Leica DM LSP Bedienungsanleitung Seite 10

Crossed polarizers
The DIN and ISO standard vibration directions
are indicated on the microscope (sticker).
If the specimen contains many non-birefringent
or opaque particles, the polarizer is frequently
turned out of the crossed position by a few
degrees so that these particles show up at least
faintly (they remain dark when the polarizers are
exactly crossed). It is not customary to examine
specimens with the polarizers parallel, as this
method of identifying birefringence is not sensi-
tive enough.
Change in brightness when birefringent objects
are rotated
When the stage is rotated, the brightness of
birefringent (anisotropic) objects changes peri-
odically. During a full rotation the object dis-
appears four times after each 90° interval. The
four dark positions are called extinction or nor-
mal positions. Exactly between each of these
extinction positions the object can be observed
with maximum light intensity. These are the four
diagonal or 45° positions. In the extinction posi-
tions the object vibration directions run parallel
to the transmission directions of the polarizers,
at maximum intensity the object vibration direc-
tions represent the angle bisectors of the polar-
izer directions. The crosslines in the (right-hand)
eyepiece of polarized light microscopes can
either be aligned at N – S/E – W, i. e. in the polar-
izer directions, or at 45° angles, i. e. correspond-
ing to the object vibration directions in the
diagonal position.
10
λ and λ/4 compensator
Depending on the microscope model, the quar-
ter- and whole-wave compensators are either
slotted in the compensator slot (43.20) or above
the polarizer (43.10; 28.2) or in the light ring slot
(CLP/PH) or integrated in the condenser disc
(UCLP) (9.6). When a compensator is engaged,
the phase difference is increased or decreased
(see Fig. 45). The vibration direction γ (i. e. corre-
sponding to the greater refractive index n
be determined from the colour changes.
200
– λ
400
600
800
+ λ
1000
1200
1400
1600
Fig. 45 Interference colours in relation to phase difference, or
to thickness and colour change for the addition and subtraction
position of a whole-wave and a quarter-wave compensator
) can
γ
Black
Lavender gray
Gray blue
Yellowish-white
Vivid yellow
Red-orange
λ
Deep red
– –
4
Indigo
λ
Sky blue + –
4
Greenish blue
Light green
Pure yellow
Orange red
Dark violet red
Indigo
Greenish blue
Sea green
Greenish yellow
Flesh color
Crimson
Matt purple