Large-aperture large-depth-of-field short-wave infrared vehicle-mounted lens

Abstract

The invention discloses a large-aperture large-depth-of-field short-wave infrared vehicle-mounted lens which is applied to a short-wave infrared spectrum band. Comprising a lens L1 with negative focal power, a lens L2 with negative focal power, a lens L3 with positive focal power, a diaphragm STOP, a lens L4 with negative focal power, a lens L5 with positive focal power, a lens L6 with positive focal power and a lens L7 with positive focal power which are sequentially distributed from an object plane to an image plane, and the total optical length TTL, the effective aperture D and the total focal length f of the vehicle-mounted lens meet the conditions that f / D is larger than or equal to 1.4 and smaller than or equal to 1.8, and f / TTL is larger than or equal to 0.1 and smaller than or equal to 0.2. According to the vehicle-mounted lens, the design of large aperture and large depth of field is adopted, the vehicle-mounted lens is more suitable for a long-distance, large-range and low-illumination environment, and clear imaging can be achieved within the object distance range from 0.75 m to infinity without refocusing.

Description

Technical Field

[0001] The invention relates to the technical field of vehicle-mounted lenses, in particular to a short-wave infrared vehicle-mounted lens with a large aperture and a large depth of field. Background Art

[0002] Existing vehicle-mounted lenses not only need to provide clear and accurate road image information, but also need to ensure the safety of vehicles at night or in bad weather such as thunderstorms, fog and haze. As one of the "atmospheric windows", short-wave infrared imaging is less affected by atmospheric scattering, has a strong ability to penetrate fog, haze, and smoke, has a long effective detection distance, and is significantly more adaptable to climate conditions and environments than visible light imaging. This gives short-wave infrared imaging a significant inherent advantage in vehicle-mounted lenses.

[0003] However, most of the current vehicle-mounted lenses work in the visible light or near-infrared spectrum, which cannot adapt to the application requirements of short-wave infrared imaging. In addition, existing vehicle-mounted lenses are often designed for targets at specific distances, and cannot achieve both depth of field and field of view. It is difficult to meet the observation needs of a large range and large depth of field targets in front when the car is driving at high speed. Summary of the invention

[0004] Purpose of the invention: The purpose of the invention is to provide a large-aperture, large-depth-of-field short-wave infrared vehicle-mounted lens with a large observation range and a long detection distance.

[0005] Technical solution: To achieve the above-mentioned purpose, the large-aperture and large-depth-of-field short-wave infrared vehicle-mounted lens of the present invention is applied to the 1300-1350nm short-wave infrared spectrum, including a lens L1 with negative optical focal length, a lens L2 with negative optical focal length, a lens L3 with positive optical focal length, an aperture STOP, a lens L4 with negative optical focal length, a lens L5 with positive optical focal length, a lens L6 with positive optical focal length, and a lens L7 with positive optical focal length, which are distributed in sequence from the object plane to the image plane. The total optical length TTL, the effective aperture D, and the total focal length f of the vehicle-mounted lens satisfy 1.4≤f / D≤1.8 and 0.1≤f / TTL≤0.2.

[0006] Among them, the object side surface of lens L1 is convex, and the image side surface is concave; the object side surface of lens L2 is convex, and the image side surface is concave; the object side surface of lens L3 is convex, and the image side surface is convex; the object side surface of lens L4 is convex, and the image side surface is concave; the object side surface of lens L5 is concave, and the image side surface is convex; the object side surface of lens L6 is convex, and the image side surface is convex; the object side surface of lens L7 is convex, and the image side surface is convex.

[0007] The refractive index of the lens L1 is 1.78≤Nd1≤1.84, and the Abbe number is 42≤Vd1≤50; the refractive index of the lens L2 is 1.57≤Nd2≤1.63, and the Abbe number is 55≤Vd2≤65; the refractive index of the lens L3 is 1.80≤Nd3≤1.92, and the Abbe number is 35≤Vd3≤42; the refractive index of the lens L4 is 1.90≤Nd 4≤1.95, and the Abbe number is 15≤Vd4≤23; the refractive index of the lens L5 is 1.80≤Nd5≤1.92, and the Abbe number is 35≤Vd5≤42; the refractive index of the lens L6 is 1.80≤Nd6≤1.85, and the Abbe number is 38≤Vd6≤48; the refractive index of the lens L7 is 1.48≤Nd7≤1.63, and the Abbe number is 61≤Vd7≤72.

[0008] Among them, the focal length of the lens L1 is -12≤f1≤8; the focal length of the lens L2 is -50≤f2≤-35; the focal length of the lens L3 is 13≤f3≤19; the focal length of the lens L4 is -45≤f4≤-32; the focal length of the lens L5 is 15≤f5≤25; the focal length of the lens L6 is 12≤f6≤23; and the focal length of the lens L7 is 30≤f7≤47.

[0009] Wherein, the total optical length TTL of the vehicle-mounted lens and the distance BFL from the center of the image side surface of the seventh lens to the image plane satisfy: TTL / BFL≤5.

[0010] The total focal length f of the vehicle-mounted lens and the distance BFL from the center of the image side surface of the seventh lens to the image plane satisfy: 0.5≤f / BFL≤1.

[0011] Wherein, the field of view angle of the vehicle-mounted lens is FOV=0°~108°.

[0012] Wherein, the effective imaging object distance of the vehicle-mounted lens is 0.75m to infinity without refocusing.

[0013] Among them, the lenses L1 to L7 are all glass spherical single lenses.

[0014] Wherein, a filter is also provided between the lens L7 and the image plane.

[0015] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0016] 1. The vehicle-mounted lens of the present invention works in the short-wave infrared spectrum, which ranges from 1300 to 1350nm. Different from the traditional near-infrared imaging, the lens in this spectrum has strong ability to penetrate fog, rain, snow, smoke and dust, and has a long effective detection distance;

[0017] 2. The vehicle-mounted lens of the present invention adopts a large aperture and large field of view design, with an aperture number FNO = 1.6 and a field of view angle FOV = 108°; it is suitable for a wide range of low-light environments. Compared with existing lenses, the vehicle-mounted lens has a large depth of field and can clearly image an object distance of 0.75m-infinity without refocusing, ensuring that objects at different levels can obtain clear images and details;

[0018] 3. The vehicle-mounted lens of the present invention uses 7 lenses with specific optical power, and through reasonable layout and distribution of optical power, reduces light aberration and improves lens resolution. At the same time, the total optical length of the lens does not exceed 35mm, and the structure is compact, which is conducive to vehicle-mounted integration;

[0019] 4. The lenses of the vehicle-mounted lens of the present invention are all glass spherical single lenses, without cemented lenses, which avoids the shortcomings of cemented lenses that are easy to debond in the infrared spectrum and have low transmittance. At the same time, the all-glass design ensures the stable performance and service life of the lens in extreme scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the structure of a vehicle-mounted lens in an embodiment of the present invention;

[0021] Figure 2 Schematic diagram of MTF of the vehicle-mounted lens at an object distance of 0.75m in an embodiment of the present invention;

[0022] Figure 3 Schematic diagram of MTF of the vehicle-mounted lens at an object distance of 1.5m in an embodiment of the present invention;

[0023] Figure 4 Schematic diagram of MTF of the vehicle-mounted lens at infinite object distance in an embodiment of the present invention;

[0024] Figure 5 Schematic diagram of the relative illumination curve of the vehicle-mounted lens in an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is described in detail below in conjunction with the embodiments and drawings.

[0026] like Figure 1 The embodiment of a large-aperture, large-depth-of-field short-wave infrared vehicle-mounted lens disclosed in the present invention is shown, which comprises a convex-concave lens L1 with negative optical power, a convex-concave lens L2 with negative optical power, a convex-convex lens L3 with positive optical power, a convex-concave lens L4 with negative optical power, a convex-convex lens L5 with positive optical power, a convex-convex lens L6 with positive optical power, and a convex-convex lens L7 with positive optical power, which are sequentially arranged along the optical axis from the object side to the image side of the objective lens. An aperture stop is arranged between the lens L3 and the lens L4; and a filter Fliter is arranged between the lens L7 and the image plane.

[0027] The refractive index Nd and Abbe number Vd of lenses L1-L7 respectively satisfy the following conditions: lens L1, 1.78≤Nd1≤1.84, 42≤Vd1≤50; lens L2, 1.57≤Nd2≤1.63, 55≤Vd2≤65; lens L3, 1.80≤Nd3≤1.92, 35≤Vd3≤42; lens L4, 1.90≤Nd4≤1.95, 15≤Vd4≤23; lens L5, 1.80≤Nd5≤1.92, 35≤Vd5≤42; lens L6, 1.80≤Nd6≤1.85, 38≤Vd6≤48; lens L7, 1.48≤Nd7≤1.63, 61≤Vd7≤72.

[0028] The focal lengths of lenses L1-L7 respectively satisfy the following conditions: lens L1, -12≤f1≤-2; lens L2, -50≤f2≤-35; lens L3, 13≤f3≤19; lens L4, -45≤f4≤-32; lens L5, 15≤f5≤25; lens L6, 12≤f6≤23; lens L7, 30≤f7≤47.

[0029] The basic parameters of the above-mentioned vehicle-mounted lenses are shown in Table 1 below:

[0030] Table 1: Basic parameters of optical system

[0031]

[0032] like Figure 1 As shown, in this embodiment, the aperture number FNO of the vehicle-mounted lens is 1.6, the focal length f of the vehicle-mounted lens is 5.4mm, the total optical length TTL of the vehicle-mounted lens is 35mm, and the field of view FOV of the vehicle-mounted lens is 108°. In this embodiment, the vehicle-mounted lens, in the case of a short focal length with a large field of view, balances the performance differences between different object distances by matching different optical powers of the lens, so that the lens obtains an excellent large depth of field range and can clearly image at an object distance of 0.75m-infinity.

[0033] When in use, the lens L1 with negative optical power collects the light emitted by the object, and its convex surface facing the object side helps the light at a large angle to enter the system smoothly. The meniscus lens L2 with negative optical power is used to preliminarily correct spherical aberration and shorten the focal length. The lens L3 with positive optical power further converges the light to reduce the aperture, while reducing the incident angle of the light entering the subsequent system and preliminarily correcting the aberration. The aperture is placed after the lens L3 to control the aperture of the entire optical system of the vehicle-mounted lens, which is also conducive to the reduction of the overall size. The lens L4 with negative optical power and the lens L5 with positive optical power cooperate to eliminate the astigmatism and field curvature of the system. The lens L6 and the lens L7 cooperate to make the light of each field of view converge to the corresponding image point, and at the same time reduce the CRA of the light entering the image plane, so as to achieve the purpose of making the illumination on the image plane uniform.

[0034] The above optical systems are all spherical mirrors and adopt an all-glass design, which avoids the temperature drift problem of plastic lens systems; the all-single lens design avoids the problem of easy debonding of glued parts in the infrared spectrum and low transmittance; at the same time, the large aperture is conducive to ensuring the brightness of imaging in dim environments, the large depth of field is conducive to providing clear and accurate details and depth information, and the short overall length is conducive to the integration of the lens into the target system; the overall structure is simple and the shape is regular, which can meet the low-cost requirements of mass production.

[0035] This embodiment adopts a sampling frequency of 50lp / mm. Figures 2 to 4 The MTF curves are shown in the figure below. The horizontal axis represents the spatial frequency in lp / mm (line pairs / millimeter), and the vertical axis represents the MTF value. From the three figures, we can see that the system field of view reaches ±54°, the best focal plane is at an object distance of 1.5m, the MTF value is greater than 0.5, and the MTF at object distances of 0.75m and infinity is greater than 0.3, indicating that the lens has an excellent depth of field and can provide good depth information for the vehicle. Figure 5 The relative illumination curve of this embodiment is shown, the horizontal axis represents different viewing angles, and the vertical axis represents relative illumination. Figure 5 It can be seen that the relative illumination of the system from the center to the edge is very uniform, avoiding the vignetting problem common in large field of view lenses.

[0036] The vehicle-mounted lens of the present invention is applied in the short-wave infrared spectrum, taking into account the advantages of large aperture and large depth of field; compared with the visible light band or the near-infrared light band, it has good penetration, can penetrate haze, dust, smoke, etc., and can realize detection and imaging in special weather conditions with low visibility.

Claims

1. A large aperture and large depth of field short-wave infrared vehicle-mounted lens, applied in the short-wave infrared spectrum, characterized in that: The vehicle-mounted lens comprises a negative power lens L1, a negative power lens L2, a positive power lens L3, an aperture STOP, a negative power lens L4, a positive power lens L5, a positive power lens L6, and a positive power lens L7, which are distributed in sequence from the object plane to the image plane. The total optical length TTL, the effective aperture D, and the total focal length f of the vehicle-mounted lens satisfy 1.4≤f / D≤1.8 and 0.1≤f / TTL≤0.

2.

2. The large-aperture, large-depth-of-field short-wave infrared vehicle-mounted lens according to claim 1, characterized in that: The object side surface of lens L1 is convex, and the image side surface is concave; the object side surface of lens L2 is convex, and the image side surface is concave; the object side surface of lens L3 is convex, and the image side surface is convex; the object side surface of lens L4 is convex, and the image side surface is concave; the object side surface of lens L5 is concave, and the image side surface is convex; the object side surface of lens L6 is convex, and the image side surface is convex; the object side surface of lens L7 is convex, and the image side surface is convex.

3. The large-aperture, large-depth-of-field short-wave infrared vehicle-mounted lens according to claim 1, characterized in that: The refractive index of the lens L1 is 1.78≤Nd1≤1.84, and the Abbe number is 42≤Vd1≤50; the refractive index of the lens L2 is 1.57≤Nd2≤1.63, and the Abbe number is 55≤Vd2≤65; the refractive index of the lens L3 is 1.80≤Nd3≤1.92, and the Abbe number is 35≤Vd3≤42; the refractive index of the lens L4 is 1.90≤Nd4≤1.95, and the Abbe number is 15≤Vd4≤23; the refractive index of the lens L5 is 1.80≤Nd5≤1.92, and the Abbe number is 35≤Vd5≤42; the refractive index of the lens L6 is 1.80≤Nd6≤1.85, and the Abbe number is 38≤Vd6≤48; the refractive index of the lens L7 is 1.48≤Nd7≤1.63, and the Abbe number is 61≤Vd7≤72.

4. The large-aperture, large-depth-of-field short-wave infrared vehicle-mounted lens according to claim 1, characterized in that: The focal length of the lens L1 is -12≤f1≤8; the focal length of the lens L2 is -50≤f2≤-35; the focal length of the lens L3 is 13≤f3≤19; the focal length of the lens L4 is -45≤f4≤-32; the focal length of the lens L5 is 15≤f5≤25; the focal length of the lens L6 is 12≤f6≤23; and the focal length of the lens L7 is 30≤f7≤47.

5. The large-aperture, large-depth-of-field short-wave infrared vehicle-mounted lens according to claim 1, characterized in that: The total optical length TTL of the vehicle-mounted lens and the distance BFL from the center of the image side surface of the seventh lens to the image plane satisfy: TTL / BFL≤5.

6. The large-aperture, large-depth-of-field short-wave infrared vehicle-mounted lens according to claim 1, characterized in that: The total focal length f of the vehicle-mounted lens and the distance BFL from the center of the image side surface of the seventh lens to the image plane satisfy: 0.5≤f / BFL≤1.

7. The large-aperture, large-depth-of-field short-wave infrared vehicle-mounted lens according to claim 1, characterized in that: The field of view angle of the vehicle-mounted lens is FOV=0°~108°.

8. The large-aperture, large-depth-of-field short-wave infrared vehicle-mounted lens according to claim 1, characterized in that: The effective imaging object distance of the vehicle-mounted lens is 0.75m to infinity without refocusing.

9. The large-aperture, large-depth-of-field short-wave infrared vehicle-mounted lens according to claim 1, characterized in that: The lenses L1 to L7 are all glass spherical single lenses.

10. The large-aperture, large-depth-of-field short-wave infrared vehicle-mounted lens according to claim 1, characterized in that: A filter is also provided between the lens L7 and the image plane.

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