THORLABS WFS150, Руководство по эксплуатации

Страница: 29 / 123

27 Description
© <2007> ... Thorlabs GmbH
wavefront array which is displayed in a 3D diagram. All valid spot deviations
within the defined pupil region and the desired number of Zernike orders / modes
are input data to the Zernike fit that fits the measured wavefront using well-known
Zernike functions. Output data are Zernike coefficients which are displayed
numerically and within a bar graph panel. All or a few selected Zernike modes are
used for the wavefront reconstruction. Also the difference between measured and
fitted wavefront data is available.
3.1 Shack-Hartmann Functional Principle
The WFS150 / WFS150C Wavefront Sensor consists basically of a CCD camera
with a microlens array mounted in a defined distance in front of its sensor chip.
Each microlens generates a spot onto the sensor whereas the spot centroid
position depends on the wavefront gradient in front of the lens area.
Each microlens of the lenslet array collects the light falling onto its aperture and
generates a single spot on the detector plane (CCD camera) that is situated a
focal length behind the lenslets. The spot positions are straight behind the lenses
only in case the launched wavefront is plane and parallel to the plane of the
lenslets. We call these the
Reference Spot Positions or reference spotfield.
In the common case however, the current spot positions will be deviated in X and
Y direction, that is, every spot lies away from the optical axis z of its associated
microlens, separated by an angle
a.