| Large aperture aspheric optics have advantages in improving the performance of optical system and are used more and more widely in modern optical systems, due to their ability of correcting aberration, enhancing the image quality and enlarging the field of view , while reducing the weight and volume of the system. With the application of telescopes, spy camera and high-energy laser weapons at outer space, large aperture space aspheric optics with the characteristic of high light-weighted, high stiffness and high stability are demanded ever-increasing. However, this kind of optical mirror are hard to fabricate, and the main obstacle is metrology technique. The major research tasks are to solve the problems during testing and obtain high repetition, high precision testing results. In this dissertation the research efforts include these key questions: the measurement method of surface figure, support deformation during installing, inefficient and low precision alignment. The main contents are as follows:1. According to analyze the spherical aberration of aspherical mirror and the third order aberration theory, original constructional parameters can be calculated. Computer optimization design constructional parameters and tolerance analysis are presented through the optical design software. The rationality, machining and assembly performance of design results are validated.2. Analyzing the installing characteristic of large aperture mirror, and scheme design of large aperture mirror installing equipment is performed. Finite element analysis software is adopted to simulate in different working circumstance and typical support configuration. The results show that support deformation is very large on condition of optical axis-vertical setup and it can not satisfied with testing precision; and the lever and hammer support method can get small support deformation on condition of optical axis- horizontal setup. The concept of sensitivity of support deformation is brought forward. Since the simulation precision is hard to achieve in the support method of high sensitivity, the support method of low sensitivity should be priority.3. The computer-aided alignment technique is used to adjust the optical path of compensator testing system and adjusting software is accomplished according to the mathematical model. The correctness of the aided adjusting software is testified according to the numerical simulation of coaxial mirror testing system and abaxial mirror testing system. The compensatory relation of different adjusting variable is studied, the results show that five degrees of freedom of compensator can be used only to obtain high accuracy installing of testing optical path on condition of small misalignment. It can minish the number of adjusting variable, solve the trouble of high accuracy installing of mirror with large aperture and large weight, reduce the actualization difficulty of installing.4. Taking paraboloidal mirror with 750mm aperture for example, compensation testing and support deformation are analyzed. Which flat reference wavefront and sphere reference wavefront are checkouted reciprocally can improve the dependability of testing result. The reason of installing deformation is analyzed according to comparing with the simulation results and testing results, and used to instruct and improve installing method. Novel support method of backboard support is brought forward. It weakens the support deformation, improves testing precision and testing repeatability. The repeatability of surface figure in different angles reaches to nanometer scale. |
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