MEASUREMENT WITH AN OLYMPUS FILAR MICROMETER EYEPIECE OSM
( C a t a l o g #2-C790)
#2-C791)
1.
I n i n s t a n c e s where measurements w i t h a n e y e p i e c e micrometer
d i s k a r e n o t a c c u r a t e enough f o r t h e u s e r ' s p u r p o s e , a f i l a r
micrometer e y e p i e c e (OSM) should be employed. The f i l a r micrometer e y e p i e c e must be c a l i b r a t e d f o r e a c h o b j e c t i v e w i t h which
i t might be used. The c a l i b r a t i o n of t h e a r b i t r a r y f i e l d of
view s c a l e d i v i s i o n s and t h e e x t e r n a l f i l a r drum d i v i s i o n s i s
done a g a i n s t t h e known v a l u e s of a s t a g e micrometer s c a l e .
2.
The s t a g e micrometer i s a 1" X 3 " s l i d e w i t h a n e t c h e d s c a l e ,
u s u a l l y o f 100 e q u a l s m a l l d i v i s i o n s ; t h e e n t i r e s c a l e i s usua l l y 1 m i l l i m e t e r (1000 microns) long. Every f i f t h and t e n t h
d i v i s i o n i s u s u a l l y a somewhat l o n g e r v e r t i c a l l i n e t o e n a b l e
t h e u s e r t o c o u n t t h e s t a g e micrometer r e a d i n g s more r e a d i l y .
Every s m a l l d i v i s i o n i s e q u a l t o 1 0 m i c r o n s ; f i v e d i v i s i o n s
e a u a l 50 microns: t e n d i v i s i o n s e q u a l 100 microns. The
;<age s c a l e i s t h e known s c a l e of l e n g t h s .
(Some s t a g e micrometers a r e c a l i b r a t e d i n f r a c t i o n s of a n i n c h
r a t h e r t h a n m e t r i c a l l y ) . F i g . 1A, F i g . 1B
n
FIG. 1B
Each Small. D l v l ~ l o n ~ l ~
pvary Clv8 D l v I 8 l o n r a 6 0 ~ .
Evrry T r n Dlvlalonr 8 lo&
FIG.' 1A
OTAQE MICROMETER
Page 2
3.
The f i l a r micrometer eyepiece has an a d j u s t a b l e eye l e n s w i t h a
f i x e d s c a l e , 0 t o 8 i n t h e f i e l d of view. Also i n view, t h e r e
i s a p a i r of v e r t i c a l ( f i d u c i a r y ) l i n e s which move along t h e
f i x e d s c a l e as t h e e x t e r n a l drum i s r o t a t e d by t h e u s e r . Below
t h e f i d u c i a r y l i n e p a i r , t h e r e a r e i n t e r s e c t i n g X h a i r s which
t r a v e l a c r o s s t h e f i e l d of view simultaneously as t h e f i d u c i a r y
l i n e p a i r i s moved. The i n t e r s e c t i o n of t h e X h a i r s makes poss i b l e a c c u r a t e r e a d i n g s of t h e p o s i t i o n of t h e moving l i n e s
aboGe'them as t h e X h a i r s t r a v e l a c r o s s t h e o b j e c t being measured.
Fig. 2
4.
A t r i g h t a n g l e s t o t h e f i l a r eyepiece and a t t a c h e d o u t s i d e t h e
eyepiece, t h e r e i s a r o t a t a b l e drum, d i v i d e d i,nto 100 e q u a l d i v i s i o n s ; each t e n t h d i v i s i o n i s numbered; each f i f t h d i v i s i o n l i n e
i s s l i g h t l y longer t o make r e a d i n g s e a s i e r . A s t h e e x t e r n a l drum
i s t u r n e d by t h e o p e r a t o r , t h e f i d u c i a r y l i n e s i n t h e f i e l d of
view a r e a c t u a t e d t o move a c r o s s t h e f i x e d s c a l e i n t h e f i e l d of
view; simultaneously t h e i n t e r s e c t i n g X h a i r s t r a v e l a c r o s s t h e
f i e l d of view. When t h e f i d u c i a r y l i n e s a r e e x a c t l y on 4 of t h e
f i x e d s c a l e and t h e drum i s a t 0, t h e i n t e r s e c t i o n of t h e x h a i r s
i s e x a c t l y i n t h e c e n t e r of t h e f i e l d of view. Fig.3
. -
FIG.' 3
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Each complete r o t a t i o n of 100 s m a l l d i v i s i o n s o f t h e e x t e r n a l
drum moves the X h a i r s and t h e f i d u c i a r y l i n e s t h e e q u i v a l e n t
of 1 whole s p a c e on t h e f i e l d of view f i x e d s c a l e . The drum
d i v i s i o n s a r e r e a d a g a i n s t a n i n d e x l i n e engraved on t h e outs i d e of t h e f i l a r eyepiece.
-
F o r example, 2 f u l l t u r n s of t h e drum and a p a r t i a l t u r n of
37 s m a l l d i v i s i o n s e q u a l s 237 s m a l l d i v i s i o n s of t h e drum.
For e a s e of c a l i b r a t i o n , it i s convenient t o s t a r t a measurement w i t h t h e f i d u c i a r y l i n e s s t r a d d l i n g 4 on t h e f i x e d s c a l e
i n t h e f i e l d of view and the e x t e r n a l drum r e a d i n g 0.
5.
The t a s k i s t o c a l i b r a t e t h e a r b i t r a r y v a l u e of e a c h s m a l l
d i v i s i o n of t h e e x t e r n a l drum (100 of t h e s e i s e q u a l t o one
whole m a c e on t h e f i x e d s c a l e i n t h e f i e l d o f view) a g a i n s t
<he k n o k v a l u e s o f e a c h s m a l l d i v i s i o n o f t h e s t a g e micrometer
s c a l e (10 microns e a c h ) FOR EACH OBJECTIVE. The c a l i b r a t i o n
f o r each o b j e c t i v e i s recorded f o r f u t u r e use.
Thus, when
measuring a n unknown l e n g t h of a specimen, t h e f i l a r micrometer ca; b e used w i t h o u t need f o r a known s t a g e s c a l e .
~-
Procedure Usinq a 10X O b j e c t i v e a s an Example
A.
P l a c e t h e s t a g e micrometer on t h e microscope s t a g e and f o c u s
as u s u a l u n t i l t h e l i n e s appear sharp. Using t h e mechanical
s t a g e , c e n t e r t h e s t a q e s c a l e i n t h e f i e l d o f view s o t h a t t h e
v e r t i c a l l i n e s are o r i e n t e d North-South and t h e s t a g e s c a l e
c e n t e r e d i n t h e f i e l d of view from "9 o ' c l o c k t o 3 o ' c l o c k m
positions.
B.
Remove t h e v i s u a l e y e p i e c e from t h e microscope body t u b e ( f o r
a b i n o c u l a r , u s e t h e e y e t u b e which i s n o t a d j u s t a b l e ) .
C.
Hold t h e f i l a r e y e p i e c e toward a b r i g h t l i g h t . Using t h e adj u s t a b l e e y e l e n s of t h e e y e p i e c e , f o c u s t h e f i e l d of view
f i x e d s c a l e ( 0 - 8 ) and X h a i r s s o t h a t t h e y appear sharp.
D.
I n s e r t t h e f i l a r eyepiece i n t o t h e microscope tube. Without
changing t h e f i l a r eyepiece f o c u s , o r i e n t t h e f i l a r eyepiece
s o t h a t t h e f i x e d eyepiece s c a l e i n t h e f i e l d of view (0 t o 8 )
i s East-West; 0 on t h e l e f t , 8 on t h e r i g h t . Without changi n g t h e adjustment of t h e e y e l e n s of t h e f i l a r micrometer,
t i g h t e n t h e r e t a i n i n g screw of t h e f i l a r eyepiece s o t h a t it
i s f i x e d t o the microscope body tube. The s c a l e i n t h e f i e l d
of view w i l l be seen approximately extending from "10 o l c l o c k
t o 2 o l c l o c k " p o s i t i o n . If t h e drum i s t u r n e d s o t h a t t h e
f i d u c i a r y p a i r of l i n e s i s a t 4 i n t h e f i e l d of view and t h e
e x t e r n a l drum r e a d i n g i s a t 0 , t h e X h a i r s w i l l be seen i n
t h e , c e n t e r of t h e f i e l d of view.
E.
~f t h e microscope being employed i s t h e Vanox o r t h e BH-2, an
a d a p t e r ( C a t . #B-0670) must be used. The f i l a r eyepiece has
t o be f i x e d by r e t a i n i n g screw t o the a d a p t e r . Then proceed
a s i n C and D above, t h i s t i m e u s i n g t h e a d a p t e r r e t a i n i n gscrew *to.be t i g h t e n e d t o t h e microscope tube:
F.
Using t h e mechanical s t a g e , move t h e s t a q e micrometer s c a l e
s o t h a t a longer v e r t i c a l l i n e ( a t e n t h d i v i s i o n ) i s o r i e n t e d
North-South and i s e x a c t l y i n t e r s e c t e d by t h e t r a v e l i n g X h a i r
of t h e f i l a r ; t h e moveable f i d u c i a r y l i n e s a r e a l s o o r i e n t e d
North-South.
G.
S t a r t i n g w i t h t h e e x t e r n a l drum a t 0 and t h e X h a i r i n t e r s e c t i n g t h e longer v e r t i c a l l i n e of t h e s t a g e s c a l e , r o t a t e t h e
e x t e r n a l drum toward t h e u s e r (going from 0 upwards). While
looking a t t h e X h a i r s , move t h e X h a i r s s o t h a t t h e X h a i r s
and f i d u c i a r y l i n e s t r a v e l a d i s t a n c e of 1 0 small spaces on
t h e s t a g e s c a l e . Record t h e " s t a r t i n g " number on t h e f i x e d
s c a l e and t h e " f i n i s h i n g " number on t h e f i x e d s c a l e , e.g.,
4 t o 5; a l s o r e c o r d t h e number on t h e e x t e r n a l drum.
e.g.
1 whole space on t h e f i x e d s c a l e - d100
s m a l l drum
i n t h e f i e l d of view
ivisions
39 on drum reading = 39 small drum d i v i s i o n s
139 s m a l l drum d i v i s i o n s
Total
--
# Small spaces on s t a q e s c a l e
# T o t a l drum d i v i s i o n s
10 Small spaces on s t a g e s c a l e = 10 x l o p
139 T o t a l drum d i v i s i o n s
139
100 Microns
K =
= 0 . 7 1 9 ~ = Value of each s m a l l drum
139
d i v i s i o n f o r this o b j e c t i v e
K =
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E y r p l r s r Flxrd- 8 s r l r
~ n u c ~ r LIMB
rr
mvklon L h r of t h 8 t r 0 r Mlorm.rtrr
For this objective,
One small drum division = 0.719 microns;
One whole space in the fixed eyepiece scale = 71.9 microns
If the user measures a specimen and finds that it takes two
whole fixed spaces in the field of view and 27 drum divisions
of the filar to traverse the specimen, then the specimen length
would be 227 C200+27) X 0.719~ -163.2 microns for this objective and specimen.
Page 6
H.
For t h e 4 0 X O b j e c t i v e , f o r example: Only a l i m i t e d segment of
t h e s t a g e micrometer s c a l e w i l l u s u a l l y be v i s i b l e a t t h i s magn i f i c a t i o n . Proceed as follows f o r t h i s o b j e c t i v e :
1.
Turn t h e e x t e r n a l drum of t h e f i l a r s o t h a t it i s a t 0.
2 . - Using t h e mechanical s t a g e , a l i g n t h e s t a g e s c a l e
s o t h a t t h e X h a i r i n t e r s e c t i o n i s superimposed on
one of t h e longer v e r t i c a l l i n e s of the s t a g e s c a l e .
Read t h e " s t a r t i n g " number on t h e eyepiece f i x e d
s c a l e . Rotate t h e f i l a r drum u n t i l t h e X h a i r s t r a v e l
5 s m a l l spaces on t h e s t a s e s c a l e . Now read t h e
" f i n i s h i n s " number on t h e eyepiece
f i x e d s c a l e . Add
- t h e numbe; reading on t h e o u t s i d e drum. This g i v e s
t h e t o t a l number of f i l a r small d i v i s i o n s t r a v e l e d .