Primary Mirror System Research Articles

Design and analysis of segmented-mirror primary mirror system

with the development of space exploration, the resolution of optical system is required to be higher and higher. According to the Rayleigh criterion, the resolution of the optical system is directly proportional to the aperture. However, due to the influence of processing capacity and size of the rocket fairing, it is difficult to achieve one single large aperture. Therefore, the scheme of using small size segmented-mirror to achieve one large aperture becomes an effective form. Because location difference between the deployment and the ideal position, the imaging quality will be affected, and cannot be imaged in serious case. For the analysis of influence of the position error on the imaging quality, the traditional method is to analyze on the optical transfer function and Strehl ratio in theory, ignoring the influence of various aberrations that cannot be corrected by the optical system itself. In this paper, the segmented-mirror primary mirror system model is established to analyze the influence of the position error and the real influence of the various aberrations of the system, so as to complete the analysis of the influence more comprehensively. Through the analysis of different position errors, we can get the final wave-front aberration and Strehl ratio of the system under the influence of position error, which can be used as a reference for the analysis of position error influence of segmented-mirror primary mirror form and sparse aperture form of large aperture optical system in the future.

A Golay3 sparse aperture optical system of primary mirror with free-form surface

To image distant and dim objects, this paper designs a sparse aperture optical system with a small F number and a large filling factor. The design process is divided into three steps. To start with, the curvature radius and spacing of the primary and secondary mirrors are calculated under the guidance of the paraxial imaging theory. Then, based on the primary aberration theory, the conic coefficients of the primary and secondary mirrors are also calculated. Finally, the node aberration theory is used to increase the field of view and eliminate the residual aberrations. Through theoretical derivation and computer-aided methods, a Golay3 sparse aperture optical system with primary mirror used Zernike polynomial is designed. The full field of view is 0.3° and the F number is 5.

Improved Spatial Modulation Diversity with High Noise Robust Based on Deep Denoising Convolution Neural Network

Synthetic aperture imaging systems can be applied to equivalently get high-resolution images of traditional monolithic primary mirror systems with less weight and costs. Spatial modulation diversity (SMD), a newly developed post-processing technology applicable for such synthetic aperture systems, is very sensitive to Gaussian noise, which greatly limits its further application. In this paper, we propose an improved SMD strategy by introducing the deep denoising convolutional neural networks (DnCNN) into the image preprocessing to improve the robustness of SMD. Results of the numerical simulations demonstrate that the strategy proposed exhibits superior performance compared to the traditional SMD technique in terms of both the root-mean-square error (RMSE) of phase estimates and the structural similarity (SSIM) of image reconstruction. In view of the superiority and robustness, the method we proposed may have important application prospects in multi-aperture imaging systems.

空间引力波望远镜主反射镜系统的结构设计优化

The structure and supporting components of the primary mirror system of space gravitational wave telescope were designed and optimized. The side three-point support was used to restrain the mirror body with the primary mirror, and the selection and layout of support points were studied. The mirror adopted a semi-enclosed structure with back drill holes, which can achieve large bending stiffness. The lightweight structure of the mirror was optimized by finite element calculation combined with multi-objective genetic algorithm. The lightweight ratio of the mirror structure reached 74% without reducing the surface accuracy. An adjustable bi-axis bipod flexure hinge structure composed of two non-barrier series flexibility elements was designed, which can compensate the surface error of the mirror. The mathematical model of the flexible hinge parallel mechanism acting on the mirror was established, and the parameters were analyzed based on MATLAB. The parameters were corrected by finite element method. Finally, the analysis of mirror shape under space thermal load was carried out. The results show that the error of mirror shape is better than λ/60, which meets the design requirements.

空间引力波望远镜主反射镜系统的结构设计优化

空间引力波望远镜主反射镜系统的结构设计优化

Conceptual Design for Control System of Segmented Primary Mirror in SEIMEI Telescope

Conceptual Design for Control System of Segmented Primary Mirror in SEIMEI Telescope

Measurement of picometer-scale mirror dynamics.

A high-speed interferometer has been designed and built to measure the dynamics of the James Webb Space Telescope primary mirror system currently under testing. This interferometer is capable of tracking large absolute motion (i.e., piston) of the mirror's entire surface over orders of magnitudes of wavelengths displacement. Preliminary tests have shown it to be capable of measuring dynamic effects on the level of tens of picometers reliably. This paper reports the details of test setup to do so, the data system used to collect and process the data, and the algorithms to distill the dynamics motions detected. The results that were obtained are presented and followed by a discussion of the conclusions and potential applications of this measurement technique.

Compact freeform off-axis three-mirror imaging system based on the integration of primary and tertiary mirrors on one single surface

In this Letter, a novel and compact freeform off-axis three-mirror imaging system and its detailed design method are proposed. The primary mirror and tertiary mirror of the system have the same surface analytical expression and they are integrated on one single freeform surface. In this way, the alignment process is made much easier due to the much fewer degrees of freedom. In addition, the difficulty and cost for the data handling, fabrication, and testing of the freeform surfaces and system can also be significantly reduced in some cases, especially compared with the configuration having multiple surfaces of different expressions integrated on one monolithic substrate. The final system has a 100 mm effective focal length and a 4°×3° field of view. The modulation transfer function of the system is close to the diffraction-limit.

Bipod flexure for 1-m primary mirror system.

We present an analytical formulation of the bipod flexure for mounting the 1-m primary mirror in a space telescope. Compliance and stiffness matrices of the bipod flexure are derived to estimate theoretical performance and to make initial design guidelines. We use finite element analysis to optimize the bipod design satisfying the application requirements. Experimental verification is achieved by vibration test with a dummy mirror system.

Optimum Design of the Support System of the SiC Primary Mirror with 1m Aperture

The support system of the one-meter SiC primary mirror was optimum designed by the finite element method. For the analysis, the 3D solid finite element model was used by the finite element software. The axial support-ring radius and the lateral support position were determined after the optimum design. The mirror deformations with different pitching angles were calculated. The maximum value of the surface figure deformation root-mean-square (RMS) is 23.84nm, which satisfies the requirement and shows the support system is reasonable and feasible.

Off-plane anastigmatic imaging in Offner spectrometers

In this paper, the imaging performance of an Offner concentric imaging spectrometer is analyzed when the spectrometer entrance slit is disposed arbitrarily on the plane that is parallel to the grating grooves and contains the common center of curvature. Astigmatism-corrected designs are obtained for off-plane incidence on the grating if one point on the slit is located on the Rowland circle of the primary mirror. In this case, the combined system of primary mirror plus diffraction grating provides two astigmatic line images oriented parallel and orthogonal to the plane of diffraction, with the former located on the same plane as the slit. Consequently, these images can be brought to a single focus on this plane by the tertiary mirror if its radius of curvature is chosen properly. In addition, coma aberration is simultaneously removed. These results can be applied to the design of two-mirror or three-mirror spectrometers, generalizing the concept of the best imaging circle and providing solutions to get anastigmatic imaging for two object points and two wavelengths.

Design Of Catadioptric Infrared Optical System With Wide Field

Many infrared optical systems usually adopt catoptric systems. Because that the system does not have chromatism and restriction of the working wave. But the coma and astigmatism of off-axis point is large, so the field of view that we can use is restricted. In the needs of infrared early warning system for sea-based, a large field of catadioptric infrared optical system is designed. The optical system breaks the limitation of traditional reflective optical system with small field of view. The system adopts two methods to expand the field of view. One is adding the calibration group before the reflecting system .The other one is that the primary and secondary reflective mirror system are used of Mangin mirror. So the optical system avoids any high-order aspheric surface .In order to match the cold aperture exactly, lens group is inserted after the first image plane. The system's field can reach 8 degree, and the ratio of obscuration is less than 0.4, and also optical transfer function achieves diffraction limit.

H2 Control of Large Segmented Telescopes

In this paper we conduct a preliminary study of control of the primary mirror of a large segmented telescope, i.e. aligning the segments to form a paraboloid. This work is motivated by the need of astronomers to study faint objects and to reach the highest possible angular resolution. First, we present background information about large segmented telescopes and our collaborative research program on large telescopes. Second, we formulate a model of the primary mirror system in state space. Third, we design a centralized controller using H2 methods for a seven-segment system which establishes the best possible performance characteristics for the laboratory-type of unit that we plan to build. Simulation results are displayed. Finally, we apply spatially-invariant distributed control techniques to an infinite segmented system that approximates a large mirror. Through the H2 norm, we calculate upper bounds for the relative displacements between adjacent segments with either a spatially-invariant infinite controller or a truncated local controller. Simulation results are also presented with a truncated local controller applied to a 19-segment system. In all cases, the results indicate that the required mirror-to-mirror surface position accuracy of 10-8 m can be achieved.

Importance of tip sensing for active control system of 30-m RIT primary mirror

The active control of 30-m ring interferometric telescope needs edge sensing and tip sensing when its primary mirror is composed by trapezoid-shaped segments, and the imaging performance of the RIT is determined by the accuracy of these two detecting approaches. Considering the detecting accuracy available in current segmented telescope active control systems, tire effect of these detecting approaches on the surface error of the RIT primary mirror is calculated from the point of error propagation. The corresponding effect on imaging performance (modulation transfer functions (MTFs) and point; spread functions (PSFs) at several typical wavelengths) of the RIT primary mirror is also simulated. The results show that tip sensing is very important. for increasing the active control quality of the RIT primary mirror under the present techniques.

실험계획법을 이용한 인공위성 주반사경 플렉셔 마운트의 최적 설계

The primary mirror system in a satellite camera is an opto-mechanically coupled system for a reason that optical and mechanical behaviors are intricately interactive. In order to enhance the opto-mechanical performance of the primary mirror system, opto-mechanical behaviors should be thoroughly investigated by using various analysis procedures such as elastic, thermo-elastic, optical and eigenvalue analysis. In this paper, optimal design of the bipod flexure mounts for high opto-mechanical performance is performed. Optomechanical performances considered in this paper are RMS wavefront error under the gravity and thermal loading conditions and 1st natural frequency of the mirror system. The procedures of the flexure mounts design based on design of experiments and statistics is as follows. The experiments for opto-mechanical analysis are constructed based on the tables of orthogonal arrays and analysis of each experiment is carried out. In order to deal with the multiple opto-mechanical properties, MADM (Multiple-attribute decision making) is employed. From the analysis results, the critical design variables of the flexure mounts which have dominant influences on opto-mechanical performance are determined through analysis of variance and F-test. The regression model in terms of the critical design variables is constructed based on the response surface analysis. Then the critical design variables are optimized from the regression model by using SQP algorithm. Opto-mechanical performance of the optimal bipod flexure mounts is verified through analysis.

A Study on the Adhesive Effects on the Optical Performance of the Primary Mirror System of a Satellite Camera

A Study on the Adhesive Effects on the Optical Performance of the Primary Mirror System of a Satellite Camera

Ultra-high-speed wide-angle catadioptric corrector system for medium-scale spherical mirror telescopes

The large amount of spherical aberration generated by a spherical mirror can be corrected by an image relay having a diameter much smaller than that of the pupil of the system. Described is a high-performance catadioptric corrector with a maximum input numerical aperture (NA) of 0.29 ( f /1.7), a fixed output NA of 0.67 ( f /0.75), and a passband of 405 to 1000 nm, that can be adapted to operate with spherical primary mirror systems having small to medium pupil diameters. Design examples are presented of systems with pupil diameters 0.5, 1, 2, and 4 m, with corresponding angular fields of 4, 2, 1, and 0.5 deg. The image in all examples is ~26 mm diameter, resolved to <4 μm root mean square (rms) over the whole field.

The U.S. National 8 m telescope project

The National Optical Astronomy Observatories (NOAO) are planning to build two 8 m telescopes, one for Mauna Kea, Hawaii, the other for a site in Chile. Optical configurations, primary mirror systems, and the telescope mounting are discussed. A new optical testing method is outlined. The system imaging goal is 0.25 FWHM. Construction could begin in the early 1990’s.