Off-axial three-mirror optical system with freeform surfaces

Patent metadata

Field	Value
Publication number	US-9703084-B2
Application number	US-201514726684-A
Country	US
Kind code	B2
Filing date	Jun 1, 2015
Priority date	Jun 3, 2014
Publication date	Jul 11, 2017
Grant date	Jul 11, 2017

Abstract

An off-axial three-mirror optical system with freeform surfaces includes a primary mirror, a secondary mirror, a tertiary mirror, and an image sensor. The primary mirror is located on an incident light path. The secondary mirror is located on a primary mirror reflecting light path. The tertiary mirror is located on a secondary mirror reflecting light path. The image sensor is located on a tertiary mirror reflecting light path. A primary mirror surface and a tertiary mirror surface are all xy polynomial freeform surfaces up to a fifth order. A secondary mirror surface is a planar surface.

First claim

What is claimed is:

1. An off-axial three-mirror optical system with freeform surfaces comprising:
a primary mirror located on an incident light path, and configured to reflect an incident light to form a first reflected light; and a first three-dimensional rectangular coordinates system (X, Y, Z) is defined by a primary mirror vertex as a first origin;
a secondary mirror located on a first reflected light path, and configured to reflect the first reflected light to form a second reflected light; a secondary mirror reflecting surface is a stop surface; a second three-dimensional rectangular coordinates system (X′, Y′, Z′) is defined by a secondary mirror vertex as a second origin; and the second three-dimensional rectangular coordinates system (X′, Y′, Z′) is obtained by moving the first three-dimensional rectangular coordinates system (X, Y, Z) along a Z-axis negative direction;
a tertiary mirror located on a second reflected light path, and configured to reflect the second reflected light to form a third reflected light; a third three-dimensional rectangular coordinates system (X″, Y″, Z″) is defined by a tertiary mirror vertex as a third origin; and the third three-dimensional rectangular coordinates system (X″, Y″, Z″) is obtained by moving the second three-dimensional rectangular coordinates system (X′, Y′, Z′) along a Z′-axis positive direction; and
a detector located on a third reflected light path and configured to receive the third reflected light;
wherein a primary mirror surface is an xy polynomial freeform surface up to a fifth order, and an xy polynomial freeform surface equation 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
10

⁢

x
4

+

A
12

⁢

x
2

⁢

y
2

+

A
14

⁢

y
4

+

A
16

⁢

x
4

⁢
y

+

A
18

⁢

x
2

⁢

y
3

+

A
20

⁢

y
5

,

wherein, c represents surface curvature, k represents conic constant, and A 2 ˜A 20 represent coefficients; a tertiary mirror surface is an x″y″ polynomial freeform surface up to a fifth order, and an x′y′ polynomial freeform surface equation is

z
″

⁡

(

Assignees

• Univ Tsinghua
• Hon Hai Prec Ind Co Ltd

Inventors

• Zhu Jun
• Yang Tong
• Jin Guo-Fan
• Fan Shou-Shan

Classifications

• 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