Study Of Variable Curvature Mirrors Technology For Optical Zoom Without Macroscopic Moving Elements

Optical zoom without macroscopic moving elements means the process which can realize optical zoom without the components having macroscopic movement in optical system. As a new type of optical zoom technology, the elimination of macroscopic movement components make it can be used to fields having rigorous requirements on space, power consumption, stability, and also can increase the timeliness of zoom. So, optical zoom without macroscopic moving elements can greatly expand the application range of zoom technology. At present, the United States of America, Germany, France and China have carried out the study applying this zoom technology to telescope and mobile devices zoom imaging, etc.Variable curvature mirror, active optical components which can change itself’ s radius of curvature, is the key to achieve optical zoom without macroscopic moving elements. In specific occasion, for example, in small scale verify systems, commercial deformable mirror can be used as the replacement of variable curvature mirror. However, to solve the problem of complex control caused by multi-points actuation deformable mirror, simplified variable curvature mirror having easy mechanism, functions easy to realize becomes a new study branch. This paper centers on the study work of variable curvature mirror, mainly consists of the following four sections:Section 1 give a systematic introduction of optical zoom technology without macroscopic moving elements and variable curvature mirror’s current research situation and development tendency. Based on this, we get the difficulties of variable curvature mirror technology, background of carrying out the study and technical parameters mean to get.Section 2 based on Roark’s formulas for stress and strain, firstly, give an introduction of variable curvature mirror’s uniform annular line load model under simply support. Secondly, compare and analyze the two models--central point actuation and multi-points actuation, which can realize the actuation mechanism of annular line load. Meanwhile, using’maximum center deflection under minimum actuate force’as the evaluation standard, we get the optimum position of actuate ring, and analyze the control ability to surface shape precision of multi-points actuation after the annular line load deflection. Finally, we decide the key parameters of variable curvature mirror by comparing the influence of different material, different thickness to center deflection and the requirement to ability of actuator.Section 3 first gives the structure design of variable curvature mirror, then carry on finite element analysis using specific software under nearly realistic condition. The analysis results indicate that the constructed model in this paper both can realize quite big centre deflection corresponding to the change of radius of curvature and can guarantee the safety of mirror and its structure.Section 4 give the detail description of prototype mirror and opto-mechanical structure’s fabrication, actuators’choose and test, experimental platform’s construction and the whole system’s experimental test. Then analyzes the experiment data and find the problems of structure design in the experiment process. Based on this, gives the improvement of the variable curvature mirror’s opto-mechanical structure. The test results demonstrate that beryllium bronze variable curvature mirror with 100mm aperture,3mm thickness can realize centre deflection more than 30 waves, reach the expected target.