Re: To David Soderman: A Little Test

["Dave King" <kingphoto@xxxxxxxxxxxxxx>]

> > ----- Original Message -----
> > From: "Ernst Dinkla" <E.Dinkla@chello.nl>
> > To: <scan@leben.com>
> > Sent: Thursday, April 11, 2002 5:40 PM
> > Subject: Re: To David Soderman: A Little Test
>
> > > The scan movement can't be done with the gear-teeth and a
> gear
> > > wheel. The only workable solution possible that includes the
> gear
> > > teeth of the carriage could be a belt that fits in the gear
> teeth
> > > over a longer stretch and the belt itself driven by friction
> or
> > > very fine teeth on the inside. But most likely the carrier is
> > > clamped between some wheels and relies on friction movement
> only
> > > for the scan movement.
> > > If it still has to move the uncoupled gear wheel then that in
> > > itself could be a source of vibration.
> > >
> > > The weight difference between the carriages is considerable,
> > > their length varies as well so a rack and pinion kind of
> movement
> > > with teeth of that size isn't an option. I have seen better
> gear
> > > solutions on 19 th century canal locks. I'm tempted to open
> the
> > > scanner as my plan to make another type of glass carrier
> should
> > > be compatible with the scan mechanism in all aspects. Maybe
> > > tomorrow.
> > >
> > > Ernst
> >
> >
> > If you do get in there could you also have a look at the
> mirror(s)
> > positions?  Wondering if they're user accessible for the
> inevitable day they
> > need cleaning.
>
> Taken off the steel cover and resisted my desire to take it
> further apart.
>
> First, there is most likely just one mirror that bends the light
> from vertical to horizontal and so to the rear of the scanner
> where the lens and the CCD are located. Cleaning that mirror and
> the lens that must be horizontal at 1/3 from the rear of the
> scanner is not a DIY job. There's a cilinder like shaped chamber
> made of I guess glassfiber reinforced thermoplastic (looks more
> like a Bakelite but I doubt that is true) that holds the lens,
> mirror and at the rear end the CCD. Not something to take apart
> and put together without the right calibrating tools.
>
> The carrier is inserted in a traction unit that positions the
> carrier for scanning etc with the gear teeth at the side of the
> carrier. For scanning the whole traction unit glides on two rods
> with a traditional 3 point brass bearing setup. That movement is
> done with a finely machined screw spindle (don't know the right
> English term for it). So far I do not see any flaws in the
> mechanical design but maybe one;
> I can't see how the carrier is locked in the traction unit. From
> above some flat springs keep it down but
> if it is only arrested by the gear wheel on any lengthwise
> movement and sideway movement then I fear that it is difficult to
> keep out all vibrations on all the carrier models with their
> different weigths and lengths. Remember that the carrier is
> 'locked' in two extreme positions in the traction unit when it
> scans the first and the last image. The brass bearings are
> capable enough to keep the whole unit straight for a long time.
> But if a Nikon tealady (KME) did design the clamping of the
> carrier in the traction unit then there may be a problem there. A
> good vibration meter on the carrier will tell a lot.
>
> I think it must be in the CCD arrangement what causes the banding
> but I will take the cover off once more to see how the carrier is
> clamped down.
>
> Ernst

Thanks for looking.  Too bad about the optical path surfaces being
inaccessible, I was hoping for something along the lines detailed in these
two posts from the Leica group archive:

http://mejac.palo-alto.ca.us/leica-users/v20/msg04336.html

http://mejac.palo-alto.ca.us/leica-users/v21/msg03062.html


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