An ultra-depth-of-field high-precision measurement system based on a symmetric objective lens

Abstract

The application discloses a kind of based on symmetric objective's super depth of field high-precision measurement system, it is related to precision measurement technical field.Therein including: camera, camera fixed group, coaxial illumination group, displacement sliding table, L-shaped connecting branch plate, near object movement group, super depth of field scanning imaging area, software algorithm module of coordination each hardware work;The camera fixed group rigidity connection is to the bottom of camera, coaxial illumination group is integrated and installed in the side cavity of camera fixed group, the fixed guide rail of displacement sliding table is fixed in the side wall of camera fixed group along system Z direction, the movable sliding block of displacement sliding table and the vertical connecting plate of L-shaped connecting branch plate rigidity fixed connection;The horizontal connecting plate of L-shaped connecting branch plate and the top of near object movement group rigidity butt joint fixed, super depth of field scanning imaging area is the placement area of object to be measured.The application has extremely strong environmental adaptability, can keep stable measurement precision under complex environment, is widely applicable scene, has extremely high practical value and large-scale industrialization prospect.

Description

Technical Field

[0001] This invention relates to the field of precision measurement technology, and in particular to a high-precision measurement system for ultra-depth of field based on a symmetrical objective lens. Background Technology

[0002] In fields such as industrial inspection, precision manufacturing, and biomedicine, the demand for high-precision measurement of the three-dimensional structure of objects is increasing. Ultra-depth-of-field measurement systems, with their advantage of being able to stitch together shallow depth-of-field images of different heights to construct large depth-of-field models, have become a key technical means to achieve this type of measurement.

[0003] The measurement accuracy of a super depth-of-field system is closely related to the depth of field of a single-image shot: according to optical principles, the smaller the depth of field in a single frame, the stronger the ability to resolve object details, and the higher the upper limit of accuracy in detail reproduction and dimensional accuracy of the reconstructed 3D model. At the same time, the system's measurement efficiency is significantly affected by the frame size of a single shot: the larger the frame size, the fewer movements and shots are required to cover the specified area of ​​the object under test, effectively shortening the overall measurement time and improving work efficiency.

[0004] It is evident that low magnification (corresponding to a large field of view) and shallow depth of field (corresponding to a large numerical aperture) are the core requirements for achieving breakthroughs in accuracy and efficiency in ultra-depth-of-field imaging systems, and the synergistic optimization of the two is the key direction for the research and development of such systems.

[0005] Current mainstream ultra-depth-of-field detection systems mainly employ two optical schemes, but both have insurmountable limitations and cannot simultaneously meet the application requirements of large field of view, large numerical aperture, and high precision: (1) Microscopic system-based approach: This approach uses an infinity conjugate microscope objective combined with a tube mirror, and achieves scanning in the height Z direction by moving the microscope objective upwards along the axis. However, in order to obtain a large numerical aperture to reduce the depth of field, it is usually necessary to use a high-magnification microscope objective. However, most existing tube mirrors are designed with a low magnification of 0.5X, which makes it difficult to expand the imaging field, resulting in a limited field of view of the system and making it impossible to efficiently measure large objects.

[0006] (2) Scheme based on dual telecentric lenses: This scheme achieves scanning by displacing the lens and camera as a whole. On the one hand, due to the constraints of optical design principles, the image size and numerical aperture of dual telecentric lenses are mutually restrictive, making it difficult to achieve a large field of view and a large numerical aperture at the same time; on the other hand, the scanning process requires moving the lens and camera as a whole, which results in a large system load and is prone to accuracy deviations in the displacement platform, thereby reducing the overall measurement accuracy of the system, especially in long-term, high-frequency scanning scenarios, where the accuracy loss is more obvious.

[0007] In summary, current ultra-depth-of-field measurement technologies cannot overcome the bottleneck of synergistic optimization of large field of view and large numerical aperture. They also suffer from problems such as complex system structure, large motion load, easy degradation of measurement accuracy, and high equipment manufacturing and maintenance costs. As a result, they cannot meet the comprehensive application requirements of modern industrial inspection, precision manufacturing, biomedicine and other fields for ultra-depth-of-field measurement systems that simultaneously possess large field of view, large numerical aperture, high precision, high stability and low cost. Summary of the Invention

[0008] The present invention also provides a high-precision measurement system for ultra-depth of field based on a symmetrical objective lens, comprising: a camera (1), a camera fixing group (2), a coaxial illumination group (3), a displacement slide (4), an L-shaped connecting support plate (5), a near object moving group (6), an ultra-depth of field scanning imaging area (7), and a software algorithm module for coordinating the operation of each hardware component; The camera fixing assembly (2) is rigidly connected to the bottom end of the camera (1). The camera fixing assembly (2) and the camera (1) remain fixed throughout the entire process. The output light path of the camera fixing assembly (2) matches the position of the photosensitive surface of the camera (1). The coaxial illumination assembly (3) is integrated and installed in the side cavity of the camera fixing assembly (2). The fixed guide rail of the displacement slide (4) is fixed to the side wall of the camera fixing assembly (2) along the Z direction of the system (the vertical movement direction marked in the figure, that is, the extension direction of the optical principal axis of the system, the height direction of the object to be measured). The movable slider of the displacement slide (4) is connected to the L-shaped connecting... The vertical connecting plate of the support plate (5) is rigidly fixed; the horizontal connecting plate of the L-shaped connecting support plate (5) is rigidly docked and fixed to the top of the near object moving group (6); the main optical axis of the near object moving group (6) is coaxial with the main optical axis of the camera fixing group (2); the near object moving group (6) and the movable slider of the displacement slide (4) and the L-shaped connecting support plate (5) maintain completely synchronized Z-direction displacement; the ultra-depth scanning imaging area (7) is the placement area of ​​the object to be measured, located within the object working distance of the near object moving group (6), and within the Z-direction scanning stroke coverage range of the near object moving group (6).

[0009] As described above, a high-precision measurement system based on a symmetrical objective lens for ultra-depth of field includes a camera (1) for acquiring shallow depth-of-field images at different heights; a camera fixing group (2) is a symmetrical objective lens rear group for refocusing the parallel beam emitted from the near object moving group (6) and projecting it onto the photosensitive surface of the camera (1) to form a clear image; a coaxial illumination group (3) is used to provide a uniform and stable coaxial illumination source for the system; a displacement slide (4) is used to provide high-precision linear guidance for the Z-axis movement of the near object moving group (6); an L-shaped connecting support plate (5) is used to achieve complete synchronous displacement between the moving slider of the displacement slide (4) and the near object moving group (6); the near object moving group (6) is a symmetrical objective lens front group for receiving the reflected light from the object under test and shaping the divergent reflected light into a parallel beam for emission; and an ultra-depth-of-field scanning imaging area (7) is used to place the object under test.

[0010] As described above, in a high-precision measurement system for ultra-depth of field based on a symmetrical objective lens, the movable slider of the displacement stage (4) moves linearly back and forth along the Z-direction of the system, and synchronously drives the L-shaped connecting support plate (5) to move linearly back and forth along the Z-direction of the system through a rigid connection. The L-shaped connecting support plate (5) synchronously drives the near-object moving group (6) to move linearly back and forth along the Z-direction of the system through a rigid docking. The camera (1), camera fixing group (2), coaxial illumination group (3), and ultra-depth of field scanning imaging area (7) remain in fixed positions throughout the process.

[0011] As described above, a high-precision measurement system for ultra-depth of field based on symmetrical objective lenses is described, wherein the photosensitive surface of the built-in photosensitive chip of the camera (1) is the image plane (11) of the system, the three-dimensional measured surface of the object to be measured, which is rigidly fixed in the ultra-depth of field scanning imaging area (7), is the object plane (71), the near object moving group (6) and the camera fixed group (2) are two independent optical lens groups with no direct mechanical connection, and are optically coupled through the optical path; the camera fixed group (2) includes an aperture (21), and the near object moving group (6) includes an aperture (61); the aperture (61) of the near object moving group (6) and the aperture (21) of the camera fixed group (2) are aligned along the main light path of the system. The two groups are arranged coaxially and opposite each other, and the two groups are parallel light transmission optical paths. The object-side working distance of the near object moving group (6) is constant. During the movement, the optical imaging relationship between the lens and the object under test is stable. The near object moving group (6) moves independently along the Z direction of the system, and the camera fixed group (2) remains stationary throughout the process. When the near object moving group (6) is in the initial scanning position, the aperture (61) of the near object moving group (6) is axially connected to the aperture (21) of the camera fixed group (2). After the near object moving group (6) moves, the aperture (61) of the near object moving group (6) separates from the aperture (21) of the camera fixed group (2), and its fixed object-side working distance synchronously scans different height areas of the object surface (71).

[0012] As described above, a high-precision measurement system for ultra-depth of field based on a symmetrical objective lens is provided. In this system, the camera fixing group (2) has a built-in beam splitter (22), and the coaxial illumination group (3) integrates the fiber optic light source end face (31) and the aperture (32). The aperture (21) of the camera fixing group (2) is placed between the first lens of the camera fixing group (2) near the object. In the imaging optical path, the reflected light from the object surface (71) passes through the near-object moving group (6), the transmission surface of the beam splitter (22), and the camera fixing group (2) in sequence, and is then focused on the image plane (11) for clear imaging. In the illumination optical path, the illumination light is emitted from the fiber optic light source end face (31), then enters the beam splitter (22) after being limited by the aperture (32) and collimated by the lens group of the coaxial illumination group (3). After being reflected by the beam splitter, it is coaxial with the imaging optical path, and then focused by the near-object moving group (6) and emitted vertically to the object surface (71).

[0013] As described above, a high-precision measurement system for ultra-depth of field based on a symmetrical objective lens is provided. The independent illumination optical path of the coaxial illumination group (3) consists of the fiber optic light source end face (31), the aperture (32), and multiple collimating lens groups arranged coaxially along the main optical axis of the illumination optical path of the coaxial illumination group (3). The fiber optic light source end face (31) is the light source emission end of the illumination optical path and is arranged at the incident end of the optical path. The aperture (32) is arranged at the converging pupil position of the lens group and is arranged coaxially with the main optical axis of the illumination optical path of the coaxial illumination group (3). The diverging illumination light emitted from the fiber optic light source end face (31) is converged and shaped by the front lens group, and then the aperture (32) limits the beam aperture and filters out stray light. It is then collimated into a uniform parallel beam by the rear lens group and emitted, forming an illumination optical path that conforms to the Kohler illumination design concept. It is coupled with the imaging optical path to ensure the uniformity of illumination brightness across the entire field of view of the object surface.

[0014] This invention provides a high-precision measurement method for ultra-depth of field based on a symmetrical objective lens, applied to the software algorithm module of the aforementioned high-precision measurement system for ultra-depth of field based on a symmetrical objective lens, comprising: Step S1: Based on the parallel light transmission characteristics of the symmetrical objective lens, plan the total scanning stroke, adaptively set the scanning step distance based on the system depth of field and displacement accuracy constraints, and generate a full sequence of scanning point sets; Step S2: Obtain the surface reflection type of the object under test, combine the optical parameters of the symmetrical objective lens, configure the camera imaging parameters and coaxial illumination group parameters, and enable the coaxial illumination group. Step S3: Based on the total scanning travel, scanning step distance and full sequence scanning point set, drive the near object moving group to move to the target scanning point in sequence. After online error compensation, trigger the camera to acquire single-height shallow depth-of-field images of the target scanning point and obtain a multi-height shallow depth-of-field image set with height labels. Step S4: Using an image fusion and stitching algorithm, extract the clear areas from each image in the multi-height shallow depth-of-field image set with height labels, stitch and fuse them to generate a 3D model image.

[0015] The above-described method for high-precision measurement of ultra-depth of field based on a symmetrical objective lens includes the following sub-steps: planning the total scanning stroke based on the parallel light transmission characteristics of the symmetrical objective lens; adaptively setting the scanning step distance based on system depth of field and displacement accuracy constraints; and generating a full sequence of scanning point sets. Step S11: Control the object movement group to perform a pre-scan of the object to be tested, and determine the total scanning distance based on the sharpness change curve of the image acquired by the camera during the pre-scan. Step S12: Based on the minimum step distance of the displacement slide and the theoretical depth of field of the symmetrical objective lens, automatically set the optimal scanning step distance and generate a full sequence of scanning point sets.

[0016] The above-described method for high-precision measurement of ultra-depth of field based on a symmetrical objective lens includes the following sub-steps: obtaining the surface reflection type of the object under test, configuring the camera imaging parameters and coaxial illumination group parameters in conjunction with the optical parameters of the symmetrical objective lens, and enabling the coaxial illumination group. Step S21: Trigger the camera to perform single-frame pre-acquisition, and identify the surface reflection type of the object to be tested based on the grayscale statistical characteristics of the pre-acquisition image; Step S22: Based on the surface reflection type of the object under test, and combined with the optical parameters of the symmetrical objective lens, configure the camera imaging parameters; Step S23: Obtain ambient lighting information, combine it with the surface reflection type of the object under test, match and configure the light source power of the coaxial illumination group, and enable the coaxial illumination group according to the configured power.

[0017] The above-described method for high-precision measurement of ultra-depth of field based on a symmetrical objective lens includes the following sub-steps: Based on the total scanning travel, scanning step distance, and the full sequence of scanning points, the near-object movement group is driven to move sequentially to the target scanning point. After online error compensation, the camera is triggered to acquire a single-height shallow depth-of-field image of the target scanning point. Obtaining a multi-height shallow depth-of-field image set with height labels includes the following sub-steps: Step S31: Send the target scanning point command to the high-precision stepper motor of the driving displacement slide according to the height sorting of the scanning point set, drive the displacement slide, and drive the near object moving group to move synchronously along the Z direction through the L-shaped connecting support plate. The grating ruler displacement sensor collects the actual displacement of the displacement slide in real time. Step S32: After the near object moving group moves to the target scanning point, compare the preset displacement of the target scanning point with the actual displacement, perform online compensation for position error, trigger the camera to acquire images, and simultaneously record the current height coordinates to form a single-height shallow depth-of-field image with height label. Step S33: Repeat steps S31 to S32 until all scan points in the full sequence scan point set are traversed to obtain a set of multi-height shallow depth-of-field images with height labels.

[0018] The above-described method for high-precision measurement of ultra-depth of field based on symmetrical objectives includes the following sub-steps: Extracting sharp regions from each image in a multi-height shallow depth-of-field image set with height labels using an image fusion and stitching algorithm, and then stitching and fusing them to generate a 3D model image. Step S41: Perform image denoising and spatial registration on the multi-height shallow depth-of-field image set with height labels; Step S42: Calculate the pixel-by-pixel sharpness evaluation value for each image in the multi-height shallow depth-of-field image set after denoising and registration, extract the sharp regions at each pixel position, and stitch and fuse them into a three-dimensional model image of the object to be tested.

[0019] The beneficial effects achieved by this invention are as follows: This invention achieves a synergistic breakthrough in large field of view and large numerical aperture. The large field of view reduces the number of scans for workpieces of the same size by more than 60%, significantly improving measurement efficiency. The 0.125 object-space numerical aperture achieves a theoretical depth of field of 20μm, enabling micron-level three-dimensional topography reconstruction with industry-leading measurement accuracy. The symmetrical optical design achieves self-distortion elimination, with a maximum TV distortion of only 0.0054%, far superior to the industry standard, eliminating dimensional measurement errors caused by distortion at the source. The lightweight scanning design drives only the front objective lens, reducing system load by over 60%. This effectively minimizes accuracy loss during long-duration, high-frequency scanning, enhancing the system's long-term stability and reliability. It boasts extremely high scanning displacement control precision, with a minimum step distance of 1μm. Combined with full closed-loop displacement compensation control, it precisely controls the scanning stroke, ensuring accurate image acquisition at each height level and eliminating 3D reconstruction errors caused by displacement deviations. Image quality remains stable and unaffected throughout the 0-20mm scanning stroke, guaranteeing consistency and reconstruction accuracy across the sequence of images. The coaxial Kohler illumination design provides uniform, shadow-free illumination across the entire field of view, perfectly adapting to surfaces with varying reflectivity and solving imaging challenges in low-reflection and low-light scenarios. The optimized fusion algorithm improves processing efficiency by 30% compared to traditional solutions, offering excellent detail reproduction. The overall system manufacturing cost is reduced by over 40% compared to traditional high-precision solutions. The simplified structure facilitates maintenance and upgrades, while exhibiting strong environmental adaptability. It maintains stable measurement accuracy even in complex environments such as industrial workshops with vibrations and temperature fluctuations, making it suitable for a wide range of applications and possessing high practical value and promising prospects for large-scale industrial deployment. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0021] Figure 1 This is a schematic diagram of the overall structure of a high-precision measurement system for ultra-depth of field based on a symmetrical objective lens, provided in Embodiment 1 of this application. Figure 2 This is a schematic diagram of the Z-axis scanning motion state and displacement driving structure of a high-precision ultra-depth-of-field measurement system based on a symmetrical objective lens, provided in Embodiment 1 of this application. Figure 3 This is a schematic diagram of the symmetrical objective lens optical structure and the ultra-depth-of-field scanning optical principle provided in Embodiment 1 of this application; Figure 4 This is a simulation curve of the MTF of the symmetrical objective lens at the initial position of 0mm provided in Embodiment 1 of this application; Figure 5 This is a simulation curve of the MTF at the maximum travel position of the symmetrical objective lens at 20mm provided in Embodiment 1 of this application; Figure 6 This is a schematic diagram of the illumination-imaging coaxial coupling optical path structure provided in Embodiment 1 of this application; Figure 7 This is a schematic diagram of the independent lighting optical path structure of the coaxial lighting group provided in Embodiment 1 of this application; Figure 8 This is a flowchart of a high-precision measurement method for ultra-depth of field based on a symmetrical objective lens, provided in Embodiment 2 of this application. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1 like Figure 1 As shown, Embodiment 1 of this application provides a high-precision measurement system for ultra-depth of field based on a symmetrical objective lens, including: a camera 1, a camera fixing group 2, a coaxial illumination group 3, a displacement slide 4, an L-shaped connecting support plate 5, a near-object movement group 6, an ultra-depth of field scanning imaging area 7, and a software algorithm module that coordinates the operation of each hardware component.

[0024] The camera fixing group 2 is rigidly connected to the bottom of the camera 1, and the camera fixing group 2 and the camera 1 remain fixed throughout the entire process. The output light path of the camera fixing group 2 is matched with the position of the photosensitive surface of the camera 1. The coaxial illumination group 3 is integrated and installed in the side cavity of the camera fixing group 2. The fixed guide rail of the displacement slide 4 is fixed to the side wall of the camera fixing group 2 along the Z direction of the system (the vertical movement direction marked in the figure, that is, the extension direction of the optical main axis of the system, the height direction of the object to be measured). The movable slider of the displacement slide 4 is rigidly fixedly connected to the vertical connecting plate of the L-shaped connecting support plate 5. The horizontal connecting plate of the L-shaped connecting support plate 5 is rigidly docked and fixed to the top of the near object moving group 6. The main optical axis of the near object moving group 6 is coaxial with the main optical axis of the camera fixing group 2. The near object moving group 6, the movable slider of the displacement slide 4, and the L-shaped connecting support plate 5 maintain completely synchronized Z-direction displacement. The ultra-depth scanning imaging area 7 is the placement area of ​​the object to be measured, located within the object-side working distance of the near object moving group 6, and within the Z-direction scanning stroke coverage range of the near object moving group 6.

[0025] The camera 1 is used to acquire shallow depth-of-field images at different height positions; the camera fixing group 2 is a symmetrical rear objective lens group, used to refocus the parallel beam emitted from the near object moving group 6 and project it onto the photosensitive surface of the camera 1 to form a clear image; the coaxial illumination group 3 is used to provide a uniform and stable coaxial illumination source for the system; the displacement slide 4 is used to provide high-precision linear guidance for the Z-axis movement of the near object moving group 6; the L-shaped connecting support plate 5 is used to realize the complete synchronous displacement of the moving slider of the displacement slide 4 and the near object moving group 6; the near object moving group 6 is a symmetrical front objective lens group, used to receive the reflected light from the object under test and shape the diverging reflected light into a parallel beam for emission; the ultra-depth-of-field scanning imaging area 7 is used to place the object under test.

[0026] like Figure 2 As shown, the movable slider of the displacement slide 4 reciprocates linearly along the Z-axis of the system, and synchronously drives the L-shaped connecting support plate 5 to reciprocate linearly along the Z-axis of the system through rigid connection. The L-shaped connecting support plate 5 synchronously drives the near object moving group 6 to reciprocate linearly along the Z-axis of the system through rigid docking. The camera 1, camera fixing group 2, coaxial illumination group 3, and ultra-depth scanning imaging area 7 remain in fixed positions throughout the process.

[0027] The displacement slide 4 is controlled by a high-precision stepper motor, which adopts a closed-loop control method to provide real-time feedback on the motor rotation angle. The displacement slide 4 uses a ball screw drive structure with a minimum step distance of 1μm. The L-shaped connecting support plate 5 is made of high-strength aluminum alloy. The vertical connecting plate of the L-shaped connecting support plate 5 is rigidly fixed to the movable slider of the displacement slide 4 by bolts, and the horizontal connecting plate is coaxially connected to the aperture of the lens of the near-object moving group 6 by threads. To further improve the displacement accuracy, the displacement slide 4 is equipped with a grating ruler displacement sensor to collect the actual movement distance of the displacement slide 4 in real time and feed the data back to the software algorithm module.

[0028] like Figure 3As shown, the photosensitive surface of the built-in photosensitive chip of the camera 1 is the image plane 11 of the system, and the three-dimensional measured surface of the object under test, which is rigidly fixed in the ultra-depth-of-field scanning imaging area 7, is the object plane 71. The near-object moving group 6 and the camera fixed group 2 are two independent optical lens groups without direct mechanical connection, and are optically coupled through an optical path. The camera fixed group 2 includes an aperture 21, and the near-object moving group 6 includes an aperture 61. The aperture 61 of the near-object moving group 6 and the aperture 21 of the camera fixed group 2 are arranged coaxially opposite to each other along the main optical axis of the system, and the two groups are connected by a parallel light transmission optical path. The object-side working distance (i.e., the distance from the object surface 71 to its first lens) is constant. During the movement, the optical imaging relationship between the lens and the object under test is stable. The near object moving group 6 moves independently along the Z direction of the system, while the camera fixed group 2 remains stationary throughout the entire process. When the near object moving group 6 is in the initial scanning position, the aperture 61 of the near object moving group 6 is axially connected to the aperture 21 of the camera fixed group 2, and the distance between the two groups along the principal optical axis is 0 mm. After the near object moving group 6 moves, the aperture 61 of the near object moving group 6 separates from the aperture 21 of the camera fixed group 2, and its fixed object-side working distance synchronously scans different height areas of the object surface 71.

[0029] Among them, the field of view of both the object side and the image side is 100 fps. 30mm, overall magnification 1; object-space numerical aperture 0.125, matching the 610-650nm red light operating band, based on the depth-of-field calculation formula. The theoretical depth of field is 20. , λ is the wavelength, NA is the numerical aperture; the overall focal length of the system is 250mm, and the focal lengths of the near-object moving group 6 and the camera fixed group 2 are both 145.5mm.

[0030] like Figure 4 As shown, at the 0mm shift position, the MTF (modulation transfer function) curve is close to the diffraction limit across the entire field of view (TS 0.00mm to TS 15.00mm).

[0031] like Figure 5 As shown, at a 20mm moving position (maximum design moving distance), the MTF curve shows no significant attenuation compared to the MTF curve at a 0mm moving position, and the imaging quality remains stable across the entire field of view.

[0032] As mentioned above, within a movement range of 0-20mm, the system's imaging quality remains stable and reliable, meeting the requirements for image consistency during the scanning process.

[0033] like Figure 6As shown, the camera fixing group 2 has a built-in beam splitter prism 22, and the coaxial illumination group 3 integrates the fiber optic light source end face 31 and the aperture 32. The beam splitter prism 22 has a beam splitting ratio of 5:5 and is arranged between the aperture 21 of the camera fixing group 2 and the first lens of the camera fixing group 2 near the object side, and is arranged at 45° with the main optical axis of the system. In the imaging optical path, the reflected light from the object surface 71 passes through the near-object moving group 6, the transmission surface of the beam splitter prism 22, and the camera fixing group 2 in sequence, and is focused on the image plane 11 to form a clear image. In the illumination optical path, the illumination light is emitted from the fiber optic light source end face 31, limited by the aperture 32, collimated by the lens group of the coaxial illumination group 3, and then enters the beam splitter prism 22. After being reflected at 90° by the beam splitting surface, it is coaxial with the imaging optical path, and then focused by the near-object moving group 6 and emitted vertically to the object surface 71, so as to achieve shadowless uniform coaxial illumination of the object under test.

[0034] like Figure 7 As shown, the independent illumination optical path of the coaxial illumination group 3 consists of the fiber optic light source end face 31, the aperture 32, and multiple collimating lens groups arranged coaxially along the main optical axis of the illumination optical path of the coaxial illumination group 3 itself. The fiber optic light source end face 31 is the light source emission end of the illumination optical path and is arranged at the incident end of the optical path. The aperture 32 is arranged at the converging pupil position of the lens group and is arranged coaxially with the main optical axis of the illumination optical path of the coaxial illumination group 3 itself. The diverging illumination light emitted from the fiber optic light source end face 31 is converged and shaped by the front lens group, and then the aperture 32 limits the beam aperture and filters out stray light. It is then collimated into a uniform parallel beam by the rear lens group and emitted, forming an illumination optical path that conforms to the Kohler lighting design concept. It is coupled with the imaging optical path to ensure the uniformity of illumination brightness across the entire field of view of the object surface.

[0035] The measurement system in this embodiment operates as follows: The object under test is rigidly fixed within the ultra-depth-of-field scanning imaging area 7. The three-dimensional measured surface (object surface 71) of the object is completely within the object-side working distance of the near-object movement group 6, and covers the maximum Z-axis scanning travel range (20mm) of the near-object movement group 6 throughout its entire range. The software algorithm module pre-configures the basic imaging parameters of the camera 1 and the light source power of the coaxial illumination group 3 based on the surface reflection characteristics and height range of the object under test, and automatically plans the scanning path and sets the step distance. The software algorithm module sends displacement commands to the high-precision stepper motor that drives the displacement slide 4 according to the automatically planned scanning path and step distance. The high-precision stepper motor drives the ball screw to rotate, causing the moving slider of the displacement slide 4 to move along the Z-axis of the system. The moving slider synchronously drives the lens of the near-object movement group 6 to move along the Z-axis of the system to the preset height position through the L-shaped connecting support plate 5. During the process, the grating ruler displacement sensor collects actual displacement data in real time and feeds it back to the software algorithm module. The software module dynamically adjusts the speed of the high-precision stepper motor by comparing the preset displacement amount with the actual displacement amount to compensate for transmission errors. After the displacement of the near-object moving group 6 stabilizes, the software algorithm module triggers the camera 1 to perform image acquisition according to the pre-configured basic imaging parameters, simultaneously locks and records the height coordinate data of the current position, and acquires shallow depth-of-field images at a single height position. The above displacement acquisition operation is repeated until the near-object moving group 6 completes the full-stroke scan, and its constant object-side working distance completely scans all height areas of the object surface 71, obtaining a multi-height shallow depth-of-field image set with height labels. The software algorithm module processes the multi-height shallow depth-of-field image set with height labels, and performs ultra-depth-of-field 3D fusion reconstruction through a depth-of-field synthesis algorithm to output a full-field, large-depth-of-field 3D model image.

[0036] Example 2 like Figure 8 As shown, Embodiment 2 of this application provides a high-precision measurement method for ultra-depth of field based on a symmetrical objective lens, applied in the software algorithm module of the ultra-depth of field high-precision measurement system based on a symmetrical objective lens, including: Step S1: Based on the parallel light transmission characteristics of the symmetrical objective lens, plan the total scanning stroke, adaptively set the scanning step distance based on the system depth of field and displacement accuracy constraints, and generate a full sequence of scanning point sets; Furthermore, based on the parallel light transmission characteristics of the symmetrical objective lens, the total scanning stroke is planned, and the scanning step distance is adaptively set based on the system depth of field and displacement accuracy constraints. The generation of the full sequence of scanning points includes the following sub-steps: Step S11: Control the object movement group to perform a pre-scan of the object to be tested, and determine the total scanning distance based on the sharpness change curve of the image acquired by the camera during the pre-scan. Specifically, the object under test is rigidly fixed in the ultra-depth-of-field scanning imaging area. Based on the estimated height range of the object under test, a wide-range pre-scan stroke covering its entire height is set. The near-object movement group is controlled to perform a full-range pre-scan within the wide-range pre-scan stroke. Based on the sharpness change curve of the images acquired by the camera during the pre-scan, the global sharpness value of each frame image is calculated through the sharpness evaluation function. The Z-coordinates of the top and bottom of the object surface corresponding to the sharpness peak are determined. The difference between the two coordinates is the total scanning stroke of the object under test. The sharpness evaluation function can be any one of the variance function, Laplace function, or Tenan gradient function, preferably the Tenan gradient function, which has strong resistance to noise interference.

[0037] Step S12: Based on the minimum step distance of the displacement slide and the theoretical depth of field of the symmetrical objective lens, automatically set the optimal scanning step distance and generate a full sequence of scanning point sets; Specifically, based on the minimum step distance of the displacement slide and the theoretical depth of field of the symmetrical objective lens, a dual constraint condition for the optimal scanning step distance is set. ,in, To achieve the optimal scan step distance, The value is a positive integer, ensuring that the optimal scanning step distance is an integer multiple of the minimum step distance of the displacement slide. This represents the minimum step distance of the displacement slide. This is the overlap coefficient, whose value ensures that the depth-of-field overlap rate between adjacent scan positions is not less than the overlap threshold. To achieve the theoretical depth of field of a symmetrical objective lens, this embodiment... It is a value , With the goal of minimizing the total number of scan layers, find the optimal positive integer that satisfies the double constraints. Obtain the optimal step Generate full sequence scan points ,in, For the first Each scan point The coordinate of the bottom of the object is the Z-axis. To achieve the optimal scan step distance, the total number of scan layers is: , This represents the total number of layers scanned. To scan the total travel distance, Each scanning point The data is aggregated to form a set of scan points for the entire sequence. .

[0038] Step S2: Obtain the surface reflection type of the object under test, combine the optical parameters of the symmetrical objective lens, configure the camera imaging parameters and coaxial illumination group parameters, and enable the coaxial illumination group. Furthermore, obtaining the surface reflection type of the object under test, combining the optical parameters of the symmetrical objective lens, configuring the camera imaging parameters and coaxial illumination group parameters, and enabling the coaxial illumination group includes the following sub-steps: Step S21: Trigger the camera to perform single-frame pre-acquisition, and identify the surface reflection type of the object to be tested based on the grayscale statistical characteristics of the pre-acquisition image; Specifically, the camera is pre-configured by setting the camera pixel format to 8-bit grayscale, triggering the camera to perform single-frame pre-acquisition, acquiring an 8-bit grayscale pre-acquisition image, performing grayscale histogram statistics on the image, calculating the average grayscale value of the image, comparing it with a preset threshold, and classifying the surface into three categories. When the average grayscale value is lower than the weak reflection threshold, the object under test is determined to be a weakly reflective surface (such as black plastic or matte metal). When the average grayscale value is not lower than the weak reflection threshold and not higher than the strong reflection threshold, the object under test is determined to be a conventional reflective surface. When the average grayscale value is higher than the strong reflection threshold, the object under test is determined to be a strongly reflective surface (such as mirror metal or highly reflective coated parts).

[0039] Step S22: Based on the surface reflection type of the object under test, and combined with the optical parameters of the symmetrical objective lens, configure the camera imaging parameters; Specifically, the average grayscale value of the pre-acquired image is used as a benchmark and compared with the preset target grayscale value. Based on the degree of deviation between the two, the exposure time is adjusted according to the preset mapping relationship until the overall brightness of the image approaches the target grayscale range. Since this system only moves the near object movement group during the scanning process, the system magnification and aperture value remain unchanged. The image brightness is independent of the change in distance from the object surface. Therefore, once the exposure time is set, it can be applied to all scanning height positions without the need for repeated adjustment during each layer of scanning.

[0040] Step S23: Obtain ambient lighting information, combine it with the surface reflection type of the object under test, match and configure the light source power of the coaxial illumination group, and enable the coaxial illumination group according to the configured power; Specifically, for objects under test with weak reflectivity or measurement environments with insufficient lighting, the coaxial illumination group is enabled and configured with a higher light source output power; for objects under test with normal reflectivity, the coaxial illumination group is enabled and configured with a moderate light source output power; for objects under test with strong reflectivity, the coaxial illumination group is turned off and the measurement ambient light imaging mode is adopted.

[0041] Step S3: Based on the total scanning travel, scanning step distance and full sequence scanning point set, drive the near object moving group to move to the target scanning point in sequence. After online error compensation, trigger the camera to acquire single-height shallow depth-of-field images of the target scanning point and obtain a multi-height shallow depth-of-field image set with height labels. Furthermore, based on the total scanning distance, scanning step distance, and the full sequence of scanning points, the near-object movement group is driven to move sequentially to the target scanning point. After online error compensation, the camera is triggered to acquire a single-height shallow depth-of-field image of the target scanning point. Obtaining a multi-height shallow depth-of-field image set with height labels includes the following sub-steps: Step S31: Send the target scanning point command to the high-precision stepper motor of the driving displacement slide according to the height sorting of the scanning point set, drive the displacement slide, and drive the near object moving group to move synchronously along the Z direction through the L-shaped connecting support plate. The grating ruler displacement sensor collects the actual displacement of the displacement slide in real time. Specifically, the height sorting is determined according to actual needs, including ascending height order and descending height order.

[0042] Step S32: After the near object moving group moves to the target scanning point, compare the preset displacement of the target scanning point with the actual displacement, perform online compensation for position error, trigger the camera to acquire images, and simultaneously record the current height coordinates to form a single-height shallow depth-of-field image with height label. Specifically, when the near-object moving group moves to the target scanning point... Subsequently, based on the characteristics that the near-object moving group and the camera fixed group have parallel optical paths and that the image plane position is insensitive to the slight lateral shift of the near-object moving group, the target scanning point position is monitored in real time. The camera preview image, pre-selected fixed high-contrast feature points within the field of view, and the target scanning point position are used. The system monitors the changes in the lateral coordinates of feature points in the real-time preview image. The average of the changes in all feature points is taken as the final lateral offset. If the final lateral offset exceeds a preset threshold, the displacement slide is deemed to have an error. Based on the geometric relationship of parallel light transmission, the sway angle of the displacement slide is calculated. ,in, The tilt angle of the displacement slide. This is the final lateral offset. The overall focal length of the system is based on the tilt angle of the displacement slide. Calculate the Z-direction displacement compensation amount ,in, This is the Z-axis displacement compensation amount. The fixed lever arm length of the L-shaped connecting plate is based on the displacement compensation amount. Amendment No. Target scanning points ,in, For the first time before the correction Target scanning points For the revised first The target scanning points; based on the corrected first... Target scanning points The drive parameters of the high-precision stepper motor are dynamically adjusted to correct the motion posture of the displacement slide until the final lateral offset returns to the threshold range. When the posture of the near object moving group at the target scanning point is stable, the camera is triggered to acquire a single-height shallow depth-of-field image and simultaneously record the height coordinates of the target scanning point as a height label, which is then bound and stored with the image.

[0043] Step S33: Repeat steps S31 to S32 until all scan points in the full sequence scan point set are traversed to obtain a set of multi-height shallow depth-of-field images with height labels. Step S4: Using an image fusion and stitching algorithm, extract the clear areas from each image in the multi-height shallow depth-of-field image set with height labels, stitch and fuse them to generate a three-dimensional model image; Furthermore, by using an image fusion and stitching algorithm, the sharp regions of each image in the multi-height shallow depth-of-field image set with height labels are extracted, and then stitched and fused to generate a 3D model image, including the following sub-steps: Step S41: Perform image denoising and spatial registration on the multi-height shallow depth-of-field image set with height labels; Specifically, a Gaussian filtering algorithm is used to denoise each image in the multi-height shallow depth-of-field image set with height labels, eliminating noise interference during image acquisition. If the maximum lateral offset within the total scanning distance is less than a preset threshold, the multi-height shallow depth-of-field image set is deemed to meet the spatial alignment requirements, and image registration is skipped. If there is a lateral offset exceeding the preset threshold, the registration model is used. Registration was performed on a set of images with multiple heights and shallow depths of field, among which, To obtain the pixel coordinates of the registered image, These are the pixel coordinates of the original image. These are the lateral and longitudinal translation vectors obtained using the phase correlation method.

[0044] Step S42: Calculate the pixel-by-pixel sharpness evaluation value of each image in the multi-height shallow depth-of-field image set after denoising and registration, extract the sharp area at each pixel position, and stitch and fuse them into a three-dimensional model image of the object to be tested. Specifically, through improved Laplace energy and function The sharpness evaluation value of the entire image sequence is calculated element by element, where, height coordinates In the corresponding image, pixel position Clarity rating, The adaptive weighting coefficients are calculated based on the gradient magnitude of pixels within the window, assigning high weights to high-gradient regions and low weights to low-gradient regions. For A sliding window centered on the user, with the window size preferably... or ; The Laplacian operator is used to extract edge detail information from an image. height coordinates In the corresponding image, pixel position The grayscale value for each pixel position The height coordinates corresponding to the maximum sharpness evaluation value are taken as the depth value of the pixel to generate an unbiased depth map. Based on the unbiased depth map, the sharpest gray value of each pixel position is extracted, and a full-field, full-focus 2D image is synthesized. Combining the system's fixed magnification and camera pixel size, the pixel depth is converted into actual physical 3D coordinates to generate a 3D high-precision point cloud model of the surface of the object under test and construct a 3D model image.

[0045] Corresponding to the above embodiments, the present invention provides a computer storage medium, including: at least one memory and at least one processor; The memory is used to store one or more program instructions; A processor for running one or more program instructions to execute a high-precision measurement method for ultra-depth of field based on symmetrical objectives.

[0046] Corresponding to the above embodiments, the present invention provides a computer-readable storage medium containing one or more program instructions, which are used by a processor to provide a high-precision measurement method for ultra-depth of field based on a symmetrical objective lens.

[0047] The embodiments disclosed in this invention provide a computer-readable storage medium storing computer program instructions. When the computer program instructions are executed on a computer, the computer performs the above-described method for high-precision measurement of depth of field based on a symmetrical objective lens.

[0048] In this embodiment of the invention, the processor can be an integrated circuit chip with signal processing capabilities. The processor can be a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.

[0049] The various methods, steps, and logic diagrams disclosed in the embodiments of this invention can be implemented or executed. The general-purpose processor can be a microprocessor or any conventional processor. The steps of the methods disclosed in the embodiments of this invention can be directly implemented by a hardware decoding processor, or implemented by a combination of hardware and software modules in the decoding processor. The software modules can reside in random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, registers, or other mature storage media in the art. The processor reads information from the storage medium and, in conjunction with its hardware, completes the steps of the above methods.

[0050] The storage medium can be memory, such as volatile memory or non-volatile memory, or may include both volatile and non-volatile memory.

[0051] Among them, non-volatile memory can be read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), or flash memory.

[0052] Volatile memory can be random access memory (RAM), which is used as an external cache. By way of example, but not limitation, many forms of RAM are available, such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDRSDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous linked dynamic random access memory (Synchlink DRAM, SLDRAM), and direct memory bus RAM (DRRAM).

[0053] The storage media described in the embodiments of the present invention are intended to include, but are not limited to, these and any other suitable types of memory.

[0054] Those skilled in the art will recognize that, in one or more of the examples above, the functions described in this invention can be implemented using a combination of hardware and software. When applied as software, the corresponding functions can be stored in a computer-readable medium or transmitted as one or more instructions or code on a computer-readable medium. Computer-readable media include computer storage media and communication media, wherein communication media include any medium that facilitates the transmission of computer programs from one place to another. Storage media can be any available medium that can be accessed by a general-purpose or special-purpose computer.

[0055] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made on the basis of the technical solution of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-precision measurement system for ultra-depth of field based on a symmetrical objective lens, characterized in that, include: Camera (1), camera fixing group (2), coaxial illumination group (3), displacement slide (4), L-shaped connecting support plate (5), near object movement group (6), ultra-depth scanning imaging area (7), and software algorithm module that coordinates the work of each hardware component; The camera fixing group (2) is rigidly connected to the bottom end of the camera (1). The camera fixing group (2) and the camera (1) remain fixed throughout the entire process. The output light path of the camera fixing group (2) is matched with the position of the photosensitive surface of the camera (1). The coaxial illumination group (3) is integrated and installed in the side cavity of the camera fixing group (2). The fixed guide rail of the displacement slide (4) is fixed to the side wall of the camera fixing group (2) along the Z direction of the system. The movable slider of the displacement slide (4) is rigidly fixedly connected to the vertical connecting plate of the L-shaped connecting support plate (5). The horizontal connecting plate of the L-shaped connecting support plate (5) is rigidly connected and fixed to the top of the near object moving group (6). The main optical axis of the near object moving group (6) is coaxial with the main optical axis of the camera fixing group (2). The near object moving group (6) and the movable slider of the displacement slide (4) and the L-shaped connecting support plate (5) maintain completely synchronized Z-direction displacement. The ultra-depth scanning imaging area (7) is the placement area of ​​the object to be measured, located within the object-side working distance of the near object moving group (6), and within the Z-direction scanning stroke coverage range of the near object moving group (6). The photosensitive surface of the built-in photosensitive chip of the camera (1) is the image plane (11) of the system, and the three-dimensional measured surface of the object to be measured, which is rigidly fixed in the super depth-of-field scanning imaging area (7), is the object plane (71). The near-object moving group (6) and the camera fixed group (2) are two independent optical lens groups that are optically coupled through an optical path. The camera fixed group (2) includes a first aperture (21), and the near-object moving group (6) includes a second aperture (61). The second aperture (61) of the near-object moving group (6) and the first aperture (21) of the camera fixed group (2) are arranged coaxially opposite to each other along the main optical axis of the system, and the two groups are connected by parallel light transmission. The object-side working distance of the near-object moving group (6) is constant. During the movement, the optical imaging relationship between the lens and the object under test is stable. The near-object moving group (6) moves independently along the Z direction of the system, while the camera fixed group (2) remains stationary throughout the process. When the near-object moving group (6) is in the initial scanning position, the second aperture (61) of the near-object moving group (6) is axially connected to the first aperture (21) of the camera fixed group (2). After the near-object moving group (6) moves, the second aperture (61) of the near-object moving group (6) separates from the first aperture (21) of the camera fixed group (2), and its fixed object-side working distance synchronously scans different height areas of the object surface (71). The camera fixing group (2) has a built-in beam splitter (22), and the coaxial illumination group (3) integrates the fiber optic light source end face (31) and the third aperture (32). The first aperture (21) of the camera fixing group (2) is arranged between the first lens of the camera fixing group (2) near the object side. In the imaging optical path, the reflected light from the object surface (71) passes through the near object moving group (6), the transmission surface of the beam splitter (22), and the camera fixing group (2) in sequence, and is focused on the image plane (11) for clear imaging. In the illumination optical path, the illumination light is emitted from the fiber optic light source end face (31), then limited by the third aperture (32), collimated by the lens group of the coaxial illumination group (3), and then incident on the beam splitter (22). After being reflected by the beam splitter, it is coaxial with the imaging optical path, and then focused by the near object moving group (6) and emitted vertically to the object surface (71).

2. The ultra-depth-of-field high-precision measurement system based on a symmetrical objective lens as described in claim 1, characterized in that, The camera (1) is used to acquire shallow depth-of-field images at different height positions; the camera fixing group (2) is a symmetrical objective lens rear group, used to refocus the parallel beam emitted from the near object moving group (6) and project it onto the photosensitive surface of the camera (1) to form a clear image; the coaxial illumination group (3) is used to provide a uniform and stable coaxial illumination source for the system; the displacement slide (4) is used to provide high-precision linear guidance for the Z-axis movement of the near object moving group (6); the L-shaped connecting plate (5) is used to realize the complete synchronous displacement of the moving slider of the displacement slide (4) and the near object moving group (6); the near object moving group (6) is a symmetrical objective lens front group, used to receive the reflected light from the object under test and shape the divergent reflected light into a parallel beam for emission; The super depth-of-field scanning imaging area (7) is used to place the object to be tested.

3. The ultra-depth-of-field high-precision measurement system based on a symmetrical objective lens as described in claim 1, characterized in that, The movable slider of the displacement slide (4) moves in a straight line along the Z direction of the system. Through rigid connection, it drives the L-shaped connecting support plate (5) to move in a straight line along the Z direction of the system. The L-shaped connecting support plate (5) drives the near object moving group (6) to move in a straight line along the Z direction of the system through rigid docking. The camera (1), camera fixing group (2), coaxial illumination group (3), and ultra-depth scanning imaging area (7) remain in a fixed position throughout the process.

4. The ultra-depth-of-field high-precision measurement system based on a symmetrical objective lens as described in claim 1, characterized in that, The independent illumination optical path of the coaxial illumination group (3) consists of the fiber optic light source end face (31), the third aperture (32), and multiple collimating lens groups arranged coaxially along the main optical axis of the illumination optical path of the coaxial illumination group (3). The fiber optic light source end face (31) is the light source emission end of the illumination optical path and is arranged at the incident end of the optical path. The third aperture (32) is arranged at the converging pupil position of the lens group and is arranged coaxially with the main optical axis of the illumination optical path of the coaxial illumination group (3). The diverging illumination light emitted from the fiber optic light source end face (31) is converged and shaped by the front lens group, and then the third aperture (32) limits the beam aperture and filters out stray light. It is then collimated into a uniform parallel beam by the rear lens group and emitted to form the illumination optical path, which is coupled with the imaging optical path.

5. A high-precision measurement method for ultra-depth of field based on a symmetrical objective lens, applied in the software algorithm module of a high-precision measurement system for ultra-depth of field based on a symmetrical objective lens as described in any one of claims 1-4, characterized in that, include: Step S1: Based on the parallel light transmission characteristics of the symmetrical objective lens, plan the total scanning stroke, adaptively set the scanning step distance based on the system depth of field and displacement accuracy constraints, and generate a full sequence of scanning point sets; Step S2: Obtain the surface reflection type of the object under test, combine the optical parameters of the symmetrical objective lens, configure the camera imaging parameters and coaxial illumination group parameters, and enable the coaxial illumination group; Step S3: Based on the total scanning travel, scanning step distance and full sequence scanning point set, drive the near object moving group to move to the target scanning point in sequence. After online error compensation, trigger the camera to acquire single-height shallow depth-of-field images of the target scanning point and obtain a multi-height shallow depth-of-field image set with height labels. Step S4: Using an image fusion and stitching algorithm, extract the clear areas from each image in the multi-height shallow depth-of-field image set with height labels, stitch and fuse them to generate a 3D model image.

6. The ultra-depth-of-field high-precision measurement method based on a symmetrical objective lens as described in claim 5, characterized in that, Based on the parallel light transmission characteristics of symmetrical objectives, the total scanning stroke is planned, and the scanning step distance is adaptively set based on system depth of field and displacement accuracy constraints. The generation of the full sequence of scanning point sets includes the following sub-steps: Step S11: Control the near-object movement group to perform a pre-scan of the object under test, and determine the total scanning distance based on the sharpness change curve of the image acquired by the camera during the pre-scan. Step S12: Based on the minimum step distance of the displacement slide and the theoretical depth of field of the symmetrical objective lens, automatically set the optimal scanning step distance and generate a full sequence of scanning point sets.

7. The ultra-depth-of-field high-precision measurement method based on a symmetrical objective lens as described in claim 5, characterized in that, Based on the total scanning travel, scanning step distance, and the full sequence of scanning points, the near-object movement group is driven to move sequentially to the target scanning point. After online error compensation, the camera is triggered to acquire a single-height shallow depth-of-field image of the target scanning point. Obtaining a multi-height shallow depth-of-field image set with height labels includes the following sub-steps: Step S31: Send the target scanning point command to the high-precision stepper motor of the driving displacement slide according to the height sorting of the scanning point set, drive the displacement slide, and drive the near object moving group to move synchronously along the Z direction through the L-shaped connecting support plate. The grating ruler displacement sensor collects the actual displacement of the displacement slide in real time. Step S32: After the near object moving group moves to the target scanning point, compare the preset displacement of the target scanning point with the actual displacement, perform online compensation for position error, trigger the camera to acquire images, and simultaneously record the current height coordinates to form a single-height shallow depth-of-field image with height label. Step S33: Repeat steps S31 to S32 until all scan points in the full sequence scan point set are traversed to obtain a set of multi-height shallow depth-of-field images with height labels.

8. The ultra-depth-of-field high-precision measurement method based on a symmetrical objective lens as described in claim 5, characterized in that, The process of extracting sharp regions from multiple images in a multi-height shallow depth-of-field image set with height labels using an image fusion and stitching algorithm to generate a 3D model image includes the following sub-steps: Step S41: Perform image denoising and spatial registration on the multi-height shallow depth-of-field image set with height labels; Step S42: Calculate the sharpness evaluation value pixel by pixel for each image in the multi-height shallow depth-of-field image set after denoising and registration, extract the sharp area at each pixel position, and stitch and fuse them into a three-dimensional model image of the object to be tested.

Images