Aperture off-axis total reflection type infrared optical system

Abstract

The utility model relates to the technical field of optical detection, and particularly discloses an aperture off-axis total reflection type infrared optical system, which comprises an optical element and a lens cone, and the optical element comprises a primary lens, a secondary lens, a third lens and a detector. Incident light from a target is reflected by the primary mirror and then forms a primary image plane between the primary mirror and the secondary mirror, and then the incident light is reflected by the secondary mirror and the third mirror in sequence and reaches the focal plane of the detector without blocking to form a target image. The entrance pupil is arranged in front of the primary mirror; the primary mirror and the secondary mirror are eccentrically arranged in the Y-axis direction and are obliquely arranged around the X-axis. And the third mirror is eccentrically arranged in the Y-axis direction. The utility model has the advantages of compact structure, high efficiency, easy heat elimination, and good imaging quality.

Description

Technical Field

[0001] The utility model relates to the technical field of optical detection, and more specifically to an aperture off-axis total reflection type infrared optical system. Background Art

[0002] Most traditional infrared imaging optical systems adopt transmission or catadioptric forms, but there are few lens materials that can be used in the medium-wave or long-wave infrared spectrum, and the materials that can be used in both bands (medium-wave and long-wave) are even more limited; the transmission system will inevitably introduce chromatic aberration in the design, and it is not easy to achieve passive heat removal design;

[0003] There is an urgent need for an infrared optical system that can be used in two bands at the same time and has good imaging effect and heat dissipation design to meet the needs of use. Utility Model Content

[0004] The technical problem to be solved by the utility model is to provide an aperture off-axis total reflection infrared optical system with compact structure, high efficiency, easy heat removal and good imaging quality;

[0005] The solution adopted by the utility model to solve the technical problem is:

[0006] An aperture off-axis total reflection infrared optical system comprises optical components and a lens barrel; the optical components comprise a primary mirror, a secondary mirror, a third mirror, an aperture stop, and a detector;

[0007] The incident light from the target is reflected by the primary mirror and forms a primary image plane between the primary mirror and the secondary mirror, and then reflects through the secondary mirror and the third mirror in sequence, reaching the focal plane of the detector without obstruction to form a target image;

[0008] The entrance pupil is set in front of the primary mirror;

[0009] The primary mirror and the secondary mirror are both eccentrically arranged in the Y-axis direction and tilted around the X-axis;

[0010] The three mirrors are eccentrically arranged in the Y-axis direction.

[0011] In some possible implementations,

[0012] The optical element is made of the same material as the lens barrel.

[0013] In some possible implementations,

[0014] The optical element and the lens barrel are made of aluminum alloy material or silicon carbide material.

[0015] In some possible implementations,

[0016] The primary mirror is an even-order high-order aspheric surface, with an eccentricity of no more than 20 mm in the Y-axis direction and a tilt of no more than 6° around the X-axis.

[0017] In some possible implementations,

[0018] The secondary mirror is a quadratic curved surface, with an eccentricity of no more than 20 mm in the Y-axis direction and an inclination of no more than 6° around the X-axis.

[0019] In some possible implementations,

[0020] The three mirrors are even-order high-order aspherical surfaces, and the eccentricity in the Y-axis direction is no more than 10 mm.

[0021] In some possible implementations,

[0022] The focal power of the primary mirror is positive, the focal power of the secondary mirror is negative, and the focal power of the third mirror is positive.

[0023] In some possible implementations,

[0024] The optical components meet the following requirements: field of view is 6.44°×5.16° and focal length is 136 mm.

[0025] In some possible implementations,

[0026] The detector comprises a cold stop arranged at the aperture stop and a focal plane; the cold stop is arranged between the focal plane and the three mirrors; and the detector is a medium-wave refrigerated detector.

[0027] In some possible implementations,

[0028] The incident optical axis of the incident light ray is parallel to the outgoing optical axis of the outgoing light ray.

[0029] Compared with the prior art, the utility model has the following beneficial effects:

[0030] Compared with the traditional transmission infrared optical system, the utility model has the characteristics of less number of lenses, high efficiency, no color difference, and acceptable installation and adjustment complexity;

[0031] In the utility model, the optical component and the lens barrel are made of the same material, which ensures that the optical component and the lens barrel can expand and contract evenly, which is conducive to realizing the athermal design of the system and eliminating the influence of temperature changes on the entire optical system;

[0032] The utility model can effectively correct spherical aberration, coma and astigmatism through eccentric and tilt design, and has the advantages of no aperture obstruction at the center and a large field of view. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the structure of the utility model;

[0034] Figure 2 is the modulation transfer function curve of the utility model at -55°C;

[0035] Figure 3 is the modulation transfer function curve of the utility model at 20°C;

[0036] Figure 4 is the modulation transfer function curve of the utility model at +70°C;

[0037] Among them: 1. Primary mirror; 2. Secondary mirror; 3. Tertiary mirror; 4. Aperture stop; 5. Focal plane. DETAILED DESCRIPTION

[0038] In the present utility model, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral body; it can be directly connected, or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. The "first", "second" and similar words mentioned in this application do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, "one" or "one" and other similar words do not indicate a quantity limit, but indicate the existence of at least one. In the implementation of this application, "and / or" describes the association relationship of the associated objects, indicating that there can be three relationships, for example, A and / or B can indicate: A exists alone, A and B exist at the same time, and B exists alone. In the description of the embodiments of the present application, unless otherwise specified, the meaning of "multiple" refers to two or more. For example, multiple positioning columns refer to two or more positioning columns. For ordinary technicians in this field, the specific meanings of the above terms in the utility model can be understood according to the specific circumstances.

[0039] The utility model is described in detail below.

[0040] like Figure 1-Figure 4 As shown:

[0041] An aperture off-axis total reflection infrared optical system, suitable for medium waves with a wavelength band of 3-5um; comprising optical components and a lens barrel; the optical components include a primary mirror 1, a secondary mirror 2, a third mirror 3, an aperture stop 4, and a detector;

[0042] like Figure 1 As shown, first, the incident light from the target is reflected by the primary mirror 1 and forms a primary image plane between the primary mirror 1 and the secondary mirror 2. The image plane is close to the exit pupil to avoid secondary occlusion.

[0043] Then, it is reflected by the secondary mirror 2 and the tertiary mirror 3 in sequence, and reaches the focal plane 5 of the detector without obstruction to form a target image;

[0044] Specifically, in the optical system, the entrance pupil is arranged in front of the primary mirror 1, and the exit pupil is arranged at the aperture stop 4;

[0045] The primary mirror 1 and the secondary mirror 2 are both eccentrically arranged in the Y-axis direction and tilted around the X-axis; the tertiary mirror 3 is eccentrically arranged in the Y-axis direction;

[0046] The detector includes a cold stop arranged at the aperture stop 4, and a focal plane 5; the cold stop is arranged between the focal plane 5 and the three mirrors 3; the detector is a medium-wave refrigeration detector; in the optical component, the cold stop is arranged at the aperture stop 4, thereby effectively achieving 100% cold stop matching; the exit pupil is arranged at the cold stop;

[0047] Specifically, the input conditions of the optical system are an entrance pupil diameter of 34 mm, an F number of 4, a 640*512 cooled medium wave detector, and a pixel size of 24 um;

[0048] The aperture stop 4 is set at the cold stop, and the focal plane size of the detector is matched by constraining the image height of the chief ray of each field of view, and the cold stop and F number of the detector are matched by constraining the exit pupil position and exit pupil diameter;

[0049] Furthermore, the primary mirror 1 is an even-order high-order aspheric surface; the secondary mirror 2 is a quadratic surface; and the tertiary mirror 3 is an even-order high-order aspheric surface;

[0050] In some possible implementations, in order to enable the system to have a good heat elimination effect, thereby eliminating the influence of temperature changes on the entire optical system;

[0051] The optical element and the lens barrel are made of the same material, so that the optical element and the lens barrel can expand and contract evenly, which is conducive to realizing the athermal design of the system;

[0052] Specifically, the optical component and the lens barrel are made of aluminum alloy material or silicon carbide material.

[0053] In some possible implementations, in order to effectively ensure imaging quality, eliminate aberrations, and make the optical fiber unobstructed;

[0054] The primary mirror 1 is not more than 20 mm eccentric in the Y-axis direction and is not more than 6° tilted around the X-axis;

[0055] The secondary mirror 2 is eccentric in the Y-axis direction by no more than 20 mm and tilted about the X-axis by no more than 6°;

[0056] The eccentricity of the three mirrors 3 in the Y-axis direction is no more than 10 mm.

[0057] Among them, the eccentricity of the primary mirror 1, the secondary mirror 2, and the tertiary mirror 3 in the Y-axis direction can also effectively realize the aperture offset, thereby realizing the aperture off-axis;

[0058] In some possible implementations, the focal power of the primary mirror 1 is positive, the focal power of the secondary mirror 2 is negative, and the focal power of the tertiary mirror 3 is positive. In some possible implementations, the optical components satisfy: a field of view of 6.44°×5.16°, and a focal length of 136 mm.

[0059] In some possible implementations, the incident optical axis of the incident light is parallel to the exiting optical axis of the exiting light.

[0060] Table 1 shows the structural parameters of the optical components in this optical system;

[0061]

[0062] like Figure 2-Figure 4 As shown, it is the modulation transfer function curve of the optical system, where: Figure 2 is the modulation transfer function curve of the utility model at -55°C;

[0063] Figure 3 is the modulation transfer function curve of the utility model at 20°C;

[0064] Figure 4 is the modulation transfer function curve of the utility model at +70°C;

[0065] from Figure 2-Figure 4 It can be seen that the MTF curves of the center and edge fields of view are close to the diffraction limit, and the imaging quality is good after the surface system aberration is balanced; it can be obtained that the imaging quality of this optical system is good when the ambient temperature changes from -55℃ to +70℃.

[0066] Of course, this optical system can also be used for long-wave use in the band of 8-12um, and the detector is a long-wave cooling detector.

[0067] The present invention is not limited to the above-mentioned specific implementation modes, but extends to any new features or any new combination disclosed in this specification, as well as any new method or process steps or any new combination disclosed.

Claims

1. An aperture off-axis total reflection infrared optical system, comprising optical components and a lens barrel; characterized in that: The optical components include a primary mirror, a secondary mirror, a tertiary mirror, an aperture stop, and a detector; The incident light from the target is reflected by the primary mirror and forms a primary image plane between the primary mirror and the secondary mirror, and then reflects through the secondary mirror and the third mirror in sequence, reaching the focal plane of the detector without obstruction to form a target image; The entrance pupil is set in front of the primary mirror; The primary mirror and the secondary mirror are both eccentrically arranged in the Y-axis direction and tilted around the X-axis; The three mirrors are eccentrically arranged in the Y-axis direction.

2. The aperture off-axis total reflection infrared optical system according to claim 1, characterized in that: The optical element is made of the same material as the lens barrel.

3. The aperture off-axis total reflection infrared optical system according to claim 2, characterized in that: The optical element and the lens barrel are made of aluminum alloy material or silicon carbide material.

4. The aperture off-axis total reflection infrared optical system according to claim 1, characterized in that: The primary mirror is an even-order high-order aspheric surface, with an eccentricity of no more than 20 mm in the Y-axis direction and an inclination of no more than 6° around the X-axis.

5. The aperture off-axis total reflection infrared optical system according to claim 4, characterized in that: The secondary mirror is a quadratic curved surface, with an eccentricity of no more than 20 mm in the Y-axis direction and an inclination of no more than 6° around the X-axis.

6. The aperture off-axis total reflection infrared optical system according to claim 5, characterized in that: The three mirrors are even-order high-order aspherical surfaces, and the eccentricity in the Y-axis direction is no more than 10 mm.

7. The aperture off-axis total reflection infrared optical system according to claim 1, characterized in that: The focal power of the primary mirror is positive, the focal power of the secondary mirror is negative, and the focal power of the third mirror is positive.

8. The aperture off-axis total reflection infrared optical system according to claim 1, characterized in that: The optical components meet the following requirements: field of view is 6.44°×5.16° and focal length is 136 mm.

9. The aperture off-axis total reflection infrared optical system according to claim 1, characterized in that: The detector comprises a cold stop arranged at the aperture stop and a focal plane; the cold stop is arranged between the focal plane and the three mirrors; and the detector is a medium-wave refrigerated detector.

10. An aperture off-axis total reflection infrared optical system according to any one of claims 1 to 8, characterized in that: The incident optical axis of the incident light ray is parallel to the outgoing optical axis of the outgoing light ray.

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