THORLABS WFS20-14AR, Operation Manual

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Wavefront Sensor
5.3 Beam setup using the Software
Prior to making measurements, several aspects of the input beam and a few related Wavefront
Sensor settings should be reviewed and adjusted as necessary. The following sections provide
guidance on aligning the input beam, as well as configuring the system for different beam sizes
and power levels.
5.3.1 Beam Size and Alignment
Beam Size
Use the software to set the active area of the CMOS camera chip to include the full beam while
excluding as much of the unilluminated sensor area as possible (see
Camera Settings Setup
). The unilluminated region of the sensor provides no information about the beam's wavefront.
Measurement speed will increase by excluding this region from the active area, as speed in-
creases with reduced image size.
Beam sizes larger than the available aperture (7.20 mm x 5.40 mm for WFS20; 11.34 mm x
7.13 mm for WFS30 and 11.26 mm x 11.26 mm for WFS40) can compensate for by using a
beam expander (Thorlabs GBE02 through GBE20 series) used in reverse.
Alignment
Position the Wavefront Sensor so that the beam is normally incident on the sensor. To reduce
unwanted reflections back into the source, rotate (tilt) the Wavefront Sensor slightly from this
alignment.
Align the incident beam to the center of the entrance aperture of the Wavefront Sensor. An off-
center beam can be measured as well, provided the full beam is contained within the active
sensor area. However, aligning the beam to the center of the sensor area is recommended.
Verify this alignment by checking the power density distribution displayed in the
Beam View
Panel . Enable options 'Show Image Axes' and 'Show Beam Diameter' in order to visualize
the beam position and size with respect to the analyzed sensor area.
Alternatively, you can check the correct beam position using the Spotfield Panel . Enable the
diagram options ' Show Image Axes ' and ' Show Pupil '.
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