Freeform surface off-axial three-mirror imaging system

Patent metadata

Field	Value
Publication number	US-11249292-B2
Application number	US-201916502138-A
Country	US
Kind code	B2
Filing date	Jul 3, 2019
Priority date	Jan 25, 2019
Publication date	Feb 15, 2022
Grant date	Feb 15, 2022

Abstract

A freeform surface off-axial three-mirror imaging system comprising a primary mirror, a secondary mirror, a tertiary mirror, and a detector. The secondary mirror comprises a first freeform surface and a second freeform surface. Each reflective surface of the primary mirror, the first freeform surface, the second freeform surface and the tertiary mirror is an xy polynomial freeform surface. The freeform surface off-axial three-mirror imaging system comprises a first field of view formed by the first freeform surface and a second field of view formed by the second freeform surface.

First claim

What is claimed is:

1. A freeform surface off-axial three-mirror imaging system, comprising:
a primary mirror, wherein a first three-dimensional rectangular coordinates system (X,Y,Z) is defined with a vertex of the primary mirror as a first origin, and in the first three-dimensional rectangular coordinates system (X,Y,Z), a reflective surface of the primary mirror is an xy polynomial freeform surface;
a secondary mirror comprising a first freeform surface and a second freeform surface, wherein a second three-dimensional rectangular coordinates system (X′,Y′,Z′) is defined with a vertex of the first freeform surface 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 an Z-axis negative direction and a Y-axis positive direction, and in the second three-dimensional rectangular coordinates system (X′,Y′,Z′), a reflective surface of the first freeform surface is an x′y′ polynomial freeform surface; a third three-dimensional rectangular coordinates system (X″,Y″,Z″) is defined with a vertex of the second freeform surface 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 an Z-axis positive direction and a Y-axis negtive direction, and in the third three-dimensional rectangular coordinates system (X″,Y″,Z″), a reflective surface of the second freeform surface is an x″y″ polynomial freeform surface;
an aperture being capable of moving from the first freeform surface to the second freeform surface;
a tertiary mirror, wherein a fourth three-dimensional rectangular coordinates system (X′″,Y′″,Z′″) is defined with a vertex of the tertiary mirror as a fourth origin, and the fourth three-dimensional rectangular coordinates system (X′″,Y′″,Z′″) is obtained by moving the first three-dimensional rectangular coordinates system (X,Y,Z) along an Z-axis negative direction and a Y-axis negative direction, and in the fourth three-dimensional rectangular coordinates system (X′″,Y′″,Z′″), a reflective surface of the tertiary mirror is an x′″y′″ polynomial freeform surface;
a detector, wherein feature rays are reflected by the primary mirror, the secondary mirror and the tertiary mirror to form an image on the detector;
wherein the freeform surface off-axial three-mirror imaging system comprises a first field of view formed by the first freeform surface and a second field of view formed by the second freeform surface.

2. The freeform surface off-axial three-mirror imaging system of claim 1 , wherein the second three-dimensional rectangular coordinates system (X′,Y′,Z′) is offset from the first three-dimensional rectangular coordinates system (X,Y,Z) by about 143.542 mm along the Y-axis positive direction, and offset from the first three-dimensional rectangular coordinate system (X,Y,Z) by about 87.613 mm along the Z-axis negative direction, and then rotating along the counterclockwise direction for about 65.978° with the X axis as the rotation axis.

3. The freeform surface off-axial three-mirror imaging system of claim 1 , wherein a distance between the origin of the first three-dimensional rectangular coordinates system (X,Y,Z) and the origin of the second three-dimensional rectangular coordinates system (X′,Y′,Z′) is about 168.168 mm.

4. The freeform surface off-axial three-mirror imaging system of claim 1 , wherein the third three-dimensional rectangular coordinates system (X″,Y″,Z″) is offset from the second three-dimensional rectangular coordinates system (X′,Y′,Z′) by about 4.108 mm along a Y′-axis negative direction, and offset from the first three-dimensional rectangular coordinate system (X,Y,Z) by about 1.473 mm along an Z′-axis negative direction, and then rotating along the counterclockwise direction for about 8.549° with the X′ axis as the rotation axis.

5. The freeform surface off-axial three-mirror imaging system of claim 1 , wherein a distance between the origin of the second three-dimensional rectangular coordinates system (X′,Y′,Z′) and the origin of the third three-dimensional rectangular coordinates system (X″,Y″,Z″) is about 4.364 mm.

6. The freeform surface off-axial three-mirror imaging system of claim 1 , wherein the fourth three-dimensional rectangular coordinates system (X′″,Y′″,Z′″) is offset from moving the first three-dimensional rectangular coordinates system (X,Y,Z) by about 84.058 mm along the Z-axis negative direction, and offset from the first three-dimensional rectangular coordinate system (X,Y,Z) by about 5.298 mm along the Y-axis negative direction, and then rotating along the counterclockwise direction for about 54.668° with the X-axis s as the rotation axis.

7. The freeform surface off-axial three-mirror imaging system of claim 1 , a distance between the origin of the fourth three-dimensional rectangular coordinates system (X′″,Y′″,Z′″) and the origin of the first three-dimensional rectangular coordinates system (X,Y,Z) is about 84.225 mm.

8. The freeform surface off-axial three-mirror imaging system of claim 1 , wherein the reflective surface of the primary 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 can be expressed as follows:

z
⁡

(

x
,
y

)

=

c
⁡

(

x
2

+

y
2

)

1
+

1
-

(

1
+
k

)

⁢

c
2

⁡

(

x
2

+

y
2

)

+

A
2

⁢
y

Assignees

• Univ Tsinghua
• Hon Hai Prec Ind Co Ltd

Inventors

• Zhu Jun
• Tang rui-rui
• Jin Guo-Fan
• Fan Shou-Shan

Classifications

• G02B5/10

  with curved faces · CPC title

• G02B17/0626 Primary

  using three curved mirrors (G02B17/0668, G02B17/0694 take precedence) · CPC title

• G02B17/0636

  off-axis or unobscured systems in which all of the mirrors share a common axis of rotational symmetry · CPC title

• G02B27/0025

  for optical correction, e.g. distorsion, aberration · 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