Low-cost miniaturized vehicle-mounted optical lens and imaging method thereof

Abstract

The invention relates to the technical field of lenses, in particular to a low-cost miniaturized vehicle-mounted optical lens and an imaging method thereof.The optical system of the lens is composed of a first lens, a diaphragm, a second lens, a third lens and a fourth lens which are sequentially arranged from left to right along a light incident light path; under the condition that retroflexion caused by aspheric coefficients is not considered, the first lens is a meniscus negative lens, the object side surface of the first lens is a concave surface, and the image side surface of the first lens is a convex surface; the second lens is a biconvex positive lens, the object side surface is a convex surface, and the image side surface is a convex surface; the third lens is a meniscus positive lens, the object side surface is a concave surface, and the image side surface is a convex surface; the fourth lens is a meniscus positive lens, the object side surface is a concave surface, and the image side surface is a convex surface; the second lens is a spherical lens, and the first lens, the third lens and the fourth lens are aspheric lenses. The lens can simultaneously meet the requirements of miniaturization, low cost, high image quality and the like.

Description

Technical Field

[0001] This invention relates to the field of lens technology, and in particular to a low-cost, miniaturized automotive optical lens and its imaging method. Background Technology

[0002] As a core component of advanced driver assistance systems (ADAS), the in-vehicle driver monitoring system (DMS) collects information such as the driver's facial expressions and eye status through cameras, and combines AI algorithms to identify dangerous driving behaviors such as fatigue and distraction, providing key protection for driving safety. Moreover, the demand for its installation in vehicles continues to grow due to regulatory requirements.

[0003] Existing DMS lenses have significant shortcomings: in pursuit of imaging performance, some products employ multiple glass elements or complex structures, resulting in an overall optical length often exceeding 20mm, making them bulky and difficult to fit into the limited installation space inside vehicles; the high processing cost of all-glass structures hinders large-scale applications. Although hybrid glass-plastic solutions exist, they often suffer from unreasonable lens combinations, sacrificing image quality to reduce the overall optical length, or relaxing size restrictions to maintain performance.

[0004] The contradiction between size, cost, and image quality has restricted the large-scale popularization of DMS systems, and there is an urgent need for an optical solution that balances miniaturization, low cost, and reliable performance. Summary of the Invention

[0005] The purpose of this invention is to provide a low-cost, miniaturized automotive optical lens and its imaging method, which can simultaneously meet the requirements of miniaturization, low cost, and high image quality.

[0006] The technical solution of this invention is as follows: a low-cost, miniaturized automotive optical lens, the optical system of which consists of a first lens, an aperture stop, a second lens, a third lens, and a fourth lens arranged sequentially from left to right along the incident light path; without considering the curvature caused by the aspherical coefficient, the first lens is a meniscus negative lens with a concave object side and a convex image side; the second lens is a biconvex positive lens with a convex object side and a convex image side; the third lens is a meniscus positive lens with a concave object side and a convex image side; the fourth lens is a meniscus positive lens with a concave object side and a convex image side; the second lens is a spherical lens, and the first, third, and fourth lenses are all aspherical lenses.

[0007] Furthermore, the on-axis distances between each lens satisfy the following relationships: the air gap between the first lens and the aperture stop is 0.0~0.5mm; the air gap between the aperture stop and the second lens is 0.0~0.5mm; the air gap between the second lens and the third lens is 0.5~1.0mm; and the air gap between the third lens and the fourth lens is 0.5~1.0mm.

[0008] Furthermore, the focal length of the optical system is f, and the focal lengths of the first lens, second lens, third lens, and fourth lens are f1, f2, f3, and f4, respectively, wherein f1, f2, f3, and f4 satisfy the following ratio with f: -2.0 <f1 / f<-1.0,0.0<f2 / f<1.0,0.0<f3 / f<1.0,5.0<f4 / f<6.0。

[0009] Furthermore, the first lens satisfies the following relationship: 1.4≤Nd≤1.7, Vd≥50.0; the second lens satisfies the following relationship: 1.8≤Nd≤2.1, Vd≤50.0; the third lens satisfies the following relationship: 1.4≤Nd≤1.7, Vd≥50.0; and the fourth lens satisfies the following relationship: 1.5≤Nd≤1.8, Vd≤50.0; where Nd is the refractive index and Vd is the Abbe constant.

[0010] Furthermore, the total optical length (TTL) of the optical system and the focal length (f) of the optical system satisfy the following condition: TTL / f ≤ 2.8.

[0011] Furthermore, the F-number of the optical system is ≤2.0.

[0012] Furthermore, the image height H of the optical system and the focal length f of the optical system satisfy the following condition: H / f≥0.7.

[0013] Furthermore, the second lens is a glass spherical lens, while the first, third, and fourth lenses are all plastic aspherical lenses.

[0014] Furthermore, a filter is provided on the right side of the fourth lens.

[0015] An imaging method for a low-cost, miniaturized automotive optical lens, wherein light rays pass sequentially from left to right along the incident direction through a first lens, an aperture stop, a second lens, a third lens, and a fourth lens before forming an image on the imaging surface.

[0016] Compared with the prior art, the present invention has the following advantages: 1. This lens uses four optical elements, consisting of one glass spherical lens and three plastic aspherical lenses to form the imaging system. While using plastic lenses to control production costs, the glass lenses are used to improve overall image quality and suppress temperature drift, effectively improving image stability under high and low temperature environments.

[0017] 2. The lens has a total length of less than 11.5 mm and an outer diameter of less than 6.5 mm. Its compact structure helps to improve aesthetics and system integration.

[0018] 3. In terms of optical performance, the system has an object-side field of view of more than 80 degrees, a large aperture, high image clarity, and effectively corrects axial, transverse and higher-order chromatic aberrations to ensure high-quality imaging even at large angles.

[0019] 4. This lens has low tolerance sensitivity, is easy to assemble, and is suitable for large-scale, high-yield production. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the optical structure of the present invention; Figure 2 This is the axial chromatic aberration diagram for the entire working band of this invention; Figure 3 This is the transverse chromatic aberration diagram for the entire working band of this invention; Figure 4 This is a field curvature distortion diagram for the entire working band of this invention; In the diagram: STO - aperture stop; L1 - first lens; L2 - second lens; L3 - third lens; L4 - fourth lens; L5 - filter; L6 - glass plate; IMA - imaging plane. Detailed Implementation

[0021] To make the above features and advantages of the present invention more readily understood, specific embodiments are described below in conjunction with the accompanying drawings, but the present invention is not limited thereto.

[0022] refer to Figures 1 to 4 A low-cost, miniaturized automotive optical lens comprises a first lens L1, an aperture stop STO, a second lens L2, a third lens L3, and a fourth lens L4 arranged sequentially from left to right along the incident light path. Ignoring curvature caused by aspherical coefficients, the first lens L1 is a meniscus negative lens with a concave object-side and a convex image-side; the second lens L2 is a biconvex positive lens with a convex object-side and a convex image-side; the third lens L3 is a meniscus positive lens with a concave object-side and a convex image-side; and the fourth lens L4 is a meniscus positive lens with a concave object-side and a convex image-side. The second lens L2 is a glass spherical lens, while the first lens L1, third lens L3, and fourth lens L4 are all plastic aspherical lenses.

[0023] In this embodiment, the on-axis distances between each lens satisfy the following relationships: the air gap between the first lens L1 and the aperture stop STO is 0.0~0.5mm; the air gap between the aperture stop STO and the second lens L2 is 0.0~0.5mm; the air gap between the second lens L2 and the third lens L3 is 0.5~1.0mm; and the air gap between the third lens L3 and the fourth lens L4 is 0.5~1.0mm.

[0024] In this embodiment, the focal length of the optical system is f, and the focal lengths of the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 are f1, f2, f3, and f4, respectively, wherein f1, f2, f3, f4 and f satisfy the following ratio: -2.0 <f1 / f<-1.0,0.0<f2 / f<1.0,0.0<f3 / f<1.0,5.0<f4 / f<6.0。

[0025] In this embodiment, the first lens L1 satisfies the following relationship: 1.4≤Nd≤1.7, Vd≥50.0; the second lens L2 satisfies the following relationship: 1.8≤Nd≤2.1, Vd≤50.0; the third lens L3 satisfies the following relationship: 1.4≤Nd≤1.7, Vd≥50.0; and the fourth lens L4 satisfies the following relationship: 1.5≤Nd≤1.8, Vd≤50.0; where Nd is the refractive index and Vd is the Abbe constant.

[0026] In this embodiment, the total optical length (TTL) of the optical system and the focal length (f) of the optical system satisfy the following condition: TTL / f ≤ 2.8.

[0027] In this embodiment, the F-number of the optical system is ≤2.0.

[0028] In this embodiment, the image height H of the optical system and the focal length f of the optical system satisfy the following condition: H / f≥0.7.

[0029] In this embodiment, a filter L5 and a glass plate L6 are provided on the right side of the fourth lens L4.

[0030] In this embodiment, the first lens L1, the third lens L3, and the fourth lens L4 are all aspherical lenses. The equation for the aspherical curve is: Where z is the distance from the vertex of the aspherical surface to the optical axis at a position of height r; c is the paraxial curvature of the aspherical surface; and k is the conic constant. All are coefficients of higher-order terms.

[0031] In this embodiment, the optical system effectively balances various aberrations by optimizing its structural form and optical power distribution, and fully utilizes the ability of plastic aspherical lenses to correct spherical and off-axis aberrations. This achieves system miniaturization and reduces the number of lenses, significantly lowering production costs. The lens's total length is controlled within 11.5mm, while possessing a wide field of view of over 80° and a large F2.0 aperture, resulting in superior imaging performance. Through a reasonable material combination, the system effectively suppresses chromatic aberration and temperature drift, significantly improving image quality stability under high and low temperature environments, and fully meeting the comprehensive requirements of automotive DMS lenses in terms of performance, cost, and reliability.

[0032] In this embodiment, the technical specifications achieved by the optical system are as follows: (1) Focal length: 4.0≤EFFL≤5.0mm; (2) Aperture F≤2.0; (3) Field of view: 2w ≥ 80°; (4) Operating band: shortwave near-infrared band.

[0033] In this embodiment, the specific design of the optical system to achieve the above design parameters is shown in the table below: .

[0034] In this embodiment, the aspherical coefficients of each aspherical lens in the optical system are shown in the following table: .

[0035] In the imaging method of the aforementioned low-cost miniaturized automotive optical lens, light rays pass sequentially from left to right along the incident direction through a first lens L1, an aperture stop STO, a second lens L2, a third lens L3, a fourth lens L4, a filter L5, and a glass plate L6 before forming an image on the imaging surface.

[0036] The optical system achieves miniaturization of the lens assembly and low manufacturing costs by rationally allocating the optical power, surface shape, center thickness of each lens, and on-axis distance between each lens, while meeting the lens imaging performance requirements.

[0037] The above description is only a preferred embodiment of the present invention. For those skilled in the art, designing different forms of low-cost miniaturized automotive optical lenses and their imaging methods according to the teachings of the present invention does not require creative labor. All equivalent changes, modifications, substitutions and variations made in accordance with the scope of the patent application of the present invention without departing from the principles and spirit of the present invention shall be covered by the present invention.

Claims

1. A low-cost, miniaturized automotive optical lens, characterized in that, The optical system of the lens consists of a first lens, an aperture stop, a second lens, a third lens, and a fourth lens arranged sequentially from left to right along the incident light path. Without considering the curvature caused by aspherical coefficients, the first lens is a meniscus negative lens with a concave object side and a convex image side; the second lens is a biconvex positive lens with a convex object side and a convex image side; the third lens is a meniscus positive lens with a concave object side and a convex image side; the fourth lens is a meniscus positive lens with a concave object side and a convex image side; the second lens is a spherical lens, while the first, third, and fourth lenses are all aspherical lenses.

2. The low-cost miniaturized automotive optical lens according to claim 1, characterized in that, The on-axis distances between each lens satisfy the following relationships: the air gap between the first lens and the aperture stop is 0.0~0.5mm; the air gap between the aperture stop and the second lens is 0.0~0.5mm; the air gap between the second lens and the third lens is 0.5~1.0mm; and the air gap between the third lens and the fourth lens is 0.5~1.0mm.

3. The low-cost, miniaturized automotive 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, and the fourth lens are f1, f2, f3, and f4, respectively. The ratios of f1, f2, f3, f4 and f satisfy the following: -2.0 < f1 / f < -1.0, 0.0 < f2 / f < 1.0, 0.0 < f3 / f < 1.0, and 5.0 < f4 / f < 6.

0.

4. A low-cost, miniaturized automotive optical lens according to claim 1, 2, or 3, characterized in that, The first lens satisfies the following relationship: 1.4≤Nd≤1.7, Vd≥50.0; the second lens satisfies the following relationship: 1.8≤Nd≤2.1, Vd≤50.0; the third lens satisfies the following relationship: 1.4≤Nd≤1.7, Vd≥50.0; and the fourth lens satisfies the following relationship: 1.5≤Nd≤1.8, Vd≤50.0; where Nd is the refractive index and Vd is the Abbe constant.

5. A low-cost, miniaturized automotive optical lens according to claim 1, characterized in that, The total optical length (TTL) of the optical system and the focal length (f) of the optical system satisfy the following condition: TTL / f ≤ 2.

8.

6. A low-cost, miniaturized automotive optical lens according to claim 1, characterized in that, The F-number of the optical system is ≤2.

0.

7. A low-cost, miniaturized automotive 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 the following condition: H / f≥0.

7.

8. A low-cost, miniaturized automotive optical lens according to claim 1, characterized in that, The second lens is a glass spherical lens, while the first, third, and fourth lenses are all plastic aspherical lenses.

9. A low-cost, miniaturized automotive optical lens according to claim 1, 2, 4, 5, 6, 7, or 8, characterized in that, A filter is provided on the right side of the fourth lens.

10. An imaging method applied to a low-cost, miniaturized automotive optical lens as described in any one of claims 1-9, characterized in that, The light rays pass through the first lens, aperture, second lens, third lens and fourth lens in sequence from left to right along the incident direction before forming an image on the imaging plane.

Images