The CNEPO has achieved a comprehensive breakthrough in some key technologies such as surface figure accuracy assurance of component coating with extremely high precision, preparation of low-loss deep ultraviolet optical coatings, control of coating thickness uniformities on large curved surfaces, IBS (ion beam sputtering) coating at room temperature for fine polishing components,evaluation of service life of long-term laser irradiation, etc. Some critical performance indicators have reached or exceeded the best results reported internationally, such as the double-sided transmittance of T = 99.8 % @ 193 nm, and the surface figure accuracy of below 0.1 nm after coating. 

Figure 1: Statistical results of surface figure accuracies of elements of NA0.75 projection objective lens after coating

Figure 2: The radial uniformity of optical performance on curved surfaces is achieved by optimizing the coating process