Long-focus far-infrared optical system and long-focus far-infrared optical lens

Abstract

The utility model discloses a long-focus far-infrared optical system and a long-focus far-infrared optical lens, the long-focus far-infrared optical system comprises a first aspheric lens, a second aspheric lens and a diffractive optical element, the focal power of the first aspheric lens is positive, and the object side surface and the image side surface of the first aspheric lens both protrude towards the object side; the focal power of the second aspheric lens is positive; the diffractive optical element is arranged on the image side surface of the first aspheric lens; wherein the first aspheric lens and the second aspheric lens are sequentially arranged from the object side to the image side along the optical axis. According to the long-focus far-infrared optical system provided by the invention, the diffractive optical element is opposite to the first aspheric lens and the second aspheric lens in dispersion characteristic, and correction of chromatic aberration of the long-focus far-infrared optical system is realized through combination of the diffractive optical element, the first aspheric lens and the second aspheric lens; therefore, the long-focus far infrared optical system has excellent imaging quality.

Description

Technical Field

[0001] This application relates to the field of optical systems, and more particularly to a long-focal-length far-infrared optical system and a long-focal-length far-infrared optical lens. Background Technology

[0002] In low visibility conditions such as rain, fog, and snow, far-infrared optical systems have an advantage over visible light optical systems in imaging.

[0003] The design of long-focal-length far-infrared optical systems requires correction of a large number of chromatic aberrations. Due to the limited range of far-infrared lens materials available, it is difficult to correct the chromatic aberrations in long-focal-length far-infrared optical systems, resulting in less than ideal imaging quality and room for improvement. Utility Model Content

[0004] To address the aforementioned technical issues, this application provides a telephoto far-infrared optical system and a telephoto far-infrared optical lens, aiming to provide a telephoto far-infrared optical system with excellent imaging quality.

[0005] According to one aspect of the embodiments of this application, a long-focal-length far-infrared optical system is disclosed, the long-focal-length far-infrared optical system comprising:

[0006] The first aspherical lens has a positive optical power, and both the object side and the image side of the first aspherical lens are convex towards the object side.

[0007] The second aspherical lens has a positive optical power.

[0008] A diffractive optical element is disposed on the image-side surface of the first aspherical lens;

[0009] The first aspherical lens and the second aspherical lens are arranged sequentially from the object side to the image side along the optical axis.

[0010] In some embodiments, the long-focal-length far-infrared optical system satisfies: Where f1 is the focal length of the first aspherical lens and f2 is the focal length of the second aspherical lens.

[0011] In some embodiments, the long-focal-length far-infrared optical system satisfies: Among them, D 11 D is the effective diameter of the object-side surface of the first aspherical lens. 21 The effective diameter of the object-side surface of the second aspherical lens is denoted as .

[0012] In some embodiments, the long-focal-length far-infrared optical system satisfies: Wherein, L1 is the distance on the optical axis between the object-side surface of the first aspherical lens and the object-side surface of the second aspherical lens, L2 is the distance on the optical axis between the image-side surface of the second aspherical lens and the image plane of the long-focal-length far-infrared optical system, and FOV is the maximum field of view of the long-focal-length far-infrared optical system.

[0013] In some embodiments, the long-focal-length far-infrared optical system satisfies: Where T1 is the center thickness of the first aspherical lens, T2 is the center thickness of the second aspherical lens, and D... 11 D is the effective diameter of the object-side surface of the first aspherical lens. 21 The effective diameter of the object-side surface of the second aspherical lens is denoted as .

[0014] In some embodiments, the long-focal-length far-infrared optical system satisfies: Among them, D 11 f1 is the effective diameter of the object side surface of the first aspherical lens, and f1 is the focal length of the first aspherical lens.

[0015] In some embodiments, the long-focal-length far-infrared optical system satisfies: Among them, D 11 ImgH is the effective diameter of the object side surface of the first aspherical lens, ImgH is the radius of the imaging area of ​​the long-focal far-infrared optical system on the image plane corresponding to the maximum half field of view, and Fno is the aperture number of the long-focal far-infrared optical system.

[0016] In some embodiments, the long-focal-length far-infrared optical system satisfies: Wherein, R1 is the radius of curvature of the object side of the first aspherical lens, R2 is the radius of curvature of the image side of the first aspherical lens, R3 is the radius of curvature of the object side of the second aspherical lens, and R4 is the radius of curvature of the image side of the second aspherical lens.

[0017] In some embodiments, the diffractive optical element satisfies: The maximum phase difference of the diffractive optical element.

[0018] In some embodiments, the long-focal-length far-infrared optical system further includes an aperture stop disposed between the first aspherical lens and the second aspherical lens; or, the aperture stop is disposed on the object side of the first aspherical lens.

[0019] A second aspect of this application provides a long-focal-length far-infrared optical lens, the long-focal-length far-infrared optical lens comprising: an imaging detector and a long-focal-length far-infrared optical system as described in any of the preceding claims; the imaging detector is disposed on the image plane of the long-focal-length far-infrared optical system.

[0020] The long-focal-length far-infrared optical system provided in this application includes: a first aspherical lens, a second aspherical lens, and a diffractive optical element. The first aspherical lens has positive optical power, and both its object-side and image-side surfaces are convex towards the object side. The second aspherical lens also has positive optical power. The diffractive optical element is disposed on the image-side surface of the first aspherical lens. The first and second aspherical lenses are sequentially arranged along the optical axis from the object side to the image side. In the long-focal-length far-infrared optical system provided in this application, the diffractive optical element has opposite dispersion characteristics to the first and second aspherical lenses. By combining the diffractive optical element with the first and second aspherical lenses, chromatic aberration correction is achieved, resulting in excellent imaging quality for the long-focal-length far-infrared optical system. Attached Figure Description

[0021] The above and other objectives, features and advantages of this application will become more apparent from a detailed description of exemplary embodiments thereof with reference to the accompanying drawings.

[0022] Figure 1 A schematic diagram of the architecture layout of a long-focal-length far-infrared optical system in one embodiment of this application is shown.

[0023] Figure 2 The diagram shows the phase distribution of the diffractive optical element of a long-focal-length far-infrared optical system according to an embodiment of this application.

[0024] Figure 3 The MTF field-of-view curve of a long-focal-length far-infrared optical system according to an embodiment of this application is shown.

[0025] Figure 4 The field curve diagram of a long-focal-length far-infrared optical system according to an embodiment of this application is shown.

[0026] Figure 5 A distortion diagram of a long-focal-length far-infrared optical system according to an embodiment of this application is shown.

[0027] Figure 6 A schematic diagram of the architecture layout of a long-focal-length far-infrared optical system in one embodiment of this application is shown.

[0028] Figure 7 The diagram shows the phase distribution of the diffractive optical element of a long-focal-length far-infrared optical system according to an embodiment of this application.

[0029] Figure 8 The MTF field-of-view curve of a long-focal-length far-infrared optical system according to an embodiment of this application is shown.

[0030] Figure 9 The field curve diagram of a long-focal-length far-infrared optical system according to an embodiment of this application is shown.

[0031] Figure 10 A distortion diagram of a long-focal-length far-infrared optical system according to an embodiment of this application is shown.

[0032] Figure 11 A schematic diagram of the architecture layout of a long-focal-length far-infrared optical system in one embodiment of this application is shown.

[0033] Figure 12 The diagram shows the phase distribution of the diffractive optical element of a long-focal-length far-infrared optical system according to an embodiment of this application.

[0034] Figure 13 The MTF field-of-view curve of a long-focal-length far-infrared optical system according to an embodiment of this application is shown.

[0035] Figure 14 The field curve diagram of a long-focal-length far-infrared optical system according to an embodiment of this application is shown.

[0036] Figure 15 A distortion diagram of a long-focal-length far-infrared optical system according to an embodiment of this application is shown.

[0037] Figure 16 A schematic diagram of the architecture layout of a long-focal-length far-infrared optical system in one embodiment of this application is shown.

[0038] Figure 17 The diagram shows the phase distribution of the diffractive optical element of a long-focal-length far-infrared optical system according to an embodiment of this application.

[0039] Figure 18 The MTF field-of-view curve of a long-focal-length far-infrared optical system according to an embodiment of this application is shown.

[0040] Figure 19 The field curve diagram of a long-focal-length far-infrared optical system according to an embodiment of this application is shown.

[0041] Figure 20 A distortion diagram of a long-focal-length far-infrared optical system according to an embodiment of this application is shown.

[0042] Figure Labels

[0043] 100. Long-focus far-infrared optical system;

[0044] 10. First aspherical lens; 20. Second aspherical lens; 30. Diffractive optical element; 40. Aperture stop; 50. Protective glass; 60. Object plane; 70. Image plane; 80. Optical axis. Detailed Implementation

[0045] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, they are provided to make the description of this application more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art. The drawings are merely illustrative of this application and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted.

[0046] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more exemplary embodiments. Numerous specific details are provided in the following description to give a full understanding of exemplary embodiments of this application. However, those skilled in the art will recognize that the technical solutions of this application can be practiced with one or more specific details omitted, or other modules, components, etc., can be employed. In other instances, well-known structures, methods, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this application.

[0047] Please see Figure 1 , Figure 1 A schematic diagram of the architectural layout of a long-focal-length far-infrared optical system 100 according to an embodiment of this application is shown, wherein the optical axis 80 is the center line of the light beam. Figure 1 In the long-focal-length far-infrared optical system 100, the object is located to the left of the leftmost lens, meaning the object side is to the left of the leftmost lens, and the object plane 60 is located on the object side. The image formed by the long-focal-length far-infrared optical system 100 is located to the right of the rightmost lens, meaning the image side is to the right of the rightmost lens, and the image plane 70 is located on the image side. Therefore, the direction along the optical axis 80 from the object plane 60 to the image plane 70 is consistent with the direction along the optical axis 80 from the object side to the image side. In the long-focal-length far-infrared optical system 100, the side of each optical element closest to the object plane 60 is the object side or object-side surface of the corresponding optical element. Similarly, the side of each optical element in the long-focal-length far-infrared optical system 100 closest to the image plane 70 is the image side or image-side surface of the corresponding optical element.

[0048] The long-focal-length far-infrared optical system 100 includes a first aspherical lens 10, a second aspherical lens 20, and a diffractive optical element 30.

[0049] The first aspherical lens 10 has a positive optical power, and the object side of the first aspherical lens 10 is convex to the object side, while the image side of the second aspherical lens 20 is convex to the object side.

[0050] The second aspherical lens 20 has a positive optical power. The first aspherical lens 10 and the second aspherical lens 20 are arranged sequentially from the object side to the image side along the optical axis 80.

[0051] A diffractive optical element (DOE) 30 is an optical device designed based on the principle of light diffraction. It precisely modulates the wavefront of incident light through micro / nano structures or periodic patterns to achieve specific optical functions. The DOE 30 is disposed on the image-side surface of the first aspherical lens 10. The negative dispersion introduced by the DOE 30 can correct the positive dispersion introduced by the first aspherical lens 10 and the second aspherical lens 20, thereby achieving achromatic aberration.

[0052] In the long-focal-length far-infrared optical system 100 provided in this application, the diffraction optical element 30 has opposite dispersion characteristics to the first aspherical lens 10 and the second aspherical lens 20. The chromatic aberration of the long-focal-length far-infrared optical system 100 is corrected by the combination of the diffraction optical element 30 with the first aspherical lens 10 and the second aspherical lens 20, so that the long-focal-length far-infrared optical system 100 has excellent imaging quality.

[0053] For the second aspherical lens 20 mentioned above, the shapes of its object side and image side are not fixed.

[0054] Please see Figure 1 and Figure 11 In some embodiments, the object side of the second aspherical lens 20 convexes towards the object side, and the image side of the second aspherical lens 20 convexes towards the object side.

[0055] Please see Figure 6 and Figure 16 In some embodiments, the paraxial region of the object-side surface of the second aspherical lens 20 convexes towards the object side, and the edge of the object-side surface of the second aspherical lens 20 is inverted. Similarly, the paraxial region of the image-side surface of the second aspherical lens 20 convexes towards the object side, and the edge of the image-side surface of the second aspherical lens 20 is inverted. In this application, the paraxial region of the lens refers to a small area on the lens close to the optical axis 80, in which the angle between the light rays and the optical axis 80 is very small, nearly parallel to the optical axis 80.

[0056] In some embodiments, the diffractive optical element 30 satisfies: The maximum phase difference of the diffractive optical element 30 corresponding to a wavelength of 10 micrometers. The unit is 2π rad. By properly configuring the maximum phase difference of the diffractive optical element 30, it is beneficial to eliminate the chromatic aberration of the long-focal-length far-infrared optical system 100, thereby improving the imaging quality of the long-focal-length far-infrared optical system 100.

[0057] Furthermore, in some embodiments, the diffractive optical element 30 satisfies: The maximum phase difference of the diffractive optical element 30 corresponding to a wavelength of 10 micrometers. The unit is 2π rad. By precisely configuring the maximum phase difference of the diffractive optical element 30, the negative dispersion introduced by the diffractive optical element 30 can be ensured to be more accurate, so that the negative dispersion introduced by the diffractive surface can be better matched with the positive dispersion introduced by the first aspherical lens 10 and the second aspherical lens 20, which can better eliminate chromatic aberration and thus ensure the imaging quality of the long-focal far-infrared optical system 100.

[0058] In some embodiments, the diffractive optical element 30 is a diffractive surface, which is an optical element surface that uses the diffraction effect of light to control the light wavefront and has a specific microstructure design.

[0059] In some embodiments, the diffractive optical element 30 is a metasurface, which is composed of subwavelength nanoantennas or micro / nano structures arranged together. By adjusting the shape, size and arrangement of the nanoantennas or micro / nano structures, the phase, amplitude and polarization of light can be precisely controlled.

[0060] In some embodiments, the long-focal-length far-infrared optical system 100 satisfies condition one: Where f1 is the focal length of the first aspherical lens 10 and f2 is the focal length of the second aspherical lens 20. f1 and f2 have the same dimension, both being units of length, such as millimeters.

[0061] Condition 1 reflects the optical power distribution relationship of the long-focal-length far-infrared optical system 100. Condition 1 is beneficial to the aberration correction of the long-focal-length far-infrared optical system 100 and can ensure that the long-focal-length far-infrared optical system 100 can provide excellent imaging quality.

[0062] In some embodiments, the long-focal-length far-infrared optical system 100 satisfies condition two: Among them, D 11 The effective diameter of the object-side surface of the first aspherical lens 10, in this application, refers to the diameter of the maximum light-transmitting area of ​​the corresponding surface of the lens (object-side or image-side) along the optical axis 80. For example, the effective diameter of the object-side surface of the first aspherical lens 10 refers to the diameter of the maximum light-transmitting area of ​​the object-side surface of the first aspherical lens 10. D 21 D is the effective diameter of the object-side surface of the second aspherical lens 20. 11 D 21 They have the same dimensions, both being units of length, such as millimeters.

[0063] Condition two is the ratio of the effective diameter of the object-side surface of the first aspherical lens 10 to the effective diameter of the object-side surface of the second aspherical lens 20. The lower limit of condition two ensures that the long-focal-length far-infrared optical system 100 has a small volume. At the same time, the lower limit of condition two ensures that the rear port diameter (the diameter near the end of the second aspherical lens 20) of the long-focal-length far-infrared optical system 100 is not too large. The upper limit of condition two ensures that the long-focal-length far-infrared optical system 100 has sufficient optical back focus, thereby ensuring that the long-focal-length far-infrared optical system 100 has a small volume while still reserving enough installation space for the imaging sensor and structural components.

[0064] In some embodiments, the long-focal-length far-infrared optical system 100 satisfies condition three: Where L1 is the distance on the optical axis 80 between the object-side surface of the first aspherical lens 10 and the object-side surface of the second aspherical lens 20, and L2 is the distance on the optical axis 80 between the image-side surface of the second aspherical lens 20 and the image plane 70 of the long-focal-length far-infrared optical system 100. FOV (Field of View) is the maximum field of view of the long-focal-length far-infrared optical system 100. L1 and L2 have the same dimension, both being units of length, such as millimeters. The unit of FOV is an angle unit, such as degrees.

[0065] In some embodiments, the long-focal-length far-infrared optical system 100 satisfies condition four: Wherein, T1 is the center thickness of the first aspherical lens 10. In this application, the thickness of the lens refers to the thickness of the lens along the optical axis 80. For example, the center thickness of the first aspherical lens 10 refers to the thickness of the first aspherical lens 10 along the optical axis 80. T2 is the center thickness of the second aspherical lens 20, D 11 D is the effective diameter of the object-side surface of the first aspherical lens 10. 21 The effective diameter of the object-side surface of the second aspherical lens 20. T1, T2, D 11 D 21 They have the same dimensions, both being units of length, such as millimeters.

[0066] The upper limit of conditional expression four is used to control the weight of the long-focal-length far-infrared optical system 100, thereby reducing the amount of lens material used and thus lowering the cost of the long-focal-length far-infrared optical system 100. The lower limit of conditional expression four is used to ensure that both the first aspherical lens 10 and the second aspherical lens 20 have the expected thickness, so that the thickness of the first aspherical lens 10 and the second aspherical lens 20 meets the processing requirements.

[0067] In some embodiments, the long-focal-length far-infrared optical system 100 satisfies condition five: Among them, D 11Let f1 be the effective diameter of the object-side surface of the first aspherical lens 10, and f1 be the focal length of the first aspherical lens 10. 11 f1 and f2 have the same dimensions; both are units of length, such as millimeters.

[0068] The upper limit of condition five ensures that the long-focal-length far-infrared optical system 100 has a shorter length, while the lower limit of condition five ensures that the first aspherical lens 10 has sufficient optical power to guarantee imaging quality.

[0069] In some embodiments, the long-focal-length far-infrared optical system 100 satisfies condition six: Among them, D 11 is the effective diameter of the object-side surface of the first aspherical lens 10. ImgH is the radius of the imaging region of the long-focal-length far-infrared optical system 100 on the image plane 70 corresponding to the maximum half-field angle; that is, ImgH is half the diagonal length of the image sensor adapted to the long-focal-length far-infrared optical system 100. Fno is the aperture number of the long-focal-length far-infrared optical system 100; that is, Fno is the F-number of the long-focal-length far-infrared optical system 100. D 11 Both ImgH and 1mgH have the same dimensions; they are both units of length, such as millimeters.

[0070] The upper limit of condition six ensures that the aperture of the first aspherical lens 10 is not too large, and the lower limit of condition six ensures that the long-focal far-infrared optical system 100 has a sufficient amount of light intake, thereby ensuring that the image formed by the long-focal far-infrared optical system 100 is relatively bright.

[0071] In some embodiments, the long-focal-length far-infrared optical system 100 satisfies condition seven: Wherein, R1 is the radius of curvature of the object-side surface of the first aspherical lens 10, R2 is the radius of curvature of the image-side surface of the first aspherical lens 10, R3 is the radius of curvature of the object-side surface of the second aspherical lens 20, and R4 is the radius of curvature of the image-side surface of the second aspherical lens 20. R1, R2, R3, and R4 have the same dimensions and are all units of length, such as millimeters.

[0072] Condition 7 ensures that the surface shape and optical power of the first aspherical lens 10 and the second aspherical lens 20 are reasonably matched, thereby ensuring that the long-focal-length far-infrared optical system 100 has excellent imaging quality.

[0073] The long-focus far-infrared optical system 100 also includes an aperture 40, which is used to control the amount of light entering the long-focus far-infrared optical system 100 to ensure that the long-focus far-infrared optical system 100 can work effectively and generate high-quality images.

[0074] In some embodiments, the aperture stop 40 is disposed on the object side of the first aspherical lens 10. Specifically, the aperture stop 40 may be disposed in the following positions:

[0075] (1) The aperture 40 is disposed on the object side of the first aspherical lens 10, and the aperture 40 is disposed at a distance from the first aspherical lens 10.

[0076] (2) The aperture 40 is disposed on the object side of the first aspherical lens 10, and the aperture 40 is attached to the object side of the first aspherical lens 10, that is, the aperture 40 is disposed on the object side of the first aspherical lens 10.

[0077] In some embodiments, the aperture stop 40 is disposed between the first aspherical lens 10 and the second aspherical lens 20. Specifically, the aperture stop 40 can be positioned as follows:

[0078] (1) The aperture 40 is disposed between the first aspherical lens 10 and the second aspherical lens 20, and the aperture 40 is attached to the image side of the first aspherical lens 10, that is, the aperture 40 is disposed on the image side of the first aspherical lens 10.

[0079] (2) The aperture 40 is disposed between the first aspherical lens 10 and the second aspherical lens 20, and the aperture 40 is disposed at intervals with the first aspherical lens 10 and the second aspherical lens 20.

[0080] (3) The aperture 40 is disposed between the first aspherical lens 10 and the second aspherical lens 20, and the aperture 40 is attached to the object side of the second aspherical lens 20, that is, the aperture 40 is disposed on the object side of the second aspherical lens 20.

[0081] In some embodiments, the telephoto far-infrared optical system 100 further includes a protective glass 50 located between the second aspherical lens 20 and the image plane 70. The protective glass 50 is used to protect the lens and the image sensor matched with the telephoto far-infrared optical system 100.

[0082] The long-focal-length far-infrared optical system 100 provided in this application has the following advantages:

[0083] (1) Total Track Length (TTL) ≤ 46mm;

[0084] (2) The MTF (Modulation Transfer Function) is greater than 0.4 at the cutoff frequency of 42 lp / mm within the field of view;

[0085] (3) Distortion ≤ 1%;

[0086] (4) F number ≤ 1.

[0087] This application provides three exemplary long-focal-length far-infrared optical systems 100 that meet usage requirements in three embodiments. The long-focal-length far-infrared optical systems 100 provided in each embodiment of this application will be described in detail below.

[0088] Example 1

[0089] Figure 1 A schematic diagram of the architecture layout of the long-focal-length far-infrared optical system 100 provided in Embodiment 1 is shown. Figure 1 The mid-to-long focal length far-infrared optical system 100, along the optical axis 80 from the object plane 60 to the image plane 70, includes, in sequence: an aperture stop 40, a first aspherical lens 10, a diffractive optical element 30, a second aspherical lens 20, and a protective glass 50. The aperture stop 40 is located on the object-side surface of the first aspherical lens 10, and the diffractive optical element is a diffraction surface located on the image-side surface of the first aspherical lens 10. Some parameters of the long focal length far-infrared optical system 100 provided in Embodiment 1 are shown in Table 1-1.

[0090] Table 1-1. Partial parameters of the long-focal-length far-infrared optical system 100 provided in Example 1

[0091] Parameter Data Optical total length (TTL) 44.19 mm Maximum field angle (2ω) 16.0° F number 0.9 Effective focal length 34.6 mm Operating wavelength band Far infrared (8 μm - 12 μm)

[0092] As shown in Table 1-1, the total optical length of the long-focus far-infrared optical system 100 is 44.19 mm and the F-number of the long-focus far-infrared optical system 100 is 0.9. Therefore, the long-focus far-infrared optical system 100 has a large amount of light intake, which can ensure excellent imaging quality.

[0093] Along the optical axis 80 from the object plane 60 to the image plane 70, starting from the aperture stop 40, each surface in the long focal far-infrared optical system 100 is numbered, and the parameters of each surface are summarized to obtain Table 1-2 below.

[0094] Table 1-2. Parameters of each surface in the long-focal-length far-infrared optical system 100 provided in Example 1

[0095]

[0096] For each surface in Table 1-2, surface 1 is the aperture stop 40, surface 2 is the object-side surface of the first aspherical lens 10, surface 3 is the image-side surface of the first aspherical lens 10, and the diffraction surface is disposed on surface 3. Surface 4 is the object-side surface of the second aspherical lens 20, and surface 5 is the image-side surface of the second aspherical lens 20. Surface 6 is the object-side surface of the protective glass 50, surface 7 is the image-side surface of the protective glass 50, and surface 8 is the image surface 70.

[0097] As shown in Table 1-2, surface 1 is a sphere with an infinite radius of curvature, meaning it is a plane. The distance between surface 1 and surface 2 is -8.79 mm, where the negative sign indicates that surface 2 bulges out of surface 1 towards the object. Surface 2 is an even-order aspherical surface with a radius of curvature of 26.51 mm. The distance between surface 2 and surface 3 is 5.81 mm, and the material between them is chalcogenide glass. Surface 3 is an even-order aspherical surface with a radius of curvature of 33.09 mm. The distance between surface 3 and surface 4 is 25.35 mm, and the material between them is air. Surface 4 is an even-order aspherical surface with a radius of curvature of 17.25 mm. The distance between surface 4 and surface 5 is 3.36 mm, and the material between them is chalcogenide glass. Surface 5 is an even-order aspherical surface with a radius of curvature of 17.84 mm. The distance between surface 5 and surface 6 is 8.46 mm, and the material between them is air. Surface 6 is a sphere with an infinite radius of curvature, therefore, surface 6 is a plane. The distance between surface 6 and surface 7 is 1 mm, and the material between them is germanium. Surface 7 is a sphere with an infinite radius of curvature, therefore, surface 7 is a plane. The distance between surface 7 and surface 8 is 0.21 mm, and the material between them is air. The material between surface 1 and surface 2 is silicon. Surface 2 has an infinite radius of curvature, i.e., it is a plane. The distance between surface 2 and surface 3 is 0.49 mm, and the material between them is air. Surface 3 has a radius of curvature of -5.7 mm. The distance between surface 3 and surface 4 is 1.55 mm, and the material between them is silicon. Surface 4 has a radius of curvature of -2.9 mm, and the distance between surface 4 and surface 5 is 1.4 mm. The material between surface 4 and surface 5 is air. Surface 5 has an infinite radius of curvature, meaning surface 5 is a plane, and the distance between surface 5 and surface 6 is 0.5 mm. The material between surface 5 and surface 6 is silicon. Surface 6 has an infinite radius of curvature, meaning surface 6 is a plane, and the distance between surface 6 and surface 7 is 0.1 mm. The material between surface 6 and surface 7 is air.

[0098] Surfaces 2, 3, 4, and 5 are even-order aspherical surfaces, and their surface shapes satisfy the following relationship:

[0099]

[0100] Where Z(r) is the distance vector from the vertex of the aspherical surface at a height of r along the optical axis 80; c is the surface curvature of the aspherical surface, c = 1 / R, where R is the radius of curvature of the aspherical surface; k is the conic coefficient; A, B, C, D... are aspherical coefficients. The values ​​of k, A, B, C, D... for surfaces 2, 3, 4, and 5 can be obtained from Table 1-3.

[0101] Table 1-3. Coefficients of even-order aspherical surfaces in the long-focal-length far-infrared optical system 100 provided in Example 1

[0102]

[0103]

[0104] Please refer to Tables 1-3. For surface 2, k is -1.46E+00, A is 1.22E-05, B is 2.41E-09, C is 9.59E-12, D is 5.83E-14, E is -7.82E-17, F is -4.29E-20, and G is 0.00E+00. The coefficients of even-order aspherical surfaces 3, 4, and 5 can be found in Tables 1-3, and will not be described in detail in this embodiment.

[0105] The diffraction plane is located on surface 3, and the phase expression of the diffraction plane is: Where ρ = r / r0, r is the radius of the diffraction surface, r0 is the normalized radius of the diffraction surface, and A i Here, represents 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.

[0106] Table 1-4. Coefficients of the diffraction surface in the long-focal-length far-infrared optical system 100 provided in Example 1

[0107]

[0108] Please see Figure 2 , Figure 2 The phase distribution diagram of the diffraction surface of the long-focal-length far-infrared optical system 100 provided in Embodiment 1 is shown. Figure 2 The horizontal axis represents the distance from the center of the diffraction plane. Figure 2 The vertical axis represents phase. (From...) Figure 2 It can be seen that the maximum phase difference of the diffraction plane is It is worth mentioning that, Figure 2 The given figure shows the actual phase distribution of the diffraction surface in Example 1. Since the phase is a periodic function of 2π, there exists a relationship... (n is an integer, therefore, it can be based on the needs.) Figure 2 The phase of the diffraction surface in Example 1 is normalized by taking the remainder of 2π to meet the actual processing requirements of the diffraction surface.

[0109] Please see Figure 3 , Figure 3 The MTF field-of-view curve of the long-focal-length far-infrared optical system 100 provided in Embodiment 1 is shown. Figure 3 The horizontal axis in the image represents the image height, and its unit is millimeters.Figure 3 The horizontal axis in the image is used to measure the field of view using image height; Figure 3 The vertical axis represents the MTF value. Figure 3 The table lists the sagittal curve S1 and meridional curve T1 for the MTF at a spatial frequency of 10 lp / mm as a function of field of view; the sagittal curve S2 and meridional curve T2 for the MTF at a spatial frequency of 21 lp / mm as a function of field of view; and the sagittal curve S3 and meridional curve T3 for the MTF at a spatial frequency of 42 lp / mm as a function of field of view. Figure 3 It can be seen that within the 1.0 field of view, the MTF is greater than 0.47, indicating that the long-focal-length far-infrared optical system has excellent imaging quality.

[0110] Please see Figure 4 , Figure 4 The field curvature diagram of the long-focal-length far-infrared optical system 100 provided in Embodiment 1 is shown. Figure 4 The horizontal axis represents the field curvature, and its unit is millimeters. Figure 4 The central vertical axis represents the field of view angle, and its unit is degrees. Figure 4 In the diagram, S1 represents the field curvature of 8-micrometer-wavelength far-infrared light in the sagittal direction, and T1 represents the field curvature of 8-micrometer-wavelength far-infrared light in the meridional direction; S2 represents the field curvature of 10-micrometer-wavelength far-infrared light in the sagittal direction, and T2 represents the field curvature of 10-micrometer-wavelength far-infrared light in the meridional direction; S3 represents the field curvature of 12-micrometer-wavelength far-infrared light in the sagittal direction, and T3 represents the field curvature of 12-micrometer-wavelength far-infrared light in the meridional direction. Figure 4 It can be seen that the maximum field curvature of the long-focal-length far-infrared optical system 100 in the sagittal direction is 0.048 mm, and the maximum field curvature of the long-focal-length far-infrared optical system 100 in the meridional direction is 0.024 mm, which meets the field curvature requirements of the excellent imaging quality standard.

[0111] Please see Figure 5 , Figure 5 The distortion diagrams of the long-focal-length far-infrared optical system 100 provided in Example 1 under far-infrared light with wavelengths of 8 micrometers, 10 micrometers, and 12 micrometers are shown. Figure 5 The horizontal axis represents distortion. Figure 5 The vertical axis is the field of view angle, because Figure 5 The three curves almost completely overlap, therefore, this embodiment does not distinguish between the three curves. Figure 5 It can be seen that the maximum distortion of the long-focal-length far-infrared optical system 100 is 0.90%, which is relatively small and meets the distortion requirements of the excellent imaging quality standard.

[0112] Example 2

[0113] Figure 6 A schematic diagram of the architecture layout of the long-focal-length far-infrared optical system 100 provided in Embodiment 2 is shown. Figure 6The mid-to-long focal length far-infrared optical system 100, along the optical axis 80 from the object plane 60 to the image plane 70, includes, in sequence: an aperture stop 40, a first aspherical lens 10, a diffractive optical element 30, a second aspherical lens 20, and a protective glass 50. The aperture stop 40 is located on the object-side surface of the first aspherical lens 10, and the diffractive optical element is a diffraction surface located on the image-side surface of the first aspherical lens 10. Some parameters of the long focal length far-infrared optical system 100 provided in Embodiment 2 are shown in Table 2-1.

[0114] Table 2-1. Partial parameters of the long-focal-length far-infrared optical system 100 provided in Example 2

[0115] Parameter Data Optical total length (TTL) 41.88 mm Maximum field angle (2ω) 16.0° F number 1.0 Effective focal length 34.7 mm Operating wavelength band Far infrared (8 μm - 12 μm)

[0116] As shown in Table 2-1, the total optical length of the long-focus far-infrared optical system 100 is 41.88 mm and the F-number of the long-focus far-infrared optical system 100 is 1.0. Therefore, the long-focus far-infrared optical system 100 has a large amount of light intake, which can ensure excellent imaging quality.

[0117] Along the optical axis 80 from the object plane 60 to the image plane 70, starting from the aperture stop 40, each surface in the long focal far-infrared optical system 100 is numbered, and the parameters of each surface are summarized to obtain Table 2-2 below.

[0118] Table 2-2. Parameters of each surface in the long-focal-length far-infrared optical system 100 provided in Example 2

[0119]

[0120] The analysis of each surface in Table 2-2 can be referred to Example 1. This example will not analyze each surface again.

[0121] Surfaces 2, 3, 4, and 5 are even-order aspherical surfaces, and their surface shapes satisfy the following relationship:

[0122]

[0123] Where Z(r) is the distance vector from the vertex of the aspherical surface at a height of r along the optical axis 80; c is the surface curvature of the aspherical surface, c = 1 / R, where R is the radius of curvature of the aspherical surface; k is the conic coefficient; A, B, C, D... are aspherical coefficients. The values ​​of k, A, B, C, D... for surfaces 2, 3, 4, and 5 can be obtained from Table 2-3.

[0124] Table 2-3. Coefficients of even-order aspherical surfaces in the long-focal-length far-infrared optical system 100 provided in Example 2

[0125]

[0126] The coefficients of even-order aspherical surfaces 2, 3, 4 and 5 can be found in Table 2-3, and will not be described in detail in this embodiment.

[0127] The diffraction plane is located on surface 3, and the phase expression of the diffraction plane is: Where ρ = r / r0, r is the radius of the diffraction surface, r0 is the normalized radius of the diffraction surface, and A i Here, represents 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 2-4.

[0128] Table 2-4. Coefficients of the diffraction surface in the long-focal-length far-infrared optical system 100 provided in Example 2

[0129]

[0130] Please see Figure 7 , Figure 7 The phase distribution diagram of the diffraction surface of the long-focal-length far-infrared optical system 100 provided in Embodiment 2 is shown. Figure 7 The horizontal axis represents the distance from the center of the diffraction plane. Figure 7 The vertical axis represents phase. (From...) Figure 7 It can be seen that the maximum phase difference of the diffraction plane is

[0131] It is worth mentioning that, Figure 7 The given figure shows the actual phase distribution of the diffraction surface in Example 2. Since the phase is a periodic function of 2π, there exists a relationship... (n is an integer, therefore, it can be based on the needs.) Figure 7 The phase of the diffraction surface in Example 2 is normalized by taking the remainder of 2π to meet the actual processing requirements of the diffraction surface.

[0132] Please see Figure 8 , Figure 8 The MTF field-of-view curve of the long-focal-length far-infrared optical system 100 provided in Embodiment 2 is shown. Figure 8 The horizontal axis in the image represents the image height, and its unit is millimeters. Figure 8 The horizontal axis in the image is used to measure the field of view using image height; Figure 8 The vertical axis represents the MTF value. Figure 8 The table lists the sagittal curve S1 and meridional curve T1 for the MTF at a spatial frequency of 10 lp / mm as a function of field of view; the sagittal curve S2 and meridional curve T2 for the MTF at a spatial frequency of 21 lp / mm as a function of field of view; and the sagittal curve S3 and meridional curve T3 for the MTF at a spatial frequency of 42 lp / mm as a function of field of view. Figure 8It can be seen that within the 1.0 field of view, the MTF is greater than 0.4, indicating that the long-focal-length far-infrared optical system has excellent imaging quality.

[0133] Please see Figure 9 , Figure 9 The field curvature diagram of the long-focal-length far-infrared optical system 100 provided in Embodiment 2 is shown. Figure 9 The horizontal axis represents the field curvature, and its unit is millimeters. Figure 9 The central vertical axis represents the field of view angle, and its unit is degrees. Figure 9 In the diagram, S1 represents the field curvature of 8-micrometer-wavelength far-infrared light in the sagittal direction, and T1 represents the field curvature of 8-micrometer-wavelength far-infrared light in the meridional direction; S2 represents the field curvature of 10-micrometer-wavelength far-infrared light in the sagittal direction, and T2 represents the field curvature of 10-micrometer-wavelength far-infrared light in the meridional direction; S3 represents the field curvature of 12-micrometer-wavelength far-infrared light in the sagittal direction, and T3 represents the field curvature of 12-micrometer-wavelength far-infrared light in the meridional direction. Figure 9 It can be seen that the maximum field curvature of the long-focal-length far-infrared optical system 100 in the sagittal direction is 0.047 mm, and the maximum field curvature of the long-focal-length far-infrared optical system 100 in the meridional direction is 0.039 mm, which meets the field curvature requirements of the excellent imaging quality standard.

[0134] Please see Figure 10 , Figure 10 The distortion diagrams of the long-focal-length far-infrared optical system 100 provided in Example 2 under far-infrared light with wavelengths of 8 micrometers, 10 micrometers, and 12 micrometers are shown. Figure 10 The horizontal axis represents distortion. Figure 10 The vertical axis is the field of view angle, because Figure 10 The three curves almost completely overlap, therefore, this embodiment does not distinguish between the three curves. Figure 10 It can be seen that the maximum distortion of the long-focal-length far-infrared optical system 100 is 0.89%, which is relatively small and meets the distortion requirements of the excellent imaging quality standard.

[0135] Example 3

[0136] Figure 11 A schematic diagram of the architecture layout of the long-focal-length far-infrared optical system 100 provided in Embodiment 3 is shown. Figure 11 The mid-to-long focal length far-infrared optical system 100, along the optical axis 80 from the object plane 60 to the image plane 70, includes, in sequence: an aperture stop 40, a first aspherical lens 10, a diffractive optical element 30, a second aspherical lens 20, and a protective glass 50. The aperture stop 40 is located on the object-side surface of the first aspherical lens 10, and the diffractive optical element is a diffraction surface located on the image-side surface of the first aspherical lens 10. Some parameters of the long focal length far-infrared optical system 100 provided in Embodiment 3 are shown in Table 3-1.

[0137] Table 3-1. Partial parameters of the long-focal-length far-infrared optical system 100 provided in Example 3

[0138] Parameter Data Optical total length (TTL) 45.72 mm Maximum field angle (2ω) 16.0° F number 1.0 Effective focal length 34.8 mm Operating wavelength band Far infrared (8 μm - 12 μm)

[0139] As shown in Table 3-1, the total optical length of the long-focus far-infrared optical system 100 is 45.72 mm and the F-number of the long-focus far-infrared optical system 100 is 1.0. Therefore, the long-focus far-infrared optical system 100 has a large amount of light intake, which can ensure excellent imaging quality.

[0140] Along the optical axis 80 from the object plane 60 to the image plane 70, starting from the aperture stop 40, each surface in the long focal far-infrared optical system 100 is numbered, and the parameters of each surface are summarized to obtain Table 3-2 below.

[0141] Table 3-2. Parameters of each surface in the long-focal-length far-infrared optical system 100 provided in Example 3

[0142]

[0143]

[0144] The analysis of each surface in Table 3-2 can be referred to Example 1. This example will not analyze each surface again.

[0145] Surfaces 2, 3, 4, and 5 are even-order aspherical surfaces, and their surface shapes satisfy the following relationship:

[0146]

[0147] Where Z(r) is the distance vector from the vertex of the aspherical surface at a height of r along the optical axis 80; c is the surface curvature of the aspherical surface, c = 1 / R, where R is the radius of curvature of the aspherical surface; k is the conic coefficient; A, B, C, D... are aspherical coefficients. The values ​​of k, A, B, C, D... for surfaces 2, 3, 4, and 5 can be obtained from Table 3-3.

[0148] Table 3-3. Coefficients of even-order aspherical surfaces in the long-focal-length far-infrared optical system 100 provided in Example 3

[0149]

[0150] The coefficients of even-order aspherical surfaces 2, 3, 4 and 5 can be found in Table 3-3, and will not be described in detail in this embodiment.

[0151] r is the radius of the diffraction surface, r0 is the normalized radius of the diffraction surface, and A i Here, represents 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 3-4.

[0152] Table 3-4. Coefficients of the diffraction surface in the long-focal-length far-infrared optical system 100 provided in Example 3. The diffraction surface is located on surface 3, and the phase expression of the diffraction surface is as follows: Where ρ=r / r0,

[0153]

[0154] Please see Figure 12 , Figure 12 The phase distribution diagram of the diffraction surface of the long-focal-length far-infrared optical system 100 provided in Embodiment 3 is shown. Figure 12 The horizontal axis represents the distance from the center of the diffraction plane. Figure 12 The vertical axis represents phase. (From...) Figure 12 It can be seen that the maximum phase difference of the diffraction plane is It is worth mentioning that, Figure 12 The given figure shows the actual phase distribution of the diffraction surface in Example 3. Since the phase is a periodic function of 2π, there exists a relationship... (n is an integer, therefore, it can be based on the needs.) Figure 12 The phase of the diffraction surface in Example 3 is normalized by taking the remainder of 2π to meet the actual processing requirements of the diffraction surface.

[0155] Please see Figure 13 , Figure 13 The MTF field-of-view curve of the long-focal-length far-infrared optical system 100 provided in Embodiment 3 is shown. Figure 13 The horizontal axis in the image represents the image height, and its unit is millimeters. Figure 13 The horizontal axis in the image is used to measure the field of view using image height; Figure 13 The vertical axis represents the MTF value. Figure 13 The table lists the sagittal curve S1 and meridional curve T1 for the MTF at a spatial frequency of 10 lp / mm as a function of field of view; the sagittal curve S2 and meridional curve T2 for the MTF at a spatial frequency of 21 lp / mm as a function of field of view; and the sagittal curve S3 and meridional curve T3 for the MTF at a spatial frequency of 42 lp / mm as a function of field of view. Figure 13 It can be seen that within the 1.0 field of view, the MTF is greater than 0.39, indicating that the long-focal-length far-infrared optical system has excellent imaging quality.

[0156] Please see Figure 14 , Figure 14 The field curvature diagram of the long-focal-length far-infrared optical system 100 provided in Embodiment 3 is shown. Figure 14 The horizontal axis represents the field curvature, and its unit is millimeters. Figure 14 The central vertical axis represents the field of view angle, and its unit is degrees. Figure 14In the diagram, S1 represents the field curvature of 8-micrometer-wavelength far-infrared light in the sagittal direction, and T1 represents the field curvature of 8-micrometer-wavelength far-infrared light in the meridional direction; S2 represents the field curvature of 10-micrometer-wavelength far-infrared light in the sagittal direction, and T2 represents the field curvature of 10-micrometer-wavelength far-infrared light in the meridional direction; S3 represents the field curvature of 12-micrometer-wavelength far-infrared light in the sagittal direction, and T3 represents the field curvature of 12-micrometer-wavelength far-infrared light in the meridional direction. Figure 14 It can be seen that the maximum field curvature of the long-focal-length far-infrared optical system 100 in the sagittal direction is 0.044 mm, and the maximum field curvature of the long-focal-length far-infrared optical system 100 in the meridional direction is 0.068 mm, which meets the field curvature requirements of the excellent imaging quality standard.

[0157] Please see Figure 15 , Figure 15 The distortion diagrams of the long-focal-length far-infrared optical system 100 provided in Example 4 under far-infrared light with wavelengths of 8 micrometers, 10 micrometers, and 12 micrometers are shown. Figure 15 The horizontal axis represents distortion. Figure 15 The vertical axis is the field of view angle, because Figure 15 The three curves almost completely overlap, therefore, this embodiment does not distinguish between the three curves. Figure 15 It can be seen that the maximum distortion of the long-focal-length far-infrared optical system 100 is 0.09%, which is relatively small and meets the distortion requirements of the excellent imaging quality standard.

[0158] Example 4

[0159] Figure 16 A schematic diagram of the architecture layout of the long-focal-length far-infrared optical system 100 provided in Embodiment 4 is shown. Figure 16 The mid-to-long focal length far-infrared optical system 100, along the optical axis 80 from the object plane 60 to the image plane 70, includes, in sequence: an aperture stop 40, a first aspherical lens 10, a diffractive optical element 30, a second aspherical lens 20, and a protective glass 50. The aperture stop 40 is located on the object-side surface of the first aspherical lens 10, and the diffractive optical element is a diffraction surface located on the image-side surface of the first aspherical lens 10. Some parameters of the long focal length far-infrared optical system 100 provided in Embodiment 4 are shown in Table 4-1.

[0160] Table 4-1. Partial parameters of the long-focal-length far-infrared optical system 100 provided in Example 4

[0161] Parameter Data Optical total length (TTL) 40.01 mm Maximum field angle (2ω) 16.0° F number 0.9 Effective focal length 34.8 mm Operating wavelength band Far infrared (8 μm - 12 μm)

[0162] As shown in Table 4-1, the total optical length of the long-focus far-infrared optical system 100 is 40.01 mm and the F-number of the long-focus far-infrared optical system 100 is 0.9. Therefore, the long-focus far-infrared optical system 100 has a large amount of light intake, which can ensure excellent imaging quality.

[0163] Along the optical axis 80 from the object plane 60 to the image plane 70, starting from the aperture stop 40, each surface in the long focal far-infrared optical system 100 is numbered, and the parameters of each surface are summarized to obtain Table 4-2 below.

[0164] Table 4-2. Parameters of each surface in the long-focal-length far-infrared optical system 100 provided in Example 4

[0165]

[0166] The analysis of each surface in Table 4-2 can be referred to Example 1. This example will not analyze each surface again.

[0167] Surfaces 2, 3, 4, and 5 are even-order aspherical surfaces, and their surface shapes satisfy the following relationship:

[0168]

[0169] Where Z(r) is the distance vector from the vertex of the aspherical surface at a height of r along the optical axis 80; c is the surface curvature of the aspherical surface, c = 1 / R, where R is the radius of curvature of the aspherical surface; k is the conic coefficient; A, B, C, D... are aspherical coefficients. The values ​​of k, A, B, C, D... for surfaces 2, 3, 4, and 5 can be obtained from Table 4-3.

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

[0171]

[0172] The coefficients of even-order aspherical surfaces 2, 3, 4 and 5 can be found in Table 4-3, and will not be described in detail in this embodiment.

[0173] The diffraction plane is located on surface 3, and the phase expression of the diffraction plane is: Where ρ = r / r0, r is the radius of the diffraction surface, r0 is the normalized radius of the diffraction surface, and A i Here, represents 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 4-4.

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

[0175]

[0176] Please see Figure 17 , Figure 17 The phase distribution diagram of the diffraction surface of the long-focal-length far-infrared optical system 100 provided in Embodiment 4 is shown.Figure 17 The horizontal axis represents the distance from the center of the diffraction plane. Figure 17 The vertical axis represents phase. (From...) Figure 17 It can be seen that the maximum phase difference of the diffraction plane is It is worth mentioning that, Figure 17 The given figure shows the actual phase distribution of the diffraction surface in Example 4. Since the phase is a periodic function of 2π, there exists a relationship... (n is an integer, therefore, it can be based on the needs.) Figure 17 The phase of the diffraction surface in Example 4 is normalized by taking the remainder of 2π to meet the actual processing requirements of the diffraction surface.

[0177] Please see Figure 18 , Figure 18 The MTF field-of-view curve of the long-focal-length far-infrared optical system 100 provided in Embodiment 4 is shown. Figure 18 The horizontal axis in the image represents the image height, and its unit is millimeters. Figure 18 The vertical axis represents the MTF value. Figure 18 The table lists the sagittal curve S1 and meridional curve T1 for the MTF at a spatial frequency of 10 lp / mm as a function of field of view; the sagittal curve S2 and meridional curve T2 for the MTF at a spatial frequency of 21 lp / mm as a function of field of view; and the sagittal curve S3 and meridional curve T3 for the MTF at a spatial frequency of 42 lp / mm as a function of field of view. Figure 19 It can be seen that within the 1.0 field of view, the MTF is greater than 0.42, indicating that the long-focal-length far-infrared optical system has excellent imaging quality.

[0178] Please see Figure 19 , Figure 19 The field curvature diagram of the long-focal-length far-infrared optical system 100 provided in Embodiment 4 is shown. Figure 19 The horizontal axis represents the field curvature, and its unit is millimeters. Figure 19 The central vertical axis represents the field of view angle, and its unit is degrees, i.e., Figure 19 The horizontal axis in the image is used to measure the field of view using image height. Figure 19 In the diagram, S1 represents the field curvature of 8-micrometer-wavelength far-infrared light in the sagittal direction, and T1 represents the field curvature of 8-micrometer-wavelength far-infrared light in the meridional direction; S2 represents the field curvature of 10-micrometer-wavelength far-infrared light in the sagittal direction, and T2 represents the field curvature of 10-micrometer-wavelength far-infrared light in the meridional direction; S3 represents the field curvature of 12-micrometer-wavelength far-infrared light in the sagittal direction, and T3 represents the field curvature of 12-micrometer-wavelength far-infrared light in the meridional direction. Figure 20 It can be seen that the maximum field curvature of the long-focal-length far-infrared optical system 100 in the sagittal direction is 0.089 mm, and the maximum field curvature of the long-focal-length far-infrared optical system 100 in the meridional direction is 0.098 mm, which meets the field curvature requirements of the excellent imaging quality standard.

[0179] Please see Figure 20, Figure 20 The distortion diagrams of the long-focal-length far-infrared optical system 100 provided in Example 4 under far-infrared light with wavelengths of 8 micrometers, 10 micrometers, and 12 micrometers are shown. Figure 20 The horizontal axis represents distortion. Figure 20 The vertical axis is the field of view angle, because Figure 20 The three curves almost completely overlap, therefore, this embodiment does not distinguish between the three curves. ​ It can be seen that the maximum distortion of the long-focal-length far-infrared optical system 100 is 0.91%, which is relatively small and meets the distortion requirements of the excellent imaging quality standard.

[0180] After summarizing the parameters of the long-focal-length far-infrared optical system 100 provided in the above four embodiments, Table 5 is shown below. The table 5 is mainly used to illustrate that the conditions satisfied by the long-focal-length far-infrared optical system 100 provided in this application have all been verified and supported by experiments.

[0181] Table 5. Parameters of the long-focal-length far-infrared optical system 100 provided in each embodiment

[0182]

[0183]

[0184] This application also provides a long-focal-length far-infrared optical lens (not shown), which includes an imaging detector (not shown) and the aforementioned long-focal-length far-infrared optical system 100. The imaging detector is located on the image plane 70 of the long-focal-length far-infrared optical system 100, and includes, but is not limited to, CMOS (Complementary Metal Oxide Semiconductor) and CCD (Charge Coupled Device). The specific architecture of the long-focal-length far-infrared optical system 100 can be referred to above, and will not be repeated here.

[0185] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the utility models disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this application are indicated by the appended claims.

Claims

1. A long-focal-length far-infrared optical system, characterized in that, The long-focal-length far-infrared optical system includes: The first aspherical lens has a positive optical power, and both the object side and the image side of the first aspherical lens are convex towards the object side. The second aspherical lens has a positive optical power. A diffractive optical element is disposed on the image-side surface of the first aspherical lens; The first aspherical lens and the second aspherical lens are arranged sequentially from the object side to the image side along the optical axis.

2. The long-focal-length far-infrared optical system according to claim 1, characterized in that, The long-focal-length far-infrared optical system satisfies: Where f1 is the focal length of the first aspherical lens and f2 is the focal length of the second aspherical lens.

3. The long-focal-length far-infrared optical system according to claim 1, characterized in that, The long-focal-length far-infrared optical system satisfies: Among them, D 11 D is the effective diameter of the object-side surface of the first aspherical lens. 21 The effective diameter of the object-side surface of the second aspherical lens is denoted as .

4. The long-focal-length far-infrared optical system according to claim 1, characterized in that, The long-focal-length far-infrared optical system satisfies: Wherein, L1 is the distance on the optical axis between the object-side surface of the first aspherical lens and the object-side surface of the second aspherical lens, L2 is the distance on the optical axis between the image-side surface of the second aspherical lens and the image plane of the long-focal-length far-infrared optical system, and FOV is the maximum field of view of the long-focal-length far-infrared optical system.

5. The long-focal-length far-infrared optical system according to claim 1, characterized in that, The long-focal-length far-infrared optical system satisfies: Where T1 is the center thickness of the first aspherical lens, T2 is the center thickness of the second aspherical lens, and D... 11 D is the effective diameter of the object-side surface of the first aspherical lens. 21 The effective diameter of the object-side surface of the second aspherical lens is denoted as .

6. The long-focal-length far-infrared optical system according to claim 1, characterized in that, The long-focal-length far-infrared optical system satisfies: Among them, D 11 f1 is the effective diameter of the object side surface of the first aspherical lens, and f1 is the focal length of the first aspherical lens.

7. The long-focal-length far-infrared optical system according to claim 1, characterized in that, The long-focal-length far-infrared optical system satisfies: Among them, D 11 ImgH is the effective diameter of the object side surface of the first aspherical lens, ImgH is the radius of the imaging area of ​​the long-focal far-infrared optical system on the image plane corresponding to the maximum half field of view, and Fno is the aperture number of the long-focal far-infrared optical system.

8. The long-focal-length far-infrared optical system according to claim 1, characterized in that, The long-focal-length far-infrared optical system satisfies: Wherein, R1 is the radius of curvature of the object side of the first aspherical lens, R2 is the radius of curvature of the image side of the first aspherical lens, R3 is the radius of curvature of the object side of the second aspherical lens, and R4 is the radius of curvature of the image side of the second aspherical lens.

9. The long-focal-length far-infrared optical system according to claim 1, characterized in that, The diffractive optical element satisfies: The maximum phase difference of the diffractive optical element.

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

Images