Wavefront sensor having a lenslet array as a null corrector
AssigneeHughes Danbury Optical Systems, Inc.
InventorWilliam Zmek
Life of this patent
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Abstract
A wavefront sensor (10) includes a radiation sensor (2) and an array (12) of lenslets (12A) that are optically coupled to the radiation sensor. The array of lenslets has a radiation receiving surface for receiving an incident wavefront and for focussing the wavefront at a plurality of focal positions upon the radiation sensor. Each of the lenslets comprises a diffractive optical element having an optical center that is located at a predetermined point for inducing an equal and opposite tilt to a portion of the wavefront incident on the lenslet. As a result, an aberration within that portion of the wavefront is cancelled. The predetermined point is determined to be equal to and opposite a focal spot shift of the lenslet.
Claims15
A wavefront sensor, comprising:
- radiation sensor means;
- and
- an array of lenslets optically coupled to said radiation sensor means, said array of lenslets having a radiation receiving surface for receiving an incident wavefront and for focussing the wavefront at a plurality of focal positions upon said radiation sensor means, wherein each of said lenslets is comprised of a diffractive optical element having an optical center that is located at a predetermined point for inducing an equal and opposite tilt to a portion of the wavefront incident on the lenslet for substantially cancelling an aberration within that portion of the wavefront.
A method of fabricating a lenslet array for use with a wavefront having a known aberration, comprising the steps of:
- for each lenslet of the lenslet array, determining a location of an optical center of the lenslet relative to a geometric center of an array cell within which the lenslet is contained, the step of determining including the steps of,
- determining a focal spot shift of the aberrated wavefront at a position of the lenslet cell;
- and
- shifting the optical center of the lenslet by an equal and opposite amount to the determined focal spot shift;
- and wherein the method further includes a step of
- fabricating the lenslet into or upon a surface of a substrate such that the optical center of the lenslet is positioned away from the geometric center of the cell by an amount equal to and opposite the determined focal spot shift.
A null corrector for use with an aberrated wavefront, comprising:
- a lenslet array having a plurality of lenslets, each lenslet of the lenslet array including a diffractive optical element having a location of an optical center thereof disposed a predetermined distance away from a geometric center of an array cell within which the lenslet is contained, the predetermined distance being equal and opposite to a focal spot shift of the lenslet, the focal spot shift being found, in the case of Seidel spherical aberration, in accordance with the expression,
- spot shift=4a.rho..sub.i.sup.3 F,
- wherein F is the focal length of said lenslet, (a) is a magnitude of the aberration, and where ( .sub.i) is a radial distance of an i.sup.th lenslet from a center of the wavefront.
A Hartmann-Shack Wavefront Sensor for measuring an aberration of a wavefront reflecting from a surface, comprising:
- means for relaying a pupil of an optical system to a location away from a focal plane of the optical system;
- and
- means, positioned at the location, for sensing
- a wavefront, said sensing means including, radiation sensor means;
- and
- an array of lenslets optically coupled to said radiation sensor means, said array of lenslets having a radiation receiving surface for receiving an incident wavefront and for focussing the wavefront at a plurality of focal positions upon said radiation sensor means, wherein each of said lenslets is comprised of a diffractive optical element having an optical center that is located at a predetermined point for inducing an equal and opposite tilt to a portion of the wavefront incident on the lenslet for substantially cancelling an aberration within that portion of the wavefront.
Dependencies are inferred from the claim text.