How to open a Mitty?

enricosavazzi · Post by **enricosavazzi** » Thu Jan 23, 2020 5:08 am

Adalbert wrote:So, there is no possibility to align anything.[...]

One of the types of alignment that may be done is by rotating elements with respect to each other, while measuring the optical parameters to find the best reciprocal orientation. This type of alignment may be done at the factory before inserting the stack of sleeves containing the individual optical groups into the barrel, so it is possible even when there are no centering adjustment holes/screws.

In principle, centering may have been done when mounting/cementing the individual optical groups into their metal retaining sleeves, leaving other types of alignment to subsequent assembly stages.

Adalbert · Post by **Adalbert** » Thu Jan 23, 2020 5:38 am

Hello Enrico,

rotating elements

yes, you can rotate the whole groups but the lenses are placed in the middle of the cylinders.
Why the rotation of the lenses should improve anything, could you explain please?

I’m afraid if something was asymmetrical then the defect would only be moved to the other position.

I only can imagine that the defects of the two groups could be compensated by the rotation.
But I wouldn’t expect that Mitutyo cannot mount the lenses perpendicularly to the optical axis.

BR, ADi

lothman · Post by **lothman** » Thu Jan 23, 2020 6:42 am

Adalbert wrote:Hello Enrico,
yes, you can rotate the whole groups but the lenses are placed in the middle of the cylinders.
Why the rotation of the lenses should improve anything, could you explain please?

I’m afraid if something was asymmetrical then the defect would only be moved to the other position.

I only can imagine that the defects of the two groups could be compensated by the rotation.
But I wouldn’t expect that Mitutyo cannot mount the lenses perpendicularly to the optical axis.

BR, ADi

you always have tolerances, so the center of the ground sphere of a lens is never 100% aligned with the outer diameter of the lens. So you can crank up production quality at high expenses or adjust the lens while assembly.
With the bare eye everything looks just fine but at micron level not. Even if you tighten the threads you will deform you whole stack. An experienced worker at a lens manufacturer knows this and can compensate/adjust those effects before tightening and therefore can achieve an ultra precision lens (of course with some jigs, test setups and years of experience and finger feeling). That's what those Zeiss, Leitz, Schneider... guys were/are famous for.

Adalbert · Post by **Adalbert** » Thu Jan 23, 2020 7:05 am

Hello Lothman,

Very interesting!

(of course with some jigs, test setups and years of experience and finger feeling).

OK, I can imagine that :-)

Even if you tighten the threads you will deform you whole stack.

blessedly this problem doesn’t exist if you open the front of the Mitty 2x (see the picture attached)

I am curious to see how the lens will behave.

BR, ADi

rjlittlefield · Post by **rjlittlefield** » Thu Jan 23, 2020 11:34 am

Adalbert wrote:I am curious to see how the lens will behave.

Me too.

In any case, it's very clear that this 2X objective has a different construction style from higher magnifications. Starting at 14:52 in https://www.youtube.com/watch?v=J16EeaibdNE , you can see two of the adjustment ports for the 20X objective that is being disassembled. My bad 10X Mitty has similar ports. I don't know about other magnifications. I expect that all higher magnifications have them, but maybe the 5X does not either. Except on the bad 10X, I have not removed barrels to look.

--Rik

Adalbert · Post by **Adalbert** » Fri Jan 24, 2020 8:12 am

Hello everybody,
I have just taken the photographs of some parallel lines printed by the laser printer.
And the stack has been developed as usual.

Original size: https://live.staticflickr.com/65535/494 ... 31ce_o.jpg
BR, ADi

rjlittlefield · Post by **rjlittlefield** » Fri Jan 24, 2020 8:17 am

Seems to have survived OK. The center is sharp and the corners look symmetric, though not so sharp and with quite a bit of CA (which I recall other people seeing in their 2X's also).

Do you have a "before" shot for direct comparison?

--Rik

Adalbert · Post by **Adalbert** » Fri Jan 24, 2020 8:32 am

Hello Rik,
Unfortunately I haven’t taken any photographs before

This is the first one :-)
BR, ADi

Macro_Cosmos · Post by **Macro_Cosmos** » Sat Jan 25, 2020 10:40 pm

Oof, the CA, it's also soft. What's the tube lens? The PN95 Nikon is still the 2x reference.

Not bad overall, too bad there's no "before" images. However I do agree with Rik here, a 2x lens should have larger assembly tolerances than a 10x. It survived!

Just wondering, how much did you actually pay for the lens?

Adalbert · Post by **Adalbert** » Sun Jan 26, 2020 3:14 am

Hi Macro_Cosmos,
The Raynox DCR-150 has been used.
BTW, see PM.
BR, ADi

Macro_Cosmos · Post by **Macro_Cosmos** » Sun Jan 26, 2020 6:29 am

Ah, the raynox. Then the corners are kind of unexpected, unless this is the norm of the mit 2x.

Generally, I've found line scanner lenses and even bellow lenses to perform better then objective lenses when it comes to low mag. such as 1x and 2x. I think this has something to do with the size of the lens, larger size enables better correction. Objective lenses are... well pretty small! They have to be.

Not sure about stacking, but if we look at Robert's tests, they show superior results too.

Adalbert · Post by **Adalbert** » Sun Jan 26, 2020 8:20 am

Hello Macro_Cosmos,

I've found line scanner lenses and even bellow lenses to perform better then objective lenses when it comes to low mag.

Yes, usually I use my Rodagon Apo N 50 for the magn 2x
but if I want to stack by autofocus then I take the microscope objectives corrected to infinity.
Mostly Mitty 5x or NIKON 4x and CANON EF 100L Macro as a tube-lens.

BR, ADi