Broadband refrigeration type infrared optical system

Abstract

The invention provides a broadband refrigeration type infrared optical system, which comprises a light convergence group, an aberration correction group and a rear end fixing group which are coaxially arranged along a first direction, the interval between the light convergence group and the aberration correction group is 160mm, and the interval between the aberration correction group and the rear end fixing group is 25mm; the light converging group comprises a first lens and a second lens, the front end surface and the rear end surface of the first lens are spherical surfaces and are made of silicon, the front surface of the second lens is aspheric, the rear surface of the second lens is spherical surface and is made of germanium; the aberration correction group comprises a third lens and a fourth lens; the rear end fixing group comprises a fifth lens, a sixth lens and a seventh lens, and the optical system only adopts germanium, silicon and other materials under the condition of correcting the chromatic aberration in the ultra-wide wave band, has high economical efficiency, and also ensures the maturity and stability of the technology at the same time.

Description

Technical Field

[0001] The present application relates to the field of infrared optical imaging technology, and in particular to a wide-band refrigerated infrared optical system. Background Art

[0002] Compared with visible light systems, infrared optical systems have the advantages of strong environmental adaptability, strong anti-interference ability, and good concealment. They have been widely used in various fields such as military, medical, security, electricity, remote sensing and industry;

[0003] The infrared optical systems in the existing technology are mainly concentrated in three atmospheric windows, and their bands are mainly distributed in the near-infrared band of 0.75-2.5um and the mid-infrared band of 3-5um. Their working bands are relatively narrow, and there are certain limitations in the channels for obtaining information. When obtaining target information outside the traditional band, the original infrared optical system cannot identify the target object; therefore, the infrared optical system needs to be redesigned to adapt to the receiving band;

[0004] Generally, when adjusting the wavelength of an infrared system, filters are usually added to the optical system to achieve the adjustment of different wavelengths. However, filters can only filter out light of a specific wavelength and allow light of a specific wavelength to pass through. They can only reduce the wavelength of the system but cannot broaden it.

[0005] This adjustment method does not play any role in obtaining target information outside the traditional band; usually the entire optical system needs to be readjusted, otherwise just replacing or adjusting the filter may affect the stability and accuracy of the system. Therefore, it is urgent to design an infrared optical system with a wider band. Summary of the invention

[0006] The purpose of the present application is to solve the above problems and provide a wide-band refrigerated infrared optical system, comprising a light converging group, an aberration correction group and a rear end fixing group coaxially arranged along a first direction, wherein the interval between the light converging group and the aberration correction group is 160 mm, and the interval between the aberration correction group and the rear end fixing group is 25 mm;

[0007] The light converging group includes a first lens and a second lens arranged along the first direction, with an interval of 3.5 mm between them, the first lens is a meniscus lens with positive focal power, and the second lens is a meniscus lens with negative focal power;

[0008] The aberration correction group includes a third lens and a fourth lens arranged along the first direction, which are used to correct the aberration between the lenses to ensure the correct propagation path of the light;

[0009] The rear end fixed group includes a fifth lens, a sixth lens and a seventh lens arranged along the first direction, and is used to focus the light emitted from the aberration correction group;

[0010] The optical system also includes an infrared detector, which includes a focal plane detector window coaxially arranged with the rear end fixing group.

[0011] According to the technical solution provided in the embodiment of the present application, the front surface of the second lens is an aspherical surface with a curvature radius of 500 mm; the rear surface is a spherical surface with a curvature radius of 250 mm.

[0012] According to the technical solution provided in the embodiment of the present application, the aperture of the third lens is 43 mm, the center thickness is 2.75 mm, the front surface is a spherical lens with a curvature radius of 50 mm, and the rear surface is an even-order aspheric lens with a curvature radius of 45 mm.

[0013] According to the technical solution provided in the embodiment of the present application, the aperture of the fourth lens is 36.5 mm, the center thickness is 4 mm, the front and rear surfaces are both spherical, the curvature radius of the front surface is 33 mm, and the curvature radius of the rear surface is 42 mm.

[0014] According to the technical solution provided in the embodiment of the present application, the front and rear end surfaces of the first lens are both spherical surfaces, the aperture is 84 mm, and the center thickness is 7.3 mm.

[0015] According to the technical solution provided in the embodiment of the present application, the materials of the second lens, the third lens and the fifth lens are all germanium.

[0016] According to the technical solution provided in the embodiment of the present application, the material of the fourth lens is chalcogenide glass.

[0017] According to the technical solution provided in the embodiment of the present application, the materials of the first lens, the sixth lens and the seventh lens are all silicon.

[0018] According to the technical solution provided in the embodiment of the present application, the fifth lens is an aspheric lens, the front surface of which is an even-order aspheric surface, the radius of curvature is 16 mm, and the center thickness is 2 mm.

[0019] According to the technical solution provided in the embodiment of the present application, the sixth lens and the seventh lens are standard spherical lenses, the curvature radius of the front surface of the sixth lens is -12 mm, the curvature radius of the rear surface is -18 mm, and the center thickness is 6 mm; the curvature radius of the front surface of the seventh lens is 35 mm, the curvature radius of the rear surface is 240 mm, and the center thickness is 5 mm.

[0020] Compared with the prior art, the present application has the following beneficial effects: the working band of the wide-band refrigerated infrared optical system described in the present application is 1.5um-5.5um, the system includes a light convergence group, an aberration correction group and a rear end fixing group arranged in sequence along a first direction, the light convergence group includes a first lens and a second lens, and the first lens is a meniscus lens with a positive optical power, and the second lens is a meniscus lens with a negative optical power; the aberration correction group includes a third lens and a fourth lens, which are used to correct the aberration between the lenses to ensure the correct propagation path of the light, the rear end fixing group includes a fifth lens, a sixth lens and a seventh lens, which are used to focus the light emitted from the aberration correction group, and the system also includes an infrared detector with a focal plane detector window;

[0021] During use, the infrared light from the target, that is, the object light, is focused on the focal plane of the infrared detector after passing through the light convergence group and the aberration correction group. The infrared detector receives the focused light and converts it into electrical signals, which are then processed and converted into readable images for identifying the target object.

[0022] The optical system described in the present application includes a light converging group, an aberration correction group and a rear-end fixing group. The light converging group is composed of a first lens and a second lens, and its main function is to converge the light from the target to the next optical element. Since it is designed to be closely arranged and the interval between the first lens and the second lens is 3.5 mm, the light energy collection capacity of the optical system can be effectively improved. At the same time, the first lens and the second lens are meniscus lenses, so that they can accurately control and converge the light. Because infrared light is prone to refraction and scattering when propagating in the medium, the aberration correction group mainly corrects the aberration between the lenses, thereby ensuring the correct propagation path of the light, thereby improving the imaging quality. The rear-end fixing group mainly stabilizes the rear end of the optical system, ensures the stability and accuracy of the optical system, and prevents the infrared light from being refracted and scattered due to external Environmental factors, such as system deformation caused by temperature changes, etc., can achieve chromatic aberration correction in an ultra-wide band range of 1.5um-5.5um; In summary, the present application can ensure that light can be correctly propagated and focused through light convergence, aberration correction and back-end fixation, and then convert the optical signal into an electrical signal through an infrared detector, and finally form a recognizable target image. The band used in the present application is wider than that of the optical system in the prior art, which greatly improves the ability of the optical system to identify the target object, and the optical system of the present application has a focal length of up to 200mm under wide-band conditions, and the ratio between the focal length and the virtual pupil is 2.5, that is, the aperture is 2.5. At the same time, it can also match a 640*512@25 micron detector, filling the gap in the ultra-wide band, long focal length and large relative aperture optical system architecture. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1An architectural diagram of an optical system provided in an embodiment of the present application;

[0024] Figure 2 A path diagram of the object-side light entering the embodiment of the present application;

[0025] Figure 3 The optical transfer function curve of the system provided in the embodiment of the present application at room temperature of 20°C;

[0026] Figure 4 The optical transfer function curve of the system provided in the embodiment of the present application at a low temperature of -40°C;

[0027] Figure 5 The optical transfer function curve of the system provided in the embodiment of the present application at a high temperature of 60°C;

[0028] Figure 6 The defocus curves of each field of view of the optical system provided in the embodiments of the present application.

[0029] The text labels in the figure are as follows: 101, the first lens; 102, the second lens; 201, the third lens; 202, the fourth lens; 301, the fifth lens; 302, the sixth lens; 303, the seventh lens. DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to better understand the technical solution of the present application, the present application is described in detail below in conjunction with the accompanying drawings. The description in this section is only exemplary and explanatory and should not have any limiting effect on the scope of protection of the present application.

[0031] Compared with visible light systems, infrared optical systems have the advantages of strong environmental adaptability, strong anti-interference ability, and good concealment. They have been widely used in various fields such as military, medical, security, electricity, remote sensing and industry;

[0032] The infrared optical systems in the prior art are mainly concentrated in three atmospheric windows, distributed in the near-infrared band of 0.75-2.5um and the mid-infrared band of 3-5um. Their working bands are relatively narrow. If the target object is not in the corresponding band, the existing infrared optical systems cannot identify the target object.

[0033] The purpose of the present application is to provide a wide-band refrigerated infrared optical system to solve the above problems. In order to ensure that the optical system maintains excellent imaging quality in the range of -40°C to +60°C when the spectral range is 1.5um-5.5um, the focal length is 200mm, the relative aperture is F2.5, and the detector is matched with 640*512@25um, and the aperture size of the optical system is compressed, and the stray light of the optical system is effectively controlled, the system adopts a secondary imaging configuration. The relative aperture is an important parameter in the optical system. It refers to the ratio of the effective aperture of the lens to the focal length. This ratio can be used to describe the amount of light that the lens absorbs. The size of the relative aperture indicates the ability of the lens to collect light. Generally speaking, the larger the relative aperture, the more light the lens collects, and the brighter the image.

[0034] The optical system described in the present application is capable of identifying target objects in the working band of 1.5um-5.5um. The optical system described in the present application includes:

[0035] A light converging group, an aberration correction group and a rear end fixing group are coaxially arranged along a first direction, wherein the interval between the light converging group and the aberration correction group is 160 mm, and the interval between the aberration correction group and the rear end fixing group is 25 mm;

[0036] The light converging group includes a first lens 101 and a second lens 102 arranged along the first direction, with a spacing of 3.5 mm therebetween, the first lens 101 being a meniscus lens with positive focal power, and the second lens 102 being a meniscus lens with negative focal power;

[0037] The aberration correction group includes a third lens 201 and a fourth lens 202 arranged along the first direction, which are used to correct the aberration between the lenses to ensure the correct propagation path of the light;

[0038] The rear fixed group includes a fifth lens 301, a sixth lens 302 and a seventh lens 303 arranged along the first direction, and is used to focus the light emitted from the aberration correction group;

[0039] The optical system also includes an infrared detector, which includes a focal plane detector window coaxially arranged with the rear end fixing group.

[0040] Specifically, in this embodiment, Figure 1 and Figure 2As shown, the optical system of the present application includes a light converging group, an aberration correction group and a rear end fixing group coaxially arranged along a first direction, the interval between the light converging group and the aberration correction group is 160 mm, the interval between the aberration correction group and the rear end fixing group is 25 mm, and the light converging group is responsible for converging the object side light into the optical path of the optical system, and can also reduce the angle between the light of different field beads and the optical axis of the optical system;

[0041] The light converging group includes a first lens 101 and a second lens 102 arranged along the first direction. The front and rear surfaces of the first lens 101 are both spherical surfaces. The material used for the first lens 101 is silicon. The parameters of the first lens 101 are as follows:

[0042] The first lens 101 has an aperture of 84 mm and a center thickness of 7.3 mm.

[0043] Specifically, in the present embodiment, the front and rear surfaces of the first lens 101 are both spherical lenses, the front surface curvature radius of the first lens 101 is 135 mm, and the rear surface curvature radius is 280 mm. In order to take into account the lightweight of the optical system, the aperture of the first lens 101 is 84 mm, and the center thickness is 7.3 mm. The first lens 101 is a meniscus lens with positive focal power, and its focal power is 0.009615. The focal power is used to characterize the degree of light deflection of the optical system.

[0044] The interval between the first lens 101 and the second lens 102 is 3.5 mm.

[0045] The material of the second lens 102 is germanium single crystal, and the parameters of the second lens 102 are as follows:

[0046] In order to correct the chromatic aberration of the optical system, the front surface of the second lens 102 is aspherical, and the rear surface is spherical. The curvature radius of the front surface of the second lens 102 is 500 mm, and the curvature radius of the rear surface is 250 mm. The aperture of the second lens 102 is 80 mm, and the center thickness is 4 mm. The 4th order coefficient of the front surface is A4=-7.414997218281000E-009, and the 6th order coefficient is The coefficient A6=8.3495500000000000E-013, the 8th order coefficient A8=-2.321390000000000E-016, the 10th order coefficient A10=9.106560000000000E-020, the 12th order coefficient A12=-2.363010000000000E-023, and the second lens 102 is a meniscus lens with negative optical power.

[0047] The aberration correction group is responsible for further correcting the aberration of the optical system, and simultaneously, together with the light converging group, images the object light once, so as to control the aperture size of the optical system. The aberration correction group includes a third lens 201 and a fourth lens 202 arranged along the first direction. The third lens 201 and the fourth lens 202 are made of germanium single crystal. The third lens 201 is an aspherical lens. The interval between the third lens 201 and the fourth lens 202 is 15.5 mm. The parameters of the third lens 201 are as follows:

[0048] The third lens 201 has an aperture of 43 mm and a center thickness of 2.75 mm. Its front surface is a spherical lens with a curvature radius of 50 mm, and its rear surface is an even-order aspherical lens with a curvature radius of 45 mm.

[0049] Specifically, in this embodiment, the front surface of the third lens 201 is a spherical surface with a curvature radius of 50 mm, and the rear surface is an even-order aspherical lens with a curvature radius of 45 mm. The 4th order coefficient of the aspherical surface is A4=6.30292E-007, the 6th order coefficient is A6=8.87896E-011, the 8th order coefficient is A8=-1.91419E-013, and the 10th order coefficient is A10=-3.53452E-017.

[0050] The fourth lens 202 is made of chalcogenide glass.

[0051] Specifically, in this embodiment, the material of the fourth lens 202 is IRG206 in the chalcogenide glass, and the parameters of the fourth lens 202 are as follows:

[0052] Furthermore, the fourth lens 202 has an aperture of 36.5 mm and a center thickness of 4 mm. Both its front and rear surfaces are spherical surfaces, the curvature radius of the front surface is 33 mm, and the curvature radius of the rear surface is 42 mm.

[0053] Specifically, in this embodiment, the fourth lens 202 is an ordinary spherical lens, the front surface curvature radius of the fourth lens 202 is 33 mm, the rear surface curvature radius is 42 mm, the aperture is 36.5 mm, and the center thickness is 4 mm.

[0054] The rear end fixed group includes a fifth lens 301, a sixth lens 302, and a seventh lens 303 coaxially arranged along the first direction;

[0055] Furthermore, the third lens 201 and the fifth lens 301 are both made of germanium.

[0056] Furthermore, the sixth lens 302 and the seventh lens 303 are both made of silicon.

[0057] Specifically, in the present embodiment, the material of the fifth lens 301 is germanium single crystal, the fifth lens 301 is a meniscus lens with negative optical power, the sixth lens 302 is a meniscus lens with negative optical power, the material of the sixth lens 302 and the material of the seventh lens 303 are both silicon single crystal, the seventh lens 303 is a meniscus lens with positive optical power, the interval between the fifth lens 301 and the sixth lens 302 is 5.5 mm, the interval between the sixth lens 302 and the seventh lens 303 is 7.5 mm, in order to control the stray light of the optical system, the height of each field of view light incident on the front surface of the fifth lens 301 is 3.2 mm, and considering the convenience of installation and debugging of the optical system, the edge interval between the seventh lens 303 and the detector window is 6 mm.

[0058] Furthermore, the fifth lens 301 is an aspheric lens, the front surface of which is an even-order aspheric surface, the radius of curvature is 16 mm, and the center thickness is 2 mm.

[0059] Specifically, in this embodiment, the fifth lens 301 is an aspheric lens, whose front surface is an even-order aspheric surface with a curvature radius of 16 mm and a center thickness of 2nn. The 4th-order coefficient of the even-order aspheric surface is A4=-9.93052E-006, the 6th-order coefficient is A6=3.54309E-007, the 8th-order coefficient is A8=-6.02956E-009, the 10th-order coefficient is A10=-1.58042E-010, the 12th-order coefficient is A12=7.40449E-012, and the 14th-order coefficient is A14=-8.43474E-014; the rear surface is a spherical surface with a curvature radius of 13.75 mm.

[0060] Furthermore, the sixth lens 302 and the seventh lens 303 are standard spherical lenses, the curvature radius of the front surface of the sixth lens 302 is -12 mm, the curvature radius of the rear surface is -18 mm, and the center thickness is 6 mm; the curvature radius of the front surface of the seventh lens 303 is 35 mm, the curvature radius of the rear surface is 240 mm, and the center thickness is 5 mm.

[0061] Specifically, in this embodiment, the sixth lens 302 and the seventh lens 303 are both standard spherical lenses, the sixth lens 302 has a front surface curvature radius of -12 mm, a rear surface curvature radius of -18 mm, and a center thickness of 6 mm, and the seventh lens 303 has a front surface curvature radius of 35 mm, a rear surface curvature radius of 240 mm, and a center thickness of 5 mm.

[0062] like Figure 3As shown, it is the optical transfer function curve of the optical system of the present application at room temperature of 20 degrees Celsius; Figure 4 As shown, it is the optical transfer function curve of the optical system of the present application at a low temperature of -40 degrees Celsius; Figure 5 As shown, it is the optical transfer function curve of the optical system of the present application at a high temperature of 60 degrees Celsius; in the optical transfer function curve, the smoother the curve and the higher the value at the cutoff frequency, the better the imaging quality of the system. Figure 3 , Figure 4 , Figure 5 It can be seen that the optical transfer function curves of each field of view of the system are all greater than 0.5 at the cutoff frequency of 20l p / mm, while the optical transfer function of most optical systems in the prior art is greater than 0.2 at the cutoff frequency. Therefore, the imaging quality of the optical system of the present application is greatly improved compared with the prior art. Figure 6 As shown, it is the defocus curve of each field of view of the optical system, wherein the horizontal axis represents the defocus amount, and the vertical axis represents the specific value of the optical transfer function at 20lp / mm. The smoother the defocus curve is, the greater the defocus range of the system can still ensure that the image clarity is not affected. The optical system described in this application is Figure 6 It can be seen that the defocus curve can still ensure that the image clarity is not affected within the defocus range of -0.10 to +0.10.

[0063] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and its core ideas of this application. The above is only the preferred implementation method of this application. It should be pointed out that due to the limitations of textual expression and the objective existence of infinite specific structures, ordinary technicians in this technical field can make several improvements, modifications or changes without departing from the principles of the present invention, and can also combine the above technical features in an appropriate manner; these improvements, modifications, changes or combinations, or the direct application of the inventive concept and technical solution to other occasions without improvement, should be regarded as the scope of protection of this application.

Claims

1. A wide-band refrigeration infrared optical system, characterized in that: The system comprises: A light converging group, an aberration correction group and a rear end fixing group are coaxially arranged along a first direction, wherein the interval between the light converging group and the aberration correction group is 160 mm, and the interval between the aberration correction group and the rear end fixing group is 25 mm; The light converging group comprises a first lens (101) and a second lens (102) arranged along the first direction, with a spacing of 3.5 mm between them, the first lens (101) being a meniscus lens with positive focal power, and the second lens (102) being a meniscus lens with negative focal power; The aberration correction group comprises a third lens (201) and a fourth lens (202) arranged along the first direction, which are used to correct the aberration between the lenses to ensure the correct propagation path of the light; The rear end fixed group comprises a fifth lens (301), a sixth lens (302) and a seventh lens (303) arranged along the first direction, and is used to focus the light emitted from the aberration correction group; The optical system also includes an infrared detector, which includes a focal plane detector window coaxially arranged with the rear end fixing group.

2. The wide-band refrigerated infrared optical system according to claim 1, characterized in that: The front surface of the second lens (102) is an aspherical surface with a curvature radius of 500 mm; the rear surface is a spherical surface with a curvature radius of 250 mm.

3. The wide-band refrigerated infrared optical system according to claim 1, characterized in that: The third lens (201) has an aperture of 43 mm and a center thickness of 2.75 mm. Its front surface is a spherical lens with a curvature radius of 50 mm, and its rear surface is an even-order aspherical lens with a curvature radius of 45 mm.

4. The wide-band refrigerated infrared optical system according to claim 1, characterized in that: The fourth lens (202) has an aperture of 36.5 mm and a center thickness of 4 mm. Its front and rear surfaces are both spherical surfaces, the curvature radius of the front surface is 33 mm, and the curvature radius of the rear surface is 42 mm.

5. The wide-band refrigerated infrared optical system according to claim 1, characterized in that: The front and rear end surfaces of the first lens (101) are both spherical surfaces, with an aperture of 84 mm and a center thickness of 7.3 mm.

6. The wide-band refrigerated infrared optical system according to claim 1, characterized in that: The materials of the second lens (201), the third lens (201) and the fifth lens (301) are all germanium.

7. The wide-band refrigerated infrared optical system according to claim 1, characterized in that: The material of the fourth lens (202) is chalcogenide glass.

8. The wide-band refrigerated infrared optical system according to claim 1, characterized in that: The materials of the first lens (101), the sixth lens (302) and the seventh lens (303) are all silicon.

9. The wide-band refrigerated infrared optical system according to claim 1, characterized in that: The fifth lens (301) is an aspheric lens, the front surface of which is an even aspheric surface, the radius of curvature is 16 mm, and the center thickness is 2 mm.

10. The wide-band refrigerated infrared optical system according to claim 1, characterized in that: The sixth lens (302) and the seventh lens (303) are standard spherical lenses. The radius of curvature of the front surface of the sixth lens (302) is -12 mm, the radius of curvature of the rear surface is -18 mm, and the center thickness is 6 mm. The radius of curvature of the front surface of the seventh lens (303) is 35 mm, the radius of curvature of the rear surface is 240 mm, and the center thickness is 5 mm.

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