Freeform surface off-axial three-mirror imaging system

Patent metadata

Field	Value
Publication number	US-11650402-B2
Application number	US-202016999222-A
Country	US
Kind code	B2
Filing date	Aug 21, 2020
Priority date	Jan 15, 2020
Publication date	May 16, 2023
Grant date	May 16, 2023

Abstract

A freeform surface off-axial three-mirror imaging system is provided. The freeform surface off-axial three-mirror imaging system comprises a primary mirror, a secondary mirror, and a compensating mirror. The primary mirror, the secondary mirror, and the compensating mirror are located adjacent and spaced away from each other. A surface shape of each of the primary mirror and the secondary mirror is a quadric surface. The primary mirror is used as an aperture stop. A surface shape of the compensating mirror is a freeform surface. A light emitted from a light source is reflected by the primary mirror, the secondary mirror, and the compensating mirror to form an image on an image plane.

First claim

What is claimed is:

1. A freeform surface off-axial three-mirror imaging system, comprising:
a primary mirror, a secondary mirror, and a compensating mirror, wherein the primary mirror, the secondary mirror and the compensating mirror are located adjacent and spaced away from each other, a surface shape of each of the primary mirror and the secondary mirror is a quadric surface, the primary mirror is an aperture stop, a surface shape of the compensating mirror is a freeform surface, a light emitted from a light source is reflected by the primary mirror, the secondary mirror, the compensating mirror to form an image on an image plane, and an F-number of view of the freeform surface off-axial three-mirror imaging system is 5;
a first three-dimensional rectangular coordinates system (X, Y, Z) is defined by a location of the secondary mirror, a vertex of the secondary mirror is an origin of the three-dimensional rectangular coordinates system (X, Y, Z), a reflective surface of the compensating mirror is an xy polynomial freeform surface; and an xy polynomial equation is

z
⁡
(

x
,
y

)

=

c
⁡
(

x
2

+

y
2

)

1
+

1
-

(

1
+
k

)

⁢

c
2

(

x
2

+

y
2

)

+

∑

i
=
1

N

A
i

⁢

x
m

⁢

y
n

,

wherein z represents surface sag, c represents surface curvature, k represents conic constant, while Ai represents an ith term coefficient; and
the reflective surface of compensating mirror is a fourth-order polynomial freeform surface of xy without odd items of x; and an equation of the fourth-order polynomial freeform surface of xy is:

z
⁡
(

x
,
y

)

=

c
⁡
(

x
2

+

y
2

)

1
+

1
-

(

1
+
k

)

⁢

c
2

(

x
2

+

y
2

)

+

A
2

⁢
y

+

A
3

⁢

x
2

+

A
5

⁢

y
2

+

A
7

⁢

x
2

⁢
y

+

A
9

⁢

y
3

+

A

1
⁢
0

⁢

x
4

+

Assignees

• Univ Tsinghua
• Hon Hai Prec Ind Co Ltd

Inventors

• Zhu Jun
• Tang rui-rui
• Wu Wei-Chen
• Jin Guo-Fan
• Fan Shou-Shan

Classifications

• G02B27/0012

  Optical design, e.g. procedures, algorithms, optimisation routines · CPC title

• G02B17/0642 Primary

  off-axis or unobscured systems in which not all of the mirrors share a common axis of rotational symmetry, e.g. at least one of the mirrors is warped, tilted or decentered with respect to the other elements · CPC title

• G02B23/06

  having a focussing action, e.g. parabolic mirror · CPC title

• G02B17/0631 Primary

  on-axis systems with at least one of the mirrors having a central aperture · CPC title

• G02B5/10

  with curved faces · CPC title