Complex parts in the aerospace field need to deal with high temperature, high pressure, high speed and complex electromagnetic environment, and other new service environments, parts usually need to design some precision microstructures such as micropores to bear the function of heat dissipation and pressure resistance, which puts forward extremely high requirements for the manufacturing accuracy of the parts themselves, and also requires the measurement equipment to take into account the dimensional accuracy and positioning accuracy of the parts. At present, the measurement technology of multiple sensor combinations is mainly adopted, and the macro and micro feature data is obtained by using the measurement characteristics of each sensor, and finally the data is registered and fused or three-dimensional stitching, the main registration fusion method is to downsample the microscale measurement data of high-precision large data and upsample the large-scale measurement data with relatively low accuracy and small data volume, and finally make the data of these two scales achieve similar accuracy to register them, but this method does not form a more correct and mature method in the upsampling process, which makes the accuracy of upsampling unsatisfactory, resulting in doubts about the correctness of the final result. In addition, the current multi-sensor integration method is mostly limited to sensors of similar scale, so this paper proposes an integrated calibration method between sensors with large scale differences, which can overcome the problem of coordinate integration difficulties caused by the difference in accuracy and resolution between sensors, and use typical aerospace parts for measurement verification, which proves that this method can be effectively applied to such parts with cross-scale structural features.

By preliminarily establishing a model of multi-sensor combination measurement to derive the coordinate system conversion closed loop, due to the relative position of the probe and the microscope camera is constant, which is the invariants in the closed loop and the key link to complete the accuracy conversion in the conversion closed loop. This paper innovatively uses a special calibration block as a transit target to calibrate this conversion relationship, this calibration block is designed and processed from the perspective of controlling the accuracy of coordinate conversion, it contains sixteen macro feature points and eight micro feature points, because the field of view of zoom scanning microscopy equipment is extremely small, and calibration requires at least six feature points to be set in such a field of view, so this paper designs such a microstructure into a square groove structure, using its corner points as marker points, This also facilitates the search for more accurate feature point coordinates in microscopic reconstruction results. In addition, silicon is used for the processing of this calibration block, so that the tiny square groove structure can be precisely machined. Finally, the above coordinate transformation relationship is solved by a relatively simple quaternion method, that is, the calibration of the geo-coordinate system of two sensors of different scales is completed.

Using the above model and the fixed conversion relationship solved by the calibration method proposed in this paper, the data of each local measurement can be converted to the same coordinate system. The experiment in this paper chose an injector, a space cross-scale part with a conical surface. There are 12 holes with a diameter of about 0.5 mm evenly distributed above, measure them one by one while using a binocular camera to record the global control points distributed on the microprobe during each measurement, use these global control points to calculate their conversion relationship to the binocular system, and then the pose matrix represented by the left multiplication calibration result can obtain the conversion relationship from a specific point to the global coordinate system, respectively apply the conversion relationship to the measurement results of specific points (represented as point cloud datasets), you can obtain each local area data with the same coordinate system, and make them a simple collection to obtain a complete high-precision large-scale topography dataset. The central coordinates of each hole on its surface and the direction vector of each hole axis are obtained by solving some processing algorithms, because these quantities can accurately represent the positioning accuracy of holes, compare them with the theoretical model to obtain error values, and then compare the error values with the processing accuracy of parts, which can verify the final accuracy of the measurement method and the degree of improvement of accuracy. The final result is that the central coordinate error is 0.029 mm, the axial error of the hole is 0.1140°, which is greatly improved compared with the central coordinate error of 0.05 mm and the axial error of the hole of 0.167° in the machining accuracy requirements, in addition, the results of this paper are more accurate than the scanning results of the single-scan measuring instrument Gocator sensor.

In this paper, a cross-scale measurement method based on macro-micro composite calibration is proposed for precision three-dimensional optical measurement of parts with cross-scale micro-nano structure, which takes into account the accuracy difference of macro-micro measurement equipment and the integrity and correctness of microscopic raw data, and completes the conversion relationship and accuracy transition of the global model of the binocular-microscopic combined measurement system by designing and precision processing the macro-micro composite calibration block, so as to realize the global calibration of cross-scale measurement equipment. By comparing with the roundness and flatness of the center point set of each hole in the theoretical model to analyze the splicing accuracy, it is concluded that the roundness error of the coordinate distribution of the hole surface of the microhole is 0.0438 mm and the flatness error is 0.0252 mm, and the positioning accuracy of the parts measured by this method is analyzed by comparing with the position of each hole center pose in the theoretical model, and the point error value is less than 0.029 mm and the axial error is less than 0.1140°. The experimental results show that compared with direct measurement methods such as surface structured light, this measurement method has the advantages of higher accuracy and more accurate morphology reconstruction, and is suitable for the measurement of microstructure, topography, dimensional accuracy, and positioning accuracy of a type of cross-scale parts.