4
on any two opposite sides of the
qpod 2e
. Put
black plastic blanks from the
qpod 2e
accessory kit
in the other two optical ports. One lens collimates
the output from the source fiber into a beam about
5 mm in diameter. The beam passes through the
sample and is then focused on the collection fiber.
A collimating lens assembly contains a single 6 mm
diameter, 12 mm focal length, broadband AR-
coated, fused silica lens whose principal point is
located 12 mm from the end of the fiber.
Optics to measure fluorescence
Figure 2 -
Fluorescence configuration
As shown in
Figure 2
, to set the
qpod 2e
up for
fluorescence measurements insert an imaging lens
to focus light from a source fiber into the center of
the sample cuvette. Place another imaging lens at
90° to the source lens images the illuminated
volume onto a collection fiber. To enhance
collection efficiency, spherical mirrors may be place
on the remaining positions of the
qpod 2e
. One
opposite the excitation fiber focuses the excitation
source back through the sample and another
opposite the collection lens focuses extra emitted
light back through the sample to roughly double the
amount of emitted light collected.
An imaging lens assembly contains two ½-inch
diameter, 30 mm focal length, broadband AR-
coated fused silica lenses. The principal point of
one lens is located 30 mm from the fiber and the
principal point of the second lens is located 30 mm
from the center of the cuvette. Thus, the imaging
lens pair creates an image of the fiber end, without
magnification, in the center of the cuvette, or
images the illuminated volume on a collection fiber.
Inserting a lens into the
qpod 2e
Figure 3
- Components of a lens assembly
1.
Use the 5/64-inch hex screwdriver from the
qpod 2e
accessory kit to loosen the set screw
(
Figure 3
).
2.
Remove the silver sleeve with a black end
piece from the lens assembly. Set it aside.
3.
Screw the empty optical assembly all the way
into the appropriate position in the
qpod 2e
. If
you are using an accessory component such as
a filter holder or polarizer. First place the
accessory in the
qpod 2e
. As you screw in the
empty lens assembly the accessory will fit over
its end and then snap into place.
4.
Look for the location of the set screw. If it is in
a difficult position to reach, you may wish to
remove the three fiber steering screws, rotate
the end of the optical assembly until the set
screw is accessible, and reattach the alignment
