Athermal infrared optical system

Abstract

The invention provides an athermalization infrared optical system, belongs to the technical field of airborne photoelectric detection, and particularly relates to a scanning reflector. The off-axis telescopic assembly comprises a primary mirror, a secondary mirror and a third mirror, the caliber center of the primary mirror coincides with the center of the scanning reflector, a light beam between the primary mirror and the scanning reflector is a first light beam, the secondary mirror and the third mirror are located on the same side outside the range of the first light beam, and the secondary mirror and the third mirror are located on the same side of an incident light beam of the scanning reflector; the scanning reflector reflects external light to the primary mirror, and the light is reflected by the primary mirror, the secondary mirror and the third mirror in sequence; the Delta prism is located on a light path of reflected light of the third mirror, and the Delta prism is used for eliminating image rotation caused by searching azimuth scanning of the scanning reflector; and the convergence assembly is used for receiving emergent light of the Delta prism and converging the light to the image surface of the detector. The optical system has the advantages of being free of blocking, athermalization, optical racemization and compactness, and integrated design is achieved.

Description

Technical Field

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

[0002] The ambient temperature of the airborne platform varies greatly, requiring the optical system to have the ability to image clearly at both high and low temperatures; the system with a scanning mirror needs to have the function of derotation. At the same time, the airborne platform has strict restrictions on space volume and load, requiring the optical configuration to be as compact as possible to achieve lightweight design.

[0003] Commonly used athermalization methods are divided into electromechanical active, mechanical passive and optical passive methods; the racemization methods are divided into mechanical, electronic and optical methods. The existing athermalization racemization infrared optical system has a large structure and it is difficult to meet the requirements of making the configuration as compact as possible and achieving lightweight design. Summary of the invention

[0004] In view of this, the present application provides an athermal infrared optical system, which solves the problems in the prior art and has the characteristics of being unobstructed, athermal, optically racemized, and compact, thus achieving an integrated design.

[0005] The present application provides an athermal infrared optical system using the following technical solutions:

[0006] An athermalized infrared optical system, comprising:

[0007] A scanning reflector, used for scanning the field of view;

[0008] An off-axis telescope assembly comprises a primary mirror, a secondary mirror and a third mirror, wherein the aperture center of the primary mirror coincides with the center of a scanning reflector, the light beam between the primary mirror and the scanning reflector is a first light beam, the secondary mirror and the third mirror are located on the same side outside the range of the first light beam, and the secondary mirror and the third mirror are located on the same side of the incident light beam of the scanning reflector, the secondary mirror is arranged corresponding to the middle of the first light beam, the third mirror is arranged corresponding to an 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 third mirror, the aperture center point of the third mirror and the aperture center point of the primary mirror are on a straight line, and the distance between the third mirror and the first light beam is greater than the distance between the secondary mirror and the first light beam, the scanning reflector reflects external light to the primary mirror, and the light is reflected by the primary mirror, the secondary mirror and the third mirror in sequence;

[0009] A Delta prism is located on the optical path of the light reflected by the three mirrors. The Delta prism is used to receive the reflected light from the three mirrors. The Delta prism is used to eliminate the image rotation caused by the scanning mirror searching the azimuth scan;

[0010] The converging component is used to receive the light emitted by the Delta prism and converge the light onto the detector image plane.

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

[0012] Optionally, the converging assembly includes a first reflector, an objective lens group, a second reflector and an eyepiece group, the first reflector is used to receive the output light of the Delta prism, the angle between the output light of the first reflector and the output light of the Delta prism is 45 degrees, the objective lens group is used to receive the output light of the first reflector, the optical axis of the objective lens group is parallel to the output light of the first reflector, the second reflector receives the output light of the objective lens group, the angle between the output light of the second reflector and the output light of the objective lens group is 45 degrees, the eyepiece group is used to receive the output light of the second reflector, and the optical axis of the eyepiece group is located on the side of the three-mirror output light beam facing away from the first light beam.

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

[0014] Optionally, the objective lens group includes a first objective lens and a second objective lens, and the first objective lens and the second objective lens converge the output light of the first reflector in turn; the eyepiece group includes a first eyepiece lens, a second eyepiece lens, a third eyepiece lens, a fourth eyepiece lens and a fifth eyepiece lens, and the first eyepiece lens and the second eyepiece lens diffuse the output light of the second reflector, and the third eyepiece lens, the fourth eyepiece lens and the fifth eyepiece lens converge the output light of the second eyepiece lens on one side; the first eyepiece lens and the fourth eyepiece lens are made of a material whose refractive index changes negatively with temperature, and the first objective lens, the second objective lens, the second eyepiece lens, the third eyepiece lens and the fifth eyepiece lens are made of a material whose refractive index changes positively with temperature.

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

[0016] Optionally, the primary mirror, secondary mirror and tertiary mirror all use aspherical lenses.

[0017] In summary, this application includes the following beneficial technical effects:

[0018] The optical system of the present application is an athermal long-wave infrared optical system used 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 is used to eliminate image rotation caused by the scanning process; and the system meets the athermal design by using material matching. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 A schematic diagram of three-dimensional light tracing in an athermalized infrared optical system;

[0021] Figure 2 This is a planar optical path diagram of the athermalized infrared optical system.

[0022] Explanation of the accompanying drawings: 1. scanning reflector; 2. primary mirror; 3. secondary mirror; 4. third mirror; 5. Delta prism; 6. first reflector; 7. first objective lens; 8. second objective lens; 9. second reflector; 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 are described in detail below with reference to the accompanying drawings.

[0024] The following describes the implementation methods of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific implementation methods, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the following embodiments and the features in the embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present application.

[0025] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on the present application, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this device and / or practice this method.

[0026] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present application. The illustrations only show the components related to the present application rather than being drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed at will, and the component layout may also be more complicated.

[0027] Additionally, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, it will be understood by those skilled in the art that the aspects described may be practiced without these specific details.

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

[0029] like Figure 1 and Figure 2 As shown, an athermalized infrared optical system comprises:

[0030] The scanning reflector 1 is used for scanning the field of view.

[0031] An off-axis telescope assembly comprises 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 a scanning reflector 1, so that more parts overlap to reduce space occupancy. The light beam between the primary mirror 2 and the scanning reflector 1 is a first light beam. The secondary mirror 3 and the third mirror 4 are located on the same side outside the range of the first light beam, and the secondary mirror 3 and the third mirror 4 are located on the same side of the incident light beam of the scanning reflector 1. The secondary mirror 3 is arranged corresponding to the middle part of the first light beam, and the third mirror 4 is arranged corresponding to an 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 third mirror 4. The aperture center point of the third mirror 4 and the aperture center point of the primary mirror 2 are on a straight line, and the distance between the third mirror 4 and the first light beam is greater than the distance between the secondary mirror 3 and the first light beam. The scanning reflector 1 reflects external light to the primary mirror 2, and the light is reflected by the primary mirror 2, the secondary mirror 3 and the third mirror 4 in sequence.

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

[0033] The converging component is used to receive the light emitted by the Delta prism 5 and converge the light onto the image plane of the detector 15.

[0034] The parameters of the detector 15 of the present application are: system: long-wave cooling type array detector 15; pixel size: 25 μm; detector 15 array: 640×512.

[0035] The optical system parameters of the present application are: working band: 7700nm~10500nm; focal length: f=280mm; F ​​number: 2; field of view: 3.27°×2.61°.

[0036] The optical system of the present application is an athermal long-wave infrared optical system used 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 the scanning process; and the system meets the athermal design by using material matching.

[0037] The Delta prism 5, the primary mirror 2, the secondary mirror 3 and the third mirror 4 are all located on the same side of the incident light beam of the scanning reflector 1, and the distance from the Delta prism 5 to the incident light beam of the scanning reflector 1 is greater than the distance from the secondary mirror 3 to the incident light beam of the scanning reflector 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 reflector 6, an objective lens group, a second reflector 9 and an eyepiece group. The first reflector 6 is used to receive the light emitted from the Delta prism 5, and the angle between the light emitted from the first reflector 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 reflector 6, and the optical axis of the objective lens group is parallel to the light emitted from the first reflector 6. The second reflector 9 receives the light emitted from the objective lens group, and the angle between the light emitted from the second reflector 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 reflector 9, and the optical axis of the eyepiece group is located on the side of the light beam emitted from the three-mirror 4 that is opposite to the first light beam.

[0039] In the embodiment of the present application, all the mirror groups are distributed in sequence along 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 reflector 1, the primary mirror 2, the secondary mirror 3, the third mirror 4, the Delta prism 5, the first reflector 6, the objective lens group, the second reflector 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, compressing the size of the Delta prism 5. The material of the Delta prism 5 is zinc selenide, which improves the system transmittance.

[0041] The objective lens group includes a first objective lens 7 and a second objective lens 8, and the first objective lens 7 and the second objective lens 8 converge the output light of the first reflector 6 in sequence. The eyepiece group includes a first eyepiece 10, a second eyepiece 11, a third eyepiece 12, a fourth eyepiece 13 and a fifth eyepiece 14, and the first eyepiece 10 and the second eyepiece 11 diffuse the output light of the second reflector 9, and the third eyepiece 12, the fourth eyepiece 13 and the fifth eyepiece 14 converge the output light of the second eyepiece 11 on one side. The first eyepiece lens 10 and the fourth eyepiece lens 13 are made of a material whose refractive index change dn / dT with temperature is negative, 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 whose refractive index change dn / dT with temperature is positive. The converging component of the present application adopts an athermal design. When the temperature changes, the focal length changes of the lens whose refractive index changes positively with temperature and the lens whose refractive index changes negatively with temperature cancel each other out, thereby eliminating the focusing mechanism.

[0042] The structural parts of the off-axis telescope assembly are made of titanium alloy, and the optical parts of the off-axis telescope assembly are made of K9 glass, so as to achieve lightweight design, match thermal expansion coefficients, and realize passive athermal design.

[0043] The primary mirror 2, the secondary mirror 3 and the tertiary mirror 4 are all aspherical lenses, which compresses the size envelope of the optical system.

[0044] The details of all lenses in this application are shown in Table 1.

[0045] Table 1

[0046]

[0047] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. An athermalized infrared optical system, characterized in that: include: A scanning reflector (1) for scanning the field of view; An off-axis telescope assembly comprises a primary mirror (2), a secondary mirror (3) and a third mirror (4), wherein the aperture center of the primary mirror (2) coincides with the center of a scanning reflector (1), the light beam between the primary mirror (2) and the scanning reflector (1) is a first light beam, the secondary mirror (3) and the third mirror (4) are located on the same side outside the range of the first light beam, and the secondary mirror (3) and the third mirror (4) are located on the same side of the incident light beam of the scanning reflector (1), the secondary mirror (3) is arranged corresponding to the middle of the first light beam, and the third mirror (4) is arranged corresponding to the middle of the first light beam. The first light beam is arranged at one end 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 third mirror (4), the aperture center point of the third mirror (4) and the aperture center point of the primary mirror (2) are on a straight line, and the distance between the third mirror (4) and the first light beam is greater than the distance between the secondary mirror (3) and the first light beam, the scanning reflector (1) reflects external light to the primary mirror (2), and the light is reflected by the primary mirror (2), the secondary mirror (3) and the third mirror (4) in sequence; A Delta prism (5) is located on the optical path of the light reflected by the three mirrors (4), the Delta prism (5) is used to receive the light reflected by the three mirrors (4), and the Delta prism (5) is used to eliminate the image rotation caused by the search azimuth scanning of the scanning reflector (1); The converging component is used to receive the light emitted by the Delta prism (5) and converge the light onto the image plane of the detector (15).

2. The athermalized infrared optical system according to claim 1, characterized in that: The Delta prism (5), the primary mirror (2), the secondary mirror (3) and the third mirror (4) are all located on the same side of the incident light beam of the scanning reflector (1), and the distance from the Delta prism (5) to the incident light beam of the scanning reflector (1) is greater than the distance from the secondary mirror (3) to the incident light beam of the scanning reflector (1), and the Delta prism (5) is located on the side of the secondary mirror (3) away from the first light beam.

3. The athermalized infrared optical system according to claim 2, characterized in that: The converging assembly comprises a first reflecting mirror (6), an objective lens group, a second reflecting mirror (9) and an eyepiece group, wherein the first reflecting mirror (6) is used to receive light emitted from a delta prism (5), and 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 light emitted from the first reflecting mirror (6), and 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 light emitted from the objective lens group, and 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 light emitted from the second reflecting mirror (9), and the optical axis of the eyepiece group is located on a side of the light beam emitted from the three mirrors (4) that is opposite to the first light beam.

4. The athermalized infrared optical system according to claim 3, characterized in that: The Delta prism (5) is located at the exit pupil position of the off-axis telescope assembly.

5. The athermalized infrared optical system according to claim 3, characterized in that: The objective lens group comprises a first objective lens (7) and a second objective lens (8), wherein the first objective lens (7) and the second objective lens (8) sequentially converge the light emitted from the first reflector (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), wherein the first eyepiece lens (10) and the second eyepiece lens (11) diffuse the light emitted from the second reflector (9), and one side of the third eyepiece lens (12), the fourth eyepiece lens (13) and the fifth eyepiece lens (14) converges the light emitted from the second eyepiece lens (11); the first eyepiece lens (10) and the fourth eyepiece lens (13) are made of a material whose refractive index changes negatively with temperature, 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 whose refractive index changes positively with temperature.

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

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

Images