Abstract:

Due to the processing difficulties of optical glass F-Theta freeform surface lens, the form error compensation and the mirror grinding processes of freeform surface using an elliptical grinding wheel instead of the arc one are proposed. The F-Theta freeform surface lens is designed by equation, and a normal algorithm model for planning tool paths of freeform grinding is proposed. Second, the form error compensation is employed to grinding F-Theta freeform surface lens with an elliptical torus-shaped #46 diamond grinding wheel, which includes the vertical from error and normal form error compensation. An elliptical torus-shaped #3000 diamond grinding wheel is employed to grind F-Theta freeform surface lens to study the mirror grinding process. Experimental results show that the vertical form errorsE_y and PV of F-Theta freeform surface lens are decreased by 45.9% and 11.6% after traditional vertical form errors compensation, respectively; The normal form errorsE_n and PV of F-Theta freeform surface lens are decreased by 47.9% and 41.5% after the new proposed normal form error compensation, respectively; Besides, The roughness of F-Theta freeform surface lens ground by #3000 diamond grinding wheel is 28 nm, and its mirror grinding process is different from the coarse grinding process. It is confirmed that normal form error compensation may be an efficient method for precision grinding of freeform surface. In addition, the #3000 elliptical torus-shaped diamond grinding wheel can fabricate mirror optical glass freeform surface lens without polishing.

Key words: diamond grinding wheel, error compensation, freeform surface, mirror grinding, precision grinding, F-Theta lens