Full aperture polishing is a significant process to fabricate optical workpieces with nano figure precision. It has the characteristics of excellent full spectrum uniform removal ability, fast convergence speed, high machining accuracy, and low production cost, which makes it the first choice for the processing of large-aperture optical elements. However, with BK7 glass it is difficult to achieve deterministic processing due to its large thermal expansion coefficient and other factors, and the surface shape accuracy is difficult to improve. In this paper, the thermal deformation of BK7 glass is analyzed first, and then the temperature distribution in the element is measured during full-aperture polishing. The influence of the temperature field in the optics on the accuracy of the final surface shape is analyzed, and the quantitative relationship between the temperature difference and the surface shape is established. In addition, the methods of deterministically controlling the surface shape of optics such as polishing liquid temperature control and immersion polishing are proposed. Finally, the model of quantitative control of the surface shape of optics is verified by experiments, which improve the surface shape accuracy of 600 mm BK7 optics to 0.2 λ .

Continuous polishing is the first choice for machining optical elements with a large aperture. The lubrication in the continuous polishing is an important factor affecting the surface quality of the optical elements. In this study, the lubrication system between the optic element and polishing lap was analyzed firstly and then was verified by the measurement experiment of the friction coefficient. In addition, the numerical simulation model of the mixture lubrication was established. The polishing pressure distribution and material removal distribution can be obtained by the model. The influences of the rotating speed, optical element load, and surface roughness of the polishing lap on polishing pressure were also analyzed. Finally, the influence rules of the lubrication on the surface shape of optical elements were revealed by the polishing experiments.

High-precision freeform surfaces are widely used in ultra-precision optical systems to improve imaging performance and reduce optical system weight. With the development of short wavelength optics represented by extreme ultraviolet lithography, the high-precision requirements for the full frequency errors and geometrical complexity of optical freeform surfaces pose great challenges to optical processing and are difficult to achieve by traditional manufacturing processes. This paper proposes a cross-scale surface shape error correction method to correct surface shape errors in different cycles in bonnet polishing. First, the material removal mechanism based on physical and chemical effects was discussed to obtain the method of cross-scale removal functions. Secondly, the analysis method of the frequency response characteristics of the tool based on power spectral density was discussed to analyze, evaluate, and guide the bonnet polishing process of freeform surfaces. Finally, the proposed method was verified by the experiments in processing a fused silica freeform surface of 120 mm diameter; the final root-mean-square (RMS) of surface shape accuracy was better than λ/100.

Large flat transmission mirrors made from optical glass BK7 are widely used in the high-power laser facility, which are required of stringent specifications for the whole spatial frequency errors. This work reveals the role of pad block’s support surface (PBSS) topography in measuring BK7 surface figure. Firstly, the PBSS topography was measured with laser displacement sensor. Secondly, the BK7 surface deformation at different pad blocks were simulated with finite element method and validated by experiments. Finally, a method was proposed to quantitively evaluate the different PBSS topography.