|
You have it the wrong way round. The piece on top becomes concave (the mirror) the piece below becomes convex(the tool).
The edges do all the cutting, so the tool and mirror must move longitudinally and transversely across the surface. Otherwise you won't get a spherical surface.
You need the movement to generate the sphere. The length of the strokes needs to be varied in both axes. Mechanical mirror grinding and polishing machines have the ability to vary the stroke pattern, length and width. If the length and width of stroke is not regularly varied, concentric rings are ground into the surface.
You are thinking like a machinist not an optician. As I mentioned before, the most precise machining is 1000x too coarse for optical surface figures. You can machine out the very rough figures for mirror and tool but then you need to go conventionally
|