Portable Optical Tweezers Kit
Chapter 5: Setup and Adjustment
Page 58
MTN024417-D02
5.5. Trapping, Microscope Focus, and Final Alignment
The table is now set to trap microscopic particles.
Step 1: Preparation
•
Switch on your computer and start the camera software (see Section Figure 32).
•
Set the velocity of the motors to 0.02 mm/s (see Section 5.2.4, you may increase
the speed when you have trapped a particle).
•
Set the LED lighting to maximum (see Section 5.2.1).
•
Switch on the laser with a diode current of 95 mA (or the diode current you
measured to obtain 40 mW of output power, see Section 5.2.2)
Step 2: Sample
•
Prepare a sample with polystyrene-beads (see Section 6.1).
•
Place the sample positioning table as low as necessary with the aid of the
micrometer screw for the Z direction. Make sure to leave enough space to avoid
a collision with the objective when the sample slide is inserted into its holder.
•
Place the sample in the holder with the selected well under the objective.
Step 3: Approach
•
Raise the sample positioning table with the micrometer screw and pay close
attention to the camera image on the monitor of your computer. Note that the
objective’s working distance is below 0.5 mm due to the high numerical aperture.
•
As you raise the sample, you will see a distorted red laser spot forming on the
monitor. This is not the sample, but rather the top of the cover glass. Continue
slowly raising the sample. The laser spot will disappear and reappear. The
second time you see the spot indicates the bottom of the cover glass. Raise the
sample higher, and the spot will disappear and reappear again. The third time
you see the spot indicates that the laser focus is in the sample. At this point, the
focus is at the right level. Figure 43 shows a schematic representation of the
situations.
Please note that reflections of the laser may occur. In the camera image, these will appear
with varying diameter (small spots or larger shapes). These are not a sign of bad
adjustment and can be ignored.
Summary of Contents for EDU-OT3
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