Large-aperture far infrared optical system and large-aperture far infrared lens

Abstract

The invention discloses a large-aperture far infrared optical system and a large-aperture far infrared optical lens, the large-aperture far infrared optical system comprises a first aspheric lens, the object side surface and the image side surface of the first aspheric lens are convex to the object side; the focal power of the second aspheric lens is positive, and the object side surface and the image side surface of the second aspheric lens both protrude towards the image side; the focal power of the third aspheric lens is positive, and the object side surface and the image side surface of the third aspheric lens both protrude towards the image side; the diffractive optical element is arranged in a light path of the large-aperture far infrared optical system; wherein the first aspheric lens, the second aspheric lens and the third aspheric lens are sequentially arranged along an optical axis from an object side to an image side; the large-aperture far infrared optical system satisfies the following conditions: f2 < f3 < f1, and f1, f2 and f3 are focal lengths of the first aspherical lens, the second aspherical lens and the third aspherical lens respectively. The far infrared optical system provided by the invention is excellent in imaging quality, large in light incoming amount, high in resolution ratio, small in size and capable of meeting the miniaturization requirement.

Description

Technical Field

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

[0002] The design of far-infrared optical systems usually needs to be able to match the corresponding imaging detectors. At present, the resolutions of the more mature far-infrared imaging detectors on the market are 256×192, 640×512, 1280×1024, etc. The pixel sizes of the above imaging detectors are basically 12 microns. With the development of related technologies, the market demand for more detailed resolutions has gradually increased, and the existing imaging detectors with a pixel size of 12 microns basically cannot meet the resolution requirements. At the same time, imaging detectors with a pixel size of 8 microns have appeared on the market. Compared with imaging detectors with a pixel size of 12 microns, imaging detectors with a pixel size of 8 microns can distinguish more details, but imaging detectors with a pixel size of 8 microns also have higher requirements for the optical system. According to the Nyquist sampling theorem, the resolution of the far-infrared optical system matched with an imaging detector with a pixel size of 8 microns should reach 1000 / (8×2)=62.5lp / mm.

[0003] In the prior art, some far-infrared optical systems cannot match the 8-micron imaging detector, and some far-infrared optical systems also have problems such as small light input and large size. 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 solve at least one of the above problems.

[0005] According to one aspect of an embodiment of the present application, a large aperture far-infrared optical system is disclosed, and the large aperture far-infrared optical system comprises:

[0006] A first aspheric lens, whose object side surface is convex toward the object side and whose image side surface is convex toward the object side;

[0007] A second aspheric lens having positive optical power, an object side surface convex toward the image side, and an image side surface convex toward the image side;

[0008] a third aspheric lens having positive optical power, an object side surface convex toward the image side, and an image side surface convex toward the image side;

[0009] A diffractive optical element is arranged in the optical path of the large aperture far-infrared optical system;

[0010] Among them, the first aspheric lens, the second aspheric lens, and the third aspheric lens are arranged in sequence along the optical axis from the object side to the image side; the large aperture far-infrared optical system satisfies: |f2|<|f3|<|f1|, f1 is the focal length of the first aspheric lens, f2 is the focal length of the second aspheric lens, and f3 is the focal length of the third aspheric lens.

[0011] In some embodiments, the large aperture far-infrared optical system further comprises an aperture, and the aperture is arranged in the optical path of the large aperture far-infrared optical system;

[0012] The large aperture far-infrared optical system meets the following requirements: Wherein, f is the effective focal length of the large aperture far-infrared optical system, and D S is the aperture of the aperture, the TTL is the total optical length of the large aperture far-infrared optical system, and the FOV is the maximum field of view angle of the large aperture far-infrared optical system.

[0013] In some embodiments, the large aperture far-infrared optical system satisfies:

[0014] In some embodiments, the large aperture far-infrared optical system satisfies: Among them, the FOV is the maximum field angle of the large aperture far-infrared optical system, and f is the effective focal length of the large aperture far-infrared optical system.

[0015] In some embodiments, the large aperture far-infrared optical system further comprises an aperture, and the aperture is arranged in the optical path of the large aperture far-infrared optical system;

[0016] The large aperture far-infrared optical system meets the following requirements: Wherein, D1 is the maximum effective diameter of the first aspheric lens, D2 is the maximum effective diameter of the second aspheric lens, D3 is the maximum effective diameter of the third aspheric lens, and D S is the aperture of the aperture.

[0017] In some embodiments, the large aperture far-infrared optical system satisfies: Wherein, D1 is the maximum effective diameter of the first aspheric lens, D2 is the maximum effective diameter of the second aspheric lens, and D3 is the maximum effective diameter of the third aspheric lens.

[0018] In some embodiments, the large aperture far-infrared optical system satisfies: Among them, the Imgh is half of the diagonal length of the image formed by the large aperture far-infrared optical system at the maximum field of view angle, the n1 is the refractive index of the first aspheric lens, the FOV is the maximum field of view angle of the large aperture far-infrared optical system, the FNO is the aperture number of the large aperture far-infrared optical system, and the R1 is the radius of curvature of the object side of the first aspheric lens.

[0019] In some embodiments, the large aperture far-infrared optical system satisfies: Among them, the f 12 is the combined focal length of the first aspheric lens and the second aspheric lens, and the f 23 is the combined focal length of the second aspheric lens and the third aspheric lens.

[0020] In some embodiments, the diffractive optical element is a diffractive surface, and the diffractive surface is disposed on the object side surface of the third aspherical lens.

[0021] A second aspect of an embodiment of the present application provides a large aperture far-infrared optical lens, which includes: an imaging detector and a large aperture far-infrared optical system as described above; the imaging detector is arranged on the image plane of the large aperture far-infrared optical system.

[0022] The large aperture far-infrared optical system provided by the present application includes, in order from the object side to the image side along the optical axis: a first aspheric lens, a second aspheric lens and a third aspheric lens; the object side surface of the first aspheric lens is convex to the object side, and the image side surface of the first aspheric lens is convex to the object side; the optical focal length of the second aspheric lens is positive, the object side surface of the second aspheric lens is convex to the image side, and the image side surface of the second aspheric lens is convex to the image side; the optical focal length of the third aspheric lens is positive, the object side surface of the third aspheric lens is convex to the image side, and the image side surface of the third aspheric lens is convex to the image side; the large aperture far-infrared optical system also includes a diffractive optical element, at least one diffractive optical element is arranged in the optical path of the large aperture far-infrared optical system; wherein the large aperture far-infrared optical system satisfies: |f2|<|f3|<|f1|, f1 is the focal length of the first aspheric lens, f2 is the focal length of the second aspheric lens, and f3 is the focal length of the third aspheric lens. The large aperture far-infrared optical system provided by the present application has excellent imaging quality, a large amount of light entering, and a high resolution, and can be adapted to an imaging detector with a pixel size of 8 microns. The large aperture far-infrared optical system has a small number of lenses, which can ensure that the large aperture far-infrared optical system has a small volume and can meet the needs of miniaturization. In addition, the large aperture far-infrared optical system introduces a diffractive optical element, which can correct the system chromatic aberration while improving the system's design freedom. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] 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.

[0024] Figure 1 A schematic diagram of the architecture layout of a large aperture far-infrared optical system in an embodiment of the present application is shown.

[0025] Figure 2 A phase distribution diagram of a diffractive optical element of a large aperture far-infrared optical system in an embodiment of the present application is shown.

[0026] Figure 3 The MTF field of view curve of a large aperture far-infrared optical system in one embodiment of the present application is shown.

[0027] Figure 4 A point diagram of a large aperture far-infrared optical system in one embodiment of the present application is shown.

[0028] Figure 5 A field curvature diagram of a large aperture far-infrared optical system in an embodiment of the present application is shown.

[0029] Figure 6 A distortion diagram of a large aperture far-infrared optical system in one embodiment of the present application is shown.

[0030] Figure 7 A relative illumination diagram of a large aperture far-infrared optical system in one embodiment of the present application is shown.

[0031] Figure 8 A vertical axis chromatic aberration diagram of a large aperture far-infrared optical system in one embodiment of the present application is shown.

[0032] Fig. 9 A schematic diagram of the architecture layout of a large aperture far-infrared optical system in an embodiment of the present application is shown.

[0033] Fig.10 A phase distribution diagram of a diffractive optical element of a large aperture far-infrared optical system in an embodiment of the present application is shown.

[0034] Fig.11 The MTF field of view curve of a large aperture far-infrared optical system in one embodiment of the present application is shown.

[0035] Fig.12 A point diagram of a large aperture far-infrared optical system in one embodiment of the present application is shown.

[0036] Fig.13 A field curvature diagram of a large aperture far-infrared optical system in an embodiment of the present application is shown.

[0037] Fig.14 A distortion diagram of a large aperture far-infrared optical system in one embodiment of the present application is shown.

[0038] Fig.15 A relative illumination diagram of a large aperture far-infrared optical system in one embodiment of the present application is shown.

[0039] Fig.16 A vertical axis chromatic aberration diagram of a large aperture far-infrared optical system in one embodiment of the present application is shown.

[0040] Fig.17 A schematic diagram of the architecture layout of a large aperture far-infrared optical system in an embodiment of the present application is shown.

[0041] Fig.18 A phase distribution diagram of a diffractive optical element of a large aperture far-infrared optical system in an embodiment of the present application is shown.

[0042] Fig.19 The MTF field of view curve of a large aperture far-infrared optical system in one embodiment of the present application is shown.

[0043] Fig. 20 A point diagram of a large aperture far-infrared optical system in one embodiment of the present application is shown.

[0044] Fig.21 A field curvature diagram of a large aperture far-infrared optical system in an embodiment of the present application is shown.

[0045] Fig. 22 A distortion diagram of a large aperture far-infrared optical system in one embodiment of the present application is shown.

[0046] Fig.23 A relative illumination diagram of a large aperture far-infrared optical system in one embodiment of the present application is shown.

[0047] Fig.24 A vertical axis chromatic aberration diagram of a large aperture far-infrared optical system in one embodiment of the present application is shown.

[0048] Fig.25 A schematic diagram of the architecture layout of a large aperture far-infrared optical system in an embodiment of the present application is shown.

[0049] Fig.26 A phase distribution diagram of a diffractive optical element of a large aperture far-infrared optical system in an embodiment of the present application is shown.

[0050] Fig. 27 The MTF field of view curve of a large aperture far-infrared optical system in one embodiment of the present application is shown.

[0051] Fig.28 A point diagram of a large aperture far-infrared optical system in one embodiment of the present application is shown.

[0052] Fig.29A field curvature diagram of a large aperture far-infrared optical system in an embodiment of the present application is shown.

[0053] Fig.30 A distortion diagram of a large aperture far-infrared optical system in one embodiment of the present application is shown.

[0054] Fig.31 A relative illumination diagram of a large aperture far-infrared optical system in one embodiment of the present application is shown.

[0055] Fig.32 A vertical axis chromatic aberration diagram of a large aperture far-infrared optical system in one embodiment of the present application is shown.

[0056] Fig.33 A schematic diagram of the architecture layout of a large aperture far-infrared optical system in an embodiment of the present application is shown.

[0057] Fig.34 A phase distribution diagram of a diffractive optical element of a large aperture far-infrared optical system in an embodiment of the present application is shown.

[0058] Fig.35 The MTF field of view curve of a large aperture far-infrared optical system in one embodiment of the present application is shown.

[0059] Fig.36 A point diagram of a large aperture far-infrared optical system in one embodiment of the present application is shown.

[0060] Fig.37 A field curvature diagram of a large aperture far-infrared optical system in an embodiment of the present application is shown.

[0061] Fig.38 A distortion diagram of a large aperture far-infrared optical system in one embodiment of the present application is shown.

[0062] Fig.39 A relative illumination diagram of a large aperture far-infrared optical system in one embodiment of the present application is shown.

[0063] Fig.40 A vertical axis chromatic aberration diagram of a large aperture far-infrared optical system in one embodiment of the present application is shown.

[0064] Fig.41 A schematic diagram of the architecture layout of a large aperture far-infrared optical system in an embodiment of the present application is shown.

[0065] Fig.42 A phase distribution diagram of a diffractive optical element of a large aperture far-infrared optical system in an embodiment of the present application is shown.

[0066] Fig.43 The MTF field of view curve of a large aperture far-infrared optical system in one embodiment of the present application is shown.

[0067] Fig.44 A point diagram of a large aperture far-infrared optical system in one embodiment of the present application is shown.

[0068] Fig.45 A field curvature diagram of a large aperture far-infrared optical system in an embodiment of the present application is shown.

[0069] Fig.46 A distortion diagram of a large aperture far-infrared optical system in one embodiment of the present application is shown.

[0070] Fig.47 A relative illumination diagram of a large aperture far-infrared optical system in one embodiment of the present application is shown.

[0071] Fig.48 A vertical axis chromatic aberration diagram of a large aperture far-infrared optical system in one embodiment of the present application is shown.

[0072] Reference numerals

[0073] 100. Large aperture far-infrared optical system;

[0074] 10. A first aspheric lens;

[0075] 20. A second aspheric lens;

[0076] 30. A third aspheric lens;

[0077] 40. Diffractive optical elements;

[0078] 50. Aperture;

[0079] 60. Protective glass;

[0080] 70. Object surface;

[0081] 80. Image plane;

[0082] 90. Optical axis. DETAILED DESCRIPTION

[0083] 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.

[0084] 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.

[0085] See also Figure 1 , Figure 1 A schematic diagram of the architectural layout of a large aperture far-infrared optical system in an embodiment of the present application is shown, wherein the optical axis is the center line of the light beam, and the direction from the object plane to the image plane along the optical axis is consistent with the direction from the object side to the image side along the optical axis.

[0086] The large aperture far-infrared optical system 100 comprises a first aspheric lens 10, a second aspheric lens 20, a third aspheric lens 30 and a diffractive optical element 40, wherein the first aspheric lens 10, the second aspheric lens 20 and the third aspheric lens 30 are sequentially arranged along the optical axis 90 from the object plane 70 to the image plane 80. The diffractive optical element 40 is arranged in the optical path of the large aperture far-infrared optical system 100, for example, between any two adjacent lenses, or, arranged on the surface of any one or more lenses.

[0087] The object side surface of the first aspheric lens 10 is convex toward the object side, and the image side surface of the first aspheric lens 10 is convex toward the object side. The optical power of the first aspheric lens 10 may be positive or negative. Specifically, in some embodiments, the optical power of the first aspheric lens 10 is positive; in some embodiments, the optical power of the first aspheric lens 10 is negative.

[0088] The optical power of the second aspheric lens 20 is positive, the object side surface of the second aspheric lens 20 is convex toward the image side, and the image side surface of the second aspheric lens 20 is convex toward the image side.

[0089] The third aspheric lens 30 has positive refractive power, the object side surface of the third aspheric lens 30 is convex toward the image side, and the image side surface of the third aspheric lens 30 is convex toward the image side.

[0090] At least one diffractive optical element 40 is provided, and at least one diffractive optical element 40 is arranged in the optical path of the large aperture far-infrared optical system 100. The diffractive optical element 40 has negative dispersion and is used in combination with a traditional refractive lens (a first aspheric lens 10, a second aspheric lens 20, and a third aspheric lens 30) to effectively correct the chromatic aberration of the large aperture far-infrared optical system 100.

[0091] The large aperture far-infrared optical system 100 satisfies conditional formula 1: |f2|<|f3|<|f1|, wherein f1 is the focal length of the first aspheric lens 10, f2 is the focal length of the second aspheric lens 20, and f3 is the focal length of the third aspheric lens 30. The dimensions of f1, f2, and f3 are the same, and are all length units, such as millimeters.

[0092] The optical power of the large aperture far-infrared optical system 100 can be reasonably allocated by conditional expression 1, so as to ensure that the large aperture far-infrared optical system 100 has a lower tolerance sensitivity while having excellent imaging quality.

[0093] The large aperture far-infrared optical system 100 provided by the present application has excellent imaging quality, a large amount of light entering, and a high resolution, and can be adapted to an imaging detector with a pixel size of 8 microns. The large aperture far-infrared optical system 100 has a small number of lenses, which can ensure that the large aperture far-infrared optical system 100 has a small volume and can meet the needs of miniaturization. In addition, the large aperture far-infrared optical system 100 introduces a diffractive optical element 40, which can improve the design freedom of the system while correcting the chromatic aberration of the system.

[0094] In some embodiments, the large aperture far-infrared optical system 100 includes only one diffractive optical element 40, and the diffractive optical element 40 may be disposed at any of the following positions:

[0095] A: The diffractive optical element 40 is disposed on the object side of any lens;

[0096] B: The diffractive optical element 40 is disposed on the image side of any lens;

[0097] C: The diffractive optical element 40 is disposed between any two adjacent lenses;

[0098] D: The diffractive optical element 40 is disposed on the object side of the first aspheric lens 10;

[0099] E: The diffractive optical element 40 is provided on the image side of the third aspherical lens 30 .

[0100] In some embodiments, when the large aperture far-infrared optical system 100 includes at least two diffractive optical elements 40, the positions at which the diffractive optical elements are arranged are a combination of the above-mentioned A, B, C, D, and E situations. For example, when the large aperture far-infrared optical system 100 includes two diffractive optical elements 40, the positions at which the two diffractive optical elements 40 are arranged can be a combination of any two of A, B, C, D, and E. When the large aperture far-infrared optical system 100 includes three diffractive optical elements 40, the positions at which the three diffractive optical elements 40 are arranged can be a combination of any three of A, B, C, D, and E.

[0101] For the above-mentioned diffractive optical element 40, when the diffractive optical element 40 is disposed on the surface of the lens, the diffractive optical element 40 can be realized by a diffractive surface, which is a special optical surface that introduces a tiny periodic or non-periodic structure on its surface to cause the incident light to diffract, thereby achieving precise control of the shape, direction and intensity distribution of the light beam. When the diffractive optical element 40 is disposed between any two adjacent lenses, or when the diffractive optical element 40 is disposed on the object side of the first aspheric lens 10, or when the diffractive optical element 40 is disposed on the image side of the third aspheric lens 30, the diffractive optical element 40 can be a super lens or a diffractive surface integrated on a flat glass.

[0102] In some embodiments, the diffractive optical element 40 is a diffractive surface, and the object side surface of the first aspheric lens 10, the image side surface of the first aspheric lens 10, the object side surface of the second aspheric lens 20, the image side surface of the second aspheric lens 20, the object side surface of the third aspheric lens 30 and the image side surface of the third aspheric lens 30 are all target surfaces on which the diffractive optical element 40 can be set. At least one target surface is provided with a diffractive surface. The diffractive surface has the advantages of high diffraction efficiency and good dispersion. Introducing a diffractive surface in the large aperture far-infrared optical system 100 can improve the design freedom.

[0103] Further, in some embodiments, the diffractive optical element 40 is a diffractive surface, and the diffractive surface is disposed on the object side of the third aspheric lens 30. Compared with disposing the diffractive surface at other positions, when the diffractive surface is disposed on the object side of the third aspheric lens 30, the large aperture far-infrared optical system 100 has better imaging quality. Compared with disposing multiple diffractive surfaces in the large aperture far-infrared optical system 100, when the large aperture far-infrared optical system 100 is only provided with one diffractive surface, and the diffractive surface is disposed on the object side of the third aspheric lens 30, the large aperture far-infrared optical system 100 has a higher transmittance.

[0104] In some embodiments, the large aperture far-infrared optical system 100 satisfies conditional formula 2: Wherein, f1 is the focal length of the first aspheric lens 10, f2 is the focal length of the second aspheric lens 20, and f3 is the focal length of the third aspheric lens 30. f1, f2, and f3 have the same dimension, which is a length unit, such as millimeters.

[0105] Conditional formula 2 indicates the focal power distribution relationship of the large aperture far-infrared optical system 100. Meeting conditional formula 2 is beneficial to the aberration correction of the large aperture far-infrared optical system 100, so that the large aperture far-infrared optical system 100 has excellent imaging quality and is beneficial to the balance of aberrations. Moreover, meeting conditional formula 2 can reduce the sensitivity of the assembly tolerance of the large aperture far-infrared optical system 100 and improve the assembly yield of the lens corresponding to the large aperture far-infrared optical system 100.

[0106] In some embodiments, the large aperture far-infrared optical system 100 satisfies conditional formula 3: Wherein, FOV (Field of View, FOV for short) is the maximum field angle of the large aperture far-infrared optical system 100, and the unit of FOV is degree. f is the effective focal length of the large aperture far-infrared optical system 100, and the dimension of f is the unit of length, such as millimeter.

[0107] Conditional formula five can ensure that the imaging clarity of the large aperture far-infrared optical system 100 can meet the needs of an imaging detector with a pixel size of 8 microns. At the same time, conditional formula five can also ensure that the large aperture far-infrared optical system 100 can collect larger field of view information, which can improve the efficiency of the large aperture far-infrared optical system 100 in receiving information.

[0108] In some embodiments, the large aperture far-infrared optical system 100 satisfies conditional formula 4: Wherein, D1 is the maximum effective diameter of the first aspheric lens 10, D2 is the maximum effective diameter of the second aspheric lens 20, and D3 is the maximum effective diameter of the third aspheric lens 30. In the present application, the maximum effective diameter of a lens is the larger of the maximum effective diameter of the object side surface and the maximum effective diameter of the image side surface of the corresponding lens. For example, the maximum effective diameter D1 of the first aspheric lens 10 is the larger of the maximum effective diameter of the object side surface of the first aspheric lens 10 and the maximum effective diameter of the image side surface of the first aspheric lens 10. The maximum effective diameter of the object side surface of the lens refers to the diameter of the maximum light-transmitting area of ​​the object side surface of the lens, and the same is true for the maximum effective diameter of the image side surface of the lens. f1 is the focal length of the first aspheric lens 10, f2 is the focal length of the second aspheric lens 20, and f3 is the focal length of the third aspheric lens 30. The dimensions of D1, D2, D3, f1, f2, and f3 are the same, and are all length units, such as millimeters.

[0109] Conditional formula 4 can ensure that the propagation path of light in the large aperture far-infrared optical system 100 is relatively smooth, which can reduce the overall tolerance sensitivity of the large aperture far-infrared optical system 100 and improve the assembly yield of the large aperture far-infrared optical system 100. In addition, conditional formula 4 can ensure the imaging performance of the large aperture far-infrared optical system 100.

[0110] In some embodiments, the large aperture far-infrared optical system 100 satisfies conditional formula 5: Wherein, Imgh is half of the diagonal length of the image formed by the large aperture far-infrared optical system 100 at the maximum field of view. n1 is the refractive index of the first aspheric lens 10. In the present application, n1 is the refractive index at a wavelength of 10.6 microns. FOV is the maximum field of view of the large aperture far-infrared optical system 100. The unit of FOV is an angle unit, such as degree. FNO is the aperture number of the large aperture far-infrared optical system 100, that is, FNO is the F number of the large aperture far-infrared optical system 100. R1 is the radius of curvature of the object side of the first aspheric lens 10. Imgh and R1 have the same dimension, both are length units, such as millimeters.

[0111] Conditional formula 5 indicates the system parameter range when the large aperture far-infrared optical system 100 has excellent imaging quality when paired with an imaging detector with a pixel size of 8 microns. It is worth mentioning that the pixel size of the imaging detector adapted to the large aperture far-infrared optical system 100 includes but is not limited to 8 microns, and the number of pixels of the imaging detector adapted to the large aperture far-infrared optical system 100 includes but is not limited to 640*512.

[0112] In some embodiments, the large aperture far-infrared optical system 100 satisfies conditional formula 6: Among them, f 12 is the combined focal length of the first aspheric lens 10 and the second aspheric lens 20, f 23 is the combined focal length of the second aspheric lens 20 and the third aspheric lens 30. 12 、f 23 have the same dimension, which is a unit of length, such as millimeter.

[0113] Conditional expression 6 is beneficial to the aberration correction of the large aperture far-infrared optical system 100, and can ensure that the large aperture far-infrared optical system 100 has excellent imaging quality.

[0114] In some embodiments, the large aperture far-infrared optical system 100 satisfies conditional equation 7: Wherein, TTL (Total Track Length, TTL for short) is the total optical length of the large aperture far-infrared optical system 100, and f is the effective focal length of the large aperture far-infrared optical system 100. TTL and f have the same dimension, both of which are length units, such as millimeters.

[0115] Conditional expression 7 can ensure that the large aperture far-infrared optical system 100 has a smaller total optical length, and further ensure that the large aperture far-infrared optical system 100 has a smaller volume, so that the large aperture far-infrared optical system 100 has the advantage of miniaturization.

[0116] In some embodiments, the large aperture far-infrared optical system 100 satisfies conditional formula eight: Wherein, BFL (Back focal length, referred to as BFL) is the optical back focal length of the large aperture far-infrared optical system 100, and f is the effective focal length of the large aperture far-infrared optical system 100. BFL and f have the same dimension, both of which are length units, such as millimeters.

[0117] If the optical back focus is too large, the total optical length will be too large, which will in turn cause the volume of the large aperture far-infrared optical system 100 to be too large; if the optical back focus is too small, the space between the third aspherical lens 30 and the image plane 80 will be too small, which will be unfavorable for the installation of components such as the shutter. Conditional formula three can ensure that the large aperture far-infrared optical system 100 has a suitable optical back focus, so that the large aperture far-infrared optical system 100 has a small volume and a suitable optical back focus, so that the large aperture far-infrared optical system 100 has enough space for installing components such as the shutter, and collisions between components can be avoided.

[0118] In some embodiments, the large aperture far-infrared optical system 100 satisfies conditional formula 9: Wherein, D1 is the maximum effective diameter of the first aspheric lens 10, and D3 is the maximum effective diameter of the third aspheric lens 30. D1 and D3 have the same dimension, both of which are length units, such as millimeters.

[0119] The lower limit of conditional formula 9 can ensure that the large aperture far-infrared optical system 100 has a small volume, thereby ensuring that the aperture of the large aperture far-infrared optical system 100 is not too large. The lower limit of conditional formula 9 can ensure that the large aperture far-infrared optical system 100 has sufficient relative illumination.

[0120] In some embodiments, the large aperture far-infrared optical system 100 satisfies Conditional Formula 10: Among them, R 31 is the curvature radius of the object side surface of the third aspheric lens 30, SAG 31 is the sagittal height at the maximum effective radius of the object side of the third aspherical lens 30. In the present application, the sagittal height at the maximum effective radius is the sagittal height at the effective radius of the corresponding surface and the distance from the center of the corresponding surface on the optical axis 90 is equal to the sagittal height of the corresponding surface, that is, SAG 31 R is the sagittal height at the object side surface of the third aspherical lens 30, and the distance from the center of the object side surface of the third aspherical lens 30 on the optical axis 90 is equal to the effective radius of the object side surface of the third aspherical lens 30. 32 is the curvature radius of the image side surface of the third aspherical lens 30, SAG 32 is the sag of the image side surface of the third aspheric lens 30 at the maximum effective radius, that is, SAG 31R is the sagittal height at the image side surface of the third aspheric lens 30, and the distance from the center of the image side surface of the third aspheric lens 30 on the optical axis 90 is equal to the effective radius of the image side surface of the third aspheric lens 30. 31 、SAG 31 , R 32 、SAG 32 have the same dimension, which is a unit of length, such as millimeter.

[0121] Conditional expression 6 can effectively control the spherical aberration and off-axis coma of the large aperture far-infrared optical system 100. Meanwhile, conditional expression 5 can also control the surface shape of the third aspherical lens 30, making the surface shape of the third aspherical lens 30 more reasonable and easier to process.

[0122] In some embodiments, the large aperture far-infrared optical system 100 satisfies conditional formula 11: Wherein, ΣCT is equal to the sum of the center thickness of the first aspheric lens 10, the center thickness of the second aspheric lens 20, and the center thickness of the third aspheric lens 30, and BFL is the optical back focus of the large aperture far-infrared optical system 100. 13 is the distance between the object side surface of the first aspheric lens 10 and the image side surface of the third aspheric lens 30 on the optical axis 90, and TTL is the total optical length of the large aperture far-infrared optical system 100. ΣCT, BFL, C 13 , TTL have the same dimension, both are length units, such as millimeters.

[0123] The upper limit of the conditional formula 11 is used to constrain the thickness of the first aspheric lens 10, the second aspheric lens 20, and the third aspheric lens 30, so as to reduce the amount of lens material used, thereby reducing the cost of the large aperture far-infrared optical system 100. The lower limit of the conditional formula 11 can ensure that the large aperture far-infrared optical system 100 has a smaller total optical length, thereby ensuring that the large aperture far-infrared optical system 100 has a smaller volume.

[0124] The large aperture far-infrared optical system 100 further includes an aperture 50, which is used to control the amount of light entering the large aperture far-infrared optical system 100, thereby ensuring that the large aperture far-infrared optical system 100 can work effectively and generate high-quality images.

[0125] In some embodiments, the aperture 50 is disposed on the object side of the first aspheric lens 10. Specifically, the position where the aperture 50 is disposed satisfies any of the following conditions:

[0126] (1) The aperture 50 is disposed on the object side of the first aspheric lens 10, and the aperture 50 is spaced apart from the first aspheric lens 10;

[0127] (2) The aperture stop 50 is provided on the object side of the first aspherical lens 10 , and the aperture stop 50 is provided on the object-side surface of the first aspherical lens 10 .

[0128] In some embodiments, the aperture 50 is disposed between any two adjacent lenses. Specifically, the position where the aperture 50 is disposed satisfies any of the following conditions:

[0129] (1) The aperture 50 is located between the first aspheric lens 10 and the second aspheric lens 20, and the aperture 50 is arranged on the image side surface of the first aspheric lens 10;

[0130] (2) The aperture 50 is located between the first aspheric lens 10 and the second aspheric lens 20, and the aperture 50 is spaced apart from the first aspheric lens 10 and the second aspheric lens 20;

[0131] (3) The aperture 50 is located between the first aspheric lens 10 and the second aspheric lens 20, and the aperture 50 is arranged on the object side surface of the second aspheric lens 20;

[0132] (4) The aperture 50 is located between the second aspheric lens 20 and the third aspheric lens 30, and the aperture 50 is arranged on the image side surface of the second aspheric lens 20;

[0133] (5) The aperture 50 is located between the second aspheric lens 20 and the third aspheric lens 30, and the aperture 50 is spaced apart from the second aspheric lens 20 and the third aspheric lens 30;

[0134] (6) The aperture stop 50 is located between the second aspherical lens 20 and the third aspherical lens 30 , and the aperture stop 50 is provided on the object side surface of the third aspherical lens 30 .

[0135] Furthermore, in some embodiments, the aperture 50 is located between the first aspheric lens 10 and the second aspheric lens 20. Compared with setting the aperture 50 at other positions, when the aperture 50 is set between the first aspheric lens 10 and the second aspheric lens 20, the large aperture far-infrared optical system 100 has better imaging quality.

[0136] In some embodiments, the aperture 50 is disposed in the optical path of the large aperture far-infrared optical system 100, and the large aperture far-infrared optical system 100 satisfies conditional formula 12: Wherein, f is the effective focal length of the large aperture far-infrared optical system 100, D S is the aperture of the aperture 50, and TTL is the total optical length of the large aperture far-infrared optical system 100. f, D S , TTL have the same dimension, both are length units, such as millimeters. FOV is the maximum field of view of the large aperture far-infrared optical system 100, and the unit of FOV is degree.

[0137] The lower limit of conditional formula 12 can ensure that the large aperture far infrared optical system 100 has sufficient light intake, improve light energy utilization, and obtain more details of the photographed object. The upper limit of conditional formula 12 can ensure that the large aperture far infrared optical system 100 has a smaller volume to meet the demand for miniaturization.

[0138] In some embodiments, the aperture 50 is disposed in the optical path of the large aperture far-infrared optical system 100, and the large aperture far-infrared optical system 100 satisfies conditional formula 13: Wherein, D1 is the maximum effective diameter of the first aspheric lens 10, D2 is the maximum effective diameter of the second aspheric lens 20, D3 is the maximum effective diameter of the third aspheric lens 30, and D S The diameter of the aperture 50. D1, D2, D3, D S have the same dimension, which is a unit of length, such as millimeter.

[0139] The upper limit of conditional formula 13 is used to control the overall aperture of the large aperture far-infrared optical system 100, which is conducive to the miniaturization of the large aperture far-infrared optical system 100. Moreover, when the large aperture far-infrared optical system 100 has a reasonable aperture, the apertures of the first aspheric lens 10, the second aspheric lens 20, and the third aspheric lens 30 are not too large, which can reduce the material usage of the first aspheric lens 10, the second aspheric lens 20, and the third aspheric lens 30, thereby reducing the cost of the large aperture far-infrared optical system 100. The lower limit of conditional formula 13 can avoid the relative illumination of the large aperture far-infrared optical system 100 being too low, that is, the lower limit of conditional formula 13 can ensure the relative illumination threshold of the far-infrared optical system.

[0140] In some embodiments, the large aperture far-infrared optical system 100 further includes a protective glass 60, which is located on the image side of the third aspheric lens 30. The protective glass 60 is used to protect the imaging detector disposed on the image plane 80 to reduce the probability of damage to the imaging detector.

[0141] The large aperture far-infrared optical system 100 provided in this application has the following benefits:

[0142] (1) Effective focal length: 6.1 mm ± 5%

[0143] (2) F number: 0.9-1.0;

[0144] (3) The absolute value of distortion is ≤12%;

[0145] (4) Relative illumination>70%;

[0146] (5) Total optical length (TTL) < 14 mm;

[0147] (6) optical back focus (BFL) > 5.05 mm;

[0148] (7) Adaptable to imaging detectors with a pixel size of 8 microns;

[0149] The present application exemplarily provides six large aperture far-infrared optical systems 100 that meet usage requirements in six embodiments. Next, the large aperture far-infrared optical systems 100 provided in the various embodiments of the present application are introduced in detail.

[0150] Example 1

[0151] Figure 1 FIG. 1 shows a schematic diagram of the architecture layout of the large aperture far-infrared optical system 100 provided in Example 1. Figure 1 The medium-large aperture far-infrared optical system 100 includes, along the optical axis 90, from the object plane 70 to the image plane 80, a first aspheric lens 10, an aperture 50, a second aspheric lens 20, a diffractive optical element 40, a third aspheric lens 30 and a protective glass 60, wherein the diffractive optical element 40 is a diffractive surface, and the diffractive surface is arranged on the object side of the third aspheric lens 30. Some parameters of the large aperture far-infrared optical system 100 provided in Example 1 are shown in Table 1-1.

[0152] Table 1-1. Partial parameters of the large aperture far-infrared optical system 100 provided in Example 1

[0153] Optical indicators data Effective focal length 6.104mm F-number 0.9 distortion -11.64％ Relative Illuminance >74.8％ Total optical length (TTL) 13.056mm Optical Back Focus (BFL) 5.433mm Maximum field of view FOV (2ω) 62.994° Working band 8μm-12μm

[0154] As can be seen from Table 1-1, the total optical length of the large aperture far-infrared optical system 100 is relatively short, only 13.06 mm, so the volume of the large aperture far-infrared optical system 100 provided in Example 1 is relatively small. The F number of the large aperture far-infrared optical system 100 is 0.9, and the large aperture far-infrared optical system 100 has a large amount of light input, thereby ensuring excellent imaging quality.

[0155] Along the direction of the optical axis 90 from the object plane 70 to the image plane 80, starting from the object plane 70, each surface in the large aperture far-infrared optical system 100 is numbered, and the parameters of each surface are summarized to obtain the following Table 1-2.

[0156] Table 1-2. Parameters of various surfaces in the large aperture far-infrared optical system 100 provided in Example 1

[0157] Surface number Surface type Curvature radius (mm) Thickness(mm) Material 0 flat unlimited unlimited - 1 even aspherical surface 4.242 0.900 Chalcogenide glass 2 even aspherical surface 3.665 1.416 - 3 Aperture unlimited 0.419 - 4 even aspherical surface -50.483 2.000 Chalcogenide glass 5 even aspherical surface -9.693 0.670 - 6 even aspherical surface -8.076 2.218 Chalcogenide glass 7 even aspherical surface -7.195 4.708 - 8 flat unlimited 0.625 silicon 9 flat unlimited 0.100 - 10 flat unlimited - -

[0158] For each surface in Table 1-2, surface 0 is the object surface 70, surface 1 is the object side surface of the first aspheric lens 10, and surface 2 is the image side surface of the first aspheric lens 10. Surface 3 is the aperture 50. Surface 4 is the object side surface of the second aspheric lens 20, and surface 5 is the image side surface of the second aspheric lens 20. Surface 6 is the object side surface of the third aspheric lens 30, and surface 7 is the image side surface of the third aspheric lens 30 and the diffraction surface is provided on this surface. Surface 8 is the object side surface of the protective glass 60, surface 9 is the image side surface of the protective glass 60, and surface 10 is the image surface 80.

[0159] As can be seen from Table 1-2, surface 1 is an even aspheric surface, the radius of curvature of surface 1 is 4.242 mm, the distance between surface 1 and surface 2 is 0.900 mm, and the material between surface 1 and surface 2 is chalcogenide glass. Surface 2 is an even aspheric surface, the radius of curvature of surface 2 is 3.665 mm, the distance between surface 2 and surface 3 is 1.416 mm, and the material between surface 2 and surface 3 is air. Surface 3 is a plane, the radius of curvature of surface 3 is infinite, the distance between surface 3 and surface 4 is 0.419 mm, and the material between surface 3 and surface 4 is air. Surface 4 is an even aspheric surface, the radius of curvature of surface 4 is -50.483 mm, the distance between surface 4 and surface 5 is 2.000 mm, and the material between surface 4 and surface 5 is chalcogenide glass. Surface 5 is an even aspheric surface, the radius of curvature of surface 5 is -9.693 mm, the distance between surface 5 and surface 6 is 0.670 mm, and the material between surface 5 and surface 6 is air. Surface 6 is an even aspheric surface, the radius of curvature of surface 6 is -8.076 mm, the distance between surface 6 and surface 7 is 2.218 mm, and the material between surface 6 and surface 7 is chalcogenide glass. Surface 7 is an even aspheric surface, the radius of curvature of surface 7 is -7.195 mm, the distance between surface 7 and surface 8 is 4.708 mm, and the material between surface 7 and surface 8 is air. Surface 8 is a plane, the radius of curvature of surface 8 is infinite, the distance between surface 8 and surface 9 is 0.625 mm, and the material between surface 8 and surface 9 is silicon. Surface 9 is a plane, the radius of curvature of surface 9 is infinite, the distance between surface 9 and surface 10 is 0.100 mm, and the material between surface 9 and surface 10 is air.

[0160] 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:

[0161]

[0162] 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 90 degrees; 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 6 and surface 7 can be obtained from Table 1-3.

[0163] Table 1-3. Coefficients of various orders of even-order aspheric surfaces in the large aperture far-infrared optical system 100 provided in Example 1

[0164] surface k A B C D E 1 -5.36E-02 5.88E-04 -2.00E-04 3.42E-06 -1.10E-06 2.30E-09 2 -3.39E-01 1.58E-03 -7.26E-05 -4.78E-05 1.30E-06 -5.13E-08 4 -9.90E+01 -1.26E-03 3.96E-05 -2.93E-05 3.30E-06 -1.98E-07 5 -1.36E+00 6.82E-05 -1.24E-04 2.36E-06 7.79E-08 -1.05E-08 6 2.36E+00 1.81E-03 -1.79E-04 7.25E-06 -5.48E-08 1.02E-08 7 -6.72E+00 -1.65E-03 1.85E-05 -1.31E-06 5.96E-08 -1.67E-09

[0165] Refer to Table 1-3. For surface 1, k is -5.36E-02, A is 5.88E-04, B is -2.00E-04, C is 3.42E-06, D is -1.10E-06, and E is 2.30E-09. The coefficients of the even-order aspheric surfaces of surface 2, surface 4, surface 5, surface 6, and surface 7 are not described here one by one.

[0166] The diffraction surface is set on surface 6, and the phase expression of the diffraction surface is Where, ρ = r / r0, r is the radius of the diffraction surface, r0 is the normalized radius of the diffraction surface, A i is the phase coefficient of the diffraction surface, and N is the number of terms in the polynomial. The coefficients of the diffraction surface can be found in Table 1-4.

[0167] Table 1-4. Coefficients of diffraction surface in the large aperture far-infrared optical system 100 provided in Example 1

[0168] surface Face type Normalized radius A1 A2 A3 A4 6 Binary diffraction surface 3.6mm -1.07E+01 -5.93E+00 -6.47E+01 3.05E+02

[0169] See also Figure 2 , Figure 2 FIG. 1 shows a phase distribution diagram of the diffraction surface in the large aperture far-infrared optical system 100 provided in Example 1. Figure 2 The horizontal axis represents the distance from the center of the diffraction surface. Figure 2 The vertical axis represents the phase. Since the phase is a periodic function about 2π, there is a relationship (n is an integer), therefore, Figure 2 The phase of the diffraction surface in Example 1 is modulo 2π to achieve normalization processing to meet the needs of actual processing of the diffraction surface.

[0170] See also Figure 3 , Figure 3 The MTF (Modulation Transfer Function, MTF for short) field of view curve of the large aperture far-infrared optical system 100 provided in Example 1 is shown. Figure 3 The horizontal axis in is the image height, that is, the horizontal axis measures the field of view with the image height, and the unit of the horizontal axis is millimeters; Figure 3 The vertical axis is the MTF value. Figure 3 The MTF of 10lp / mm spatial frequency is listed as the sagittal curve S1 and the meridional curve T1 of the field of view, the MTF of 21lp / mm spatial frequency is listed as the sagittal curve S2 and the meridional curve T2 of the field of view, the MTF of 42lp / mm spatial frequency is listed as the sagittal curve S3 and the meridional curve T3 of the field of view, and the MTF of 62.5lp / mm spatial frequency is listed as the sagittal curve S4 and the meridional curve T4 of the field of view. Figure 3 It can be seen that at a spatial frequency of 62.5lp / mm, the MTF is greater than 0.17 in the entire field of view, and the large aperture far-infrared optical system 100 has excellent imaging quality.

[0171] See also Figure 4 , Figure 4 The point diagram of the large aperture far-infrared optical system 100 provided in Example 1 is shown. Figure 4 It can be seen that the maximum size of the spot diagram in the entire field of view is less than 2 pixels (16 micrometers), so the light is concentrated and the large aperture far-infrared optical system 100 provided in Example 1 has a sharp imaging effect.

[0172] See also Figure 5 , Figure 5 1 shows a field curvature diagram of the large aperture far-infrared optical system 100 provided in Example 1, Figure 5 The central horizontal axis is the field curvature, which is in millimeters; Figure 5 The vertical axis is the Y-axis field of view, and its unit is degree. Figure 5 S1 is the field curvature of far-infrared light with a wavelength of 8 microns in the sagittal direction, and T1 is the field curvature of far-infrared light with a wavelength of 8 microns in the meridional direction; S2 is the field curvature of far-infrared light with a wavelength of 10 microns in the sagittal direction, and T2 is the field curvature of far-infrared light with a wavelength of 10 microns in the meridional direction; S3 is the field curvature of far-infrared light with a wavelength of 12 microns in the sagittal direction, and T3 is the field curvature of far-infrared light with a wavelength of 12 microns in the meridional direction. Figure 5 It can be seen that the field curvature of the large aperture far-infrared optical system 100 in the sagittal direction is 0.1447 mm, and the field curvature of the large aperture far-infrared optical system 100 in the meridional direction is 0.1309 mm, which meets the requirements for field curvature in the excellent imaging quality standard.

[0173] See also Figure 6 , Figure 6 1 shows the distortion diagram of the large aperture far-infrared optical system 100 provided in Example 1, Figure 6 The horizontal axis is distortion, and its unit is percentage; Figure 6 The vertical axis is the Y-axis field of view, and its unit is degree. Figure 61 and 2 show the distortion curves of the large aperture far-infrared optical system 100 provided in Example 1 at wavelengths of 8 microns, 10 microns, and 12 microns. Since the three curves almost completely overlap, the three curves are not distinguished in this embodiment. Figure 6 It can be seen that the maximum distortion of the large aperture far-infrared optical system 100 provided in Example 1 is -11.64%, which meets the requirement of clear imaging.

[0174] See also Figure 7 , Figure 7 : shows a relative illumination diagram of the large aperture far-infrared optical system 100 provided in Example 1, Figure 7 The middle horizontal axis represents the image height, which is in millimeters; Figure 7 The vertical axis represents relative illumination. Figure 7 It can be seen that within the full field of view, the relative illumination of the large aperture far-infrared optical system 100 provided in Example 1 is greater than 74%, and the brightness of the picture is relatively uniform.

[0175] See also Figure 8 , Figure 8 The vertical axis chromatic aberration diagram of the large aperture far-infrared optical system 100 provided in Example 1 under far-infrared light with wavelengths of 8 microns, 10 microns and 12 microns is shown. Figure 8 The horizontal axis is the position of light of different wavelengths on the vertical axis image plane 80, in micrometers; Figure 8 The vertical coordinate is the image height, and its unit is millimeters. Figure 8 A total of three curves are shown, among which the curve at 0 micrometers is a far-infrared light with a wavelength of 10 micrometers. Since the other two curves are too close together, the other two curves are not distinguished. Figure 8 It can be seen that within the full field of view, the maximum vertical axis chromatic aberration is less than 2 microns. Therefore, the large aperture far-infrared optical system 100 provided in Example 1 has good chromatic aberration correction capability.

[0176] Example 2

[0177] Fig. 9 FIG. 1 shows a schematic diagram of the architecture layout of the large aperture far-infrared optical system 100 provided in Example 2. Fig. 9 The medium-large aperture far-infrared optical system 100 includes, along the optical axis 90, from the object plane 70 to the image plane 80, a first aspheric lens 10, an aperture 50, a second aspheric lens 20, a diffractive optical element 40, a third aspheric lens 30 and a protective glass 60, wherein the diffractive optical element 40 is a diffractive surface, and the diffractive surface is arranged on the object side of the third aspheric lens 30. Some parameters of the large aperture far-infrared optical system 100 provided in Example 2 are shown in Table 2-1.

[0178] Table 2-1. Partial parameters of the large aperture far-infrared optical system 100 provided in Example 2

[0179] Optical indicators data Effective focal length 6.151mm F-number 0.9 distortion -11.24％ Relative Illuminance >74％ Total optical length (TTL) 13.562mm Optical Back Focus (BFL) 5.259mm Maximum field of view FOV (2ω) 61.968° Working band 8μm-12μm

[0180] As can be seen from Table 2-1, the total optical length of the large aperture far-infrared optical system 100 is relatively short, only 13.56 mm, so the volume of the large aperture far-infrared optical system 100 provided in Example 2 is relatively small. The F number of the large aperture far-infrared optical system 100 is 0.9, and the large aperture far-infrared optical system 100 has a large amount of light input, thereby ensuring excellent imaging quality.

[0181] Along the direction of the optical axis 90 from the object plane 70 to the image plane 80, starting from the object plane 70, each surface in the large aperture far-infrared optical system 100 is numbered, and the parameters of each surface are summarized to obtain the following Table 2-2.

[0182] Table 2-2. Parameters of various surfaces in the large aperture far-infrared optical system 100 provided in Example 2

[0183]

[0184]

[0185] The analysis of each surface in Table 2-2 can refer to Example 1, and this example does not analyze each surface again.

[0186] 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:

[0187]

[0188] Among them, Z(r) is the distance vector height from the vertex of the aspheric surface when the aspheric surface is at a height of r along the optical axis 90 degrees; c is the curvature of the aspheric surface, c = 1 / R, R is the radius of curvature of the aspheric surface; k is the cone coefficient; A, B, C, D... are the aspheric coefficients. The values ​​of k, A, B, C, D... of Surface 1, Surface 2, Surface 4, Surface 5, Surface 6 and Surface 7 can be obtained from Table 2-3.

[0189] Table 2-3. Coefficients of various orders of even-order aspheric surfaces in the large aperture far-infrared optical system 100 provided in Example 2

[0190] surface k A B C D E 1 8.99E-01 -9.03E-04 -6.30E-05 -5.51E-08 -3.57E-07 2.38E-08 2 -4.04E-01 1.88E-04 -1.01E-05 -1.77E-05 2.92E-06 -2.20E-07 4 -9.90E+01 -1.63E-03 -1.05E-06 -2.05E-05 2.72E-06 -2.02E-07 5 8.67E-02 -1.23E-03 -4.16E-05 1.46E-06 9.92E-08 -3.40E-08 6 2.71E+00 1.33E-04 -5.78E-05 8.65E-06 -7.31E-07 7.23E-09 7 -4.04E+00 -1.61E-03 2.67E-05 -2.01E-06 6.02E-08 -1.92E-09

[0191] The coefficients of each order of the even-order aspheric surfaces of surface 1, surface 2, surface 4, surface 5, surface 6 and surface 7 can be obtained from Table 2-3. The specific values ​​of the coefficients of each order of the even-order aspheric surfaces are not described one by one in this embodiment.

[0192] The diffraction surface is set on surface 6, and the phase expression of the diffraction surface is Where, ρ = r / r0, r is the radius of the diffraction surface, r0 is the normalized radius of the diffraction surface, A i is the phase coefficient of the diffraction surface, and N is the number of terms in the polynomial. The coefficient of the diffraction surface can be obtained from Table 2-4.

[0193] Table 2-4. Coefficients of the diffraction surface in the large aperture far-infrared optical system 100 provided in Example 2

[0194]

[0195]

[0196] See also Fig.10 , Fig.10 FIG. 1 shows a phase distribution diagram of the diffraction surface in the large aperture far-infrared optical system 100 provided in Example 2. Fig.10 The horizontal axis represents the distance from the center of the diffraction surface. Fig.10 The vertical axis represents the phase. Since the phase is a periodic function about 2π, there is a relationship (n is an integer), therefore, Fig.10 The phase of the diffraction surface in Example 2 is modulo 2π to achieve normalization processing to meet the needs of actual processing of the diffraction surface.

[0197] See also Fig.11 , Fig.11 FIG. 1 shows the MTF field curve of the large aperture far-infrared optical system 100 provided in Example 2. Fig.11 The horizontal axis in is the image height, that is, the horizontal axis measures the field of view with the image height, and the unit of the horizontal axis is millimeters; Fig.11 The vertical axis is the MTF value. Fig.11 The MTF of 10lp / mm spatial frequency is listed as the sagittal curve S1 and the meridional curve T1 of the field of view, the MTF of 21lp / mm spatial frequency is listed as the sagittal curve S2 and the meridional curve T2 of the field of view, the MTF of 42lp / mm spatial frequency is listed as the sagittal curve S3 and the meridional curve T3 of the field of view, and the MTF of 62.5lp / mm spatial frequency is listed as the sagittal curve S4 and the meridional curve T4 of the field of view. Fig.11 It can be seen that at a spatial frequency of 62.5lp / mm, the MTF is greater than 0.17 in the entire field of view, and the large aperture far-infrared optical system 100 has excellent imaging quality.

[0198] See also Fig.12 , Fig.12 The point diagram of the large aperture far-infrared optical system 100 provided in Example 2 is shown. Fig.12 It can be seen that the maximum size of the spot diagram in the entire field of view is less than 2 pixels (16 micrometers), so the light is concentrated and the large aperture far-infrared optical system 100 provided in Example 2 has a sharp imaging effect.

[0199] See also Fig.13 , Fig.13 1 shows a field curvature diagram of the large aperture far-infrared optical system 100 provided in Example 2, Fig.13 The central horizontal axis is the field curvature, which is in millimeters; Fig.13 The vertical axis is the Y-axis field of view, and its unit is degree. Fig.13 S1 is the field curvature of far-infrared light with a wavelength of 8 microns in the sagittal direction, and T1 is the field curvature of far-infrared light with a wavelength of 8 microns in the meridional direction; S2 is the field curvature of far-infrared light with a wavelength of 10 microns in the sagittal direction, and T2 is the field curvature of far-infrared light with a wavelength of 10 microns in the meridional direction; S3 is the field curvature of far-infrared light with a wavelength of 12 microns in the sagittal direction, and T3 is the field curvature of far-infrared light with a wavelength of 12 microns in the meridional direction. Fig.13 It can be seen that the field curvature of the large aperture far-infrared optical system 100 in the sagittal direction is 0.0447 mm, and the field curvature of the large aperture far-infrared optical system 100 in the meridional direction is 0.0510 mm, which meets the requirements for field curvature in the excellent imaging quality standard.

[0200] See also Fig.14 , Fig.14 1 shows the distortion diagram of the large aperture far-infrared optical system 100 provided in Example 2, Fig.14 The horizontal axis is distortion, and its unit is percentage; Fig.14 The vertical axis is the Y-axis field of view, and its unit is degree. Fig.14 2 shows the distortion curves of the large aperture far-infrared optical system 100 provided in Example 2 at wavelengths of 8 microns, 10 microns, and 12 microns. Since the three curves almost completely overlap, the three curves are not distinguished in this embodiment. Fig.14 It can be seen that the maximum distortion of the large aperture far-infrared optical system 100 provided in Example 2 is -11.23%, which meets the requirement of clear imaging.

[0201] See also Fig.15 , Fig.15 : shows a relative illumination diagram of the large aperture far-infrared optical system 100 provided in Example 2, Fig.15 The middle horizontal axis represents the image height, which is in millimeters; Fig.15 The vertical axis represents relative illumination. Fig.15 It can be seen that within the full field of view, the relative illumination of the large aperture far-infrared optical system 100 provided in Example 2 is greater than 74%, and the brightness of the picture is relatively uniform.

[0202] See also Fig.16 , Fig.16 The vertical axis chromatic aberration diagram of the large aperture far-infrared optical system 100 provided in Example 2 under far-infrared light with wavelengths of 8 microns, 10 microns and 12 microns is shown. Fig.16 The horizontal axis is the position of light of different wavelengths on the vertical axis image plane 80, in micrometers; Fig.16 The vertical coordinate is the image height, and its unit is millimeters. Fig.16 A total of three curves are shown, among which the curve at 0 micrometers is a far-infrared light with a wavelength of 10 micrometers. Since the other two curves are too close together, the other two curves are not distinguished. Fig.16 It can be seen that within the full field of view, the maximum vertical axis chromatic aberration is less than 3 microns. Therefore, the large aperture far-infrared optical system 100 provided in Example 2 has good chromatic aberration correction capability.

[0203] Example 3

[0204] Fig.17 FIG. 1 shows a schematic diagram of the architecture layout of the large aperture far-infrared optical system 100 provided in Example 3. Fig.17 The medium-large aperture far-infrared optical system 100 includes, along the optical axis 90, from the object plane 70 to the image plane 80, a first aspheric lens 10, an aperture 50, a second aspheric lens 20, a diffractive optical element 40, a third aspheric lens 30 and a protective glass 60, wherein the diffractive optical element 40 is a diffractive surface, and the diffractive surface is arranged on the object side of the third aspheric lens 30. Some parameters of the large aperture far-infrared optical system 100 provided in Example 3 are shown in Table 3-1.

[0205] Table 3-1. Partial parameters of the large aperture far-infrared optical system 100 provided in Example 3

[0206]

[0207]

[0208] As can be seen from Table 3-1, the total optical length of the large aperture far-infrared optical system 100 is relatively short, only 12.85 mm, so the volume of the large aperture far-infrared optical system 100 provided in Example 3 is relatively small. The F number of the large aperture far-infrared optical system 100 is 0.9, and the large aperture far-infrared optical system 100 has a large amount of light input, thereby ensuring excellent imaging quality.

[0209] Along the direction of the optical axis 90 from the object plane 70 to the image plane 80, starting from the object plane 70, each surface in the large aperture far-infrared optical system 100 is numbered, and the parameters of each surface are summarized to obtain the following Table 3-2.

[0210] Table 3-2. Parameters of various surfaces in the large aperture far-infrared optical system 100 provided in Example 3

[0211] Surface number Surface type Curvature radius (mm) Thickness(mm) Material 0 flat unlimited unlimited - 1 even aspherical surface 5.16149 1.062 Chalcogenide glass 2 even aspherical surface 4.41856 1.127 - 3 Aperture unlimited 0.862 - 4 even aspherical surface -17.74 2.002 Chalcogenide glass 5 even aspherical surface -7.3558 0.827 - 6 even aspherical surface -6.7549 1.287 Chalcogenide glass 7 even aspherical surface -6.2922 4.959 - 8 flat unlimited 0.625 silicon 9 flat unlimited 0.100 - 10 flat unlimited - -

[0212] The analysis of each surface in Table 3-2 can refer to Example 1, and this example does not analyze each surface again.

[0213] 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:

[0214]

[0215] 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 90 degrees; 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 and surface 7 can be obtained from Table 3-3.

[0216] Table 3-3. Coefficients of the even-order aspheric surfaces in the large aperture far-infrared optical system 100 provided in Example 3

[0217] surface k A B C D E 1 5.26E-01 -6.02E-04 -1.65E-04 2.45E-06 -7.70E-07 2.39E-08 2 -4.01E-01 3.09E-04 -5.74E-05 -3.39E-05 2.02E-06 -3.61E-08 4 1.75E+01 -2.27E-03 -4.49E-05 -2.94E-05 3.84E-06 -2.57E-07 5 1.04E-01 -3.62E-04 -5.26E-05 6.07E-07 1.29E-08 -2.06E-09 6 -3.66E-01 3.03E-03 -1.39E-04 8.66E-06 -1.86E-07 5.31E-10 7 -5.77E+00 -9.19E-04 2.93E-05 -1.14E-06 9.46E-08 -7.04E-10

[0218] The coefficients of each order of the even-order aspheric surfaces of surface 1, surface 2, surface 4, surface 5, surface 6 and surface 7 can be obtained from Table 3-3. The specific values ​​of the coefficients of each order of the even-order aspheric surfaces are not described one by one in this embodiment.

[0219] The diffraction surface is set on surface 6, and the phase expression of the diffraction surface is Where, ρ = r / r0, r is the radius of the diffraction surface, r0 is the normalized radius of the diffraction surface, A i is the phase coefficient of the diffraction surface, and N is the number of terms in the polynomial. The coefficient of the diffraction surface can be obtained from Table 3-4.

[0220] Table 3-4. Coefficients of diffraction surface in the large aperture far-infrared optical system 100 provided in Example 3

[0221] surface Face type Normalized radius A1 A2 A3 A4 6 Binary diffraction surface 4.2mm -7.01E+00 -6.62E+01 4.06E+01 8.77E+02

[0222] See also Fig.18 , Fig.18 FIG. 4 shows a phase distribution diagram of the diffraction surface in the large aperture far-infrared optical system 100 provided in Example 3. Fig.18 The horizontal axis represents the distance from the center of the diffraction surface. Fig.18The vertical axis represents the phase. Since the phase is a periodic function about 2π, there is a relationship (n is an integer), therefore, Fig.18 The phase of the diffraction surface in Example 3 is modulo 2π to achieve normalization processing to meet the needs of actual processing of the diffraction surface.

[0223] See also Fig.19 , Fig.19 FIG. 1 shows the MTF field curve of the large aperture far-infrared optical system 100 provided in Example 3. Fig.19 The horizontal axis in is the image height, that is, the horizontal axis measures the field of view with the image height, and the unit of the horizontal axis is millimeters; Fig.19 The vertical axis is the MTF value. Fig.19 The MTF of 10lp / mm spatial frequency is listed as the sagittal curve S1 and the meridional curve T1 of the field of view, the MTF of 21lp / mm spatial frequency is listed as the sagittal curve S2 and the meridional curve T2 of the field of view, the MTF of 42lp / mm spatial frequency is listed as the sagittal curve S3 and the meridional curve T3 of the field of view, and the MTF of 62.5lp / mm spatial frequency is listed as the sagittal curve S4 and the meridional curve T4 of the field of view. Fig.19 It can be seen that at a spatial frequency of 62.5lp / mm, the MTF is greater than 0.16 in the entire field of view, and the large aperture far-infrared optical system 100 has excellent imaging quality.

[0224] See also Fig. 20 , Fig. 20 The point diagram of the large aperture far-infrared optical system 100 provided in Example 3 is shown. Fig. 20 It can be seen that the maximum size of the spot diagram in the entire field of view is less than 2 pixels (16 micrometers), so the light is concentrated and the large aperture far-infrared optical system 100 provided in Example 3 has a sharp imaging effect.

[0225] See also Fig.21 , Fig.21 : shows a field curvature diagram of the large aperture far-infrared optical system 100 provided in Example 3, Fig.21 The central horizontal axis is the field curvature, which is in millimeters; Fig.21 The vertical axis is the Y-axis field of view, and its unit is degree. Fig.21 S1 is the field curvature of far-infrared light with a wavelength of 8 microns in the sagittal direction, and T1 is the field curvature of far-infrared light with a wavelength of 8 microns in the meridional direction; S2 is the field curvature of far-infrared light with a wavelength of 10 microns in the sagittal direction, and T2 is the field curvature of far-infrared light with a wavelength of 10 microns in the meridional direction; S3 is the field curvature of far-infrared light with a wavelength of 12 microns in the sagittal direction, and T3 is the field curvature of far-infrared light with a wavelength of 12 microns in the meridional direction. Fig.21It can be seen that the field curvature of the large aperture far-infrared optical system 100 in the sagittal direction is 0.1729 mm, and the field curvature of the large aperture far-infrared optical system 100 in the meridional direction is 0.1092 mm, which meets the requirements for field curvature in the excellent imaging quality standard.

[0226] See also Fig. 22 , Fig. 22 1 shows the distortion diagram of the large aperture far-infrared optical system 100 provided in Example 3, Fig. 22 The horizontal axis is distortion, and its unit is percentage; Fig. 22 The vertical axis is the Y-axis field of view, and its unit is degree. Fig. 22 2 shows the distortion curves of the large aperture far-infrared optical system 100 provided in Example 3 at wavelengths of 8 microns, 10 microns, and 12 microns. Since the three curves are almost completely overlapped, the three curves are not distinguished in this embodiment. Fig. 22 It can be seen that the maximum distortion of the large aperture far-infrared optical system 100 provided in Example 3 is -11.60%, which meets the requirement of clear imaging.

[0227] See also Fig.23 , Fig.23 : shows a relative illumination diagram of the large aperture far-infrared optical system 100 provided in Example 3, Fig.23 The middle horizontal axis represents the image height, which is in millimeters; Fig.23 The vertical axis represents relative illumination. Fig.23 It can be seen that the relative illumination of the large aperture far-infrared optical system 100 provided in Example 3 is greater than 74% within the full field of view, and the brightness of the picture is relatively uniform.

[0228] See also Fig.24 , Fig.24 FIG. 1 shows a vertical axis chromatic aberration diagram of the large aperture far-infrared optical system 100 provided in Example 3. Fig.24 The horizontal axis is the position of light of different wavelengths on the vertical axis image plane 80, in micrometers; Fig.24 The vertical coordinate is the image height, and its unit is millimeters. Fig.24 There are three curves shown, among which the M1 curve is the vertical axis chromatic aberration curve of far infrared light with a wavelength of 8 microns, the M2 curve located at 0 microns on the horizontal axis is the vertical axis chromatic aberration curve of far infrared light with a wavelength of 10 microns, and the M3 curve is the vertical axis chromatic aberration curve of far infrared light with a wavelength of 12 microns. Fig.24 It can be seen that within the full field of view, the maximum vertical axis chromatic aberration is less than 2 microns. Therefore, the large aperture far-infrared optical system 100 provided in Example 3 has good chromatic aberration correction capability.

[0229] Example 4

[0230] Fig.25FIG. 1 shows a schematic diagram of the architecture layout of the large aperture far-infrared optical system 100 provided in Example 4. Fig.25 The medium-large aperture far-infrared optical system 100 includes, along the optical axis 90, from the object plane 70 to the image plane 80, a first aspheric lens 10, an aperture 50, a second aspheric lens 20, a diffractive optical element 40, a third aspheric lens 30 and a protective glass 60, wherein the diffractive optical element 40 is a diffractive surface, and the diffractive surface is arranged on the object side of the third aspheric lens 30. Some parameters of the large aperture far-infrared optical system 100 provided in Example 4 are shown in Table 4-1.

[0231] Table 4-1. Partial parameters of the large aperture far-infrared optical system 100 provided in Example 4

[0232] Optical indicators Required value Effective focal length 5.865mm F-number 1.0 distortion -9.47％ Relative Illuminance >81.2％ Total optical length (TTL) 12.88mm Optical Back Focus (BFL) 5.23mm Maximum field of view FOV (2ω) 62.465° Working band 8μm-12μm

[0233] As can be seen from Table 4-1, the total optical length of the large aperture far-infrared optical system 100 is relatively short, only 12.88 mm, so the volume of the large aperture far-infrared optical system 100 provided in Example 4 is relatively small. The F number of the large aperture far-infrared optical system 100 is 1.0, and the large aperture far-infrared optical system 100 has a large amount of light input, thereby ensuring excellent imaging quality.

[0234] Along the direction of the optical axis 90 from the object plane 70 to the image plane 80, starting from the object plane 70, each surface in the large aperture far-infrared optical system 100 is numbered, and the parameters of each surface are summarized to obtain the following Table 4-2.

[0235] Table 4-2. Parameters of various surfaces in the large aperture far-infrared optical system 100 provided in Example 4

[0236]

[0237]

[0238] The analysis of each surface in Table 4-2 can refer to Example 1, and this example does not analyze each surface again.

[0239] 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:

[0240]

[0241] 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 90 degrees; 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 and Surface 7 can be obtained from Table 4-3.

[0242] Table 4-3. Coefficients of various orders of even-order aspheric surfaces in the large aperture far-infrared optical system 100 provided in Example 4

[0243] surface k A B C D E 1 -1.01E+00 -8.18E-04 6.24E-04 -2.30E-04 4.19E-05 -4.21E-06 2 7.26E-01 1.58E-03 -3.66E-03 2.24E-03 -7.82E-04 1.50E-04 4 8.38E+01 -2.87E-03 1.36E-03 -6.69E-04 1.50E-04 -1.63E-05 5 1.76E+00 6.89E-04 -3.86E-04 1.27E-04 -3.59E-05 5.28E-06 6 1.24E+00 2.85E-03 3.39E-05 -5.22E-05 5.07E-06 6.37E-07 7 5.49E-01 1.43E-03 -8.50E-05 1.00E-05 -8.57E-07 7.84E-08

[0244] The coefficients of each order of the even-order aspheric surfaces of surface 1, surface 2, surface 4, surface 5, surface 6 and surface 7 can be obtained from Table 4-3. The specific values ​​of the coefficients of each order of the even-order aspheric surfaces are not described one by one in this embodiment.

[0245] The diffraction surface is set on surface 6, and the phase expression of the diffraction surface is Where, ρ = r / r0, r is the radius of the diffraction surface, r0 is the normalized radius of the diffraction surface, A i is the phase coefficient of the diffraction surface, and N is the number of terms in the polynomial. The coefficient of the diffraction surface can be obtained from Table 4-4.

[0246] Table 4-4. Coefficients of diffraction surface in the large aperture far-infrared optical system 100 provided in Example 4

[0247] surface Face type Normalized radius A1 A2 A3 A4 6 Binary diffraction surface 3.4mm -1.09E+01 1.899 -8.591 -3.038E+01

[0248] See also Fig.26 , Fig.26 FIG. 4 shows a phase distribution diagram of the diffraction surface in the large aperture far-infrared optical system 100 provided in Example 4. Fig.26 The horizontal axis represents the distance from the center of the diffraction surface. Fig.26 The vertical axis represents the phase. Since the phase is a periodic function about 2π, there is a relationship (n is an integer), therefore, Fig.26 The phase of the diffraction surface in Example 4 is modulo 2π to achieve normalization processing to meet the needs of actual processing of the diffraction surface.

[0249] See also Fig. 27 , Fig. 27 FIG. 4 shows the MTF field curve of the large aperture far-infrared optical system 100 provided in Example 4. Fig. 27 The horizontal axis in is the image height, that is, the horizontal axis measures the field of view with the image height, and the unit of the horizontal axis is millimeters; Fig. 27 The vertical axis is the MTF value. Fig. 27The MTF of 10lp / mm spatial frequency is listed as the sagittal curve S1 and the meridional curve T1 of the field of view, the MTF of 21lp / mm spatial frequency is listed as the sagittal curve S2 and the meridional curve T2 of the field of view, the MTF of 42lp / mm spatial frequency is listed as the sagittal curve S3 and the meridional curve T3 of the field of view, and the MTF of 62.5lp / mm spatial frequency is listed as the sagittal curve S4 and the meridional curve T4 of the field of view. Fig. 27 It can be seen that at a spatial frequency of 62.5lp / mm, the MTF is greater than 0.16 in the entire field of view, and the large aperture far-infrared optical system 100 has excellent imaging quality.

[0250] See also Fig.28 , Fig.28 The point diagram of the large aperture far-infrared optical system 100 provided in Example 4 is shown. Fig.28 It can be seen that the maximum size of the spot diagram in the entire field of view is less than 2 pixels (16 micrometers), so the light is concentrated and the large aperture far-infrared optical system 100 provided in Example 4 has a sharp imaging effect.

[0251] See also Fig.29 , Fig.29 1 shows a field curvature diagram of the large aperture far-infrared optical system 100 provided in Example 4, Fig.29 The central horizontal axis is the field curvature, which is in millimeters; Fig.29 The vertical axis is the Y-axis field of view, and its unit is degree. Fig.29 S1 is the field curvature of far-infrared light with a wavelength of 8 microns in the sagittal direction, and T1 is the field curvature of far-infrared light with a wavelength of 8 microns in the meridional direction; S2 is the field curvature of far-infrared light with a wavelength of 10 microns in the sagittal direction, and T2 is the field curvature of far-infrared light with a wavelength of 10 microns in the meridional direction; S3 is the field curvature of far-infrared light with a wavelength of 12 microns in the sagittal direction, and T3 is the field curvature of far-infrared light with a wavelength of 12 microns in the meridional direction. Fig.29 It can be seen that the field curvature of the large aperture far-infrared optical system 100 in the sagittal direction is 0.1053 mm, and the field curvature of the large aperture far-infrared optical system 100 in the meridional direction is 0.3185 mm, which meets the requirements for field curvature in the excellent imaging quality standard.

[0252] See also Fig.30 , Fig.30 1 shows the distortion diagram of the large aperture far-infrared optical system 100 provided in Example 4, Fig.30 The horizontal axis is distortion, and its unit is percentage; Fig.30 The vertical axis is the Y-axis field of view, and its unit is degree. Fig.30 2 shows the distortion curves of the large aperture far-infrared optical system 100 provided in Example 4 at wavelengths of 8 microns, 10 microns, and 12 microns. Since the three curves completely overlap, the three curves are not distinguished in this embodiment. Fig.30 It can be seen that the maximum distortion of the large aperture far-infrared optical system 100 provided in Example 4 is -9.46%, which meets the requirement of clear imaging.

[0253] See also Fig.31 , Fig.31 : shows a relative illumination diagram of the large aperture far-infrared optical system 100 provided in Example 4, Fig.31 The middle horizontal axis represents the image height, which is in millimeters; Fig.31 The vertical axis represents relative illumination. Fig.31 It can be seen that the relative illumination of the large aperture far-infrared optical system 100 provided in Example 4 is greater than 81% within the full field of view, and the brightness of the picture is relatively uniform.

[0254] See also Fig.32 , Fig.32 The vertical axis chromatic aberration diagram of the large aperture far-infrared optical system 100 provided in Example 4 is shown. Fig.32 The horizontal axis is the position of light of different wavelengths on the vertical axis image plane 80, in micrometers; Fig.32 The vertical coordinate is the image height, and its unit is millimeters. Fig.32 There are three curves shown, among which the M1 curve is the vertical axis chromatic aberration curve of far infrared light with a wavelength of 8 microns, the M2 curve located at 0 microns on the horizontal axis is the vertical axis chromatic aberration curve of far infrared light with a wavelength of 10 microns, and the M3 curve is the vertical axis chromatic aberration curve of far infrared light with a wavelength of 12 microns. Fig.32 It can be seen that within the full field of view, the maximum chromatic aberration between different wavelengths is less than 4 microns. Therefore, the large aperture far-infrared optical system 100 provided in Example 4 has good chromatic aberration correction capability.

[0255] Example 5

[0256] Fig.33 FIG. 1 shows a schematic diagram of the architecture layout of the large aperture far-infrared optical system 100 provided in Example 5. Fig.33 The medium-large aperture far-infrared optical system 100 includes, along the optical axis 90, from the object plane 70 to the image plane 80, a first aspheric lens 10, an aperture 50, a second aspheric lens 20, a diffractive optical element 40, a third aspheric lens 30 and a protective glass 60, wherein the diffractive optical element 40 is a diffractive surface, and the diffractive surface is arranged on the object side of the third aspheric lens 30. Some parameters of the large aperture far-infrared optical system 100 provided in Example 5 are shown in Table 5-1.

[0257] Table 5-1. Partial parameters of the large aperture far-infrared optical system 100 provided in Example 5

[0258] Optical indicators Required value Effective focal length 5.924mm F-number 1.0 distortion -9.2％ Relative Illuminance >82.3％ Total optical length (TTL) 13.44mm Optical Back Focus (BFL) 5.10mm Maximum field of view FOV (2ω) 61.780° Working band 8μm-12μm

[0259] As can be seen from Table 5-1, the total optical length of the large aperture far-infrared optical system 100 is relatively short, only 13.44 mm, so the volume of the large aperture far-infrared optical system 100 provided in Example 5 is relatively small. The F number of the large aperture far-infrared optical system 100 is 1.0, and the large aperture far-infrared optical system 100 has a large amount of light input, thereby ensuring excellent imaging quality.

[0260] Along the direction of the optical axis 90 from the object plane 70 to the image plane 80, starting from the object plane 70, each surface in the large aperture far-infrared optical system 100 is numbered, and the parameters of each surface are summarized to obtain the following Table 5-2.

[0261] Table 5-2. Parameters of various surfaces in the large aperture far-infrared optical system 100 provided in Example 5

[0262] Surface number Surface type Curvature radius (mm) Thickness(mm) Material 0 flat unlimited unlimited - 1 even aspherical surface 6.16 2.12 Chalcogenide glass 2 even aspherical surface 5.15 0.70 - 3 Aperture unlimited 0.21 - 4 even aspherical surface -155.25 2.47 Chalcogenide glass 5 even aspherical surface -9.05 0.24 - 6 even aspherical surface -6.09 2.60 Chalcogenide glass 7 even aspherical surface -6.24 4.40 - 8 flat unlimited 0.60 silicon 9 flat unlimited 0.10 - 10 flat unlimited - -

[0263] The analysis of each surface in Table 5-2 can refer to Example 1, and this example does not analyze each surface again.

[0264] 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:

[0265]

[0266] 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 90 degrees; 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 and Surface 7 can be obtained from Table 5-3.

[0267] Table 5-3. Coefficients of various orders of even-order aspheric surfaces in the large aperture far-infrared optical system 100 provided in Example 5

[0268]

[0269]

[0270] The coefficients of each order of the even-order aspheric surfaces of surface 1, surface 2, surface 4, surface 5, surface 6 and surface 7 can be obtained from Table 5-3. The specific values ​​of the coefficients of each order of the even-order aspheric surfaces are not described one by one in this embodiment.

[0271] The diffraction surface is set on surface 6, and the phase expression of the diffraction surface is Where, ρ = r / r0, r is the radius of the diffraction surface, r0 is the normalized radius of the diffraction surface, A iis the phase coefficient of the diffraction surface, and N is the number of terms in the polynomial. The coefficient of the diffraction surface can be obtained from Table 5-4.

[0272] Table 5-4. Coefficients of diffraction surface in the large aperture far-infrared optical system 100 provided in Example 5

[0273] surface Face type Normalized radius A1 A2 A3 A4 6 Binary diffraction surface 3.3mm -1.27E+01 1.92E+01 -1.16E+02 2.36E+02

[0274] See also Fig.34 , Fig.34 FIG. 4 shows a phase distribution diagram of the diffraction surface in the large aperture far-infrared optical system 100 provided in Example 5. Fig.34 The horizontal axis represents the distance from the center of the diffraction surface. Fig.34 The vertical axis represents the phase. Since the phase is a periodic function about 2π, there is a relationship (n is an integer), therefore, Fig.34 The phase of the diffraction surface in Example 5 is modulo 2π to achieve normalization processing to meet the needs of actual processing of the diffraction surface.

[0275] See also Fig.35 , Fig.35 FIG. 5 shows the MTF field curve of the large aperture far-infrared optical system 100 provided in Example 5. Fig.35 The horizontal axis in is the image height, that is, the horizontal axis measures the field of view with the image height, and the unit of the horizontal axis is millimeters; Fig.35 The vertical axis is the MTF value. Fig.35 The MTF of 10lp / mm spatial frequency is listed as the sagittal curve S1 and the meridional curve T1 of the field of view, the MTF of 21lp / mm spatial frequency is listed as the sagittal curve S2 and the meridional curve T2 of the field of view, the MTF of 42lp / mm spatial frequency is listed as the sagittal curve S3 and the meridional curve T3 of the field of view, and the MTF of 62.5lp / mm spatial frequency is listed as the sagittal curve S4 and the meridional curve T4 of the field of view. Fig.35 It can be seen that at a spatial frequency of 62.5lp / mm, the MTF is greater than 0.16 in the entire field of view, and the large aperture far-infrared optical system 100 has excellent imaging quality.

[0276] See also Fig.36 , Fig.36 The point diagram of the large aperture far-infrared optical system 100 provided in Example 5 is shown. Fig.36 It can be seen that the maximum size of the spot diagram in the entire field of view is less than 2 pixels (16 micrometers), so the light is concentrated and the large aperture far-infrared optical system 100 provided in Example 5 has a sharp imaging effect.

[0277] See also Fig.37 , Fig.371 shows a field curvature diagram of the large aperture far-infrared optical system 100 provided in Example 5, Fig.37 The central horizontal axis is the field curvature, which is in millimeters; Fig.37 The vertical axis is the Y-axis field of view, and its unit is degree. Fig.37 S1 is the field curvature of far-infrared light with a wavelength of 8 microns in the sagittal direction, and T1 is the field curvature of far-infrared light with a wavelength of 8 microns in the meridional direction; S2 is the field curvature of far-infrared light with a wavelength of 10 microns in the sagittal direction, and T2 is the field curvature of far-infrared light with a wavelength of 10 microns in the meridional direction; S3 is the field curvature of far-infrared light with a wavelength of 12 microns in the sagittal direction, and T3 is the field curvature of far-infrared light with a wavelength of 12 microns in the meridional direction. Fig.37 It can be seen that the field curvature of the large aperture far-infrared optical system 100 in the sagittal direction is 0.1116 mm, and the field curvature of the large aperture far-infrared optical system 100 in the meridional direction is 0.2797 mm, which meets the requirements for field curvature in the excellent imaging quality standard.

[0278] See also Fig.38 , Fig.38 1 shows the distortion diagram of the large aperture far-infrared optical system 100 provided in Example 5, Fig.38 The horizontal axis is distortion, and its unit is percentage; Fig.38 The vertical axis is the Y-axis field of view, and its unit is degree. Fig.38 2 shows the distortion curves of the large aperture far-infrared optical system 100 provided in Example 5 at wavelengths of 8 microns, 10 microns, and 12 microns. Since the three curves completely overlap, the three curves are not distinguished in this embodiment. Fig.38 It can be seen that the maximum distortion of the large aperture far-infrared optical system 100 provided in Example 5 is -9.19%, which meets the requirement of clear imaging.

[0279] See also Fig.39 , Fig.39 : shows a relative illumination diagram of the large aperture far-infrared optical system 100 provided in Example 5, Fig.39 The middle horizontal axis represents the image height, which is in millimeters; Fig.39 The vertical axis represents relative illumination. Fig.39 It can be seen that within the full field of view, the relative illumination of the large aperture far-infrared optical system 100 provided in Example 5 is greater than 82%, and the brightness of the picture is relatively uniform.

[0280] See also Fig.40 , Fig.40 FIG. 1 shows a vertical axis chromatic aberration diagram of the large aperture far-infrared optical system 100 provided in Example 5. Fig.40 The horizontal axis is the position of light of different wavelengths on the vertical axis image plane 80, in micrometers; Fig.40 The vertical coordinate is the image height, and its unit is millimeters. Fig.40There are three curves shown, among which the M1 curve is the vertical axis chromatic aberration curve of far infrared light with a wavelength of 8 microns, the M2 curve located at 0 microns on the horizontal axis is the vertical axis chromatic aberration curve of far infrared light with a wavelength of 10 microns, and the M3 curve is the vertical axis chromatic aberration curve of far infrared light with a wavelength of 12 microns. Fig.40 It can be seen that within the full field of view, the maximum chromatic aberration between different wavelengths is less than 2 microns. Therefore, the large aperture far-infrared optical system 100 provided in Example 5 has good chromatic aberration correction capability.

[0281] Example 6

[0282] Fig.41 FIG. 1 shows a schematic diagram of the architecture layout of the large aperture far-infrared optical system 100 provided in Example 6. Fig.41 The medium-large aperture far-infrared optical system 100 includes, along the optical axis 90, from the object plane 70 to the image plane 80, a first aspheric lens 10, an aperture 50, a second aspheric lens 20, a diffractive optical element 40, a third aspheric lens 30 and a protective glass 60, wherein the diffractive optical element 40 is a diffractive surface, and the diffractive surface is arranged on the object side of the third aspheric lens 30. Some parameters of the large aperture far-infrared optical system 100 provided in Example 6 are shown in Table 6-1.

[0283] Table 6-1. Partial parameters of the large aperture far-infrared optical system 100 provided in Example 6

[0284] Optical indicators Required value Effective focal length 5.822mm F-number 1.0 distortion -8.6％ Relative Illuminance >81.2％ Total optical length (TTL) 11.89mm Optical Back Focus (BFL) 5.20mm Maximum field of view FOV (2ω) 61.730° Working band 8μm-12μm

[0285] As can be seen from Table 6-1, the total optical length of the large aperture far-infrared optical system 100 is relatively short, only 11.90 mm, so the volume of the large aperture far-infrared optical system 100 provided in Example 6 is relatively small. The F number of the large aperture far-infrared optical system 100 is 1.0, and the large aperture far-infrared optical system 100 has a large amount of light input, thereby ensuring excellent imaging quality.

[0286] Along the direction of the optical axis 90 from the object plane 70 to the image plane 80, starting from the object plane 70, each surface in the large aperture far-infrared optical system 100 is numbered, and the parameters of each surface are summarized to obtain the following Table 6-2.

[0287] Table 6-2. Parameters of various surfaces in the large aperture far-infrared optical system 100 provided in Example 6

[0288]

[0289]

[0290] The analysis of each surface in Table 6-2 can refer to Example 1, and this example does not analyze each surface again.

[0291] 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:

[0292]

[0293] Among them, Z(r) is the distance vector height from the vertex of the aspheric surface when the aspheric surface is at a height of r along the optical axis 90 degrees; c is the curvature of the aspheric surface, c = 1 / R, R is the radius of curvature of the aspheric surface; k is the cone coefficient; A, B, C, D... are the aspheric coefficients. The values ​​of k, A, B, C, D... of Surface 1, Surface 2, Surface 4, Surface 5, Surface 6 and Surface 7 can be obtained from Table 6-3.

[0294] Table 6-3. Coefficients of the even-order aspheric surfaces in the large aperture far-infrared optical system 100 provided in Example 6

[0295] surface k A B C D E 1 -2.74E-01 -2.73E-04 6.72E-04 -2.64E-04 5.07E-05 -5.25E-06 2 1.54E+00 3.52E-03 -4.56E-03 2.34E-03 -7.82E-04 1.49E-04 4 9.44E+01 -3.97E-03 1.43E-03 -7.67E-04 1.71E-04 -1.71E-05 5 1.38E+00 6.60E-04 -5.78E-04 1.62E-04 -4.15E-05 5.97E-06 6 9.19E-01 4.29E-03 9.89E-05 -9.51E-05 1.64E-05 -2.74E-07 7 4.57E-01 2.24E-03 -1.05E-04 1.54E-05 -1.23E-06 1.71E-07

[0296] The coefficients of each order of the even-order aspheric surfaces of surface 1, surface 2, surface 4, surface 5, surface 6 and surface 7 can be obtained from Table 6-3. The specific values ​​of the coefficients of each order of the even-order aspheric surfaces are not described one by one in this embodiment.

[0297] The diffraction surface is set on surface 6, and the phase expression of the diffraction surface is Where, ρ = r / r0, r is the radius of the diffraction surface, r0 is the normalized radius of the diffraction surface, A i is the phase coefficient of the diffraction surface, and N is the number of terms in the polynomial. The coefficient of the diffraction surface can be obtained from Table 6-4.

[0298] Table 6-4. Coefficients of diffraction surface in the large aperture far-infrared optical system 100 provided in Example 6

[0299] surface Face type Normalized radius A1 A2 A3 A4 6 Binary diffraction surface 3.3mm -2.31E+01 7.06E+01 -2.45E+02 4.43E+02

[0300] See also Fig.42 , Fig.42 FIG. 4 shows a phase distribution diagram of the diffraction surface in the large aperture far-infrared optical system 100 provided in Example 6, Fig.42 The horizontal axis represents the distance from the center of the diffraction surface. Fig.42 The vertical axis represents the phase. Since the phase is a periodic function about 2π, there is a relationship (n is an integer), therefore, Fig.42 The phase of the diffraction surface in Example 6 is modulo 2π to achieve normalization processing to meet the needs of actual processing of the diffraction surface.

[0301] See also Fig.43 , Fig.43 FIG. 1 shows the MTF field curve of the large aperture far-infrared optical system 100 provided in Example 6. Fig.43 The horizontal axis in is the image height, that is, the horizontal axis measures the field of view with the image height, and the unit of the horizontal axis is millimeters; Fig.43 The vertical axis is the MTF value. Fig.43 The MTF of 10lp / mm spatial frequency is listed as the sagittal curve S1 and the meridional curve T1 of the field of view, the MTF of 21lp / mm spatial frequency is listed as the sagittal curve S2 and the meridional curve T2 of the field of view, the MTF of 42lp / mm spatial frequency is listed as the sagittal curve S3 and the meridional curve T3 of the field of view, and the MTF of 62.5lp / mm spatial frequency is listed as the sagittal curve S4 and the meridional curve T4 of the field of view. Fig.43 It can be seen that at a spatial frequency of 62.5lp / mm, the MTF is greater than 0.15 in the entire field of view, and the large aperture far-infrared optical system 100 has excellent imaging quality.

[0302] See also Fig.44 , Fig.44 The point diagram of the large aperture far-infrared optical system 100 provided in Example 6 is shown. Fig.44 It can be seen that the maximum size of the spot diagram in the entire field of view is less than 2 pixels (16 micrometers), so the light is concentrated and the large aperture far-infrared optical system 100 provided in Example 6 has a sharp imaging effect.

[0303] See also Fig.45 , Fig.45 1 shows a field curvature diagram of the large aperture far-infrared optical system 100 provided in Example 6, Fig.45 The central horizontal axis is the field curvature, which is in millimeters; Fig.45 The vertical axis is the Y-axis field of view, and its unit is degree. Fig.45 S1 is the field curvature of far-infrared light with a wavelength of 8 microns in the sagittal direction, and T1 is the field curvature of far-infrared light with a wavelength of 8 microns in the meridional direction; S2 is the field curvature of far-infrared light with a wavelength of 10 microns in the sagittal direction, and T2 is the field curvature of far-infrared light with a wavelength of 10 microns in the meridional direction; S3 is the field curvature of far-infrared light with a wavelength of 12 microns in the sagittal direction, and T3 is the field curvature of far-infrared light with a wavelength of 12 microns in the meridional direction. Fig.45 It can be seen that the field curvature of the large aperture far-infrared optical system 100 in the sagittal direction is 0.2611 mm, and the field curvature of the large aperture far-infrared optical system 100 in the meridional direction is 0.5365 mm, which meets the requirements for field curvature in the excellent imaging quality standard.

[0304] See also Fig.46 , Fig.46 1 shows the distortion diagram of the large aperture far-infrared optical system 100 provided in Example 6, Fig.46 The horizontal axis is distortion, and its unit is percentage; Fig.46 The vertical axis is the Y-axis field of view, and its unit is degree. Fig.46 1 and 2 show the distortion curves of the large aperture far-infrared optical system 100 provided in Example 6 at wavelengths of 8 microns, 10 microns, and 12 microns. Since the three curves completely overlap, this embodiment does not distinguish between the three curves. Fig.46 It can be seen that the maximum distortion of the large aperture far-infrared optical system 100 provided in Example 6 is -8.60%, which meets the requirement of clear imaging.

[0305] See also Fig.47 , Fig.47 : shows a relative illumination diagram of the large aperture far-infrared optical system 100 provided in Example 6, Fig.47 The middle horizontal axis represents the image height, which is in millimeters; Fig.47 The vertical axis represents relative illumination. Fig.47 It can be seen that within the full field of view, the relative illumination of the large aperture far-infrared optical system 100 provided in Example 6 is greater than 81%, and the brightness of the picture is relatively uniform.

[0306] See also Fig.48 , Fig.48 The vertical axis chromatic aberration diagram of the large aperture far-infrared optical system 100 provided in Example 6 is shown. Fig.48 The horizontal axis is the position of light of different wavelengths on the vertical axis image plane 80, in micrometers; Fig.48 The vertical coordinate is the image height, and its unit is millimeters. Fig.48 There are three curves shown, among which the M1 curve is the vertical axis chromatic aberration curve of far infrared light with a wavelength of 8 microns, the M2 curve located at 0 microns on the horizontal axis is the vertical axis chromatic aberration curve of far infrared light with a wavelength of 10 microns, and the M3 curve is the vertical axis chromatic aberration curve of far infrared light with a wavelength of 12 microns. Fig.48 It can be seen that within the full field of view, the maximum chromatic aberration between different wavelengths is less than 4 microns. Therefore, the large aperture far-infrared optical system 100 provided in Example 6 has good chromatic aberration correction capability.

[0307] After summarizing the various parameters of the large aperture far-infrared optical system 100 provided by the above six embodiments, the following Table 7 is obtained. The display of Table 7 is mainly used to illustrate that the various conditions satisfied by the large aperture far-infrared optical system 100 provided by the present application are all verified and supported by experiments.

[0308] Table 7. Parameters of the large aperture far-infrared optical system 100 provided in various embodiments

[0309]

[0310]

[0311]

[0312] The present application also provides a large aperture far-infrared optical lens (not shown), which includes an imaging detector (not shown) and the above-mentioned large aperture far-infrared optical system 100. The specific structure of the large aperture far-infrared optical system 100 can be found above and will not be repeated here. The imaging detector is arranged on the image plane 80 of the large aperture 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).

[0313] 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 large aperture far-infrared optical system, characterized in that: The large aperture far-infrared optical system comprises: A first aspheric lens, whose object side surface is convex toward the object side and whose image side surface is convex toward the object side; A second aspheric lens having positive optical power, an object side surface convex toward the image side, and an image side surface convex toward the image side; a third aspheric lens having positive optical power, an object side surface convex toward the image side, and an image side surface convex toward the image side; A diffractive optical element is arranged in the optical path of the large aperture far-infrared optical system; Among them, the first aspheric lens, the second aspheric lens, and the third aspheric lens are arranged in sequence along the optical axis from the object side to the image side; the large aperture far-infrared optical system satisfies: |f2|<|f3|<|f1|, f1 is the focal length of the first aspheric lens, f2 is the focal length of the second aspheric lens, and f3 is the focal length of the third aspheric lens.

2. The large aperture far-infrared optical system according to claim 1, characterized in that: The large aperture far-infrared optical system further comprises an aperture, and the aperture is arranged in the optical path of the large aperture far-infrared optical system; The large aperture far-infrared optical system meets the following requirements: Wherein, f is the effective focal length of the large aperture far-infrared optical system, and D S is the aperture of the aperture, the TTL is the total optical length of the large aperture far-infrared optical system, and the FOV is the maximum field of view angle of the large aperture far-infrared optical system.

3. The large aperture far-infrared optical system according to claim 1, characterized in that: The large aperture far-infrared optical system meets the following requirements:

4. The large aperture far-infrared optical system according to claim 1, characterized in that: The large aperture far-infrared optical system meets the following requirements: Among them, the FOV is the maximum field angle of the large aperture far-infrared optical system, and f is the effective focal length of the large aperture far-infrared optical system.

5. The large aperture far-infrared optical system according to claim 1, characterized in that: The large aperture far-infrared optical system further comprises an aperture, and the aperture is arranged in the optical path of the large aperture far-infrared optical system; The large aperture far-infrared optical system meets the following requirements: Wherein, D1 is the maximum effective diameter of the first aspheric lens, D2 is the maximum effective diameter of the second aspheric lens, D3 is the maximum effective diameter of the third aspheric lens, and D S is the aperture of the aperture.

6. The large aperture far-infrared optical system according to claim 1, characterized in that: The large aperture far-infrared optical system meets the following requirements: Wherein, D1 is the maximum effective diameter of the first aspheric lens, D2 is the maximum effective diameter of the second aspheric lens, and D3 is the maximum effective diameter of the third aspheric lens.

7. The large aperture far-infrared optical system according to claim 1, characterized in that: The large aperture far-infrared optical system meets the following requirements: Among them, the Imgh is half of the diagonal length of the image formed by the large aperture far-infrared optical system at the maximum field of view angle, the n1 is the refractive index of the first aspheric lens, the FOV is the maximum field of view angle of the large aperture far-infrared optical system, the FNO is the aperture number of the large aperture far-infrared optical system, and the R1 is the radius of curvature of the object side of the first aspheric lens.

8. The large aperture far-infrared optical system according to claim 1, characterized in that: The large aperture far-infrared optical system meets the following requirements: Among them, the f 12 is the combined focal length of the first aspheric lens and the second aspheric lens, and the f 23 is the combined focal length of the second aspheric lens and the third aspheric lens.

9. The large aperture far-infrared optical system according to any one of claims 1 to 8, characterized in that: The diffractive optical element is a diffractive surface, and the diffractive surface is arranged on the object side surface of the third aspherical lens.

10. A large aperture far-infrared optical lens, characterized in that: The large aperture far-infrared optical lens comprises: an imaging detector and a large aperture far-infrared optical system as described in any one of claims 1 to 9; the imaging detector is arranged on the image plane of the large aperture far-infrared optical system.

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