[rollei_list] Re: changing lens formulas
- From: Marc James Small <marcsmall@xxxxxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx,<rollei_list@xxxxxxxxxxxxx>
- Date: Sun, 04 Nov 2007 20:27:02 -0500
At 08:06 PM 11/4/2007, Richard Knoppow wrote:
> I have heard many references to automated production of
>lenses but I am not sure what this could include. The
>process of making a lens begins with a blank. In the old
>days this was a chunk of glass the right size broken out of
>a "pot" of glass but a later method was to mold the glass
>into the approximate size and shape for the element. The
>elements were then ground on machines which ground many
>lenses at once. Several steps are used to grind the lens
>from rough grinding to finished lens. About the only hand
>work I know of was the making of aspherical surfaces which
>is done now by automated machines. AFAIK such operations as
>centering and cementing must still be largely hand work
>although the determination of the center can be done by a
>sensor working an automatic centering machine. Centering is
>very important especially for elements wich are to be
>cemented.
> Lens mountings must be quite precise but are the sort of
>machining that can be done by CNC machines.
> To some degree the exact curvature and thickness of an
>element can be varied to compensate for small variations in
>glass constants. Usually, the glass is measured before its
>use in production to verify its constants. While glass
>manufacture has advanced a great deal there are still some
>small variations. These can affect all optical aberrations.
> I simply don't see that automated manufacure and
>assembly results in more precise production although it
>probably lowers cost. The fact is that some very fine lenses
>were made before automation.
Rogliatti discusses this in his Leica lens
books: he was able to point out the progress
made by Leitz Midland in shifting production from
hand-assembled lenses to machine-assembled
lenses. Today, Zeiss, with a work force about
half of what it was thirty years back, cranks out
runs of a million lenses a year or more for Sony
digital cameras. This is all automated in one
way or the other, with human intervention only
occurring when a defect surfaces. I am aware of
the broad outlines of this but do not know the details.
Lenses made in this manner are more uniform than
those made in the past by hand assembly. It is
the inevitable course of progress. The same is
true for the production of cars or, for that
matter, of telescopes. I will not speak of the
production of TV sports broadcasts, though I
suspect these, too, have been affected by automation.
Marc
msmall@xxxxxxxxxxxx
Cha robh bàs fir gun ghràs fir!
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