Study On Precision Grinding And Form Error Compensation Grinding Of F-theta Freeform Surface On Optical Glass

Freeform surface optical components are more conducive to integration of optical systems compared with spherical and aspheric optical components. Due to heat accumulation of integrated optical systems produces a higher temperature, so the optical glass is used as lens material because of its high temperature resistant, corrosion resistance and small thermal deformation. However, the optical glass is easy to produce micro cracks in the machining so that machining accuracy is damaged. Diamond grinding wheel has already been applied to precision grinding the axisymmetric aspheric optical components because of its excellent cutting performance and good wear resistance, but it has not been applied to machine non axisymmetric freeform surface optical components because it is difficult to generate tool path.Therefore, an elliptical torus diamond grinding wheel is applied to precision grinding freeform surface optical components by controlling the tangent point of grinding wheel and workpiece surface in the three-axis CNC grinding. Precision grinding of form error compensation is proposed to reduce the comprehensive error, such as form-truing error of grinding wheel, mechanical error, and design errors. First, F-theta lens in the laser printer is used as freeform surface optical components design in this paper. Then, an orthogonal experimental which is used to study the process parameters of precision truing of elliptical torus grinding wheel is employed. Finally, a normal-form algorithm that is used to generate 3D tool path is established. Also, the research includes how form-truing error compensation of grinding wheel, vertical form error and normal form error compensation of freeform surface and process parameters of CNC grinding influence form accuracy and surface quality of F-theta lens in laser printer. The specific research results are as follows:1、The initial structure of F-theta lens in laser printer is designed with reference to the existed F-theta lens in the optical system, and it is optimized by optical software ZEMAX to meet the design requirements.2、The form-truing error of grinding wheel is mainly influenced by wheel speed, the thicker GC tool can improve the truing accuracy, and its truing accuracy of less than 29.6 μm can been obtained by under appropriate truing conditions.3、The form-truing error compensation of grinding wheel can decrease the form error by 55% in precision grinding of F-theta lens without the secondary processing. Also, vertical form error and normal form error compensation can decrease the form error by 62% and 64%, respectively.4、The roughness of optical glass is mainly influenced by feed speed, and the roughness of mirror freeform surface optical ground is 44.7 nm without polishing by under appropriate process conditions.Comprehensive the above, the grinding of F-theta lens can realized by using the elliptical torus diamond grinding wheel and the normal-form algorithm. The form-truing error compensation of grinding wheel and form error compensation of freeform surface can used to achieve high precision machining of F-theta lens. Besides, an elliptical torus-shaped #3000 diamond grinding wheel can used to mirror grind of freeform surface optical components.