A large aperture swir vehicle lens

Abstract

The application discloses a large-aperture SWIR vehicle-mounted lens, which is applied to a near-infrared wave band and comprises, in sequence from an object plane to an image plane, a positive-power first lens, a positive-power second lens, a stop, a positive-power third lens, a negative-power fourth lens, a negative-power fifth lens, a positive-power sixth lens and a positive-power seventh lens; the vehicle-mounted lens adopts an optical passive compensation technology, and the power of each lens is distributed, so that the vehicle-mounted lens realizes athermal high-definition imaging in a temperature range of-40 DEG C to 105 DEG C. The application provides a long-focal-length, large-aperture and athermal vehicle-mounted lens, which can be adapted to a megapixel sensor, and the vehicle-mounted lens can image in the near-infrared wave band, can effectively reduce the interference of low visibility under weather such as rain, snow and haze, and adopts the optical passive compensation, so that the vehicle-mounted lens realizes high-low temperature defocus compensation in a temperature range of-40 DEG C to 105 DEG C, thereby having good optical performance.

Description

Technical Field

[0001] This invention relates to the field of automotive lens technology, and in particular to a large-aperture SWIR automotive lens. Background Technology

[0002] With the popularization of intelligent vehicles and the development of ADAS systems and autonomous driving technology, the requirements for automotive cameras are becoming increasingly stringent. As the imaging lenses of a car, automotive cameras can image objects outside the vehicle onto the detector, converting light signals into image signals, thereby providing drivers with real-time information on surrounding road conditions, helping them understand the surrounding environment during driving, and improving driving safety.

[0003] However, during daily driving, automotive lenses encounter various interferences that affect image clarity. For example, in foggy or hazy weather with low visibility, conventional visible light struggles to penetrate the fog, making it difficult for automotive lenses to achieve high-quality images and impacting driving safety. At night, when meeting oncoming traffic, the excessive brightness of high beams can cause glare, creating blind spots and similarly affecting driving safety. Furthermore, automotive lenses face significant environmental temperature variations when used outdoors. The lens materials commonly used in automotive lenses are plastic or glass, both of which have a higher temperature coefficient of refractive index (dn / dT) in the SWIR band, typically an order of magnitude higher than that used in the visible light band. Therefore, with changes in ambient temperature, the refractive index of SWIR optical materials, the curvature of components, thickness, and spacing will change even more significantly. Combined with the thermal expansion and contraction of structural components such as spacers and lens barrels, this can cause defocusing and other aberrations in the entire automotive lens system, severely affecting its image quality.

[0004] Therefore, the design of automotive lenses needs to consider reducing the impact of severe weather on image quality and ensuring good performance in working environments with large temperature differences. This requires considering the thermal difference treatment of the lens at different temperatures to achieve calorific high-definition imaging. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a long focal length, large aperture SWIR automotive lens that enables athermal high-definition imaging in working environments with low visibility and large temperature differences.

[0006] Technical Solution: To achieve the above objectives, the present invention provides a large-aperture SWIR automotive lens applied in the near-infrared band, with a total optical length of 45-50mm, an entrance pupil size of 26-32mm, and a total focal length of 32-38mm. It includes a first lens, a second lens, an aperture stop, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens, arranged sequentially from the object plane to the image plane. The automotive lens employs passive optical compensation technology to achieve calorimetric high-definition imaging within a temperature range of -40℃ to 105℃.

[0007] The optical passive compensation technology includes allocating the optical power of each lens and the thermal expansion coefficient of each lens material, thereby eliminating image plane shift caused by focal length shift of each lens under high and low temperature conditions.

[0008] The optical power of each lens is allocated as follows: the first lens, the second lens, the third lens, the sixth lens, and the seventh lens are all positive optical power, while the fourth lens and the fifth lens are both negative optical power.

[0009] Wherein, the first lens has a convex surface on the object side and a concave surface on the image side; the second lens has a convex surface on the object side and a concave surface on the image side; the third lens has a convex surface on the object side and a concave surface on the image side; the fourth lens has a convex surface on the object side and a concave surface on the image side; the fifth lens has a concave surface on the object side and a concave surface on the image side; the sixth lens has a flat surface on the object side and a convex surface on the image side; and the seventh lens has a convex surface on the object side and a flat surface on the image side.

[0010] Among them, the first lens, the second lens, the third lens, and the fourth lens are all meniscus lenses, the fifth lens is a biconcave lens, and the sixth and seventh lenses are plano-convex lenses.

[0011] The thermal expansion coefficients of the materials of each lens are as follows: the refractive index temperature coefficients dn / dT of the second, third, fourth, and fifth lenses are all negative, while the refractive index temperature coefficients dn / dT of the first, sixth, and seventh lenses are all positive. When the ambient temperature rises, the concave surface of each lens will expand towards the center of the lens, while the convex surface will expand towards the air gap. When the ambient temperature drops, under normal circumstances, the material will shrink after cooling, that is, the concave surface of each lens will expand towards the air gap, while the convex surface will expand towards the center of the lens.

[0012] Among them, the first to the seventh lenses are all spherical glass lenses.

[0013] The refractive index Nd and Abbe number Vd of the first to seventh lenses satisfy the following conditions:

[0014] The refractive index of the first lens is Nd1 = 1.74, and the Abbe number is 40 ≤ Vd1 ≤ 45;

[0015] The refractive index of the second lens is Nd2 = 1.72, and the Abbe number is 45 ≤ Vd2 ≤ 50;

[0016] The refractive index of the third lens is Nd3 = 1.85, and the Abbe number is 20 ≤ Vd3 ≤ 25;

[0017] The refractive index of the fourth lens is Nd4 = 1.72, and the Abbe number is 25 ≤ Vd4 ≤ 30;

[0018] The refractive index of the fifth lens is Nd5 = 1.73, and the Abbe number is 25 ≤ Vd5 ≤ 30.

[0019] The refractive index of the sixth lens is Nd6 = 1.83, and the Abbe number is 35 ≤ Vd6 ≤ 40;

[0020] The refractive index of the seventh lens is Nd7 = 1.74, and the Abbe number is 40 ≤ Vd7 ≤ 45.

[0021] The focal lengths of the first to seventh lenses satisfy the following conditions:

[0022] The focal length of the first lens is 81≤f1≤82;

[0023] The focal length of the second lens is 43≤f2≤44;

[0024] The focal length of the third lens is 85≤f3≤86;

[0025] The focal length of the fourth lens is -19≤f4≤-18;

[0026] The focal length of the fifth lens is -20≤f5≤-19;

[0027] The focal length of the sixth lens is 34≤f6≤35;

[0028] The focal length of the seventh lens is 21≤f7≤22.

[0029] The seventh lens and the image plane are provided with a filter to filter visible light and ultraviolet light from entering the photosensitive element on the image plane receiving surface.

[0030] Beneficial effects: The present invention has the following advantages: 1. The vehicle-mounted lens of the present invention adopts a near-infrared band design. Infrared light has strong penetrability and low sensitivity to glare, which enables the vehicle-mounted lens to achieve effective detection and clear imaging under adverse weather conditions such as rain, snow, thick smoke, dust and fog. Even when the driver's vision is temporarily lost due to the high brightness of the headlights at night, it can still provide the driver with a clear image and improve driving safety.

[0031] 2. The vehicle-mounted lens of the present invention adopts a large aperture and long focal length design, which enables it to capture enough light in environments with poor lighting conditions and has a longer detection range, thereby ensuring that the acquired image is clear and detailed.

[0032] 3. The vehicle lens described in this invention uses a glass lens. Compared with other optical materials, glass lenses have higher hardness, oxidation resistance and transmittance. At the same time, glass lenses have smaller deformation at different temperatures, higher image clarity and better color contrast.

[0033] 4. This invention uses optical passive compensation technology to rationally allocate the optical power of each lens and selects glass materials with different coefficients of thermal expansion to combine for high and low temperature defocus compensation, so that the vehicle-mounted lens imaging system can be heat-free in a wide temperature range of -40℃ to 105℃. This technology not only improves the imaging quality of the vehicle-mounted lens, but also makes the vehicle-mounted lens lightweight, highly reliable and low cost. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the vehicle-mounted lens structure described in this invention;

[0035] Figure 2 A schematic diagram of Through Focus MTF when the operating temperature of the automotive lens is 20℃.

[0036] Figure 3 A schematic diagram of Through Focus MTF when the operating environment temperature of the automotive lens is -40℃.

[0037] Figure 4 This is a schematic diagram of Through Focus MTF when the operating temperature of the automotive lens is 105℃. Detailed Implementation

[0038] The technical solution of the present invention will be described in detail below with reference to the embodiments and accompanying drawings.

[0039] The vehicle-mounted lens described in this invention operates in the near-infrared (SWIR) band, with a wavelength range of 1300-1350nm. Compared to the visible light band, infrared light has a longer wavelength and a lower frequency. At night, the infrared imaging system can provide the driver with a better field of vision and avoid temporary vision loss caused by the high brightness of headlights when passing other vehicles. Simultaneously, infrared light has excellent penetrating power, capable of penetrating fog, dust, and smoke, enabling detection and imaging in special weather conditions with low visibility.

[0040] like Figure 1 As shown, in this embodiment, the total focal length of the vehicle-mounted lens is preferably 35.3mm, the total optical length is preferably 47mm, and the working F-number is preferably 1.2. From the object plane to the image plane (from left to right), it comprises seven optical lenses: a first meniscus lens L1 with positive optical power, a second meniscus lens L2 with positive optical power, an aperture stop, a third meniscus lens L3 with positive optical power, a fourth meniscus lens L4 with negative optical power, a fifth biconcave lens L5 with negative optical power, a sixth plano-convex lens L6 with positive optical power, and a seventh plano-convex lens L7 with positive optical power. The object-side surface of the sixth lens L6 and the image-side surface of the seventh lens L7 are both planar, facilitating processing and assembly with the vehicle-mounted lens.

[0041] All seven lenses are spherical glass lenses. Compared to aspherical lenses, spherical lenses have a better cost advantage and higher processing precision. Compared to plastic lenses, glass lenses have higher hardness, oxidation resistance, and transmittance; at the same time, the coefficient of thermal expansion of glass lenses is an order of magnitude smaller than that of plastic lenses, and the deformation at different temperatures is also smaller, making them suitable for working environments with large temperature variations.

[0042] The refractive indices Nd and Abbe numbers Vd of the first lens L1 to the seventh lens L7 satisfy the following conditions: The refractive index of the first lens L1 is Nd1 = 1.74, and the Abbe number is 40 ≤ Vd1 ≤ 45; the refractive index of the second lens L2 is Nd2 = 1.72, and the Abbe number is 45 ≤ Vd2 ≤ 50; the refractive index of the third lens L3 is Nd3 = 1.85, and the Abbe number is 20 ≤ Vd3 ≤ 25; the refractive index of the fourth lens L4 is Nd4 = 1.72, and the Abbe number is 25 ≤ Vd4 ≤ 30; the refractive index of the fifth lens L5 is Nd5 = 1.73, and the Abbe number is 25 ≤ Vd5 ≤ 30; the refractive index of the sixth lens L6 is Nd6 = 1.83, and the Abbe number is 35 ≤ Vd6 ≤ 40; the refractive index of the seventh lens L7 is Nd7 = 1.74, and the Abbe number is 40 ≤ Vd7 ≤ 45.

[0043] The focal lengths of the first lens L1 to the seventh lens L7 satisfy the following conditions: the focal length of the first lens L1 is 81≤f1≤82; the focal length of the second lens L2 is 43≤f2≤44; the focal length of the third lens L3 is 85≤f3≤86; the focal length of the fourth lens L4 is -19≤f4≤-18; the focal length of the fifth lens L52 is -20≤f5≤-19; the focal length of the sixth lens L62 is 34≤f6≤35; and the focal length of the seventh lens L7 is 21≤f7≤22.

[0044] This embodiment lists the optimal design schemes for parameters such as curvature, thickness, and spacing of various lens surfaces in the automotive lens, as shown in Table 1:

[0045] Table 1: Parameters of each lens element in the vehicle-mounted lens

[0046]

[0047]

[0048] Compared to existing vehicle-mounted lenses, the vehicle-mounted lens provided by this invention has a longer focal length, resulting in a greater detection range, increasing the detection distance by 2-3 times. The preferred operating F-number is 1.2, indicating that the first lens L1 has a large aperture, enabling it to collect more light information during imaging. This allows the entire vehicle-mounted lens system to deliver a greater light throughput to the photosensor, achieving clear imaging in low-light environments such as at night.

[0049] The aforementioned seven-lens combination can correct spherical aberration, field curvature, and distortion that occur during the imaging process of automotive lenses, thereby optimizing aberrations. Specifically, positive-power meniscus lenses (L1, L2, L3) and negative-power meniscus lens (L4) can be used to correct spherical aberration and field curvature. Lens L2 bends light towards the aperture stop, reducing higher-order aberrations. The biconcave lens (L5) acts as a divergent light source, and the plano-convex lenses (L6, L7) reduce distortion. This design ensures that light does not undergo excessive bending angles before and after each lens. During tolerance analysis, while ensuring performance, it also meets a relatively relaxed tolerance distribution, reducing the difficulty of manufacturing and assembling automotive lenses and improving the assembly yield of automotive lenses.

[0050] The vehicle-mounted lens of this invention fully considers the potential for high and low temperature changes in the working environment, and the resulting thermal expansion and contraction of optical lenses and structural components, which can lead to defocusing and image blurring in the entire vehicle-mounted lens imaging system. To solve this problem, this invention utilizes optical passive compensation technology to rationally allocate the optical power of each lens and selects glass materials with different coefficients of thermal expansion for combination. This enables the vehicle-mounted lens imaging system to achieve heat-free operation within a wide temperature range of -40℃ to 105℃ with minimal defocusing. This technology not only improves image quality but also gives the vehicle-mounted lens advantages such as light weight, high reliability, and low cost. The specific implementation method is as follows: the refractive index temperature coefficients dn / dT of the second meniscus lens L2 with positive optical power, the third meniscus lens L3 with positive optical power, the fourth meniscus lens L4 with negative optical power, and the fifth biconcave lens L5 with negative optical power are all negative. The refractive index temperature coefficients dn / dT of the first meniscus lens L1 with positive optical power, the sixth plano-convex lens L6 with positive optical power, and the seventh plano-convex lens L7 with positive optical power are all positive. When the temperature rises, the concave surface will expand towards the center of the lens, and the convex surface will expand towards the air gap. The opposite is true when the temperature drops, thereby eliminating the image plane shift caused by the focal length shift of each lens under high and low temperature conditions.

[0051] A filter can also be added to the vehicle-mounted lens to improve image quality. Filter L8 is located between the seventh lens L7 and the image plane. The main function of filter L8 is to filter out light outside the designed wavelength range, preventing visible light and certain ultraviolet light from entering the image sensor to avoid image ghosting and thus improve the system's image sharpness. In addition, filter L8 also protects the lens from dust and water stains.

[0052] In the process of thermal analysis of automotive lenses, it is necessary to fully consider, such as Figure 1 The support methods and positions between optical and structural components, including the spacers between lenses L1 and L2, L2 and L3, L3 and L4, L6 and L7, and the lens barrel between lens L7 and the image plane, are input into Zemax software for modeling. During modeling, the thermal expansion coefficients of each component, including lenses, spacers, and the lens barrel, are input. Operating environments of 20℃, -40℃, and 105℃ are constructed in a multi-structure environment. The curvature radius of each lens and the thickness variations of lenses and structural components are calculated using the software's built-in calculation method to account for deformation at different temperatures. This design uses a sampling frequency of 72 lp / mm. Figures 2-4 In the Through Focus MTF diagram shown, different colored lights represent Through Focus MTF curves for different fields of view. The horizontal axis represents the defocus amount, and the vertical axis represents the MTF value at 72 lp / mm. The horizontal axis value of the highest point at a 0° field of view represents the defocus amount of the paraxial optimal focal plane. Figures 2-4 It can be seen that the defocusing amount of the vehicle lens is very small at different temperatures, specifically the defocusing offset is <3um at each temperature. This indicates that the vehicle lens designed in this solution can effectively perform thermal differential work in an operating environment of -40℃ to 105℃.

Claims

1. A large-aperture SWIR automotive lens, characterized in that, The vehicle-mounted lens is used in the near-infrared band, with a total optical length of 45-50mm, an entrance pupil size of 26-32mm, and a total focal length of 32-38mm. From the object plane to the image plane, it consists of a first lens, a second lens, an aperture stop, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens. The vehicle-mounted lens uses optical passive compensation technology to achieve calorific high-definition imaging within a temperature range of -40℃ to 105℃. The first lens, the second lens, the third lens, the sixth lens, and the seventh lens are all positive optical power, while the fourth lens and the fifth lens are all negative optical power. The first lens has a convex object side and a concave image side; the second lens has a convex object side and a concave image side; the third lens has a convex object side and a concave image side; the fourth lens has a convex object side and a concave image side; the fifth lens has a concave object side and a concave image side; the sixth lens has a planar object side and a convex image side; and the seventh lens has a convex object side and a planar image side. The focal length of the first lens is 81mm ≤ f1 ≤ 82mm; The focal length of the second lens is 43mm ≤ f2 ≤ 44mm; The focal length of the third lens is 85mm≤f3≤86mm; The focal length of the fourth lens is -19mm≤f4≤-18mm; The focal length of the fifth lens is -20mm≤f5≤-19mm; The focal length of the sixth lens is 34mm≤f6≤35mm; The focal length of the seventh lens is 21mm≤f7≤22mm.

2. The large aperture SWIR automotive lens according to claim 1, characterized in that: The optical passive compensation technology includes allocating the optical power of each lens and the thermal expansion coefficient of each lens material, thereby eliminating image plane shift caused by focal length shift of each lens under high and low temperature conditions.

3. The large aperture SWIR automotive lens according to claim 1, characterized in that: The thermal expansion coefficients of the lens materials are as follows: the refractive index temperature coefficients dn / dT of the second, third, fourth, and fifth lenses are all negative, while the refractive index temperature coefficients dn / dT of the first, sixth, and seventh lenses are all positive. When the ambient temperature rises, the concave surface of each lens will expand towards the center of the lens, while the convex surface will expand towards the air gap. When the ambient temperature decreases, the concave surface of each lens will expand towards the air gap, while the convex surface will expand towards the center of the lens.

4. The large aperture SWIR automotive lens according to claim 1, characterized in that: The first to the seventh lenses are all spherical glass lenses.

5. The large aperture SWIR automotive lens according to claim 1, characterized in that: The refractive index Nd and Abbe number Vd of the first to seventh lenses satisfy the following conditions: The refractive index of the first lens is Nd1=1.74, and the Abbe number is 40≤Vd1≤45; The refractive index of the second lens is Nd2=1.72, and the Abbe number is 45≤Vd2≤50; The refractive index of the third lens is Nd3=1.85, and the Abbe number is 20≤Vd3≤25; The refractive index of the fourth lens is Nd4=1.72, and the Abbe number is 25≤Vd4≤30; The refractive index of the fifth lens is Nd5=1.73, and the Abbe number is 25≤Vd5≤30; The refractive index of the sixth lens is Nd6=1.83, and the Abbe number is 35≤Vd6≤40; The refractive index of the seventh lens is Nd7=1.74, and the Abbe number is 40≤Vd7≤45.

6. The large aperture SWIR automotive lens according to claim 1, characterized in that: A filter is also provided between the seventh lens and the image plane to filter visible light and ultraviolet light from entering the photosensitive element on the image plane receiving surface.

Images