Far infrared optical system and far infrared optical lens

Abstract

The invention discloses a far infrared optical system and a far infrared optical lens. The far infrared optical system sequentially comprises a first refraction lens, a second refraction lens and a third refraction lens from an object side to an image side along an optical axis, the focal power of the first refractor is negative, and the object side surface and the image side surface of the first refractor both protrude towards the object side; the focal power of the second refractor is positive, and the object side surface and the image side surface of the second refractor both protrude towards the image side; the focal power of the third refraction lens is positive, and the object side surface of the third refraction lens protrudes towards the object side; the far infrared optical system further comprises a first diffractive optical element and / or a second diffractive optical element arranged in a light path. The far-infrared optical system provided by the invention is small in size, the tolerance sensitivity of the far-infrared optical system is reduced by reasonably distributing the focal length of each lens, and the installation difficulty of the far-infrared optical system can be reduced.

Description

Technical Field

[0001] The present application relates to the field of optical systems, and in particular to a far-infrared optical system and a far-infrared optical lens. Background Art

[0002] The far-infrared optical system is an optical system whose working band is the far-infrared band. The far-infrared optical system has been widely used in many fields.

[0003] In order to ensure the imaging quality, the far-infrared optical system is usually provided with multiple lenses, which makes the volume of the far-infrared optical system larger, and the focal lengths of the lenses are prone to have large differences, resulting in uneven distribution of the focal length of the far-infrared optical system. Whether the focal lengths of the lenses are evenly distributed or not will have a great impact on the installation difficulty and temperature drift of the performance of the far-infrared optical system. Specifically, if the focal length of a certain lens in the far-infrared optical system is too small, the focal length of the far-infrared optical system will be concentrated on a certain lens, so that the light will be deflected at a large angle in this lens. Even if there is a small error in the installation position of the lens, the actual performance of the far-infrared optical system is significantly reduced compared to the design value due to the large contribution of the lens to the focal length of the system, that is, the far-infrared optical system has a problem of tolerance sensitivity. Therefore, in the far-infrared optical system with uneven focal length distribution, the lens with too large focal length has a high requirement for installation accuracy and needs to be installed more accurately at the expected position, but this will consume more manpower and material resources and is not conducive to mass production. Summary of the invention

[0004] In response to the above technical problems, the embodiments of the present application provide a far-infrared optical system and a far-infrared optical lens, aiming to provide a far-infrared optical system and a far-infrared optical lens with a smaller size and lower tolerance sensitivity.

[0005] According to one aspect of an embodiment of the present application, a far-infrared optical system is disclosed, and the far-infrared optical system includes, in order from the object side to the image side along the optical axis: a first refractive lens, a second refractive lens, and a third refractive lens; the optical focal length of the first refractive lens is negative, the object side surface of the first refractive lens is convex toward the object side, and the image side surface of the first refractive lens is convex toward the object side; the optical focal length of the second refractive lens is positive, the object side surface of the second refractive lens is convex toward the image side, and the image side surface of the second refractive lens is convex toward the image side; the optical focal length of the third refractive lens is positive, and the object side surface of the third refractive lens is convex toward the object side;

[0006] Wherein, the far-infrared optical system further comprises a first diffractive optical element arranged in the optical path of the far-infrared optical system and / or a second diffractive optical element arranged in the optical path of the far-infrared optical system;

[0007] The far-infrared optical system satisfies: ||f1|-|f2||<25mm, ||f1|-|f3||<20mm, wherein f1 is the focal length of the first refractive lens, f2 is the focal length of the second refractive lens, and f3 is the focal length of the third refractive lens.

[0008] In some embodiments, the far-infrared optical system also includes a fourth refractive lens; the fourth refractive lens is located between the first refractive lens and the second refractive lens, the optical focal length of the fourth refractive lens is negative, the object side surface of the fourth refractive lens is convex toward the object side, and the image side surface of the fourth refractive lens is convex toward the object side.

[0009] In some embodiments, the far-infrared optical system satisfies: Among them, the f m is the focal length of the diffractive optical element. When the far-infrared optical system includes the first diffractive optical element and the second diffractive optical element, the f m is the focal length of the smaller one of the first diffractive optical element and the second diffractive optical element, and f is the effective focal length of the far-infrared optical system.

[0010] In some embodiments, the far-infrared optical system satisfies: 0.06mm -1 <n1×(|c1|+|c2|)<0.4mm -1 , wherein n1 is the refractive index of the first refractive lens, c1 is the curvature of the object side surface of the first refractive lens, and c2 is the curvature of the image side surface of the first refractive lens.

[0011] In some embodiments, the far-infrared optical system satisfies: Among them, the CT i is the center thickness of the i-th refractive lens, the ET i is the thickness of the i-th refractive lens corresponding to its maximum effective diameter, and i is a positive integer.

[0012] In some embodiments, the far-infrared optical system satisfies: Among them, Lb is the distance between the image side surface of the third refractive lens and the image plane of the far-infrared optical system on the optical axis, ImgH is the imaging area radius of the far-infrared optical system on the image plane corresponding to the maximum field of view angle, and TTL is the total optical length of the far-infrared optical system.

[0013] In some embodiments, the far-infrared optical system satisfies: Wherein, Lb is the distance between the image side surface of the third refractive lens and the image plane of the far-infrared optical system on the optical axis, and θ bIt is the minimum value of the angle between the tangent line at any point on the surface of any refractive lens and the optical axis, and the TTL is the total optical length of the far-infrared optical system.

[0014] In some embodiments, the far-infrared optical system satisfies: Among them, the D i is the maximum effective diameter of the i-th refractive lens, the CT i is the central thickness of the i-th refractive lens, where i is a positive integer.

[0015] In some embodiments, the far-infrared optical system satisfies: Among them, the f i is the focal length of the i-th refractive lens, is the average value of the absolute values ​​of the focal lengths of all refractive lenses, and i is a positive integer.

[0016] In some embodiments, the far-infrared optical system satisfies: Among them, the D max is the largest of the maximum effective diameters of the refractive lenses, min It is the smallest of the maximum effective diameters of each refractive lens.

[0017] In some embodiments, the far-infrared optical system further includes an aperture, and the aperture is disposed between any two adjacent lenses; or, the aperture is disposed on the object side of the first refractive lens.

[0018] A second aspect of an embodiment of the present application provides a far-infrared optical lens, which includes: an imaging detector and a far-infrared optical system as described in any one of the above items; the imaging detector is arranged on the image plane of the far-infrared optical system.

[0019] The far-infrared optical system provided by the present application includes: a first refractive lens, a second refractive lens and a third refractive lens in sequence from the object side to the image side along the optical axis; the focal power of the first refractive lens is negative, the object side surface of the first refractive lens is convex to the object side, and the image side surface of the first refractive lens is convex to the object side; the focal power of the second refractive lens is positive, the object side surface of the second refractive lens is convex to the image side, and the image side surface of the second refractive lens is convex to the image side; the focal power of the third refractive lens is positive, and the object side surface of the third refractive lens is convex to the object side; wherein, the far-infrared optical system also includes a first diffractive optical element and / or a second diffractive optical element arranged in the optical path of the far-infrared optical system. The far-infrared optical system provided by the present application has a small size and good imaging quality. The far-infrared optical system can reduce the tolerance sensitivity of the far-infrared optical system by reasonably allocating the focal length of each lens, thereby reducing the installation difficulty of the far-infrared optical system and facilitating the mass production of the far-infrared optical system. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and other objects, features and advantages of the present application will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings.

[0021] Figure 1 A schematic diagram of the architecture layout of a far-infrared optical system in an embodiment of the present application is shown.

[0022] Figure 2 The MTF field of view curve of the far-infrared optical system in one embodiment of the present application is shown.

[0023] Figure 3 A schematic diagram of the architecture layout of a far-infrared optical system in an embodiment of the present application is shown.

[0024] Figure 4 The MTF field of view curve of the far-infrared optical system in one embodiment of the present application is shown.

[0025] Figure 5 A schematic diagram of the architecture layout of a far-infrared optical system in an embodiment of the present application is shown.

[0026] Figure 6 The MTF field of view curve of the far-infrared optical system in one embodiment of the present application is shown.

[0027] Figure 7 A schematic diagram of the architecture layout of a far-infrared optical system in an embodiment of the present application is shown.

[0028] Figure 8 The MTF field of view curve of the far-infrared optical system in one embodiment of the present application is shown.

[0029] Fig. 9 A schematic diagram of the architecture layout of a far-infrared optical system in an embodiment of the present application is shown.

[0030] Fig.10 The MTF field of view curve of the far-infrared optical system in one embodiment of the present application is shown.

[0031] Fig.11 A schematic diagram of the architecture layout of a far-infrared optical system in an embodiment of the present application is shown.

[0032] Fig.12 The MTF field of view curve of the far-infrared optical system in one embodiment of the present application is shown.

[0033] Reference numerals

[0034] 100. Far infrared optical system;

[0035] 10. a first refractive lens;

[0036] 20. a second refractive lens;

[0037] 30. The third refractive lens;

[0038] 40. Fourth refractive lens;

[0039] 50. first diffractive optical element; 510. substrate; 520. micro-nano structure;

[0040] 60. a second diffractive optical element;

[0041] 70. Aperture;

[0042] 80. Protective glass;

[0043] A, object plane; B, image plane; S, optical axis. DETAILED DESCRIPTION

[0044] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as limited to the examples set forth herein; rather, these example embodiments are provided so that the description of the present application will be more comprehensive and complete and the concepts of the example embodiments will be fully conveyed to those skilled in the art. The accompanying drawings are only schematic illustrations of the present application and are not necessarily drawn to scale. The same reference numerals in the figures represent the same or similar parts, and thus their repeated description will be omitted.

[0045] In addition, the described features, structures or characteristics may be combined in one or more example embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the example embodiments of the present application. However, those skilled in the art will appreciate that the technical solution of the present application may be practiced while omitting one or more of the specific details, or other modules, components, etc. may be adopted. In other cases, known structures, methods, implementations or operations are not shown or described in detail to avoid obscuring the present application and making the various aspects of the present application obscure.

[0046] See also Figure 1 , Figure 1 FIG. 1 shows a schematic diagram of the architecture layout of a far-infrared optical system 100 in an embodiment of the present application, wherein the optical axis S is the center line of the light beam. Figure 1 In the figure, the object is located on the left side of the leftmost lens, that is, the object side is located on the left side of the leftmost lens, and the object plane A is located on the object side. The image formed by the far-infrared optical system 100 is located on the right side of the rightmost lens, that is, the image side is located on the right side of the rightmost lens, and the image plane B is located on the image side. Therefore, the direction from the object plane A to the image plane B along the optical axis S is consistent with the direction from the object side to the image side along the optical axis S.

[0047] The side of each optical element of the far-infrared optical system 100 close to the object side is the object side of the corresponding optical element, and the side of each optical element of the far-infrared optical system 100 close to the image side is the image side of the corresponding optical element. For example, the side of the diaphragm 70 close to the object side is the object side of the diaphragm 70. The surface of each optical element of the far-infrared optical system 100 close to the object side is the object side surface of the corresponding optical element, and the surface of each optical element of the far-infrared optical system 100 close to the image side is the image side surface of the corresponding optical element. For example, the surface of the diaphragm 70 close to the image side is the image side surface of the diaphragm 70.

[0048] The far-infrared optical system 100 includes a first refractive lens 10 , a second refractive lens 20 and a third refractive lens 30 , which are sequentially arranged along an optical axis S from an object side to an image side.

[0049] The optical power of the first refractive lens 10 is negative, the object-side surface of the first refractive lens 10 is convex toward the object side, and the image-side surface of the first refractive lens 10 is convex toward the object side.

[0050] The optical power of the second refractive lens 20 is positive, the object-side surface of the second refractive lens 20 is convex toward the image side, and the image-side surface of the second refractive lens 20 is convex toward the image side.

[0051] The third refractive lens 30 has a positive refractive power, and the object-side surface of the third refractive lens 30 is convex toward the object side.

[0052] The far-infrared optical system 100 further includes a first diffractive optical element 50 and / or a second diffractive optical element 60. For details, see Figure 1 , Figure 5 In some embodiments, the far-infrared optical system 100 further includes a first diffractive optical element 50; see Figure 3 , Figure 7 , Fig.11 In some embodiments, the far-infrared optical system 100 further includes a second diffractive optical element 60; see Fig. 9 In some embodiments, the far-infrared optical system 100 includes both a first diffractive optical element 50 and a second diffractive optical element 60 .

[0053] The first diffractive optical element 50 and the second diffractive optical element 60 are both disposed in the optical path of the far-infrared optical system 100, that is, the first diffractive optical element 50 and the second diffractive optical element 60 can be disposed at any position in the optical path, for example, between two adjacent refractive lenses, or on the object side of the first refractive lens 10, or on the image side of the third refractive lens 30, or on the object side surface and / or the image side surface of a certain refractive lens. By introducing the first diffractive optical element 50 and / or the second diffractive optical element 60, it is possible to avoid using relatively expensive materials such as germanium for the lenses of the far-infrared optical system 100, and at the same time, it is possible to avoid having too many lenses of the far-infrared optical system 100.

[0054] The far-infrared optical system 100 provided by the present application is small in size and has good imaging quality. The far-infrared optical system 100 reduces the tolerance sensitivity of the far-infrared optical system 100 by reasonably allocating the focal lengths of the lenses, thereby reducing the difficulty of installing the far-infrared optical system 100 and facilitating mass production of the far-infrared optical system 100.

[0055] In some embodiments, the first diffractive optical element 50 is a super lens or a binary diffractive surface, and the second diffractive optical element 60 is a super lens or a binary diffractive surface. Figure 1 , Figure 5 , Fig. 9 In some embodiments, the first diffractive optical element 50 is a metalens; see Figure 3 , Figure 7 , Fig. 9 , Fig.11 In some embodiments, the second diffractive optical element 60 is a binary diffractive surface. A binary diffractive surface refers to a special type of optical surface that controls the diffraction behavior of light by forming a specific binary structure on the surface.

[0056] Please refer again Figure 1 , Figure 5 , Fig. 9 The metalens includes a substrate 510 and a micro-nano structure 520, and the micro-nano structure 520 is disposed on the surface of the substrate 510 close to the object side and / or the surface of the substrate 510 close to the image side. According to the phase modulation method adopted, the corresponding phase modulation formula can be adaptively used to configure the various parameters of the micro-nano structure 520, so that the metalens has the expected optical performance. The phase distribution of the metalens satisfies one of the following formulas:

[0057]

[0058] in, ris the distance from the center of the superlens to any micro-nanostructure 520, λ is the central wavelength of the working band of the superlens, is the phase constant, (x, y) is the two-dimensional coordinate of the surface of the metalens, a i , b i 、a ij , b ij are all real coefficients, N is the number of phase coefficients, f m is the focal length of the metalens.

[0059] In some embodiments, the micro-nano structure 520 is disposed on a surface of the substrate 510 close to the object side.

[0060] In some embodiments, the surface of the substrate 510 close to the object side and the surface of the substrate 510 close to the image side are both provided with micro-nano structures 520, so that the metalens has a higher degree of design freedom.

[0061] In some embodiments, the micro-nano structure 520 is a positive micro-nano structure.

[0062] In some embodiments, the micro-nano structure 520 is a negative micro-nano structure.

[0063] In some embodiments, the micro-nano structure 520 is provided with a layer to make the processing technology of the superlens compatible with the existing semiconductor processing technology, which can facilitate the processing and manufacturing of the superlens.

[0064] In some embodiments, the micro-nano structure 520 has two or more layers, so that the metalens has a larger optical power that meets the expected requirements.

[0065] For the superlens, the surface of the substrate 510 on which the micro-nano structure 520 is disposed, the positive and negative sides of the micro-nano structure 520, and the number of layers of the micro-nano structure 520 can be freely combined as long as the superlens has the expected performance.

[0066] Furthermore, in some embodiments, when the first diffractive optical element 50 and / or the second diffractive optical element 60 is a binary diffractive surface, the binary diffractive surface is integrated on the image side surface or the object side surface of the refractive lens to improve the integration of the far-infrared optical system 100, which is beneficial to reduce the volume and weight of the far-infrared optical system 100. Figure 3 , Figure 7 , Fig. 9 , Fig.11 The second diffractive optical element 60 is a binary diffractive surface, and the binary diffractive surface is integrated on the image side surface of the third refractive lens 30 .

[0067] See also Figure 1 , Figure 3 , Fig.11In some embodiments, the far-infrared optical system 100 further includes a fourth refractive lens 40, which is located between the first refractive lens 10 and the second refractive lens 20, the optical focal length of the fourth refractive lens 40 is negative, the object side surface of the fourth refractive lens 40 is convex toward the object side, and the image side surface of the fourth refractive lens 40 is convex toward the object side.

[0068] In some embodiments, the far-infrared optical system 100 satisfies conditional formula 1: ||f1|-|f2||<25mm, ||f1|-|f3||<20mm, wherein f1 is the focal length of the first refractive lens 10, f2 is the focal length of the second refractive lens 20, and f3 is the focal length of the third refractive lens 30.

[0069] It can be seen from Conditional Formula 1 that the differences among the absolute values ​​of the focal lengths of the first refractive lens 10, the second refractive lens 20, and the third refractive lens 30 are small, which can avoid the optical focal length of a certain lens in the far-infrared optical system 100 being much greater than the optical focal lengths of other lenses. Therefore, Conditional Formula 1 can be used to reasonably distribute the focal lengths of the first refractive lens 10, the second refractive lens 20, and the third refractive lens 30, thereby making the optical focal length distribution of the far-infrared optical system 100 more uniform, reducing the tolerance sensitivity of the far-infrared optical system 100, and reducing the processing difficulty and assembly difficulty of the far-infrared optical system 100, thereby facilitating mass production of the far-infrared optical system 100.

[0070] Furthermore, in some embodiments, the far-infrared optical system 100 satisfies the second conditional expression: ||f1|-|f2||<20mm, ||f1|-|f3||<15mm. The second conditional expression can more accurately distribute the focal length of the far-infrared optical system 100, thereby making the focal power distribution of the far-infrared optical system 100 more uniform, and further reducing the difficulty of processing and assembling the far-infrared optical system 100.

[0071] In some embodiments, the far-infrared optical system 100 satisfies conditional formula 3: Among them, f m is the focal length of the diffractive optical element. When the far-infrared optical system 100100 includes the first diffractive optical element 50 and the second diffractive optical element 60, f m is the focal length of the smaller one of the first diffractive optical element 50 and the second diffractive optical element 60. Specifically, when the diffractive optical element in the far-infrared optical system 100 is only the first diffractive optical element 50 or the second diffractive optical element 60, f m When the far-infrared optical system 100 includes a first diffractive optical element 50 and a second diffractive optical element 60, f mis the focal length of the first diffractive optical element 50 and the second diffractive optical element 60, whichever has the smaller focal length. f is the effective focal length of the far-infrared optical system 100, and f, f m The dimensions of are all length units, such as millimeters.

[0072] Conditional formula 3 reflects the focal length proportion of the first diffractive optical element 50 and / or the second diffractive optical element 60 in the far-infrared optical system 100, and reflects the contribution of the first diffractive optical element 50 and / or the second diffractive optical element 60 to focusing. The lower limit of conditional formula 3 reflects the maximum light focusing ability that the first diffractive optical element 50 and / or the second diffractive optical element 60 can provide, and the upper limit of conditional formula 3 reflects the minimum light converging ability that the first diffractive optical element 50 and / or the second diffractive optical element 60 should provide in the far-infrared optical system 100.

[0073] In some embodiments, the far-infrared optical system 100 satisfies conditional formula 4: 0.06 mm -1 <n1×(|c1|+|c2|)<0.4mm -1 , where n1 is the refractive index of the first refractive lens 10, c1 is the curvature of the object side surface of the first refractive lens 10, and c2 is the curvature of the image side surface of the first refractive lens 10. The dimensions of c1 and c2 are both the negative first power of the length unit, for example mm -1 .

[0074] Since the first refractive lens 10 is a negative meniscus lens, conditional formula 4 reflects the light divergence capability of the first refractive lens 10. The lower limit of conditional formula 4 ensures that the first refractive lens 10 still has a certain optical focal length when the refractive index of the first refractive lens 10 is low, that is, when the first refractive lens 10 is made of a low refractive index material, the first refractive lens 10 still has an optical focal length that meets expectations; the upper limit of conditional formula 4 ensures that when the refractive index of the first refractive lens 10 is large, the curvature of the object side surface and the image side surface of the first refractive lens 10 is not too large, thereby ensuring that the first refractive lens 10 has good processability.

[0075] In some embodiments, the far-infrared optical system 100 satisfies Condition 5: Among them, CT i is the central thickness of the i-th refractive lens; ET i ET1 is the thickness of the i-th refractive lens corresponding to its maximum effective diameter. For example, when the maximum effective diameter of the first refractive lens 10 is 30 mm, ET2 is the thickness of the first refractive lens 10 at a distance of 15 mm from the center of the first refractive lens 10. In this application, the maximum effective diameter of the lens is the diameter of the maximum light transmission area of ​​the lens, the same below. CT i , E.T. ihave the same dimension, which is a unit of length, such as millimeter.

[0076] i is a positive integer. For example, when i=1, CT1 is the center thickness of the first refractive lens 10, and ET1 is the thickness of the first refractive lens 10 corresponding to its maximum effective diameter. When i takes other values, CT i , E.T. i When the far-infrared optical system 100 includes the first refractive lens 10, the second refractive lens 20, the third refractive lens 30, and does not include the fourth refractive lens 40, 1≤i≤3, that is, n is 3, at this time Wherein, CT1 is the center thickness of the first refractive lens 10, ET1 is the thickness of the first refractive lens 10 corresponding to its maximum effective diameter, CT2 is the center thickness of the second refractive lens 20, ET2 is the thickness of the second refractive lens 20 corresponding to its maximum effective diameter, CT3 is the center thickness of the third refractive lens 30, and ET3 is the thickness of the third refractive lens 30 corresponding to its maximum effective diameter. When the far-infrared optical system 100 includes the first refractive lens 10, the second refractive lens 20, the third refractive lens 30, and the fourth refractive lens 40, 1-i≤4, that is, n is 4, at this time Among them, CT1 is the center thickness of the first refractive lens 10, ET1 is the thickness of the first refractive lens 10 corresponding to its own maximum effective diameter, CT2 is the center thickness of the second refractive lens 20, ET2 is the thickness of the second refractive lens 20 corresponding to its own maximum effective diameter, CT3 is the center thickness of the third refractive lens 30, ET3 is the thickness of the third refractive lens 30 corresponding to its own maximum effective diameter, CT4 is the center thickness of the fourth refractive lens 40, and ET4 is the thickness of the fourth refractive lens 40 corresponding to its own maximum effective diameter.

[0077] The conditional formula 5 generally reflects the degree of difficulty in processing the lenses of the far-infrared optical system 100. The upper limit of the conditional formula 5 reflects the easiest processing of the lenses in the far-infrared optical system 100, and the lower limit of the conditional formula 5 reflects the most difficult processing of the lenses in the far-infrared optical system 100. When the far-infrared optical system 100 satisfies the conditional formula 5, each refractive lens in the far-infrared optical system 100 can have good processability, which is beneficial to the mass production of the far-infrared optical system 100.

[0078] In some embodiments, the far-infrared optical system 100 satisfies conditional formula 6: Wherein, Lb is the distance between the image side surface of the third refractive lens 30 and the image plane B of the far-infrared optical system 100 on the optical axis S, and ImgH is the radius of the imaging area of ​​the far-infrared optical system 100 on the image plane B corresponding to the maximum field angle, that is, ImgH is half of the diagonal length of the imaging area of ​​the far-infrared optical system 100 on the image plane B. TTL (Total Track Length, TTL for short) is the total optical length of the far-infrared optical system 100. In the present application, TTL is equal to the distance from the optical surface closest to the object side to the image plane B of the far-infrared optical system 100 on the optical axis S, and the same below. Lb, ImgH, and TTL have the same dimension, which are all length units, such as millimeters.

[0079] Since the larger the ImgH is, the more image detectors the far-infrared optical system 100 can be compatible with, the smaller the TTL is, the more platforms the far-infrared optical system 100 can be mounted on, and the larger the Lb is, the more image detector interfaces and structures the infrared optical system can be compatible with, the conditional formula 6 reflects the compatibility and versatility of the far-infrared optical system 100. The upper limit of the conditional formula 6 reflects the highest versatility of the far-infrared optical system 100, and the lower limit of the conditional formula 6 reflects the lowest versatility of the far-infrared optical system 100.

[0080] In some embodiments, the far-infrared optical system 100 satisfies conditional equation 7: Wherein, Lb is the distance between the image side surface of the third refractive lens 30 and the image plane B of the far-infrared optical system 100 on the optical axis S, θ b Lb is the minimum value of the angle between the tangent line at any point on the object side and image side of any refractive lens in the far-infrared optical system 100 and the optical axis S, and TTL is the total optical length of the far-infrared optical system 100. Lb and TTL have the same dimension, both of which are length units, such as millimeters.

[0081] The first refractive lens 10, the second refractive lens 20, the third refractive lens 30 and the fourth refractive lens 40 are all traditional lenses. The larger the edge curvature of the traditional lens, the more difficult it is to process. The ratio of Lb to TTL reflects the volume compression of the far-infrared optical system 100, and conditional formula 7 reflects the effect of volume compression on the difficulty of lens processing. The lower limit of conditional formula 7 reflects the situation where compressing the volume of the far-infrared optical system 100 increases the difficulty of lens processing the least, and the upper limit of conditional formula 7 reflects the situation where compressing the volume of the far-infrared optical system 100 increases the difficulty of lens processing the most.

[0082] In some embodiments, the far-infrared optical system 100 satisfies Conditional Formula 8: Among them, D iis the maximum effective diameter of the i-th refractive lens. In this application, the maximum effective diameter of the object side of the lens refers to the diameter of the maximum light-transmitting area of ​​the object side of the lens, and the maximum effective diameter of the image side of the lens refers to the diameter of the maximum light-transmitting area of ​​the image side of the lens; the maximum effective diameter of the lens refers to the larger of the maximum effective diameter of the object side of the lens and the maximum effective diameter of the image side of the lens. i is the center thickness of the i-th refractive lens. i and CT i have the same dimension, which is a unit of length, such as millimeter.

[0083] i is a positive integer. For example, when i=1, D1 is the maximum effective diameter of the first refractive lens 10, and CT1 is the center thickness of the first refractive lens 10. When i takes other values, D i , CT i When the far-infrared optical system 100 includes the first refractive lens 10, the second refractive lens 20, the third refractive lens 30, and does not include the fourth refractive lens 40, 1≤i≤3, that is, n is 3, at this time Wherein, D1 is the maximum effective diameter of the first refractive lens 10, CT1 is the center thickness of the first refractive lens 10, D2 is the maximum effective diameter of the second refractive lens 20, CT2 is the center thickness of the second refractive lens 20, D3 is the maximum effective diameter of the third refractive lens 30, and CT3 is the center thickness of the third refractive lens 30. When the far-infrared optical system 100 includes the first refractive lens 10, the second refractive lens 20, the third refractive lens 30, and the fourth refractive lens 40, 1≤i≤4, that is, n is 4, at this time Among them, D1 is the maximum effective diameter of the first refractive lens 10, CT1 is the center thickness of the first refractive lens 10, D2 is the maximum effective diameter of the second refractive lens 20, CT2 is the center thickness of the second refractive lens 20, D3 is the maximum effective diameter of the third refractive lens 30, CT3 is the center thickness of the third refractive lens 30, D4 is the maximum effective diameter of the fourth refractive lens 40, and CT4 is the center thickness of the fourth refractive lens 40.

[0084] The ratio of the maximum effective diameter of the lens to the center thickness reflects the space occupancy of the lens under the premise of ensuring the processability and reliability of the lens. The combination of all refractive lenses in the far-infrared optical system 100 is recorded as a refractive lens group. The upper limit of conditional formula eight represents the maximum space occupancy of the refractive lens group in the far-infrared optical system 100, and the lower limit of conditional formula eight represents the minimum space occupancy of the refractive lens group in the far-infrared optical system 100.

[0085] In some embodiments, the far-infrared optical system 100 satisfies Condition 9: Among them, fi is the focal length of the i-th refractive lens, is the average of the absolute values ​​of the focal lengths of all refractive lenses. i , have the same dimension, which is a unit of length, such as millimeter.

[0086] i is a positive integer. For example, when i=1, f1 is the focal length of the first refractive lens 10. When i takes other values, f i When the far-infrared optical system 100 includes the first refractive lens 10, the second refractive lens 20, the third refractive lens 30, and does not include the fourth refractive lens 40, 1≤i≤3, that is, n is 3, and in this case, Wherein, f1 is the focal length of the first refractive lens 10, f2 is the focal length of the second refractive lens 20, and f3 is the focal length of the third refractive lens 30. When the far-infrared optical system 100 includes the first refractive lens 10, the second refractive lens 20, the third refractive lens 30, and the fourth refractive lens 40, 1≤i≤4, that is, n is 4, and in this case, Wherein, f1 is the focal length of the first refractive lens 10 , f2 is the focal length of the second refractive lens 20 , f3 is the focal length of the third refractive lens 30 , and f4 is the focal length of the fourth refractive lens 40 .

[0087] Conditional formula nine reflects the uniformity of focal length distribution among the refractive lenses in the far-infrared optical system 100. The smaller the value of conditional formula nine is, the closer the absolute values ​​of the focal lengths of the refractive lenses in the far-infrared optical system 100 are; otherwise, it indicates that the absolute value difference of the focal lengths of the refractive lenses in the far-infrared optical system 100 is large, that is, the focal length uniformity of the refractive lenses in the infrared optical system is poor. Uneven focal length distribution may cause some refractive lenses in the far-infrared optical system 100 to have a problem of too small focal length. Refractive lenses with too small focal lengths have problems such as low machinability and tolerance sensitivity. The upper limit of conditional formula nine represents the worst focal length distribution uniformity that the far-infrared optical system 100 can tolerate, and the lower limit of conditional formula nine represents the best focal length distribution uniformity that the far-infrared optical system 100 can provide.

[0088] In some embodiments, the far-infrared optical system 100 satisfies Conditional Formula 10: Among them, D max is the largest of the maximum effective diameters of the refractive lenses, D min It is the smallest of the maximum effective diameters of each refractive lens. max , D min have the same dimension, which is a unit of length, such as millimeter.

[0089] For example, when the far-infrared optical system 100 includes the first refractive lens 10, the second refractive lens 20, and the third refractive lens 30, and does not include the fourth refractive lens 40, D max is the largest of the maximum effective diameter D1 of the first refractive lens 10, the maximum effective diameter D2 of the second refractive lens 20, and the maximum effective diameter D3 of the third refractive lens 30; D min is the smallest of the maximum effective diameter D1 of the first refractive lens 10, the maximum effective diameter D2 of the second refractive lens 20, and the maximum effective diameter D3 of the third refractive lens 30. When the far-infrared optical system 100 includes the first refractive lens 10, the second refractive lens 20, the third refractive lens 30, and the fourth refractive lens 40, D max is the largest of the maximum effective diameter D1 of the first refractive lens 10, the maximum effective diameter D2 of the second refractive lens 20, the maximum effective diameter D3 of the third refractive lens 30, and the maximum effective diameter D4 of the fourth refractive lens 40; D min It is the smallest of the maximum effective diameter D1 of the first refractive lens 10 , the maximum effective diameter D2 of the second refractive lens 20 , the maximum effective diameter D3 of the third refractive lens 30 , and the maximum effective diameter D4 of the fourth refractive lens 40 .

[0090] Conditional formula 10 reflects the change of the beam diameter in the far-infrared optical system 100. The larger the value of conditional formula 10 is, the more dramatic the change of the beam diameter is. If the beam diameter changes dramatically, the far-infrared optical system 100 may have problems such as tolerance sensitivity and stray light. Therefore, conditional formula 10 reflects the actual performance of the far-infrared optical system 100 from the side. The upper limit of conditional formula 10 represents the maximum allowable optical diameter change of the far-infrared optical system 100, and the lower limit of conditional formula 10 represents the beam diameter change required for the far-infrared optical system 100 to achieve optical performance.

[0091] The far-infrared optical system 100 further includes an aperture 70, which is used to control the amount of light entering the far-infrared optical system 100, thereby ensuring that the far-infrared optical system 100 can work effectively and generate high-quality images.

[0092] In some embodiments, the aperture 70 is disposed between any two adjacent lenses in the far-infrared optical system 100, where the "lenses" include the first refractive lens 10, the second refractive lens 20, the third refractive lens 30, the fourth refractive lens 40, the first diffractive optical element 50, and the second diffractive optical element 60. Specifically, for ease of description, the lens close to the object side of any two adjacent lenses is recorded as the lens close to the object side, and the lens close to the image side of any two adjacent lenses is recorded as the lens close to the image side. The position where the aperture 70 is disposed satisfies any of the following conditions:

[0093] (1) The aperture 70 is located between the lens element close to the object side and the lens element close to the image side, and the aperture 70 is arranged in close contact with the image side surface of the lens element close to the object side;

[0094] (2) The aperture 70 is located between the lens close to the object side and the lens close to the image side, and the aperture 70 and the lens close to the object side and the lens close to the image side are spaced apart;

[0095] (3) The aperture 70 is located between the lens element close to the object side and the lens element close to the image side, and the aperture 70 is arranged to be attached to the object side surface of the lens element close to the image side.

[0096] In some embodiments, the aperture 70 is disposed on the object side of the first refractive lens 10. Specifically, the position where the aperture 70 is disposed satisfies any of the following conditions:

[0097] (1) The aperture 70 is disposed on the object side of the first refractive lens 10, and the aperture 70 is spaced apart from the first refractive lens 10;

[0098] (2) The aperture 70 is disposed on the object side of the first refractive lens 10 , and the aperture 70 is disposed on the object-side surface of the first refractive lens 10 , that is, the aperture 70 is disposed in contact with the object-side surface of the first refractive lens 10 .

[0099] In some embodiments, for ease of description, the last lens in the far-infrared optical system 100 along the direction from the object side to the image side is recorded as the final lens, and the final lens may be the second diffractive optical element 60. The far-infrared optical system 100 further includes a protective glass 80, which is located between the final lens and the image plane B, and the protective glass 80 is disposed close to the image plane B. The protective glass 80 is used to protect an imaging detector adapted to the far-infrared optical system 100, so as to reduce the probability of damage to the imaging detector.

[0100] The present application exemplarily provides six far-infrared optical systems 100 that meet usage requirements in six embodiments. Next, the far-infrared optical systems 100 provided in the various embodiments of the present application are introduced in detail.

[0101] Example 1

[0102] Figure 1 FIG. 1 shows a schematic diagram of the architecture layout of the far-infrared optical system 100 provided in Example 1. Figure 1 The mid-to-far infrared optical system 100 includes, in sequence from the object plane A to the image plane B along the optical axis S: a first refractive lens 10, a fourth refractive lens 40, an aperture 70, a second refractive lens 20, a first diffractive optical element 50, a third refractive lens 30, and a protective glass 80, wherein the first refractive lens 10, the second refractive lens 20, the third refractive lens 30, and the fourth refractive lens 40 are all aspherical lenses, the first diffractive optical element 50 is a super lens, and the micro-nano structure 520 of the super lens is arranged on the image side of the substrate 510.

[0103] Some parameters of the far-infrared optical system 100 provided in Example 1 are shown in Table 1-1.

[0104] Table 1-1. Partial parameters of the far-infrared optical system 100 provided in Example 1

[0105] parameter data Total optical length (TTL) 55.1mm Maximum field of view (2ω) 96° F-number 1.2 Effective focal length 10mm Working band 8μm-12μm

[0106] As can be seen from Table 1-1, the operating band of the far-infrared optical system 100 is 8μm-12μm, and the maximum field angle of the far-infrared optical system 100 reaches 96°, which can meet the requirements of large field imaging. The F number of the far-infrared optical system 100 is 1.2, which can greatly increase the amount of light entering the far-infrared optical system 100, and when the imaging detector has a low response to light energy, the energy entering the far-infrared optical system 100 is collected as much as possible, thereby ensuring excellent imaging quality.

[0107] Along the direction from the object plane A to the image plane B along the optical axis S, starting from the first refractive lens 10, each surface in the far-infrared optical system 100 is numbered, and the parameters of each surface are summarized to obtain the following Table 1-2.

[0108] Table 1-2. Parameters of various surfaces in the far-infrared optical system 100 provided in Example 1

[0109]

[0110]

[0111] For each surface in Table 1-2, surface 1 is the object side surface of the first refractive lens 10, and surface 2 is the image side surface of the first refractive lens 10. Surface 3 is the object side surface of the fourth refractive lens 40, and surface 4 is the image side surface of the fourth refractive lens 40. Surface 5 is the aperture 70, surface 6 is the object side surface of the second refractive lens 20, and surface 7 is the image side surface of the second refractive lens 20. Surface 8 is the object side surface of the first diffractive optical element 50, and surface 9 is the image side surface of the first diffractive optical element 50. Since the first diffractive optical element 50 is a super lens and the micro-nano structure 520 is located on the image side surface of the substrate 510, surface 9 is recorded as a structural surface. Surface 10 is the object side surface of the third refractive lens 30, and surface 11 is the image side surface of the third refractive lens 30. Surface 12 is the object side surface of the protective glass 80, and surface 13 is the image side surface of the protective glass 80. Surface 14 is the protective glass 80.

[0112] As can be seen from Table 1-2, surface 1 is an aspherical surface, the radius of curvature of surface 1 is 25.8 mm, the distance between surface 1 and surface 2 is 4.0 mm, and the material between surface 1 and surface 2 is IRG206. Surface 2 is an aspherical surface, the radius of curvature of surface 2 is 14.9 mm, the distance between surface 2 and surface 3 is 10.0 mm, and the material between surface 2 and surface 3 is air. Surface 3 is an aspherical surface, the radius of curvature of surface 3 is 22.0 mm, the distance between surface 3 and surface 4 is 3.0 mm, and the material between surface 3 and surface 4 is IRG206. Surface 4 is an aspherical surface, the radius of curvature of surface 4 is 18.0 mm, the distance between surface 4 and surface 5 is 4.6 mm, and the material between surface 4 and surface 5 is air. The radius of curvature of surface 5 is infinite, that is, surface 5 is a plane, the distance between surface 5 and surface 6 is 2.9 mm, and the material between surface 5 and surface 6 is air. Surface 6 is an aspherical surface, the radius of curvature of surface 6 is -376.0 mm, the distance between surface 6 and surface 7 is 3.6 mm, and the material between surface 6 and surface 7 is IRG204. Surface 7 is an aspherical surface, the radius of curvature of surface 7 is -31.0 mm, the distance between surface 7 and surface 8 is 8.0 mm, and the material between surface 7 and surface 8 is air. The radius of curvature of surface 8 is infinite, that is, surface 8 is a plane, the distance between surface 8 and surface 9 is 0.3 mm, and the material between surface 8 and surface 9 is silicon. The radius of curvature of surface 9 is infinite, therefore, surface 9 is a plane, the distance between surface 9 and surface 10 is 1.2 mm, and the material between surface 9 and surface 10 is air. Surface 10 is an aspherical surface, the radius of curvature of surface 10 is 51.1 mm, the distance between surface 10 and surface 11 is 4.3 mm, and the material between surface 10 and surface 11 is IRG206. Surface 11 is an aspheric surface, the radius of curvature of surface 11 is -144.9 mm, the distance between surface 11 and surface 12 is 10.3 mm, and the material between surface 11 and surface 12 is air. The radius of curvature of surface 12 is infinite, that is, surface 12 is a plane, the distance between surface 12 and surface 13 is 0.7 mm, and the material between surface 12 and surface 13 is germanium. The radius of curvature of surface 13 is infinite, that is, surface 13 is a plane, the distance between surface 13 and surface 14 is 2.2 mm, and the material between surface 13 and surface 14 is air.

[0113] Surface 1, surface 2, surface 3, surface 4, surface 6, surface 7, surface 10, and surface 11 are all even-order aspheric surfaces, and their surface shapes satisfy the following relationship:

[0114]

[0115] Among them, Z(r) is the distance vector height from the vertex of the aspherical surface when the aspherical surface is at a height of r along the optical axis S direction; c is the curvature of the aspherical surface, c=1 / R, R is the radius of curvature of the aspherical surface; k is the cone coefficient; A, B, C, D... are the aspherical coefficients. The values ​​of k, A, B, C, D... of surface 1, surface 2, surface 3, surface 4, surface 6, surface 7, surface 10, and surface 11 can all be obtained from Table 1-3.

[0116] Table 1-3. Coefficients of the even-order aspheric surfaces in the far-infrared optical system 100 provided in Example 1

[0117]

[0118] Please refer to Table 1-3. For surface 1, k is -18.4, A is 1.3E-04, B is -7.8E-07, C is 4.3E-09, D is -1.4E-11, E is 2.7E-14, F is -2.6E-17, and G is -8.0E-21. The coefficients of the even-order aspheric surfaces of surface 2, surface 3, surface 4, surface 6, surface 7, surface 10, and surface 11 can be obtained from Table 1-3, and will not be explained here one by one.

[0119] See also Figure 2 , Figure 2 The MTF (Modulation Transfer Function, MTF for short) field of view curve of the far-infrared optical system 100 provided in Example 1 is shown. Figure 2 The horizontal axis in is the Y-axis field of view, and its unit is degree; Figure 2 The vertical axis is the MTF value. Figure 2 The sagittal curve S1 and the meridional curve T1 of the MTF with 21lp / mm spatial frequency as the field of view changes, and the sagittal curve S2 and the meridional curve T2 of the MTF with 42lp / mm spatial frequency as the field of view changes are listed in the table. Figure 2 It can be seen that within the 0.9 field of view (43.2°), the MTF is greater than 0.3, and the imaging quality of the far-infrared optical system 100 is excellent.

[0120] Example 2

[0121] Figure 3 FIG. 1 shows a schematic diagram of the architecture layout of the far-infrared optical system 100 provided in Example 2. Figure 3The mid-to-far infrared optical system 100 includes, along the optical axis S, from the object plane A to the image plane B, in sequence: a first refractive lens 10, a fourth refractive lens 40, an aperture 70, a second refractive lens 20, a third refractive lens 30, a second diffractive optical element 60, and a protective glass 80, wherein the first refractive lens 10, the second refractive lens 20, and the fourth refractive lens 40 are all aspherical lenses, the object side surface and the image side surface of the third refractive lens 30 are both aspherical surfaces, the second diffractive optical element 60 is a binary diffractive surface, and the second diffractive optical element 60 is integrated with the image side surface of the third refractive lens 30. Some parameters of the far infrared optical system 100 provided in Example 2 are shown in Table 2-1.

[0122] Table 2-1. Partial parameters of the far-infrared optical system 100 provided in Example 2

[0123] parameter data Total optical length (TTL) 54.9mm Maximum field of view (2ω) 96° F-number 1.2 Effective focal length 10mm Working band 8μm-12μm

[0124] As can be seen from Table 2-1, the operating band of the far-infrared optical system 100 is 8μm-12μm, and the maximum field angle of the far-infrared optical system 100 reaches 96°, which can meet the requirements of large field imaging. The F number of the far-infrared optical system 100 is 1.2, which can greatly increase the amount of light entering the far-infrared optical system 100, and collect as much energy as possible entering the far-infrared optical system 100 when the imaging detector has a low response to light energy, thereby ensuring excellent imaging quality.

[0125] Along the direction from the object plane A to the image plane B along the optical axis S, starting from the first refractive lens 10, each surface in the far-infrared optical system 100 is numbered, and the parameters of each surface are summarized to obtain the following Table 2-2.

[0126] Table 2-2. Parameters of various surfaces in the far-infrared optical system 100 provided in Example 2

[0127]

[0128]

[0129] The analysis of each surface in Table 2-2 can refer to Example 1, and no analysis is performed again in this example.

[0130] Surface 1, surface 2, surface 3, surface 4, surface 6, surface 7, surface 8, and surface 9 are all even-order aspheric surfaces, and their surface shapes satisfy the following relationship:

[0131]

[0132] Among them, Z(r) is the distance vector height from the vertex of the aspherical surface when the aspherical surface is at a height of r along the optical axis S direction; c is the curvature of the aspherical surface, c=1 / R, R is the radius of curvature of the aspherical surface; k is the cone coefficient; A, B, C, D... are the aspherical coefficients. The values ​​of k, A, B, C, D... of Surface 1, Surface 2, Surface 3, Surface 4, Surface 6, Surface 7, Surface 8, Surface 9 can all be obtained from Table 2-3.

[0133] Table 2-3. Coefficients of the even-order aspheric surfaces in the far-infrared optical system 100 provided in Example 2

[0134]

[0135] The even-order aspheric coefficients of surface 1, surface 2, surface 3, surface 4, surface 6, surface 7, surface 8, and surface 9 can be obtained from Table 2-3 and will not be repeated here.

[0136] The coefficients of the binary diffraction surface can be obtained from Table 2-4.

[0137] Table 2-4. Coefficients of the binary diffraction surface in the far-infrared optical system 100 provided in Example 2

[0138]

[0139]

[0140] See also Figure 4 , Figure 4 FIG. 2 shows the MTF field curve of the far-infrared optical system 100 provided in Example 2. Figure 4 The horizontal axis in is the Y-axis field of view, and its unit is degree; Figure 4 The vertical axis is the MTF value. Figure 4 The sagittal curve S1 and the meridional curve T1 of the MTF with 21lp / mm spatial frequency as the field of view changes, and the sagittal curve S2 and the meridional curve T2 of the MTF with 42lp / mm spatial frequency as the field of view changes are listed in the table. Figure 4 It can be seen that within the range of 0.8 field of view (38.4°), the MTF is greater than 0.3, and the imaging quality of the far-infrared optical system 100 is excellent.

[0141] Example 3

[0142] Figure 5 FIG. 1 shows a schematic diagram of the architecture layout of the far-infrared optical system 100 provided in Example 3. Figure 5The mid-infrared optical system 100 includes, along the optical axis S from the object plane A to the image plane B, a first refractive lens 10, an aperture 70, a second refractive lens 20, a first diffractive optical element 50, a third refractive lens 30, and a protective glass 80, wherein the first refractive lens 10, the second refractive lens 20, and the third refractive lens 30 are all aspherical lenses, the first diffractive optical element 50 is a super lens, and the micro-nano structure 520 of the super lens is disposed on the image side of the substrate 510. Some parameters of the far-infrared optical system 100 provided in Example 3 are shown in Table 3-1.

[0143] Table 3-1. Partial parameters of the far-infrared optical system 100 provided in Example 3

[0144] parameter data Total optical length (TTL) 55mm Maximum field of view (2ω) 97.2° F-number 1.21 Effective focal length 9.75mm Working band 8μm-12μm

[0145] As shown in Table 3-1, the operating band of the far-infrared optical system 100 is 8μm-12μm, and the maximum field angle of the far-infrared optical system 100 reaches 97.24°, which can meet the requirements of large field imaging. The F number of the far-infrared optical system 100 is 1.21, which can greatly increase the amount of light entering the far-infrared optical system 100, and collect as much energy as possible entering the far-infrared optical system 100 when the imaging detector has a low response to light energy, thereby ensuring excellent imaging quality.

[0146] Along the direction of the optical axis S from the object plane A to the image plane B, starting from the first refractive lens 10, each surface in the far-infrared optical system 100 is numbered, and the parameters of each surface are summarized to obtain the following Table 3-2.

[0147] Table 3-2. Parameters of various surfaces in the far-infrared optical system 100 provided in Example 3

[0148] Surface serial number Surface type Curvature radius (mm) Thickness(mm) Material 1 Aspheric 7785.2 4.3 IRG206 2 Aspheric 44.3 15.1 3 Aperture surface unlimited 1.5 4 Aspheric -38.9 4.0 IRG204 5 Aspheric -22.4 9.2 6 Spherical unlimited 0.3 Si 7 Structural surface unlimited 1.7 8 Aspheric 68.3 4.6 IRG206 9 Aspheric -78.0 11.4 10 Spherical unlimited 0.7 Ge 11 Spherical unlimited 2.2 12 Image plane unlimited - -

[0149] The analysis of each surface in Table 3-2 can refer to Example 1, and no analysis is performed again in this example.

[0150] Surface 1, surface 2, surface 4, surface 5, surface 8, and surface 9 are all even-order aspheric surfaces, and their surface shapes satisfy the following relationship:

[0151]

[0152] Among them, Z(r) is the distance vector height from the vertex of the aspherical surface when the aspherical surface is at a height of r along the optical axis S direction; c is the curvature of the aspherical surface, c=1 / R, R is the curvature radius of the aspherical surface; k is the cone coefficient; A, B, C, D... are the aspherical coefficients. The values ​​of k, A, B, C, D... of Surface 1, Surface 2, Surface 4, Surface 5, Surface 8, and Surface 9 can all be obtained from Table 3-3.

[0153] Table 3-3. Coefficients of the even-order aspheric surfaces in the far-infrared optical system 100 provided in Example 3

[0154]

[0155] The even-order aspheric coefficients of surface 1, surface 2, surface 3, surface 4, surface 6, surface 7, surface 8, and surface 9 can be obtained from Table 3-3 and will not be repeated here.

[0156] See also Figure 6 , Figure 6 FIG. 1 shows the MTF field curve of the far-infrared optical system 100 provided in Example 3. Figure 6 The horizontal axis in is the Y-axis field of view, and its unit is degree; Figure 6 The vertical axis is the MTF value. Figure 6 The sagittal curve S1 and the meridional curve T1 of the MTF with 21lp / mm spatial frequency as the field of view changes, and the sagittal curve S2 and the meridional curve T2 of the MTF with 42lp / mm spatial frequency as the field of view changes are listed in the table. Figure 6 It can be seen that within the full field of view (48.6°), the MTF is greater than 0.28, and the imaging quality of the far-infrared optical system 100 is excellent.

[0157] Example 4

[0158] Figure 7 FIG. 1 shows a schematic diagram of the architecture layout of the far-infrared optical system 100 provided in Example 4. Figure 7 The mid-to-far infrared optical system 100 includes, along the optical axis S from the object plane A to the image plane B, a first refractive lens 10, an aperture 70, a second refractive lens 20, a third refractive lens 30, a second diffractive optical element 60, and a protective glass 80, wherein the first refractive lens 10 and the second refractive lens 20 are both aspherical lenses, the image side surface and the object side surface of the third refractive lens 30 are both aspherical surfaces, the second diffractive optical element 60 is a binary diffractive surface, and the second diffractive optical element 60 is integrated with the image side surface of the third refractive lens 30. Some parameters of the far infrared optical system 100 provided in Example 4 are shown in Table 4-1.

[0159] Table 4-1. Partial parameters of the far-infrared optical system 100 provided in Example 4

[0160] parameter data Total optical length (TTL) 55mm Maximum field of view (2ω) 97.2° F-number 1.2 Effective focal length 9.87mm Working band 8μm-12μm

[0161] As shown in Table 4-1, the operating band of the far-infrared optical system 100 is 8μm-12μm, and the maximum field angle of the far-infrared optical system 100 reaches 97.2°, which can meet the requirements of large field imaging. The F number of the far-infrared optical system 100 is 1.2, which can greatly increase the amount of light entering the far-infrared optical system 100, and collect as much energy as possible entering the far-infrared optical system 100 when the imaging detector has a low response to light energy, thereby ensuring excellent imaging quality.

[0162] Along the direction from the object plane A to the image plane B along the optical axis S, starting from the first refractive lens 10, each surface in the far-infrared optical system 100 is numbered, and the parameters of each surface are summarized to obtain the following Table 4-2.

[0163] Table 4-2. Parameters of various surfaces in the far-infrared optical system 100 provided in Example 4

[0164]

[0165]

[0166] For the analysis of each surface in Table 4-2, please refer to Example 1, and no analysis is performed again in this example.

[0167] Surface 1, surface 2, surface 4, surface 5, surface 6, and surface 7 are all even-order aspheric surfaces, and their surface shapes satisfy the following relationship:

[0168]

[0169] Among them, Z(r) is the distance vector height from the vertex of the aspherical surface when the aspherical surface is at a height of r along the optical axis S; c is the curvature of the aspherical surface, c = 1 / R, R is the radius of curvature of the aspherical surface; k is the cone coefficient; A, B, C, D... are the aspherical coefficients. The values ​​of k, A, B, C, D... of Surface 1, Surface 2, Surface 4, Surface 5, Surface 6, Surface 7 can all be obtained from Table 4-3.

[0170] Table 4-3. Coefficients of the even-order aspheric surfaces in the far-infrared optical system 100 provided in Example 4

[0171]

[0172] The even-order aspheric coefficients of surface 1, surface 2, surface 4, surface 5, surface 6, and surface 7 can be obtained from Table 4-3 and will not be repeated here.

[0173] The coefficients of the binary diffraction surface can be obtained from Table 4-4.

[0174] Table 4-4. Coefficients of the binary diffraction surface in the far-infrared optical system 100 provided in Example 4

[0175] Surface serial number 2 times 4 times 6 times 8 times 10 times 12 times 14 times 16 times 7 -4.7E-01 8.6E-04 -2.0E-05 2.7E-07 -1.6E-09 1.1E-12 2.2E-14 -6.2E-17

[0176] See also Figure 8 , Figure 8 FIG. 4 shows the MTF field curve of the far-infrared optical system 100 provided in Example 4. Figure 8 The horizontal axis in is the Y-axis field of view, and its unit is degree; Figure 8 The vertical axis is the MTF value. Figure 8 The sagittal curve S1 and the meridional curve T1 of the MTF with 21lp / mm spatial frequency as the field of view changes, and the sagittal curve S2 and the meridional curve T2 of the MTF with 42lp / mm spatial frequency as the field of view changes are listed in the table. Figure 8 It can be seen that within the range of 1.0 field of view (48.6°), the MTF is greater than 0.24, and the imaging quality of the far-infrared optical system 100 is excellent.

[0177] Example 5

[0178] Fig. 9 FIG. 1 shows a schematic diagram of the architecture layout of the far-infrared optical system 100 provided in Example 5. Fig. 9 The mid-infrared optical system 100 includes, along the optical axis S from the object plane A to the image plane B, the first refractive lens 10, the aperture 70, the second refractive lens 20, the first diffractive optical element 50, the third refractive lens 30, the second diffractive optical element 60, and the protective glass 80, wherein the first refractive lens 10 and the second refractive lens 20 are both aspheric lenses, and the image side surface and the object side surface of the third refractive lens 30 are both aspheric surfaces; the first diffractive optical element 50 is a super lens, and the micro-nano structure 520 of the super lens is arranged on the image side surface of the substrate 510, the second diffractive optical element 60 is a binary diffractive surface, and the second diffractive optical element 60 is integrated on the image side surface of the third refractive lens 30. Some parameters of the far-infrared optical system 100 provided in Example 5 are shown in Table 5-1.

[0179] Table 5-1. Partial parameters of the far-infrared optical system 100 provided in Example 5

[0180] parameter data Total optical length (TTL) 55.2mm Maximum field of view (2ω) 97.2° F-number 1.2 Effective focal length 9.85mm Working band 8μm-12μm

[0181] As shown in Table 5-1, the operating band of the far-infrared optical system 100 is 8μm-12μm, and the maximum field angle of the far-infrared optical system 100 reaches 97.2°, which can meet the requirements of large field imaging. The F number of the far-infrared optical system 100 is 1.2, which can greatly increase the amount of light entering the far-infrared optical system 100, and collect as much energy as possible entering the far-infrared optical system 100 when the imaging detector has a low response to light energy, thereby ensuring excellent imaging quality.

[0182] Along the direction from the object plane A to the image plane B along the optical axis S, starting from the first refractive lens 10, each surface in the far-infrared optical system 100 is numbered, and the parameters of each surface are summarized to obtain the following Table 5-2.

[0183] Table 5-2. Parameters of various surfaces in the far-infrared optical system 100 provided in Example 5

[0184] Surface serial number Surface type Curvature radius (mm) Thickness(mm) Material 1 Aspheric 52.2 4.3 IRG206 2 Aspheric 23.3 15.3 3 Aperture surface unlimited 1.2 4 Aspheric -42.1 3.8 IRG204 5 Aspheric -24.7 2.9 6 Spherical unlimited 0.3 Si 7 Structural surface unlimited 8.2 8 Aspheric 44.4 5.2 IRG206 9 Binary diffraction surface -123.6 11.1 10 Spherical unlimited 0.7 Ge 11 Spherical unlimited 2.2 12 Image plane unlimited - -

[0185] The analysis of each surface in Table 5-2 can refer to Example 1, and no further analysis is performed in this example.

[0186] Surface 1, surface 2, surface 4, surface 5, surface 8, and surface 9 are all even-order aspheric surfaces, and their surface shapes satisfy the following relationship:

[0187]

[0188] Among them, Z(r) is the distance vector height from the vertex of the aspherical surface when the aspherical surface is at a height of r along the optical axis S; c is the curvature of the aspherical surface, c = 1 / R, R is the radius of curvature of the aspherical surface; k is the cone coefficient; A, B, C, D... are the aspherical coefficients. The values ​​of k, A, B, C, D... of Surface 1, Surface 2, Surface 4, Surface 5, Surface 8, and Surface 9 can all be obtained from Table 5-3.

[0189] Table 5-3. Coefficients of the even-order aspheric surfaces in the far-infrared optical system 100 provided in Example 5

[0190]

[0191] The even-order aspheric coefficients of Surface 1, Surface 2, Surface 4, Surface 5, Surface 8, and Surface 9 can be obtained from Table 5-3 and will not be elaborated here one by one.

[0192] The coefficients of the binary diffraction surface can be obtained from Table 5-4.

[0193] Table 5-4. Coefficients of the binary diffraction surface in the far-infrared optical system 100 provided in Example 5

[0194]

[0195] See also Fig.10 , Fig.10 FIG. 5 shows the MTF field curve of the far-infrared optical system 100 provided in Example 5. Fig.10 The horizontal axis in is the Y-axis field of view, and its unit is degree; Fig.10 The vertical axis is the MTF value. Fig.10 The sagittal curve S1 and the meridional curve T1 of the MTF with 21lp / mm spatial frequency as the field of view changes, and the sagittal curve S2 and the meridional curve T2 of the MTF with 42lp / mm spatial frequency as the field of view changes are listed in the table. Fig.10 It can be seen that within the range of 1.0 field of view (48.6°), the MTF is greater than 0.28, and the imaging quality of the far-infrared optical system 100 is excellent.

[0196] Example 6

[0197] Fig.11 FIG. 1 shows a schematic diagram of the architecture layout of the far-infrared optical system 100 provided in Example 6. Fig.11 The mid-to-far infrared optical system 100 includes, along the optical axis S, from the object plane A to the image plane B, in sequence: a first refractive lens 10, a fourth refractive lens 40, an aperture 70, a second refractive lens 20, a third refractive lens 30, a second diffractive optical element 60, and a protective glass 80, wherein the first refractive lens 10, the second refractive lens 20, and the fourth refractive lens 40 are all aspherical lenses, the object side surface and the image side surface of the third refractive lens 30 are both aspherical surfaces, the second diffractive optical element 60 is a binary diffractive surface, and the second diffractive optical element 60 is integrated with the image side surface of the third refractive lens 30. Some parameters of the far infrared optical system 100 provided in Example 6 are shown in Table 6-1.

[0198] Table 6-1. Partial parameters of the far-infrared optical system 100 provided in Example 6

[0199] parameter data Total optical length (TTL) 55mm Maximum field of view (2ω) 96° F-number 1.2 Effective focal length 10mm Working band 8μm-12μm

[0200] As can be seen from Table 6-1, the operating band of the far-infrared optical system 100 is 8μm-12μm, and the maximum field angle of the far-infrared optical system 100 reaches 96°, which can meet the requirements of large field imaging. The F number of the far-infrared optical system 100 is 1.2, which can greatly increase the amount of light entering the far-infrared optical system 100, and collect as much energy as possible entering the far-infrared optical system 100 when the imaging detector has a low response to light energy, thereby ensuring excellent imaging quality.

[0201] Along the direction from the object plane A to the image plane B along the optical axis S, starting from the first refractive lens 10, each surface in the far-infrared optical system 100 is numbered, and the parameters of each surface are summarized to obtain the following Table 6-2.

[0202] Table 6-2. Parameters of various surfaces in the far-infrared optical system 100 provided in Example 6

[0203] Surface serial number Surface type Curvature radius (mm) Thickness(mm) Material 1 Aspheric 24.4 4.1 IRG209 2 Aspheric 15.3 10.0 3 Aspheric 22.6 3.0 IRG206 4 Aspheric 17.9 4.2 5 Aperture surface unlimited 2.9 6 Aspheric -2927.4 3.6 IRG204 7 Aspheric -36.4 8.5 8 Aspheric 67.4 4.4 IRG206 9 Binary diffraction surface -66.4 11.4 10 Spherical unlimited 0.7 Ge 11 Spherical unlimited 2.2 12 Image plane unlimited - -

[0204] The analysis of each surface in Table 6-2 can refer to Example 1, and no analysis is performed again in this example.

[0205] Surface 1, surface 2, surface 3, surface 4, surface 6, surface 7, surface 8, and surface 9 are all even-order aspheric surfaces, and their surface shapes satisfy the following relationship:

[0206]

[0207] Among them, Z(r) is the distance vector height from the vertex of the aspherical surface when the aspherical surface is at a height of r along the optical axis S direction; c is the curvature of the aspherical surface, c=1 / R, R is the radius of curvature of the aspherical surface; k is the cone coefficient; A, B, C, D... are the aspherical coefficients. The values ​​of k, A, B, C, D... of Surface 1, Surface 2, Surface 3, Surface 4, Surface 6, Surface 7, Surface 8, Surface 9 can all be obtained from Table 6-3.

[0208] Table 6-3. Coefficients of the even-order aspheric surfaces in the far-infrared optical system 100 provided in Example 6

[0209]

[0210]

[0211] The even-order aspheric coefficients of surface 1, surface 2, surface 3, surface 4, surface 6, surface 7, surface 8, and surface 9 can be obtained from Table 6-3 and will not be repeated here.

[0212] The coefficients of the binary diffraction surface can be obtained from Table 6-4.

[0213] Table 6-4. Coefficients of the binary diffraction surface in the far-infrared optical system 100 provided in Example 6

[0214] Surface serial number 2 times 4 times 6 times 8 times 10 times 12 times 14 times 16 times 9 -3.86E-01 -3.02E-03 -1.34E-05 2.75E-06 -5.60E-08 4.95E-10 -2.06E-12 3.30E-15

[0215] See also Fig.12 , Fig.12 FIG. 1 shows the MTF field curve of the far-infrared optical system 100 provided in Example 6. Fig.12 The horizontal axis in is the Y-axis field of view, and its unit is degree; Fig.12 The vertical axis is the MTF value. Fig.12 The sagittal curve S1 and the meridional curve T1 of the MTF with 21lp / mm spatial frequency as the field of view changes, and the sagittal curve S2 and the meridional curve T2 of the MTF with 42lp / mm spatial frequency as the field of view changes are listed in the table. Fig.12 It can be seen that within the 1.0 field of view (48°), the MTF is greater than 0.26, and the imaging quality of the far-infrared optical system 100 is excellent.

[0216] After summarizing the various parameters of the far-infrared optical system 100 provided by the above six embodiments, the following Table 7 is obtained. Table 7 is mainly used to illustrate that the various conditions satisfied by the far-infrared optical system 100 provided by the present application are all verified and supported by experiments.

[0217] Table 7. Parameters of the far-infrared optical system 100 provided in various embodiments

[0218]

[0219]

[0220] The present application also provides a far-infrared optical lens (not shown), which includes an imaging detector (not shown) and the above-mentioned far-infrared optical system 100. The architecture of the far-infrared optical system 100 can be found above and will not be repeated here. The imaging detector is arranged on the image plane B of the far-infrared optical system 100, and the imaging detector includes but is not limited to CMOS (Complementary Metal Oxide Semiconductor, referred to as CMOS, complementary metal oxide semiconductor) and CCD (Charge Coupled Device, referred to as CCD, charge coupled device).

[0221] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the invention disclosed herein. The present application is intended to cover any modification, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary techniques in the art that are not disclosed in the present application. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present application are indicated by the appended claims.

Claims

1. A far-infrared optical system, characterized in that: The far-infrared optical system comprises, in order from the object side to the image side along the optical axis: a first refractive lens, a second refractive lens and a third refractive lens; the first refractive lens has a negative focal length, the object side surface of the first refractive lens is convex toward the object side, and the image side surface of the first refractive lens is convex toward the object side; the second refractive lens has a positive focal length, the object side surface of the second refractive lens is convex toward the image side, and the image side surface of the second refractive lens is convex toward the image side; the third refractive lens has a positive focal length, and the object side surface of the third refractive lens is convex toward the object side; Wherein, the far-infrared optical system further includes a first diffractive optical element arranged in the optical path of the far-infrared optical system and / or a second diffractive optical element arranged in the optical path of the far-infrared optical system.

2. The far-infrared optical system according to claim 1, characterized in that: The far-infrared optical system also includes a fourth refractive lens; the fourth refractive lens is located between the first refractive lens and the second refractive lens, the optical focal length of the fourth refractive lens is negative, the object side surface of the fourth refractive lens is convex to the object side, and the image side surface of the fourth refractive lens is convex to the object side.

3. The far-infrared optical system according to claim 1, characterized in that: The far-infrared optical system meets the following requirements: Among them, the f m is the focal length of the diffractive optical element. When the far-infrared optical system includes the first diffractive optical element and the second diffractive optical element, the f m is the focal length of the smaller one of the first diffractive optical element and the second diffractive optical element, and f is the effective focal length of the far-infrared optical system.

4. The far-infrared optical system according to claim 1 or 2, characterized in that: The far-infrared optical system meets the following requirements: 0.06mm -1 <n1×(|c1|+|c2|)<0.4mm -1 , wherein n1 is the refractive index of the first refractive lens, c1 is the curvature of the object side surface of the first refractive lens, and c2 is the curvature of the image side surface of the first refractive lens.

5. The far-infrared optical system according to claim 1 or 2, characterized in that: The far-infrared optical system meets the following requirements: Among them, the CT i is the center thickness of the i-th refractive lens, the ET i is the thickness of the i-th refractive lens corresponding to its maximum effective diameter, and i is a positive integer.

6. The far-infrared optical system according to claim 1 or 2, characterized in that: The far-infrared optical system meets the following requirements: Among them, Lb is the distance between the image side surface of the third refractive lens and the image plane of the far-infrared optical system on the optical axis, ImgH is the imaging area radius of the far-infrared optical system on the image plane corresponding to the maximum field of view angle, and TTL is the total optical length of the far-infrared optical system.

7. The far-infrared optical system according to claim 1 or 2, characterized in that: The far-infrared optical system meets the following requirements: Wherein, Lb is the distance between the image side surface of the third refractive lens and the image plane of the far-infrared optical system on the optical axis, and θ b It is the minimum value of the angle between the tangent line at any point on the surface of any refractive lens and the optical axis, and the TTL is the total optical length of the far-infrared optical system.

8. The far-infrared optical system according to claim 1 or 2, characterized in that: The far-infrared optical system meets the following requirements: Among them, the D i is the maximum effective diameter of the i-th refractive lens, the CT i is the central thickness of the i-th refractive lens, where i is a positive integer.

9. The far-infrared optical system according to claim 1 or 2, characterized in that: The far-infrared optical system meets the following requirements: Among them, the f i is the focal length of the i-th refractive lens, is the average value of the absolute values ​​of the focal lengths of all refractive lenses, and i is a positive integer.

10. The far-infrared optical system according to claim 1 or 2, characterized in that: The far-infrared optical system meets the following requirements: Among them, the D max is the largest of the maximum effective diameters of the refractive lenses, min It is the smallest of the maximum effective diameters of each refractive lens.

11. The far-infrared optical system according to claim 1 or 2, characterized in that: The far-infrared optical system further comprises an aperture, which is arranged between any two adjacent lenses; or, the aperture is arranged on the object side of the first refractive lens.

12. A far-infrared optical lens, characterized in that: The far-infrared optical lens comprises: an imaging detector and a far-infrared optical system as described in any one of claims 1 to 11; the imaging detector is arranged on the image plane of the far-infrared optical system.

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