Arrangement for generating a differential interference contrast image
An assembly for the generation of a differential interference contrast image (DIC) of an object in an imaging plane, comprising a radiation source; a Köhler illuminating optical assembly for illuminating the object with light from the radiation source; an objective for imaging the object plane in an imaging plane, wherein the objective is provided with an exit pupil and an entrance pupil, and wherein the entrance pupil of the objective is positioned in the illuminating pupil of the Köhler illuminating optical assembly; and a component for the generation of an interference is characterized in that the component for the generation of an interference is positioned in the exit pupil of the objective, and the component for the generation of an interference is formed by an amplitude filter with an amplitude transmission factor F DIC (x,y), which complies with the equation: 2 · F DIC ( x , y ) = F + ( x , y ) · ⅇ + ⅈ P 0 + F - ( x , y ) = 2 · T 0 · cos ( P max ( - x · sin φ + y · cos φ ) + P 0 2 ) · ⅇ + ⅈ P 0 2 wherein F DIC (x,y) is a functional expression for the description of the amplitude filter transmission and the phase of the amplitude filter depending on the coordinates x and y.
1. An assembly for the generation of a differential interference contrast image (DIC) of an object provided in an object plane in an imaging plane, comprising:
(a) a light emitting radiation source;
(b) a Köhler illuminating optical assembly for illuminating said object with said light from said radiation source, said Köhler illuminating optical assembly having an illuminating pupil;
(c) an objective for imaging an object plane in an imaging plane, wherein said objective is provided with an exit pupil and an entrance pupil, and wherein said entrance pupil of said objective is positioned in said illuminating pupil of said Köhler illuminating optical assembly; and
(d) a component for the generation of an interference of light waves;
characterized in that
(e) said component for the generation of said interference of light waves is positioned in said exit pupil of said objective, and
(f) said component for the generation of said interference of light waves is formed by an amplitude filter with an amplitude transmission factor F DIC (x,y), which complies with the equation:
2
·
F
DIC
(
x
,
y
)
=
F
+
(
x
,
y
)
·
ⅇ
+
ⅈ
P
0
+
F
-
(
x
,
y
)
=
2
·
T
0
·
cos
(
P
max
(
-
x
·
sin
φ
+
y
·
cos
φ
)
+
P
0
2
)
·
ⅇ
+
ⅈ
P
0
2
wherein
x,y: coordinates in said exit pupil plane
F DIC (x,y): functional expression for describing said amplitude filter transmission and a phase of said amplitude filter as a function of x and y
t(x,y): variable, real portion of said amplitude transmission factor of said amplitude filter with
t
(
x
,
y
)
=
T
0
·
cos
(
P
max
(
-
x
·
sin
φ
+
y
·
cos
φ
)
+
P
0
2
)
T(x,y): Transmission degree of said amplitude filter (if F* DIC (x,y) designates the conjugate-complex of F DIC (x,y), then
T ( x,y )= F DIC ( x,y )· F* DIC ( x,y )= t 2 ( x,y )
F + (x,y): “positive” portion of F DIC , with F + (x,y)=T 0 ·e +iP max ·(−x·sin φ+y·cos φ)
φ: azimuth direction angle of the effect of the DIC in said exit pupil plane
P(x,y): phase distribution of said amplitude filter with
P
(
x
,
y
)
=
arg
(
F
DIC
)
=
{
P
0
2
-
π
≤
2
P
max
·
(
-
x
·
sin
φ
+
y
·
cos
φ
)
+
P
0
≤
π
P
0
2
+
π
π
≤
2
P
max
·
(
-
x
·
sin
φ
+
y
·
cos
φ
)
+
P
0
≤
3
π
F − (x,y): “negative” portion of F DIC , with
F + ( x,y )· F − ( x,y )= T 0 ·e +iP max ·(−x·sin φ+y·cos φ) ·T 0 ·e −iP max·(−x·sin φ+y·cos φ) =T 0 2
P 0 : constant, real phase offset of said amplitude filter F DIC (x,y)
T 0 : constant, real amplitude transmission factor of F DIC , or F + and F − , respectively
P max : constant, real maximum phase of F + or F − , respectively.
2. The assembly of claim 1 , wherein said amplitude filter is an intensity filter comprising a substrate having a substrate thickness and wherein said substrate has the same substrate thickness in every point.
3. The assembly of claim 1 , wherein said amplitude filter generates an amplitude transmission distribution, and wherein said amplitude filter is coated with aluminum or any other suitable absorbing material.
4. The assembly of claim 1 , wherein said amplitude filter is provided with a knife-edge extending in said exit pupil, which does not let any radiation from said radiation source pass on one side and blocks said radiation in a portion of said exit pupil and which lets the maximum intensity of said radiation pass on the other side in the remaining portion of the exit pupil.
5. The assembly of claim 4 , wherein said knife-edge is positioned in such a way that at least half of said radiation passes with maximum intensity.
6. The assembly of claim 1 , wherein the zero diffraction order of the light diffracted by the object passes with maximum intensity.