Nikon Optiphot

As I have mentioned elsewhere, I do have a number of microscopes. I guess that is not surprising as I'm a microbiologist, but while we have quite a few in my company that are used for real work, I also have a collection of older and interesting models either at home, or in the studio in Germany. I also have a large collection of historic microscope slides and have been collecting, mainly Victorian, prepared slides of diatoms for many years. Now these organisms have wonderful geometric 'skeletons', but being made of silica are rather hard to visualise under the microscope. One can use a number of contrast enhancing methods to view them and the best of these is differential interference contrast (DIC).

I have three microscopes in my collection fitted with DIC, two are inverted (one for use mainly with live, biological specimens, a Reichert Biovert, and a second really aimed at materials, the Reicgert MeF2). I also have a large research microscope with most of the accessories which has DIC, but which still lives at work (actually there is a Zeiss Universal there too for which I have DIC, but it is not operational at the moment). Despite this, I have always fancied a Nikon fitted with DIC and have been keeping my eye out for one that is not too insanely expensive. A couple of weeks back I spotted a full set of DIC optics for sale in Spain and purchased them and they are on their way to my address in Germany. They fit the Nikon Optiphot, a smallish, modular research microscope from the 1980s. These are pretty robust and many can still commonly be found in use in companies and universities today: we have one (and a related model) in our laboratory and they are used very day.

As the Otiphots at work were in use I looked around for one I could use to host the DIC optics I had bought and spotted one on a university equipment resellers website. It looked to be cosmetically very nice and was a very good price, and they included photos showing an image taken through the microscope. However, I assumed there was a good reason that the university were disposing of it. When it arrived it was immediately clear why as the condenser rack was right at the bottom of its travel and completely stuck. A few other controls, such as the lamp adjuster, were stiff and the optics needed a bit of a clean. So, I set to and checked to see what the problem was and hoped the rack and pinion had not been damaged. After dismantling the condenser rack assembly it was clear that it had been driven off its rack and whoever did it was not able to realign it and just got it stuck, not aided by the grease having hardened. It took an hour or so to clean, re-lubricate and reassemble it and now it works perfectly. I also cleaned the microscope externally as well as the optics and stripped and lubricated the phase-contrast condenser it came with. It worked well and I aligned all of the optics correctly and I checked it out using a random selection of slides from my collection.

Although it produced a bright and uniformly lit image, I could see there was dust on the primary mirror in the base and so today I stripped the base from the stand and looked. There was some dust, but most of the 'clouding' was caused by fine oxidation of the surface mirroring which sounds and looks worse that it is, but I still wanted to clean it. Microscope mirrors, like those in reflecting telescopes, are mirrored on their surface and not on the back of a glass support which makes cleaning them much more difficult. While a telescope mirror often has a hardened layer applied to the mirroring due them being exposed to the elements more, microscope mirrors are not, and the (usually) vacuum deposited aluminium is unprotected. This leads to it developing slight oxidation over time. Using a large number of optical tissues I carefully removed the layer, but had to work through the aperture in the mirror block as I did not want to remove it as the light path would then have needed recollimating (which although it is done mechanically rather than optically, I do not have the special tool for and didn't fancy making one). Anyway, the cleaning worked perfectly and the microscope is up and running and ready for the DIC optics when they arrive. I also have an episcopic illumination module for it and a fluorescence module and a wide range of objectives, but at the moment I only have it set up for transmitted, normal light.

Here is a view of the base with primary mirror box and the field iris, and another showing the nice shiny mirror after cleaning.

Optiphot refurb-1.jpg

Optiphot refurb-2.jpg


Here is the microscope fully reassembled (every home should have one of the coffee table I reckon!).

Optiphot refurb-4.jpg


I then stuck an 18MP CMOS camera on the photo-tube and took a few pictures of a couple of old slides. This shows a comparison of the 3 lighting system available at the moment (using a 10X objective).

Bright-field (ie the standard lighting for a light microscope). This is a marine diatom, called Actinoptychus stella. It is about 115 µm in diameter and has been mounted without the cell contents being oxidised and still retains some pigmentation even after about 80-odd years. Note the poor contrast in areas that are not pigmented.

Optiphot Diatoms-5.jpg


Dark field illumination. This results in the subject being lit against a dark ground (by using a patch plate in the condenser that prevents direct transmission) and in this case worked well despite it being an old slide (I only removed 3 dust specks that were embedded in the mountant along with the specimen in 'post production). There is still little definition in the areas without pigmentation.

Optiphot Diatoms-4.jpg


Phase Contrast (which uses phase displaced light to create positive and negative interference in areas of greater optical density in the object (and in the mountant and on the surface of the slide!). Now non-pigmented elements are visible, although slightly degraded by being strongly highlighted (DIC will resolve this).

Optiphot Diatoms-3.jpg


I also created a couple of image stacks at a higher magnification (using a 40X objective) of this and another slide using phase contrast for fun. I rendered them in monochrome and then toned them digitally in the final edit (stacking using Helicon Focus and editing using Adobe Lightroom and Nik ColorEffex 6 and Output Sharpener). Given the ages of the specimens, they came out quite well.

Optiphot Diatoms-1.jpg

Optiphot Diatoms-2.jpg
 
Fascinating stuff, Pete. Remarkable structures, those tiny creatures. As you say, (though I'm certainly purely a layman with this) looking good for their age. Impressive piece of microscope kit, too.
well, I can't say I have a 'scope on the coffee table quite, but I do have a Kyowa stereo zoom 'scope that I used to use in job many moons ago. When I was made redundant through company restructuring, they let me keep hold of the instrument, writing it off as surplus or scrap or something. A rather different beast to the ones you describe, but a useful tool nonetheless. Anyway, not sure my little coffee table would accommodate it that well either lol.
 
Definitely fascinating! I have no expertise to go into detail, but I completely understand the desire to bring this microscope and these old Diatom samples back to life. The topic somewhat marginally intersects my daily life, but I will not dwell on that.
 
Thanks, all. It proved to be a good buy and will be a perfect platform for the DIC optics when they arrive. I need to source a couple of ND filters for the filter rack between the lamp and the field iris (it has a colour correction filters and a green filter plus a diffuser at present) so that I do not need to turn the lamp down and so decrease the colour temperature at low magnification / bright-field use.

At present it is fitted with a 4X bright-field objective plus 10X and 40X phase contrast objectives and I found a 20X and 100X DL Phase contrast objectives online and have purchased those to complete the range on that turret. I also have some other bright-field objectives that I will put on another turret for use with a non-phase contrast condenser which can also provide a wider illumination field for those with lower magnification. There is a third turret which I will populate with objectives designed for a longer tube-length (210 mm vs 160 mm) which will be used with the episcopic lifting unit (which adds 50 mm to the light path). The turrets often come up on eBay and so I may buy another to populate with fluorescence objectives of which I have a couple already. I have a few specialised objectives as well and maybe I'll even get a fifth turret and put those on it.

I also bought a polarisation stage from the same person in Spain that I bought the DIC optics from, but it is slightly tatty and two of the screws will need to be re-made. However, it was a bargain and they usually sell for more than twice what I paid for the microscope if they ever appear on the market so a few hours work on it will be worth it.
 
Pretty cool Pete! The microscope that I purchased while I was fooling with watch work is boxed up in the garage. While I have a damaged retina in my left eye that affects my eyesight oddly enough I could still see stereo-depth through the scope. I was never able to get tack-sharp photos through the scope and try as I might I was never able to actually figure that out either - you'd think it would be a simple matter of distance.whole rig - small.jpg
 
Back
Top