Laser speckle pattern interferometry is a kind of high-precision deformation measurement method by analyzing images of speckle patterns. Deformation of measured object can cause phase change of laser light reflected by the object and speckle fringe can be formed. The background noise is large and the phase jump is not clear in the image of speckle fringe. According to the character of the image, a kind of two-step filtering algorithm is used to enhance image quality. First, adaptive filtering algorithm is used to process original speckle fringe image. And then after three-dimensional phase image is formed by phase unwrapping of the speckle fringe phase image, mean smoothing filtering is used to reduce burr in three-dimensional phase image. The experimental results show that this two-step filtering algorithm can keep detail information in the speckle fringe image and get good deformation measurement results.
As the requirement of satellite antenna’s planar near-field test, the scanning plane, the air-bearing based platform and the satellite antenna should be measured and adjusted with high precision. In order to improve the measurement accuracy and efficiency for large scale objects, a new measurement method is proposed based on laser radar. Target ball measurement, scanning measurement and single point measurement are respectively used to measure the scanning plane, the air-bearing based platform and the satellite antenna. The working principle, automatic measurement method and measurement error are described in detail. The experimental results show that the measurement error is less than 0.1mm for 3D point coordinate and 10” for attitude angle. Compared with traditional theodolite measurement method, this method can realize automatic measurement with higher precision and efficiency.
Because of the close range photogrammetry has wide measuring range, high precision and high efficiency, the precision measurement of large size tasks take more and more important role Among them, the self-calibration measurement model based on adjustment optimization is the important reason to ensure the method to achieve high-precision measurement. However, with commercial grade SLR camera more and more applied to three-dimensional measurement, the measurement accuracy and the professional camera compared to a certain gap A large number of analyses have found that, in addition to the camera itself, the self -calibration model relies too much on the internal parameters of the camera, especially the distortion parameter, which is the important reason leading to the decrease of the measurement accuracy. In order to reduce the influence of the parameterized model on the measurement results, we propose a photogrammetric method that does not rely on the intrinsic parameters of the camera. Firstly, a non-parameterized calibration method for large field of view camera is designed by combining the perpendicular method and Zeiss calibration method. Then, the non-parameterized measurement model based on the angle information can be established after the matching of the same point and the initial value of the difference between different images. Finally, combined with adjustment optimization algorithm, the three-dimensional coordinate of the measured point in space is calculated accurately. Compared with the traditional photogrammetry results, it is proved that this method can effectively improve the photogrammetric accuracy of the large field SLR camera.
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