
Holographic SHG Imaging 211
Γ( , ) .
,
x y C x y
N
N
y
x
=
==
∑∑
2
00
π
λ
α β
βα
α β
(9.14)
en, C
α
,
β
denes a set of aberration coecients, relating to the linearly independent polynomials
of x and y and each coecient corresponds to a unique aberration type. For example, coecient C
0,0
denes a uniform phase oset, or piston aberration, while C
1,0
and C
0,1
respectively describe tilts along x
and y. In an o-axis holographic microscope, some tilt aberrations are expected due to the o-axis angle
between the reference and the object waves that introduces a linear phase gradient
Γ
TILT x y
x y C x C y k x k y( , ) ( ) ,
, , , ,
= + = +
2
1 0 0 1 0 0
π
(9.15)
where t ...