Portable Optical Tweezers Kit
Chapter 3: Principles of Optical Tweezers
Page 10
MTN024417-D02
So far, the force was given as a function of
𝜃𝜃
which now has to be expressed in terms of
𝑟𝑟
and
𝛽𝛽
. Figure 5 shows a partial beam incident on the sphere with angle
𝜃𝜃
from the side.
The following statements hold true:
𝑋𝑋
= sin
𝜙𝜙 ∙ 𝑆𝑆
= sin
𝜃𝜃 ∙ 𝑅𝑅
(19)
and
sin
𝜙𝜙
=
𝑟𝑟 �𝑟𝑟
2
+
𝑟𝑟
2
⁄
(20)
𝑟𝑟
roughly corresponds to the focal length of the objective. Effectively, you can use the
objective’s working distance for this parameter.
Relation Between
𝒓𝒓
and
𝜽𝜽
.
6
Then,
𝜃𝜃
can be expressed as
𝜃𝜃
(
𝑟𝑟
) = arcsin
�
𝑆𝑆
𝑅𝑅
𝑟𝑟
√𝑟𝑟
2
+
𝑟𝑟
2
�
(21)
Summary of Contents for EDU-OT3
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