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64
9. Contrast methods for Leica DM4000 B/DM4500 P/DM5000 B
• Insert the λ/4 plate (69.5) into the tube slot.
• Insert the λ/4 plate (69.1) into the receptacle
located on top of the polarizer and rotate it
until a specimen-free field of vision appears
at its maximum extinction position (make sure
to cross the polarizers precisely before doing
this).
Compensators for quantitative measurements
Adjustable compensators are used to obtain ex-
act measurements of path differences.
To obtain the usual specimen thickness, d, and
the measured path difference, gamma (Γ), the
birefringence ∆n’ is calculated according to the
following formula:
Γ = d x ∆n’ [nm] or ∆n = ––
When obtaining measurements, the compensator
is inserted into the compensator slot and adjust-
ed until the specimen position being measured is
at the maximum extinction position. For this, the
specimen must be pitched at a diagonal.
For HC P tube optics, use an iris diaphragm to
mask out the measuring points.
Detailed information can be found in the instruc-
tions for the compensator.
The following compensators are available:
Elliptical compensator based on Brace-Köhler
techniques 69.9)
Rotating compensator with compensator plate
and a path difference of approx. λ/10. Measure-
ments can be obtained in white or monochro-
matic light with a measurement range of up to
approx. 50 nm.
Elliptical compensator based on Sénarmont
techniques 69.6)
(λ/4 plate in subparallel position)
Measurements are obtained in monochromatic
light (546 nm), which requires an analyzer that
can be rotated 360°. In most cases, the compen-
sator is used to measure path differences of up
to 1 order. But higher path differences can be
measured. However, when doing so, the com-
pensator does not provide the entire path differ-
D
Γ
Fig. 69 Compensators
1, 2 λ/4 u. λplate. For polarizing microscopes only: 3 λ/4 u. λplate for the 8x turret disk, 4, 5 λ/4 u. λplate for the tube slot,
6 Revolving λ/4 plate (Sénarmont compensator), 7 Quartz wedge, 8 Tilt compensator, 9 Brace-Köhler compensator
1
2
3
4
5
6
7
9
8