Residual stress is an important performance indicator of optics, which is of great significance to the fa-brications and applications of optical components. Residual stress measurement methods of optics can be summed up into two categories: methods based on the strain measurement and on the stress induced birefringence mea-surement, respectively. The strain based methods, which are built upon crystal dynamics and elastic mechanics, in-cluding X-ray diffraction (XRD), Stoney curvature method, and micro-Raman spectroscopic method, are well devel-oped and widely used. Methods based on the measurements of birefringence phase retardation induced by residual stress, including digital photoelasticity method, photoelasticitic modulator (PEM) method and polarization-dependent cavity ring-down method, show a higher precision. The principles, measurement precisions and application scena-rios of these residual stress measurement methods are summarized in this overview. Comparisons between the performances of these methods are performed and correlations between them are analyzed in detail.

With the space technologies progress rapidly, demand of large-size mirrors is intensively growing. In this paper, the developing trend of large-size space mirrors was discussed from the angles of material and fabrication technology. Taking 1.0 m aperture technical validation brazed mirror as an example, the design and fabrication of segments, joining and optic machining were analyzed. In addition, the 1.0 m aperture technical validation brazed mirror was performed environmental tests including thermal-vacuum test, vibration test and anti-radiation test in order to evaluate its engineering applicability. The experimental results show that the surface figure of the 1.0 m aperture technical validation brazed mirror changed from 0.038λ (λ=632.8 nm) to 0.037λ and 0.036λ after thermo-vacuum test and vibration test. Additionally, reflectivity of the brazed mirror basically kept stable after 60Co γ-ray radiation test, indicating a brilliant application prospect.

The construction of high-power solid-state laser facility for inertial confinement fusion requires to precisely control the full-spatial frequency error, and realize efficient mass-manufacturing of large-aperture optics. This review summarizes the recent critical progress in manufacturing of large-aperture optics in high-power laser facility. It also emphasizes the technologies such as single point diamond fly-cutting, and aspheric ultra-precision grinding, as well as deterministic polishing, based on the deterministic ultra-precision process manufacturing method. In addition, the application status of these key technologies in the mass-manufacturing chain was stated specifically.

Due to the unique advantages of complex curved aluminum mirrors, its application in optical systems is becoming more and more widespread. However, the accuracy of optical mirrors that are only processed by ul-tra-precision turning is limited by the "error reflection" of ultra-precision turning, which can only meet the application requirements of infrared systems, and its further promotion and application have encountered bottlenecks. The combined processing technology of ultra-precision turning, magnetorheological polishing, and computer-controlled surface forming (CCOS), combined with the computational hologram method (CGH) of the complex optical curved surface (CGH) surface shape detection technology, can further improve the surface shape accuracy of the aluminum reflector, to meet the application requirements of visible light systems, and lay the foundation for the promotion and application of complex curved aluminum alloy mirrors.

This article reviews on the fabrication advancement of X-ray reflect mirror fabrication in terms of technical requirements, fabrication and metrology development. Synchrotron radiation source, as a revolutionary light source, provides one of the most high-performance X-ray for scientific research, where reflect mirror plays an essential role in X-ray beam focusing. The short wavelength of X-ray demands reflecting photons only at a grazing angle of inci-dence on the extremely high-precision and smooth surface. Fabrication of such mirrors requires highly specialized equipment and technology that only a few foreign optic manufacturers possess, whereas manufacturers in China is laggard in this area. It is imperative to develop fabrication capability domestically as two synchrotron radiation facili-ties are under construction and several more projects are about to launch in the near future in China.

With the continuous development of modern optics, such as EUV, DUV lithography and the advanced light source, the surface interferometric measurement with higher accuracy has become an important challenge. The surface accuracy as one of key technical parameters will be required to nanometer, sub-nanometer, even picometer. The surface interferometric measurement with higher accuracy push the limits of surface metrology, has important research significance and application value. This paper analyzes the development trends of surface interferometric measurement with higher accuracy and reports the related research progress of Institute of Optics and Electronics, Chinese Academy of Sciences.

The fabrication of optical elements with microstructural arrays has attracted more and more attention. Single-point diamond flying cutting technology has been gradually applied to the fabrication of microstructures with the advantages of high efficiency, low cost and high machining accuracy. This paper mainly studies the influence of repeated positioning errors of machine tools and errors introduced by cyclic machining on micro-structure turning effect when flying cutter turning micro-pyramid structure, analyses the conditions of secondary groove generation in V-groove turning, studies the methods of restraining secondary groove generation, and finally verifies through expe-riments that the generation of secondary groove can be restrained by controlling the turning depth greater than the minimum turning depth.

Stressed polishing technology transforms aspheric fabrication into spherical fabrication by applying pre-determined loads on the surface of the mirror. The key to achieve high precision of stressed polishing is to test the surface deformation with high precision. Stereoscopic phase measuring deflectometry was used to test the surface topography and the deformation of stressed mirror. After obtained unwrapped phase distribution, and combined with normal consistency constraint and gradient integral algorithm, the height distribution was finally obtained. Composi-tion of systematic errors were simulated. Also, the errors were calibrated and removed by N-step averaging method in this system, which improved the measuring precision. In this paper, the surface topography and the deformation of a stressed mirror with a diameter of 320 mm, spherical radius of 5200 mm were measured. The measuring results were consistent with the corresponding result of CMM and finite element simulation, indicating that this proposed method is on the level of micron in terms of accuracy and more suitable for the test of stressed mirror compared with interferometer and CMM.

Passive hydraulic support units (PHSUs) are frequently used in the in-situ fabrication and testing (in-situ support). However, the difference in PHSUs’ stiffness will affect the mirror surface figure, especially for those thin meniscus mirrors. In order to solve this problem, the joint optimization method of layout, stiffness and active correction is studied. Firstly, for the difference of PHUS' stiffness, a hierarchical layout optimization method for support stiffness and support position is proposed to obtain the initial optimization solution of the support system. Then, the mode calibration method and the least square method is used for active correction of support system to obtain the final optimized solution of the mirror surface figure. Finally, the effectiveness of the method is verified by a numerical simulation experiment with specific cases. The results show that, for 4 m thin meniscus mirror, after layout optimization, with the hydraulic passive support system, the root mean square (RMS) of the mirror surface errors of 60 point axial support system is reduced from 150.6 nm to 32.9 nm, and the RMS value of the mirror surface errors of 78 point axial support system is reduced from 45.2 nm to 22.6 nm. The optimization effect is remarkable. After active correction, the RMS value of the mirror surface errors of 60 point axial support system is 14.6 nm, and it is 6.9 nm for 78 point axial support system. The requirement of the RMS value of the mirror surface error is less than λ/40 (λ=632.8 nm). The support systems meet the requirement. Finally, the 60 point axial support system was selected. Through the joint optimization of layout, stiffness and active correction for supporting points, it can greatly increase the applicability, flexibility and reduce the difficulty of implementation for the in-situ support system.

The in-situ measurement of complex optical surfaces is a challenging task in precision engineering. The phase measuring deflectometry is a powerful measuring method for complex specular surfaces, and it has higher measuring efficiency, stability and dynamic range compared to interferometry. Consequently it is promising to wide-spread applications in various fields. Deflectometry is essentially a calibration problem, and the measuring accuracy is directly determined by the quality of geometrical calibration. An in-situ deflectometric measuring system is de-signed based on the single point diamond turning machine. A self-calibration method is developed to specify the relative positions of the camera and screen. Ray tracing is conducted at two positions of an auxiliary reflecting mirror, which is mounted on an air bearing spindle. The accuracy of the geometrical positions can be improved by an order of magnitude by minimizing the deviations of the traced points with respect to the true correspondences. According to the statistical properties of the deviations in reverse ray tracing, the form errors and the position errors can be separated, and the positioning error of the workpiece can be corrected accordingly. Henceforth, the nominal shape of the fabricated workpiece can be fully utilized, and the conventional one-way position-form mapping can be converted into a two-way mapping problem. As for the complex shapes, the whole surface can be covered by sub-aperture measurement. Precise localization of a local region under test is achieved by multi-position imaging, so that correct convergence of the iterative reconstruction process can be guaranteed. Several typical optical surfaces including an off-axis paraboloid mirror are measured, and the measuring accuracy of the proposed method is proved better than 150 nm RMS.

In order to solve the problem that the mass and the surface figure accuracy of the space reflective mirror are often contradictory in the lightweight design process, a structural optimization design of a lightweight rectangular reflective mirror of an off-axis three-reflection optical system is performed. In this study, a lightweight structure based on the center support of SiC materials is proposed. At the same time, a multi-objective optimization method is in-troduced. With the RMS value and Mass as the optimization targets at the same time, a mirror optimal structure model is obtained with a mass of 2.32 kg. Compared with the solid mirror, the lightweight ratio is 73.8%. Then the mirror subassembly is designed and the integrated performance of it is simulated. It shows that the RMS value of the mirror reaches respectively 2.5 nm, 2.2 nm and 7.3 nm when gravity load is applied in the directions of X, Y and Z axes. Furthermore, the RMS value is 3.2 nm when the mirror subassembly is under the load condition of uniform temperature rise of 4 ℃, which is far less than the requirement of RMS≤λ/50(λ=632.8 nm). Therefore the data meets the design requirements.