VIN secondary marking polarization detection device

Abstract

The utility model provides a kind of VIN secondary marking polarization detection device, it includes: fixed unit;Posture adjustment unit provides mutually orthogonal first translational degree of freedom and second translational degree of freedom, along the lift degree of freedom of imaging optical axis and the angle fine adjustment of lockable;Coaxial imaging unit includes imaging collector, coaxial partition controllable illumination, the first polaroid of setting in illumination light path, the second polaroid of setting in imaging light path and the elastic diaphragm of being located at light outlet end and being adhered with the surface of being examined;Control unit, with imaging collector and coaxial partition controllable illumination electric connection to realize the synchronous trigger of illumination and imaging;Wherein, coaxial partition controllable illumination and imaging collector are fixedly installed by coaxial positioning structure, so that the coaxiality of illumination optical axis and imaging optical axis is not more than 0.2 mm;The first polaroid and the second polaroid are installed on angle adjusting seat, and the relative angle of the polarization axis of two is adjustable;The axial compression amount of elastic diaphragm under adhered state is 0.5-2 mm.

Description

Technical Field

[0001] This utility model relates to the field of automotive testing equipment technology, and in particular to a VIN secondary marking polarization detection device. Background Technology

[0002] The Vehicle Identification Number (VIN) is a unique identifier for a vehicle, playing a crucial role in vehicle production, sales, maintenance, and supervision. To enhance anti-counterfeiting and traceability capabilities, some vehicles require "secondary stamping" on key areas of the engine compartment and body, i.e., an additional VIN code is engraved on top of the original nameplate. Current detection methods primarily rely on ordinary industrial cameras or handheld inspection lamps, using strong light illumination and image acquisition to identify the stamped characters. In laboratory environments, there are also detection methods based on polarization imaging, which utilize image differences at different polarization angles to suppress reflection interference, thereby enhancing the contrast of the stamped characters. These technologies are typically applied to fixed inspection platforms, resulting in large, complex devices suitable for relatively spacious inspection environments.

[0003] However, in actual vehicle-mounted inspection environments, the above methods have significant shortcomings: First, the secondary stamping location is often inside the engine compartment or in narrow gaps in the vehicle body structure, where space is limited, making it difficult to flexibly arrange and fix traditional cameras and supplementary lighting devices; second, the vehicle body surface is mostly metal or painted, resulting in severe glare and insufficient contrast in ordinary imaging, leading to blurred character edges; third, existing polarization imaging equipment is mostly based on experimental platforms, which are bulky and dependent on external support structures, making them unsuitable for rapid deployment on-site; fourth, some detection methods lack light-shielding measures that fit snugly against the vehicle body, making them susceptible to interference from ambient light and resulting in unstable imaging. These problems severely restrict the rapid and reliable detection of VIN code secondary stamping.

[0004] To address the aforementioned issues, this invention proposes a VIN secondary marking polarization detection device. While ensuring image quality, it achieves stable coaxial illumination and precise framing of the marking area, and supports rapid on-site installation and secure fixation. Thus, while ensuring image quality, it significantly improves detection efficiency and applicability, meeting the needs of regulatory and inspection departments. Utility Model Content

[0005] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, one objective of this invention is to provide a VIN secondary etching polarization detection device in one possible embodiment, comprising: a fixing unit; an attitude adjustment unit providing mutually orthogonal first and second translational degrees of freedom, vertical and horizontal degrees of freedom along the imaging optical axis, and lockable angle fine-tuning; a coaxial imaging unit including an imaging acquisition unit, coaxial partitioned controllable illumination, a first polarizer disposed in the illumination optical path, a second polarizer disposed in the imaging optical path, and an elastic light-shielding ring located at the light-emitting end that can be attached to the surface under inspection; and a control unit electrically connected to the imaging acquisition unit and the coaxial partitioned controllable illumination to achieve synchronous triggering of illumination and imaging; wherein, the coaxial partitioned controllable illumination and the imaging acquisition unit are fixedly installed through a coaxial positioning structure, such that the coaxiality between the illumination optical axis and the imaging optical axis is no greater than 0.2 mm; the first polarizer and the second polarizer are mounted on an angle adjustment seat, and the relative angle between their polarization axes is adjustable; the axial compression of the elastic light-shielding ring in the attached state is 0.5–2 mm.

[0006] In one possible implementation, the fixing unit is a triangular base, with support foot mounting positions provided at the three corners of the base. Each support foot mounting position is equipped with a support foot assembly, which is connected to the base via a quick-connect connection, which can be either a snap-fit ​​type or a rotary lock type.

[0007] In one possible implementation, the support foot assembly includes a support foot body and a support foot end piece installed at the lower end of the support foot body, wherein the support foot end piece is any one of a magnetic end piece, a vacuum adsorption end piece, or an anti-slip rubber end piece.

[0008] In one possible implementation, the posture adjustment unit includes an X-axis linear slide and a Y-axis linear slide, with the Y-axis linear slide mounted on the X-axis linear slide in a stacked arrangement. The X-axis linear slide and the Y-axis linear slide are respectively provided with locking members for locking the position.

[0009] In one possible implementation, the posture adjustment unit further includes a Z-axis lifting mechanism, which is mounted on the Y-axis linear slide, has a scale indicator, and is finely adjusted by a micrometer head, with a Z-axis travel of 10–80 mm.

[0010] In one possible implementation, the attitude adjustment unit is provided with a two-degree-of-freedom gimbal at its end. The gimbal is installed at the output end of the Z-axis lifting mechanism and can realize the angle adjustment in the pitch and yaw directions, with an adjustment range of ±10°. Angle locking components are provided in the pitch and yaw directions respectively.

[0011] In one possible implementation, the coaxial zone controllable illumination is a ring-shaped four-quadrant structure, with each of the four quadrants controlled by an independent drive channel; the coaxial zone controllable illumination and the imaging acquisition unit are fixedly installed through a positioning structure consisting of a coaxial sleeve, a thrust end face, and a radial positioning pin, so that the coaxiality between the illumination optical axis and the imaging optical axis is no more than 0.2 mm.

[0012] In one possible implementation, the control unit includes a timing trigger control box, which is equipped with a camera trigger interface and a flash synchronization interface. The interface is TTL level, the trigger edge is a rising edge, the minimum system response time is no more than 5 ms, and the trigger jitter is no more than ±50 μs.

[0013] In one possible implementation, the coaxial imaging unit includes a drawer-type filter holder that can be inserted and removed in a direction orthogonal to the imaging optical axis, capable of accommodating filters of any size among 1 mm, 2 mm, and 3 mm thickness, and is provided with a stop and positioning structure to limit the insertion direction and prevent reverse or misaligned installation.

[0014] In one possible implementation, a light-shielding tube is provided at the front end of the coaxial imaging unit, and an annular elastic light-shielding ring is installed at the light-emitting end of the light-shielding tube. The elastic light-shielding ring is made of silicone, and its axial compression when it is attached to the surface being inspected is 0.5–2 mm. The elastic light-shielding ring can be replaced and installed through a slot structure.

[0015] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Based on the above technical solution, the VIN secondary marking polarization detection device provided by this utility model ensures precise alignment between the imaging optical axis and the marking area through the multi-degree-of-freedom adjustment capability provided by the attitude adjustment unit; the coaxial imaging unit, combined with coaxial partitioned controllable illumination and adjustable polarizer components, achieves adaptive imaging for different surface reflection characteristics; the elastic light-shielding ring adheres to the surface under inspection, effectively shielding against ambient stray light interference; the imaging acquisition unit and illumination device are installed through a high coaxiality positioning structure, and the control unit realizes synchronous triggering of illumination and imaging, thereby ensuring image quality while achieving stable coaxial illumination and precise framing of the marking area, improving the contrast and clarity of the detected image. The overall structure of this device supports rapid deployment and stable fixation, significantly improving detection efficiency and applicability, and meeting the imaging detection needs of regulatory and inspection departments in practical work. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this utility model 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 some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 A schematic diagram of the structure of a VIN secondary etching polarization detection device from a first-view perspective, provided for an embodiment of this utility model; Figure 2 for Figure 1 A top view of the device shown. Figure 3 for Figure 1 A schematic diagram of the device shown from a second perspective; Figure 4 for Figure 3 A magnified view of region A in the middle.

[0018] Explanation of reference numerals in the attached figures: 1. Fixing unit; 2. Attitude adjustment unit; 3. Coaxial imaging unit; 4. Imaging acquisition unit; 5. Coaxial zone controllable illumination; 6. First polarizer; 7. Second polarizer; 8. Elastic light shield; 9. Control unit; 10. Base; 11. Support foot assembly; 12. Support foot body; 13. Support foot end piece; 14. X-axis linear slide; 15. Y-axis linear slide; 16. Z-axis lifting mechanism. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0020] In the description of this utility model, it should be understood that the terms "center," "longitudinal," "transverse," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, features defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0021] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0022] The embodiments of this utility model are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0023] Figure 1 A schematic diagram of the structure of a VIN secondary etching polarization detection device from a first-view perspective, provided for an embodiment of this utility model; Figure 2 for Figure 1 A top view of the device shown. Figure 3 for Figure 1 A schematic diagram of the device shown from a second perspective; Figure 4 for Figure 3 A magnified view of region A in the middle.

[0024] Please see Figure 1-4In one possible implementation, a VIN secondary etching polarization detection device includes a fixing unit 1; an attitude adjustment unit 2, providing mutually orthogonal first and second translational degrees of freedom, vertical and horizontal degrees of freedom along the imaging optical axis, and lockable angle fine adjustment; a coaxial imaging unit 3, including an imaging acquisition unit 4, a coaxial partitioned controllable illumination 5, a first polarizer 6 disposed in the illumination optical path, a second polarizer 7 disposed in the imaging optical path, and an elastic light-shielding ring 8 located at the light-emitting end and capable of adhering to the surface under inspection; and a control unit 9, electrically connected to the imaging acquisition unit 4 and the coaxial partitioned controllable illumination 5 to achieve synchronous triggering of illumination and imaging; the coaxial partitioned controllable illumination 5 and the imaging acquisition unit 4 are fixedly installed through a coaxial positioning structure, so that the coaxiality between the illumination optical axis and the imaging optical axis is no greater than 0.2 mm; the first polarizer 6 and the second polarizer 7 are mounted on an angle adjustment seat, and the relative angle between their polarization axes is adjustable; the axial compression of the elastic light-shielding ring 8 in the adhering state is 0.5–2 mm. Preferably, the imaging acquisition device 4 is an industrial camera with a fixed-focus or telecentric lens, and the working distance is selected according to the geometric dimensions of the inspected part; the coaxial zone controllable illumination 5 uses a narrow-band high color index LED, and the center wavelength matches the reflection spectrum of the inspected material to improve texture contrast.

[0025] When a vehicle's metal substrate and its coating form oriented microgrooves and residual stress zones after initial etching, grinding, repainting, or secondary etching can reshape the surface geometry, but the underlying micro-orientation and strain distribution are difficult to perfectly match, leading to differences in the specular / diffuse reflection ratio and polarization retention. This device uses coaxial geometry to incident linearly polarized illumination onto the inspected surface. The specular component mostly retains its original polarization state, while the edge of the etch and the residual deformation band generate depolarized or polarization-rotated scattering components. The second polarizer 7 in the imaging channel acts as an analyzer, and is aligned to near cross with the first polarizer 6. This significantly suppresses the clear coat and metallic highlights, retaining only the scattering related to the micro-morphology, thereby amplifying the brightness and texture differences between the covered, replicated, or re-etched strokes and the background. The ring-shaped zone illumination is driven independently by each quadrant. While maintaining coaxial incidence, it changes the incidence orientation to perform azimuth scanning of anisotropic microgrooves, further highlighting stroke boundaries and fine strokes. The elastic light-shielding ring 8 fits to form a local darkroom, shielding ambient stray light. Combined with synchronous triggering, it avoids exposure drift, allowing weak contrast details to be stably displayed.

[0026] Specifically, during use, the fixed unit 1 positions the coaxial imaging unit 3 and the attitude adjustment unit 2 as an integrated module on the workstation. The operator first uses the attitude adjustment unit 2 to perform translational positioning in the X and Y directions, ensuring that the imaging optical axis passes through the geometric center of the target marking area; then, the operator fine-tunes the working distance along the Z direction and corrects the pitch and yaw using the angle fine-tuning mechanism, making the imaging optical axis essentially perpendicular to the surface being inspected. The light emitted from the illumination end is linearly polarized at the first polarizer 6 and then coaxially illuminates the surface being inspected. The specular and diffuse reflection components of the surface return to the imaging channel, are selectively transmitted through the second polarizer 7, and are then captured by the imaging acquisition unit 4. By changing the relative angle of the two polarizers, a balance is achieved between suppressing specular reflection glare and enhancing the scattering of the marking edges; when using a near-crossing state, it effectively suppresses highlights and oil film reflections to improve the contrast of dark lines in the markings; when using a small angle state deviating from the near-crossing state, it can enhance fine and shallow strokes on a low-contrast substrate. Before acquisition, the elastic light-shielding ring 8 is gently pressed against the surface to be inspected, creating an axial compression of 0.5–2 mm to form a local dark field and block stray ambient light from entering the optical path. The control unit 9 coordinates the timing of the illumination and camera: first, a stable pulse light intensity is established, then imaging exposure is triggered, and the illumination is turned off after the exposure, thus obtaining a consistent image even when mechanical vibration and ambient light changes are present. Preferably, the two polarizers are linear polarizers with an extinction ratio ≥1:500 and equipped with a scale angle holder for reproducing settings; each channel of the coaxial zoned illumination is driven by an independent constant current, and the pulse width and duty cycle are adjustable to match the exposure time.

[0027] The aforementioned device maintains consistency between the illumination and imaging optical paths under a coaxiality constraint of no more than 0.2 mm, reducing shadows and ghosting introduced by parallax. It is suitable for secondary engraving inspection of painted surfaces, coatings, and metal substrates with different roughnesses. The polarization adjustment mechanism adapts to different materials and surface film conditions, and has good visibility capabilities for low-contrast scratches caused by fine, shallow, localized abrasion, or secondary processing.

[0028] Please see Figure 1-3 In one possible implementation, the fixing unit 1 adopts a triangular base 10, with support foot mounting positions at the three corners of the base 10, and each mounting position is equipped with a support foot assembly 11. The support foot assembly 11 is connected to the base 10 via a quick-release connection, either by snap-fit ​​or twist-lock. The three-point support directly defines the reference plane of the equipment, avoiding warping caused by excessive constraints at multiple points, and enabling the device to be quickly and stably placed even on uneven work areas.

[0029] During use, the triangular base 10 is first positioned at the work station, and then the support foot assembly 11 is quickly engaged with the mounting position: for example, in the snap-fit ​​structure, the support foot pin is inserted axially along the mounting hole, and after the built-in spring is compressed, the snap ring expands outward at the annular groove to form a radial lock; in the twist-lock structure, the support foot latch engages with the L-shaped or arc-shaped groove on the base 10, and after insertion, it is rotated about 1 / 4 to 1 / 2 turn, relying on the inclined surface or cam to generate axial clamping force, and is prevented from loosening by the anti-loosening component.

[0030] The base 10 is preferably an equilateral triangle with a side length of, for example, 280–420 mm and a thickness of 12–20 mm. The material can be aluminum alloy or steel. To balance weight and rigidity, weight-reducing ribs are machined on the bottom surface, and cable routing channels are pre-installed. The upper surface is arranged with T-slots or an array of threaded holes for mounting the attitude adjustment unit 2 and accessories. This structure allows for quick leveling and locking during deployment, reducing tool dependence and the risk of misinstallation. It also maintains overall rigidity and a stable coaxial relationship under vibration conditions, which is beneficial for continuously maintaining the consistency between the illumination and imaging optical axes and obtaining reproducible imaging conditions across multiple batches of testing.

[0031] Please see Figure 1-3 In one possible implementation, the support foot assembly 11 includes a support foot body 12 and a support foot end piece 13 installed at the lower end of the support foot body 12. The support foot end piece 13 is any one of a magnetic end piece, a vacuum adsorption end piece, or an anti-slip rubber end piece.

[0032] When using these devices, select the appropriate end fitting based on the material and surface condition of the workstation: When the workstation is a ferromagnetic platform or steel fixture, the magnetic end fitting uses a permanent magnet to generate a normal clamping force. A thin elastic isolation pad is preferably placed on the bottom surface to even out minor undulations and protect the workstation surface. When the workstation is made of glass, aluminum profiles, or a coated layer and requires no magnetic attraction, the vacuum adsorption end fitting uses a flexible cup lip connected to a negative pressure source to establish adsorption. A built-in one-way valve maintains stable adsorption during short-term air interruption. When the workstation has pores, a rough paint surface, or high surface protection requirements, the anti-slip rubber end fitting utilizes a high coefficient of friction and material compliance to provide tangential anti-slip and compliant support. When the three types of end fittings are interchanged on the same quick-change interface, the end face reference and axis position remain consistent. Under conditions of 0.5–2 mm axial compression and near-cross-polarization imaging caused by pressing the elastic light-shielding ring 8, the increase in mirror component and analysis angle deviation caused by slight tilting or slippage of the base 10 are avoided, ensuring stable reproduction of light suppression and micro-morphology.

[0033] Please see Figure 1-3In one possible implementation, the attitude adjustment unit 2 is composed of an X-axis linear slide 14 and a Y-axis linear slide 15 stacked together. The Y-axis slide is mounted on the X-axis slide, and both are equipped with locking components for locking the position. The two slides are guided by cross roller guides or precision linear guides, and achieve micro-displacement with the help of a differential head or fine-tooth screw; mechanical limiters and travel scales / reading scales are set at the ends. During assembly, the parallelism between the X-axis guide rail and the workpiece reference edge is first corrected using the base 10 reference plane, and then the Y-axis slide and the X-axis slide are orthogonally positioned by "two pins and one hole". The orthogonality error is controlled within ≤0.05° to ensure the geometric accuracy of the planar motion and the coaxial imaging relationship.

[0034] Specifically, during use, the coarse positioning of the engraving area is first achieved through X and Y translation, followed by fine adjustment using a micrometer head to ensure the imaging optical axis passes through the geometric center of the target area. The locking mechanism employs a side-pressure or wedge-type force-enhancing structure to pre-tighten the slider and guide rail. Positional drift after locking is controlled to ≤5 μm, preventing field-of-view shift and changes in polarization analysis angle caused by unlocking / relocking. To reduce Abbe error, the reading scale is positioned near the imaging optical axis; the lead screw is equipped with a backlash compensation nut or double nuts for pre-tightening to improve bidirectional repeatability. An array of threaded holes is pre-drilled on the upper surface of the slide to facilitate connection with the Z-axis lifting mechanism 16 and the two-DOF gimbal, while ensuring that the coaxial positioning reference of the camera and illumination is not obstructed.

[0035] The aforementioned structure enables rapid, repeatable in-plane positioning and reliable locking, maintaining the consistency between the illumination and imaging optical axes, and improving image stability and repeatability under near-cross polarization conditions. Depending on cycle time and accuracy requirements, the drive method can be selected from manual differential head, fine-tooth lead screw + handwheel, electric stepper, or servo motor.

[0036] Please see Figure 1-3 In one possible implementation, the attitude adjustment unit 2 is equipped with a Z-axis lifting mechanism 16, which is mounted on the Y-axis linear slide 15. The Z-axis lifting mechanism 16 adopts a precision dovetail / cross roller guide vertical structure with a stroke of 10–80 mm. The outer side is etched with millimeter-gradient dual scales and a zero reference line for rapid reset and recipe recording. Micro-adjustment is achieved by a micrometer head, with a typical reading of 1–2 μm per division. The handle end is equipped with anti-slip knurling and a scale cover to avoid accidental contact. To ensure geometric consistency with the coaxial imaging unit 3, a through hole or semi-through groove is opened in the center of the lifting platform to allow space for the coaxial sleeve and wiring. The perpendicularity of the guide rail to the reference plane of the base 10 remains stable within a unit stroke. The locking element is located in a symmetrical position to reduce pitch deviation induced by locking.

[0037] Specifically, during use, after completing the X and Y coarse positioning, the Z-axis locking is released. First, the imaging acquisition unit 4 and lens group are smoothly moved closer to the preset working distance along the Z-axis using the micrometer head. Then, the sharpness and scratch contrast are observed on the real-time image, and fine-tuned to the optimal focal plane in 1-2 increments. Subsequently, the Z-axis locking is activated to pre-tighten the platform and guide rail. The scale indicator is used to record the standard focal length point corresponding to the inspected vehicle model and position, facilitating subsequent reset. To reduce Abbe error, the micrometer head and scale reference line are positioned close to the imaging optical axis. Backlash during the lifting process is eliminated by the pre-tightening nut. After locking, the positional drift remains within process requirements, ensuring that light suppression and edge detail rendering under near-cross polarization conditions are unaffected by defocusing and attitude changes.

[0038] Please see Figure 1-3 In one possible implementation, a two-degree-of-freedom gimbal is installed at the end of the attitude adjustment unit 2, located at the output end of the Z-axis lifting mechanism 16. The pitch and yaw axes of the gimbal are orthogonal to each other and pass through the imaging optical axis at their spatial intersection. The adjustable range of both pitch and yaw is ±10°, and each axis is equipped with an independent angle locking device. Preferably, crossed roller bearings or thin tapered roller bearings are used to support the rotating shaft. The outer ring of the turntable is equipped with a scale ring and a zero mark, with a minimum reading of, for example, 0.5°. Small-angle smooth adjustment is achieved in conjunction with a fine-tuning screw or a fine-tooth sector-worm gear pair. The locking device adopts a symmetrically arranged wedge or eccentric clamp structure. After locking, the angular position is kept stable by elastic pre-tightening, avoiding slight sway caused by unilateral clamping.

[0039] During use, after completing X and Y translation and Z-axis focusing, fine-tune the pitch and yaw of the gimbal to align the imaging optical axis as closely as possible with the normal of the surface under inspection. Observe the sharpness and contrast changes of the scratch strokes in the real-time image, and search back and forth along a single axis at small angles to reach the optimal point. When under near-cross polarization conditions and with varnish or oil film present, small pitch adjustments of 0.2° to 0.5° can be used to change the off-axis direction of the specular reflection, thereby further suppressing glare and enhancing the micro-topography scattering signal. After adjustment, first lock the pitch axis and then the yaw axis, confirming that there is no significant image drift after locking the two axes. Since the intersection of the two axes coincides with the imaging optical axis, the center of the field of view remains consistent before and after locking. The compression of the elastic light-shielding ring 8 is uniform in the fitted state, the Z-axis working distance is not perceptibly affected, and the coaxiality of the coaxial illumination and the camera also remains stable.

[0040] It is worth noting that the gimbal can adopt a double-layer universal frame structure or an integrated flexible hinge structure to reduce thickness and dead zone. The fine adjustment mechanism can be replaced with an opposing micrometer head to obtain finer angular resolution (e.g., on the order of 0.1°). The scale ring can be used in conjunction with a small electronic tilt sensor to record the angle reading to the control unit 9 as a recipe parameter.

[0041] In one possible implementation, the coaxial zone-controlled illumination 5 adopts a ring-shaped four-quadrant structure. The four quadrants are equally angularly divided along the circumference and each is controlled by an independent drive channel. Each quadrant consists of several narrow-angle LED arrays and a one-piece molded diffuser. The arrays are mounted on a ring base with an inner diameter of, for example, 20–50 mm and an outer diameter of, for example, 40–90 mm, to ensure that the light cone covers the lens field of view without obstructing the imaging channel. The emitting surfaces of the four quadrants are located in the same normal plane. An integral heat sink and temperature sensing element are provided on the back of the base for constant current drive and temperature drift compensation. The illumination assembly and the imaging acquisition unit 4 are fixedly installed by a positioning structure consisting of a coaxial sleeve, a thrust end face, and a radial positioning pin: the coaxial sleeve and the outer diameter of the lens are fitted with a transition fit, the thrust end face provides an axial reference, and the radial positioning pin and the pin hole are fitted with a small clearance fit to limit the circumferential and radial positions, so that the coaxiality between the illumination optical axis and the imaging optical axis is no more than 0.2 mm.

[0042] Specifically, during assembly, the coaxial sleeve is first pressed against the thrust end face of the lens shoulder to ensure axial positioning. Then, the first locating pin is inserted into the reference hole, and the lens is gently rotated until aligned with the second locating hole, where the locating pin is inserted to achieve dual circumferential and radial positioning. Finally, the annular base is symmetrically locked with equally distributed circumferential fastening screws to ensure uniform contact of the thrust end face and prevent assembly misalignment. Each quadrant drive channel is independently connected to the control unit 9, allowing for individual switching or setting of different duty cycles / currents to alter the incident orientation and intensity distribution, thereby generating an orientation-sensitive reflection response to anisotropic microgrooves. During polarization detection, the illumination light is first linearly polarized by the first polarizer 6 and coaxially incident on the surface under test. By selectively illuminating a specific quadrant or sequentially illuminating the four quadrants, the incident orientation can be changed while maintaining coaxial geometry. Combined with the analyzer angle setting of the coaxial imaging channel, this enhances the visibility of fine lines and residual deformation bands. To suppress stray light, the inner edge of the ring and the surface of the illumination cavity are treated with matte black, and a thin light-shielding blade is added at the edge of the field of view to limit off-axis light leakage.

[0043] Please see Figure 1-4 In one possible implementation, the control unit 9 includes a timing trigger control box, which is equipped with a camera trigger interface and a flash synchronization interface. The interface standard is TTL level, and the trigger edge is a rising edge. The minimum response time from the external trigger signal to the valid output is no more than 5 ms, and the trigger jitter is no more than ±50 μs. Preferably, the camera trigger and flash synchronization are configured with independent channels in the control box. Both channels adopt opto-isolation and Schmitt trigger shaping. The external connection can be selected with BNC or M12 interface and provide polarity indication for easy field wiring.

[0044] In operation, external devices (such as PLCs, foot switches, or host computer I / O) output TTL rising edges to the control box trigger input. The signal is then optocoupled and Schmitt trigger shaped before entering the timing logic. The timing logic first outputs a camera trigger pulse after a settable pre-delay, and simultaneously, or according to a set bias, outputs a flash synchronization pulse to the illumination driver. When four-quadrant illumination requires sequential lighting, the control box sequentially sends quadrant enable signals within the same trigger cycle or across multiple cycles according to a preset formula, aligning with the camera exposure window. When single-shot uniform coaxial illumination is required, the control box outputs synchronization pulses to all four channels simultaneously. To ensure jitter performance, critical channels use hardware timing (such as FPGA timing units or high-precision timers) to generate pulse width and delay. The inputs are equipped with selectable debounce and minimum interval latching to prevent repeated triggering due to glitches. The outputs support both active push-pull and open-collector drives to adapt to different camera brands and flash drivers. To reduce system latency uncertainty, the control box provides fixed bias compensation for cable length differences, separates power and signal ground wiring, and adds ESD protection and surge suppression at the interface side. The BUSY signal remains active during the exposure period. If another trigger is given from the outside, the higher-level logic will queue or block it until the current exposure is completed, ensuring that one trigger corresponds to one exposure and one illumination.

[0045] Please see Figure 1-4 In one possible implementation, the coaxial imaging unit 3 is equipped with a drawer-type filter holder, which is inserted and removed along a direction orthogonal to the imaging optical axis. The holder features low-friction linear grooves on both sides, and a limiting surface and locking mechanism at the front end, automatically locking in place by the elastic locking mechanism. The holder cavity is equipped with a three-thickness adaptation structure, capable of accommodating filters of 1mm, 2mm, and 3mm thicknesses respectively. Thickness adaptive clamping is achieved through replaceable stepped pads or spring-loaded clamping frames. To limit the insertion direction and prevent reverse or misaligned insertion, the holder features asymmetrical guide protrusions and corresponding grooves, with a notch on one side of the filter frame. Full insertion is only possible when the notch aligns with the protrusion. A stop shoulder is also provided at the end of the holder to prevent over-insertion into the imaging channel. The inner wall of the holder and the edge of the opening are treated with a matte black finish, and a soft pressure ring is provided around the filter to reduce light leakage through gaps.

[0046] During use, the operator presses the front unlocking mechanism, pulls the bracket laterally to the mechanical stop, inserts the selected filter, aligns the directional notch of the filter frame with the guide key of the bracket, and gently pushes the bracket until the thrust surface is in contact and a locking click is heard to complete the assembly. To change filters of different thicknesses, simply switch the corresponding stepped shim or adjust the spring clip position; there is no need to change the optical-mechanical coaxial relationship of the imaging module. Depending on the illumination wavelength and the reflection characteristics of the inspected surface, bandpass, narrowband, or neutral density filters can be selected: when using narrowband LED illumination, a bandpass filter matching the center wavelength is used to suppress ambient light; on highly reflective substrates, an ND filter of appropriate density can be added to avoid exposure saturation. The insertion / removal direction is orthogonal to the imaging optical axis, ensuring that filter replacement does not affect the axial position and focal length of the objective lens and camera. After locking, the bracket is positioned by both the thrust surface and the guide surface, preventing image quality fluctuations caused by tilting or eccentricity.

[0047] Please see Figure 1-4 In one possible implementation, a light-shielding tube is installed at the front end of the coaxial imaging unit 3, and an annular elastic light-shielding ring 8 is provided at the light-emitting end of the light-shielding tube. The inner wall of the light-shielding tube is treated with matte black and has a threaded or snap-fit ​​interface for coaxial fixation with the lens mount; the light-shielding ring is made of silicone, with a hollow or flat circular lip structure in cross-section, and a preferred hardness of Shore A 30-50. The inner ring engages with the light-shielding tube through a circumferential groove, achieving tool-free assembly, disassembly, and positioning. When the light-shielding ring is in operation, it fits against the surface being inspected, and the axial compression is controlled within 0.5-2 mm; to prevent reverse installation and misalignment, the light-emitting end of the light-shielding tube is provided with asymmetrical keyways and guide bevels, and the two ends of the groove are provided with stop shoulders to limit the insertion depth and ensure uniform circumferential force. To balance fit and dirt resistance, the surface of the light-shielding ring is micro-textured (such as concentric fine ribs or fine sandblasting), and the lip edge is chamfered by 0.2-0.5 mm to reduce initial friction; a thin-walled reinforcing ring is built into the ring body to suppress edge flipping under large compression. A labyrinth-style pressure relief groove is set on the inner side of the light-shielding cylinder opening to achieve a slight pressure difference balance without forming a direct light path, thus avoiding suction and pulling during extraction.

[0048] Specifically, the light-shielding tube is aligned with the area under inspection along the imaging optical axis and gently pressed until the light-shielding ring experiences axial compression of 0.5–2 mm. The rounded lip conforms to the slight undulations of the workpiece, thereby sealing the periphery of the imaging window and suppressing the entry of ambient stray light. The compression rebound force is within a controllable range and does not significantly change the Z-axis working distance or focal plane. After bonding, the specular component from the varnish / metal surface under near-cross polarization conditions is suppressed by the analyzer, and the remaining scattering signal caused by micro-morphology is preserved in the local dark field, enhancing the contrast of the scratch edges and shallow fine strokes. The friction and conformability of the light-shielding ring simultaneously suppress the slight relative slippage caused by micro-vibrations, ensuring stable alignment between the coaxial illumination beam and the field of view. Replacement is simple: pull out the old ring along the slot direction and press in the new ring until a noticeable stop is felt, without affecting the coaxial positioning structure and optical calibration.

[0049] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0050] Although embodiments of the present invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the claims and their equivalents.

[0051] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0052] Although embodiments of the present invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A VIN secondary marking polarization detection device, characterized in that, include: Fixed unit; The pose adjustment unit provides mutually orthogonal first and second translational degrees of freedom, vertical and horizontal degrees of freedom along the imaging optical axis, and lockable angle fine adjustment; The coaxial imaging unit includes an imaging acquisition unit, a coaxial partitioned controllable illumination, a first polarizer disposed in the illumination optical path, a second polarizer disposed in the imaging optical path, and an elastic light-shielding ring located at the light-emitting end that can be attached to the surface under inspection. The control unit is electrically connected to the imaging acquisition unit and the coaxial partition controllable illumination to achieve synchronous triggering of illumination and imaging; The coaxial zone controllable illumination and the imaging acquisition device are fixedly installed through a coaxial positioning structure, so that the coaxiality between the illumination optical axis and the imaging optical axis is no more than 0.2 mm; the first polarizer and the second polarizer are installed on the angle adjustment seat, and the relative angle between their polarization axes is adjustable; the axial compression of the elastic light shielding ring in the fitted state is 0.5–2 mm.

2. The apparatus according to claim 1, characterized in that, The fixing unit is a triangular base, and support foot mounting positions are respectively set at the three corners of the base. Each support foot mounting position is equipped with a support foot assembly. The support foot assembly is connected to the base through a quick-connect connection, which can be either a snap-on type or a rotary lock type.

3. The apparatus according to claim 2, characterized in that, The support foot assembly includes a support foot body and a support foot end piece installed at the lower end of the support foot body. The support foot end piece is any one of a magnetic end piece, a vacuum adsorption end piece, or an anti-slip rubber end piece.

4. The apparatus according to claim 1, characterized in that, The posture adjustment unit includes an X-axis linear slide and a Y-axis linear slide. The Y-axis linear slide is mounted on the X-axis linear slide to form a stacked arrangement. The X-axis linear slide and the Y-axis linear slide are respectively provided with locking members for locking the position.

5. The apparatus according to claim 4, characterized in that, The posture adjustment unit also includes a Z-axis lifting mechanism, which is installed on the Y-axis linear slide, has a scale indicator, and is finely adjusted by a micrometer head. The Z-axis travel is 10–80 mm.

6. The apparatus according to claim 5, characterized in that, The attitude adjustment unit is equipped with a two-degree-of-freedom gimbal at its end. The gimbal is installed at the output end of the Z-axis lifting mechanism and can realize the angle adjustment in the pitch and yaw directions, with an adjustment range of ±10°. Angle locking components are provided in the pitch and yaw directions respectively.

7. The apparatus according to claim 1, characterized in that, The coaxial zone controllable illumination is a ring-shaped four-quadrant structure, with each of the four quadrants controlled by an independent drive channel. The coaxial zone controllable illumination and the imaging acquisition unit are fixedly installed through a positioning structure consisting of a coaxial sleeve, a thrust end face, and a radial positioning pin, so that the coaxiality between the illumination optical axis and the imaging optical axis is no more than 0.2 mm.

8. The apparatus according to claim 7, characterized in that, The control unit includes a timing trigger control box, which is equipped with a camera trigger interface and a flash synchronization interface. The interface is TTL level, the trigger edge is a rising edge, the minimum system response time is no more than 5 ms, and the trigger jitter is no more than ±50 μs.

9. The apparatus according to claim 1, characterized in that, The coaxial imaging unit includes a drawer-type filter holder, which can be inserted and removed along a direction orthogonal to the imaging optical axis. It can accommodate filters of any size with a thickness of 1 mm, 2 mm, or 3 mm, and is equipped with a stop and positioning structure to limit the insertion direction and prevent reverse or misaligned installation.

10. The apparatus according to claim 9, characterized in that, The coaxial imaging unit has a light-shielding tube at its front end, and an annular elastic light-shielding ring is installed at the light-emitting end of the light-shielding tube. The elastic light-shielding ring is made of silicone and has an axial compression of 0.5–2 mm when it is attached to the surface being inspected. The elastic light-shielding ring can be replaced and installed through a slot structure.

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