3 ms·

I work on digital microscope scanners and I have always thought that 1um was the general value for a 10x objective (because that is always what it is on scanner

by EpicEng 13y ago

I work on digital microscope scanners and I have always thought that 1um was the general value for a 10x objective (because that is always what it is on scanners.), 0.5um for 20x, etc. I realize that many factors contribute to effective magnification (and resolution), but your statement makes me want to look more closely at standard microscopes.

chrisBob 13y ago
The resolution is given by 1.22λ/NA. λ can be rounded to 500nm and the NA of a standard 20x objective is .4 giving 1.5µm. This is good because I was worried you caught me just making things up for the internet. A 40x with a .65 NA gives just under 1µm resolution. Resolution is also a slightly fuzzy spec depending on the audience. I go with the Raleigh criteria: You can't distinguish between two particles separated by less than the resolution distance. You can however, see particles much smaller than that, and there are many variations, most of which give you better resolution numbers. We occasionally use other specifications when we need to say we met a specific target. The standard objectives I am quoting are Olympus Plan Acromats, different systems have different tube lenses which cause you to get a different magnification out of the same objective. That is why the NA is the important factor. Otherwise I would just use a 1m tube lens and get 5x higher magnification numbers to report similar to what we see with the paper microscope.
- EpicEng 13y ago
  Ok, that makes sense. We tend to use high NA objectives for our applications, and the light path is a bit longer than in standard scopes (though not too long as to introduce too much empty magnification.) shows how much I still have to learn about optical systems even though I've been writing control sofwtware for these things for almost five years now.

3 ms·

I work on digital microscope scanners and I have always thought that 1um was the general value for a 10x objective (because that is always what it is on scanner

by EpicEng 13y ago

chrisBob 13y ago
The resolution is given by 1.22λ/NA. λ can be rounded to 500nm and the NA of a standard 20x objective is .4 giving 1.5µm. This is good because I was worried you caught me just making things up for the internet. A 40x with a .65 NA gives just under 1µm resolution. Resolution is also a slightly fuzzy spec depending on the audience. I go with the Raleigh criteria: You can't distinguish between two particles separated by less than the resolution distance. You can however, see particles much smaller than that, and there are many variations, most of which give you better resolution numbers. We occasionally use other specifications when we need to say we met a specific target. The standard objectives I am quoting are Olympus Plan Acromats, different systems have different tube lenses which cause you to get a different magnification out of the same objective. That is why the NA is the important factor. Otherwise I would just use a 1m tube lens and get 5x higher magnification numbers to report similar to what we see with the paper microscope.
- EpicEng 13y ago
  Ok, that makes sense. We tend to use high NA objectives for our applications, and the light path is a bit longer than in standard scopes (though not too long as to introduce too much empty magnification.) shows how much I still have to learn about optical systems even though I've been writing control sofwtware for these things for almost five years now.