Microscope objectives can be confusing, and detailed specs (or even basic properties) are often hard to find. Here's an introductory resource to help new builders and instrument designers with the basics. It's a work in progress so feedback is appreciated: amsikking.github.io/microscope_o... - ThreadSky

amsikking.bsky.social • 2 days ago

Microscope objectives can be confusing, and detailed specs (or even basic properties) are often hard to find. Here's an introductory resource to help new builders and instrument designers with the basics. It's a work in progress so feedback is appreciated:

https://amsikking.github.io/microscope_objectives/

Comments

kmdouglass.bsky.social•2 days ago

Regarding the field of view: what do you think about using the field number divided by the magnification?

I recently did some calculations for an illumination system and used this as the size of the objective's entrance window. The numbers seemed quite reasonable.

amsikking.bsky.social•1 day ago

So I just reread my section on FOV and I think I still agree with my old self. So yeah FOV ~ FN / M is better than nothing.

https://amsikking.github.io/microscope_objectives/field_of_view.html

lumasullo.bsky.social•1 day ago

Interesting! But how do you measure/calculate the FN independently?

jsdaniel02.bsky.social•1 day ago

The FN is a spec of the objective. From it you can estimate the usable FOV. However there is not a uniform rigorous definition of FN or FOV. The lack of rigor is a defensible approach because different applications vary on what is "good enough" optical performance.

lumasullo.bsky.social•1 day ago

what do you mean by “a spec” ?Like it’s reported by the manufacturer presumably obtained through some measurement? My question is how would one measure it independently, or how does the manufacturer come up with the spec

jsdaniel02.bsky.social•1 day ago

FN is reported by the manufacturer based on some metric(s) that they choose. Usually the image size where wavefront error or some other aberration is deemed to exceed acceptable limits however they define acceptable. It is a perfectly fair question to ask the manufacturer what criteria they use.

jsdaniel02.bsky.social•1 day ago

E.g. if your camera is spatially undersampling then the usable FOV might be larger because you are less sensitive to degraded Strehl ratio at the edges. If you are insensitive to field curvature then your usable FOV might be larger than a colleague who really needs a flat field. Etc.

kmdouglass.bsky.social•1 day ago

I wonder why the FN is not defined in terms of the size of the entrance window, i.e. the image of the objective's field stop. It would be easy for manufacturers to determine from the lens data (I assume), and anyone else who has more demanding applications could apply their own definition.

jamesdmanton.bsky.social•1 day ago

Because the field stop is part of the microscope, not the objective?

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