A small distortion monitoring optical lens

Abstract

The present invention provides a small distortion monitoring optical lens, which has a small field of view and high detail resolution capability, and the lens is short and lightweight, has small distortion, stable environmental adaptability, and its ghost image can be effectively controlled, meeting the imaging quality requirements of the monitoring lens. It includes a first lens, a second lens, a third lens, and a fourth lens in sequence from the object side to the image side along the optical axis, characterized in that: the first lens has positive focal power, and its object side is convex; the second lens has negative focal power, and its object side is concave; the third lens has positive focal power, and its image side is convex; the object side of the fourth lens is convex; and a color filter, a protective glass, and an IMA are arranged in sequence behind the image side of the fourth lens.

Description

Technical Field

[0001] The invention relates to the technical field of lens structure, and in particular to a small-distortion monitoring optical lens. Background Art

[0002] With the continuous development of intelligent and safe driving of automobiles, the requirements for on-board monitoring imaging lenses are constantly increasing. Under the premise of maintaining the lens's high detail resolution ability in a small field of view and the lens being short and lightweight, the requirements for the lens's environmental stability and the restoration of monitoring facts, stray light, ghosting and other factors are getting higher and higher. Although there are low-cost glass-plastic hybrid structures among the only small-field-of-view monitoring lenses currently available, for driver status monitoring lenses with strict environmental performance requirements, full-glass structures with small distortion and good environmental stability are still the preferred choice for on-board monitoring lenses. However, existing optical lenses cannot meet the above requirements for the time being. Summary of the invention

[0003] In response to the above problems, the present invention provides a small distortion monitoring optical lens, which has a small field of view and high detail resolution capability, and the lens is short and lightweight, has small distortion and stable environmental adaptability, and its ghost images can be effectively controlled, meeting the imaging quality requirements of the monitoring lens.

[0004] A small distortion monitoring optical lens, the technical solution of which is as follows: it includes a first lens, a second lens, a third lens, and a fourth lens in sequence from the object side to the image side along the optical axis, characterized in that: the first lens has positive focal power, and its object side is a convex surface;

[0005] The second lens has negative optical power, and its object side surface is concave;

[0006] The third lens has positive refractive power, and its image side surface is convex;

[0007] The object side surface of the fourth lens is a convex surface;

[0008] A color filter, a protective glass, and an IMA are sequentially arranged behind the image side surface of the fourth lens.

[0009] It is further characterized by:

[0010] It also includes an aperture, which is arranged on the object side of the first lens or between any two adjacent lenses;

[0011] The fourth lens has positive or negative optical power;

[0012] The first lens satisfies 2<F1 / F<5, F1 is the focal length of the first lens, and F is the focal length of the entire optical system; the first lens satisfies 0.2<r1 / r2<0.8, r1 is the object side curvature radius of the first lens, and r2 is the image side curvature radius of the first lens;

[0013] The second lens satisfies r3 / r4≥-0.8, r3 is the curvature radius of the second lens on the object side, and r4 is the curvature radius of the second lens on the image side; the second lens satisfies F2 / F≥-1.5, F2 is the focal length of the second lens, and F is the overall focal length of the optical system;

[0014] The third lens satisfies F3 / F≥0.5, where F3 is the focal length of the third lens and F is the overall focal length of the optical system;

[0015] The fourth lens satisfies 1.0<|F4 / F|<12, F4 is the focal length of the fourth lens, and F is the overall focal length of the optical system;

[0016] The optical lens includes at least three glass spherical lenses;

[0017] When the optical lens includes only three glass spherical lenses, another lens is a glass aspherical lens, and the position of the glass aspherical lens is not limited and can be set according to requirements;

[0018] The first lens, the second lens, and the third lens are all glass spherical lenses, and the fourth lens is a glass aspherical lens;

[0019] The optical lens includes four glass spherical lenses, that is, the first lens, the second lens, the third lens, and the fourth lens are all glass spherical lenses;

[0020] The maximum field of view FOV of the optical lens, the maximum light clearance D of the object side surface S1 of the first lens L1 corresponding to the maximum field of view of the optical lens, and the image height h corresponding to the maximum field of view of the optical lens satisfy D / h / FOV≤0.015;

[0021] The optical back focus BFL of the optical lens and the optical total length TTL of the optical lens satisfy BFL / TTL≤0.6;

[0022] The total optical length TTL of the optical lens, the maximum field of view angle FOV of the optical lens and the image height h corresponding to the maximum field of view angle of the optical lens satisfy: TTL / h / FOV≤0.04.

[0023] The present invention adopts four lenses, 1GM3G architecture, and has a simple structure. While realizing the miniaturization and lightness of the vehicle-mounted lens, it greatly reduces the imaging distortion caused by the distortion of the monitoring lens, and is suitable for the requirements of vehicle-mounted monitoring imaging lenses with high distortion requirements. The optical distortion is controlled within 6%, and the imaging picture restoration is high with small distortion. The selection of glass lenses enables the optical lens to have stable environmental adaptability and stable imaging; in addition, ghosting can be effectively controlled to meet the imaging quality requirements of the monitoring lens. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic structural diagram of a specific embodiment of the wide-angle lens of the present invention;

[0025] Figure 2 is an MTF curve diagram of a specific embodiment of the present invention;

[0026] Figure 3 This is a defocus curve diagram of a specific embodiment of the present invention under a 25°C environment;

[0027] Figure 4 This is a distortion curve diagram of the imaging lens provided by the present invention. DETAILED DESCRIPTION

[0028] A small distortion monitoring optical lens, see Figure 1 : It includes a first lens L1, a second lens L2, a third lens L3, and a fourth lens L5 from the object side to the image side along the optical axis. The first lens L1 has positive focal power, and its object side surface is convex; the second lens L2 has negative focal power, and its object side surface is concave; the third lens L3 has positive focal power, and its image side surface is convex; the object side surface of the fourth lens L4 is convex; and a color filter L5, a protective glass L6, and an IMA are arranged in sequence behind the image side surface of the fourth lens L4.

[0029] It also includes a stop S, which is arranged on the object side of the first lens L1 or between any two adjacent lenses;

[0030] The fourth lens L4 specifically has positive or negative refractive power;

[0031] The first lens L1 satisfies 2<F1 / F<5, where F1 is the focal length of the first lens and F is the focal length of the entire optical system;

[0032] The first lens L1 satisfies 0.2<r1 / r2<0.8, r1 is the curvature radius of the first lens on the object side, and r2 is the curvature radius of the first lens on the image side;

[0033] The second lens L2 satisfies r3 / r4≥-0.8, where r3 is the curvature radius of the second lens on the object side, and r4 is the curvature radius of the second lens on the image side;

[0034] The second lens L2 satisfies F2 / F≥-1.5, where F2 is the focal length of the second lens and F is the focal length of the entire optical system;

[0035] The third lens L3 satisfies F3 / F≥0.5, where F3 is the focal length of the third lens and F is the focal length of the entire optical system;

[0036] The fourth lens L3 satisfies 1.0<|F4 / F|<12, F4 is the focal length of the fourth lens, and F is the focal length of the entire optical system;

[0037] The optical lens includes at least three glass spherical lenses;

[0038] When the optical lens includes only three glass spherical lenses, another lens is a glass aspherical lens, and the position of the glass aspherical lens is not limited and can be set according to requirements;

[0039] The first lens, the second lens, and the third lens are all glass spherical lenses, and the fourth lens is a glass aspherical lens;

[0040] The optical lens includes four glass spherical lenses, namely, the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 are all glass spherical lenses;

[0041] The maximum field of view FOV of the optical lens, the maximum light clearance D of the object side surface S1 of the first lens L1 corresponding to the maximum field of view of the optical lens, and the image height h corresponding to the maximum field of view of the optical lens satisfy D / h / FOV≤0.015;

[0042] The optical back focus BFL of the optical lens and the optical total length TTL of the optical lens satisfy BFL / TTL≤0.6;

[0043] The total optical length TTL of the optical lens, the maximum field of view angle FOV of the optical lens and the image height h corresponding to the maximum field of view angle of the optical lens satisfy: TTL / h / FOV≤0.04.

[0044] The aspheric surface of the lens provided in the embodiment of the present invention satisfies the following equation:

[0045]

[0046] Among them, Z(h) is the distance vector height from the vertex of the aspherical surface when the aspherical surface is at a height of h along the optical axis, c=1 / r, r represents the radius of curvature of the aspherical mirror surface, k is the cone coefficient conic, and A, B, C, D, E, F, G, and H are all high-order coefficients of the aspherical surface.

[0047] Specific embodiments, see Figure 1 , the optical parameters of each component are shown in Table 1:

[0048]

[0049]

[0050] Table 1

[0051] In Table 1, when the curvature radius of the surfaces of the aperture S, the IR filter L5, and the protective glass L6 is Infinity, it means that the surface is a plane.

[0052] The aperture S is disposed on the object side surface of the first lens L1. The object side surface of the first lens L1 is convex, and the image side surface is concave; the object side surface of the second lens L2 is concave, and the image side surface is concave; the object side surface of the third lens L3 is concave, and the image side surface is convex; the object side surface of the fourth lens L4 is convex, and the image side surface is concave.

[0053] In a specific embodiment, the aspheric coefficient values ​​of each surface are shown in Table 2:

[0054]

[0055] Table 2

[0056] In the specific embodiment, the values ​​of various parameters are shown in Table 3:

[0057] parameter TTL(mm) F(mm) D(mm) h(mm) FOV(°) BFL(mm) Numeric 10 5.57 2.6 6.185 62.1 4.576

[0058] Table 3

[0059] In this embodiment, the maximum field of view FOV of the optical lens, the maximum light clearance aperture D of the object side surface S1 of the first lens L1 corresponding to the maximum field of view of the optical lens, and the image height h corresponding to the maximum field of view of the optical lens satisfy D / h / FOV=0.0068; the optical back focus BFL of the optical lens and the total optical length TTL of the optical lens satisfy BFL / TTL=0.4576; and the total optical length TTL of the optical lens, the maximum field of view FOV of the optical lens, and the image height h corresponding to the maximum field of view of the optical lens satisfy: TTL / h / FOV=0.026.

[0060] The principle is as follows: from the object side to the image side, it includes, in sequence, a first lens with positive optical power and a convex surface facing the object side, a second lens with negative optical power and a concave surface facing the object side, a third lens with positive optical power and a convex surface facing the image side, and a fourth lens with a convex surface facing the object side. The optical lens provided can maintain the imaging quality requirements of small distortion, high resolution and stable environmental adaptability while maintaining the lens's small field of view, high detail resolution capability, and short and lightweight lens.

[0061] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0062] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A small distortion monitoring optical lens, which comprises a first lens, a second lens, a third lens, and a fourth lens in sequence from the object side to the image side along the optical axis, characterized in that: The first lens has positive power, and its object side surface is convex; the second lens has negative power, and its object side surface is concave; the third lens has positive power, and its image side surface is convex; the object side surface of the fourth lens is convex, and the fourth lens has positive power or negative power; a color filter, a protective glass, and an IMA are arranged in sequence behind the image side surface of the fourth lens; The first lens satisfies 2< F1 / F<5, F1 is the focal length of the first lens, and F is the focal length of the entire optical system; the first lens satisfies 0.2<r1 / r2<0.8, r1 is the object side curvature radius of the first lens, and r2 is the image side curvature radius of the first lens; The second lens satisfies r3 / r4≥-0.8, r3 is the curvature radius of the second lens on the object side, and r4 is the curvature radius of the second lens on the image side; the second lens satisfies F2 / F≥-1.5, F2 is the focal length of the second lens, and F is the overall focal length of the optical system; The third lens satisfies F3 / F ≥ 0.5, where F3 is the focal length of the third lens and F is the focal length of the entire optical system; The fourth lens satisfies 1.0 <|F4 / F| < 12, F4 is the focal length of the fourth lens, and F is the focal length of the entire optical system; The maximum field of view FOV of the optical lens, the maximum light clearance D of the object side surface S1 of the first lens L1 corresponding to the maximum field of view of the optical lens, and the image height h corresponding to the maximum field of view of the optical lens satisfy D / h / FOV≤0.015; The optical back focus BFL of the optical lens and the optical total length TTL of the optical lens satisfy BFL / TTL≤0.6; The total optical length TTL of the optical lens, the maximum field of view angle FOV of the optical lens and the image height h corresponding to the maximum field of view angle of the optical lens satisfy the following conditions: TTL / h / FOV≤0.

04.

2. The small distortion monitoring optical lens according to claim 1, characterized in that: The optical system further comprises an aperture, which is arranged on the object side of the first lens or between any two adjacent lenses.

3. The small distortion monitoring optical lens according to claim 1, characterized in that: The optical lens includes at least three glass spherical lenses; when the optical lens includes only three glass spherical lenses, another lens is a glass aspherical lens, and the position of the glass aspherical lens is not limited and is set according to needs; the optical lens includes four glass spherical lenses, that is, the first lens, the second lens, the third lens, and the fourth lens are all glass spherical lenses.

Images