how to calculate diameter at 40x?

hzma

Member
10+ Year Member
5+ Year Member
If i have a scope that has a 22 x eyepiece, and with the 40x objective (olympus), how do i calculate the diameter of the field? googled it but wasn't much help. Oh n supposing i don't have an eyepiece with the scale thing. thanks in advance!

Torsed

Deo Vindice.
10+ Year Member
Shouldn't the manufacturer have data on this. Where did you get a 22x? I don't recall seeing those ever. Maybe its a specialized scope for the techs or something, but you never know with the Japanese.

glorybrian

New Member
10+ Year Member
5+ Year Member
http://www.olympusmicro.com/primer/anatomy/oculars.html

Eyepiece: 10X
Objective: 40X
Then
Viewfield Diameter = (FN) / (M(O) x M(T))
FN = 22
M(O)=40
M(T)= 1.25 or 1

Then Diameter
0.44 mm for M(T)=1.25
0.55 mm for M(T)=1

If the scope has micrometer, then measure with any line by moving one side to another.

Otherwise, you can buy dial gage and attach to the stage, then measure.

10+ Year Member
5+ Year Member
Thanks!

torero

Member
10+ Year Member
http://www.olympusmicro.com/primer/anatomy/oculars.html

Eyepiece: 10X
Objective: 40X
Then
Viewfield Diameter = (FN) / (M(O) x M(T))
FN = 22
M(O)=40
M(T)= 1.25 or 1

Then Diameter
0.44 mm for M(T)=1.25
0.55 mm for M(T)=1

If the scope has micrometer, then measure with any line by moving one side to another.

Otherwise, you can buy dial gage and attach to the stage, then measure.

One thing I do not know is whether or not my scope has tube lens magnification.
I have an Olympus BX45 with an adjustable (tilting) observation tube. Anyone know if these scopes have tube lens magnification?

The other question I have is how are people counting mitoses per square mm in melanomas?

I have 10X eyepieces with a field number of 22, and think the viewfield AREA is close to 1 square mm using a 20X objective.

The way I calculated this is as follows:

Viewfield diameter= field number/ objective magnification x tube lens magnification
Viewfield diamgeter= 22/20 = 1.1 mm, assuming the lens magnification is 1

Area in a circle= 3.14 (radius)2
Area in a circle= 3.14 (.55)2 = 0.93 mm2

Pretty close to 1 mm2

The problem is if my scope has a tube lens magnification of 1.25X, then the viewfield area with a 20X objective would be of .6mm2 Quite a significant difference from 0.93 mm2

So is everyone just eyeballing a square mm, is there a graticule available for this, or how are you guys counting mitoses in those melanomas?

Thanks