Off-axis three-mirror multi-view field optical system configuration

Abstract

The application discloses an off-axis three-mirror multi-view field optical system configuration, and belongs to the field of optics. The application comprises a reflecting primary mirror, a reflecting secondary mirror, a first folding mirror, a reflecting three-mirror, a second folding mirror, an infrared detector, a visible light detector and a large view field lens assembly arranged in sequence along an optical path. The reflecting primary mirror, the reflecting secondary mirror, the first folding mirror, the reflecting three-mirror, the second folding mirror, the infrared detector and the visible light detector constitute a small view field or a medium view field optical path. The axial position of the reflecting three-mirror is changed to switch the small view field optical path and the medium view field optical path. The third folding mirror and the fourth folding mirror of the large view field lens assembly, the infrared detector and the visible light detector constitute a large view field optical path. The radial position of the large view field lens assembly is changed to switch the small view field optical path and the large view field optical path or the medium view field optical path and the large view field optical path. The application realizes wide spectrum, high zoom ratio, high quality imaging and high optical transmittance.

Description

Technical Field

[0001] This invention belongs to the field of optics, specifically relating to an off-axis three-mirror multi-field optical system configuration. Background Technology

[0002] Depending on the distance of the target to be observed, optoelectronic observation and monitoring systems typically require optical systems with multiple focal lengths to detect, identify, and recognize targets at different distances, as well as for large-scale monitoring. Furthermore, since targets exhibit different characteristics in different spectral bands, the optical system needs to operate simultaneously in different spectral bands to improve the probability of target detection and identification. However, the types of broadband transmission optical materials are limited, and the fabrication and processing of large-aperture optical materials are difficult. Therefore, broadband optical systems generally adopt a reflective optical system configuration. The fact that mirrors do not introduce chromatic aberration is particularly advantageous for the design of broadband optical systems. At the same time, the substrate material and aperture of the mirrors are not limited, and their fabrication is relatively easy to achieve.

[0003] Common reflective optical system configurations can be divided into coaxial reflective optical system configurations and off-axis reflective optical system configurations. The biggest drawback of coaxial reflective optical system configurations is the central obstruction problem, which reduces the energy efficiency of the optical system and causes mid-frequency loss in the optical transfer function. Off-axis reflective optical system configurations solve the central obstruction problem by using an off-axis approach, thus improving energy efficiency. However, reflective optical system configurations are generally only suitable for long focal length optical systems, and their inherent disadvantage is a small field of view, making it impossible to achieve multiple fields of view. Current solutions involve setting two apertures of different positions and sizes, with different optical components used to achieve long and short focal lengths respectively. However, this results in problems such as large system volume, high system complexity, and high cost. Summary of the Invention

[0004] The technical problem to be solved:

[0005] To overcome the shortcomings of existing technologies, this invention provides an off-axis three-mirror multi-field optical system configuration. This optical system configuration is based on vector aberration theory, employs an eccentric aperture setting, and achieves mutual switching between small-field, medium-field, and large-field optical paths through axial switching of the three reflective mirrors and radial switching of the large-field mirror group. It solves the problem of realizing an off-axis three-mirror multi-field optical system configuration, resulting in unobstructed optical paths, a wide spectrum, high zoom ratio, high-quality imaging, high optical transmittance, and a compact spatial layout.

[0006] The technical solution of the present invention is: an off-axis three-mirror multi-field optical system configuration, comprising a reflective primary mirror, a reflective secondary mirror, a first folding mirror, a reflective third mirror, a second folding mirror, an infrared detector, a visible light detector, and a large field-of-view mirror group arranged sequentially along the optical path; the large field-of-view mirror group includes a third folding mirror and a fourth folding mirror;

[0007] The optical path of the small field-of-view or medium field-of-view broadband optical system is composed of a primary reflector, a secondary reflector, a first folding reflector, a third reflector, a second folding reflector, an infrared detector, and a visible light detector. The switching between the small field-of-view broadband optical system and the medium field-of-view broadband optical system can be completed by changing the axial position of the third reflector.

[0008] The optical path of the wide field-of-view broadband optical system is composed of the third and fourth folded mirrors, the infrared detector, and the visible light detector of the wide field-of-view mirror group. By changing the radial position of the wide field-of-view mirror group, the switching between the optical path of the small field-of-view broadband optical system and the optical path of the wide field-of-view broadband optical system, or between the optical path of the medium field-of-view broadband optical system and the optical path of the wide field-of-view broadband optical system, can be completed.

[0009] A further technical solution of the present invention is that the optical paths of the small field-of-view broadband optical system and the medium field-of-view broadband optical system adopt an off-axis reflective optical system configuration, and the optical path of the large field-of-view broadband optical system adopts a coaxial optical system configuration.

[0010] A further technical solution of the present invention is: the primary reflector is a parabolic surface, the secondary reflector is a high-order aspherical surface, and the third reflector is a free-form surface symmetrical about the meridional plane.

[0011] A further technical solution of the present invention is as follows: the optical parameters of the optical paths of the small field-of-view broadband optical system and the medium field-of-view broadband optical system are as follows:

[0012]

[0013]

[0014] A further technical solution of the present invention is: the aspherical coefficients of the primary mirror, the secondary mirror, and the third mirror are:

[0015] Reflective primary mirror -1 —— —— —— —— secondary mirror -0.3654 1.2660E-08 -8.1223E-14 1.0876E-18 -6.6462E-24 Reflective three-mirror 1.7724 —— —— —— ——

[0016] A further technical solution of the present invention is as follows: the optical parameters of the optical path of the large field-of-view broadband optical system are as follows:

[0017] Third folding reflector infinity -153.25 Fourth folding mirror infinity 85.81

[0018] A further technical solution of the present invention is that the position switching of the three reflective mirrors, the second folding reflector, and the large field-of-view mirror group is completed by motor drive.

[0019] A further technical solution of the present invention is that the materials used to manufacture the primary mirror, secondary mirror, and tertiary mirror are microcrystalline glass, fused silica, or silicon carbide.

[0020] A further technical solution of the present invention is: a mid-wave infrared focal length range of 1200mm~800mm~220mm, and a visible light focal length range of 1800mm~1200mm~330mm; zoom ratio: 5.45. × Optical system F-numbers: f / 5.5 for infrared and f / 8 for visible light.

[0021] A further technical solution of the present invention is: the detector is a cooled infrared focal plane detector with a resolution of 1280×1024 and a visible light focal plane detector with a resolution of 5120×4096, with a visible light spectral range of 0.6μm to 0.9μm and a mid-wave infrared spectral range of 3μm to 5μm.

[0022] Beneficial effects

[0023] The beneficial effects of this invention are as follows: This invention achieves a small field-of-view optical path through off-axis aperture; it achieves the conversion between small and medium field-of-view optical paths through axial switching of the three reflective mirrors; and it achieves the conversion between large and small field-of-view optical paths, and between large and medium field-of-view optical paths, through radial switching of the large field-of-view mirror group and the second folding mirror. This solves the layout problem of off-axis three-mirror multi-field-of-view optical systems, and results in unobstructed optical paths, a wide spectrum, high zoom ratio, high-quality imaging, and high optical transmittance, all within a compact spatial layout. Specific advantages are as follows:

[0024] 1. Off-axis three-mirror multi-field optical path configuration;

[0025] The conversion between small and medium field-of-view optical paths is achieved by axial switching of the three reflective mirrors. The conversion between large and small field-of-view optical paths, and between large and medium field-of-view optical paths, is achieved by radial switching of the large field-of-view mirror group and the second folding mirror.

[0026] 2. Broad spectrum common aperture;

[0027] By adopting a reflective optical system configuration, a common aperture design for visible light and mid-wave infrared light was achieved.

[0028] 3. No central obstruction;

[0029] By adopting an off-axis reflective optical system configuration, the central obstruction problem of the coaxial reflective optical system configuration is solved.

[0030] 4. Excellent image quality;

[0031] By utilizing special optical surface shapes such as quadric surfaces, higher-order aspherical surfaces, and freeform surfaces, aberrations in off-axis optical systems are corrected, balancing various asymmetric aberrations and achieving excellent image quality.

[0032] The off-axis three-mirror multi-field optical system configuration design of the present invention is based on vector aberration theory and paraxial optical system theory calculation and analysis. It determines that the small and medium field of view optical paths adopt an off-axis reflective optical system configuration, while the large field of view optical path adopts a coaxial optical system configuration. By optimizing optical structure parameters, balancing aberrations, and using special surface shapes such as quadratic surfaces, higher-order aspherical surfaces, and freeform surfaces, the asymmetric aberrations of the optical system are corrected, so that the image quality reaches the optimal level. Attached Figure Description

[0033] Figure 1 This is a diagram of the off-axis three-mirror multi-field optical path layout of the present invention;

[0034] Figure 2 This is the optical path diagram of the off-axis three-mirror small field of view of the present invention;

[0035] Figure 3 This is the field-of-view optical path diagram of the off-axis three-mirror system of this invention;

[0036] Figure 4 This is the optical path diagram of the off-axis three-mirror large field of view of the present invention;

[0037] Figure 5 This is a graph of the mid-wave infrared optical transfer function of the off-axis three-mirror system with a small field of view according to the present invention;

[0038] Figure 6 This is the optical transfer function diagram of the off-axis three-mirror system with a small field of view for visible light in this invention;

[0039] Figure 7 This is a mid-wave infrared optical transfer function diagram of the off-axis three-lens reflex camera in the field of view of this invention;

[0040] Figure 8 This is a diagram of the visible light optical transfer function in the field of view of the off-axis three-lens reflex camera of this invention;

[0041] Figure 9 This is a graph of the mid-wave infrared optical transfer function of the off-axis three-mirror display with a large field of view according to the present invention;

[0042] Figure 10 This is the optical transfer function diagram of the off-axis three-lens reflex camera with a large field of view for visible light in this invention.

[0043] Explanation of reference numerals in the attached diagram: 1-reflective primary mirror, 2-reflective secondary mirror, 3-first folding mirror, 4-reflective triple mirror, 5-second folding mirror, 6-large field-of-view mirror group (composed of third folding mirror 6-1 and fourth folding mirror 6-2), 7-infrared detector, 8-visible light detector. Detailed Implementation

[0044] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0045] Existing technologies, by setting two apertures of different positions and sizes and using different optical components to achieve long and short focal lengths respectively, result in problems such as large system volume, high system complexity, and high cost. This invention provides an off-axis three-mirror multi-field optical system configuration, including a primary mirror 1, a secondary mirror 2, a first folding mirror 3, a third mirror 4, a second folding mirror 5, an infrared detector 7, and a visible light detector 8 arranged sequentially along the optical path, and a large field-of-view lens group 6 movably disposed between the incident light source and the primary mirror; the large field-of-view lens group 6 includes a third folding mirror 6-1 and a fourth folding mirror 6-2; the system consists of the primary mirror 1, secondary mirror 2, first folding mirror 3, third mirror 4, second folding mirror 5, infrared detector 7, and visible light detector 8. The optical path of the small or medium field-of-view broadband optical system is formed by changing the axial position of the three reflective mirrors 4. The optical path of the small field-of-view broadband optical system and the medium field-of-view broadband optical system are switched by changing the axial position of the three reflective mirrors 4. The optical path of the large field-of-view broadband optical system is formed by the third folding mirror 6-1 and the fourth folding mirror 6-2 of the large field-of-view mirror group 6, the infrared detector 7, and the visible light detector 8. The optical path of the large field-of-view broadband optical system is formed by changing the radial position of the large field-of-view mirror group 6. The optical path of the small field-of-view broadband optical system is switched with the large field-of-view broadband optical system, or the optical path of the medium field-of-view broadband optical system is switched with the large field-of-view broadband optical system.

[0046] Among them, the optical paths of the small field-of-view optical system and the medium field-of-view optical system adopt an off-axis reflective optical system configuration, while the optical path of the large field-of-view optical system adopts a coaxial optical system configuration.

[0047] The above technical solution will be further described in detail below with reference to the accompanying drawings:

[0048] Reference Figure 1 The diagram illustrates the optical path of an off-axis three-mirror multi-field optical system configuration in this embodiment. This diagram is based on vector aberration theory, employs an eccentric aperture setup in the optical system, and utilizes axial switching of the three reflective mirrors and radial switching of the large-field-of-view lens group to realize the optical path principles for the small-field-of-view, medium-field-of-view, and large-field-of-view optical paths, respectively. The optical system configuration includes: a primary reflector 1, a secondary reflector 2, a first folding reflector 3, three reflective mirrors 4, a second folding reflector 5, a large-field-of-view lens group 6, an infrared detector 7, and a visible light detector 8. The large-field-of-view lens group 6 consists of a third folding reflector 6-1 and a fourth folding reflector 6-2.

[0049] Reference Figure 1 and Figure 2 As shown, the optical path follows the optical axis O1O1' and consists of a primary reflector 1, a secondary reflector 2, a first folding reflector 3, a third reflector 4 (position A1), a second folding reflector 5 (position C1), a large field-of-view mirror group 6 (position B1), an infrared detector 7, and a visible light detector 8, forming the optical path of a small field-of-view broadband optical system.

[0050] Reference Figure 1 and Figure 3 As shown, the optical path follows the optical axis O2O2' and consists of a primary reflector 1, a secondary reflector 2, a first folding reflector 3, a third reflector 4 (position A2), a second folding reflector 5 (position C1), a wide field-of-view mirror group 6 (position B1), an infrared detector 7, and a visible light detector 8, forming the optical path of a mid-field wide-spectrum optical system.

[0051] Reference Figure 1 and Figure 4 As shown, the optical path follows the optical axis O1O1' to form the optical path of the large field-of-view mirror group 6 (position B2), the second folding mirror 5 (position C2), the infrared detector 7, and the visible light detector 8, thus constituting the optical path of the large field-of-view broadband optical system.

[0052] When the lens group is in the small field of view optical system optical path, the reflective three-mirror 4 is driven by the motor to switch from position A1 to position A2 to form a medium field of view optical path, and vice versa, to realize the switching between small field of view and medium field of view.

[0053] When the lens group is in the optical path of the small or medium field of view optical system, the large field of view lens group 6 is driven by the motor to switch from position B1 to position B2, and at the same time the second folding mirror 5 is driven by the motor to switch from position C1 to position C2, forming a large field of view optical path. The reverse is also true, realizing the switching between small and large field of view, and medium and large field of view.

[0054] Specifically, the primary reflector 1 is a parabolic surface, the secondary reflector 2 is a high-order aspherical surface, and the tertiary reflector 4 is a free-form surface symmetrical about the meridional plane. The materials used to manufacture these reflectors can be glass-ceramic, fused silica, and silicon carbide.

[0055] Specifically, the mid-wave infrared focal length range is 1200mm~800mm~220mm, and the visible light focal length range is 1800mm~1200mm~330mm; zoom ratio: 5.45 × Optical system F-number: f / 5.5 (infrared), f / 8 (visible light).

[0056] Specifically, the applicable detectors are a 1280×1024 cooled infrared focal plane detector and a 5120×4096 visible light focal plane detector, with a visible light spectral range of 0.6μm to 0.9μm and a mid-wave infrared spectral range of 3μm to 5μm.

[0057] Reference Figure 1 As shown, this optical path diagram is a schematic diagram of the implementation principle of an off-axis three-mirror multi-field optical system. The optical system includes a primary mirror 1, a secondary mirror 2, a first folding mirror 3, a triple mirror 4, a second folding mirror 5, a large field-of-view mirror group 6 (composed of a third folding mirror 6-1 and a fourth folding mirror 6-2), an infrared detector 7, and a visible light detector 8.

[0058] The specific optical parameters are shown in the table below.

[0059] Table 1. Optical Path Parameters of Small and Medium Field-of-View Wide-Spectrum Optical Systems (Unit: mm)

[0060]

[0061] Table 2 Optical Path Parameters of a Wide Field-of-View Broad-Spectrum Optical System (Unit: mm)

[0062] Third folding reflector 6-1 infinity -153.25 Fused Quartz Fourth folding reflector 6-2 infinity 85.81 Fused Quartz

[0063] Table 3 Aspherical Coefficients

[0064]

[0065] Table 4. Coefficients of the 4-XY Polynomials for a Reflective Three-Mirror System

[0066] <![CDATA[Y 0 ]]> —— 0 -1.4364E-9 -6.4022E-13 1.6216E-16 -4.9355E-21 <![CDATA[Y 1 ]]> 0.0049 0 0 0 0 —— <![CDATA[Y 2 ]]> 1.1096E-5 -4.6102E-9 -3.4708E-13 1.8844E-16 -3.9878E-20 —— <![CDATA[Y 3 ]]> 3.1683E-7 0 0 0 —— —— <![CDATA[Y 4 ]]> 1.0781E-9 -1.3363E-13 5.6841E-18 -4.8982E-21 —— —— <![CDATA[Y 5 ]]> -3.3036E-11 0 0 —— —— —— <![CDATA[Y 6 ]]> -1.4508E-12 1.7594E-17 7.4663E-22 —— —— —— <![CDATA[Y 7 ]]> -1.5785E-14 0 —— —— —— —— <![CDATA[Y 8 ]]> -5.7511E-17 -1.0944E-21 —— —— —— —— <![CDATA[Y 9 ]]> 1.3984E-19 —— —— —— —— —— <![CDATA[Y 10 ]]> 1.1181E-21 —— —— —— —— ——

[0067] Table 5. Eccentricity and Inclination Parameters

[0068] Reflective primary mirror 1 -30.76 0 First folding reflector 3 0 -55.88 Second folding reflector 5 0 -34.12

[0069] The equation for an aspherical surface is:

[0070]

[0071] Where: r — distance from the optical axis;

[0072] R—radius of curvature at the vertex of the aspherical surface;

[0073] k — constant of the quadratic curve;

[0074] A, B, C, D – aspherical coefficients.

[0075] The XY polynomial equation is:

[0076]

[0077] Where: r — distance from the optical axis;

[0078] c—radius of curvature at the vertex;

[0079] k — constant of the quadratic curve;

[0080] C j — Monomial x m y n coefficient.

[0081] In summary, this embodiment achieves a small field-of-view optical path by using an off-axis aperture, and converts between the small and medium field-of-view optical paths by axial switching of the three reflective mirrors. By radial switching of the large field-of-view mirror group and the second folding mirror, it achieves the conversion between the large and small field-of-view optical paths, as well as between the large and medium field-of-view optical paths. Furthermore, it features an unobstructed optical path, a wide spectrum, a high zoom ratio, high-quality imaging, and high optical transmittance, all within a compact spatial layout.

[0082] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. An off-axis three-mirror multi-field optical system configuration, characterized in that: It includes a reflective primary mirror, a reflective secondary mirror, a first folding mirror, a reflective third mirror, a second folding mirror, an infrared detector, a visible light detector, and a large field-of-view mirror assembly arranged sequentially along the optical path; the large field-of-view mirror assembly includes a third folding mirror and a fourth folding mirror. The optical path of the small field-of-view or medium field-of-view broadband optical system is composed of a primary reflector, a secondary reflector, a first folding reflector, a third reflector, a second folding reflector, an infrared detector, and a visible light detector. The switching between the small field-of-view broadband optical system and the medium field-of-view broadband optical system can be completed by changing the axial position of the third reflector. The optical path of the wide field-of-view broadband optical system is composed of the third and fourth folded mirrors of the wide field-of-view mirror group, an infrared detector, and a visible light detector. By changing the radial position of the wide field-of-view mirror group, the switching between the optical path of the small field-of-view broadband optical system and the optical path of the wide field-of-view broadband optical system, or between the optical path of the medium field-of-view broadband optical system and the optical path of the wide field-of-view broadband optical system, can be completed.

2. The off-axis three-mirror multi-field optical system configuration according to claim 1, characterized in that: The optical paths of the small field-of-view broadband optical system and the medium field-of-view broadband optical system adopt an off-axis reflective optical system configuration, while the optical path of the large field-of-view broadband optical system adopts a coaxial optical system configuration.

3. The off-axis three-mirror multi-field optical system configuration according to claim 1, characterized in that: The primary reflector is a parabolic surface, the secondary reflector is a higher-order aspherical surface, and the tertiary reflector is a free-form surface symmetrical about the meridional plane.

4. The off-axis three-mirror multi-field optical system configuration according to claim 3, characterized in that: The optical parameters of the small field-of-view broadband optical system and the medium field-of-view broadband optical system are as follows:

5. The off-axis three-mirror multi-field optical system configuration according to claim 4, characterized in that: The aspherical coefficients of the primary mirror, secondary mirror, and tertiary mirror are:

6. The off-axis three-mirror multi-field optical system configuration according to claim 3, characterized in that: The optical parameters of the optical path of the large field-of-view broadband optical system are as follows: 。 7. The off-axis three-mirror multi-field optical system configuration according to claim 1, characterized in that: The position switching of the three reflective mirrors, the second folding reflector, and the wide field-of-view mirror group is accomplished by motor drive.

8. The off-axis three-mirror multi-field optical system configuration according to claim 1, characterized in that: The primary mirror, secondary mirror, and tertiary mirror are made of microcrystalline glass, fused silica, or silicon carbide.

9. The off-axis three-mirror multi-field optical system configuration according to claim 1, characterized in that: Mid-wave infrared focal length range: 1200mm~800mm~220mm; visible light focal length range: 1800mm~1200mm~330mm; zoom ratio: 5.45 × Optical system F-numbers: f / 5.5 for infrared and f / 8 for visible light.

10. The off-axis three-mirror multi-field optical system configuration according to any one of claims 1-9, characterized in that: The detectors are a cooled infrared focal plane detector with a resolution of 1280×1024 and a visible light focal plane detector with a resolution of 5120×4096, with a visible light spectral range of 0.6μm to 0.9μm and a mid-wave infrared spectral range of 3μm to 5μm.

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