Precise image measurement equipment and method based on laser measurement

Abstract

The invention discloses precise image measurement equipment and method based on laser measurement, and relates to the field of laser measurement, and the measurement equipment comprises a multi-axis motion platform, a measurement probe and a control system. The measuring probe is of a probe-shaped structure capable of penetrating into a measured inner cavity and is installed at the tail end of the Z axis of the multi-axis motion platform, and a confocal laser sensor and a lateral microscopic vision system are integrated in the measuring probe. The lateral microscopic vision system comprises a miniature image sensor, a miniature lens module and a lateral projection light source, and the optical axis of the lateral microscopic vision system is turned back through a reflection optical element, so that the effective sight direction of the lateral microscopic vision system is perpendicular to the axis direction of the measuring probe. According to the invention, through the design of the integrated miniature measuring probe, the shielding and depth-of-field limitation are overcome, and the synchronous and high-precision data acquisition of the inner side wall and the bottom of the deep hole with a high depth-diameter ratio and a step structure is realized, so that the complete three-dimensional shape of the inner cavity is reconstructed, the contour features are completely captured, and the precise measurement requirement is realized.

Description

Technical Field

[0001] This invention relates to the field of laser measurement technology, and more particularly to optical metrology equipment, specifically a precision image measurement device and method based on laser measurement. Background Technology

[0002] In precision manufacturing fields, such as aerospace, automotive engines, and precision molds, there are numerous core components with high aspect ratio internal cavity structures. Examples include micro-orifices in engine fuel injectors, blind lubrication holes in gears, and cooling channels in molds. The geometrical precision of these internal structures, including inner diameter, roundness, depth, taper, and step height, is a key factor determining the final performance, service life, and operational reliability of the product. For instance, the diameter and roundness of the fuel injector orifice directly affect fuel atomization and combustion efficiency; the size and smoothness of the cooling channels determine heat dissipation efficiency and service life. Therefore, precise three-dimensional dimensional inspection and quality control of these typically invisible or semi-invisible high aspect ratio internal cavity structures is an indispensable and crucial step in modern high-end manufacturing.

[0003] To meet the precision measurement requirements of high aspect ratio cavities, existing technologies mainly employ a composite measurement method combining optical imaging and laser measurement. This involves integrating a laser scanning or point laser ranging module into a top-view optical system. A laser point or line is projected into the aperture, and the three-dimensional coordinates of a specific point are obtained by measuring the time or phase difference of the reflected light, attempting to compensate for the insufficient accuracy of pure vision methods in the depth (Z-axis) direction.

[0004] However, when faced with micropore structures with internal steps and a depth-to-diameter ratio exceeding 5:1, the laser beams of the aforementioned existing technologies typically rely on a direct path on the outside. Inside the deep hole, they are easily blocked by structures such as the hole walls, making it difficult to effectively irradiate the vertical sidewall surface or the bottom area to be measured. This results in a significant loss of laser data on the target surface. At the same time, the high-magnification lenses used in the vision section usually have a very shallow depth of field to ensure imaging resolution, making it impossible to simultaneously place the edge of the hole, the middle section of the hole wall, and the bottom plane of the hole on the focal plane. This results in only obtaining locally clear images in a single shot. More importantly, under the traditional top-view perspective, the edge of the hole will severely obstruct the internal field of view, especially in complex structures with steps. Even if multi-focal-plane images are acquired by moving along the Z-axis, it is difficult to fully capture the contour features of the internal sidewalls, thus failing to achieve truly high-precision three-dimensional measurement. This leads to fragmented data, unbalanced accuracy, and difficulty in reconstructing a complete and accurate three-dimensional morphology of the internal cavity.

[0005] Therefore, it is necessary to improve upon the shortcomings of existing technologies in order to solve the above problems. Summary of the Invention

[0006] This invention overcomes the shortcomings of the prior art and provides a precision image measurement device and method based on laser measurement. Through the design of an integrated micro measurement probe, it overcomes the limitations of occlusion and depth of field, and achieves synchronous and high-precision data acquisition of the internal sidewalls and bottom of deep holes with high aspect ratio and stepped structure. This allows for the reconstruction of the complete three-dimensional morphology of the internal cavity, complete capture of contour features, and fulfillment of precision measurement requirements.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: First aspect: The present invention provides a precision image measurement device based on laser measurement, comprising: a multi-axis motion platform, a measurement probe, and a control system;

[0008] The multi-axis motion platform is used to carry and drive the measuring probe to move along the X, Y and Z axes within the workspace;

[0009] The measuring probe is a probe-like structure that can penetrate deep into the cavity being measured. It is installed at the Z-axis end of the multi-axis motion platform and integrates the following internal components:

[0010] A confocal laser sensor is disposed inside and at the lower end of the measuring probe, and is used to emit and receive laser light downward along the main axis of the measuring probe.

[0011] A lateral microscopic vision system is installed inside and at the lower end of the measuring probe to acquire images of the inner cavity sidewall;

[0012] The lateral microscopic vision system includes a miniature image sensor, a miniature lens module, and a lateral light source. Its optical axis is refracted by a reflective optical element so that its effective line of sight is perpendicular to the axial direction of the measurement probe.

[0013] The control system is electrically connected to the multi-axis motion platform, the confocal laser sensor, and the lateral microscopic vision system. It is used to control the three-axis motion, synchronously trigger laser measurement and image acquisition, and perform internal cavity three-dimensional morphology reconstruction and size measurement by data fusion processing.

[0014] In a preferred embodiment of the present invention, the miniature image sensor is installed inside the housing of the measuring probe, and the miniature lens module and the side-projection light source are both installed in the integrated cavity at the lower end of the measuring probe; the reflective optical element is a 45° miniature right-angle reflecting prism or reflector, which is fixed at the bottom of the measuring probe and located in front of the line of sight of the miniature lens module.

[0015] In a preferred embodiment of the present invention, the confocal laser sensor includes: a laser source installed in the top housing of the measuring probe, and a focusing lens group installed in the integrated cavity at the lower end of the measuring probe; the output end of the laser source is connected to the focusing lens group via an optical fiber.

[0016] In a preferred embodiment of the present invention, the focusing lens group is coaxially arranged with the measuring probe, and the laser source is a broadband or multi-wavelength semiconductor laser.

[0017] In a preferred embodiment of the present invention, the control system includes: an industrial computer, a motion control card, an image acquisition card, a laser controller, and a host computer;

[0018] The industrial computer uses a multi-core processor to run a real-time operating system;

[0019] The motion control card communicates with the multi-axis motion platform to perform synchronous control and trajectory planning of X, Y and Z axis motion.

[0020] The image acquisition card is used to receive image data from the miniature image sensor;

[0021] The laser controller is used to configure parameters, acquire signals and process data for the confocal laser sensor, and exchange data with the industrial computer.

[0022] The host computer is based on a modular architecture and includes a motion control module, an image acquisition module, a laser data processing module, a data fusion module, a 3D reconstruction module, a size analysis module, and a human-computer interaction interface module.

[0023] In a preferred embodiment of the present invention, the multi-axis motion platform includes: an X-axis motion mechanism, a Y-axis motion mechanism installed at the X-axis end of the X-axis motion mechanism, and a Z-axis motion mechanism installed at the Y-axis end of the Y-axis motion mechanism;

[0024] The X-axis motion mechanism, Y-axis motion mechanism, and Z-axis motion mechanism each include: a mounting block, a translation block disposed on one side of the mounting block, and a plurality of cross roller guides installed between the mounting block and the translation block; a translation groove is provided on one side of the mounting block, a connecting block is fixed on one side of the translation block, and one side of the housing of the measuring probe is installed on one side of the translation block;

[0025] The side of the connecting block is slidably connected to the inner side of the translation groove. The inner side of the translation groove is rotatably connected to a lead screw via a bearing. The inner side of the connecting block is threadedly connected to the side of the lead screw. A servo motor is fixed at the bottom of the mounting block. The output end of the servo motor is fixed to one end of the lead screw via a coupling.

[0026] Secondly, this invention provides a measurement method for a precision image measurement device based on laser measurement, comprising the following steps:

[0027] S1. The control system controls the multi-axis motion platform to move the measuring probe above the opening of the inner cavity to be measured and then lowers it vertically to make it penetrate into the inner cavity.

[0028] S2. The Z-axis of the multi-axis motion platform is fixed at different heights, and the X and Y axes of the multi-axis motion platform are driven on each height plane to drive the measuring probe to perform planar scanning along a predetermined scanning path. During the scanning process, the confocal laser sensor is synchronously triggered to continuously measure the absolute distance value from the current point at the bottom of the inner cavity, and the lateral microscopic vision system continuously acquires images of the inner cavity sidewall facing it.

[0029] S3. The control system processes the images acquired by the lateral microscopic vision system to extract the two-dimensional contour coordinates of the inner cavity sidewalls, and combines the calibration parameters of the lateral microscopic vision system with the current Z-axis height value to convert the two-dimensional contour coordinates into three-dimensional point cloud data of the sidewalls; at the same time, based on the distance value measured by the confocal laser sensor and the current Z-axis height value, the three-dimensional point cloud data of the bottom of the inner cavity is calculated, and the three-dimensional point cloud data of the sidewalls and the three-dimensional point cloud data of the bottom are fused in a unified coordinate system to reconstruct the complete three-dimensional model of the inner cavity;

[0030] S4. Based on the reconstructed complete three-dimensional model, calculate the geometric dimensions of the cavity.

[0031] In a preferred embodiment of the present invention, in step S2, the predetermined scanning path is one of a spiral, a serpentine line, or a concentric circle trajectory.

[0032] In a preferred embodiment of the present invention, in step S3, the two-dimensional contour coordinates of the inner cavity sidewall are extracted by edge detection and sub-pixel localization algorithm; the fused point cloud data is processed by a three-dimensional modeling algorithm to generate the three-dimensional model, wherein the three-dimensional modeling algorithm is one of Poisson reconstruction algorithm, traveling cube algorithm or triangulation algorithm.

[0033] In a preferred embodiment of the present invention, in step S4, the geometric dimensions include one or more of the following: inner diameter, roundness, depth, taper, and internal step height.

[0034] This invention addresses the shortcomings of the prior art and has the following beneficial effects:

[0035] (1) This invention provides a precision image measurement device and method based on laser measurement. A confocal laser sensor and a lateral microscopic vision system are integrated in the measurement probe. The probe-shaped measurement structure is realized through miniaturization and spatial design. The confocal laser sensor can accurately measure the absolute distance to the bottom of the hole. The lateral microscopic vision system can simultaneously acquire side wall images and obtain dense two-dimensional contour information. The bottom depth data and side wall contour data can be acquired at the same time in one scan. There is no need to change the sensor or measure in multiple times. It can realize unobstructed data acquisition of the inner wall and bottom features of the high depth-to-diameter ratio cavity, thereby completely capturing the contour features and realizing the precision measurement requirements.

[0036] (2) In this invention, by installing the lateral microscopic vision system at the lower end of the measuring probe and with the cooperation of the reflecting prism, the optical axis is made to form a 90° angle with the probe axis, which can change the optical path direction of the traditional top-view measurement. When the measuring probe is inserted into the cavity of the high aspect ratio micro-hole, the line of sight is folded to the side, which can avoid the obstruction of the edge of the hole and directly face the side wall of the cavity. Thus, even in the deep hole with high aspect ratio and internal steps, the side wall contour information can be clearly and completely captured, which can effectively solve the problem of visual blind spot in the cavity with high aspect ratio, significantly improve the observability and data integrity of the side wall features, and thus provide a continuous and complete side wall morphology data basis for subsequent three-dimensional size analysis, and reconstruct the complete three-dimensional morphology of the cavity.

[0037] (3) In this invention, the multi-axis motion platform is controlled to perform a predetermined path scan at different Z-axis heights, and the absolute height coordinates of the bottom of the cavity are calculated in real time by combining the laser ranging value. Its layered scanning can cover the depth range of the entire cavity, ensuring that the cross-sectional data of each layer from the opening to the bottom of the hole are collected. It can achieve full range data coverage in the depth direction of the cavity, effectively avoid local omissions, and thus provide accurate layered height benchmarks for three-dimensional reconstruction.

[0038] (4) In this invention, by fusing the depth information obtained by laser measurement with the sidewall contour information extracted by the vision system, the metrological accuracy of laser in the Z direction and the imaging detail advantage of vision in the XY plane can be fully utilized. Under a unified world coordinate system, the sparse laser point cloud and the dense visual point cloud are spliced ​​and fused together, and a complete three-dimensional model is generated by the three-dimensional reconstruction algorithm. In this way, a complete and accurate three-dimensional shape of the inner cavity can be reconstructed, which can more accurately calculate key dimensions such as inner diameter, roundness, and step height, thereby satisfying the data integrity of high depth-to-diameter ratio inner cavity precision measurement and effectively improving the overall accuracy of measurement. Attached Figure Description

[0039] 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 without creative effort.

[0040] Figure 1 This is a three-dimensional structural diagram of the measuring device according to a preferred embodiment of the present invention;

[0041] Figure 2 This is a frontal half-sectional view of the measuring probe according to a preferred embodiment of the present invention;

[0042] Figure 3 This is a partial structural diagram of the measuring probe located in the integrated cavity according to a preferred embodiment of the present invention;

[0043] Figure 4 This is a front view of the separation structure of the translation block and the mounting block according to a preferred embodiment of the present invention;

[0044] Figure 5 This is a rear view of the separation structure of the translation block and the mounting block according to a preferred embodiment of the present invention;

[0045] In the diagram: 1. Multi-axis motion platform; 11. Mounting block; 12. Translation block; 13. Cross roller guide; 14. Translation groove; 15. Connecting block; 16. Lead screw; 17. Servo motor; 2. Measuring probe; 21. Housing; 22. Integrated cavity; 3. Miniature image sensor; 31. Miniature lens module; 32. Side-projection light source; 33. Reflective optical element; 4. Laser light source; 41. Focusing lens group. Detailed Implementation

[0046] 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 embodiments of the present invention, and not all embodiments. 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.

[0047] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0048] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art will understand the specific meaning of the above terms in this application based on the specific circumstances.

[0049] Example 1: As Figure 1 As shown, a precision image measurement device based on laser measurement includes: a multi-axis motion platform 1, a measurement probe 2, and a control system.

[0050] In some specific implementations, the measuring probe 2 is a probe-like structure that can penetrate deep into the cavity being measured. It is installed at the Z-axis end of the multi-axis motion platform 1 and integrates a confocal laser sensor and a lateral microscopic vision system.

[0051] It should be noted that the measuring probe 2 has a cylindrical or conical structure, with an outer diameter preferably of 10-30 mm and a length preferably of 100-200 mm, to adapt to the measurement needs of cavities of different sizes and depths. The outer material of the measuring probe 2 is preferably a medical-grade titanium alloy or zirconia ceramic material that is wear-resistant, has low reflectivity, and has good mechanical stability. Among them, titanium alloy has high strength, lightweight and excellent biocompatibility, and is easy to precision machine. Zirconia ceramic has extremely high hardness, wear resistance, corrosion resistance and thermal stability, and its low reflectivity helps to reduce stray light interference to the internal optical system.

[0052] Furthermore, the upper housing 21 is connected to the Z-axis end of the multi-axis motion platform 1 via a standard mechanical interface, such as a high-precision flange or a tapered shank connector, while the lower integrated cavity 22 is used to house the core components of the confocal laser sensor and the lateral microscopic vision system.

[0053] Specifically, the lower end of the measuring probe 2 uses its slender probe-like structure to penetrate deep into the inner cavity of the workpiece, delivering the core components of the confocal laser sensor and the lateral microscopic vision system to the area to be measured. This avoids the problem of orifice obstruction in traditional top-view measurement and enables accessibility to complex inner cavity structures with high depth-to-diameter ratios and steps.

[0054] like Figure 2 and Figure 3As shown, in some specific embodiments, a confocal laser sensor is disposed inside and at the lower end of the measuring probe 2, and is used to emit and receive laser light downward along the main axis of the measuring probe 2; the confocal laser sensor includes: a laser source 4 installed in the top housing 21 of the measuring probe 2, and a focusing lens group 41 installed in the integrated cavity 22 at the lower end of the measuring probe 2; the output end of the laser source 4 is connected to the focusing lens group 41 through an optical fiber.

[0055] It should be noted that the focusing lens group 41 is coaxially set with the measuring probe 2. The laser source 4 is a broadband or multi-wavelength semiconductor laser, preferably HL6501MG, with a wavelength of 400-700 nm and an output power of 5 mW. The focusing lens group 41 consists of two aspherical lenses made of H-K9L material, with a focal length of 2 mm and a numerical aperture of 0.5. It is coaxially fixed with the housing 21 by a precision metal bracket to ensure that the laser is emitted vertically downward along the main axis (Z-axis) of the measuring probe 2, and the spot diameter is focused to 5 μm to meet the submicron ranging accuracy requirements.

[0056] Specifically, the laser source 4 emits a laser beam through an optical fiber to the focusing lens group 41, forming a measurement beam with axial dispersion characteristics. When this beam is projected onto the surface to be measured, the confocal principle ensures that the reflected light can be efficiently received and generate a peak signal only when the surface to be measured is located at the focal plane of the lens. This peak signal is then detected by a spectrometer or photodetector array. The spectrometer can accurately analyze the center wavelength of the reflected beam. Since different wavelengths correspond to different axial focal positions, the confocal laser sensor can determine the Z-axis coordinate of the measured point in real time with sub-micron accuracy by detecting the peak wavelength of the reflected light. The laser sensor has a measurement frequency of 5000-10000 Hz to support high-speed scanning measurement, ensuring that high-density point cloud data can still be acquired under fast-moving platforms. This provides metrological-level high-precision Z-axis distance information, and the measurement is almost unaffected by the surface color, tilt, or material of the measured object, thus providing a reliable depth reference.

[0057] like Figure 2 and Figure 3 As shown, in some specific embodiments, a lateral microscopic vision system is disposed inside and at the lower end of the measuring probe 2 to acquire images of the inner cavity sidewall; the lateral microscopic vision system includes: a miniature image sensor 3, a miniature lens module 31 and a lateral projection light source 32, whose optical axis is folded by a reflective optical element 33 so that its effective line of sight is perpendicular to the axial direction of the measuring probe 2.

[0058] It should be noted that the miniature image sensor 3 is electrically connected to the miniature lens module 31 via a cable. The miniature image sensor 3 is preferably a CMOS image sensor of model S15611-10, and the miniature lens module 31 is preferably a Hongjia Imaging GC0308 miniature macro camera module. The miniature image sensor 3 is installed inside the housing 21 of the measuring probe 2, and the miniature lens module 31 and the side-projection light source 32 are both installed in the integrated cavity 22 at the lower end of the measuring probe 2.

[0059] Among them, the side-projection light source 32 adopts miniature high-brightness LED illumination to uniformly project light into the target field of view of the side-projection microscopic vision system, ensuring that the inner cavity sidewalls receive sufficient and uniform illumination during imaging, effectively suppressing the shadow and uneven reflection problems commonly found inside deep holes.

[0060] Furthermore, the reflective optical element 33 is a 45° miniature right-angle reflective prism or mirror, which is formed by processing optical glass, preferably fused silica, which has an extremely low coefficient of thermal expansion and excellent ultraviolet transmission performance. It is fixed at the bottom of the measuring probe 2 and located in front of the line of sight of the miniature lens module 31.

[0061] Specifically, when the measuring probe 2 is inserted into the cavity being measured, the lateral microscopic vision system uses the reflective optical element 33 to fold the light path by 90°, which changes the downward viewing angle of the micro-lens module 31 to a side view towards the side of the side-projecting light source 32. This allows for direct and clear imaging of the sidewall surface of the cavity, avoiding obstruction by the orifice. Thus, even in deep holes with high aspect ratios and internal steps, the sidewall contour information can be clearly and completely captured, effectively solving the problem of visual blind spots in high aspect ratio cavities. This significantly improves the observability and data integrity of sidewall features, thereby providing a continuous and complete sidewall morphology data foundation for subsequent three-dimensional dimensional analysis and reconstructing the complete three-dimensional morphology of the cavity.

[0062] In some specific implementations, the control system is electrically connected to the multi-axis motion platform 1, the confocal laser sensor, and the lateral microscopic vision system. It is used to control three-axis motion, synchronously trigger laser measurement and image acquisition, and perform internal cavity three-dimensional topography reconstruction and dimensional measurement through data fusion processing. The control system includes: an industrial computer, a motion control card, an image acquisition card, a laser controller, and a host computer.

[0063] In this embodiment, the industrial computer uses a multi-core processor from the Intel Core i7 / i9 or Xeon series, and is equipped with at least 16GB of high-speed DDR4 / DDR5 memory and at least 500GB of NVMe solid-state drive to meet the needs of large data processing and real-time response. It is used to run a real-time operating system to ensure the real-time and deterministic response of key tasks such as motion control and data acquisition.

[0064] The motion control card uses a digital signal processor or field-programmable gate array as the core processor to provide high-speed, parallel data processing capabilities and deterministic control cycles. The motion control card communicates with the multi-axis motion platform 1 via an Ethernet bus to perform synchronous control and trajectory planning of X, Y and Z axis motion, and to achieve high-speed and high-precision positioning of the measuring probe 2 on the predetermined scanning path.

[0065] The image acquisition card is compatible with industry standard protocols such as GigE Vision or CoaXPress to support image data transmission from the miniature image sensor 3. GigE Vision transmits images via a standard Gigabit Ethernet interface, while CoaXPress provides higher bandwidth and lower latency via coaxial cable.

[0066] The laser controller is used for parameter configuration of wavelength range and exposure time of the confocal laser sensor, signal acquisition, peak wavelength identification and distance conversion data processing. It exchanges data with an industrial computer through a serial communication interface to provide real-time, high-precision Z-axis distance data.

[0067] The host computer is based on a modular architecture, using C++ or Python programming languages, and integrates image processing libraries, point cloud processing libraries, and 3D modeling libraries to implement functions from data acquisition to final report generation; specifically including:

[0068] The module is responsible for sending motion commands to the motion control card, receiving position feedback, and executing trajectory planning; the module is responsible for receiving and caching image data from the lateral microscopic vision system via the image acquisition card; the module is responsible for receiving and processing distance data transmitted from the laser controller, performing filtering, calibration, and Z-axis coordinate transformation; the module is responsible for synchronizing and fusing data from the confocal laser sensor and the lateral microscopic vision system in a unified coordinate system; the module is responsible for generating a complete 3D model of the cavity based on the fused point cloud data; the module is responsible for performing geometric analysis on the 3D model and calculating various dimensional parameters; and the module is responsible for providing an intuitive user interface for parameter setting, task management, real-time monitoring, result visualization, and report generation.

[0069] like Figure 4 and Figure 5 As shown, in some specific embodiments, the multi-axis motion platform 1 is used to carry and drive the measuring probe 2 to move along the X, Y and Z axes in the workspace; the multi-axis motion platform 1 includes: an X-axis motion mechanism, a Y-axis motion mechanism installed at the X-axis end of the X-axis motion mechanism, and a Z-axis motion mechanism installed at the Y-axis end of the Y-axis motion mechanism.

[0070] The X-axis motion mechanism, Y-axis motion mechanism, and Z-axis motion mechanism each include: a mounting block 11, a translation block 12 disposed on one side of the mounting block 11, and several cross roller guides 13 installed between the mounting block 11 and the translation block 12; a translation groove 14 is provided on one side of the mounting block 11, a connecting block 15 is fixed on one side of the translation block 12, and one side of the housing 21 of the measuring probe 2 is installed on one side of the translation block 12; the side of the connecting block 15 is slidably connected to the inner side of the translation groove 14, and a lead screw 16 is rotatably connected to the inner side of the translation groove 14 through a bearing; the inner side of the connecting block 15 is threadedly connected to the side of the lead screw 16; a servo motor 17 is fixed at the bottom of the mounting block 11, and the output end of the servo motor 17 is fixed to one end of the lead screw 16 through a coupling.

[0071] It should be noted that the bottom of the translation block 12 in the X-axis motion mechanism is fixed to the top of the mounting block 11 in the Y-axis motion mechanism, and the bottom of the translation block 12 in the Y-axis motion mechanism is fixed to the top of the mounting block 11 in the Z-axis motion mechanism; the servo motor 17 is preferably a 70BL76; one side of the cross roller guide 13 is fixed to one side of the mounting block 11, and the top of the other side is fixed to one side of the translation block 12. The number of cross roller guides 13 is preferably two, symmetrically arranged between the mounting block 11 and the translation block 12 along the translation direction, and the contact pressure of the cross roller guide 13 is adjusted by the pre-tightening bolts to ensure that the guide rails are gapless and have uniform load.

[0072] Specifically, the X, Y, and Z axis motion mechanisms enable the independent movement of the measuring probe 2 in the X, Y, and Z directions within space through vertically arranged translational directions. When the servo motor 17 drives the lead screw 16 to drive the connecting block 15 to move linearly along the translation groove 14, the connecting block 15 can push the translation block 12 to translate along the cross roller guide 13. The two-point contact design of the cross roller guide 13 effectively counteracts the overturning moment of the translation block 12 and improves the radial stiffness. The translation groove 14 on the top of the mounting block 11 provides guidance for the connecting block 15, enabling smooth displacement in the X / Y / Z axis directions. This ensures the independence of the movement of each axis and transmits the driving force through rigid connection, providing a reliable motion basis for precision measurement.

[0073] Understandably, the X-axis motion mechanism, Y-axis motion mechanism, and Z-axis motion mechanism should also include a high-resolution optical encoder for position feedback, preferably an incremental or absolute optical encoder. For the incremental optical encoder, its measurement period is designed to be 20 nm. Combined with a high-performance interpolation circuit, the original period signal is subdivided to a reading resolution of 0.01 micrometers. While providing extremely high resolution, this configuration requires the system to be zeroed upon startup. The absolute optical encoder, on the other hand, does not require zeroing after the system is powered on and can provide unique absolute position information, further simplifying the operation process and improving the reliability of the system. Moreover, the effective measurement surface of the optical encoder must be parallel to the movement direction of the precision cross roller guide 13 to minimize Abbe error.

[0074] Example 2: A measurement method for a laser-based precision image measurement device is provided, comprising the following steps:

[0075] S1. Before measurement, the workpiece to be measured is initially positioned. By using a preset normalized cross-correlation matching or geometric template matching algorithm based on shape context, the position and orientation of the orifice of the inner cavity to be measured in the coordinate system of the multi-axis motion platform 1 are identified.

[0076] Furthermore, after obtaining the preliminary positioning results, the motion control module of the control system calculates and plans the safe descent path of the measuring probe 2 based on the results and the known depth and diameter of the inner cavity. The motion control card drives the multi-axis motion platform 1 to move the measuring probe 2 above the opening of the inner cavity to be measured and descend vertically along the planned path.

[0077] During the process of the measuring probe 2 slowly entering the inner cavity being measured, the confocal laser sensor monitors the absolute distance between the lower end face of the measuring probe 2 and the bottom of the inner cavity in real time at a frequency of 5000 points per second. The control system compares the distance value fed back by the confocal laser sensor with the preset safe distance threshold in real time. Once the distance is less than the threshold, the descent is slowed down or stopped, so that the measuring probe 2 is at the starting measurement height.

[0078] S2. After the probe is safely inserted into the cavity and positioned at the initial measurement height, the fine multi-height section scanning measurement stage is entered to systematically obtain the full depth information of the cavity.

[0079] S21, The Z-axis of the multi-axis motion platform 1 is fixed at the preset first measurement height H1.

[0080] It should be noted that the measurement height H1 is determined based on the overall geometric characteristics of the cavity, especially its depth and diameter, as well as the field of view and working distance of the lateral microscopic vision system. This is to ensure that the field of view of the lateral microscopic vision system can completely cover the side wall area to be measured, while avoiding interference between the measurement probe 2 and the cavity wall.

[0081] S22. The motion control module of the control system drives the X-axis motion mechanism and Y-axis motion mechanism of the multi-axis motion platform 1, so that the measuring probe 2 moves along the predetermined two-dimensional plane scanning path within the horizontal plane at a fixed height H1.

[0082] It should be noted that the scanning path is optimized based on the geometry of the cavity and the data acquisition efficiency requirements. For circular cavities, a spiral scanning path provides uniform coverage and high efficiency. For square or irregularly shaped cavities, a serpentine scanning path is more suitable. Concentric circular trajectories are used to accurately measure roundness or concentricity. The scanning speed is a balance between the data acquisition frequency of the confocal laser sensor and the lateral vision system and the required point cloud density. For example, if the laser sensor frequency is 5000 Hz and the lateral vision frame rate is 60 Hz, the scanning speed needs to be between 1 and 10 mm / s to obtain sufficient laser points and image information at each pixel resolution.

[0083] S23. During the two-dimensional plane scanning process, the confocal laser sensor and the lateral microscopic vision system are triggered and data is acquired synchronously. The confocal laser sensor continuously measures the absolute distance L from the lower end face of the probe 2 to the current point at the bottom of the inner cavity at a preset frequency. The lateral microscopic vision system simultaneously captures images of the inner cavity sidewall facing the probe at a preset frame rate.

[0084] S24. For each scanning point, the control system calculates the absolute height coordinate Z of the current point at the bottom of the inner cavity in real time using the laser ranging value L acquired in real time and the current mechanical position H1 of the Z-axis of the multi-axis motion platform 1. bottom =H1-L.

[0085] S25. After completing the XY plane scanning and data acquisition at the current height H1, the control system drives the Z-axis motion mechanism of the multi-axis motion platform 1 to move to the next measurement height H2 with a preset step size. Repeat steps S22-S24 to continuously perform XY plane scanning and synchronous data acquisition until the measuring probe 2 covers the entire depth range of the inner cavity from the bottom of the cavity upwards or from the top downwards.

[0086] S3. After completing the data acquisition of all height sections, perform data fusion and 3D reconstruction to transform the acquired raw data into usable 3D models and dimensional information.

[0087] S31. For each acquired image of the inner cavity sidewall, the control system executes an image preprocessing algorithm; a Gaussian filter is used for smoothing to remove high-frequency noise, or a median filter is used to remove salt-and-pepper noise to improve image quality, and adaptive histogram equalization or CLAHE algorithm is used for contrast enhancement to enhance the distinction between the target and the background in the image.

[0088] Furthermore, after preprocessing, an edge detection algorithm, either Canny edge detection, Sobel operator, or Laplacian operator, is used to identify the rough edges of the inner wall contour from the image. Then, a sub-pixel-level edge localization algorithm, either Zernike moment, Gaussian curve fitting, or B-spline curve fitting, is used to extract the pixel coordinates of the inner wall contour in the image coordinate system. Here, the pixel coordinates represent the precise geometric boundary of the inner cavity sidewall on the two-dimensional image projection.

[0089] S32. Since the lateral microscopic vision system has undergone a pre-calibrated camera calibration process, its precise internal and external parameters have been obtained; among them, the camera calibration uses the Zhang Zhengyou calibration method or other checkerboard calibration methods, and the obtained internal parameters include the focal length (f). x ,f y ), principal point coordinates (c x ,c y ), radial distortion coefficients (k1,k2,k3) and tangential distortion coefficients (p1,p2); the external parameters are the rigid body transformation matrix between the camera coordinate system and the probe coordinate system, namely the rotation matrix R and the translation vector T;

[0090] Furthermore, using calibration parameters, combined with the Z-axis height H of probe 2 during the current sidewall image acquisition, i The extracted 2D pixel coordinates (u,v) are converted into 3D spatial coordinates (X,Y,Z) in a unified world coordinate system.

[0091] Specifically, for each extracted pixel, image distortion is eliminated through inverse distortion correction transform, and then inverse projection transform is performed, combined with the Z-axis height H. i The 3D coordinates of the device are calculated in the world coordinate system. During this process, considering that the optical axis of the lateral microscopic vision system is perpendicular to the main axis of the measuring probe 2, the determination of the Z-axis coordinate mainly depends on the positioning accuracy H of the platform's Z-axis. i The accuracy of the X and Y coordinates mainly depends on the resolution and calibration accuracy of the lateral microscopic vision system, which elevates the two-dimensional contours in all sidewall images into three-dimensional point clouds.

[0092] S33. Using the iterative nearest point or its variant point cloud registration algorithm, the laser point cloud (as a reference point cloud) and the visual point cloud are finely aligned and fused. Based on the fused high-precision point cloud data, the 3D reconstruction module uses the Poisson reconstruction algorithm, the traveling cube algorithm, or the triangulation algorithm to generate a complete, high-fidelity 3D surface model of the cavity.

[0093] S4. Based on the reconstructed complete 3D model, the dimension analysis module executes a geometric analysis algorithm to calculate the inner diameter, roundness, depth, taper, or internal step height of the cavity by fitting a cylindrical surface, plane, or conical surface.

[0094] For example, the roundness dimension can be obtained by calculating the deviation through least squares fitting of a circle, and the coaxiality can be calculated by the deviation between the central axis and the reference axis.

[0095] This invention controls a multi-axis motion platform 1 to scan a predetermined path at different Z-axis heights, and calculates the absolute height coordinates of the bottom of the cavity in real time by combining laser ranging values. Its layered scanning can cover the entire depth range of the cavity, ensuring that the cross-sectional data of each layer from the opening to the bottom of the cavity is collected. It can achieve full-range data coverage in the depth direction of the cavity, effectively avoiding local omissions, and thus providing accurate layered height benchmarks for three-dimensional reconstruction.

[0096] By fusing the depth information obtained from laser measurement with the sidewall contour information extracted by the vision system, the metrological accuracy of laser in the Z direction and the imaging detail advantage of vision in the XY plane can be fully utilized. Under a unified world coordinate system, sparse laser point clouds and dense visual point clouds are stitched and fused together, and a complete 3D model is generated through a 3D reconstruction algorithm. This allows for the reconstruction of a complete and accurate 3D morphology of the internal cavity, enabling more precise calculation of key dimensions such as inner diameter, roundness, and step height. This ensures the data integrity of high aspect ratio internal cavity precision measurement and effectively improves the overall measurement accuracy.

[0097] The above description is based on the preferred embodiments of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of the invention is defined by the appended claims rather than the foregoing description, and all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0098] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A precision image measuring apparatus based on laser measurement, characterized by, The application relates to a multi-axis motion platform, a measurement probe and a control system. The multi-axis motion platform is used for carrying and driving the measurement probe to move along X, Y and Z axes in a working space. The measurement probe is a probe-like structure which can enter a measured inner cavity and is installed at the end of the Z axis of the multi-axis motion platform and internally integrated with a confocal laser sensor, a lateral microscopic vision system and the like. The confocal laser sensor is arranged in the inside and lower end of the measurement probe and is used for emitting and receiving laser along the main axis direction of the measurement probe. The lateral microscopic vision system is arranged in the inside and lower end of the measurement probe and is used for acquiring the image of the inner cavity side wall. The lateral microscopic vision system comprises a miniature image sensor, a miniature lens module and a lateral light source, and the optical axes of the miniature image sensor, the miniature lens module and the lateral light source are folded through a reflecting optical element so that the effective visual line direction is perpendicular to the axis direction of the measurement probe. The control system is electrically connected with the multi-axis motion platform, the confocal laser sensor and the lateral microscopic vision system and is used for controlling the three-axis motion, synchronously triggering the laser measurement and the image acquisition and performing the inner cavity three-dimensional topography reconstruction and size measurement on the data fusion processing. The miniature image sensor is installed in the shell of the measurement probe, the miniature lens module and the lateral light source are both installed in the integrated cavity at the lower end of the measurement probe, the reflecting optical element is a 45-degree miniature right-angle reflecting prism or a mirror and is fixed at the bottom of the measurement probe and located in front of the visual line of the miniature lens module.

2. The precise image measuring apparatus based on laser measurement according to claim 1, characterized in that: The confocal laser sensor comprises a laser light source installed in the top shell of the measurement probe and a focusing lens group installed in the integrated cavity at the lower end of the measurement probe, and the output end of the laser light source is connected with the focusing lens group through an optical fiber.

3. The precise image measuring device based on laser measurement according to claim 1, characterized in that: The focusing lens group is coaxially arranged with the measurement probe, and the laser light source is a wide-spectrum or multi-wavelength semiconductor laser.

4. The precise image measuring apparatus based on laser measurement according to claim 3, characterized in that: The control system comprises an industrial computer, a motion control card, an image acquisition card, a laser controller and an upper computer.

5. The precise image measuring device based on laser measurement according to claim 1, characterized in that: The industrial computer adopts a multi-core processor and is used for running a real-time operating system. The motion control card communicates with the multi-axis motion platform and is used for synchronously controlling and trajectory planning of the X, Y and Z axis motion. The image acquisition card is used for receiving the image data of the miniature image sensor. The laser controller is used for parameter configuration, signal acquisition and data processing of the confocal laser sensor and exchanges data with the industrial computer. The upper computer is based on a modular architecture and comprises a motion control module, an image acquisition module, a laser data processing module, a data fusion module, a three-dimensional reconstruction module, a size analysis module and a man-machine interaction interface module. The multi-axis motion platform comprises an X-axis motion mechanism, a Y-axis motion mechanism installed at the end of the X axis of the X-axis motion mechanism and a Z-axis motion mechanism installed at the end of the Y axis of the Y-axis motion mechanism.

6. The precise image measuring device based on laser measurement according to claim 1, characterized in that: ​ The X-axis movement mechanism, the Y-axis movement mechanism and the Z-axis movement mechanism each comprise a mounting block, a translation block arranged on one side of the mounting block, and a plurality of cross roller guides mounted between the mounting block and the translation block; one side of the mounting block is provided with a translation slot, one side of the translation block is fixed with a connecting block, and one side of a shell of the measurement probe is mounted on one side of the translation block; The side of the connecting block is in sliding connection with the inner side of the translation slot, the inner side of the translation slot is rotationally connected with a lead screw through a bearing, the inner side of the connecting block is in threaded connection with the side of the lead screw, and the bottom of the mounting block is fixed with a servo motor, and an output end of the servo motor is fixed with one end of the lead screw through a shaft coupling.

7. A method of measuring with a laser measuring based precision photogrammetry apparatus according to any one of claims 1 to 6, characterized in that, The method comprises the following steps: S1, the control system controls the multi-axis movement platform to move the measurement probe above the orifice of the inner cavity and vertically descend to make it deep into the inner cavity; S2, the Z-axis of the multi-axis movement platform is fixed at different heights, and the X and Y axes of the multi-axis movement platform are driven on each height surface to drive the measurement probe to perform planar scanning according to a predetermined scanning path; during the scanning process, a confocal laser sensor is triggered synchronously to continuously measure the absolute distance value from the current point on the bottom of the inner cavity, and a lateral microscopic vision system continuously collects images of the opposite side wall of the inner cavity; S3, the control system processes the images collected by the lateral microscopic vision system to extract two-dimensional profile coordinates of the side wall of the inner cavity, and converts the two-dimensional profile coordinates into three-dimensional point cloud data of the side wall in combination with the calibration parameters of the lateral microscopic vision system and the current Z-axis height value; meanwhile, the three-dimensional point cloud data of the bottom of the inner cavity is calculated according to the distance value measured by the confocal laser sensor and the current Z-axis height value, the three-dimensional point cloud data of the side wall and the three-dimensional point cloud data of the bottom are fused in a unified coordinate system, and a complete three-dimensional model of the inner cavity is reconstructed; S4, the geometric dimensions of the inner cavity are calculated based on the reconstructed complete three-dimensional model.

8. The measuring method of the precise image measuring apparatus based on laser measurement according to claim 7, characterized in that: In the step S2, the predetermined scanning path is one of a spiral line, a serpentine line or a concentric circular trajectory.

9. The measuring method of the precise image measuring apparatus based on laser measurement according to claim 7, characterized in that: In the step S3, the two-dimensional profile coordinates of the side wall of the inner cavity are extracted through edge detection and sub-pixel positioning algorithm; the fused point cloud data is processed by a three-dimensional modeling algorithm to generate the three-dimensional model, and the three-dimensional modeling algorithm is one of a Poisson reconstruction algorithm, a marching cubes algorithm or a triangular meshing algorithm.

10. The measuring method of the precise image measuring apparatus based on laser measurement according to claim 7, characterized in that: In the step S4, the geometric dimensions include one or more of an inner diameter, a roundness, a depth, a taper and an internal step height.

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