US 12,724,176 B2Granted

System for inspecting surfaces of an optical wave using a gradient density filter

AssigneesCentre National De La Recherche Scientifique, Observatoire De La Cote D'Azur, Université CôTe D'Azur, Universite Grenoble Alpes

InventorsFrançois Henault, Alain Spang

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Abstract

The systems for inspecting an optical wave surface output from an optical device, the optical device comprising an output pupil, the inspection system comprising an optical measurement head and a computer for processing the images obtained from said the optical measurement head. The optical measurement head comprises: a density gradient filter, the density varying periodically in the two directions of the space, a matrix array comprising at least four identical lenses, of square form, of the same focal length and disposed symmetrically, a matrix of photodetectors, each of the four lenses forming, of the pupil, an image in the plane of this matrix. The computer for processing the images comprises computation means that make it possible to calculate the partial derivatives ∂ Δ ∂ x ⁢ ( x , y ) ⁢ and ⁢ ∂ Δ ∂ y ⁢ ( x , y ) of the wave surface Δ(x, y) in the plane of the output pupil.

A system for inspecting an optical wave surface output from an optical device, said optical device comprising an output pupil, said inspection system comprising an optical measurement head and a computer for processing images obtained from said optical measurement head, wherein

the optical measurement head comprises:
a matrix array of linearly varying density gradient filters, in a plane referenced (x′, y′) at right angles to the optical axis of the optical measurement head, the transmission T(x′, y′) of said filters being governed by the equation:
T
ij
(
x
′
,
y
′
)
=
1
+
2
⁢
π
⁡
(
idx
′
/
p
x
-
jdy
′
/
p
x
)
2
⁢
with
[
dx
′
dy
′
]
=
[
x
′
-
i
⁡
(
m
+
0.25
)
⁢
p
x
/
2
y
′
-
j
⁡
(
n
+
0.25
)
⁢
p
y
/
2
]
px and py representing the periods of the two sinusoidal functions dependent respectively on dx′ and dy′, i and j being able to take the values −1 and +1, m and n being positive integers or nil,
a matrix array of identical lenses, of square form, of the same focal length, said matrix array comprising 4 k lenses, where k is an integer greater than or equal to 1, each center of one of the four lenses of a group of four lenses being disposed on a respective axis passing through the center of the output pupil and one of four points O′M′(i, j) of the matrix array of density gradient filters such that, in the plane referenced (x′, y′), the four points are defined by O′M′(i, j) based on the combinations i=1, j=1;
i=−1, j=1;
i=1, j=−1;
and i=−1, j=−1 via the following relation:
O
′
⁢
M
i
,
j
′
=
[
i
⁡
(
m
+
0.25
)
⁢
p
x
/
2
j
⁡
(
n
+
0.25
)
⁢
p
y
/
2
]
a matrix of photodetectors, each of the four lenses of a group of four lenses forming, of the pupil, an image in the plane of this matrix, these images being referenced I″k(x, y), k varying from 1 to 4;
the computer for processing the images comprises computation means that make it possible to calculate the partial derivatives
∂
Δ
∂
x
⁢
(
x
,
y
)
⁢
and
⁢
∂
Δ
∂
y
⁢
(
x
,
y
)
of the wave surface Δ(x, y) in the plane (x, y) of the output pupil, these partial derivatives being equal to
∂
Δ
∂
x
⁢
(
x
,
y
)
=
A
⁢
x
+
B
⁡
(
I
4
″
(
x
,
y
)
-
I
3
″
(
x
,
y
)
+
I
2
″
(
x
,
y
)
-
I
1
″
(
x
,
y
)
)
∂
Δ
∂
y
⁢
(
x
,
y
)
=
Ay
+
B
⁡
(
I
4
″
(
x
,
y
)
+
I
3
″
(
x
,
y
)
-
I
2
″
(
x
,
y
)
-
I
1
″
(
x
,
y
)
)
A and B being constants dependent on the geometrical parameters of the optical measurement head.

243 more elements

Facts

Application

18/018,520Filed 30 Jul 2020

Published

US 2023/0296813 A121 Sep 2023

Granted

1 Sep 2026

Term ends

Not estimatedThe source records don’t support an estimate.

Classification6 codes

G02B 3/0056
Characterized by the distribution or form of lenses: arranged along two different directions in a plane, e.g. honeycomb arrangement of lenses
G01J 9/00
Measuring optical phase difference
G02B 5/20
Optical elements other than lenses: filters
G02B 2003/0093
Simple or compound lenses: characterised by the shape

Abstract

Claims5