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As the development of the measuring technology, laser displacement sensors become the most commonly used ones in the field of dimensional metrology as a result of their versatility and mature technology. However, as the differences of environment conditions and the variation of measured surfaces, the measuring errors of the laser displacement sensor may be large when used in actual application, in which the nominal accuracy of the laser sensor cannot be reached. Therefore, a precsion optimization method for the laser displacement sensor is proposed in the paper based on analysis of the principle of optical trigonometry, which can be used to reduces the measuring errors. The method is a kind of spatial filtering algorithm based on the self-adjusting domain. On the basis of the idea of spatial filtering, the method could determine the measuring errors and the optimization region according to the different measured surfaces automatically. As the experiment results show, the optimization method could be used to describe the measured object precisely and decrease the measuring error to up to 50%, which may deal with the low accuracy of the optical scanning and measuring task. With the accuracy optimization method proposed in the paper, the sensor can reach the measuring accuracy of micrometer level. Therefore, the measurement of high efficiency and high precision can be achieved.

In order to improve the quality and efficiency of forging process, it needs to execute on-line dimensional measurement of the forgings. In the paper, a laboratory color vision measuring system is set up and the combination of digital and physical filtering is adopted to improve the image quality based on the radiation characteristics of high-temperature forgings. The digital filtering technology is a kind of image processing methods, in which the R component of the forging image is removed. While, the physical filtering technology is achieved by optical filters installed in front of the CCD, in which strong self-emitted radiation from the hot parts can be filtered out. In order to evaluate the image quality, the image contrast is applied, which is generally defined as the difference value between average gray scale of object region and that of background region. In the experiments, image contrast derived with filters at different sample points set from 800°C to 1200°C is compared to determine the optimal scheme of filters to be selected. Results of experiments indicate that the application effect of filters is dissimilar when the forging is in different temperature ranges. Through comparison, the optimal selection scheme of filters is determined to derive high quality image of forgings at different temperatures, which lays a solid foundation for the subsequent image processing.

In the field of aeronautics, the tip clearance of rotor exerts a crucial influence on the performance of the aero engine. As defined as the radial distance between the top of the blade and the inner wall of the casing, the tip clearance of too large or small size will adversely affect the normal running of the engine. In order to realize accurate measurement of the tip clearance in a simple way, a non-contact measuring method by the chromatic confocal displacement sensor is proposed in the paper. The sensor possesses the advantages such as small volume, good signal-to-noise ratio, high accuracy and response frequency etc., which make it be widely used in engineering and industry. For testing the performance and potential application of the sensor, a simulation testing platform is established. In the platform, a simulation blisk is installed on the air bearing spindle and a chromatic confocal displacement sensor is fixed on the platform to measure the displacement variation of the blade tip, which can be used to characterize the variation of the tip clearance. In the simulation experiments, both of single and continuous measurement of the tip clearance of the 36 blades on the blisk is executed. As the results of experiments show, the chromatic confocal displacement sensor can meet the requirements of measuring task, in which both of high measuring efficiency and accuracy could be achieved. Therefore, the measuring method proposed in the paper can be utilized in the actual assembling sites of the aero engine.

Fast and accurate registration research has important theory significance and engineering application value in improving digital measurement accuracy and efficiency. Aiming at solving registration precision and registration speed problem, the extraction scheme of contour dominant point, correspondence establishment method and the objective function of registration are discussed in the paper. Compared with other extraction ones, the scheme can extract typical characters of the blade contour effectively. It is essential to sample measuring points which can represent the entire blade with sufficient confidence and accuracy. Unlike the registration method that only minimizes the one-way distance between the data points and the initial fitted curves, the weighted mutual (two-way) distances between the template profile curves and the data points as the objective function is considered in the paper. The registration algorithm based on iterative closest point algorithm is introduced in details. Using experimental method, the validation of proposed model registration algorithm is verified. Two experimental examples were used to demonstrate registration precision and effectiveness.

For solving the difficult problem that there is no effective way to measure abnormal holes located at blade erection loop of aero-engine case, an image measurement system based on high precision air-bearing turntable is established in this paper. The issue that monocular vision can’t measure curved surface has overcome by using high precision turntable to make sure high positioning accuracy of the surface abnormal holes and high-resolution microscope lens which is used to image local tiny features. Besides, an algorithm of determining the boundary points of a trailing edge on the contour of abnormal hole is proposed to achieve a rapid fitting and accuracy. After experiments and analysis, results show that the system can be used to measure local tiny features on curved surfaces validly and efficiently.