CN113900241B - Integrated wide-spectrum double-view-field off-axis optical system sharing secondary mirror - Google Patents

Abstract

The invention provides an integrated wide-spectrum double-view-field off-axis optical system sharing a secondary mirror, which can perform wide-spectrum double-view-field imaging on a space target. The system comprises an off-axis main reflector, an integrated compound secondary reflector and an off-axis tri-reflector. The optical system forms two groups of off-axis optical systems with different view fields through sharing the secondary mirror, and after wide-spectrum light rays are incident through the off-axis main mirror, ultraviolet band light rays are reflected through the front surface of the secondary mirror to form off-axis two opposite optical systems with small view fields; the visible light and infrared band light are transmitted through the rear surface of the secondary mirror to form an equivalent off-axis three-mirror optical system with a large view field, so that switching tracking imaging of the wide spectrum double view field of the space target is realized.

Description

An integrated wide-spectrum dual-field-of-view off-axis optical system with a shared secondary mirror

technical field

The invention relates to the technical field of space optical imaging, in particular to an integrated wide-spectrum dual-view field off-axis optical system sharing a secondary mirror.

Background technique

Compared with the coaxial optical system, the center of the off-axis optical system is unobstructed, which can avoid the loss of central energy, and can also fold the optical path to make the optical system more compact and save space costs. The optical system composed of two mirrors has very important use value. Conventional Cassegrain system and Gregory system and other conventional coaxial mirrors have two serious disadvantages. One is the small field of view, and It has a central occlusion, which has a greater impact on the utilization of energy within the aperture and the concentration of light energy at the image point. The off-axis two-mirror optical system can solve the problem of central occlusion, but the field of view of the off-axis two mirrors is still relatively small, so an off-axis three-mirror optical system with a relatively large field of view can be studied. Three Mirror Astigmatism (TMA) is one of the most widely used types of long focal length space optical systems in recent years. The off-axis three-mirror system can work in a wide band from visible light to long-wave infrared, and has the advantages of large field of view and no central occlusion. An important development direction of space optical system.

At present, in the existing off-axis space optical imaging system, only off-axis two-mirror and off-axis three-mirror are studied separately. The off-axis two-mirror system limits the field of view of the system. Compared with the off-axis three-mirror system The adjustment stability of the two-anti system is poor. Therefore, it is of great significance to design a wide-spectrum dual-field-of-view off-axis optical system that takes into account both off-axis two-mirrors and off-axis three-mirror systems.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art, and propose an integrated wide-spectrum dual-field-of-view off-axis optical system with a shared secondary mirror.

Technical solution of the present invention is:

An integrated wide-spectrum dual-field-of-view off-axis optical system with an integrated secondary mirror, the system is composed of an off-axis main reflector, an integrated composite secondary mirror, and an off-axis three-reflector; the integrated composite secondary mirror includes a secondary mirror The front surface and the rear surface of the secondary mirror; the optical information of the infinite space target can be reflected to the integrated composite secondary mirror through the off-axis main reflector, wherein the ultraviolet band light information is reflected by the front surface of the secondary mirror to form an off-axis two-mirror optical system, Visible light and infrared band optical information pass through the rear surface of the secondary mirror, and then reflect off-axis three mirrors to form an equivalent off-axis three-mirror optical system; the off-axis two-reflect optical system and the off-axis three-reflect optical system share the integrated composite The secondary mirror realizes the co-imaging design of two off-axis optical systems; the integrated composite secondary mirror is a multiplex function of a lens and a mirror, and the front surface of the secondary mirror is coated with a spectroscopic film that reflects the ultraviolet band and transmits visible light and infrared bands. The rear surface of the secondary mirror is coated with an anti-reflection film for visible light and infrared bands. The off-axis optical system based on the integrated shared secondary mirror can realize wide-spectrum dual-field imaging of space targets.

Further, the surface shape of the off-axis main mirror and the off-axis three-mirror is an aspheric mirror, and the surface shape of the integrated composite secondary mirror is: the front surface of the secondary mirror is an aspheric beam splitting mirror, and the rear surface of the secondary mirror is is an aspheric mirror.

Further, the off-axis three-mirror optical system can realize large-field recognition imaging of space targets in the visible light and infrared bands, and the off-axis two-reflect optical system can realize small-field recognition imaging of space targets in the ultraviolet band.

Further, the off-axis two-mirror optical system and the off-axis three-mirror optical system are of parfocal design.

Further, the spectral band range of the integrated wide-spectrum dual-field-of-view off-axis optical system shared by the secondary mirror is from the ultraviolet band to the infrared band, the focal length of the image square is 1000-3000mm, and the off-axis two-mirror field angle is 0.05°-0.2° , The off-axis three-mirror field of view angle is 0.4°～1°.

The advantages of the present invention are:

The invention relates to an integrated wide-spectrum dual-field off-axis optical system sharing secondary mirrors, which has a simple structure and is convenient for installation and adjustment. It includes an off-axis main reflector, an integrated compound secondary mirror and an off-axis three-mirror; the optical information of an infinite space object enters through the off-axis main reflector, and the ultraviolet band optical information is reflected by the front surface of the secondary mirror to form an off-axis two-reflector Optical system: The optical information of visible light and infrared bands is transmitted through the rear surface of the secondary mirror, and then passes through off-axis three-mirror mirrors to form an equivalent off-axis three-mirror optical system. The off-axis two-mirror and off-axis three-mirror optical system share the secondary mirror to realize the co-imaging parfocal design of the two off-axis optical systems; the integrated compound secondary mirror is the multiplex function of the lens and mirror, and the front surface of the secondary mirror is coated with anti-ultraviolet band The spectroscopic film is transparent to visible light and infrared bands, and the rear surface is coated with an anti-reflection coating for visible light and infrared bands; among them, the off-axis optical system based on the integrated compound secondary mirror can realize dual-field imaging of space targets. The off-axis three-mirror of the present invention is "equivalent off-axis three-mirror". The secondary mirror of this system is an equivalent mirror application. Normally, there are only two mirrors. Compared with the normal off-axis three-mirror system, the installation and adjustment stability is higher. Therefore, the present invention provides an integrated dual-field of view off-axis optical system that shares secondary mirrors, taking into account the small field of view of the off-axis two mirrors and the poorer stability of the off-axis three mirrors compared to the two mirrors, and provides a new Design idea, at the same time, the system of the present invention is suitable for wide-spectrum imaging. The off-axis two-mirror optical system is suitable for ultraviolet narrow field of view to take into account the high resolution of the optical system. It is of great significance to overcome the limitations of the existing system.

Description of drawings

Figure 1 is a schematic diagram of an off-axis two-mirror optical system;

Figure 2 is a schematic diagram of an equivalent off-axis three-mirror optical system;

Fig. 3 is a schematic diagram of a wide-spectrum dual-field-of-view off-axis optical system with an integrated shared secondary mirror;

4 is a schematic diagram of a transfer function (MTF) of an off-axis two-mirror optical system;

5 is a schematic diagram of the transfer function (MTF) of an equivalent off-axis three-mirror optical system;

6 is a schematic diagram of a spot diagram (SPT) of an off-axis two-reflection optical system;

FIG. 7 is a schematic diagram of a spot diagram (SPT) of an equivalent off-axis three-mirror optical system.

Among them, 1 is an off-axis main mirror, 2 is an integrated composite secondary mirror, 2a is a front surface of a secondary mirror, 2b is a rear surface of a secondary mirror, and 3 is an off-axis three-mirror.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments It is some embodiments of the present invention, but not all of them. The embodiments based on the present invention all belong to the scope of protection of the present invention, but only represent selected embodiments of the present invention. Based on the implementation manners in the present invention, all other implementation manners obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

First, referring to FIG. 3 , FIG. 3 is a schematic diagram of a wide-spectrum dual-field off-axis optical system with an integrated shared secondary mirror of the present invention, which includes an off-axis primary mirror 1, an integrated composite secondary mirror 2, and an off-axis three-mirror 3; The integrated composite secondary mirror 2 includes a front surface 2a of the secondary mirror and a rear surface 2b of the secondary mirror; wherein, the off-axis two-mirror optical system and the equivalent off-axis three-mirror optical system are of parfocal design. The spectral band range is 0.2-1.7μm, the focal length of the image square is 1600mm, the off-axis two-mirror field angle is 0.1°×0.1°, and the off-axis three-mirror field angle is 0.6°×0.6°.

See Figure 1, Figure 1 is a schematic diagram of an off-axis two-mirror optical system; the entrance pupil of the system is set to 144mm, the spectral band range is 0.2-0.4μm, the field of view is 0.1°×0.1°, and the focal length is 1600mm. The parameters of the system are shown in Table 1.

Table 1 Off-axis two-mirror optical system parameter table

Component name Radius of curvature (mm) Cone coefficient Interval (mm) Off axis (mm) Eccentricity Y(mm) Angle α(°) 1 -1295.15 -1.00280 -542.98 -136 136 0 2a -351.41 -5.67186 260.07 -3.60 26.5 2.02

The aspheric surface type satisfies the following equation:

In the above formula, Z is the sagittal height from the apex of the aspheric surface when the aspheric surface is at the position of height Y along the optical axis direction, R is the paraxial curvature radius of the lens, and K is the conic coefficient.

See Figure 2, Figure 2 is a schematic diagram of an equivalent off-axis three-mirror optical system; The parameters of the reflective optical system are shown in Table 2.

Table 2 Off-axis three-mirror optical system parameter table

Component name Radius of curvature (mm) Cone coefficient Interval (mm) Off axis (mm) Eccentricity Y(mm) Angle α(°) 1 -1295.15 -1.00280 -542.98 -136 136 0 2b -374.05 -3.78164 -375.56 -3.60 26.5 2.02 3 401.33 -0.17135 709.45 -23.75 -83 -4.47

Combining Figure 1 and Figure 2, and referring to Figure 3, Figure 3 is a schematic diagram of an integrated dual-field of view off-axis optical system with a shared secondary mirror. The optical information in the ultraviolet band is reflected by the front surface 2a of the secondary mirror to form an off-axis two-mirror optical system; the optical information in the visible light and infrared bands passes through the rear surface 2b of the secondary mirror, and then passes through the off-axis three-mirror 3 to form an equivalent off-axis three-mirror optical system. The off-axis total optical system parameters are shown in Table 3.

Table 3 Off-axis three-mirror optical system parameter table

Component name Radius of curvature (mm) Cone coefficient Interval (mm) Off axis (mm) Eccentricity Y(mm) Angle α(°) 1 -1295.15 -1.00280 -542.98 -136 136 0 2a -351.41 -5.67186 -10(260.07) -3.60 26.5 2.02 2b -374.05 -3.78164 -375.56 -3.60 26.5 2.02 3 401.33 -0.17135 709.45 -23.75 -83 -4.47

In the above table, the material of the off-axis primary mirror 1, the integrated compound secondary mirror 2 and the off-axis three-mirror 3 is all selected as F_SILICA. Referring to Figure 4 and Figure 6, it can be seen from the curve in Figure 4 that the transfer functions of each field of view (0.1°×0.1°) are close to the diffraction limit, and it can be seen from the spot diagram in Figure 6 that they are all smaller than Airy The diameter of the spot indicates that the aberrations of each field of view of the off-axis two-mirror optical system are well corrected and the imaging quality is good.

Referring to Figure 5 and Figure 7, it can be seen from the curve in Figure 5 that the transfer functions of each field of view (0.6°×0.6°) are close to the diffraction limit, and it can be seen from the spot diagram in Figure 7 that they are all smaller than Airy The diameter of the spot indicates that the aberrations of each field of view of the off-axis three-mirror optical system are well corrected and the imaging quality is good.

The integrated dual-field-of-view off-axis optical system with a shared secondary mirror takes into account the characteristics of the small field of view of the off-axis two mirrors and the poorer stability of the off-axis three-mirror compared to the two mirrors, and proposes a new design idea. The system of the present invention is suitable for wide-spectrum imaging. The off-axis two-mirror optical system uses a narrow ultraviolet field of view to take into account the high resolution of the optical system, and is equivalent to off-axis three-mirror imaging for visible light and wave infrared wide field of view, which solves the problem of existing systems. limitations are of great significance.

In short, based on the integrated compound secondary mirror 2, dual-field imaging of space targets can be realized; the off-axis two-mirror optical system and the off-axis three-mirror optical system are parfocal designs; the off-axis three-mirror optical system can realize space target imaging. Large field of view recognition imaging in visible light and infrared bands, and off-axis two-mirror optical system can realize small field of view recognition imaging in ultraviolet band for space targets.

The above is only a specific implementation mode in the present invention, but the protection scope of the present invention is not limited thereto. Anyone familiar with the technology can understand the conceived transformation or replacement within the technical scope disclosed in the present invention. All should be covered within the scope of the present invention.

Claims (5)

1. An integrated broad spectrum dual-view-field off-axis optical system sharing a secondary mirror, which is characterized in that:

the system consists of an off-axis main reflector (1), an integrated composite secondary reflector (2) and an off-axis three-reflector (3); the integrated composite secondary mirror (2) comprises a secondary mirror front surface (2 a) and a secondary mirror rear surface (2 b); the light information of an infinite space target can be reflected to an integrated composite secondary mirror (2) through an off-axis main reflector (1), wherein ultraviolet band light information is reflected by a secondary mirror front surface (2 a) to form an off-axis two-reflection optical system, and visible light and infrared band light information is reflected by a secondary mirror rear surface (2 b) and then is reflected by an off-axis three-reflector (3) to form an equivalent off-axis three-reflection optical system; the off-axis two-reflection optical system and the equivalent off-axis three-reflection optical system share the integrated compound secondary mirror (2) to realize the design of co-imaging of the two off-axis optical systems; the integrated composite secondary mirror (2) is formed by multiplexing functions of a lens and a reflecting mirror, the front surface (2 a) of the secondary mirror is plated with a light splitting film which transmits visible light and infrared wave bands in the anti-ultraviolet wave band, and the rear surface (2 b) of the secondary mirror is plated with an antireflection film which transmits visible light and infrared wave bands.

2. The integrated shared secondary mirror wide-spectrum dual-field off-axis optical system of claim 1, wherein:

the surface shape of the off-axis main reflector (1) and the surface shape of the off-axis three-reflector (3) are aspheric reflectors, and the surface shape of the integrated composite secondary reflector (2) is as follows: the front surface (2 a) of the secondary mirror is an aspheric light-splitting reflecting mirror, and the rear surface (2 b) of the secondary mirror is an aspheric transmission mirror.

3. The integrated shared secondary mirror wide-spectrum dual-field off-axis optical system of claim 1, wherein:

the equivalent off-axis three-reflection optical system can realize the visible light and infrared band large view field identification imaging of the space target, and the off-axis two-reflection optical system can realize the ultraviolet band small view field identification imaging of the space target.

4. The integrated shared secondary mirror wide-spectrum dual-field off-axis optical system of claim 1, wherein:

the off-axis two-reflection optical system and the equivalent off-axis three-reflection optical system are in a parfocal design.

5. The integrated shared secondary mirror wide-spectrum dual-field off-axis optical system of claim 1, wherein:

the spectrum band range of the integrated shared secondary mirror wide spectrum double-view-field off-axis optical system is ultraviolet band to infrared band, the focal length of an image space is 1000-3000 mm, the off-axis two-reflection field angle is 0.05-0.2 degrees, and the off-axis three-reflection field angle is 0.4-1 degrees.

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