[rollei_list] Re: Spinning front taking lens
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <rollei_list@xxxxxxxxxxxxx>
- Date: Thu, 29 Dec 2005 14:56:18 -0800
----- Original Message -----
From: "Jim Brick" <jim@xxxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Thursday, December 29, 2005 9:33 AM
Subject: [rollei_list] Re: Spinning front taking lens
I'm not sure that I understand this lens spinning
property.
I have always been told that in lenses that consist of
more than one element, each element has a specific
orientation with the other elements in the group. I was
told that if I took a lens apart, I should mark each
elements orientation so that it could be reassembled with
each element oriented properly with respect to the other
elements.
So a spinning element makes no sense to me.
??
Jim
This isn't true. Spacing can be critical but rotational
position is not. Lenses are very precisely centered when
manufactured. This is done by placing the polished lens
element on the end of a rotating tube covered with something
like pitch as a lap. A point of light from a collimator is
shown on the lens and the reflections from both sides viewed
in a telescope. The lens is pushed around on the lap while
rotating until the images of the point are stationary. The
lens is then clamped on the top by a second tube and the
edges ground precisely parallel and concentric with the
optical axis. A variation of this method is used to
precisely center cemented elements. The current technique is
to optically center each element as it is cemented and then
grind the edges of the assembly. An earlier method was to
very precisely center and grind each element and clamp the
edges for assembly. The optical method elimates some of the
accumulated error possible with the older method.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
---
Rollei List
- Post to rollei_list@xxxxxxxxxxxxx
- Subscribe at rollei_list-request@xxxxxxxxxxxxx with 'subscribe'
in the subject field OR by logging into www.freelists.org
- Unsubscribe at rollei_list-request@xxxxxxxxxxxxx with
'unsubscribe' in the subject field OR by logging into www.freelists.org
- Online, searchable archives are available at
//www.freelists.org/archives/rollei_list
Other related posts:
