In order to enhance the robustness of IR fast small target tracking, a novel mean shift tracking algorithm using improved similarity measure of is proposed. Firstly, problems of local background interfering in original mean shift algorithm for tracking fast motion small target is analyzed, and the reasons is located in the Bhattacharyya coefficient similarity measure expression for all gray weights of components are same, which cannot reflect the advantage contribution of the small target’s gray component in the process of measuring similarity, causing serious interference of the background in the tracking process, leaving the algorithm converging easily. Therefore, to solve this problem, the improvements Bhattacharyya coefficient similarity measure with the local background information fused is proposed. Then, shift vector is deduced in the framework of mean shift by regarding Bhattacharyya coefficients as the similarity measure.In shifting process, the robustness of the small target tracking is improved effectively according to target gray level of large membership degree with high shift weight, and vice versa with low shift weight, which the background interference is suppressed to some extent. In sake of verifying the performance of the proposed algorithm, the classical mean shift algorithm and the algorithm of this paper is used in the target tracking simulation experiment, as well as the infrared image sequences containing the small fast targets of uncooled infrared camera is used. Finally the experimental result indicates that the performance of tracking the small fast target in IR images is robust.
The theoretical principle of Stressed Mirror Polishing (SMP) is introduced, including the representation method of elastic deformation, the formulations of discrete bending moment and shearing force. A Finite Element Analysis (FEA) simulation model of has been set up by ANSYS software. The warping facility in this model is consisted of 36 aluminum alloy arms equally distribute on the ambit of mirror blank. Two forces are applied on each arm to provide bending moment and shearing force. Taking type 82 segment of Thirty Meters Telescope (TMT) primary mirror for example, a FEA simulation of mirror blank deformation has been performed. Simulation result shows that, the deformation error is 33μm PV. The theoretical deformation PV value is 205μm and the simulation deformation PV value is 172μm, converging rate reaches to 0.84 in a single warping cycle. After three or four warping cycles, the residue error may converge into 1μm.
In order to improve the performance of heterogeneous image matching and registration, the Weighted Voting Accumulation Measure(WVAM) based on the edge feature and image registration algorithm based on the steepest descent of the likelihood function are proposed. The WVAM is capable of resisting the interference of noise and the similarity region and can achieve matching location of template. On this basis, the likelihood function of edge sets registration is established on the basis of Gauss Mixture Model (GMM) of point sets. In order to achieve the registration between the template and matching area, and resolve the optimum transformation parameter by using the steepest descent method, the likelihood function is regarded as objective function and the affine transformation parameter is regarded as the optimization variance. The results of simulation experiments of this algorithm proved that the good performance of template and registration.
The wavefront function can be achieved by fitting the optical surfaces date using Zernike polynomials because of the corresponding relation between Zernike polynomials and Seidel aberrations. In this paper, the reason of the stable solution cannot be achieved when proceed to fit wavefront by least square, Gram-Schmidt orthogonalization and Householder transformation is deduced in theory. The Zernike coefficients fitting method based total variation (TV) regularization is presented to resolve the instability of numerical solution because of there are errors in phase values obtained by optimization algorithm in Least Square, Gram-Schmidt orthogonalization and Householder transformation. The solving model of Zernike coefficients is developed, and the regularization term is introduced in solving model, then the L-curve method is applied to determine the regularization parameter and the modified steepest descent method is applied to solve Zernike coefficients. The simulation experiment shows that the proposed algorithm can be achieve the stable fitting coefficients with the error on fitting data.
The optical systems with large collecting aperture and high resolution are the future development directions of optical
systems on orbit. The primary mirror of optical system is segmented for its advantages in reducing the difficulty of
manufacturing to achieve high imaging resolution. Once on orbit, it needs to correct the misalignment errors in optical
system introduced by the effect of various factors. The phase retrieval based on quasi-Newton method nonlinear
optimization is proposed to sense the wavefront aberration induced by segmented mirrors in the optical system. And the
BFGS method is utilized to seek the optimum value of wavefront aberrations. Then the different defocus impacted on
detection accuracy is analyzed. The result of the simulation experiment indicated that once select the suitable defocus,
the phase retrieval method can control the wavefront detection error less than 6%.
ABSTRACT
The optical systems with large collecting aperture and high resolution are the future development directions of optical
systems on orbit. Once on orbit, it needs to correct the misalignment errors in optical system introduced by the effect of
various factors. For the purpose of decreasing the complex degree of alignment on orbit and increasing the reliability, the
nonlinear function mathematical model between primary mirror misalignments and Zernike coefficients was established.
Then a certain simulated off-axis three-mirror system was corrected, the result indicated that the wavefront RMS
reduced to 0.02λ. It satisfied the demands of alignment on orbit.
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