This PDF file contains the front matter associated with SPIE Proceedings Volume 6721, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

The Advanced Technology Solar Telescope (ATST) has a 4.24m off-axis primary mirror designed to deliver diffractionlimited images of the sun. Its baseline secondary mirror (M2) design uses a 0.65m diameter Silicon Carbide mirror mounted kinematically by a bi-pod flexure mechanism at three equally spaced locations. Unlike other common telescopes, the ATST M2 is to be exposed to a significant solar heat loading. A thermal management system (TMS) will be developed to accommodate the solar loading and minimize "mirror seeing effect" by controlling the temperature difference between the M2 optical surface and the ambient air at the site. Thermo-elastic analyses for steady state thermal behaviors of the ATST secondary mirror was performed using finite element analysis by I-DEAS^TM and PCRINGE^TM for the optical analysis. We examined extensive heat transfer simulation cases and their results were discussed. The goal of this study is to establish thermal models by I-DEAS for an adequate thermal environment. These thermal models will be useful for estimating segment thermal responses. Current study assumes a few sample time dependent thermal loadings to synthesize the operational environment.

The quest for higher angular resolution in astronomy will inevitably require the telescope with large aperture. However, the diameter of primary mirror is limited by the fabrication problems as well as the scaling laws of manufacturing costs. Optical synthetic aperture telescopes represent a promising new technology to overcome the above-mentioned problems. Three incoherent imaging techniques based on optical synthetic aperture including Fourier telescopy, Michelson interferometer and Fizeau interferometer are described in the paper. Fourier telescopy is an active imaging technique combined with the advantages of synthetic aperture measurement. Michelson interferometers measure spatial Fourier transform of objects, while Fizeau interferometers produce direct images with full instant frequency coverage. We give an overview of the basic aspects and the differences of these techniques.

There is an increasing need for precision large aspheric optics with small focal ratios for astronomical and space applications. However, testing such optics presents a challenge. Interferometric testing of aspheric surfaces often requires the use of null lenses. Many of these null lenses are tested using a certification computer-generated hologram (CGH) for better error calibration. We present a method that will measure large aspheres to a greater level of accuracy than is presently possible. We use segmented and superposed CGH elements to certify and calibrate null lens errors absolutely to a high degree of accuracy. In such holograms two different phase functions are encoded on the CGH by means of aperture division. One subaperture generates a spherical wavefront that is used to determine the pattern errors of the hologram while the second subaperture reconstructs an aspherical wavefront used to calibrate the wavefront errors of the null lens. This careful calibration process involves the removal of both axisymmetric and non-axisymmetric errors in the null test. Once this is accomplished, the null lens may be used to test the asphere to a high degree of accuracy. Our initial results show that we can test 4-meter class aspheric mirrors to better than 1nm rms surface error. In current experiments we have set a goal of measuring such mirrors to better than 1nm rms surface error.

Optical sparse aperture systems can be designed to obtain high resolution for imaging astronomical object. They are particular arrays synthesized by several small filled imaging systems. In this paper, a principle experiment is set up for optical sparse aperture system. Imaging of the extended complex object is achieved. Image restoration of the direct output by the sparse-aperture system is performed by measuring the point spread functions (PSF) and by using the Weiner filter. The correlation coefficient is proposed as a criterion to determine optimal parameter, and evaluate the performance of the algorithms. The results show that Tri-Arm array configuration among three kinds of configuration models can produce higher resolution and larger correlation coefficient value after restoration. Accordingly, based on the experimental data, the possibility is demonstrated that the optical sparse aperture systems can achieve almost the same resolution and image quality as an equivalent filled system.

This paper presents an implementation of control system of position actuators in LAMOST. Performance of actuators has been tested in laboratory. The resolution of actuators is less than 5nm. The whole control system has been successfully realized in LAMOST M_B pre-segmented experiment. The control system of position actuator adopts distributed-and-centralized mode. Displacement RMS error of the control system (including actuator and electrical control) is less than 50 nm.

This paper describes the application tendency of beryllium mirror of space astronomical instruments and the tip-tilt mirror of the correlation tracker of a Space Solar Telescope (SST). The optimization choice of tip-tilt mirror substrate material, the light-weighted scheme of tip-tilt mirror substrate, the analysis and optimization design of mirror structure were accomplished. At last, the final RMS surface figure error of 2.18×10^-6mm and PV of 1.69×10^-5mm were obtained with resonant frequency of 1609Hz, and the mass of the beryllium mirror of 47.88g. These results satisfy the technology requirements of the tip-tilt mirror of the correlation tracker. The manufacture technology of beryllium mirror substrate, the nickel plating technique on beryllium mirror substrate and optical fabrication were discussed in detail.

The mechanics and method of correction of an aberration optical imaging system by means of holographic technology were described in this paper. An experimental system for the correction of aberrations of an optical system with a low quality spherical mirror in 500mm-diameter for the imaging of finite objects was established. The correction effect was tested by comparing the interferograms and images obtained before and after corrections. Experiment results showed diffraction-limited performance of the system and residual aberration was ~ λ/8.

A 1-m class off-axis SiC aspherical mirror was polished up to 13nm rms with CCOS. The lightweight mirror structure design, CCOS procedure, as well as interferometic test set up are be presented in the paper. In addition, the residual surface error of SiC mirror is analyzed and approach to improve the surface quality is discussed.

Atmospheric turbulence and telescope aberrations all contribute to image degradation with ground-based telescopes. For measuring telescope aberrations resulted from atmospheric turbulence, we have developed a method based on phase-diversity technique. The phase-diversity technique is a novel method for reconstructing the object and the distribution of wavefront in pupil plane. Using phase-diversity method, we can independently reconstruct many instantaneous wavefront from pairs of simultaneously recorded focused and defocused images. After that, by averaging these reconstructed wavefront, the telescope aberrations are separated from dynamic wavefront induced by turbulence. The simulation of estimation of telescope aberration using phase-diversity method is conducted. The results show the phase-diversity technique can estimate the telescope aberrations effectively and root-mean-square error is about 0.08 wavelengths.

Silicon carbide (SiC) is a new type candidate material for large-scale lightweight space mirror. Its low thermal distortion, high stiffness, high optical quality, and its dimensional stability are better than other traditional optical substrate materials such as ULE, Zerodure, Beryllium (Be) and so on. In this paper, the lightweight silicon carbide space mirror blank was fabricated by reaction sintering. As a space born mirror material, silicon carbide must be an optical grade ceramic. So we prepared the silicon carbide green body with gel-casting method. Then some carbon materials were supplemented into the green body which will bring reaction-sintering with silicon in a vacuum furnace during 1500-1600°C, ultimately the reaction bonded silicon carbide was made. The diameter of SiC space mirror blank we have made is 680mm. If expanding the size of the vacuum furnace, bigger mirror blank can be obtained. The test results show that the mechanical and thermal properties of RB-SiC are excellent with bending strength of 350MPa, fracture toughness of 4.1 MPa·m1/2 and coefficient of thermal expansion(CET) of 2.67×10-6/K. The surface roughness(RMS) could be better than 3nm.

Through mathematical analysis and calculation, the author considers that the former mechanical structure(used to axial-symmetrical asphere) must be modified when being used to off-axis segment. This point is different from Dr. H.M.Martin[3]. The author puts forward two mechanical structures, electrical control types, and draws up feature graphs of movement, deformation and hoist etc. then to analyze the moving and deforming features of stressed lap on off-axis segment. At last the author gives new imagination for look-up tables and how to read out data.

With the increase of telescope size, the manufacture of monolithic primaries becomes increasingly difficult. Instead, the use of segmented mirrors, where many individual mirrors (the segments) work together to provide good image quality and an aperture equivalent to that of a large monolithic mirror, is considered a more appropriate strategy. But, with the introduction of large telescope mirror comprised of many individual segments, the problem of insuring a smooth continuous mirror surface (co-phased mirrors) becomes critical. One of the main problems arising in the co-phasing of the segmented mirrors telescope is the problem of measurements of the vertical displacements between the individual segments (piston errors). Because of such mirrors to exhibit diffraction-limited performance, a phasing process is required in order to guarantee that the segments have to be positioned with an accuracy of a fraction of a wavelength of the incoming light.The measurements become especially complicated when the piston error is in order of wavelength fractions. To meet the performance capabilities, a novel method for phasing the segmented mirrors optical system is described. The phasing method is based on a high-aperture Michelson interferometer. The use of an interferometric technique allows the measurement of segment misalignment during daytime with high accuracy, which is a major design guideline. The innovation introduced in the optical design of the interferometer is the simultaneous use of both monochromatic and white-light sources that allows the system to measure the piston error with an uncertainty of 6nm in 50µm range. The description about the expected monochromatic and white-light illumination interferograms and the feasibility of the phasing method are presented here.

Based on the analysis of principle of tracking and aiming system, some important factors to design the structure of tracking-aiming system and the layout of optical system are discussed. Besides, the paper gives the present developing situation of fast-steering mirror at home and abroad, analyzes the advantages and disadvantages of FSM with axis, and presents a novel design of flexible axis FSM. The main axis of composite axis system is tracked by motor to drive the frame, and the sub-axis is tracked by voice coil motor (VCM) to drive FSM. The structure of FSM and designing principle of VCM are introduced, and the emulation analyses of inherent frequency and deformation under load of the FSM with software COSMOS are also given.

Sparse aperture optical systems use a reduced aperture area to synthesize optical performance of a filled aperture. The relative arrangement of sub-apertures is a key for the design of sparse aperture. Golay configurations are a series of sparse apertures which are nonredundant configurations and have uniform MTF. A novel sparse aperture configuration named pseudo-Golay6 is proposed, which is also nonredundant configuration. It is based on the analysis of one dimensional array arrangement and array optimization. The relative arrangement of the sub-apertures of pupil is similar with the Golay's. The sub-apertures are arranged on the sides of the equilateral triangle. It has advantage of simple configuration and uniform MTF. The arrangement of the sub-apertures is analyzed, and the MTF is also studied. Image simulation of the pseudo-Golay6 is developed, and it has been compared with the performance of Golay6. The results show that the array of pseudo-Golay6 is nonredundant and has uniform arrangement at the spatial frequency space. The sub-MTFs of pseudo-Golay6 are not overlap except at zero frequency. The cutoff spatial frequency is highest at the direction of ^π₃, the cutoff spatial frequency is lowest at the direction of ^π₆, . The practical effective diameter of pseudo-Golay6 is larger than that of Golay6 ,and the highest cutoff spatial frequency is higher than that of Golay6 with the same fill factor. At each different direction, the sub-MTF arrangement of pseudo-Golay6 is less uniform than that of Golay6.

Aspheric optics are being used more and more widely in modern optical systems, due to their ability of correcting aberrations, enhancing image quality, enlarging the field of view and extending the range of effect, while reducing the weight and volume of the system. With optical technology development, we have more pressing requirement to large-aperture and high-precision aspheric surfaces. The original computer controlled optical surfacing (CCOS) technique cannot meet the challenge of precision and machining efficiency. This problem has been thought highly of by researchers. Aiming at the problem of original polishing process, an optimized method for manufacturing large aspheric surfaces is put forward. Subsurface damage (SSD), full aperture errors and full band of frequency errors are all in control of this method. Lesser SSD depth can be gained by using little hardness tool and small abrasive grains in grinding process. For full aperture errors control, edge effects can be controlled by using smaller tools and amendment model with material removal function. For full band of frequency errors control, low frequency errors can be corrected with the optimized material removal function, while medium-high frequency errors by using uniform removing principle. With this optimized method, the accuracy of a K9 glass paraboloid mirror can reach rms 0.055 waves (where a wave is 0.6328μm) in a short time. The results show that the optimized method can guide large aspheric surface manufacturing effectively.

For the design of a space solar telescope (SST), the large reflect mirror faces to the sun directly, which is in an abominable thermal condition with seriously thermal distortion. In this paper, it sets up the thermal mode and analyzes the temperature field and thermal distortion of the main mirror of SST. Further more, it uses the thermal design software SINDA/G (System Improved Numerical Differencing Analyzer/Gaski) and the finite element analysis software MSC.Patran to set up different models and various temperature distributions of the main mirror. Though comparing with these models, the paraboloid mirror model is confirmed, which becomes a reference to later thermal analysis of the whole SST.

By summarizing the corresponding parameters 0f the driving system of a 4-m Alt-azimuth telescope, some unit techniques like the driving modes and structure, angular position measurement methods in detail. have been analyzed in the paper. A set of primary schemes for astronomical applications, including the altitude axes being driven by 2 DC torque motors, the azimuth by 4 DC torque motors using helical gears, and two pieces of the 27-bit segment tape encoders for each set of axes is proposed. To meet practical engineering needs, the shafting motion parameters are designed and motor elementary parameters are primarily calculated to offer the important references for further study on system driving model and prototype development.

Deformation of ultra thin mirror with very large aperture under external forces is analyzed. A thin plane bend equation ∇⁴w=q(r,θ)/D is employed to describe the deformation process caused by external forces, especially with small bending approximating. Under revolving symmetry condition, the radial coordinate r becomes the only variable of the bend equation. So it can be simplified as a one-dimension problem during calculation process. Finite element analysis (FEA) method is used to find the active support scheme. While the number and position of the external force points are given with suiTable displacement boundary constraint, the deformable curve corresponds to target curve. After optimizing operation the residual error is reasonable to suit optical demand. The result provides numerical basis for mirror deformable modification.

As space technology develops the optical systems with aperture more than 10 meters are needed. Constrained by the system mass and transport ability of launch vehicle, it's impossible to manufacture these optical systems by conventional technology. It is one of the most novel technologies to manufacture large aperture, ultra-lightweight space optical systems by using membrane mirror as the primary mirror. The membrane mirror is made of thin polymer membrane instead of glass, so it is characterized by ultra-lightweight and low cost. Figuring membrane mirror's surface by electrostatic field is one of the most promising methods. This method is based on the elastic mechanics and electrostatic theories. Membrane mirror is deformed by applying electrostatic voltage between membrane and electrodes behind the membrane. A Φ200mm membrane mirror with electrostatic deformation system has been built and this membrane mirror can be pulled from flat mirror to a 17m radius of curvature. It consists of membrane mounting device, electrode pad and high direct current (DC) voltage control system. The deformation of membrane mirror was observed with ZYGO interferometer and the radius of curvature of membrane mirror was measured by Moiré deflectometry.

Large-aperture telescope can be used in surveying battlefield, researching landform, searching object, real-time monitoring, imaging, detecting and identifying spatial targets and so on. A large-aperture telescope for achieving high resolution power is designed to monitor spatial target and image in real time. Real-time monitoring plays an important role in military conflicts. The orbit parameter of object, quantity, geometrical shape parameter and so on can be obtained by detect spatial target. With the development of optical technology, people require larger aperture in optics-electronic (O-E) system. By increasing optical aperture, the ability of collecting light and resolution power in the system can be enhanced. But the support structure of the primary mirror of large-aperture telescope will be a very difficult problem. With the increase of primary mirror aperture, the weight of the primary mirror will become larger than before. The root mean square (rms) of the primary mirror is affected by many factors, such as deadweight, deformation of heat, environment and so on. Due to the primary mirror of telescope is an important component of telescope system. By reducing the weight of primary mirror, precision of the system is ensured. During the designing phase, one can consider the supporting project of the primary mirror synthetically and analyze it roundly according to technical requirement of optical system and the effect factors. The final structural design can be reasonable. In an astronomical telescope, the surface of reflector is an important part for collecting dark radiation of celestial bodies. Its surface shape will have an effect on collecting efficiency of telescope radiant energy directly. So the rms must be very high. Optical system of large aperture, small wavelength and small focus can receive maximal light intensity. For ground-based optical astronomical telescope, the design proposed in the paper can satisfy the requirement of the possible minimum atmosphere seeing at astronomical observatory site and exert the use efficiency of the telescope adequately. So the accuracy of the traditional surface of reflector can assure that 90% of all the light energy can be focused on within the angle diameter range of the minimum atmosphere seeing, then 100% of light energy should be focused on the angle diameter range of minimum atmosphere seeing. Because the rms of mirror is very high, precise surface machining and accurate the support of mirror are very important tasks during designing and manufacturing the telescope. In the paper, various support techniques of a large-aperture telescope primary mirror are discussed and a 3.5 meter telescope system at the Starfire Optical Range (SOR) overviewed simply, which was operated by the Directed Energy Directorate of the Air Force Research Laboratory, Kirtland AFB, NM, USA from the ground-based O-E system for the observations of spatial target. We also analyze Theoretical elastic deformation of the Steward Observatory 2.3 meter mirror is analyzed.

Image-stabilization systems are widely used during astronomical image integration because of their large gain of image quality and relatively simple control system. Probably the simplest system is the one that tilts a mirror to correct angular variations caused by atmospheric fluctuations, vibration tilt of the telescope, or angular errors of internal components. Lightweight (structured) mirrors based on piezoelectric actuators are of important part of these systems. The coating of lightweight (structured) mirrors and the associated support systems involves the prediction of the magnitude and nature of the elastic deformation of mirror surface due to mechanical and thermal residual stress during coating. The clamping ways are firstly analyzed in this paper, and the finite element method of structural analysis makes it possible to include conveniently the deformation and stress of a lightweight mirror in consideration of effects of thermal gradients and mechanical loads during coating. Two models with different clamping ways are set up by using FEA soft. The distribution of deformation and stress of lightweight mirror caused by thermal residual stress is analyzed. The coated lightweight mirror is measured by interferometer and the result shows the calculated and measured results have good compatibility. Based on the results of these studies, we select a better clamping way to coating the lightweight mirror. The lightweight mirror for astronomical telescope intensified with silver has good optical properties, but the silver mirror has the faults of weak adhesion to glass substrate and the mirror is easily corroded by atmospheric pollution. In order to solve this problem, several silver adhesion layers are studied. Due to mutual action of Al2O3 and silver film, the developed Al2O3-based silver intensified mirror has overcome the above faults and achieved good effect. Finally, the coating is measured by making use of spectrometer. The average reflectance of coating is greater than 98% in 400-1500nm range, and the lightweight mirror can satisfy practical requirement.

The reflecting Schmidt plate M_A of LAMOST consists of 24 segmented hexagonal sub-mirrors. Each sub-mirror is 25mm thick and 1.1m in diagonal. There are 34 force actuators on the back of one sub-mirror which need to be controlled to offer precise load to create correct mirror deformation. This paper presents the control method and network configuration of force actuators for one sub-mirror. Master computer running Windows NT operation system and slave controllers running DOS operation system are connected together via Ethernet local area network (ELAN) by means of TCP/IP protocol. Adopting five slave controllers, 34 force actuators are combined into a distributed system. Master computer controls five slave controllers and five slave controllers operate 34 force actuators. Master computer communicates with slave controllers normally, which receives state of each force actuator from slave controllers and sends instructions to slave controllers via Ethernet LAN. Each slave controller operates 8 force actuators to offer correct load. Axial load capacity of force actuator is ±150N (pull and push) with accuracy RMS ≤0.05N. Force sensor is used as close-loop feedback apparatus to detect the micro load of the actuator.

The superior mechanical and thermal properties of continuous graphite fiber reinforced aluminum matrix composite (C_f/Al) make it attractive from a design standpoint for space-based system for which the lightweight, high stiffness structure is one of the key technologies. This paper describes the development process of a C_f/Al lens barrel used in space infrared optical system including fabrication technology, structure design and simulation analysis. The advantages and disadvantages of C_f/Al lens barrel compared with invar and CFRP lens barrel, whose structure parameters are identical to that of C_f/Al lens barrel, are discussed. Some performance figures and data are given. The results indicate that the performance of C_f/Al lens barrel is significantly better than the invar, and close to CFRP. However lower outgassing than CFRP under the vacuum condition make C_f/Al become a better choice for space infrared applications.

Large astronomical optical telescopes are badly needed in order to learn more remote universe. There exist some key problems of the control systems of large astronomical optical telescopes. Since they have voluminous bodies that would encounter heavy external disturbance, one of the key problems is focused on how to accurately control them. Additionally, in order to get nicer ultra-low velocity performance and a steady field of view, friction drive is widely applied in contemporary large optical telescopes. One serious disadvantage of friction drive is that it will cause some nonlinear uncertainties to influence telescope controls because of the mechanical characteristics between the principal and subordinate friction wheels. These two aspects of external and internal disturbances will make a telescope very difficult to be controlled. In this paper, we introduce a method of higher order sliding modes (HOSM) to control telescopes, which overcome these two disadvantages of traditional Proportional-Integral-Derivative approach and can achieve excellent control performance. Conventional sliding mode approach has been applied in many other mechanical control systems owing to its high accuracy in anti-jamming. By discontinuous switching, it is invariable to disturbances based on keeping some constraints with a sufficiently energetic effort. However, such conventional sliding mode approach may cause dangerous high-frequency vibrations in the corresponding control system, which may influence systemic control performance or even lead the system unstable. In this work, we use the newly developed HOSM approach in the control systems of the large astronomical optical telescopes. The HOSM approach inherits the dominant merits of conventional sliding mode. Moreover, it acts on the higher order time derivatives of the system deviation from the constraint. And the discontinuous dynamics are restricted to the highest state while the counterpart in standard sliding mode is in first derivative. Thus the HOSM approach can mostly removes high-frequency vibration effects on telescope control. This control approach needs all states of the system to be observable. We use robust exact differentiator to estimate the immeasurable state. Simulations have been done in the environment of MATLAB language. The results show that this approach can realize the tracking performance of accurate ultra-low velocity for telescope control.

The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) project is one of the National Major Scientific Projects undertaken by the Chinese Academy of Science. There are 16 low resolution multipurpose fiber-fed spectrographs in total, enabling it to obtain the spectrum of celestial objects as faint as down to 20.5. Building auto-focusing systems for the spectrographs is important due to the popularity of instruments. The system enables the optical system to automatically compensate changes in accordance to external variables, such as temperature, timidity, to ensure the spectrum collected more reliably. Image-based algorithm is utilized to calculate the departure of CCD plane from optical focal plane. The calculation also aids to regulation of the system. The defocus value is transformed to the controlling computer of each spectrograph. A driving step-motor performs refocusing function by moving the fiber slit unit to its right position.

We report progress in the development of deformable mirrors (DM) using nanocomposite materials. For the extremely large telescopes (ELTs) currently being planned, a new generation of DMs with unprecedented performance is a critical path item. The DMs need to have large apertures (meters), continuous surfaces, and low microroughness. Most importantly, they must have excellent static optical figures and yet be sufficiently thin (1-2 mm) and flexible to function with small, low powered actuators. Carbon fiber reinforced plastics (CFRP) have the potential to fulfill these requirements. However, CFRP mirrors made using direct optical replication have encountered a number of problems. Firstly, it is difficult if not impossible for a CFRP mirror to maintain a good static optical figure if a small number of plies are used, but adding more plies to the laminate tends to make the substrate too thick and stiff. Secondly, direct optical replication requires precision mandrels, the costs of which become prohibitive at multi-meter apertures. We report development of a new approach. By using a combination of a novel support structure, selected fibers, and binding resins infused with nanoparticles, it is possible to make millimeter thick optical mirrors that can both maintain good static optical figures and yet still have the required flexibility for actuation. Development and refinement of a non-contact, deterministic process of fine figuring permits generation of accurate optical surfaces without the need for precision optical mandrels. We present data from tests that have been carried out to demonstrate these new processes. A number of flat DMs have been fabricated, as well as concave and convex DMs in spherical, parabolic, and other forms.

Large-scale mirror plays an important role in the field of science and technology. Just because of shortcomings of traditional materials, silicon carbide is tending to be the most potential material for large-scale mirror. Large-scale mirror is fabricated by three steps. The first step includes design and analysis of mirror. The second step is the preparation of mirror. The third step is machining, polishing and coatings. Some mirrors with sizes from 100 mm to 1m were prepared. The roughness is less than 3 nm rms. The wave-front error can be less than 1/40 wavelength rms. The reflectivity of the mirrors with Ag films is larger than 95%. In order to obtain smoother surface, a dense coatings with single phase material should be prepared. In this paper, silicon coatings were prepared by electronic beam physical vapor deposition and magnetron sputtering. The properties of coatings-substrate system were tested. The adherence strength of silicon coatings by electronic beam physical vapor deposition is between 15~20 g, and porosity is about 6%, and the adherence strength of silicon coatings by magnetron sputtering is between 20~40 g, and porosity is less than 2%. The silicon coatings by magnetron sputtering can be polished to a smooth surface. Some silicon carbide mirrors were prepared for the large pointer mirror and the primary mirror of the high resolution camera. Currently, experiments are under way to test the properties under the simulation space situation.

The Smart X-ray Optics project is a UK based consortium consisting of several institutions to investigate the application of active/adaptive optics upon both small and large scale grazing incidence x-ray optics. The work done at University College London (UCL) focuses on the application of piezoelectric materials to large scale optics in order to actively deform the mirror's surface. These optics are geared towards the next generation of x-ray telescopes and it is hoped that the project will be able to achieve a resolution greater than that currently available by Chandra (0.5"). One of the aims of the consortium is to produce a working prototype. The initial design is based on a thin nickel ellipsoid segment with an x-ray reflective coating, on the back of which will be bonded a series of piezoelectric actuators. Investigation into the specification of the design of an active x-ray optic prototype and suitable support test structure has been undertaken. The dimensions and constraints upon the prototype, and the manufacturing process to produce a nickel shell are discussed. Finite element analysis (FEA) of the physical characteristics of piezoelectric materials has shown the ability to deform the nickel surface to correct for errors of several microns. FEA has also been utilised in the specification of the prototype's support structure to ensure that gravitational sag upon the optic is kept to a minimum. Laboratory experiments have tested a series of materials, different actuators and bonding methods, which could then be applied to the prototype.

Based on the principle of holography, a holographic experimental system for the correction of an aberrated optical imaging system with a low quality glass spherical mirror in diameter of 200mm is set up in this paper. An image hologram of the aberration mirror is recorded and reconstructed by the wave with the same wavelength as in recording from a distant object. By testing the interferogram of the reconstructed reference beam and the original reference beam and comparing the images of a pin-hole in diameter of 25μm before and after correction, the effect of correction is analyzed. The experimental results show that with the image hologram in the optical imaging system, almost all the aberrations of the spherical mirror and the optical imaging system can be corrected and near diffraction-limited performance can be obtained.

With the development of the resolution of spaceborne remote sensor, the diameter of the primary mirror of spaceborne telescope becomes larger and larger. The distortion of primary mirror which is influenced by the mirror material, structure, self-weight, support system and temperature environment affects optical image quality finally. In this paper, an on-axis TMA high-resolution Cassegrain optical payload with a primary mirror whose diameter is φ 650mm was designed and the effects of the influence factors of the distortion acts on the on-axis TMA optical system primary mirror had been analyzed by means of Finite Element Analysis. During work, the technology of the primary mirror design had been summarized and general consideration of the primary mirror design technology also had been described at the same time. Considering the telescope manufacture and work station, a reasonable and optimal structure of the primary mirror sub-assembly is taken finally. In the end, the distortion of the primary mirror during its fabrication station and work station had been analyzed by integrated Finite Element Analysis Method. The results implicated the synthesis profile error (P-V value) for the primary mirror is less than λ/10 and all the indexes of the primary mirror satisfy the requirements of the optical system.

In the field of manufacturing large aperture aspheric mirrors, mid-frequency surface error has been considered to be one of the most important factors for both manufacturing and testing technique. Mid-frequency surface error controlling the polishing process is not conventionally concerned as the same of controlling of low-frequency surface error. In order to solve such a problem, a new method-Multi-mode Combined Manufacturing (MCM) is put forward. MCM technology is useful for the control on all frequency-bands errors of optical surface and is adaptive to fast aspheric mirror especially. Based on classical manufacturing theory, principle analysis of MCM and experiments results are discussed in the paper.