Difference between revisions of "Aligning the optical trap"
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Revision as of 14:51, 22 March 2013
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Instrument overview
Block diagram
A high-NA objective lens (L1) performs the dual functions of imaging the sample and focusing the trapping laser. L1 is a 1.25 NA, 100X, infinity corrected, oil immersion objective lens with a working distance of 0.65 mm. Its back aperture is 5mm in diameter.
L7 focuses an image of the LED illuminator in the backplane of the condenser lens L2 to provide collimated transillumination in the sample plane. L2 is a .25 NA, 10X, infinity corrected objective lens with a 7 mm working distance. Steering mirror M1 and tube lens L3 complete the imaging path. L3 is a 1" diameter, uncoated plano convex lens with a focal length of 200 mm. L3 forms an image of the sample plane on the detector of a CCD camera placed at a distance of 200 mm. (For best performance, the distance between L3 and the CCD imager must be accurate.)
The trapping laser beam emerges from a fiber coupler with a diameter of approximately ??mm. Lenses L4 and L5 (focal lengths ?? and ??, respectively) implement a Galilean telescope that expands the beam by a factor of 4. To minimize aberrations and reflections, L4 and L5 are IR-coated achromatic doublet lenses. Dichroic mirror D1 deflects the collimated trapping beam toward L1.
Physical layout
Setup and alignment
Remove the optics
Collimating and adjusting the fiber port
Initial laser alignment
Beam expander coarse adjustment
Condenser adjustment
Connecting the piezo stage
Fine adjusting the beam expander
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OTKB software
Starting the software
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Calibration
Measuring R by scanning a stuck bead
PSD method
Equipartition method
Stokes method
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