The optical manufacturer normally
purchases bulk optical glass in a form identified as a strip. The optical
manufacture companies are with a very predictable &reliable
product and provide us with thorough information about the optical &
mechanical properties of any glass that we purchase. A blank for the spherical
lens will be one disc with a flat top and bottom. A blank for cylindrical
lenses will be with a rectangular cross-section. The bar is made into multiple
identical components.
The Components with a constant radius of curvature can be produced through all means in generating, grinding, and polishing. Alternatively, the components can be made using two steps: generating and polishing, which among them accomplish the grinding function. For components with a non-constant radius, the two-step method is used.
When a lens is not being produced
through equipment, it is common to use finer liquid abrasive slurry solutions
to slowly make the glass surface somewhat smooth. The appearance of the glass
surface fluctuates as the texture gets fine but the surface is still noticeably
gray, after grinding.
The grinding processes
The grinding does not change the curving
of the lens exterior. Grinding makes the lens slightly thinner, which is why
the preceding generating step leaves a little extra thickness. Grinding is a
faster process, usually requiring only fewer minutes per surface. Grinding uses
a rotary table with a physically operated swing arm to position the grinding
tool contrary to the lens surface. The Polishing process uses liquid abrasive
slurry to smooth the frosted glass texture until the surface is smooth and
transparent. The polishing pad in a polisher is made from a material that looks
like a fine mesh sponge or a coarse cloth. The polishing pad is made from the pitch
that is scored to let the liquid abrasive slurry infiltrate between the pitch &
the glass surface.