An athermalized infrared optical system

Abstract

The application provides an athermal infrared optical system, belonging to the technical field of airborne photoelectric detection, and specifically comprising a scanning mirror, an off-axis telescope assembly, a Delta prism and a converging assembly. The off-axis telescope assembly comprises a primary mirror, a secondary mirror and a tertiary mirror. The aperture center of the primary mirror and the center of the scanning mirror coincide. The light beam between the primary mirror and the scanning mirror is a first light beam. The secondary mirror and the tertiary mirror are located on the same side outside the range of the first light beam, and are located on the same side of the incident light beam of the scanning mirror. The scanning mirror reflects external light to the primary mirror, and the light is reflected by the primary mirror, the secondary mirror and the tertiary mirror in sequence. The Delta prism is located on the light path of the light reflected by the tertiary mirror, and is used for eliminating the image rotation caused by the scanning mirror searching for the azimuth scanning. The converging assembly is used for receiving the light emitted by the Delta prism and converging the light to the image plane of the detector. The optical system has the characteristics of no obstruction, athermalization, optical despinning and compactness, and realizes integrated design.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of airborne photoelectric detection, in particular to athermalized infrared optical system. BACKGROUND

[0002] The optical system is required to have the function of clear imaging at high and low temperatures due to large temperature change of the airborne platform environment; the system with a scanning mirror is required to have the function of image rotation elimination. Meanwhile, the space volume and load of the airborne platform are strictly limited, and the optical configuration is required to be as compact as possible to realize lightweight design.

[0003] The common athermalization is divided into electromechanical active type, mechanical passive type and optical passive type; the image rotation elimination mode is divided into mechanical type, electronic type and optical type, and the existing athermalized and image rotation eliminated infrared optical system has a large structure, which is difficult to meet the requirements of compact configuration and lightweight design. SUMMARY

[0004] Therefore, the present application provides an athermalized infrared optical system, which solves the problems in the prior art, has the characteristics of no obstruction, athermalization, optical image rotation elimination and compactness, and realizes integrated design.

[0005] The athermalized infrared optical system provided by the present application adopts the following technical scheme:

[0006] An athermalized infrared optical system comprises:

[0007] A scanning mirror is configured to scan a field of view.

[0008] An off-axis telescope assembly comprises a primary mirror, a secondary mirror and a tertiary mirror, the aperture center of the primary mirror is coincident with the center of the scanning mirror, the light beam between the primary mirror and the scanning mirror is a first light beam, the secondary mirror and the tertiary mirror are located on the same side outside the range of the first light beam, and the secondary mirror and the tertiary mirror are located on the same side of the incident light beam of the scanning mirror, the secondary mirror is arranged corresponding to the middle part of the first light beam, and the tertiary mirror is arranged corresponding to one end of the first light beam close to the primary mirror, the reflecting surface of the secondary mirror faces the reflecting surface of the primary mirror and the reflecting surface of the tertiary mirror, the aperture center point of the tertiary mirror and the aperture center point of the primary mirror are on a straight line, and the distance between the tertiary mirror and the first light beam is greater than the distance between the secondary mirror and the first light beam, the scanning mirror reflects external light to the primary mirror, and the light is reflected by the primary mirror, the secondary mirror and the tertiary mirror in sequence.

[0009] A Delta prism is located on the light path of the reflected light of the tertiary mirror, and the Delta prism is configured to receive the reflected light of the tertiary mirror, and eliminate the image rotation caused by the scanning mirror searching the azimuth.

[0010] A converging assembly is configured to receive the light emitted by the Delta prism and converge the light to the image plane of a detector.

[0011] Optionally, the Delta prism, the primary mirror, the secondary mirror and the tertiary mirror are all located on the same side of the incident light beam of the scanning mirror, and the distance from the Delta prism to the incident light beam of the scanning mirror is greater than the distance from the secondary mirror to the incident light beam of the scanning mirror, and the Delta prism is located on the side of the secondary mirror away from the first light beam.

[0012] Optionally, the converging assembly comprises a first mirror, an objective lens group, a second mirror and an ocular lens group, the first mirror is used to receive the light emitted by the Delta prism, the included angle between the light emitted by the first mirror and the light emitted by the Delta prism is 45 degrees, the objective lens group is used to receive the light emitted by the first mirror, the optical axis of the objective lens group is parallel to the light emitted by the first mirror, the second mirror receives the light emitted by the objective lens group, the included angle between the light emitted by the second mirror and the light emitted by the objective lens group is 45 degrees, and the ocular lens group is used to receive the light emitted by the second mirror, and the optical axis of the ocular lens group is located on the side of the light emitted by the tertiary mirror away from the first light beam.

[0013] Optionally, the Delta prism is located at the exit pupil position of the off-axis telescope assembly.

[0014] Optionally, the objective lens group comprises a first objective lens and a second objective lens, the first objective lens and the second objective lens successively converge the light emitted by the first mirror, the ocular lens group comprises a first ocular lens, a second ocular lens, a third ocular lens, a fourth ocular lens and a fifth ocular lens, the first ocular lens and the second ocular lens diffuse the light emitted by the second mirror, one side of the third ocular lens, the fourth ocular lens and the fifth ocular lens converges the light emitted by the second ocular lens, the first ocular lens and the fourth ocular lens are made of a material with a negative refractive index change with temperature, and the first objective lens, the second objective lens, the second ocular lens, the third ocular lens and the fifth ocular lens are made of a material with a positive refractive index change with temperature.

[0015] Optionally, the structural member of the off-axis telescope assembly is made of titanium alloy, and the optical member of the off-axis telescope assembly is made of K9 glass.

[0016] Optionally, the primary mirror, the secondary mirror and the tertiary mirror are all made of aspherical lens.

[0017] In summary, the present application has the following beneficial technical effects:

[0018] The optical system of the present application is a non-thermal long-wave infrared optical system applied in the field of airborne photoelectric detection. The system adopts an off-axis reflective telescope configuration to ensure that the aperture is not blocked; the Delta prism is used to eliminate the image rotation caused by the scanning process; and the material is matched to meet the non-thermal design of the system. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings described below only illustrate some of the embodiments of the present application, and the person skilled in the art can obtain other drawings according to these drawings without any creative effort.

[0020] Figure 1 A schematic diagram of three-dimensional ray tracing of an athermal infrared optical system;

[0021] Figure 2 A planar optical path diagram of an athermal infrared optical system.

[0022] Legend: 1, scanning mirror; 2, primary mirror; 3, secondary mirror; 4, tertiary mirror; 5, Delta prism; 6, first mirror; 7, first objective lens; 8, second objective lens; 9, second mirror; 10, first eyepiece lens; 11, second eyepiece lens; 12, third eyepiece lens; 13, fourth eyepiece lens; 14, fifth eyepiece lens; 15, detector. DETAILED DESCRIPTION

[0023] The embodiments of the present application will be described in detail below with reference to the drawings.

[0024] The embodiments of the present application will be described in detail below with reference to the drawings.

[0025] It is to be understood that the ranges and limits mentioned herein include all ranges located between the recited ranges, limits and endpoints. It must be noted that, as used in this specification and the appended claims, the singular form "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. It is further noted that the claims can be drafted to exclude any optional element. As such, any elements can be present or absent, and still fall within the scope of the claims. The terms "first", "second", "third", "fourth" and the like in the description and in the claims, if any, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the application described herein are, for example, capable of use in either order. Any discussion of mechanisms underlying the application should be treated as pure summary and should not be taken as an admission that the mechanisms are the only, or even the primary, mechanisms by which the described embodiments operate.

[0026] It is also necessary to note that the diagrams provided in the following embodiments only illustrate the basic concepts of the present application in a schematic manner, and only show the components related to the present application, not the number, shape and size of the components when actually implemented. The actual implementation of each component may be a random change in type, number and proportion, and the component layout may also be more complex.

[0027] In addition, in the following description, specific details are provided in order to facilitate a thorough understanding of examples. However, one skilled in the art will understand that the aspects described can be practiced without these specific details.

[0028] The embodiment of the present application provides an athermal infrared optical system.

[0029] As shown in Figure 1 and Figure 2 An athermal infrared optical system comprises:

[0030] A scanning mirror 1 is used to scan a field of view.

[0031] An off-axis telescope assembly comprises a primary mirror 2, a secondary mirror 3 and a tertiary mirror 4. The center of the aperture of the primary mirror 2 coincides with the center of the scanning mirror 1, more parts are coincided, and the space occupation is reduced. The light beam between the primary mirror 2 and the scanning mirror 1 is a first light beam. The secondary mirror 3 and the tertiary mirror 4 are located on the same side outside the range of the first light beam, and the secondary mirror 3 and the tertiary mirror 4 are located on the same side of the incident light beam of the scanning mirror 1. The secondary mirror 3 is arranged corresponding to the middle part of the first light beam. The tertiary mirror 4 is arranged corresponding to one end of the first light beam close to the primary mirror 2. The reflecting surface of the secondary mirror 3 faces the reflecting surface of the primary mirror 2 and the reflecting surface of the tertiary mirror 4. The center point of the aperture of the tertiary mirror 4 and the center point of the aperture of the primary mirror 2 are on a straight line. The distance between the tertiary mirror 4 and the first light beam is greater than the distance between the secondary mirror 3 and the first light beam. The scanning mirror 1 reflects external light to the primary mirror 2. The light is reflected by the primary mirror 2, the secondary mirror 3 and the tertiary mirror 4 in turn.

[0032] A Delta prism 5 is located on the light path of the reflected light of the tertiary mirror 4. The Delta prism 5 is used to receive the reflected light of the tertiary mirror 4. The Delta prism 5 is used to eliminate the image rotation caused by the scanning mirror 1 searching the azimuth scanning.

[0033] A converging assembly is used to receive the light emitted by the Delta prism 5 and converge the light to the image plane of a detector 15.

[0034] The parameters of the detector 15 of the present application are as follows: system: long-wave refrigeration type area array detector 15; image element size: 25 μm; detector 15 array: 640×512.

[0035] The optical system parameters of the application are: working waveband: 7700nm-10500nm; focal length: f=280mm; F number: 2; field angle: 3.27°x2.61°.

[0036] The optical system of the application is athermalized long-wave infrared optical system applied in the field of airborne photoelectric detection. The system adopts an off-axis reflective telescope configuration to ensure that the aperture is unobstructed; a Delta prism 5 is used to eliminate image rotation caused by scanning; and the system meets athermalized design by using material matching.

[0037] The Delta prism 5, the primary mirror 2, the secondary mirror 3, and the tertiary mirror 4 are all located on the same side of the incident light beam of the scanning mirror 1, and the distance from the Delta prism 5 to the incident light beam of the scanning mirror 1 is greater than the distance from the secondary mirror 3 to the incident light beam of the scanning mirror 1, and the Delta prism 5 is located on the side of the secondary mirror 3 away from the first light beam.

[0038] The converging assembly includes a first mirror 6, an objective lens group, a second mirror 9, and an eyepiece group, the first mirror 6 is used to receive the light emitted by the Delta prism 5, the included angle between the light emitted by the first mirror 6 and the light emitted by the Delta prism 5 is 45 degrees, the objective lens group is used to receive the light emitted by the first mirror 6, the optical axis of the objective lens group is parallel to the light emitted by the first mirror 6, the second mirror 9 receives the light emitted by the objective lens group, the included angle between the light emitted by the second mirror 9 and the light emitted by the objective lens group is 45 degrees, and the eyepiece group is used to receive the light emitted by the second mirror 9, the optical axis of the eyepiece group is located on the side of the light beam emitted by the tertiary mirror 4 away from the first light beam.

[0039] All the mirror groups in the embodiment of the application are sequentially distributed in one direction, and the optical axes of all the mirror groups and lenses are in the same plane, that is, the optical axes of the scanning mirror 1, the primary mirror 2, the secondary mirror 3, the tertiary mirror 4, the Delta prism 5, the first mirror 6, the objective lens group, the second mirror 9, and the eyepiece group are in the same plane, thereby reducing the volume of the entire device.

[0040] The Delta prism 5 is located at the exit pupil position of the off-axis telescope assembly, the size of the Delta prism 5 is compressed, and the material of the Delta prism 5 is selected to be zinc selenide, thereby improving the transmittance of the system.

[0041] The objective lens group comprises a first objective lens 7 and a second objective lens 8, which successively converge the outgoing light of the first reflecting mirror 6; the eyepiece group comprises a first eyepiece lens 10, a second eyepiece lens 11, a third eyepiece lens 12, a fourth eyepiece lens 13 and a fifth eyepiece lens 14, the first eyepiece lens 10 and the second eyepiece lens 11 diverge the outgoing light of the second reflecting mirror 9, and the third eyepiece lens 12, the fourth eyepiece lens 13 and the fifth eyepiece lens 14 converge the outgoing light of the second eyepiece lens 11 on one side; the first eyepiece lens 10 and the fourth eyepiece lens 13 are made of a material with a negative dn / dT, and the first objective lens 7, the second objective lens 8, the second eyepiece lens 11, the third eyepiece lens 12 and the fifth eyepiece lens 14 are made of a material with a positive dn / dT; the converging assembly of the application adopts an athermalization design; when the temperature changes, the focal length change of the lens with a positive dn / dT and the lens with a negative dn / dT cancels out each other, and a focusing mechanism is omitted.

[0042] The structural member of the off-axis telescope assembly is made of titanium alloy, and the optical member is made of K9 glass, so that a lightweight design is realized, the thermal expansion coefficients are matched, and a passive athermalization design is realized.

[0043] The primary mirror 2, the secondary mirror 3 and the tertiary mirror 4 all adopt aspheric lenses. The size envelope of the optical system is compressed.

[0044] For all the lenses of the application, the specific parameters are shown in Table 1.

[0045] Table 1

[0046]

[0047] The above is only a specific embodiment of the application, but the protection scope of the application is not limited to this, any person skilled in the art can easily think of changes or replacements within the technical range disclosed in the application, which should be covered in the protection scope of the application. Therefore, the protection scope of the application should be subject to the protection scope of the claims.

Claims

1. A thermalized infrared optical system, characterized in that, include: A scanning mirror (1) is used to scan the field of view; An off-axis telescope assembly includes a primary mirror (2), a secondary mirror (3), and a third mirror (4). The aperture center of the primary mirror (2) coincides with the center of the scanning mirror (1). The beam between the primary mirror (2) and the scanning mirror (1) is the first beam. The secondary mirror (3) and the third mirror (4) are located on the same side outside the range of the first beam, and the secondary mirror (3) and the third mirror (4) are located on the same side of the incident beam of the scanning mirror (1). The secondary mirror (3) is positioned at the center of the first beam. The third mirror (4)... The secondary mirror (3) is positioned at the end of the first beam that is close to the primary mirror (2). The reflective surface of the secondary mirror (3) faces the reflective surface of the primary mirror (2) and the reflective surface of the third mirror (4). The center point of the aperture of the third mirror (4) and the center point of the aperture of the primary mirror (2) are on a straight line. The distance between the third mirror (4) and the first beam is greater than the distance between the secondary mirror (3) and the first beam. The scanning mirror (1) reflects the external light to the primary mirror (2). The light passes through the primary mirror (2), the secondary mirror (3) and the third mirror (4) in sequence for reflection. Delta prism (5) is located in the optical path of the reflected light from the three mirrors (4). Delta prism (5) is used to receive the reflected light from the three mirrors (4). Delta prism (5) is used to eliminate the image rotation caused by the azimuth scanning of the scanning mirror (1). A converging component is used to receive the light emitted from the Delta prism (5) and converge the light onto the image plane of the detector (15); The Delta prism (5), primary mirror (2), secondary mirror (3) and third mirror (4) are all located on the same side of the incident beam of the scanning mirror (1), and the distance from the Delta prism (5) to the incident beam of the scanning mirror (1) is greater than the distance from the secondary mirror (3) to the incident beam of the scanning mirror (1). The Delta prism (5) is located on the side of the secondary mirror (3) away from the first beam. The converging assembly includes a first reflecting mirror (6), an objective lens group, a second reflecting mirror (9), and an eyepiece group. The first reflecting mirror (6) is used to receive the light emitted from the Delta prism (5). The angle between the light emitted from the first reflecting mirror (6) and the light emitted from the Delta prism (5) is 45 degrees. The objective lens group is used to receive the light emitted from the first reflecting mirror (6). The optical axis of the objective lens group is parallel to the light emitted from the first reflecting mirror (6). The second reflecting mirror (9) receives the light emitted from the objective lens group. The angle between the light emitted from the second reflecting mirror (9) and the light emitted from the objective lens group is 45 degrees. The eyepiece group is used to receive the light emitted from the second reflecting mirror (9). The optical axis of the eyepiece group is located on the side of the beam emitted from the three mirrors (4) that is away from the first beam. The Delta prism (5) is located at the exit pupil position of the off-axis telescope assembly; The objective lens group includes a first objective lens (7) and a second objective lens (8). The first objective lens (7) and the second objective lens (8) converge the light emitted from the first reflecting mirror (6) in sequence. The eyepiece group includes a first eyepiece lens (10), a second eyepiece lens (11), a third eyepiece lens (12), a fourth eyepiece lens (13), and a fifth eyepiece lens (14). The first eyepiece lens (10) and the second eyepiece lens (11) diffuse the light emitted from the second reflecting mirror (9). The third eyepiece lens (12), the fourth eyepiece lens (13), and the fifth eyepiece lens (14) converge the light emitted from the second eyepiece lens (11) on one side. The first eyepiece lens (10) and the fourth eyepiece lens (13) are made of materials whose refractive index changes negatively with temperature. The first objective lens (7), the second objective lens (8), the second eyepiece lens (11), the third eyepiece lens (12), and the fifth eyepiece lens (14) are made of materials whose refractive index changes positively with temperature.

2. The athermalized infrared optical system according to claim 1, characterized in that, The structural components of the off-axis telescope are made of titanium alloy, and the optical components are made of K9 glass.

3. The athermalized infrared optical system according to claim 1, characterized in that, The primary mirror (2), secondary mirror (3), and tertiary mirror (4) all use aspherical lenses.

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