A vehicle-mounted infrared night vision device lens

Abstract

The present invention discloses a vehicle-mounted infrared night vision device lens, comprising a first positive meniscus lens L1 and a second positive meniscus lens L2, arranged sequentially along the incident direction of light. The object-side surface S3 of the second positive meniscus lens L2 is a diffraction surface, and both the image-side surface S2 and the image-side surface S4 of the first positive meniscus lens L1 and the second positive meniscus lens L2 are aspherical surfaces. The first positive meniscus lens L1 is convex toward the object side, while the second positive meniscus lens L2 is convex toward the image side. The structure of the present invention is compact and lightweight, low-cost, high-resolution, and has good wide temperature adaptability and a wide range of applications.

Description

Technical Field

[0001] The invention belongs to the technical field of optical lenses, and in particular relates to a vehicle-mounted infrared night vision device lens. Background Art

[0002] Infrared thermal imagers have a long detection distance, can penetrate smoke and dust, are not affected by light, and can be used both day and night. They are widely used in industries such as electricity, construction, law enforcement, firefighting, and automotive, and have especially become a development trend in automotive night vision systems.

[0003] However, due to their high price, current automotive infrared thermal imagers are primarily used in high-end vehicles, limiting their application range. Existing infrared lenses have the following problems: 1) They use expensive crystal materials such as germanium, and can only produce aspheric or diffractive surfaces through turning, resulting in high lens costs and low lens processing efficiency, making mass production difficult; 2) Infrared lenses have a narrow field of view, and expanding the field of view reduces lens resolution, making image quality difficult to guarantee; 3) Using a large number of lenses results in large size, high cost, and inability to eliminate thermal differences across a wide temperature range. Summary of the Invention

[0004] The purpose of the present invention is to address the above problems and propose a vehicle-mounted infrared night vision device lens with a small and lightweight structure, low cost, high resolution, good wide temperature adaptability and a wide range of applications.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] The present invention proposes a vehicle-mounted infrared night vision device lens, including a first positive meniscus lens L1 and a second positive meniscus lens L2 arranged in sequence along the incident direction of light, the object side surface S3 of the second positive meniscus lens L2 is a diffraction surface, the image side surface S2 of the first positive meniscus lens L1 and the image side surface S4 of the second positive meniscus lens L2 are both aspherical surfaces, the first positive meniscus lens L1 is convex to the object side, and the second positive meniscus lens L2 is convex to the image side.

[0007] Preferably, the first positive meniscus lens L1 and the second positive meniscus lens L2 are both made of chalcogenide glass materials.

[0008] Preferably, the phase distribution of the diffraction surface satisfies the following expression:

[0009]

[0010] Where Φ(r) is the phase of the diffraction surface at the lens height r, M is the diffraction order, r0 is the normalized radius, and A1 and A2 are the phase coefficients of the diffraction surface.

[0011] Preferably, the aspheric surface satisfies the following expression:

[0012]

[0013] Where Z(r) is the distance vector height from the vertex of the aspheric surface when the lens height is r along the optical axis; c = 1 / R, R is the paraxial curvature radius of the mirror; k is the cone coefficient; A, B, C, and D are high-order aspheric coefficients.

[0014] Preferably, the air space between the first positive meniscus lens L1 and the second positive meniscus lens L2 is 2.5 mm.

[0015] Preferably, the total length of the optical system of the vehicle-mounted infrared night vision device lens is 21.5 mm.

[0016] Compared with the prior art, the present invention has the following beneficial effects: only two lenses are used, and by adopting an optical structure with "+, +" refractive powers and rationally selecting the diffraction surface and aspheric surface positions, the following effects are achieved: 1) Wide temperature adaptability: optical athermalization is achieved within the operating temperature range of -40°C to +85°C; 2) Lightweight structure, high transmittance, and low cost: only two lenses are used, the total length of the optical system is 21.5mm, the lenses weigh only 7.8g, and some lenses can be processed by molding, further reducing processing costs; 3) High resolution: the resolution of existing long-wave infrared lenses is generally below 30lp / mm, while the resolution of this lens can reach 50lp / mm, with high imaging resolution and excellent imaging quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the optical structure of the present invention;

[0018] Figure 2 is a speckle pattern of the present invention;

[0019] Figure 3 This is the MTF diagram of the present invention at room temperature (20°C);

[0020] Figure 4 This is the MTF diagram of the present invention at low temperature (-40°C);

[0021] Figure 5 This is the MTF diagram of the present invention at high temperature (+85°C);

[0022] Figure 6 This is the field curvature and distortion diagram of the present invention. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0024] It should be noted that, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0025] like Figure 1-6 As shown, a vehicle-mounted infrared night vision device lens includes a first positive meniscus lens L1 and a second positive meniscus lens L2 arranged in sequence along the incident direction of light, the object side surface S3 of the second positive meniscus lens L2 is a diffraction surface, the image side surface S2 of the first positive meniscus lens L1 and the image side surface S4 of the second positive meniscus lens L2 are both aspherical surfaces, the first positive meniscus lens L1 is convex to the object side, and the second positive meniscus lens L2 is convex to the image side.

[0026] Among them, such as Figure 1 As shown, the incident direction of light in this embodiment should be understood as from left to right. The vehicle-mounted infrared night vision device lens of this embodiment uses only two lenses, which makes the lens structure compact and lightweight, with high transmittance and low cost. By adopting an optical structure with "+, +" refractive powers and reasonably selecting the positions of the aspheric surface and the diffraction surface, optical athermalization is achieved within the operating temperature range of -40℃ to +85℃, and it has the advantages of high resolution and low distortion. At the same time, the use of aspheric lenses can achieve focus through correction of high-order curved surfaces, thereby overcoming aberrations and achieving clear imaging.

[0027] In one embodiment, both the first positive meniscus lens L1 and the second positive meniscus lens L2 are made of chalcogenide glass.

[0028] To achieve a compact and lightweight lens structure, high transmittance, low cost, and excellent impact resistance, both the first positive meniscus lens L1 and the second positive meniscus lens L2 are constructed from chalcogenide glass. The lens shapes have been modified, such as increasing the force-bearing area, improving the curved surface shape, or refining the thickness. It should be noted that other glass materials and plastics can also be used. Glass models include S-LAH55, N-SF15, and M-LAC130, while plastic models include E48R. Different lens materials can meet the needs of different optical systems.

[0029] In one embodiment, the phase distribution of the diffraction surface satisfies the following expression:

[0030]

[0031] Where Φ(r) is the phase of the diffraction surface at the lens height r, M is the diffraction order, r0 is the normalized radius, and A1 and A2 are the phase coefficients of the diffraction surface.

[0032] In one embodiment, the aspheric surface satisfies the following expression:

[0033]

[0034] Where Z(r) is the distance vector height from the vertex of the aspheric surface when the lens height is r along the optical axis; c = 1 / R, R is the paraxial curvature radius of the mirror; k is the cone coefficient; A, B, C, and D are high-order aspheric coefficients.

[0035] In one embodiment, the air gap between the first positive meniscus lens L1 and the second positive meniscus lens L2 is 2.5 mm.

[0036] In one embodiment, the total length of the optical system of the vehicle-mounted infrared night vision device lens is 21.5 mm.

[0037] This application uses only two lenses, and the second positive meniscus lens L2 can be molded, further reducing processing costs. The total length of the optical system is 21.5mm, and the lens weighs only 7.8g. The lightweight structure, high transmittance, and low cost make it suitable for mass production.

[0038] In combination with the above embodiments, the preferred parameters of the vehicle-mounted infrared night vision device lens of the present application are shown in Table 1 below.

[0039] Table 1 Optical component parameters

[0040]

[0041] See also Figure 1 In Table 1, L1 is the first positive meniscus lens, L2 is the second positive meniscus lens; S1 is the object-side surface of the first positive meniscus lens L1, S2 is the image-side surface of the first positive meniscus lens L1, S3 is the object-side surface of the second positive meniscus lens L2, and S4 is the image-side surface of the second positive meniscus lens L2; R is the paraxial curvature radius of the lens surface.

[0042] In the first positive meniscus lens L1 and the second positive meniscus lens L2, the S3 surface of L2 is a diffraction surface, the S2 surface of L1 and the S4 surface of L2 are aspherical surfaces, and the aspherical surface parameters of each mirror surface are shown in Table 2.

[0043] Table 2 Aspheric parameters

[0044] Surface number K A B C D S2 0 1.120E-004 -4.154E-006 -8.510E-009 1.330E-011 S3 0 -2.435E-003 1.634E-005 8.550E-007 -2.835E-009 S4 0 1.458E-004 1.634E-007 2.475E-010 -3.866E-012

[0045] In Table 2, K is the cone coefficient; A, B, C, and D are high-order aspheric coefficients.

[0046] When the aspheric surface meets the above parameters, it also meets the following expressions:

[0047]

[0048] Where Z(r) is the distance vector height from the vertex of the aspheric surface when the lens height is r along the optical axis; c = 1 / R, R represents the paraxial curvature radius of the mirror surface; k is the cone coefficient; A, B, C, and D are high-order aspheric coefficients.

[0049] The diffraction surface phase distribution mentioned above satisfies the following expression:

[0050]

[0051] Where Φ(r) is the phase of the diffraction surface at the lens height r; M is the diffraction order; r0 is the normalized radius; A1 and A2 are the phase coefficients of the diffraction surface.

[0052] The diffraction surface parameters are shown in Table 3:

[0053] Table 3 Diffraction surface parameters

[0054] Surface number M (diffraction order) <![CDATA[A1]]> <![CDATA[A2]]> Normalized radius S3 1 -16.96 -5.4 4mm

[0055] The vehicle-mounted infrared night vision device lens composed of the above lenses has the following optical indicators:

[0056] (1) Focal length: f = 10 mm;

[0057] (2) Field of view: 35.5°(H)*27.0°(V);

[0058] (3) Relative aperture: 1:1.0;

[0059] (4) Resolution: 640(H)*480(V);

[0060] (5) Pixel size: 10*10um;

[0061] (6) Working temperature: -40℃~+85℃;

[0062] (7) Optical lens weight: 7.8g.

[0063] The above-mentioned vehicle-mounted infrared night vision device lens was used as the test object for testing. The test steps adopted the conventional steps for lens testing and will not be repeated here. The test results are shown below:

[0064] like Figure 2As shown, in this embodiment, the spot root mean square (RMS) value is no greater than 10.6 μm, which is smaller than the Airy disk size and meets the imaging requirements.

[0065] like Figure 3 、 4 As shown in Figures 5 and 6, when the lens of this embodiment is used with an infrared detector equivalent to that in the prior art, such as a 640*480 10um uncooled long-wave infrared detector, the resolution can reach 50lp / mm, with high imaging resolution and excellent imaging quality. Moreover, at a characteristic frequency of 50lp / mm, the MTF at room temperature of 20°C, low temperature of -40°C, and high temperature of 85°C are all greater than 0.25, and the optical system can achieve optical athermalization, with the MTF close to the diffraction frequency and excellent imaging quality.

[0066] like Figure 6 As shown, the full field distortion of the lens optical system of this embodiment is less than 0.62%, and the distortion is low.

[0067] From the above optical indicators and test results, it can be seen that the optical system provided in this embodiment uses two lenses. By adopting an optical structure with "+, +" diopters and reasonably selecting the positions of the diffraction surface and aspheric surface, the lens structure is compact and lightweight, has high transmittance, low cost, and has the advantages of high resolution and low distortion.

[0068] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0069] The above-described embodiments merely represent specific and detailed examples of the present application and should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A vehicle-mounted infrared night vision device lens, characterized by: The vehicle-mounted infrared night vision device lens includes a first positive meniscus lens L1 and a second positive meniscus lens L2 sequentially arranged along the incident direction of light, the object-side surface S3 of the second positive meniscus lens L2 is a diffraction surface, the image-side surface S2 of the first positive meniscus lens L1 and the image-side surface S4 of the second positive meniscus lens L2 are both aspherical surfaces, the first positive meniscus lens L1 is convex to the object side, and the second positive meniscus lens L2 is convex to the image side, and the following conditions are satisfied: The object-side surface S1 of the first positive meniscus lens L1 has a curvature radius of 9.5 mm to 11 mm, the image-side surface S2 of the first positive meniscus lens L1 has a curvature radius of 8.5 mm to 9.2 mm, the object-side surface S3 of the second positive meniscus lens L2 has a curvature radius of -16 mm to -15 mm, and the image-side surface S4 of the second positive meniscus lens L2 has a curvature radius of -11.5 mm to -11 mm. The thickness of the first positive meniscus lens L1 is 4.8 mm, the thickness of the second positive meniscus lens L2 is 7.1 mm, the air gap between the first positive meniscus lens L1 and the second positive meniscus lens L2 is 2.5 mm, and the total length of the optical system of the vehicle-mounted infrared night vision device lens is 21.5 mm. The phase distribution of the diffraction surface satisfies the following expression: Where Φ(r) is the phase of the diffraction surface at the lens height r, M is the diffraction order, r0 is the normalized radius, A1 and A2 are the phase coefficients of the diffraction surface, A1 = -16.96, A2 = -5.

4.

2. The vehicle-mounted infrared night vision device lens according to claim 1, characterized in that: The first positive meniscus lens L1 and the second positive meniscus lens L2 are both made of chalcogenide glass material.

3. The vehicle-mounted infrared night vision device lens according to claim 1, characterized in that: The aspheric surface satisfies the following expression: Where Z(r) is the distance vector height from the vertex of the aspheric surface when the lens height is r along the optical axis; c = 1 / R, R is the paraxial curvature radius of the mirror; k is the cone coefficient; A, B, C, and D are high-order aspheric coefficients.

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