On October 28, 2022, China ZKCC Optical Mechanical Systems Technology Corporation issued an announcement:
After nearly 20 years of technical research, the company's research team has overcome the core key technologies such as the preparation of large diameter silicon carbide mirror blanks, processing technology, detection methods, and modified coating;
It has broken through the advanced manufacturing technology of silicon carbide optical mirrors with high structural stiffness and complex surfaces;
A full link integrated manufacturing system of φ 4m large aperture SiC aspheric mirrors has been established, and Ultraprecision manufacturing of the world's largest aperture SiC aspheric mirrors has been completed.
The optical manufacturing technology applied to high-performance imaging has put forward strict requirements on the material, aperture, surface type, surface error, surface roughness, etc. of the reflector, and has brought many serious challenges:
1. The preparation process of silicon carbide mirror blank is accompanied by complex physical phase transformation and chemical reaction. The existing international process is difficult to break through the 2m level. The preparation process and equipment of silicon carbide mirror blank with a diameter of more than ⌀ 2.5m for visible light band applications are still international blank;
2. In the world, CVD technology is generally used to modify the surface of large-diameter silicon carbide aspherical surfaces. Usually, the substrate needs to be heated to more than 600 ℃. The resulting large temperature gradient is easy to cause irreversible deformation of the mirror;
3. The manufacturing difficulty of the aspheric mirror is proportional to the cubic of the aperture. Silicon carbide is one of the four hardest inorganic materials known. Conventional means and processes make it difficult to process and have low convergence efficiency. The final surface shape detection accuracy is also restricted by the dynamic range of the instrument, air flow disturbance and other factors.
Faced with severe challenges, ZKCC has put forward a set of solutions after years of technical research:
1. Aiming at the problem of large internal stress in the preparation process of silicon carbide mirror blank, which is difficult to break through 2m due to the limitation of shrinkage ratio, the technical problems such as semi closed ultra lightweight plain blank forming, drying without macro cracks, and homogeneous microstructure connection were solved, and the preparation of φ 4m silicon carbide lightweight mirror blank was completed;
2. Aiming at the problems of poor precision and low efficiency in conventional manufacturing of large diameter silicon carbide aspheric surfaces, high temperature of CVD modification technology, large stress and deformation, etc., the technology of efficient and high-precision convergence combined processing was proposed, and the optical manufacturing software platform SLAM was developed. The convergence efficiency of full frequency surface error was increased by 30%, and the high-precision deterministic manufacturing of ⌀ 4m silicon carbide aspheric mirrors was completed;
3. Aiming at the problems such as low dynamic range of ⌀ 4m aspheric surface shape detection means and airflow disturbance in long optical path detection, a cross scale/multi method combined detection technology for large aperture aspheric surface shape error is proposed, which realizes high-precision detection of φ 4m reflector surface surface topography error.
After years of technological innovation and accumulation, ZKCC has broken through the preparation technology of large caliber lightweight silicon carbide materials, the processing and detection technology of large caliber silicon carbide aspheric surfaces, and the modified coating technology of large caliber silicon carbide, and completed the high-precision manufacturing of ⌀ 4m silicon carbide mirrors.
It has broken the monopoly position of foreign countries in the manufacturing technology of large-diameter aspheric surfaces, formed the development capability of φ 4m large aperture mirrors with independent intellectual property rights, filled a number of domestic gaps, and greatly improved the development level of high-performance large-scale optical instruments in China.
The SiC aspherical mirror with the largest caliber in the world has been applied in astronomical observation and other fields.