Will this do what I want? It appears to be achromatic, (ie plan corrected as I understand it?) and is designed for a 160mm objective tube?
The thread appears to be DIN, which I understand, fits RMS?
Thoughts?
Thanks!
Screenshot for future reference in case the link breaks:
The lens is likely to fit and work, I am not sure of the image quality.
There is one part of the specification that is not in that screenshot and is often not stated. The parfocal distance is usually 45 mm. The Openflexure microscope V6.1.5 is designed to fit 45mm parfocal distance with the slide riser fitted, or should work with the next most common 35mm parfocal distance without the slide riser. The V7.0.0-Alpha2 is designed to work with 45mm only.
The specification does not include the word ‘Plan’, so I would assume that it is indeed achromatic, but not plan. This means that a flat slide will not be in focus all across the slide. How much this matters depends on what you are wanting to look at. If you are planning to scan and tile images then you really do need a Plan corrected objective.
This here is more expensive, however, it states it is a plan objective lens, and has a parfocal length of 45mm so looks like it is the ticket. I will purchase one of these in the next week or so.
I do see the “working distance” is only 0.49mm for the 60x and 0.23mm for the 100x. That seems awfully small. Is this unusual?
How does one go about working out what the final magnification is of the microscope?
The ‘magnification’ does not have a lot of meaning on a digital microscope - if you view it on a phone screen the image size is very different from a 70" 4K screen, but the detail in the image is the same.
With a 60x or 100x objective the detail that you see in the image will be very dependent on the numerical aperture (NA) of the lens, the NA of the illumination and the quality of the lens. The theoretical resolution of these lenses may be 0.4 to 0.7 µm, but that theoretical limit will only be reached with a good lens and good illumination. @r.w.bowman wrote this about resolution and magnification. A 100x lens will usually require an immersion oil between the lens and the sample. The ‘160/0.17’ on the lenses indicates that they are designed for a ‘tube length’ of 160mm, and that they are designed to be used looking through a coverslip of 0.17mm thickness.
The working distance will be very small, usually much less than 1mm for 60 or 100x . The sample should be under a coverslip on the same side of the slide as the objective lens, so the slide ‘upsidedown’ on an inverted microscope design like this. It is possible to get objective lenses with long working distances, but they get expensive very quickly. They are often designated ‘metallurgical’ instead of ‘biological’ lenses, and are not designed for use with any coverslip or glass between the sample and the lens - they are for looking at metal and mineral surfaces. There is one I found that is not too expensive, and also is designed specifically to look through a microscope slide from underneath, so with 1mm of glass, and with a working distance of a few mm. Motic Microscope LWD 40x Plan Objective Lens (motic-microscope.com). It is 40x so has a larger field of view than 60x, but at 0.5NA the theoretical resolution is still about 1µm. I have a couple of Motic microscopes and the lenses are pretty good, I have not yet tried this particular lens.
