Key Technology On Ultra-precision Grinding Of Infrared Aspheric Lens

Infrared aspheric lens are key components of infrared imagery and guidance system, which are used to transfer, refract the incoming light in optical components. Especially, aspheric lens have many advantages in terms of optical system optimization, spherical aberration and optical aberrations reduction of spherical lens in the collimating and refocusing optics system, quantity of optical components decreasing, weight decreasing, size reducing and integration realization. Therefore, aspheric infrared lens have important and extensive application perspectives in aerospace, electrical, building, medicine, automotive, and so on. At present, the main method for mass production of aspheric infrared lens is by means of traditional abrasive polishing with low efficiency and poor product uniformity. While the ultra-precision grinding with high efficiency and technological stabilization, good product uniformity is the novel key technology for hard and brittle materials.The research purpose is the deterministic, ultraprecision, low damage and high efficiency machining of silicon for spherical surfaces with diameter of 150 mm and multispectral CVD zinc sulfide for aspheric surfaces with diameter of 93.5mm. The research contents are as follows:Based on the physical property of material, as well as the structure and dimensions, the appropriate grinding methods of aspheric surfaces were chosen from the present grinding methods. And then, contact arc length between wheel and workpiece, maximum undeformed chip thickness, scallop-height and errors was analyzed in the chosen methods. At last, the grinding method was confirmed by ways of combining theory and experiment. The results showed that the variation of contact arc length, maximum undeformed chip thickness, scallop-height and the effect of errors on surfaces was smaller, and the better surface was obtained in cross grinding than parallel grindingThe truing of abrasive tools plays an important role in grinding process. Therefore, two universal truing methods of arc-shaped diamond wheel were presented for coarse grinding and fine grinding aspheric surfaces. In oreder to inhance truing accuracy, the impacts of errors caused by institutions, control, environmental and operater on the truing profile accuracy of the diamond wheel and the corresponding solution were provided. Moreover, the effects of truing parameters on truing accuracy were achieved by experiments, and then the truing process was optimized. After truing, the form accuracy of arc-shaped profile was improved and the run error was decreased.A suppression method of grinding marks was proposed by optimizing combination of grinding parameters. Moreover, the properties of grinding wheel was chosen by grinding experiment. The influences of grinding parameters on ground surface quality were studied. And then, the optimization parameters were achieved. At last, the purposed aspheric surfaces were ground, the form acuuracy of surfaces is about PV: 0.5μm, the roughness Ra is below 5nm.The acoustic emission signal acquisition system was developed for monitoring truing and grinding process based of rotary acoustic emission sensor. The end time of truing could be judged by the threshold of acoustic emission RMS signal. The effect of grinding parameters and on acoustic emission signal and the impact of acoustic emission signal on surface quality was studied to provide technical support for monitoring grinding sperhical and aspheric lens.