

How to use Stage & Ocular Micrometer
togother for Calibration

I want to measure the sample size under the microscope,
Should I use Ocular Micrometer？
or Should I use Stage Micrometer？ 


To put it simply

● 
An ocular micrometer is used for measuring the size of objects 
● 
The stage micrometer is used for calibrating the ocular micrometer. 

(for more accurate measurement) 

■ How to Use an Ocular Micrometer 
When an ocular micrometer is set correctly inside the eyepiece, it should
enable to see a sample
and an micrometer scale simultaneously when you look through a microscope.
By determining
single pitch length of an micrometer scale, you will be able to measure the actual sample size. 
** Under the microscope, the single pitch length of an micrometer changes
as magnification of objective lens is changed.
Formula is :
Ocular Micrometer's Pitch Length (under the microscope) =
[Actual Micrometer Pitch Length］ ÷ ［Objective Lens Magnification］ 
● 
Below explains the measurement of a glomeruli (of the kidney) with following
two premises.
1. Ocular micrometer model XY11 is used. XY11 has 0.1mm pitch (100μm)
2. Objective lens has a 20x magnification. 


● 
Applying these numbers to above formula, one pitch of ocular micrometer
in this scenario
should be equal to 5.0μm (= 100μm ÷ 20). Since the glomeruli spans 23 pitches on the horizontal scale and 22 pitches on the vertical scale on micrometer,
it measures 115μm (5μm x 23) by 110μm (5μm x 22). 



Obj Lens
Mag 
Magnified Pitch Length
10mm /100 divisions / pitch 0.1mm is used 
5 x 
20μm (= 100μm ÷ 5) 
10 x 
10μm (= 100μm ÷ 10)

20 x 
5μm (= 100μm ÷20) 
40 x 
2.5μm (= 100μm ÷ 40） 
50 x 
2μm (= 100μm ÷ 50) 
100 x 
1μm (= 100μm ÷ 100) 

■ How to Use an Ocular & Stage Micrometer for Calibration 
Generally, the objective lens magnification is off by a small margin.
The purpose of the stage micrometer is to determine this subtle magnification
error in an objective lens.
The process below should enables measurement with greater precision. 
● 
First, position stage and ocular micrometer in a way both scale are lined
up complete parallel
(to derive correct and accurate magnification from error margin) 


● 
Below illustrate stage micrometer NOB1 (1mm/100 divisions = 10μm pitch) and
an ocular micrometer S11 (10mm/100 divisions = 100μm pitch).
objective lens magnification is at 20x. 


● 
If magnification rate is correct, 10 pitches of stage micrometer should
be equal to 20 pitches (2000μm) of an ocular micrometer (=[1 pitch of ocular
micrometer is 10μm] x 10 pitches x [Objective lens x20] )Instead, in below
diagram, 10 pitches of stage micrometer shows equals to 21 divisions of
ocular micrometer,therefore it can be calculated that magnification of
objective lens is x21. 



● 
To achieve the calibrated measurement of the sample, multiply the measured
value of the sample by the labeled magnification of the objective lens
divided by the actual magnification ratio.
(Ex. Calibrated measurement of sample = measurement of sample × labeled magnification ratio ÷ actual magnification ratio) (Calibration ratio = 20/21 = 0.95) 





How to Install Ocular Micrometer
An ocular micrometer is a glass disk with ruled scale on the surface which
is etched in chromium.
Please insert it into the eyepiece with written surface facing to objective
lens (downward on below image) 

By JIS standard, a small error margin is accepted for magnification of object lens. It is possible to determine the error margin and enables measurement with better accuracy by using Stage Micrometer, together

★Image above is typical eyepiece lens. Ssize and shape may slightly different
for each models.
** some of the unique designed eyepiece requires special treatment for
insertion. 

■ How to identify front and reverse side of ocular micrometer. 
Micrometer (scale and numbers) is printed on the glass with chrome.
When printed side is identified, insert ocular micrometer to eyepiece fixing bracket
with printed side facing downward (toward objective lens  refer also
to above installing instruction)
Here explains how to identify front (printed side) and reverse side. 
1. 
Shed light on the micrometer and 

let it reflects in a way that printed 

numbers and scale will be 

turned silver. 

Unable to identify sides without 

the reflection of light. 

** To generate enough reflection, large area lighting is recommended 


** Eyepieces lens can be used as loupe and it helps you for installation 
2. 
When there is no shade, 

it is reverse side 




2. 
When there is shade, 

it is fron side (printed side) 



