Off-axis two-mirror infrared imaging system

Patent metadata

Field	Value
Publication number	US-11796796-B2
Application number	US-202117337224-A
Country	US
Kind code	B2
Filing date	Jun 2, 2021
Priority date	Aug 14, 2020
Publication date	Oct 24, 2023
Grant date	Oct 24, 2023

Abstract

The present application relates to an off-axis two-mirror infrared imaging system including a primary reflecting mirror and a secondary reflecting mirror. The primary reflecting mirror is located on the incident light path of an incident infrared light beam and reflects the incident infrared light beam to form a first reflected light beam. The secondary reflecting mirror is located on the reflection light path of the primary reflecting mirror, and is used to reflect the first reflected light beam to form a second reflected light beam. The second reflected light beam reaches an image surface after passing through the incident infrared light beam. The reflective surfaces of the primary reflecting mirror and the secondary reflecting mirror are freeform surfaces. The secondary reflecting mirror and the image plane are respectively located on both sides of the incident infrared light beam.

First claim

What is claimed is:

1. An off-axis two-mirror infrared imaging system, comprising:
a primary reflecting mirror located on an incident light path of an incident infrared light beam, wherein the primary reflecting mirror reflects the incident infrared light beam to form a first reflected light beam; and
a secondary reflecting mirror located on an reflection light path of the primary reflecting mirror, wherein the primary reflecting mirror reflects the first reflected light beam to form a second reflected light beam, and the second reflected light beam reaches an image surface after passing through the incident infrared light beam;
wherein a space where the off-axis two-mirror infrared imaging system is located is defined as a global three-dimensional rectangular coordinate system (X, Y, Z), a space where the primary reflecting mirror is located is defined as a first local three-dimensional rectangular coordinate system (X′, Y′, Z′), a space where the secondary reflecting mirror is located is defined as a second local three-dimensional rectangular coordinate system (X″, Y″, Z″); the first local three-dimensional rectangular coordinate system (X′, Y′, Z′) are obtained by translating the global three-dimensional rectangular coordinate system (X, Y, Z) along a negative direction of a Y axis and a positive direction of a Z axis, and the second local three-dimensional rectangular coordinate system (X″, Y″, Z″) is obtained by translating the first local three-dimensional rectangular coordinate system (X′, Y′, Z′) along the positive direction of the Y axis and the negative direction of the Z axis; reflective surfaces of the primary reflecting mirror and the secondary reflection are freeform surfaces; the secondary reflecting mirror and the image surface are respectively located on both sides of the incident infrared light beam, so that the incident infrared light beam is between the secondary reflecting mirror and the image surface; and a focal length of the off-axis two-mirror infrared imaging system is in a range from 120 mm to 160 mm, and F number of the off-axis two-mirror infrared imaging system is in a range from 1.4 to 2.0.

2. The off-axis two-mirror infrared imaging system of claim 1 , wherein the primary reflecting mirror and an entrance pupil are respectively located on both sides of the second reflected light beam, so that the second reflected light beam is between the primary reflecting mirror and an entrance pupil.

3. The off-axis two-mirror infrared imaging system of claim 1 , wherein an optical path of the second reflected light beam crosses and partially overlaps the incident light path of the incident infrared light beam.

4. The off-axis two-mirror infrared imaging system of claim 1 , wherein in the global three-dimensional rectangular coordinate system (X, Y, Z), the image plane deviates from the secondary reflecting mirror along the negative direction of the Y axis.

5. The off-axis two-mirror infrared imaging system of claim 1 , wherein in the first local three-dimensional rectangular coordinate system (X′, Y′, Z′), the reflection surface of the primary reflecting mirror is the freeform surface of x′y′ polynomial, and a degree of the x′y′ polynomial is 7th, and an equation of the x′y′ polynomial is represented as:

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Assignees

• Univ Tsinghua
• Hon Hai Prec Ind Co Ltd

Inventors

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

Classifications

• H04N23/20

  for generating image signals from infrared radiation only · CPC title

• G02B27/0018 Primary

  with means for preventing ghost images (anti-reflection coatings G02B1/11) · CPC title

• G02B27/005

  for correction of secondary colour or higher-order chromatic aberrations · CPC title

• H04N5/33

  Transforming infrared radiation (cameras or camera modules for generating image signals from infrared radiation H04N23/20; circuitry of SSIS for transforming infrared radiation into image signals H04N25/20) · CPC title

• G02B17/0621 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