Off-axis three-mirror optical system with freeform surfaces

Patent metadata

Field	Value
Publication number	US-9846298-B2
Application number	US-201615244205-A
Country	US
Kind code	B2
Filing date	Aug 23, 2016
Priority date	Apr 1, 2016
Publication date	Dec 19, 2017
Grant date	Dec 19, 2017

Abstract

An off-axis three-mirror optical system with freeform surfaces comprised an aperture, a primary mirror, a secondary mirror, a tertiary mirror, and a detector. The aperture is located on an incident light path. The primary mirror is located on an aperture side. The secondary mirror is located on a primary mirror reflected light path. The tertiary mirror is located on a secondary mirror reflected light path. The detector located on a tertiary mirror reflected light path. The primary mirror and the tertiary mirror have a same fifth-order polynomial freeform surface expression. The primary mirror reflected light path, the secondary mirror reflected light path and the tertiary mirror reflected light path overlap with each other.

First claim

What is claimed is:

1. An off-axis three-mirror optical system with freeform surfaces comprising:
an aperture located on an incident light path, and the aperture defining an aperture center;
a primary mirror located on an aperture side that is away from an object space and configured to reflect an incident light to form a first reflected light, and the first reflected light defining a first reflected light path;
a secondary mirror located on the first reflected light path and configured to reflect the first reflected light to form a second reflected light, and the second reflected light defining a second reflected light path;
a tertiary mirror located on the second reflected light path and configured to reflect the second reflected light to form a third reflected light, and the third reflected light defining a third reflected light path; and
a detector located on the third reflected light path and configured to receive the third reflected light;
wherein a first three-dimensional rectangular coordinates system (x 1 , y 1 , z 1 ) is defined, and the aperture center is a first three-dimensional rectangular coordinates system (x 1 , y 1 , z 1 ) origin; a second three-dimensional rectangular coordinates system (x 2 , y 2 , z 2 ) is defined for a primary mirror location and a tertiary mirror location; a third three-dimensional rectangular coordinates system (x 3 , y 3 , z 3 ) is defined for a secondary mirror location; and a fourth three-dimensional rectangular coordinates system (x 4 , y 4 , z 4 ) is defined for a detector location;
a primary mirror reflective surface and a tertiary mirror reflective surface have a same freeform surface analytical expression, and the freeform surface equation is a fifth-order polynomial of x 2 y 2 ; a secondary mirror reflective surface is a fifth-order polynomial of x 3 y 3 ; and the first reflected light path, the second reflected light path and the third reflected light path overlap with each other.

2. The system as claimed in claim 1 , wherein a second three-dimensional rectangular coordinates system (x 2 , y 2 , z 2 ) origin is in (0, 88.59727, 198.07169) position of the first three-dimensional rectangular coordinates system (x 1 , y 1 , z 1 ).

3. The system as claimed in claim 1 , wherein a z 2 -axis positive direction rotates 27.84258 degrees along a counterclockwise direction relative to a z 1 -axis positive direction.

4. The system as claimed in claim 1 , wherein a third three-dimensional rectangular coordinates system (x 3 , y 3 , z 3 ) origin is in (0, −159.26851, −22.49695) position of the first three-dimensional rectangular coordinates system (x 1 , y 1 , z 1 ).

5. The system as claimed in claim 1 , wherein a z 3 -axis positive direction rotates 10.80811 degrees along a clockwise direction relative to a z 1 -axis positive direction.

6. The system as claimed in claim 1 , wherein a fourth three-dimensional rectangular coordinates system (x 4 , y 4 , z 4 ) origin is in (0, −44.59531, −47.02867) position of the first three-dimensional rectangular coordinates system (x 1 , y 1 , z 1 ).

7. The system as claimed in claim 1 , wherein a z 4 -axis positive direction rotates 16.28528 degrees along a counterclockwise direction relative to a z 1 -axis positive direction.

8. The system as claimed in claim 1 , wherein the fifth-order polynomial of x 2 y 2 is:

z
2

⁡

(

x
2

,

y
2

)

=

c
⁡

(

x
2
2

+

y
2
2

)

1
+

1
-

(

1
+
k

)

⁢

c
2

⁡

(

x
2
2

+

y
2
2

)

+

A
2

⁢

y
2

+

A
3

⁢

x
2
2

+

A
5

⁢

y
2
2

+

A
7

⁢

x
2
2

⁢

y
2

+

A
9

⁢

y
2
3

+

A
10

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

• G02B17/06

  using mirrors only {, i.e. having only one curved mirror (used in non-imaging applications G02B19/00)} · CPC title

• G02B17/02

  Catoptric systems, e.g. image erecting and reversing system · CPC title

• G02B17/00

  Systems with reflecting surfaces, with or without refracting elements · CPC title

• G02B17/0694

  with variable magnification or multiple imaging planes, including multispectral systems (systems with only refractive elements G02B15/14) · CPC title