THORLABS WFS20-14AR, Operation Manual

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Wavefront Sensor
2 Operating Principle
The Wavefront Sensor instruments comprise a CMOS camera and a microlens array that is
mounted at a defined distance in front of the camera sensor chip. Each microlens of the lenslet
array collects the light incident to its aperture and generates a single spot on the detector plane
(CMOS camera) that is located at a distance of one focal length behind the lenslets.
Each spot is centered behind the lens that generated it only if the incident wavefront is planar
and parallel to the plane of the lenslets. These are the
Reference Spot Positions, also known
as the Reference Spotfield .
In the case of a distorted wavefront incident on the sensor, the focal spot positions shift along
the X and Y directions, away from the optical axis Z of its associated microlens and the prede-
termined
Reference Spot . The displacement is described by the angle
a.
The above sketch shows that this deviation from the reference spot is caused by the deviation
of the wavefront incident angle on the microlens, or in geometrical terms: