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how to calculate diameter at 40x?

hzma

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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!
 
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glorybrian

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  1. Non-Student
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

Please check assumption.
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.
 
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torero

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Mar 15, 2006
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north of the border
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

Please check assumption.
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.

Thanks. That link is quite helpful.

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
 
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