阅读说明：本技术 一种离轴两反多光合一光学主系统 (Off-axis two-mirror multi-optical-in-one optical main system ) 是由 曲贺盟 管海军 王超 于 2021-08-23 设计创作，主要内容包括：本发明涉及一种离轴两反多光合一光学主系统,该系统包括离轴主镜和离轴次镜；所述的离轴主镜和离轴次镜均为正光焦度反射镜,且反射面均为旋转对称偶次非球面；离轴主镜将入射的平行光线汇聚在自身的焦点处,该焦点处设置一次像面视场光阑；离轴次镜焦点与离轴主镜焦点重合,经过焦点的光线通过离轴次镜反射后出射平行光线。本发明同时解决了目前机载光学载荷主系统存在中心遮拦和系统体量大的技术难题,理论上可以实现全谱段成像探测,有效的抑制了各谱段分别成像的相互干扰,各系统均能实现最优像质,适合机载环境的大口径长焦距系统的应用。(The invention relates to an off-axis two-mirror multi-in-one optical main system, which comprises an off-axis main mirror and an off-axis secondary mirror; the off-axis primary mirror and the off-axis secondary mirror are both positive focal power reflectors, and the reflecting surfaces are both rotationally symmetric even-order aspheric surfaces; the off-axis primary mirror converges the incident parallel light rays at the focus of the off-axis primary mirror, and a primary image surface field diaphragm is arranged at the focus; the focus of the off-axis secondary mirror is coincided with the focus of the off-axis primary mirror, and the light rays passing through the focus are reflected by the off-axis secondary mirror and then emit parallel light rays. The invention simultaneously solves the technical problems of central obstruction and large system mass of the conventional airborne optical load main system, theoretically can realize full-spectrum imaging detection, effectively inhibits the mutual interference of respective imaging of each spectrum, can realize optimal image quality of each system, and is suitable for application of a large-caliber long-focus system in an airborne environment.)

1. An off-axis two-mirror multi-in-one optical primary system is characterized by comprising an off-axis primary mirror L1 and an off-axis secondary mirror L2; the off-axis primary mirror L1 and the off-axis secondary mirror L2 are both positive focal power reflectors, and the reflecting surfaces are both rotationally symmetric even aspheric surfaces; the off-axis main mirror L1 converges the incident parallel light rays at the focus of the off-axis main mirror L1, and a primary image surface field diaphragm S1 is arranged at the focus; the focal point of the off-axis secondary mirror L2 is coincided with the focal point of the off-axis primary mirror L1, and the light rays passing through the focal point are reflected by the off-axis secondary mirror L2 to emit parallel light rays.

2. The off-axis two-mirror multi-in-one optical primary system according to claim 1, wherein the reflecting surfaces of the off-axis primary mirror L1 and the off-axis secondary mirror L2 are both paraboloids.

3. The off-axis two-mirror multi-in-one optical master system according to claim 2, wherein the radius of curvature of the off-axis master mirror L1 is from-295 mm to-275 mm; the curvature radius of the off-axis secondary mirror L2 is 60 mm-70 mm; the distance between the vertexes of the off-axis primary mirror and the off-axis secondary mirror along the negative direction of the optical axis is-172 mm to-176 mm.

4. The off-axis two-mirror multi-in-one optical primary system according to claim 3, wherein the off-axis secondary mirror L2 has an alpha rotation angle in the X-direction of-0.1 ° to-0.5 °, and an eccentricity in the Y-direction of 0.1 to 0.5 mm.

5. The off-axis two-mirror multi-in-one optical primary system according to claim 1, wherein the reflecting surface of the off-axis primary mirror L1 is a high-order aspheric surface, and the reflecting surface of the off-axis secondary mirror L2 is a paraboloid.

6. The off-axis two-mirror multi-in-one optical master system according to claim 5, wherein the radius of curvature of the off-axis master mirror L1 is from-295 mm to-275 mm; the curvature radius of the off-axis secondary mirror L2 is 60 mm-70 mm; the distance between the vertexes of the off-axis primary mirror and the off-axis secondary mirror along the negative direction of the optical axis is-172 mm to-176 mm.

7. An off-axis two-mirror and multi-light-in-one optical master system according to claim 5 or 6, wherein the off-axis master mirror L1 has a reflection surface profile parameter k-1.05 to-0.57, A-0, B-1E-17 to 9E-17, C-1E-22 to 9E-22, and D-1E-26 to 9E-26.

8. The off-axis two-mirror multi-in-one optical primary system according to claim 1, wherein the reflecting surface of the off-axis primary mirror L1 is a paraboloid and the reflecting surface of the off-axis secondary mirror L2 is a hyperboloid.

9. The off-axis two-mirror multi-in-one optical master system according to claim 1, wherein the radius of curvature of the off-axis master mirror L1 is from-295 mm to-275 mm; the curvature radius of the off-axis secondary mirror L2 is 60 mm-70 mm; the distance between the vertexes of the off-axis primary mirror and the off-axis secondary mirror along the negative direction of the optical axis is-172 mm to-176 mm.

10. An off-axis two-mirror multi-in-one optical primary system according to claim 8 or 9, wherein the off-axis secondary mirror L2 has a face parameter k-1.024 to-3.5.

Technical Field

The invention belongs to the technical field of optical design, and relates to an off-axis two-mirror multi-in-one optical main system.

Background

At present, the multi-detection distance and the resolution of the airborne pod in China only meet the use at low altitude or medium and low altitude. In order to meet the requirement of high-altitude and ultra-long-distance all-day detection, the optical load must increase the focal length and the caliber, and meanwhile, the detection waveband is increased, so that high-resolution visibility is used for fine observation and identification in the daytime; the infrared medium wave and the infrared long wave are used for remote detection and identification of different observation environments at night; the laser is used for distance determination, and detection information of a distance dimension is added to the system. The size and weight of optical loads in an aviation nacelle are particularly important, and the various long-focus and large-caliber optical loads are separately arranged, so that effective and reasonable arrangement of space is difficult to realize, and the systems are mutually restricted, and the optimal system performance cannot be achieved.

In order to solve the contradiction that the loads of all spectral bands of all airborne pod optical systems cannot realize the maximum design, more and more systems adopt a main system reflection type common-caliber and a rear group independent spectral imaging system to carry out system planning, and the problem of imaging restriction of all spectral bands of the systems is well solved. However, most of the main systems adopt an RC coaxial catadioptric optical structure form, so that although the contradiction problem that the system is large in size can be solved by ensuring that all wave bands of the system are imaged respectively after passing through the main systems at the same time, the secondary mirror in the system is blocked, and the effective light-passing aperture and the imaging performance of the system are greatly reduced; the off-axis three-reflector optical system without the central barrier is optimal in optical performance, but the inherent defects of the off-axis three-reflector optical system are that the system is large in size, and the main mirror and the three mirrors which are arranged off-axis in the Y direction cause the system to be overlarge in size, so that the off-axis three-reflector optical system is difficult to adapt to the application of an airborne pod environment.

Disclosure of Invention

The technical problem to be solved by the invention is to provide an off-axis two-mirror multi-optical-in-one optical main system, which can effectively condense incident light, realize imaging detection of a large-aperture full-spectrum section without central blocking in an airborne environment and has small volume.

In order to solve the above technical problem, the off-axis two-mirror multi-in-one optical primary system of the present invention comprises an off-axis primary mirror L1 and an off-axis secondary mirror L2; the off-axis primary mirror L1 and the off-axis secondary mirror L2 are both positive focal power reflectors, and the reflecting surfaces are both rotationally symmetric even aspheric surfaces; the off-axis main mirror L1 converges the incident parallel light rays at the focus of the off-axis main mirror L1, and a primary image surface field diaphragm S1 is arranged at the focus; the focal point of the off-axis secondary mirror L2 is coincided with the focal point of the off-axis primary mirror L1, and the light rays passing through the focal point are reflected by the off-axis secondary mirror L2 to emit parallel light rays.

And the reflecting surfaces of the off-axis primary mirror L1 and the off-axis secondary mirror L2 are paraboloids.

The curvature radius of the off-axis primary mirror L1 is-295 mm-275 mm; the curvature radius of the off-axis secondary mirror L2 is 60 mm-70 mm; the distance between the vertexes of the off-axis primary mirror and the off-axis secondary mirror along the negative direction of the optical axis is-172 mm to-176 mm.

The alpha rotation angle in the X direction of the off-axis secondary mirror L2 is-0.1 degree to-0.5 degree, and the eccentricity in the Y direction is 0.1 mm to 0.5 mm.

The reflecting surface of the off-axis primary mirror L1 adopts a high-order aspheric surface, and the reflecting surface of the off-axis secondary mirror L2 is a paraboloid.

The curvature radius of the off-axis primary mirror L1 is-295 mm-275 mm; the curvature radius of the off-axis secondary mirror L2 is 60 mm-70 mm; the distance between the vertexes of the off-axis primary mirror and the off-axis secondary mirror along the negative direction of the optical axis is-172 mm to-176 mm.

The reflecting surface profile parameter of the off-axis primary mirror L1 is-1.05 to-0.57, A is 0, B is 1E-17 to 9E-17, C is 1E-22 to 9E-22, and D is 1E-26 to 9E-26.

The reflecting surface of the off-axis primary mirror L1 is a paraboloid, and the reflecting surface of the off-axis secondary mirror L2 is a hyperboloid.

The curvature radius of the off-axis primary mirror L1 is-295 mm-275 mm; the curvature radius of the off-axis secondary mirror L2 is 60 mm-70 mm; the distance between the vertexes of the off-axis primary mirror and the off-axis secondary mirror along the negative direction of the optical axis is-172 mm to-176 mm.

The surface type parameter of the off-axis secondary mirror L2 is-1.024-3.5.

The invention provides an off-axis two-mirror main optical system suitable for airborne optical loads, which is used for collimating and condensing energy emitted by a target at infinity and is used for light splitting imaging of each band detection system of a rear group. The system adopts a total reflection type optical scheme, theoretically, full-spectrum imaging detection can be realized, the system can effectively reduce beam at infinity at present and is used for back component light splitting, mutual interference of respective imaging of each spectrum section is effectively inhibited, optimal image quality can be realized for each system, the structural form of the system is simplified, and the system is suitable for application of a large-caliber long-focus system in an airborne environment.

The invention adopts an off-axis two-reflection optical structure form as a multi-light-in-one optical load main system of the airborne nacelle to effectively condense incident light rays and further perform light splitting and respective imaging of each wave band, thereby realizing imaging detection of a large-aperture full-spectrum band without central blocking of an airborne environment and meeting the requirements of large aperture, miniaturization and light weight of the system.

The invention aims to solve the design problem of realizing large-caliber, long-focus and multispectral imaging under the conditions of airborne environment and limited space volume, and compared with the traditional coaxial catadioptric and off-axis three-mirror system, the system has no central blocking, and is more compact in size and suitable for airborne environment application. The invention adopts a reflection type structure form, obviously compresses the imaging aperture of the multispectral segment, has no color difference problem, and solves the contradiction between the large aperture and the large volume of the multispectral segment. The invention adopts an off-axis optical structure form, and eliminates the situations of effective caliber reduction and imaging quality reduction caused by central blocking of a coaxial reflection type main system. The two-inverse structure form is adopted, and the problem of large off-axis three-inverse structure size is obviously solved. Compared with the prior art, the method has the following advantages and positive effects:

1. the off-axis two-mirror multi-in-one optical main system adopts an off-axis two-mirror structure form, the working waveband can realize a full spectrum band, and the magnification can reach more than 4 times;

2. the off-axis two-reflector multi-light-in-one optical main system has a compact structural form, small volume and light weight;

3. all elements of the off-axis two-mirror multi-light-in-one optical main system adopt reflecting elements, and the optical main system has the technical characteristics of no chromatic aberration, no central blocking, low distortion and the like.

Drawings

Fig. 1 is a schematic structural view of the present invention.

Fig. 2 is a modulation transfer function curve of embodiment 1 of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the following drawings and examples, it being understood that the specific embodiments described herein are illustrative of the invention only and are not limiting. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.

In the description of the present invention, unless otherwise expressly specified or limited, the terms "connected," "connected," and "fixed" are to be construed broadly, e.g., as meaning permanently connected, removably connected, or integral to one another; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other suitable relationship. The specific meanings of the above terms in the present invention can be specifically understood in specific cases by those of ordinary skill in the art.

In the present invention, unless otherwise expressly stated or limited, "above" or "below" a first feature means that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact with each other via another feature therebetween. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," or "beneath" a second feature includes the first feature being directly under or obliquely below the second feature, or simply means that the first feature is at a lesser elevation than the second feature.

In the description of the present embodiment, the terms "upper", "lower", "left", "right", and the like are used in the orientation or positional relationship shown in the drawings only for convenience of description and simplicity of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used only for descriptive purposes and are not intended to have a special meaning.

Example 1

As shown in fig. 1, the off-axis two-mirror multi-in-one optical primary system of the present invention includes an off-axis primary mirror L1 and an off-axis secondary mirror L2; the off-axis primary mirror L1 and the off-axis secondary mirror L2 are both positive focal power reflectors, the reflecting surface is a rotationally symmetric even aspheric surface, and the surface equation is as follows:

wherein z is the rotational symmetry axis of the aspheric surface, c is the curvature radius of the rotationally symmetric even aspheric surface, h is the radial coordinate, and k is the conic coefficient.

The off-axis primary mirror L1 is used for imaging an infinite target to a primary image surface, and the off-axis secondary mirror L2 is used for condensing an image formed by the off-axis primary mirror L1 and emitting parallel rays with a certain multiplying power.

The off-axis main mirror L1 converges incident parallel light rays at the focus of the off-axis main mirror L1, a primary image plane field diaphragm S1 is arranged at the focus, and a primary image plane field diaphragm S1 is obliquely arranged, so that external stray radiation exceeding the imaging field of the system can be shielded; the focal point of the off-axis secondary mirror L2 is coincided with the focal point of the off-axis primary mirror L1, and light rays passing through the focal point are reflected by the off-axis secondary mirror L2 and then emitted to form parallel light rays for respectively imaging rear component light.

The reflecting surfaces of the off-axis primary mirror L1 and the off-axis secondary mirror L2 are paraboloids, namely k is-1.

The curvature radius of the off-axis primary mirror L1 is-295 mm-275 mm; the curvature radius of the off-axis secondary mirror L2 is 60 mm-70 mm; the distance between the vertexes of the off-axis primary mirror and the off-axis secondary mirror along the negative direction of the optical axis is-172 mm to-176 mm.

Examples 2 and 3 are different from example 1 in the reflection surface parameter, and the others are the same.

The reflector parameters for the off-axis primary mirror L1 and the off-axis secondary mirror L2 of examples 1-3 are shown in Table 1. In the table, R is the radius of curvature of the reflecting surface, and d is the distance between the vertex of the off-axis primary mirror L1 and the vertex of the off-axis secondary mirror L2 in the negative direction of the optical axis.

TABLE 1

The technical indices of the examples 1-3 are shown in Table 2:

TABLE 2

As shown in fig. 2, the variation of the wave aberration of each wavelength band with the field of view in embodiment 1 is shown, and the wave aberration of the whole field of view is less than 0.029 λ (λ ═ 632 nm).

As shown in fig. 2, the abscissa is the spatial frequency, the unit is lp/mm, the maximum is 733.7, and the ordinate is the normalized modulation transfer function, and it can be seen from fig. 2 that the modulation transfer functions in the 0-field meridional direction (solid line) and the sagittal direction (dotted line), and the modulation transfer functions in the y-direction 1-field meridional direction (dotted line) and the sagittal direction (star line) are all close to the diffraction limit. The collimation of each field of view of the off-axis two-mirror multi-in-one optical main system is shown in table 3.

TABLE 3

In table 3, the first column is the corresponding detection field of view, and the second column is the divergence angle of the outgoing light rays of different field of view; table 3 shows that the collimation of the emergent light is less than 0.047mrad, which can meet the requirements of receiving and imaging at different wave bands of the rear group.

Example 4

As shown in fig. 1, the present embodiment is different from embodiment 1 in that the reflection surface of the off-axis primary mirror L1 adopts a high-order aspheric surface, and the surface shape parameter of the high-order aspheric surface is k: -1.05 to-0.57; a: 0; b: 1E-17-9E-17; c: 1E-22 to 9E-22; d: 1E-26-9E-26, the purpose is to further increase the imaging field of view of the off-axis two-mirror multi-in-one optical main system, the high-order aspheric surface has stronger correction capability on off-axis asymmetric coma aberration and astigmatism, the off-axis aberration is obviously increased along with the increase of the field of view of the system, and the addition of the high-order aspheric surface is beneficial to the increase of the field of view of the main system.

Examples 5 and 6 are different from example 4 in the reflection surface parameter, and the others are the same.

The reflector parameters for the off-axis primary mirror L1 and the off-axis secondary mirror L2 of examples 5-6 are shown in Table 4. In the table, R is the radius of curvature of the reflecting surface, and d is the distance between the vertex of the off-axis primary mirror L1 and the vertex of the off-axis secondary mirror L2 in the negative direction of the optical axis.

TABLE 4

The technical indexes of this example 4 are shown in table 5:

TABLE 5

Example 7

As shown in fig. 1, the difference between this embodiment and embodiment 1 is that the off-axis secondary lens L2 adds an inclination amount (i.e., an X-direction alpha rotation angle) and a Y-direction eccentricity amount instead of only off-axis, which aims to correct off-axis asymmetric curvature of field caused by positive focal power of both the off-axis primary lens L1 and the off-axis secondary lens L2 in the system, so that the curvature of field of the rear component optical system is corrected more easily, and the optical axis of the emergent ray and the optical axis of the incident ray can be processed in parallel, which is more suitable for the layout of the rear component optical elements; the alpha rotation angle in the X direction is-0.1 to-0.5 degrees, and the eccentricity in the Y direction is 0.1 to 0.5 mm.

Examples 8 and 9 are different from example 7 in the reflection surface parameter, the inclination amount (i.e., the X-direction alpha rotation angle) and the Y-direction eccentricity amount, and the others are the same.

The parameters of the reflecting surfaces of the off-axis primary mirror L1 and the off-axis secondary mirror L2, the eccentricity in the Y direction and the rotation angle in the X direction alpha of the embodiments 7-9 are shown in Table 6. In the table, R is a curvature radius of the reflecting surface, d is a distance between the vertex of the off-axis primary mirror L1 and the vertex of the off-axis secondary mirror L2 along the negative direction of the optical axis, h is a Y-direction eccentricity (i.e., a distance between the vertex of the off-axis secondary mirror and a generatrix (a chain line in fig. 1) of the off-axis primary mirror L1), and θ is an X-direction alpha rotation angle (i.e., an included angle between a vertex tangent plane of the off-axis secondary mirror L2 and a vertical plane).

TABLE 6

The technical indicators of this example 7 are shown in Table 7:

TABLE 7

Example 10

As shown in fig. 1, the present embodiment is different from embodiment 1 in that the reflecting surface of the off-axis secondary mirror L2 adopts a hyperboloid, which can further improve the correction capability of the off-axis secondary mirror L2 on the off-axis aberration of the system, and simultaneously balance the spherical aberration generated by the off-axis primary mirror L1; k is-1.024 to-3.5.

Examples 11 and 12 are different from example 10 in the reflection surface parameters and the values of k, and are otherwise the same.

The values of the reflecting surface parameters, k, for the off-axis primary mirror L1 and the off-axis secondary mirror L2 for examples 10-12 are shown in Table 8. In the table, R is the radius of curvature of the reflecting surface, and d is the distance between the vertex of the off-axis primary mirror L1 and the vertex of the off-axis secondary mirror L2 in the negative direction of the optical axis.

The specifications of this example 10 are shown in Table 9.

TABLE 8

TABLE 9

The inventor also adopts various surface combination modes of the off-axis primary mirror L1 and the off-axis secondary mirror L2, and the effect is not ideal.

When the surface type of the off-axis primary mirror L1 and the off-axis secondary mirror L2 adopts a combination mode of an ellipsoid and a hyperboloid, through optimization, the wave aberration can only reach 0.064 lambda (lambda is 632nm), and the relative distortion can only reach 0.08%.

When the surface type of the off-axis primary mirror L1 and the off-axis secondary mirror L2 adopts a hyperboloid and hyperboloid combination mode, through optimization, the wave aberration can only reach 0.058 lambda (lambda is 632nm), and the relative distortion can only reach 0.09%.

When the surface type of the off-axis primary mirror L1 and the off-axis secondary mirror L2 adopts a combination mode of an ellipsoid and an ellipsoid, through optimization, the wave aberration can only reach 0.085 lambda (lambda is 632nm), and the relative distortion can only reach 0.09%.

When the surface types of the off-axis primary mirror L1 and the off-axis secondary mirror L2 both adopt a high-order aspheric surface combination mode, through optimization, the wave aberration and the relative distortion of the system are equivalent to those of the mode that only the primary mirror adopts a high-order aspheric surface, but the off-axis secondary mirror adopts the high-order aspheric surface, so that the processing and detection difficulty is increased.