Freeform surface off-axial three-mirror imaging system

Patent metadata

Field	Value
Publication number	US-11043521-B2
Application number	US-201816231535-A
Country	US
Kind code	B2
Filing date	Dec 23, 2018
Priority date	Jan 12, 2018
Publication date	Jun 22, 2021
Grant date	Jun 22, 2021

Abstract

A freeform surface off-axial three-mirror imaging system comprising a primary mirror, a secondary mirror, a tertiary mirror, and an image sensor. Each reflective surface of the primary mirror, the secondary mirror, and the tertiary mirror is an xy polynomial freeform surface. A field angle of the freeform surface off-axial three-mirror imaging system is larger than or equal to 60°×1°. An F-number of the freeform surface off-axial three-mirror imaging system is less than or equal to 2.5.

First claim

What is claimed is:

1. A freeform surface off-axial three-mirror imaging system, comprising:
a primary mirror, a secondary mirror, a tertiary mirror, and an image sensor, wherein a plurality of feature rays are successively reflected by the primary mirror, the secondary mirror and the tertiary mirror to form an image on the image sensor;
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 second three-dimensional rectangular coordinates system (X′,Y′,Z′) is defined with a vertex of the secondary mirror 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 and a Y-axis negative direction, and in the second three-dimensional rectangular coordinates system (X′,Y′,Z′), a reflective surface of the secondary mirror is an x′y′ polynomial freeform surface;
a third three-dimensional rectangular coordinates system (X″,Y″,Z″) is defined with a vertex of the tertiary mirror 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 Y′-axis positive direction, and in the third three-dimensional rectangular coordinates system (X″,Y″,Z″), a reflective surface of the tertiary mirror is an x″y″ polynomial freeform surface;
a field angle of the freeform surface off-axial three-mirror imaging system is larger than or equal to 60°×1°, and an F-number of the freeform surface off-axial three-mirror imaging system is less than or equal to 2.5.

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 obtained by a process of: moving the first three-dimensional rectangular coordinates system (X,Y,Z) for about 272.306 mm along the Y-axis negative direction, and then moving for about 518.025 mm along the Z-axis negative direction, and then rotating along a counterclockwise direction for about 31.253° with an X-axis as a rotation axis.

3. The freeform surface off-axial three-mirror imaging system of claim 1 , wherein the third three-dimensional rectangular coordinates system (X″,Y″,Z″) is obtained by a process of: moving the second three-dimensional rectangular coordinates system (X′,Y′,Z′) for about 346.467 mm along the Z′-axis negative direction, and then moving for about 141.540 mm along the Y′-axis negative direction, and then rotating along a counterclockwise direction for about 20.079° with an X′-axis as the rotation axis.

4. The freeform surface off-axial three-mirror imaging system of claim 1 , wherein a distance between the first origin and the second origin is about 585.235 mm.

5. The freeform surface off-axial three-mirror imaging system of claim 1 , wherein a distance between the second origin and the third origin is about 374.263 mm.

6. The freeform surface off-axial three-mirror imaging system of claim 1 , wherein in the first three-dimensional rectangular coordinates system (X,Y,Z), the reflective surface of the primary mirror is an eighth-order polynomial freeform surface of xy; and an equation of the eighth-order polynomial freeform surface of xy is:

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3

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5

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7

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9

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10

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Assignees

• Univ Tsinghua
• Hon Hai Prec Ind Co Ltd

Inventors

• Tang rui-rui
• Zhang Ben-Qi
• Zhu Jun
• Jin Guo-Fan
• Fan Shou-Shan

Classifications

• H04N25/615

  involving a transfer function modelling the optical system, e.g. optical transfer function [OTF], phase transfer function [PhTF] or modulation transfer function [MTF] · CPC title

• H10F39/8067 Primary

  Reflectors · CPC title

• G02B17/0626 Primary

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

• G02B17/0642

  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

• H04N5/35721

  Electricity · mapped topic