THORLABS WFS150, Operation Manual

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35 Operating Instruction
© <2007> ... Thorlabs GmbH
The C-Mount threading on the face of the CCD camera allows with the help of an
adapter (Thorlabs SM1A9) for the convenient mounting of ND filters, to help
prevent the saturation of CCD pixel, and lens tubes to reduce scattered light and
to allow for the mounting of additional optical components.
Beam Size
The active area on the CCD camera chip can be selected (see
Camera Settings Setup ) in order to adapt it to the actual beam size. Otherwise, a
beam much smaller than the sensor area will illuminate only the microlenses at
the center and no wavefront data can be retrieved from the ambient area. Also
the measurement speed is increased when the camera image size is reduced to
fit the real beam diameter.
A beam size larger than the available aperture (5,95 x 4,76 mm) of the WFS150 /
WFS150C Wavefront Sensor can be adapted using beam expanders (Thorlabs
BE01 - BE20 series).
Beam Alignment
Align the Wavefront Sensor so that the beam to be analyzed launches the
instrument perpendicular to its front face. In some cases a small tilt angle out of
that position can be helpful to prevent unwanted back reflection into the
measurement setup.
Direct the beam to be analyzed into the center of the entrance aperture of the
Wavefront Sensor. Although an off-center beam can also be measured as long
as it is not truncated by the active sensor area it is recommended to adjust the
beam to be measured so that it hits the center of the Wavefront Sensor. Verify
this adjustment by checking the power density distribution displayed within the
Beam View Panel . Enable the Beam View options ' Show Image Axes ' and
' Show Beam Diameter ' in order to visualize the beam position and size with
respect to the analyzed sensor area.