CN112526747B - An aberration-corrected imaging lens assembly for two-dimensional motion of a conformal optical system - Google Patents

Abstract

The invention discloses an aberration correction imaging lens component of conformal optical system two-dimensional motion, comprising: the optical system comprises a conformal optical window, an aberration correction imaging lens assembly and a servo control system; the aberration correction imaging lens assembly is connected with the servo control system, and the servo control system can control the movement of the aberration correction imaging lens assembly; the aberration-correcting imaging lens assembly includes a first lens, a second lens, and a third lens; the servo control system can drive the first lens and the third lens to move along the optical axis relative to the second lens, and the servo control system can drive the first lens, the second lens and the third lens to rotate around the optical axis. The invention converts the inherent imaging lens component into a dynamic aberration correction element to realize the dynamic correction of the aberration of the conformal optical system.

Description

Aberration-corrected imaging lens assembly for two-dimensional motion of conformal optical system

technical field

The invention belongs to the technical field of weapon equipment photodetector design, and in particular relates to an aberration-correcting imaging lens assembly for two-dimensional motion of a conformal optical system.

Background technique

Conformal optics refers to the optimal design of the optical system, not only to achieve the best imaging quality of the optical system, but also to optimize the interaction of the optical system with its application environment. It is mainly used in high-speed aircraft and missiles In imaging detection systems for navigation, tracking or reconnaissance. In order to meet the larger field of view, the traditional airborne optical remote sensor often adopts a flat spliced optical window. Although this type of optical window has little impact on the imaging quality of the optical system, it will introduce greater resistance to the fuselage, and the flat window Will increase the reflective area of the radar cross section.

The outer surface of the window used by the conformal optical system needs to be smoothly matched with the outer surface of the cabin carrier, that is, "conformal" to the outer surface of the high-speed carrier, so that the window surface conforms to the hydrodynamic and aerodynamic properties of the carrier, but at this time The optical surface of the optical window that participates in imaging is generally an aspheric optical surface, or even an irregular free-form surface. At this time, when the optical system in the cabin performs large-scale scanning imaging on a certain range of field of view, the aero-optical window conformal to the high-speed carrier will introduce serious aberrations to the subsequent imaging optical system, and these aberrations will be The dynamic change due to the change of the scanning field of view greatly affects the imaging resolution of the remote sensing camera of the aircraft. Conformal optics theory researches scientific aberration correction methods for various severe dynamic aberrations introduced by aero-optical windows. By designing flexible and diverse aberration correctors, the imaging system can meet the aerodynamic performance requirements of the fuselage. The imaging performance of the system itself.

At present, the optical aberration correctors developed by scholars at home and abroad are mainly divided into two categories, namely static aberration correctors and dynamic aberration correctors, and both types of aberration correctors have inherent disadvantages. The static aberration corrector corrects imperfect aberrations, and the dynamic aberration corrector has a complex structure and a large volume, which increases the complexity of the system.

Contents of the invention

The technical problem solved by the present invention is: to overcome the deficiencies of the prior art, to provide an aberration-corrected imaging lens assembly with two-dimensional motion of a conformal optical system, to transform the inherent imaging lens assembly into a dynamic aberration-corrected element, and to realize conformal Optical system aberration dynamic correction.

The object of the present invention is achieved through the following technical solutions: an aberration-corrected imaging lens assembly with two-dimensional motion of a conformal optical system, including: a conformal optical window, an aberration-corrected imaging lens assembly, and a servo control system; wherein the image The aberration correction imaging lens assembly is connected to the servo control system, and the servo control system can control the movement of the aberration correction imaging lens assembly; the aberration correction imaging lens assembly includes a first lens, a second lens and a third lens; The servo control system can drive the first lens and the third lens to move along the optical axis relative to the second lens, and the servo control system can drive the first lens, the second lens and the third lens to rotate around the optical axis.

In the above-mentioned aberration-corrected imaging lens assembly with two-dimensional movement of the conformal optical system, the distance between the conformal optical window and the second lens is 136mm; the distance between the first lens and the second lens along the axis is 0mm-4mm, and The distance range of the movement of the three lenses relative to the second lens along the axis is 0mm-6.7mm; the angle range of the rotation of the first lens, the second lens and the third lens around the axis is 0-0.76°.

In the above-mentioned aberration-corrected imaging lens assembly for two-dimensional motion of the conformal optical system, the conformal optical window includes a conformal outer surface and a conformal inner surface; wherein the conformal outer surface and the conformal inner surface are off-axis concentric Paraboloid; the quadratic coefficients of both the conformal outer surface and the conformal inner surface are -0.875; the curvature radius of the conformal outer surface is 50mm, and the curvature radius of the conformal inner surface is 46mm.

In the aberration-corrected imaging lens assembly for two-dimensional movement of the above-mentioned conformal optical system, the conformal inner surface is a two-way adjustable symmetrical Zernike surface.

In the aberration-corrected imaging lens assembly for two-dimensional motion of the conformal optical system, the first lens includes a first spherical surface and a second spherical surface, the material of the first lens is germanium, and the thickness of the first lens is 3mm ; The second lens includes a plane and a first cylindrical surface, the material of the second lens is zinc selenide, and the thickness of the second lens is 2mm; the third lens includes a second cylindrical surface and a third spherical surface , the material of the third lens is germanium, and the thickness of the third lens is 3 mm.

In the aberration-corrected imaging lens assembly for two-dimensional motion of the above-mentioned conformal optical system, the vector height expression of the conformal inner surface is as follows:

是光线在标准则尼克表面上的交点轴向位置，ρ光线在光学表面上的归一化交点径向位置，

是光线与光学表面的夹角。Among them, the vector height of Z optical surface, the radial position of the intersection point of C rays on the optical surface, r is the radius value, k is the quadratic surface coefficient, A _i is the i-th coefficient of the standard Zernike polynomial,

is the axial position of the intersection point of the ray on the standard regular Nick surface, the radial position of the normalized intersection point of the ρ ray on the optical surface,

is the angle between the ray and the optical surface.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The present invention converts the inherent imaging lens assembly into a dynamic aberration correction element, realizing the dynamic correction of the aberration of the conformal optical system;

(2) The present invention is composed of three lenses, and the functions of the aberration correction imaging component include: first, as an aberration corrector, generating wavefront aberration, and correcting the wavefront aberration of the conformal optical system; Relay imaging system, receiving parallel light incident from conformal optical system, to complete conformal optical relay imaging;

(3) Two lenses in the lens assembly of the present invention move axially, and all three lenses in the lens assembly rotate around their axes. The axial movement of the two lenses compensates the defocusing amount that changes with the observation field in the system, and the rotation of the three lenses around the axis is used to compensate the astigmatism in the system that changes with the observation field.

Description of drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiment. The drawings are only for the purpose of illustrating a preferred embodiment and are not to be considered as limiting the invention. Also throughout the drawings, the same reference numerals are used to designate the same parts. In the attached picture:

FIG. 1 is a schematic structural diagram of an aberration-corrected imaging lens assembly for two-dimensional movement of a conformal optical system provided by an embodiment of the present invention;

FIG. 2 is a control flow diagram of the two-dimensional movement of the aberration-corrected imaging lens assembly provided by the embodiment of the present invention.

Detailed ways

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided for more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art. It should be noted that, in the case of no conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and examples.

FIG. 1 is a schematic structural diagram of an aberration-corrected imaging lens assembly for two-dimensional movement of a conformal optical system provided by an embodiment of the present invention. As shown in FIG. 1 , the aberration-corrected imaging lens assembly for two-dimensional movement of the conformal optical system includes: a conformal optical window 1 , an aberration-corrected imaging lens assembly 13 and a servo control system. Wherein, the aberration correction imaging lens assembly 13 is connected to the servo control system, and the servo control system can control the movement of the aberration correction imaging lens assembly 13; the aberration correction imaging lens assembly includes a first lens 2, The second lens 3 and the third lens 4; the servo control system can drive the first lens 2 and the third lens 4 to move along the axis relative to the second lens 3, and the servo control system can drive the first lens 2, the second lens The lens 3 and the third lens 4 move around the axis.

The distance between the conformal optical window 1 and the second lens 3 is 136 mm;

The servo control system can drive the first lens 2 and the third lens 4 to move along the axis relative to the second lens 3. The specific distance range of the movement of the first lens 2 relative to the second lens 3 is 0mm-4mm, and the third lens 4. The range of moving distance relative to the second lens 3 is 0mm-6.7mm.

The angle range of the movement of the first lens 2 , the second lens 3 and the third lens 4 around the axis is 0-0.76°.

The conformal optical system comprises a conformal optical window 1 comprising a conformal outer surface 5 and a conformal inner surface 6 . The conformal inner surface 6 is an aspheric surface, which is used to compensate high-order aspheric aberrations. The installation position of the two-dimensional motion aberration corrector 13 can accept the imaging light entering the conformal optical window 1, and its dynamic motion can compensate for low-order aberrations, mainly including defocus and astigmatism in the large-angle observation field. The so-called observation field refers to the rotation or pointing range of the sensor with a sufficiently large angle in the pitch and azimuth directions, which is compared with the instantaneous field of view. The instantaneous field of view of a general sensor is much smaller than the observation field.

As shown in Figure 1, the conformal optical window 1 generally has two functions: first, to ensure the hydrodynamic performance of the high-speed aircraft; second, to ensure that the imaging optical system behind the window can satisfy sufficient observation field imaging. For sufficient fluid performance, the surface shape of the conformal optical window generally satisfies a smooth transition with the installation interface of the high-speed aircraft. However, the optical window that meets this condition generally introduces aberrations that vary with the observation field. The aberrations include high-order aberrations and low-order aberrations. Static correction methods and dynamic correction methods are used respectively. The high-order aberrations are generally corrected by the static aberration corrector, that is, the inner surface of the conformal optical system. Low-order aberrations, especially astigmatism and defocus, are generally corrected by a dynamic phase aberration corrector, that is, an aberration generator of a conformal optical system.

The entrance pupil diameter of the optical system is 50mm, the observation field ranges from -30° to 30° in elevation, and the working center wavelength is 4.2μm. The above is a design example, and this method is applicable to the same type of conformal optical system.

The two surfaces of the conformal optical window 1 are off-axis concentric paraboloids, and the quadratic coefficients of the inner and outer surfaces are both -0.875. The shape of the inner surface is different from that of the outer surface. The inner surface is a symmetrical Zernike surface, and the outer surface The radius of curvature is 50mm, the radius of curvature of the inner surface is 46mm, and the vector height expression of the inner surface is as follows:

是光线在标准则尼克表面上的交点轴向位置，ρ光线在光学表面上的归一化交点径向位置，

是光线与光学表面的夹角。Among them, the vector height of Z optical surface, the radial position of the intersection point of C rays on the optical surface, r is the radius value, k is the quadratic surface coefficient, A _i is the i-th coefficient of the standard Zernike polynomial,

is the axial position of the intersection point of the ray on the standard regular Nick surface, the radial position of the normalized intersection point of the ρ ray on the optical surface,

is the angle between the ray and the optical surface.

The aberration corrector 13 of two-dimensional movement comprises lens 2, lens 3, lens 4, and the two-dimensional movement of aberration corrector comprises: (1) the axial motion of lens 2 and lens 4; (2) lens 2, lens 3. The rotation of the lens 4 around the axis, the movement of the lens 2 relative to the lens 3 compensates the defocus in the system, and the movement of the lens 4 relative to the lens 3 compensates the astigmatism in the system; Rotation around an axis changes the direction of the astigmatism.

The lens 2 includes a spherical surface 7 and a spherical surface 8, the material is germanium, and the thickness is 3 mm; the lens 3 includes a plane 9 and a cylindrical surface (or annular surface) 10, the material is zinc selenide, and the thickness is 2 mm; the lens 4 includes a The cylindrical surface 11 (or annular surface) and a spherical surface 12 are made of germanium and have a thickness of about 3 mm. The function of lens 2 moving along the axis relative to 3 in the figure is to compensate the defocus of the optical system, and the function of lens 4 moving along the axis relative to 3 in the figure is to compensate the astigmatism of the optical system.

The initial wavefront difference introduced by the conformal optical window reaches about 5 wavelengths of RMS value in the observation field, which is an intolerable aberration for optical imaging performance and must be corrected. The wavefront aberration is decomposed into the form of orthogonal Zernike polynomial aberration. Through the decomposition, it is known that the aberration type includes high-order aberrations, so the inner surface of the fairing is set as the Zernike polynomial surface to correct the high-order aberrations in the aberration. Second item, after the internal surface aberration is corrected, the wavefront difference of the aberration in the observation field is about 0.3 to 0.5 wavelengths of RMS value.

The remaining aberrations are mainly composed of low-order aberrations, such as defocus and astigmatism, and the inner surface of the window cannot usually be corrected. At this time, when the two-dimensional motion aberration corrector is corrected, the aberrations are corrected to the remaining 0.025 wavelength RMS value. When two-dimensional motion is generated, the spacing and rotation between the three lenses will precisely remove defocus and astigmatism in aberrations. The two-dimensional movement of the three lenses needs to provide sufficient speed to match the scanning speed of the imaging optical system in the observation field, and the servo control system precisely controls the action of the two-dimensional motion aberration corrector through the control database.

Fig. 2 has provided the control process of the aberration correction imaging lens assembly 13 of two-dimensional movement, and the 14th step determines the position of the aberration correction imaging lens assembly 13; The 15th step shows that the detector provides the aberration data; Whether the previous RMS value meets the system requirements determines whether the aberration correction imaging lens assembly 13 needs to be moved. If movement is required, the servo control system performs motion control on the aberration correction imaging lens assembly 13 by calling the position prestored database data. The specific action change of the time change mainly depends on the position and surface shape of the light entering the conformal optical window. The application of the aberration correction imaging lens assembly 13 in different conformal optical systems is universal. The aberration correction imaging lens assembly 13 The action of the conformal optical window depends on the material, thickness, outer surface, and inner surface shape of the conformal optical window. The aberration-correcting imaging lens assembly 13 is generally placed at an afocal position behind the conformal optical window.

The 16th step judges whether two lenses should be separated and produce axial movement, if it is judged that axial movement should be produced between the lenses through the prestored database, then the 17th step controls the aberration correction imaging lens assembly 13 to produce axial movement between the lenses sports. The 18th step judges whether the aberration correction imaging lens assembly 13 should rotate around the axis, if it is judged through the pre-stored database that the aberration correction imaging lens assembly 13 must produce the rotation around the axis, then the 19th step controls the aberration correction imaging lens assembly 13 Generate rotation around the axis. If it is judged that it is not needed, then jump directly to the 20th step of the process and end.

The present invention transforms the inherent imaging lens assembly into a dynamic aberration correction element to realize the dynamic correction of the aberration of the conformal optical system; the present invention is composed of three lenses, and the functions of the aberration correction imaging assembly include: first, as an aberration corrector , generate wavefront aberration, and correct the wavefront aberration of the conformal optical system, and secondly, as a relay imaging system, receive the incident parallel light of the conformal optical system to complete the conformal optical relay imaging; the two components in the lens assembly of the present invention The lenses undergo axial movement and all three lenses in the lens assembly pivot. The axial movement of the two lenses compensates the defocusing amount that changes with the observation field in the system, and the rotation of the three lenses around the axis is used to compensate the astigmatism in the system that changes with the observation field.

Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention, and any person skilled in the art can use the methods disclosed above and technical content to analyze the present invention without departing from the spirit and scope of the present invention. Possible changes and modifications are made in the technical solution. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention, which do not depart from the content of the technical solution of the present invention, all belong to the technical solution of the present invention. protected range.

Claims (1)

1. An aberration-corrected imaging lens assembly for two-dimensional motion of a conformal optical system, characterized in that it comprises: a conformal optical window (1), an aberration-corrected imaging lens assembly (13) and a servo control system; wherein, The aberration correction imaging lens assembly (13) is connected to the servo control system, and the servo control system can control the movement of the aberration correction imaging lens assembly (13); The aberration correcting imaging lens assembly includes a first lens (2), a second lens (3) and a third lens (4); The servo control system can drive the first lens (2) and the third lens (4) to move along the optical axis relative to the second lens (3), and the servo control system can drive the first lens (2), the second lens (3) and the third lens (4) rotate around the optical axis; wherein, The conformal optical window (1) comprises a conformal outer surface (5) and a conformal inner surface (6); wherein, the conformal outer surface (5) and the conformal inner surface (6) are off-axis concentric paraboloids; The quadric coefficients of the conformal outer surface (5) and the conformal inner surface (6) are both -0.875; The radius of curvature of the conformal outer surface (5) is 50 mm, and the radius of curvature of the conformal inner surface (6) is 46 mm; The vector height expression of the conformal inner surface (6) is as follows:

Among them, the vector height of Z optical surface, the radial position of the intersection point of C rays on the optical surface, r is the radius value, k is the quadratic surface coefficient, A _i is the i-th coefficient of the standard Zernike polynomial,

is the axial position of the intersection point of the ray on the standard regular Nick surface, the radial position of the normalized intersection point of the ρ ray on the optical surface,

is the angle between the ray and the optical surface; The distance between the conformal optical window (1) and the second lens (3) is 136mm; The distance range of the axial movement of the first lens (2) relative to the second lens (3) is 0 mm-4 mm, and the distance range of the axial movement of the third lens (4) relative to the second lens (3) is 0 mm-6.7 mm. ; The angle range of the first lens (2), the second lens (3) and the third lens (4) rotating around the axis is 0-0.76°; the conformal inner surface (6) is a two-way adjustable symmetrical Zernike surface ; The first lens (2) includes a first spherical surface (7) and a second spherical surface (8), the material of the first lens (2) is germanium, and the thickness of the first lens (2) is 3mm; The second lens (3) includes a plane (9) and a first cylinder (10), the material of the second lens (3) is zinc selenide, and the thickness of the second lens (3) is 2mm; The third lens (4) includes a second cylindrical surface (11) and a third spherical surface (12), the material of the third lens (4) is germanium, and the thickness of the third lens (4) is 3 mm; in, The method for controlling the two-dimensional movement of the aberration-corrected imaging lens assembly includes: Determine the position of the aberration correction imaging lens assembly (13); The detector provides aberration data; Judging whether the first lens (2) and the third lens (4) produce axial movement, if it is judged through the pre-stored database that there should be an axial movement between the first lens (2) and the third lens (4). movement, then control the two lenses of the first lens (2) and the third lens (4) to produce axial movement; Judging whether the aberration correction imaging lens assembly (13) produces a rotation around the axis, if it is judged through the pre-stored database that the aberration correction imaging lens assembly (13) produces a rotation around the axis, then controlling the aberration correction imaging lens assembly (13) to produce a rotation around the axis turn.

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