Method and apparatus for wavefront sensing
A method for performing optical wavefront sensing includes providing an amplitude transmission mask having a light input side, a light output side, and an optical transmission axis passing from the light input side to the light output side. The amplitude transmission mask is characterized by a checkerboard pattern having a square unit cell of size Λ. The method also includes directing an incident light field having a wavelength λ to be incident on the light input side and propagating the incident light field through the amplitude transmission mask. The method further includes producing a plurality of diffracted light fields on the light output side and detecting, at a detector disposed a distance L from the amplitude transmission mask, an interferogram associated with the plurality of diffracted light fields. The relation 0 < L < 1 8 Λ 2 λ or 1 4 Λ 2 λ ( 2 n - 1 ) < L < 1 4 Λ 2 λ ( 2 n + 1 ) is satisfied, where n is an integer greater than zero.
1. A method for performing optical wavefront sensing, the method comprising:
providing an amplitude transmission mask having a light input side, a light output side, and an optical transmission axis passing from the light input side to the light output side, wherein the amplitude transmission mask is characterized by a checkerboard pattern having a square unit cell of size Λ,
directing an incident light field having a wavelength λ to be incident on the light input side;
propagating the incident light field through the amplitude transmission mask;
producing a plurality of diffracted light fields on the light output side;
detecting, at a detector disposed a distance L from the amplitude transmission mask, an interferogram associated with the plurality of diffracted light fields, wherein the interferogram includes phase slope information; wherein:
0
<
L
<
1
8
Λ
2
λ
or
1
4
Λ
2
λ
(
2
n
-
1
)
<
L
<
1
4
Λ
2
λ
(
2
n
+
1
)
,
where n is an integer greater than zero; and
integrating a two-dimensional phase slope computed using the interferogram to construct a phase front associated with the incident light field.
2. The method of claim 1 wherein the amplitude transmission mask comprises an amplitude-only transmission mask.
3. The method of claim 1 wherein the detector is characterized by a pixel size and Λ is about 10 times larger than the pixel size.
4. The method of claim 1 wherein:
10 nm<λ<2,000 nm; and
1 mm≤L≤10 mm.
5. The method of claim 1 wherein constructing the phase front comprises performing a Fourier domain spatial carrier analysis.
6. The method of claim 5 wherein the Fourier domain spatial carrier analysis comprises selecting carrier terms located diagonally, but not orthogonally, with respect to axes of the amplitude transmission mask.
7. The method of claim 6 further comprising performing a point-by-point optimization on the diagonal carrier terms to refine a spatial resolution of the wavefront.
8. The method of claim 1 further comprising:
providing a segmented mirror array; and
providing a plurality of the amplitude-only transmission masks adjacent the segmented mirror array such that each one of the amplitude-only transmission masks is disposed along a seam of two adjoining mirror segments.
9. The method of claim 8 wherein the mirror segments are hexagonal.