Material on the lens especially for Radozhiva prepared Rodion Eshmakov.
Modern Chinese achromat 10×0.25 160/0.17 and the old 10/0.30 160/-.
This article presents an old 10x microscope objective for microscopes with a final tube distance of 160 mm. There is no manufacturer's marking on the objective, but its appearance and execution correspond to Carl Zeiss Jena objectives. An interesting feature of the objective is its increased numerical aperture compared to that typical for optics of that time, as well as correction for specimens without a cover glass.
Technical specifications
Optical design – 5 lenses in 3 groups, aplanat;
Drawing of the optical scheme of the lens.
Type of correction – achromat;
Tube distance – 160 mm;
Parfocal distance – 33 mm;
Magnification factor – 10x;
Numerical aperture – 0.3;
Working distance – 6 mm;
Cover glass thickness – 0 mm;
Chromatic difference in magnification – not corrected;
Immersion required - no;
Mounting type – RMS standard (4/5” x 1/36” thread);
Features - microscopic lens, does not have an iris diaphragm and a focusing mechanism.
Lens design
The lens is designed in a completely simple way: in a brass body with a slotted nut on the side of the mounting thread there are 3 lens components in autocollimation frames. The position of the lenses does not require additional centering through holes in the body, as is done with many other lenses of the type LOMO OM-2 Plan 9×0.2The front lens has no protection, not even a small protective edge, so you should handle the lens carefully and not rest it on the nose.
The advantage is the presence of an anti-reflective coating of the lenses and ribbing on the inter-lens inserts (light protection), which almost all Soviet micro lenses cannot boast of. Among Soviet 10x lenses, only LOMO OE-9 9×0.2 EpiIt is known that this lens is also available without coating.
The light transmission spectrum of the lens is 10×0.3 160/-.
Compared to small aperture achromats of the type LOMO M-42 8×0.2 or OE-9 9×0.2 This one has a more complex optical design, which also includes a strongly positive front element. It is very likely that, unlike the already mentioned LOMO achromats, this objective uses barium or heavy crowns in the positive lenses, rather than simple K14 types. This is evidenced by the detection of zinc, barium and strontium in the front and rear lenses of the objective using the X-ray fluorescence analysis method.
XRF spectrum of the front lens element.
XRF spectrum of the rear lens element. The lead peak is from the penultimate lens element, made of heavy flint.
In terms of build quality, the Carl Zeiss Jena 10/0.30 160/- lens is significantly superior to the similar Soviet LOMO OM-5 10×0.3 lens due to the presence of coating and higher quality light protection.
Optical properties
The lens produces a contrasty and fairly sharp image in the center of the field. The curvature of the image field is not corrected, the difference in focus between the center and the corner of the APS-C frame is very impressive. Field aberrations are corrected quite well, but everything is spoiled by the high level of lateral chromatic aberration - this lens is not intended for use in direct projection and requires the use of compensating eyepieces or gomals.
The image contrast is significantly better than that of similar lenses without an anti-reflective coating. Thus, if we compare this lens with the Soviet phase-contrast LOMO OM-5 from the KF-4 condenser kit, which has a practically discolored phase ring, then it is in the overall image contrast that the difference turns out to be colossal, although the sharpness and detail differ only slightly.
The level of spherochromatic aberrations of the lens is surprisingly not too high if compared to cheap 10x lenses. At least this 10x0.3 is not inferior Chinese achromat 10×0.25 in the central area of the image and even probably surpasses it in terms of detail level. However, by the standards of photographic equipment, the quality of the lens correction definitely cannot be called satisfactory. A comparison of the image quality of this 10x0.3 with other 8-10x lenses is given here.
Below are examples of photographs taken with a 10/0.30 160/- lens without stacking using a modified NPZ M-10 microscope and a Sony NEX-6 (APS-C) camera.
Objects in the photo: 1) Ammonium pentafluoroperoxotitanate; 2) Potassium bis-oxalatodiaquacuprate; 3) Hexaamminenickel chloride; 4) Silica gel for chromatography; 5) Crystalline sulfur film; 6) Ammonium hydrogen phosphate crystals with inclusions; 7-13) Crystalline sulfur film; 14) Chromium acetylacetonate. Photos 1-6 were obtained by the dark field method in transmitted light with an OI-10 condenser. Photos 8 and 9 were obtained by the dark field method in transmitted light with a KF-4 condenser and a diaphragm for a 90x objective. Photos 10-13 were taken in polarized light.
Below are some photos taken with stacking, using the same equipment.
Objects in the photo: 1) Ammonium pentafluoroperoxotitanate; 2) Potassium bis-oxalatodiaquacuprate; 3) Hexaamminenickel chloride; 4) Silica gel for chromatography; 5) Crystalline sulfur film; 6) Ammonium hydrogen phosphate crystals with inclusions; 7-12) Crystalline sulfur film; 13) Chromium acetylacetonate, 14) Copper carbonate complex. Photos 1-6 were obtained by the dark field method in transmitted light with an OI-10 condenser. Photos 7 and 8 were obtained by the dark field method in transmitted light with a KF-4 condenser and a diaphragm for a 90x objective. Photos 9-12 were taken in polarized light.
Conclusions
The 10/0.30 160/- objective is another old affordable microscope objective. Made qualitatively and easy to use, this achromat has one big drawback in the form of uncorrected lateral chromatic aberration, which limits the image quality obtained when using it with a camera in direct projection. Probably, the objective is well suited for replacing the standard LOMO 8×0.2 on an old microscope, if there is no desire to install new optics with a parfocal distance of 45 mm. Otherwise, a similar result (with the same drawback in chromatic aberration across the field), but with a flat field and better sharpness, allows get chinese planachromat 10×0.25 of of this line.
