Chapter 3 Otkb-Fl; Introduction; Module Weight And Dimensions; Otkb-Fl Design - THORLABS OTKB-FL User Manual

Optical Trap Kit Fluorescence Light Unit
OTKB-FL
Chapter 3
3.1.

Introduction

Thank you for choosing Thorlabs' fluorescence module for your imaging solution. Our OTKB-FL modules provide a
simple solution to empower our OTKB system with fluorescence imaging capabilities.
A fluorescence microscope basically must provide the appropriate optical wavelength necessary to excite the
selected fluorophore, and it must have the ability to capture the radiation emitted by the flurophore when it returns
to a lower energy state. (NB: The emitted radiation will be at a longer wavelength (lower energy) than the absorbed
excitation radiation due to energy loss in the process.)
There are four main components needed for a fluorescence microscope to work. They are fluorophores, excitation
light source, dichroic mirror, and detectors. In our modules, we are able to tailor the various filter set suitable to
meet your imaging needs. Our OTKB-FL is provided without a light source for users who wish to provide their own
light source; the module includes a receptacle for a Ø3 mm liquid light guide (such as Thorlabs item number
LLG0338-4). The excitation light source can be a broadband LED or a multi channel LED light source like CHROLIS-
C1. We use excitation filters to select the appropriate wavelength for exciting the fluorophore, and a dichroic mirror
is inserted in the beam path to separate the excitation and the emission light paths. Finally, an emission filter is
placed in front of the imaging device to allow only the desirable emission light to be captured.
3.2.

Module Weight and Dimensions

•
Dimension: 21 cm x 15 cm x 13.5 cm
•
Weight: < 1 kg
3.3.

OTKB-FL design

Our modules are designed according to the experimental setup used
for epi-fluorescence microscopy, in which both the excitation and
emission light travel through the microscope objective. By carefully
choosing the appropriate filters and mirrors for a given application,
the signal-to-noise ratio can be maximized. As shown in Figure 1,
three types of filters are used to maximize the fluorescence signal
while minimizing the unwanted radiation. Each optical element is
discussed below.

3.3.1. Excitation Filter

The excitation filter only allows a narrow band of wavelengths to pass
through it. For example, as shown in Figure 2, the MF475-35
excitation filter has a bandpass region of 458 nm -492 nm; this
corresponds to >85% transmission for the fluorescein isothiocyanate
(FITC). Incident radiation outside of this range is either partially (for
regions near the transmission region) or totally (for regions further
from the bandpass region) blocked by the filter.

3.3.2. Dichroic Mirror

As shown in the experimental setup in Figure 1, the dichroic mirror of our modules is used to separate the
excitation and emission light paths. The transition wavelength value associated with each mirror indicates the
wavelength that corresponds to 50% transmission. For example, as shown in the transmission versus wavelength
Rev D, May 20, 2020
Chapter 3: OTKB-FL
Figure 1 Experimental Setup
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