Long-wave infrared athermalization wide-angle temperature measurement lens

Abstract

The long-wave infrared athermalization wide-angle temperature measurement lens comprises a first lens, a second lens, a third lens, a diaphragm STOP, a fourth lens and an optical filter which are sequentially connected along an optical axis from an object side to an image side in an optical path mode. The object-side surface of the first lens is a convex surface, and the image-side surface is a concave surface. The object side surface of the second lens is a convex surface, and the image side surface is a concave surface; the object side surface of the third lens is a concave surface, and the image side surface is a convex surface; the fourth lens element has a convex object-side surface and a convex image-side surface. By adopting the optimized first to fourth lenses, the number of used lenses is reduced, the cost is reduced, the horizontal visual angle is ensured to reach 90 degrees, and the number of apertures is less than or equal to 1.0. In addition, the total optical length is smaller than or equal to 50 mm, the structure is designed to be light, and the purpose of miniaturization is achieved. Meanwhile, the advantages of optical athermalization and active and passive focusing compensation of an electric tuning system are utilized, and high imaging quality is obtained under the complex environment temperature.

Description

Technical Field

[0001] The present application relates to the technical field of infrared temperature measurement thermal imagers, and in particular to a long-wave infrared athermal wide-angle temperature measurement lens. Background Art

[0002] Infrared temperature measurement thermal imagers can realize non-contact long-distance temperature measurement and fault detection. They are safe and accurate, efficient and time-saving, the results are simple and intuitive, and they can work around the clock. They are widely used in industrial inspection, temperature monitoring in the petrochemical industry, power equipment monitoring, and fire hazard monitoring in key occasions.

[0003] The thermal imaging temperature measurement lens is the core component of the infrared temperature measurement thermal imager. Its imaging performance directly affects the temperature measurement accuracy and consistency of the infrared temperature measurement thermal imager. At present, domestic developers of online and handheld temperature measurement thermal imagers all use standard fixed-focus temperature measurement lenses (horizontal field of view 6° / 12° / 24° / 48°) to achieve temperature measurement. The temperature measurement accuracy can reach ±2°C or ±2% (national standard), which can basically meet the needs of the low-end industrial temperature measurement market.

[0004] However, in the field of temperature measurement of infrared imaging, due to the limitation of detection distance, the thermal radiation field of ambient temperature will affect the lens. Changes in ambient temperature will cause changes in the refractive index of the lens material. Thermal expansion and contraction of the lens barrel material will also change the air gap of the lens, causing changes in optical focal length and displacement of the optimal position of the image plane, resulting in reduced contrast and brightness, and ultimately a decline in image quality.

[0005] At the same time, the existing infrared imaging lenses for temperature measurement still have the following problems: high cost and small temperature measurement field of view, which restricts the application scope of infrared imaging lenses for temperature measurement.

[0006] For example, CN 201811617398.8 discloses a long-wave infrared pinhole wide-angle temperature measurement lens and an imaging method thereof, wherein the lens comprises: each lens set for imaging after the light passes through the meniscus positive lens A1, meniscus positive lens A2, meniscus positive lens A3, meniscus positive lens B1, and meniscus positive lens B2 from left to right in sequence. The structure requires the use of at least 5 lenses, resulting in an increase in the overall size, an increase in manufacturing costs, and a decrease in light transmittance, which affects the imaging quality. Moreover, the imaging of this lens cannot avoid the adverse effects of ambient temperature on the imaging quality. At the same time, the lens also has the problem of too long total optical length (total optical length TTL≤72mm), resulting in a low overall integration of the lens, which cannot meet the use requirements of miniaturization. At the same time, the working performance of the lens at different temperatures has not been tested, and its actual normal operating temperature range cannot be determined.

[0007] The information disclosed in the background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0008] In response to the above-mentioned technical problems, the present application provides a long-wave infrared athermal wide-angle temperature measurement lens, the focal length of which can reach 6 mm; the aperture F number is 1.0; the working band is 8 to 12 μm; the resolution of the adaptable detector is 640×480: 640 pixels horizontally, 480 pixels vertically, and the pixel size is 17 μm; the field of view angle can reach 91° (horizontal) × 75° (vertical); and the working environment temperature can be between -40°C and +70°C.

[0009] The present application provides a long-wave infrared athermal wide-angle temperature measurement lens, comprising: a first lens, a second lens, a third lens, an aperture STOP, a fourth lens, and a filter, which are optically connected in sequence along an optical axis from an object side to an image side;

[0010] The object side surface of the first lens is convex, and the image side surface is concave;

[0011] The object side surface of the second lens is convex, and the image side surface is concave;

[0012] The object side surface of the third lens is concave, and the image side surface is convex;

[0013] The object side surface of the fourth lens is convex, and the image side surface is convex

[0014] This lens meets the following requirements:

[0015] -4.0 <f1 / f<-3.0,

[0016] -6.0 <f2 / f<-5.0,

[0017] 3.0 <f3 / f<4.0,

[0018] 1.0 <f4 / f<2.0,

[0019] Wherein, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, and f is the focal length of the long-wave infrared athermalized wide-angle temperature measurement lens;

[0020] Nd1≥4.0, Tce1≥5×10 -6 ,

[0021] Nd2≥4.0, Tce2≥5×10 -6 ,

[0022] Nd3≥4.0, Tce3≥5×10 -6,

[0023] Nd4≥2.7, Tce4≥2×10 -5 ,

[0024] Among them, Nd1 is the refractive index of the first lens, Tce1 is the thermal expansion coefficient of the first lens; Nd2 is the refractive index of the second lens, Tce2 is the thermal expansion coefficient of the second lens; Nd3 is the refractive index of the third lens, Tce3 is the thermal expansion coefficient of the third lens; Nd4 is the refractive index of the fourth lens, Tce4 is the thermal expansion coefficient of the fourth lens.

[0025] Preferably, the lens satisfies:

[0026] D1≤40mm,20mm <R11<30mm,10mm<R12<20mm,

[0027] 3.0mm <CT1<4.0mm,7.0mm<A1<8.0mm,D2≤25mm,10mm<R21<20mm,10mm<R22<20mm,1.5mm<CT2<2.5mm,

[0028] 6.0mm <A2<7.0mm,D3≤20mm,-40mm<R31<-30mm,-30mm<R32<-20mm,3.0mm<CT3<4.0mm,8.0mm<A3<11.0mm,D4≤20mm,30mm<R41<40mm,-50mm<R42<-40mm,4.0mm<CT4<6.0mm,8.0mm<A4<11.0mm;

[0029] Wherein, D1 is the aperture value of the first lens, R11 is the curvature radius of the object side surface of the first lens, R12 is the curvature radius of the image side surface of the first lens, CT1 is the center thickness of the first lens, A1 is the air gap from the first lens to the second lens, R21 is the curvature radius of the object side surface of the second lens, R22 is the curvature radius of the image side surface of the second lens, CT2 is the center thickness of the second lens, A2 is the air gap from the second lens to the third lens, R31 is the curvature radius of the object side surface of the third lens, R32 is the curvature radius of the image side surface of the third lens, CT3 is the center thickness of the third lens, A3 is the air gap from the third lens to the fourth lens, R41 is the curvature radius of the object side surface of the fourth lens, R42 is the curvature radius of the image side surface of the fourth lens, CT4 is the center thickness of the fourth lens, and A4 is the air gap from the fourth lens to the filter.

[0030] Preferably, the object side of the first lens is a spherical surface with a curvature radius R=28.6 mm and a thickness d=3 mm.

[0031] The image side surface of the first lens is an even aspheric surface with a curvature radius of R = 18.5 mm and a thickness of d = 7.5 mm;

[0032] The object side of the second lens is a spherical surface with a curvature radius of R = 17.5 mm and a thickness of d = 2 mm;

[0033] The image side surface of the second lens is an even aspheric surface with a curvature radius of R = 13.7 mm and a thickness of d = 6.6 mm;

[0034] The object side of the third lens is an even aspheric surface with a curvature radius of R = -31.6mm and a thickness of d = 3mm;

[0035] The image side of the third lens is a spherical surface with a curvature radius of R = -22.6mm and a thickness of d = 10mm;

[0036] The object side of the fourth lens is a spherical surface with a curvature radius of R=34.8 mm and a thickness of d=5 mm;

[0037] The image side surface of the fourth lens is a binary diffraction surface with a curvature radius of R=-47.7mm and a thickness of d=10mm.

[0038] Preferably, the refractive index of the first lens, the second lens, and the third lens = 4.0Nd;

[0039] The refractive index of the fourth lens=2.77Nd.

[0040] Preferably, the diffraction surface coefficient of the image side surface L42 of the fourth lens is: normalized radius

[0041] 11mm; phase coefficient H1-63.37; phase coefficient H223.79; phase coefficient H3-13.31.

[0042] Preferably, the optical parameters of the lens are: lens focal length f is 6 mm; aperture F number is 1.0; working band is 8 to 12 μm; adapted detector resolution is 640×480, 17 μm; field of view angle is 91° (horizontal) × 75° (vertical); working temperature is -40°C to +70°C.

[0043] Preferably, the total optical length of the lens is less than or equal to 50 mm; the imaging distortion is less than 12%; and the field curvature is less than ±0.1.

[0044] Preferably, it comprises: a focusing assembly and a fixed installation assembly; the focusing assembly comprises: a fourth lens and a focusing lens frame; the fixed installation assembly comprises: a first lens, a second lens, a third lens, and a lens barrel; the first lens, the second lens, the third lens, and the aperture STOP are fixedly installed in the lens barrel in sequence;

[0045] The fourth lens is installed in a focusing frame; the focusing frame is arranged to perform reciprocating focusing motion along the axial direction of the lens barrel.

[0046] Preferably, it comprises: a motor; the motor is mounted on the outer wall of the lens barrel and is drivingly connected to the focusing lens frame.

[0047] Preferably, the filter is arranged in the long-wave uncooled detector and connected to the optical path of the fourth lens; IMA is the image plane of the long-wave uncooled detector.

[0048] The beneficial effects of this application include:

[0049] 1) The long-wave infrared athermal wide-angle temperature measurement lens provided by the present application adopts the optimized first to fourth lenses, reduces the number of lenses used, reduces the cost, ensures that the horizontal viewing angle reaches 90 degrees, and the aperture number is less than or equal to 1.0. In addition, the total optical length is less than or equal to 50mm, and the structure is lightweight, achieving the goal of miniaturization. At the same time, by taking advantage of the optical athermalization and the active and passive focusing compensation of the electric adjustment system, a higher imaging quality is obtained under complex ambient temperatures.

[0050] 2) The long-wave infrared athermal wide-angle temperature measurement lens provided by the present application has the following optical parameter performances: lens focal length f is 6mm; aperture F number is 1.0; working band is 8-12μm; adapted detector resolution is 640×480, pixel size is 17μm; field of view is 91° (horizontal) × 75° (vertical); working temperature is -40℃~+70℃; imaging distortion is less than 12%; field curvature is less than ±0.1. The imaging performance is good and the working temperature range is wide. In this temperature environment, the imaging result is not affected by the ambient temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 A schematic diagram of the optical system of a long-wave infrared athermal wide-angle temperature measurement lens according to at least one embodiment of the present application.

[0052] Figure 2 A schematic structural diagram of a long-wave infrared athermal wide-angle temperature measurement lens according to at least one embodiment of the present application.

[0053] Figure 3 To have Figure 1 Relative illumination of the long-wave infrared athermalized wide-angle temperature measurement lens of the structure shown.

[0054] Figure 4 To have Figure 1 The field curvature / distortion result diagram of the long-wave infrared athermalized wide-angle temperature measurement lens of the structure shown; a) is the field curvature result; b) is the distortion result;

[0055] Figure 5 To have Figure 1MTF (diffraction modulation transfer function) curve of the long-wave infrared athermal wide-angle temperature measurement lens of the structure shown at room temperature (20°C).

[0056] Figure 6 To have Figure 1 MTF (diffraction modulation transfer function) curve of the long-wave infrared athermal wide-angle temperature measurement lens with the structure shown at low temperature (-40°C).

[0057] Figure 7 To have Figure 1 MTF (diffraction modulation transfer function) curve of the long-wave infrared athermal wide-angle temperature measurement lens with the structure shown at high temperature (70°C).

[0058] Figures 5 to 7 The MTF represents the theoretical imaging quality of the entire system, because temperature changes cause the lens curvature radius and air space to change, and the final imaging quality changes accordingly.

[0059] Figure 8 To have Figure 1 Standard spot diagram of the long-wave infrared athermalized wide-angle temperature measurement lens of the structure shown at room temperature (20°C).

[0060] Fig. 9 To have Figure 1 Standard spot diagram of the long-wave infrared athermalized wide-angle temperature measurement lens of the structure shown at low temperature (-40℃).

[0061] Fig.10 To have Figure 1 Standard spot diagram of the long-wave infrared athermalized wide-angle temperature measurement lens of the structure shown at high temperature (70°C).

[0062] Fig.11 A schematic diagram of a cam barrel of a long-wave infrared athermal wide-angle temperature measurement lens according to at least one embodiment of the present application.

[0063] Fig.12 A schematic diagram of a gear barrel of a long-wave infrared athermal wide-angle temperature measurement lens according to at least one embodiment of the present application. DETAILED DESCRIPTION

[0064] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0065] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0066] The technical means that are not described in detail in this application and are not used to solve the technical problems of this application are all set according to the common knowledge in the field, and can be implemented in a variety of common knowledge settings.

[0067] See also Figures 1 to 12 The long-wave infrared athermal wide-angle temperature measurement lens provided by the present application includes: a first lens, a second lens, a third lens, an aperture STOP, a fourth lens, and a filter, which are optically connected in sequence along the optical axis from the object side to the image side.

[0068] The object side surface of the first lens is convex, and the image side surface is concave; the object side surface of the second lens is convex, and the image side surface is concave; the object side surface of the third lens is concave, and the image side surface is convex; the object side surface of the fourth lens is convex, and the image side surface is convex.

[0069] In addition, the long-wave infrared athermal wide-angle temperature measurement lens involved in this embodiment meets the requirement of configuring an aperture between the third lens and the fourth lens, which is convenient for controlling the aperture number F of the lens to reach 1.0, and can reduce the entry of stray light from the lens. The filter is set in the long-wave uncooled detector and connected to the optical path of the fourth lens; IMA is the image plane of the long-wave uncooled detector.

[0070] By adopting the design of the first lens to the fourth lens, the number of lenses used is reduced, the production cost is reduced, and the simplified lens combination can ensure that the horizontal viewing angle reaches more than 90° and the aperture number is less than or equal to 1.0. In addition, the total optical length of the lens is less than or equal to 50mm, realizing a lightweight structural design, and the total weight of the lens is less than 120g, achieving the goal of miniaturization of the lens. At the same time, by utilizing the advantages of optical athermalization and active and passive focus compensation of the electric adjustment system, higher imaging quality can be obtained under complex ambient temperatures. "Total optical length" refers to the distance from the first object side surface of the object side lens in the lens to the final imaging surface.

[0071] In a specific embodiment, the optical system lens assembly is installed in a lens barrel, the pressing ring 1 fixes the first lens in the lens barrel, and the pressing ring 2 fixes the second lens and the third lens in the lens barrel.

[0072] A spacer is set between the second lens and the third lens to separate them, and the pressure ring 3 fixes the fourth lens in the focusing frame. The motor is installed on the outer wall of the lens and is connected to the cam barrel drive. By driving the cam barrel to rotate, the cam barrel drives the focusing frame of the fourth lens to move back and forth along the central axis of the barrel to realize the active focusing function of the lens. The aperture STOP is installed on the end face of the barrel so that the aperture STOP is set between the third lens and the fourth lens.

[0073] The first lens is fixed in the lens barrel by the pressing ring 1, the second lens and the third lens are fixed in the lens barrel by the pressing ring 2, wherein the second lens and the third lens are separated by the spacer ring, and the fourth lens is fixed in the lens frame by the pressing ring 3. The motor drives the cam barrel to rotate, and the cam barrel drives the lens frame to move back and forth along the lens barrel.

[0074] As shown in the attached figure Fig.11 and Fig.12 As shown, topology optimization is used to lightweight the main lens barrel and cam barrel, which effectively controls the overall quality of the lens. By taking advantage of optical athermalization and the electric adjustment system, the lens can perform passive and active focusing compensation under a certain temperature environment, thereby improving the overall comprehensive performance of the lens and enabling it to adapt to more complex temperature measurement environments.

[0075] The long-wave infrared athermalized wide-angle temperature measurement lens involved in this embodiment meets the following requirements:

[0076] -4.0 <f1 / f<-3.0,

[0077] -6.0 <f2 / f<-5.0,

[0078] 3.0 <f3 / f<4.0,

[0079] 1.0 <f4 / f<2.0,

[0080] Among them, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, and f is the focal length of the long-wave infrared athermal wide-angle temperature measurement lens.

[0081] At the same time, the long-wave infrared athermalized wide-angle temperature measurement lens involved in this embodiment satisfies:

[0082] Nd1≥4.0, Tce1≥5×10 -6 ,

[0083] Nd2≥4.0, Tce2≥5×10 -6 ,

[0084] Nd3≥4.0, Tce3≥5×10 -6 ,

[0085] Nd4≥2.7, Tce4≥2×10-5 ,

[0086] Among them, Nd1 is the refractive index of the first lens, Tce1 is the thermal expansion coefficient of the first lens; Nd2 is the refractive index of the second lens, Tce2 is the thermal expansion coefficient of the second lens; Nd3 is the refractive index of the third lens, Tce3 is the thermal expansion coefficient of the third lens; Nd4 is the refractive index of the fourth lens, Tce4 is the thermal expansion coefficient of the fourth lens.

[0087] By using the above parameters to control the thermal expansion coefficient of the lens, the lens can be made optically athermal, reducing the impact of high and low temperature environments on the lens. This ensures that the imaging performance of the lens is not affected by changes in ambient temperature, maintaining image clarity and stability.

[0088] At the same time, the long-wave infrared athermalized wide-angle temperature measurement lens involved in this embodiment satisfies:

[0089] D1≤40mm,

[0090] 20mm <R11<30mm,

[0091] 10mm <R12<20mm,

[0092] 3.0mm <CT1<4.0mm,

[0093] 7.0mm <A1<8.0mm,

[0094] D2≤25mm,

[0095] 10mm <R21<20mm,

[0096] 10mm <R22<20mm,

[0097] 1.5mm <CT2<2.5mm,

[0098] 6.0mm <A2<7.0mm,

[0099] D3≤20mm,

[0100] -40mm <R31<-30mm,

[0101] -30mm <R32<-20mm,

[0102] 3.0mm <CT3<4.0mm,

[0103] 8.0mm <A3<11.0mm,

[0104] D4≤20mm,

[0105] 30mm <R41<40mm,

[0106] -50mm <R42<-40mm,

[0107] 4.0mm <CT4<6.0mm,

[0108] 8.0mm <A4<11.0mm,

[0109] Where D1 is the aperture value of the first lens,

[0110] R11 is the radius of curvature of the object side of the first lens,

[0111] R12 is the radius of curvature of the image side of the first lens,

[0112] CT1 is the center thickness of the first lens,

[0113] A1 is the air gap from the first lens to the second lens,

[0114] R21 is the radius of curvature of the object side of the second lens,

[0115] R22 is the radius of curvature of the image side of the second lens,

[0116] CT2 is the center thickness of the second lens,

[0117] A2 is the air space between the second lens and the third lens.

[0118] R31 is the radius of curvature of the object side of the third lens,

[0119] R32 is the curvature radius of the image side of the third lens.

[0120] CT3 is the center thickness of the third lens,

[0121] A3 is the air space between the third lens and the fourth lens.

[0122] R41 is the radius of curvature of the object side of the fourth lens,

[0123] R42 is the curvature radius of the image side of the fourth lens,

[0124] CT4 is the center thickness of the fourth lens,

[0125] A4 is the air space from the fourth lens to the filter.

[0126] In the long-wave infrared athermal wide-angle temperature measurement lens involved in this embodiment, through the parameter design of the first lens, the second lens, the third lens and the fourth lens, the lens aperture is effectively controlled to be less than 40 mm, the height of the incident light in the edge field of view is increased to 38.5 mm, and imaging with a horizontal field of view angle of 90° is achieved.

[0127] In a specific embodiment, the object side surface of the first lens is a spherical surface, and the image side surface is an even-order aspherical surface; the object side surface of the second lens is a spherical surface, and the image side surface is an even-order aspherical surface; the object side surface of the third lens is an even-order aspherical surface, and the image side surface is a spherical surface; the object side surface of the fourth lens is a spherical surface, and the image side surface is a binary diffraction surface and an even-order aspherical surface.

[0128] The parameters of each lens are shown in Tables 1 to 3.

[0129] Table 1

[0130]

[0131] Table 2

[0132]

[0133] Among them, L12 is the image side surface of the first lens, L22 is the image side surface of the second lens, L31 is the object side surface of the third lens, L12 is the image side surface of the fourth lens, and L42 is the image side surface of the fourth lens. There are four even-order aspheric surfaces in total, and K to A14 are the even-order aspheric coefficients of each lens as shown in Table 1.

[0134] Table 3

[0135]

[0136] Among them, H1-H3 are the diffraction surface phase coefficients of the fourth lens.

[0137] In the long-wave infrared athermal wide-angle temperature measurement lens involved in this embodiment, through the aspherical and diffraction surface parameter design of the first lens, the second lens, the third lens and the fourth lens, phase differences such as spherical aberration, field curvature, distortion, etc. can be effectively corrected to further improve the imaging quality.

[0138] With Figure 1 The relative illumination imaging results of the lens with the structure shown and the above performance parameters are as follows Figure 3 As shown in the figure, it can be seen that when the millimeter value of the half field image height of the lens in the Y direction is in the range of 0 to 7.2 mm, the relative illumination is greater than 0.9, indicating that the imaging quality of the lens is good and the illumination is uniform.

[0139] With Figure 1 The field curvature / distortion results of the lens with the structure shown and the above performance parameters are as follows Figure 4 As shown in a) to b), the test conditions are: the ambient temperature is equal to 20°C; it can be seen from the figure that the field curvature of the lens is less than ±0.1, and the distortion is less than 12%, indicating that the optical distortion of the lens is effectively controlled.

[0140] With Figure 1The MTF (diffraction modulation transfer function) curve of the lens with the structure shown and the above performance parameter requirements at room temperature (20°C) is as follows Figure 5 As shown in the figure, when the spatial frequency of the lens is between 0 and 30 mm / mm line pairs, the modulus of the optical transfer function is greater than or equal to 0.45, which is close to the diffraction limit. This shows that the image of the lens is uniform and the imaging quality is excellent.

[0141] With Figure 1 The MTF (diffraction modulation transfer function) curve of the lens with the structure shown and the above performance parameter requirements at low temperature (-40°C) is as follows Figure 6 As shown in the figure, when the spatial frequency of the lens is between 0 and 30 line pairs per millimeter, the modulus of the optical transfer function is greater than or equal to 0.35, which means that the image of the lens is uniform and the imaging quality is good.

[0142] With Figure 1 The MTF (diffraction modulation transfer function) curve of the lens with the structure shown and the above performance parameter requirements at high temperature (70°C) is as follows Figure 7 As shown in the figure, when the spatial frequency of the lens is between 0 and 30 mm / mm line pairs, the modulus of the optical transfer function is greater than or equal to 0.3, which means that the image of the lens is uniform and the imaging quality is good.

[0143] With Figure 1 The standard point diagram of the lens with the structure shown and the above performance parameters at room temperature (20°C) is as follows Figure 8 As shown in the figure, it can be seen that the energy distribution of the image points is dense and uniform, which means that the energy passing through the lens is concentrated and the image quality is uniform.

[0144] With Figure 1 The standard spot diagram of the lens with the structure shown and the above performance parameters at low temperature (-40℃) is as follows: Fig. 9 As shown in the figure, it can be seen that the energy distribution of the image points is dense and uniform, which means that the energy passing through the lens is concentrated and the image quality is uniform.

[0145] With Figure 1 The standard spot diagram of the lens with the structure shown and the above performance parameters at high temperature (70°C) is as follows: Fig.10 As shown in the figure, it can be seen that the energy distribution of the image points is dense and uniform, which means that the energy passing through the lens is concentrated and the image quality is uniform.

[0146] In summary, this embodiment can achieve the optical parameters shown in Table 4. For specific image quality evaluation indicators, see Figures 3 to 10 .

[0147] Table 4

[0148] Optical parameter name Lens performance parameter values Lens focal length f 6mm Aperture F number 1.0 Working band 8~12μm Adapt detector resolution 640×480 17μm Field of view 91°(horizontal)×75°(vertical) Operating temperature -40℃～+70℃

[0149] The long-wave infrared athermal wide-angle temperature measurement lens of the embodiment of the present application adopts the optimized design of the first lens to the fourth lens, which reduces the number of lenses used, reduces costs, ensures that the horizontal viewing angle reaches 90 degrees, and the aperture number is less than or equal to 1.0. In addition, the total optical length is less than or equal to 50mm, the structure is lightweight, and the total weight is less than 120g, achieving the goal of miniaturization. At the same time, by taking advantage of the optical athermalization and the active and passive focus compensation of the electric adjustment system, a higher imaging quality is obtained under complex ambient temperatures.

[0150] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A long-wave infrared athermal wide-angle temperature measurement lens, characterized in that: The components are connected in sequence along the optical axis from the object side to the image side: a first lens, a second lens, a third lens, an aperture stop, a fourth lens, and a filter; The object side surface of the first lens is convex, and the image side surface is concave; The object side surface of the second lens is convex, and the image side surface is concave; The object side surface of the third lens is concave, and the image side surface is convex; The object side surface of the fourth lens is convex, and the image side surface is convex; This lens meets the following requirements: -4.0 <f1 / f<-3.0, -6.0 <f2 / f<-5.0, 3.0 <f3 / f<4.0, 1.0 <f4 / f<2.0, Wherein, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, and f is the focal length of the long-wave infrared athermalized wide-angle temperature measurement lens; Nd1≥4.0,Tce1≥5×10 -6 , Nd2≥4.0,Tce2≥5×10 -6 , Nd3≥4.0,Tce3≥5×10 -6 , Nd4≥2.7,Tce4≥2×10 -5 , Among them, Nd1 is the refractive index of the first lens, Tce1 is the thermal expansion coefficient of the first lens; Nd2 is the refractive index of the second lens, Tce2 is the thermal expansion coefficient of the second lens; Nd3 is the refractive index of the third lens, Tce3 is the thermal expansion coefficient of the third lens; Nd4 is the refractive index of the fourth lens, Tce4 is the thermal expansion coefficient of the fourth lens.

2. The long-wave infrared athermalized wide-angle temperature measurement lens according to claim 1, characterized in that: This lens meets the following requirements: D1≤40mm,20mm <R11<30mm,10mm<R12<20mm, 3.0mm <CT1<4.0mm,7.0mm<A1<8.0mm,D2≤25mm, 10mm <R21<20mm,10mm<R22<20mm,1.5mm<CT2<2.5mm, 6.0mm <A2<7.0mm,D3≤20mm,-40mm<R31<-30mm,-30mm<R32<-20mm,3.0mm<CT3<4.0mm,8.0mm<A3<11.0mm,D4≤20mm,30mm<R41<40mm,-50mm<R42<-40mm,4.0mm<CT4<6.0mm,8.0mm<A4<11.0mm; Wherein, D1 is the aperture value of the first lens, R11 is the curvature radius of the object side surface of the first lens, R12 is the curvature radius of the image side surface of the first lens, CT1 is the center thickness of the first lens, A1 is the air gap from the first lens to the second lens, R21 is the curvature radius of the object side surface of the second lens, R22 is the curvature radius of the image side surface of the second lens, CT2 is the center thickness of the second lens, A2 is the air gap from the second lens to the third lens, R31 is the curvature radius of the object side surface of the third lens, R32 is the curvature radius of the image side surface of the third lens, CT3 is the center thickness of the third lens, A3 is the air gap from the third lens to the fourth lens, R41 is the curvature radius of the object side surface of the fourth lens, R42 is the curvature radius of the image side surface of the fourth lens, CT4 is the center thickness of the fourth lens, and A4 is the air gap from the fourth lens to the filter.

3. The long-wave infrared athermalized wide-angle temperature measurement lens according to claim 1, characterized in that: The object side of the first lens is a spherical surface with a curvature radius of R = 28.6 mm and a thickness of d = 3 mm. The image side surface of the first lens is an even aspheric surface with a curvature radius of R = 18.5 mm and a thickness of d = 7.5 mm; The object side of the second lens is a spherical surface with a curvature radius of R = 17.5 mm and a thickness of d = 2 mm; The image side surface of the second lens is an even aspheric surface with a curvature radius of R = 13.7 mm and a thickness of d = 6.6 mm; The object side of the third lens is an even aspheric surface with a curvature radius of R = -31.6mm and a thickness of d = 3mm; The image side of the third lens is a spherical surface with a curvature radius of R = -22.6mm and a thickness of d = 10mm; The object side of the fourth lens is a spherical surface with a curvature radius of R=34.8 mm and a thickness of d=5 mm; The image side surface of the fourth lens is a binary diffraction surface with a curvature radius of R=-47.7mm and a thickness of d=10mm.

4. The long-wave infrared athermalized wide-angle temperature measurement lens according to claim 1, characterized in that: The refractive index of the first lens, the second lens, and the third lens = 4.0Nd; The refractive index of the fourth lens=2.77Nd.

5. The long-wave infrared athermalized wide-angle temperature measurement lens according to claim 1, characterized in that: The diffraction surface coefficients of the image-side surface L42 of the fourth lens are: normalized radius 11 mm; phase coefficient H1 -63.37; phase coefficient H2 23.79; phase coefficient H3 -13.

31.

6. The long-wave infrared athermalized wide-angle temperature measurement lens according to claim 1, characterized in that: The optical parameters of the lens are as follows: the focal length f of the lens is 6mm; the aperture F number is 1.0; the working band is 8~12μm; the resolution of the adapted detector is 640×480, 17μm; the field of view is 91° (horizontal) × 75° (vertical); the working temperature is -40℃~+70℃.

7. The long-wave infrared athermalized wide-angle temperature measurement lens according to claim 1, characterized in that: The total optical length of the lens is less than or equal to 50mm; the imaging distortion is less than 12%; and the field curvature is less than ±0.

1.

8. The long-wave infrared athermalized wide-angle temperature measurement lens according to claim 1, characterized in that: include: Focusing components and fixed installation components; The focusing assembly includes: a fourth lens and a focusing lens frame; the fixed installation assembly includes: a first lens, a second lens, a third lens, and a lens barrel; the first lens, the second lens, the third lens, and the aperture STOP are fixedly installed in the lens barrel in sequence; The fourth lens is installed in a focusing frame; the focusing frame is arranged to perform reciprocating focusing motion along the axial direction of the lens barrel.

9. The long-wave infrared athermalized wide-angle temperature measurement lens according to claim 8, characterized in that: include: Motor: The motor is mounted on the outer wall of the lens barrel and is connected to the focusing lens frame drive.

10. The long-wave infrared athermalized wide-angle temperature measurement lens according to claim 8, characterized in that: The filter is arranged in the long-wave uncooled detector and connected to the optical path of the fourth lens; IMA is the image plane of the long-wave uncooled detector.

Images