Have I ruined my mitutoyo 10/0.28? I need some help

[seta666]

Hello,

Yesterday I had a little "accident" with my mitutoyo 10/0.28; while placing a difuser I unthreaded the front element (diffuser was too tight), I did not completely removed it but it came loose.

After tightening it againg the mitutoyo has a big drop in performance with haze, CAs and low resolution.

I completely dissasemble the mitu and I do not understand it, it seems to me it is impossible to missalign the lenses as all elements are fixed in metal barrels, yet the performance drop is evident

Triying to clean the lenses (some dust got inside whe I inspected it)made the problem worse as now there is some small dust specks

Any ideas? could this small dust specks affect performance that much?








100% crops of a single shot, mitutoyo 5/014 resized to match




I am pretty angry with myself as this one of my favorite lenses and one I use all the time in the studio

Regards
Javier

[discomorphella]

Oh no. I will ask some of the optical design engineers I work with, but I am afraid at least some of these elements are potentially placed to micron accuracy in the final assembly process. Its not as crucial as for a 1.4 NA objective, but unfortunately the relationships between the lens groups and individual elements are crucial in cancelling aberrations. They have been computationally optimized, and potentially checked using an interferometer as part of the final assembly process, at least if my experience with custom objective design is any guide. Did you note the distances, and also, the orientations of each of the lenses with respect to each other? In other words, Element N is X microns from Element (N+1) and was rotated 0.2 radians CCW. This sort of information will be important in final re-assembly.
I don't think that a few specks of dust could introduce CA. Haze and other scatter perhaps, but either variety of CA is much more likely to be an indication of either misplaced distance and/or orientation. How does the haze/lack of contrast respond through focus? This could also give some clues as to what is happening. I will try to find out what I can for you. It may be that you will have to re-assemble the objective as best you can and get a repair quote from your local Mitutoyo representative. Sorry to be the bearer of bad news.
Regards,

David

[seta666]

Thank you David for all this information;

- I would say is impossible to change the distance between elements as they sit on of top of the others, once you place the final thread it makes a tight fit.

- I would have never thought that rotating an element clockwise would change performance, unfortunaly all of the element have rotated and there is no alignment marks to suggest proper orientation.

- Is there any procedure that one can make at home to align those lens elements?

- I do not think there is Mitutoyo repair service here in Spain


I will make a pìcture of something defocused as it acts in a funy way

Regards

[discomorphella]

Hi Javier,

The distances between the elements probably look relatively fixed, but for micron tolerances they may not be so, unfortunately. How tightly the assemblies are screwed down may change distances slightly. Did you find any thin pieces of material that could be a spacer in any of the sub-assemblies?
As for rotation, the "clocking" of lens elements is a trick to help attenuate certain aberrations that are not azimuthally symmetric, and also, these lens elements are of course, not perfectly shaped, so often rotating one can actually change its angle relative to the optical axis (tilt) slightly. Alas, slight changes can be important. Don't give up yet....you still have all the pieces after all. I need to ask my colleagues if any of them have repaired a similar LWD objective.
Regards,
David

[seta666]

Hi Javier,
The distances between the elements probably look relatively fixed, but for micron tolerances they may not be so, unfortunately. How tightly the assemblies are screwed down may change distances slightly. Did you find any thin pieces of material that could be a spacer in any of the sub-assemblies?

As you can see in the third picture there is a couple of metal spacers, but once everything is in place and closed there is no way there could be any more separation

Meanwhile I have contacted a couple of friends to see if they can get me quotes from international mitutoyo service centers

http://www.mitutoyo.co.jp/eng/corporate ... /list.html

I could try to make some marks on the different elements casings and maybe after couple of thousand tests I could get it right, but if I gbet a reasonable repair quote I rather go that way

Thank you
Javier

[ChrisR]

I wish you luck, but I asked for a similar service from Nikon UK and found it wasn't cost-effective.
Their hourly rate for work like that wss £400, = $600.

[seta666]

I wish you luck, but I asked for a similar service from Nikon UK and found it wasn't cost-effective.
Their hourly rate for work like that wss £400, = $600.

I really hope you are wrong; anyway, I do not think it can take long time to adjust it with the right measurament equipment.

What would be the procedure to align such lens, a laser beam or something like that?

Regards
Javier

[ChrisR]

I can look for Mitty UK, Monday. It would be interesting to hear what they say, anyway.

[seta666]

Thank you Chris;

I would really apreciate that

[Tomatito]

Gosh Javier, What have you done? I feel really sorry for you man..I honestly don't think so that your mitutoyo is going to work poperly anymore, it is probably better to buy another one, even if you repair it it is going to be NA like 0.23 instead of 0.28 ..probably they use some laser to go throught the lens when they assembling the lens, as u don't have it you not gonna make it 0.28 anymore..that's my opinion, Probably I am wrong ...

[seta666]

Yes, sometimes accidents happen (even stupid ones). I do not see how this can affect at the NA of the lens.

If repair dervice is not too high I still think is worth repairing, mitutoyos are pretty expenssive these days.

We have to look at the bright side of life, now we now how a mitutoyo looks in the inside ;-)

regards
Javier

[soldevilla]

Are you sure you have properly installed all lenses? I have some experience polishing optics and collimating telescopes, and I can not believe this result you get now if the lens are corrected mounted. It is true that there is a rumor about a telescope in which the optical components have position but the eyepieces no ... Automatically carve spherical surfaces are easy. I can not believe that a prestige brand like Mitutoyo can carve lenses in which the optical axes of the two faces are not coincident.

I am betting on an assembly error. I think you should try to turn one by one each lens to find out where the error is. Luck!

[seta666]

Are you sure you have properly installed all lenses?

I am 99% sure they are in the right position, the drop in performance was noticed before I dissasembled the lens.

Regards
Javier

[rjlittlefield]

We have to look at the bright side of life, now we now how a mitutoyo looks in the inside ;-)

Yes, and I especially thank you for this because I am facing a similar problem with one of my own Mitutoyo 10X objectives.

In my case, it is completely unclear what happened to cause the problem. All I know is that the lens used to work fine and now it shows reduced resolution and some aberration that looks like decentration. In between those times, I did not notice that the lens was dropped, knocked, or even set down hard. No collars are loose. But the aberration is clearly present when pixel-peeping. I have not disassembled the lens, and I do not plan to do so.

I can not believe this result you get now if the lens are corrected mounted.

Unfortunately the tolerances really are quite tight for these lenses with large NA and strong curvatures. As summarized at http://specialoptics.com/custom/precision.html,

Assembly of diffraction limited lens system is equally as important as the polishing of the lens elements themselves. In fact, many times performance degradation is traced to poor lens assembly, not the lens elements. In particular, air-spaces, centration, tilt and wedge are the key determinants of a quality lens system.

Air-Spaces

In high resolution systems, very often it is necessary to measure and maintain lens spacings to the order of a few microns. Not an easy task, but one that we have worked extensively at perfecting. Through the use of micron indicators coupled with proprietary assembly equipment we can hold lens spacing tolerances to the order of 1 micron. This is only possible through constant reoptimization of the lens design during the assembly process.

Centration, Wedge and Tilt

A major challenge during assembly of diffraction limited optics is to maintain the centration, wedge and tilt specifications for the system of lenses as a whole. Simply inserting lenses and spacers into lens tubes is not sufficient or even possible in many cases. Over the years we have developed both standard and proprietary techniques for insuring that all tolerances are met.
Assembly Capabilities

. Air-Space Tolerances Held to 1 Micron
. Continuous Lens Design Reoptimization During Assembly
. Centration, Wedge and Tilt tolerances held to Better than 1 Micron

--Rik

[dmillard]

Yes, sometimes accidents happen (even stupid ones). I do not see how this can affect at the NA of the lens.

If repair dervice is not too high I still think is worth repairing, mitutoyos are pretty expenssive these days.

We have to look at the bright side of life, now we now how a mitutoyo looks in the inside ;-)

regards
Javier

Hello Javier,

Very sorry to hear about your objective! I can sympathize - I still remember the morning 6 years ago when I was at Big Bend National Park, and dropped a 100mm Zeiss Planar that was cammed to my 23 Technika.

Hopefully you can get all the pieces back to where they belong. It is apparently a far more delicate object than I was aware.

Regards,
David