Small foresight optical lens and imaging method

Abstract

The invention relates to a small foresight optical lens and an imaging method, the small foresight optical lens comprises an optical system, the optical system is composed of a first lens, a second lens, a third lens, a fourth lens and a fifth lens which are sequentially arranged from left to right along a light incident light path, and a diaphragm is located between the second lens and the third lens; the lenses are made of glass and plastic materials, the first lens and the third lens are glass spherical lenses, the second lens, the fourth lens and the fifth lens are plastic aspheric lenses, and the fourth lens and the fifth lens form a balsaming lens group. By reasonably distributing the focal power and the surface type of each lens, the central thickness of each lens, the axial distance between the lenses and the like, the imaging performance requirement of the lens is met, the total length of the lens and the radial size of each lens are reduced, and the miniaturization of the lens group is realized.

Description

Technical Field

[0001] This invention relates to the field of lens technology, and in particular to a small forward-looking optical lens and imaging method. Background Technology

[0002] With the rapid popularization of autonomous driving technology and Advanced Driver Assistance Systems (ADAS), forward-facing automotive cameras, as core optical components for perceiving the environment, play a crucial role in realizing functions such as lane keeping, obstacle detection, and adaptive cruise control (ACC). The high-definition imaging capability of forward-facing cameras directly affects the decision-making accuracy of ADAS systems. The operating environment of forward-facing cameras is complex and variable, requiring them to cope with extreme weather, wide temperature ranges, strong light variations, road vibrations, and gravel impacts. These conditions demand that lenses possess excellent resistance to thermal deformation, anti-glare performance, high light transmittance, and mechanical stability. Furthermore, modern automotive design emphasizes modularity and lightweighting, requiring lenses to be miniaturized and low-power to fit into the compact installation space at the front of the vehicle and reduce overall vehicle energy consumption. Existing forward-facing camera technology has several shortcomings. While all-glass lens designs perform stably in high-temperature and strong-light environments, the large number of lenses leads to high cost, weight, and complex assembly, hindering mass production and vehicle lightweighting. These limitations make it difficult for existing lenses to simultaneously meet the requirements of high performance, low cost, and automotive-grade durability. Summary of the Invention

[0003] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is to provide a small forward-looking optical lens and imaging method, which achieves clear imaging while having a small size and low manufacturing cost.

[0004] To solve the above-mentioned technical problems, the technical solution of the present invention is: a small forward-looking optical lens, wherein the optical system of the lens consists of a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged sequentially from left to right along the incident light path, with the aperture stop located between the second and third lenses; without considering the curvature caused by the aspherical coefficient, the first lens is a biconcave negative lens with a concave object side and a concave image side; the second lens is a meniscus positive lens with a convex object side and a concave image side; the third lens is a biconvex positive lens with a convex object side and a convex image side; the fourth lens is a biconcave negative lens with a concave object side and a concave image side; and the fifth lens is a biconvex positive lens with a convex object side and a convex image side; the lenses are made of glass and plastic materials, wherein the first and third lenses are glass spherical lenses, the second, fourth, and fifth lenses are plastic aspherical lenses, and the fourth / fifth lens is a cemented lens group.

[0005] Preferably, the focal length of the optical system is f, and the focal lengths of the first lens, second lens, third lens, fourth lens, and fifth lens are f1, f2, f3, f4, and f5, respectively, wherein f1, f2, f3, f4, and f5 satisfy the following ratio with f: -2.0 <f1 / f<-1.0,18.0<f2 / f<19.0,0.0<f3 / f<1.0,-2.0<f4 / f<-1.0,1.0<f5 / f<2.0。

[0006] Preferably, the first lens satisfies the following relationship: 1.3≤Nd≤1.6, Vd≥50; the second lens satisfies the following relationship: 1.3≤Nd≤1.6, Vd≤50; the third lens satisfies the following relationship: 1.7≤Nd≤2.0, Vd≤50; the fourth lens satisfies the following relationship: 1.3≤Nd≤1.6, Vd≤50; and the fifth lens satisfies the following relationship: 1.3≤Nd≤1.6, Vd≥50; where Nd is the refractive index and Vd is the Abbe constant.

[0007] Preferably, the on-axis distances between each lens satisfy the following relationships: the air gap between the first lens and the second lens is 1.0 to 1.5 mm; the air gap between the second lens and the aperture stop is 0.5 to 1.0 mm; the air gap between the aperture stop and the third lens is 0.0 to 0.5 mm; the air gap between the third lens and the fourth lens is 0.1 to 0.5 mm; and the fourth lens and the fifth lens are a cemented lens group with an air gap of 0 mm.

[0008] Preferably, the second, fourth, and fifth lenses are aspherical lenses. The equation for the aspherical curve is:

[0009]

[0010] Where Z is the distance from the vertex of the aspherical surface to the optical axis at a height of h; c is the paraxial curvature of the aspherical surface; k is the conic constant; and α1, α2, α3, α4, α5, α6, α7, and α8 are all higher-order coefficients.

[0011] Preferably, the total optical length (TTL) of the optical system and the focal length (f) of the optical system satisfy the following condition: TTL / f ≤ 3.6.

[0012] Preferably, the F-number of the optical system is ≤2.2.

[0013] Preferably, the image height H of the optical system and the focal length f of the optical system satisfy the following relationship: H / f≥0.9.

[0014] An imaging method for a small forward-looking optical lens is performed according to the following steps: light rays pass through a first lens, a second lens, an aperture stop, a third lens, a fourth lens, and a fifth lens from left to right before forming an image on the imaging surface.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] The provided compact forward-looking optical lens employs five optical elements, consisting of two glass spherical lenses and three plastic aspherical lenses forming the imaging system. The use of plastic aspherical lenses, which are significantly less expensive than glass lenses, reduces production costs while maintaining image quality. The lens's total length is less than 14 mm and its outer diameter is less than 6 mm, ensuring the optical performance of the camera assembly while reducing the overall size of the lens and improving aesthetics. The second, fourth, and fifth lenses are plastic aspherical lenses, which can balance aberrations across different fields of view, further enhancing the overall image quality of the lens.

[0017] 1. This lens has an imaging angle of more than 115 degrees and features high imaging clarity, large aperture, and low tolerance sensitivity, enabling more comprehensive monitoring of the scene outside the vehicle.

[0018] 2. By rationally matching the various optical lenses, the system structure is compact and reasonable, easy to assemble, has low tolerance sensitivity, and is more suitable for large-scale high-yield production;

[0019] 3. The use of two glass lenses combined with three glass aspherical lenses reduces costs while adapting to different environments;

[0020] 4. The chromatic aberration along each axis, the transverse chromatic aberration, and higher-order chromatic aberrations have been corrected to ensure that the imaging system can maintain high imaging quality even at large angles.

[0021] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the optical structure of an embodiment of the present invention;

[0023] Figure 2 This is an axial chromatic aberration diagram of the entire working band of this invention.

[0024] Figure 3 This is a cross-axis chromatic aberration diagram for the entire working band of this invention.

[0025] Figure 4 This is a field curvature distortion diagram for the entire working band of this invention.

[0026] In the diagram: STO - aperture stop; L1 - first lens; L2 - second lens; L3 - third lens; L4 - fourth lens; L5 - fifth lens; CG - sensor protective glass; IMA - imaging plane. Detailed Implementation

[0027] To make the above features and advantages of the present invention more apparent and understandable, specific embodiments are described below in conjunction with the accompanying drawings for detailed explanation.

[0028] like Figures 1-4 As shown, a small forward-looking optical lens is provided. The optical system of the lens consists of a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged sequentially from left to right along the incident light path. An aperture stop is located between the second and third lenses. The lenses are made of glass and plastic materials, wherein the first and third lenses are glass spherical lenses, the second, fourth, and fifth lenses are plastic aspherical lenses, and the fourth / fifth lens is a cemented lens group.

[0029] In this embodiment of the invention, the second lens is an aspherical lens with positive optical power. While adjusting large-angle light, its aspherical shape corrects spherical aberration and distortion of the optical system. The fourth and fifth lenses form an achromatic cemented doublet lens, controlling chromatic aberration within a reasonable range in the visible light band, adjusting the incident angle of light in each field of view, correcting higher-order aberrations, and improving edge image quality. This reasonable lens combination enables the optical system to achieve a small volume, large field of view, and large aperture design, while effectively correcting on-axis and off-axis aberrations, resulting in good image quality. Figures 2 to 4 As shown.

[0030] The technical specifications achieved by the optical system in this embodiment are as follows:

[0031] (1) Focal length: 3.5≤EFFL≤4.0mm;

[0032] (2) Aperture F≤2.2;

[0033] (3) Field of view: 2w ≥ 115°;

[0034] (4) Operating band: Visible light band.

[0035] To achieve the above design parameters, the specific design of the optical system adopted in this embodiment is shown in the table below:

[0036]

[0037]

[0038] The aspherical coefficients of the aspherical lenses of the optical system in this embodiment of the invention are shown in the table below:

[0039]

[0040] The optical system of this invention, by rationally allocating the optical power, surface shape, center thickness of each lens, and on-axis distance between each lens, can reduce the overall length of the lens and the radial dimensions of each lens element while meeting the lens imaging performance requirements, thereby miniaturizing the lens assembly and reducing costs.

[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A compact forward-viewing optical lens comprising an optical system, characterized in that: The optical system of the lens is composed of a first lens, a second lens, a diaphragm, a third lens, a fourth lens and a fifth lens arranged in sequence from left to right along the light incident path, wherein, without considering the reverse bending caused by the aspherical surface coefficient, the first lens is a double-concave negative lens, the second lens is a meniscus positive lens, the third lens is a double-convex positive lens, the fourth lens is a double-concave negative lens, and the fifth lens is a double-convex positive lens.

2. A compact front-view optical lens according to claim 1, characterized in that: The object side surface of the first lens is concave, 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 convex, and the image side surface is convex; the object side surface of the fourth lens is concave, and the image side surface is concave; and the object side surface of the fifth lens is convex, and the image side surface is convex.

3. A compact front-view optical lens according to claim 1, characterized in that: The focal length of the optical system is f, and the focal lengths of the first lens, the second lens, the third lens, the fourth lens and the fifth lens are f1, f2, f3, f4 and f5 respectively, wherein f1, f2, f3, f4 and f5 satisfy the following ratios: -2.0 < f1 / f < -1.0, 18.0 < f2 / f < 19.0, 0.0 < f3 / f < 1.0, -2.0 < f4 / f < -1.0 and 1.0 < f5 / f < 2.

0. The first lens satisfies the relationship: 1.3 ≤ Nd ≤ 1.6, Vd ≥ 50; the second lens satisfies the relationship: 1.3 ≤ Nd ≤ 1.6, Vd ≤ 50; the third lens satisfies the relationship: 1.7 ≤ Nd ≤ 2.0, Vd ≤ 50; the fourth lens satisfies the relationship: 1.3 ≤ Nd ≤ 1.6, Vd ≤ 50; and the fifth lens satisfies the relationship: 1.3 ≤ Nd ≤ 1.6, Vd ≥ 50; wherein Nd is the refractive index, and Vd is the Abbe number.

4. A compact front-view optical lens according to claim 1, characterized in that: The on-axis distance between each lens satisfies the following relationship: the air gap between the first lens and the second lens is 1.0-1.5 mm; the air gap between the second lens and the diaphragm is 0.5-1.0 mm; the air gap between the diaphragm and the third lens is 0.0-0.5 mm; the air gap between the third lens and the fourth lens is 0.1-0.5 mm; the fourth lens and the fifth lens are a cemented lens group, and the air gap is 0.

5. A compact front-view optical lens according to claim 1, characterized in that: The second lens, the fourth lens and the fifth lens are aspherical lenses. The aspherical curve equation is expressed as:

6. A compact front-view optical lens according to claim 1, characterized in that: wherein Z is the sagittal height of the aspherical surface at a height of h along the optical axis; c is the paraxial curvature of the aspherical surface; k is the conic constant; and α1, α2, α3, α4, α5, α6, α7 and α8 are high-order coefficients. The total optical length TTL of the optical system and the focal length f of the optical system satisfy: TTL / f ≤ 3.

6.

7. A compact front-view optical lens according to claim 1, characterized in that: The F number of the optical system is ≤2.

2.

8. A compact front-view optical lens according to claim 1, characterized in that: The image height H of the optical system and the focal length f of the optical system satisfy: H / f ≥ 0.

9.

9. A compact front-view optical lens according to claim 1, characterized in that: The light rays pass through the first lens, the second lens, the diaphragm, the third lens, the fourth lens and the fifth lens in sequence from left to right and then are imaged on the imaging plane.

10. An imaging method applied to the compact forward-viewing optical lens of claim 2, characterized in that, ​

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