1 and the positioning reference hole 2-1; therefore, the camera 3-2 is fixed on the linear displacement platform 3-1 to adjust the focal length of the camera 3-2;

[0073] A blue parallel light source 3-5 is used as a backlight source to provide illumination for the camera 3-2 from the direction of the optical axis of the camera 3-2;

[0074] Four micro servo electric cylinders 3-4 are used to receive the position information collected by the camera 3-2 and adjust the position of the lens 1, thereby achieving precise alignment between the optical positioning point 1-1 of the lens 1 and the positioning reference hole 2-1 of the negative pressure fixture 2;

[0075] A rotary translation stage 3-6 is used to adjust the angle of the negative pressure fixture 2 and the lens 1 relative to the industrial camera 3-2;

[0076] A two-axis linear displacement platform 3-7 is used to adjust the positions of the negative pressure fixture 2 and the lens 1 in the XY axis direction to ensure that two positioning reference holes 2-1 of the negative pressure fixture 2 in the same radial direction are simultaneously within the field of view of the two cameras 3-2;

[0077] A linear displacement platform 3-1 is used to adjust the position of the camera 3-2 along the optical axis so that the camera 3-2 is focused on the optical positioning point 1-1 of the lens 1 and the positioning reference hole 2-1 of the negative pressure fixture 2.

[0078] 3. Align the optical positioning point 1-1 of the optical lens 1 with the positioning reference hole 2-1 of the negative pressure fixture 2

[0079] The positions of the optical positioning point 1-1 of the optical lens 1 and the positioning reference hole 2-1 of the negative pressure fixture 2 are as described above. The ideal positional relationship between the optical positioning point 1-1 of the lens 1 and the positioning reference hole 2-1 of the negative pressure fixture 2 is coaxial, that is, the expected adjusted positional relationship. However, relying on the outer circle of the lens 1 and the second characteristic plane 1-2, only the preliminary alignment of the two circles can be achieved, and the two are not coaxially aligned. In order to achieve the alignment of the two circles, the edge extraction is performed on the captured image, and the center coordinates of the outer edge contour circle 6-1 of the optical positioning point of the lens 1 and the positioning reference hole contour circle 6-2 are fitted. The center deviation is calculated to obtain the distance required for alignment, and the micro servo cylinder 3-4 is used to drive the lens 1 to move and then achieve alignment.

[0080] Furthermore, based on the above-mentioned precise automatic alignment system of optical lens and negative pressure fixture, this embodiment also provides a method for aligning the optical lens and the negative pressure fixture, which is as follows:

[0081] Step 1: placing the lens to be aligned on the negative pressure fixture, and aligning the second characteristic plane of the lens to be aligned with the first characteristic plane on the negative pressure fixture along the normal direction, so as to achieve preliminary alignment between the lens to be aligned and the negative pressure fixture;

[0082] Step 2: Preliminary fixation of the position of the lens to be aligned;

[0083] Step 3: Use an image acquisition device to capture the outer edge contour of the optical positioning point and the outer edge contour of the positioning reference hole of the negative pressure fixture, and then transmit it to the image processing system. The image processing system processes the image to obtain the distance that the servo electric cylinder needs to move, and sends it to its control system;

[0084] Step 4: The control system controls the servo electric cylinder to move according to the distance to adjust the position of the lens to be aligned;

[0085] Step 5: After completing the movement in step 4, use the image acquisition device again to capture the outer edge contour of the optical positioning point and the outer edge contour of the positioning reference hole of the negative pressure fixture, and repeat steps 3-4 until the distance between the two circle centers is less than the set threshold, indicating that the alignment of the lens and the fixture is completed.

[0086] The specific processes corresponding to the above steps are as follows:

[0087] Will Figure 1 The lens 1 to be aligned is placed on the negative pressure fixture 2, and during this period, the inherent second characteristic plane 1-2 of the lens 1 to be aligned is aligned along the normal direction with the first characteristic plane 2-2 processed on the negative pressure fixture 2, so as to achieve the preliminary alignment between the lens 1 to be aligned and the negative pressure fixture 2, and then the negative pressure vacuum pump is turned on to make the negative pressure fixture 2 absorb the lens 1. The blue parallel light source 3-5 in the figure is placed on the lower fixing seat 5-3 without fixing; the negative pressure fixture module 3-3 is pressed Figure 6 In the structure shown, the smaller diameter portion passes through the upper fixing seat 5-1 with a through hole, and is connected to the upper fixing seat 5-1 by bolts; four servo electric cylinders 3-4 are connected to the upper fixing seat 5-1 by bolts, and then the upper fixing seat is connected to the rotary displacement stage 3-6 by bolts through the four connecting holes 5-4 by connecting rods 5-2. At this time, the optical positioning point 1-1 of the lens 1 and the positioning reference hole 2-1 of the negative pressure fixture 2 are not coaxially aligned, but the outer edge contour circle 6-1 of the optical positioning point and the positioning reference hole contour circle 6-2 can be observed by the camera 3-2; Fig.10 , Fig.11 This is a picture of the optical positioning point 1-1 of the lens 1 and the positioning reference hole 2-1 of the negative pressure fixture 2 taken by the camera 3-2. There is no situation where the fixture reference hole blocks the optical positioning point 1-1 of the lens 1.

[0088] Use camera 3-2 to take pictures of the optical positioning point 1-1 of lens 1 and the positioning reference hole 2-1 of negative pressure fixture 2, and then automatically process the taken pictures in matlab software. The specific processing steps are as follows:

[0089] Step 3-1 compress the image to increase the detection speed;

[0090] Step 3-2: Binarize the image and extract the boundary by using edge detection algorithm. Fig.11 As shown;

[0091] Step 3-3: Use Hough transform to perform circle fitting, and preliminarily screen the graph by using preset values ​​(selecting the maximum and minimum radius and the number of circles according to the diameter of the target circle to be measured);

[0092] Step 3-4: Combine the Kmeans clustering algorithm to select the target circle. After the recognition is completed, the center, radius and distance between the two circles of the target circle are automatically calculated;

[0093] Step 3-5: Based on the calculated distance between the two center points, the positioning reference hole 2-1 is fixed, and the optical positioning point 1-1 of the lens 1 is moved so that the distance between the two center points is zero. The two orthogonally distributed micro servo electric cylinders 3-4 are calculated as follows: Fig.12 As shown (taking two of the electric cylinders as an example, the ones that need to be extended in actual alignment may be another pair of electric cylinders), the distance that each needs to be extended is determined, and the information is sent to its control system 3-8.

[0094] The micro servo electric cylinder 3-4 receives the motion information and controls the movement of its lead screw. When the lead screw is extended, the front end of the micro servo electric cylinder 3-4 keeps approaching the lens 1 and determines whether it is in contact through the force sensor integrated into the servo electric cylinder 3-4. When in contact, the lens 1 is pushed to move a corresponding distance according to the distance required to be moved in the previous step. At this time, in order to prevent the lens 1 from falling off the fixture, the negative pressure pump needs to be continuously used to absorb the lens 1, and at the same time, it is necessary to ensure that the maximum load of the cylinder is sufficient to push the lens 1 to move; the other servo electric cylinder 3-4 on the opposite side of the servo electric cylinder 3-4 is synchronously or preferentially retracted to release space for the movement of the lens 1, and the movement amount is greater than the extension distance of the micro servo electric cylinder 3-4 on the opposite side;

[0095] After completing the above movement, use camera 3-2 to shoot again. Fig.10 Refer to the picture of the optical positioning point 1-1 of the lens 1 and the positioning reference hole 2-1 of the negative pressure fixture 2 shown in the figure, and repeat the previous steps. If the distance between the two circle centers is less than the set threshold (set according to the alignment error requirements of the lens 1 in actual production, generally it should be less than 30μm), it means that the alignment of the lens 1 and the fixture is completed. At this time, the fixture can be removed to align the next group of lenses 1 and the fixture. After the two groups are aligned, further gluing can be carried out; if the distance between the two circle centers is greater than or equal to the set threshold, it is necessary to continue the previous steps until the distance is less than the set threshold.

[0096] After completing the alignment of a single lens and the fixture, move the negative pressure fixture module 3-3 from Figure 7The ultra-precision alignment platform shown in the figure is removed. At this time, the alignment of the lens and the fixture is completed. When disassembling, you only need to remove the bolts connected to the upper fixing seat; if another lens needs to be aligned next, complete the preliminary fixation of another negative pressure fixture module and another lens to be aligned according to the above preliminary alignment and adsorption steps, and connect the negative pressure fixture module to the upper fixing seat in the same way as above, and perform precise alignment again.

[0097] The experimental verification process is as follows:

[0098] In order to further prove the beneficial effects of the present invention, an experimental verification was carried out. The positional relationship between the four optical positioning points 1-1 of the lens 1 and the four positioning reference holes 2-1 of the negative pressure fixture 2 photographed in the previous steps is as follows: Fig.13 As shown in (a), (b), (c), and (d), the inner optical positioning point 1-1 of the lens 1 and the positioning reference hole 2-1 of the outer negative pressure fixture 2 are clearly visible, but it can be clearly seen that each pair of optical positioning points 1-1 and positioning reference holes 2-1 are obviously eccentric. Through the above steps, the eccentricity errors between the lens 1 and the negative pressure fixture 2 in the two directions are solved to be 51μm and 35.6μm respectively, and the total deviation is After adjusting the lens position, the positional relationship between the four lens 1 optical positioning points 1-1 and the four negative pressure fixture 2 positioning reference holes 2-1 is as follows: Fig.13 As shown in (e), (f), (g), and (h), each pair of optical positioning points 1-1 is closer to the center of the positioning reference hole 2-1. The eccentricity errors in the two directions between the lens 1 and the negative pressure fixture 2 are 17.1μm and 13μm respectively, and the total deviation is: , which has met the set threshold, indicating that the position adjustment of lens 1 has achieved good results.

Claims

1. A precise automatic alignment system for an optical lens and a negative pressure fixture, characterized in that: It includes a linear displacement platform, two image acquisition devices, a negative pressure fixture, a servo electric cylinder, a rotary displacement platform, a two-axis linear displacement platform, a fixture fixing frame, an image processing system and a control system; The negative pressure fixture is used to install the optical lens. A positioning reference hole, a first characteristic plane and an image acquisition observation hole are provided on the negative pressure fixture. An optical positioning point and a second characteristic plane are provided on the optical lens. The first characteristic plane and the second characteristic plane are used for preliminary positioning of the optical lens and the negative pressure fixture. The positioning reference hole and the optical positioning point are used for precise positioning of the optical lens and the negative pressure fixture. The negative pressure fixture is installed on a fixture fixing frame, and a servo electric cylinder is installed on the fixture fixing frame to adjust the position of the optical lens relative to the negative pressure fixture. The fixture fixing frame is fixed on a rotary displacement platform, and the rotary displacement platform is installed on a two-axis linear displacement platform. Two image acquisition devices are installed on the linear displacement platform, and the two image acquisition devices are located above the negative pressure clamp. The two image acquisition devices are used to shoot the outer edge contour image of the positioning reference hole and the outer edge contour image of the optical positioning point through the image acquisition observation hole; and transmit them to the image processing system. The control system controls the servo electric cylinder according to the processing information of the image processing system.

2. The optical lens and negative pressure fixture precision automatic alignment system as claimed in claim 1, characterized in that: A backlight source is also installed on the fixture fixing frame.

3. The optical lens and negative pressure fixture precision automatic alignment system as claimed in claim 1, characterized in that: There are four optical positioning points and four positioning reference holes.

4. The optical lens and negative pressure fixture precision automatic alignment system as claimed in claim 1, characterized in that: The servo electric cylinder is arranged one in each of the four directions of the optical lens: front, back, left, and right.

5. The optical lens and negative pressure fixture precision automatic alignment system as claimed in claim 1, characterized in that: A vacuum adsorption hole is also provided on the negative pressure fixture, and the vacuum adsorption hole is connected to a negative pressure vacuum pump for adsorbing the lens to be aligned.

6. The optical lens and negative pressure fixture precision automatic alignment system as claimed in claim 1, characterized in that: The two-axis linear displacement platform comprises an X-direction displacement platform and a Y-direction displacement platform. The X-direction displacement platform drives the Y-direction displacement platform, and the rotary displacement platform is installed on the Y-direction displacement platform.

7. The optical lens and negative pressure fixture precision automatic alignment system as claimed in claim 1, characterized in that: The rotary translation platform can rotate in a horizontal plane.

8. A method for aligning an optical lens and a negative pressure fixture using the optical lens and negative pressure fixture precision automatic alignment system according to any one of claims 1 to 7, characterized in that: as follows: Step 1: placing the lens to be aligned on the negative pressure fixture, and aligning the second characteristic plane of the lens to be aligned with the first characteristic plane on the negative pressure fixture along the normal direction, so as to achieve preliminary alignment between the lens to be aligned and the negative pressure fixture; Step 2: Preliminary fixation of the position of the lens to be aligned; Step 3: Use an image acquisition device to capture the outer edge contour of the optical positioning point and the outer edge contour of the positioning reference hole of the negative pressure fixture, and then transmit it to the image processing system. The image processing system processes the image to obtain the distance that the servo electric cylinder needs to move, and sends it to its control system; Step 4: The control system controls the servo electric cylinder to move according to the distance to adjust the position of the lens to be aligned; Step 5: After completing the movement in step 4, use the image acquisition device again to capture the outer edge contour of the optical positioning point and the outer edge contour of the positioning reference hole of the negative pressure fixture, and repeat steps 3-4 until the distance between the two circle centers is less than the set threshold, indicating that the alignment of the lens and the fixture is completed.

9. The method for aligning an optical lens and a negative pressure fixture using the optical lens and negative pressure fixture precision automatic alignment system as claimed in claim 8, characterized in that: The specific control process of step 3 is as follows: Step 3-1 compress the image; Step 3-2: binarize the image and extract the image boundary by combining the edge detection algorithm; Step 3-3 uses Hough transform to perform circle fitting and preliminarily screens the graph using preset values; Step 3-4 combines the Kmeans clustering algorithm to select the target circle, and automatically calculates the distance between the center of the outer edge contour of the optical positioning point and the center of the outer edge contour of the positioning reference hole of the negative pressure fixture after the recognition is completed; Step 3-5 calculates the distance that each of the two orthogonally distributed servo electric cylinders needs to extend based on the calculated distance between the two circle centers, and sends the information to its control system.

10. The method for aligning an optical lens and a negative pressure fixture using the optical lens and negative pressure fixture precision automatic alignment system as claimed in claim 8, characterized in that: In step 2, the lens to be aligned is attached to the negative pressure fixture by vacuum adsorption, and its position is fixed.

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