JMC Posted May 2, 2020 Share Posted May 2, 2020 I've recently been doing a bit of microscopy (bringing an old Olympus BHB microscope back from the grave), and while buying bits for it I came across an odd objective lens - the Reichert 40x reflecting objective. I was the only person to bid on it, and a few days later it arrived. It's a funny little thing. It has a dovetail mount for use on a Reichert microscope, but that mount unscrews to reveal a standard RMS screw thread. Here's the lens. Apparently designed for multispectral imaging, I was wondering what it'd be like for UV photography. I mean, what could possibly go wrong?? On the lens it says 250/1.5Qu, which as I understand it means it's meant for a tube length of 250mm and quartz coverslip of 1.5mm. I mounted it on a range of extension tubes to get me out to 250mm, and I could see..... absolutely nothing, couldn't get any focus at any distance. Back to basics, about 10mm extension and straight on to my UV modified d810. Amazingly, moving it back and forth I could see something come in and out of focus. Very quickly in and out of focus. Very, very quickly. Subject is a Dandelion and lighting using my Hamamatsu LC8 200w xenon lamp and collimating lens, setup shown below. And what did it show? Here is a UV image taken with it, full frame (no cropping) and whitebalanced in Darktable. I've upped the contrast and boosted the saturation slightly (and reduced the size for sharing), but other than that unmodified. This is part of the stamen style of the Dandelion, showing some pollen grains, with another part of the flower out of focus towards the right hand side of the image. Pretty trippy stuff, with some crazy reflections and flare. I see Enrico has written a bit about a Spectra-Tech Reflachromat lens, here, but I haven't been able to find out much about the Reichert one anywhere. It's certainly much smaller than the Spectra-Tech one, and is marked up as having higher magnification. Will it be useful? I'd struggle think how I'd use this for photography. Lighting is a nightmare, and fitting a hood would be 'challenging' to say the least. While it's marked as being designed for a 250mm tube length, I had no joy with long extensions. Depth of field is essentially zero, so stacking would be a must. I am planning on building a photomacrography rig in the future, and when I have stacking capability, I shall have another play with it. However despite all this, it is a cool little lens, so thought I would share it here. Link to comment Share on other sites More sharing options...
Andy Perrin Posted May 2, 2020 Share Posted May 2, 2020 The depth of field is amazingly narrow. Like a knife slice! Link to comment Share on other sites More sharing options...
OlDoinyo Posted May 2, 2020 Share Posted May 2, 2020 Sometimes those objectives are mini-Cassegrain optics. I wonder if this one is.. They are of course not intended as stand-alone optics, hence the difficulty in trying to use them as such. Link to comment Share on other sites More sharing options...
dabateman Posted May 2, 2020 Share Posted May 2, 2020 If it has an RMS mount it might not actually need a 250mm tube length to focus.My 80x meteorological lens is RMS, listed as 210mm tube. But it acually is better at 160mm. Mounts just fine on a regular microscope. On my camera it was happy a little closer to the film plain. If your microscope is RMS, can't remember. Might be good to just try it out. Found this information for it:Reichert 40/0.52 (catalog number), 250/1.5 Qu np special purpose objective for Zetopan MeF-1 and MeF-2 Inverted Metallurgical Microscopes. This objective designed to use with heating stage. Because of the extreme high temperature involved (up to 1700° C) the sample chamber is water cooled and observation done in a vacuum. The window to the chamber is of 1.5mm quartz glass, hence the 1.5 Qu nomenclature. The front lens of objective is very large in diameter to achieve a relatively large numerical aperture (0.52) given the exceptional working distance the heating stage required. This objective has concave mirror at the front end; it is cardioid-type objective configuration. It has 20.2mm threads sizes - RMS (Royal Microscope Society) standard and comes with 24mm dovetail sliding bracket. Link to comment Share on other sites More sharing options...
nfoto Posted May 2, 2020 Share Posted May 2, 2020 Nice find, might be well worth combining with focus stacking. On a terminology note, you have depicted the style not the stamen or anther. Dandelion flowers have a complex design and one needs to thread carefully with the terms. The style of the flower pushes through an anther tube and thus gets loaded with pollen grain on the outside. The style surface can be densely set with long conical cells that together act like a chimney sweeper's broom. The style tip splits into two halves that curl up to expose the stigmatic (receptive) surface inside. Wikipedia has several entries on the floral structure of the members of Asteraceae, the family to which the common dandelion belongs. A perusal can be enlightening -- and challenging at the same time.... Link to comment Share on other sites More sharing options...
bobfriedman Posted May 2, 2020 Share Posted May 2, 2020 Nice find, might be well worth combining with focus stacking. my exact first thoughts.. please do try some. Link to comment Share on other sites More sharing options...
ulf Posted May 3, 2020 Share Posted May 3, 2020 A 40/0.52 microscope lens has an extremely thin DOF if used correctly.Such high NA makes it very important to have a "cover" glass-component with correct thickness and refractive index, in the light-path.That is a part of the designed optical formula.Most of the flare and things looking like reflections is likely from the extreme spherical aberration due to the missing coverglass. Most metallurgical microscope lenses are designed to work without coverglass. The older non-infinity-types often had a tube-length of 210mm. The biological lens types had a tube-length of 160mm are designed to work with a thin coverglass.Often it is possible to vary the actual tube length just as we do with normal macro photography to change magnification without much quality-loss Link to comment Share on other sites More sharing options...
JMC Posted May 3, 2020 Author Share Posted May 3, 2020 Thanks for the comments. Birna, I have updated it to style instead of stamen. David, I was sure I had read somewhere about it being used for high temperature work, but couldn't find the information again, so thanks for doing that. I do have an RMS thread microscope, and will give it a go on there and see if I can see anything. EDIT - tried it on my microscope and couldn't get an image. Mine is a 160mm tube length, whereas this lens looks to be for a 250mm length one. Perhaps if I were to make a 90mm extension to the photo tube on top, that would work, but that's not something I'll be doing for now. The top part of the lens contains a 1.5mm quartz window, so that is in effect the coverslip mentioned. That top part can be easily removed by unscrewing, to reveal this. The front element has an extreme curve (concave when viewed from above) and in the middle a black dot about 3mm across. I am assuming this black dot is mirrored on the underside. Whether or not removing the top half of the lens makes it impossible to use it, I haven't tried yet. Looking down from the front I can see a larger mirrored surface inside the objective. I'm planning on measuring the transmission through this when I'm next using the spectrometer. Link to comment Share on other sites More sharing options...
nfoto Posted May 3, 2020 Share Posted May 3, 2020 It obviously is a kind of mirror reflex objective. Don't remove anything in front other than the quartz window .... Link to comment Share on other sites More sharing options...
JMC Posted May 3, 2020 Author Share Posted May 3, 2020 Birna, absolutely, and I have no desire to dismantle it any further. Well, I got bored so I measured the transmission - complete lens, and then without the quartz window. Bit disappointed, I was hoping this would be useful for UVB, but it turns out not to be. Still useful for UVA though. Absolute values may be a little lower than reality, as the elements are so small, and I'm trying to align the lens in the beam of the light source to measure the transmission. The quartz window is actually robbing a bit of light, probably due to reflection, but also I didn't make much of an effort to clean it. Inside it looked pristine. Probably never been opened before. It is really tiny. Here's a picture of the lens next to a ruler (inches scale). Link to comment Share on other sites More sharing options...
SteveE Posted May 6, 2020 Share Posted May 6, 2020 Could the quartz window be a corrector plate? My Celestron Schmidt-Casegrain telescope has glass at the front that is slightly not flat and is used to compensate for aberrations. Link to comment Share on other sites More sharing options...
ulf Posted May 7, 2020 Share Posted May 7, 2020 The top part of the lens contains a 1.5mm quartz window, so that is in effect the coverslip mentioned. I do not think that is correct.I believe that is the front element of the lens having some curvature The 1.5mm quartz window is a part of a water-cooled heated vacuum-chamber.Something like the chamber on page 10 here:https://www.upc.edu/sct/ca/documents_equipament/d_129_id-513.pdf Link to comment Share on other sites More sharing options...
JMC Posted May 7, 2020 Author Share Posted May 7, 2020 Yes, Ulf, I think I misread that - looks like the high temp chamber has a 1.5mm coverslip built into it. I shall correct my post. So I presume I should be using it through a 1.5mm quartz window then really? Link to comment Share on other sites More sharing options...
ulf Posted May 7, 2020 Share Posted May 7, 2020 Yes, Ulf, I think I misread that - looks like the high temp chamber has a 1.5mm coverslip built into it. I shall correct my post. So I presume I should be using it through a 1.5mm quartz window then really?Yes, that is what I think the correct setup shall be.You will have a VERY shallow DOF with an NA of 0.52. That is almost the same as the microscope lens I used for imaging a root of my hair.I needed ca 50 images to see half of a hair's thickness.(VIS as it was before I started with UV)I think the lens was a 60X NA0.6 Link to comment Share on other sites More sharing options...
JMC Posted May 7, 2020 Author Share Posted May 7, 2020 Nice image Ulf. I believe that is a hair root in its telogen phase. Yes, depth of field will be tiny. Link to comment Share on other sites More sharing options...
Lou Jost Posted December 9, 2022 Share Posted December 9, 2022 I have this objective also, and in 2018 the good folks at photomacrography.com dug up the lens design and other information for me here: https://www.photomacrography.net/forum/viewtopic.php?t=37189 The element that you removed is indeed part of the optical system, as shown in the lens diagram. Sadly this objective appears not to be designed especially for UV observing. The quartz cover slip is for heat resistance, not UV transmission, and the reflector design is used here primarily to increase working distance, in order to escape the intense heat of the subject. Link to comment Share on other sites More sharing options...
JMC Posted December 9, 2022 Author Share Posted December 9, 2022 8 hours ago, Lou Jost said: I have this objective also, and in 2018 the good folks at photomacrography.com dug up the lens design and other information for me here: https://www.photomacrography.net/forum/viewtopic.php?t=37189 The element that you removed is indeed part of the optical system, as shown in the lens diagram. Sadly this objective appears not to be designed especially for UV observing. The quartz cover slip is for heat resistance, not UV transmission, and the reflector design is used here primarily to increase working distance, in order to escape the intense heat of the subject. Yes indeed. It was for the high temp setup for the Reichert MeF2 and not for UV work. Funnily enough I managed to get an English version of set of the three volumes of the book mentioned in the link - Pluta's Light Microscopy. I must see what it has about this little objective. Link to comment Share on other sites More sharing options...
Lou Jost Posted December 9, 2022 Share Posted December 9, 2022 An English version of that book must be very very interesting! Link to comment Share on other sites More sharing options...
JMC Posted December 9, 2022 Author Share Posted December 9, 2022 1 hour ago, Lou Jost said: An English version of that book must be very very interesting! Yes it's a fascinating collection of work. Link to comment Share on other sites More sharing options...
Andy Perrin Posted December 9, 2022 Share Posted December 9, 2022 The author missed an opportunity to title it, "A Little Light Microscopy" in my opinion. Link to comment Share on other sites More sharing options...
dabateman Posted December 10, 2022 Share Posted December 10, 2022 20 hours ago, Andy Perrin said: The author missed an opportunity to title it, "A Little Light Microscopy" in my opinion. Well that 3 year warranty in the background has probably expired by now too. Also little light and a lite microscopy indeed. Link to comment Share on other sites More sharing options...
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