CN113238368B - Non-secondary blocking surface view field folded-axis three-mirror telescope objective lens - Google Patents
Non-secondary blocking surface view field folded-axis three-mirror telescope objective lens Download PDFInfo
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- CN113238368B CN113238368B CN202110538000.7A CN202110538000A CN113238368B CN 113238368 B CN113238368 B CN 113238368B CN 202110538000 A CN202110538000 A CN 202110538000A CN 113238368 B CN113238368 B CN 113238368B
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B17/00—Systems with reflecting surfaces, with or without refracting elements
- G02B17/08—Catadioptric systems
- G02B17/082—Catadioptric systems using three curved mirrors
- G02B17/0832—Catadioptric systems using three curved mirrors 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
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/02—Telephoto objectives, i.e. systems of the type + - in which the distance from the front vertex to the image plane is less than the equivalent focal length
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
- Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Telescopes (AREA)
- Lenses (AREA)
Abstract
The invention relates to a three-mirror telescope objective lens without a secondary blocking folding shaft, which comprises: a primary mirror, a secondary mirror, a triple mirror, a deflection mirror and a focal plane; the rotation symmetry axes of the main mirror, the secondary mirror and the three mirrors are not on the same axis, and the aperture diaphragm is arranged on the main mirror. The primary mirror surface is an ellipsoid, and the secondary mirror and the three mirror surfaces are hyperboloid. The deflection reflecting mirror is positioned on the emergent light path of the three mirrors and is inclined relative to the three mirrors so as to lead the image plane out of the optical axis, thereby facilitating the installation of the detector. The primary mirror and the secondary mirror form a middle real image, and the middle real image is close to the exit pupil, so that secondary obscuration generated by the deflection mirror is avoided. The invention realizes the design of the three-reflector telescope objective lens without the secondary blocking folding shaft through tiny eccentricity and inclination. The invention maintains similar mechanical structure, but has the advantages of relatively enlarged view field, compact structure and small volume, meets the miniaturization requirement, has small introduced eccentricity and inclination, has image quality close to diffraction limit and small stray light influence, and is suitable for the optical imaging fields such as area array cameras, imaging spectrometer front-end systems and the like.
Description
Technical Field
The invention relates to a telescopic objective which can be used for front objective of an area-array camera and an imaging spectrometer, in particular to a three-mirror telescopic objective without a secondary blocking folding shaft, and belongs to the technical field of imaging optics.
Background
In order to acquire a high resolution image of the ground, a long focal length telescopic objective lens is generally used. In order to reduce development and emission costs, miniaturization is required while satisfying high resolution, which puts higher demands on the design of the telescopic objective. Common telescopic objectives can be generally divided into three types, transmissive, catadioptric and reflective. The transmission system is easy to adjust by adding tools, but is sensitive to chromatic aberration and temperature, and is difficult to be suitable for a broadband. The catadioptric system is based on a two-reflection structure, and a lens correction group is added to correct off-axis aberration, but a long light shield is required to suppress stray light, so that miniaturization is difficult to achieve. The reflection system is widely used for the high-resolution satellite-borne camera due to no chromatic aberration, simple structure and insensitivity to temperature. There are on-axis and off-axis three-mirror structures widely used at present. The coaxial three-mirror structure generally adopts a deflection mirror to provide space for installing the detector, and secondary shielding needs to be avoided. The adoption of the offset-view three-mirror structure can avoid secondary blocking, but can only image a one-dimensional line view, and the other-dimensional view is difficult to expand. The other coaxial three-mirror structure adopts annular visual field imaging, the primary mirror and the secondary mirror form a primary intermediate real image, and the light reflected by the three mirrors is incident on the deflection mirror without secondary obscuration by sacrificing the central part visual field, so that part of visual field energy is lost. In order to enlarge the view field, an off-axis three-reflector structure is adopted, no central blocking exists, image space telecentricity is easy to realize, but the problems of large difficulty in tooling adjustment, large size in the vertical direction of the system and the like exist.
Disclosure of Invention
The invention solves the technical problems: aiming at the defects existing in the prior art, the non-secondary blocking folded axis three-mirror telescope objective lens has the advantages of long focal length, small volume, compact structure, suitability for wide wave band and capability of realizing two-dimensional surface view field imaging.
The technical scheme of the invention aims to provide a feasible non-secondary-obscuration refractive-axis three-mirror telescope objective lens, which comprises a main mirror, a secondary mirror, three mirrors, a deflection reflecting mirror and a focal plane. The primary mirror is an ellipsoid, the secondary mirror and the three mirrors are hyperboloids, the focal power of the primary mirror and the three mirrors is positive, and the focal power of the secondary mirror is negative; the telescope objective lens is provided with a middle real image surface, and the rotation symmetry axes of the main lens, the secondary lens and the three lenses are not coaxial. The entrance pupil of the optical system is positioned at the main mirror, and the deflection reflecting mirror is positioned near the exit pupil; the incident light from the ground target is reflected by the primary mirror and the secondary mirror in sequence, forms a real image between the secondary mirror and the three mirrors, is reflected by the three mirrors, is incident on the deflection mirror without being blocked, and forms a target image at the focal plane after being reflected by the deflection mirror.
The telescopic objective lens provided by the invention reserves the primary obscuration of the secondary lens, takes the eccentricity and the inclination of the primary lens as free variables, increases the degree of freedom compared with the traditional coaxial three-mirror, is beneficial to expanding the meridional view field and avoiding the secondary obscuration. Wherein the eccentric amount of the main mirror is 20-40 mm, and the inclination amount is 0.5-3 degrees; the eccentric amount of the secondary mirror is 1-20 mm, and the inclination amount is 0.5-3 degrees; the eccentric amount of the three mirrors is 1-20 mm, the inclination amount is 2-7 degrees, and the parameters are obtained by a great deal of research and experiments of the applicant.
The telescopic objective provided by the invention is provided with a view field diaphragm at the middle primary real image.
The working wave band of the telescopic objective provided by the invention is suitable for a wide wave band range from ultraviolet to infrared.
Compared with the prior art, the invention has the advantages that:
(1) Compared with a coaxial three-mirror telescope objective, the telescope objective provided by the invention has a similar mechanical structure form, retains the primary obscuration of the secondary mirror, and has relatively improved meridional view field without secondary obscuration.
(2) Compared with the traditional off-axis three-mirror telescope objective lens, the telescope objective lens provided by the invention has the advantages that the main lens does not need to be processed into a large-caliber mother lens, and the processing and developing cost is reduced. And secondly, the overall structure size is reduced, and the structure is more compact, so that the difficulty of adding the tool is reduced.
(3) The stray light inhibition performance is good, an outer light shield is not needed, and the volume is further reduced.
Drawings
FIG. 1 is a schematic view of the optical path structure of a telescopic objective according to an embodiment of the present invention;
FIG. 2 is a graph of the modulation transfer function of a telescopic objective lens according to an embodiment of the present invention;
FIG. 3 is a schematic view of a ray trace point of a telescopic objective according to an embodiment of the present invention;
FIG. 4 is a diagram of the grid distortion of the telescopic objective provided by the embodiment of the invention;
in fig. 1: 1. a primary mirror and an aperture stop; 2. a secondary mirror; 3. three mirrors; 4. a deflection mirror; 5. a focal plane.
Detailed Description
The following drawings and examples are provided to further illustrate the technical scheme of the present invention.
The invention discloses a three-mirror telescope objective lens without a secondary blocking folding shaft, which solves the problems of secondary blocking and difficult detector installation existing in opposite view field imaging of the existing three-mirror telescope objective lens. It comprises a main mirror 1, a secondary mirror 2, a three-mirror 3, a deflection mirror 4 and a focal plane 5. The rotation symmetry axes of the main mirror 1, the secondary mirror 2 and the three mirrors 3 are not on the same axis, and the aperture diaphragm is arranged on the main mirror 1. The surface shape of the main mirror 1 is an ellipsoid, and the surface shapes of the secondary mirror 2 and the triple mirror 3 are hyperboloid. The deflection mirror 4 is located on the outgoing light path of the three mirrors 3 and is inclined relative to the three mirrors 3 so as to lead the image plane out of the optical axis for the installation of the detector. The main mirror 1 and the secondary mirror 2 form an intermediate real image, and are close to the exit pupil, so that secondary obscuration caused by the deflection mirror is avoided. The structure provided by the invention realizes the design of the three-mirror telescope objective lens without the secondary blocking folding shaft through tiny eccentricity and inclination. A similar mechanical structure is maintained but the field of view is relatively increased compared to a coaxial three-mirror telescope objective. Compared with the traditional off-axis three-mirror telescope objective lens, the off-axis three-mirror telescope objective lens has the advantages of compact structure, small volume, small introduced decentration and inclination, near diffraction limit of image quality, small stray light influence, and is particularly suitable for the optical imaging fields such as area array cameras, imaging spectrometer front-mounted systems and the like.
The embodiment of the invention provides a three-mirror telescope objective lens without a secondary blocking folding shaft, which comprises the following design parameters: the focal length is 1200mm, the full field angle is 2.4 degrees multiplied by 1.7 degrees, the F number is 7, and the working wave band is 420 nm-780 nm.
As shown in fig. 1, the optical path structure of the telescopic objective provided by the embodiment of the invention is schematically shown. The rotation symmetry axes of the main mirror 1, the secondary mirror 2 and the three mirrors 3 are not coaxial, and the aperture diaphragm is positioned at the main mirror 1. After being reflected by the primary mirror 1 and the secondary mirror 2 in sequence, the incident light from the ground target forms a real image between the secondary mirror 2 and the three mirrors 3, and then is reflected by the three mirrors 3, the reflected light is incident on the deflection mirror 4 without obscuration, and after being reflected by the deflection mirror, a target image is formed at the focal plane 5.
The main structural parameters of the telescope objective provided by the example of the present invention are shown in Table 1, and the decentration and tilt amounts of the respective mirrors are shown in Table 2. The focal power of the primary mirror and the three mirrors is positive, the focal power of the secondary mirror 2 is negative, the primary mirror is an ellipsoid, and the secondary mirror and the three mirrors are hyperboloids. The clear aperture of the main lens is maximum and is 172mm, and the diameter of the central hole is 58mm. The total optical length is 270mm, approximately 1/4.4 of the focal length. The angle of inclination of the deflection mirror relative to the three mirrors is 17 deg..
Table 1 structural parameters of a fold-axis three-mirror telescopic objective
Table 2 decentration and tilting of each mirror
Referring to fig. 2, which is a graph of Modulation Transfer Function (MTF) curves of a telescopic objective provided in an embodiment of the present invention at fields of view (0 ° ), (0 °,0.85 °), (1.2 °,0 °), (1.2 °,0.85 °), (-1.2 °, -0.85 °), (-1.2 °,0 °), (0 °, -0.85 °) and (-1.2 °,0.85 °). In the figure, the abscissa indicates spatial frequency and the ordinate indicates MTF. As can be seen, the fringe field MTF value is 0.34 at the detector nyquist frequency and the imaging quality is near the diffraction limit.
Referring to fig. 3, it is a point-column diagram of the telescopic objective lens provided in this embodiment at the fields of view (0 ° ), (0 °,0.85 °), (1.2 °,0 °), (1.2 °,0.85 °), (-1.2 °, -0.85 °), (-1.2 °,0 °), (0 °, -0.85 °) and (-1.2 °,0.85 °) where black circles represent diffraction limit airy spots. From the graph, most of energy of the diffuse spots of each view field is concentrated in the range of the Airy spot, which shows that the telescopic objective lens has good imaging quality.
Referring to fig. 4, a grid distortion chart of the telescope objective provided by the present embodiment, according to calculation, the maximum distortion is 1.53%, and correction can be performed through later geometric scaling.
The above examples are provided for the purpose of describing the present invention only and are not intended to limit the scope of the present invention. The scope of the invention is defined by the appended claims. Various equivalents and modifications that do not depart from the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (3)
1. A non-secondary obscuration surface field of view refractive axis three-mirror telescope objective lens, characterized by comprising: a primary mirror (1), a secondary mirror (2), a three-mirror (3), a deflection reflecting mirror (4) and a focal plane (5); the primary mirror (1) is an ellipsoid, the secondary mirror (2) and the three mirrors (3) are hyperboloids, the focal power of the primary mirror (1) and the three mirrors (3) is positive, and the focal power of the secondary mirror (2) is negative; the telescopic objective lens is provided with a middle primary real image surface, and the rotation symmetry axes of the primary lens (1), the secondary lens (2) and the three lenses are not coaxial; the entrance pupil of the telescopic objective lens is positioned at the main lens (1), and the deflection reflecting mirror (4) is positioned near the exit pupil; after being reflected by the main mirror (1) and the secondary mirror (2) in sequence, the incident light from the ground target forms a real image between the secondary mirror (2) and the three mirrors (3), and then is reflected by the three mirrors (3), the reflected light is incident on the deflection mirror (4) without being blocked, and after being reflected by the deflection mirror (4), a target image is formed at the focal plane (5); and the non-secondary blocking surface view field folded-axis three-mirror telescope objective lens meets the following conditions: the FOV is 2.4 degrees x 1.7 degrees, the TTL/EFL is 1/4.4, wherein the FOV is the field of view, the TTL is the total optical length, and the EFL is the focal length;
the main mirror (1) is 20-40 mm in eccentric amount and 0.5-3 degrees in inclination relative to the direction of incident light rays;
the secondary mirror (2) is opposite to the direction of incident light, the eccentric amount of the secondary mirror (2) is 1 mm-20 mm, and the inclination amount is 0.5-3 degrees;
the eccentric amount of the three mirrors (3) is 1 mm-20 mm and the inclination amount is 2 degrees-7 degrees relative to the direction of incident light rays.
2. The non-secondary obscuration surface field of view refractive axis three-mirror telescopic objective according to claim 1, characterized in that: and placing a field stop at the middle primary real image.
3. The non-secondary obscuration surface field of view refractive axis three-mirror telescopic objective according to claim 1, characterized in that: the working wave band of the three-reflection telescope objective lens without the secondary blocking folding shaft is applicable to ultraviolet to infrared.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110538000.7A CN113238368B (en) | 2021-05-18 | 2021-05-18 | Non-secondary blocking surface view field folded-axis three-mirror telescope objective lens |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202110538000.7A CN113238368B (en) | 2021-05-18 | 2021-05-18 | Non-secondary blocking surface view field folded-axis three-mirror telescope objective lens |
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| Publication Number | Publication Date |
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| CN113238368A CN113238368A (en) | 2021-08-10 |
| CN113238368B true CN113238368B (en) | 2023-08-25 |
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| CN202110538000.7A Active CN113238368B (en) | 2021-05-18 | 2021-05-18 | Non-secondary blocking surface view field folded-axis three-mirror telescope objective lens |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115980996B (en) * | 2022-11-28 | 2024-04-30 | 中国科学院长春光学精密机械与物理研究所 | Design method of space gravitational wave telescope |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5631770A (en) * | 1994-05-26 | 1997-05-20 | Hughes Danbury Optical Systems, Inc. | Reflective scanning telescopic system on single optical bench |
| CN102023375A (en) * | 2009-09-11 | 2011-04-20 | 中国科学院西安光学精密机械研究所 | Folding axis three-reflection optical system with long focal length, no distortion and flat image field |
| CN102323671A (en) * | 2011-09-14 | 2012-01-18 | 中国科学院长春光学精密机械与物理研究所 | Telecentric off-axis three-mirror optical imaging system with real entrance pupil |
| US9134518B1 (en) * | 2010-09-23 | 2015-09-15 | Lockheed Martin Corporation | Multiple-sensor common-interface telescope |
| CN105204148A (en) * | 2015-10-15 | 2015-12-30 | 苏州大学 | Coaxial three-reflection telescope objective for planar view field without secondary blocking |
| CN106371200A (en) * | 2016-11-09 | 2017-02-01 | 苏州大学 | Broad wave band, large view field and large aperture coude three reflection afocal optical system |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108227164B (en) * | 2016-12-22 | 2020-02-07 | 清华大学 | Free-form surface off-axis three-reflection-image-side telecentric optical system |
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- 2021-05-18 CN CN202110538000.7A patent/CN113238368B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5631770A (en) * | 1994-05-26 | 1997-05-20 | Hughes Danbury Optical Systems, Inc. | Reflective scanning telescopic system on single optical bench |
| CN102023375A (en) * | 2009-09-11 | 2011-04-20 | 中国科学院西安光学精密机械研究所 | Folding axis three-reflection optical system with long focal length, no distortion and flat image field |
| US9134518B1 (en) * | 2010-09-23 | 2015-09-15 | Lockheed Martin Corporation | Multiple-sensor common-interface telescope |
| CN102323671A (en) * | 2011-09-14 | 2012-01-18 | 中国科学院长春光学精密机械与物理研究所 | Telecentric off-axis three-mirror optical imaging system with real entrance pupil |
| CN105204148A (en) * | 2015-10-15 | 2015-12-30 | 苏州大学 | Coaxial three-reflection telescope objective for planar view field without secondary blocking |
| CN106371200A (en) * | 2016-11-09 | 2017-02-01 | 苏州大学 | Broad wave band, large view field and large aperture coude three reflection afocal optical system |
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