Low cost dms lens and imaging method

Abstract

The application relates to the technical field of lenses, in particular to a low-cost DMS lens and an imaging method, an optical system of the lens is composed of a first lens, a second lens and a third lens arranged in sequence from left to right along an optical path of light incidence, and a diaphragm is a subject side of the first lens; wherein the first lens is a spherical lens, and the second lens and the third lens are aspherical lenses. By reasonably distributing the optical power, surface type, central thickness of each lens and the axial distance between the lenses, the lens imaging performance requirements are met, the structure form of combining plastic aspherical lenses and glass spherical lenses is adopted, the total length of the lens and the radial dimension of each lens are reduced, and the purposes of miniaturization of the lens group and cost reduction are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lenses, in particular to a low-cost DMS lens and imaging method. BACKGROUND

[0002] At present, the driver monitoring system market in China is still in the development stage. Relevant data shows that the market penetration rate of the fatigue driving warning system (BAWS), one of the DMS functions, was only 5% in 2017, and the market size was only 22.2 billion yuan, far lower than the market penetration rate and size of other advanced driver assistance systems (ADAS) such as blind area detection (BSD), automatic emergency braking system (AEB) and pedestrian collision warning system (PCW). Based on the prediction that the growth rate of China's automobile production is 0-2%, by 2025, the automobile production will be 32.5 million, and based on the estimation of the price level of DMS and the penetration rate of DMS system at different stages of auxiliary driving, it is estimated that the domestic DMS market space will reach 81.6 billion yuan by 2025.

[0003] The driver monitoring DMS system is based on visual information such as visible light images and infrared images in all its technical solutions, which is the current mainstream technical solution. As a kind of in-vehicle monitoring, the lens needs to be used normally in all-weather 24 hours, such as day and night confocal, high and low temperature stability, etc. On this basis, it is also necessary to ensure its high resolution, large aperture and low distortion and other optical performance, so the market is limited in small volume and adopts glass lens for design or releases the volume, resulting in high cost or being not conducive to integration. SUMMARY

[0004] The purpose of the present application is to provide a low-cost DMS lens and imaging method, which meets the requirements of small size, low production cost and all-weather 24-hour normal use in addition to high resolution, large aperture and low distortion and other optical characteristics.

[0005] The technical solution of the present application is as follows: a low-cost DMS lens, the optical system of the lens is composed of a first lens, a second lens and a third lens arranged in order from left to right along the light incident path, and the stop is the object side of the first lens; without considering the reverse curvature caused by the aspherical coefficient, the first lens is a meniscus convex positive lens, the object side is convex, and the image side is concave; the second lens is a meniscus convex positive lens, the object side is concave, and the image side is convex; the third lens is a double-concave negative lens, the object side is concave, and the image side is concave; wherein the first lens is a spherical lens, and the second lens and the third lens are aspherical lenses.

[0006] Further, the first lens is a glass spherical lens, and the second lens and the third lens are plastic aspherical lenses.

[0007] Further, the air gap between the first lens and the second lens is 2.0-2.5mm; the air gap between the second lens and the third lens is 0.0-0.5mm.

[0008] Further, the focal length of the optical system is , the focal lengths of the first lens, the second lens and the third lens are , respectively, wherein and satisfy the following ratio: , , .

[0009] Further, the first lens satisfies the relationship: , ; the second lens satisfies the relationship: , ; the third lens satisfies the relationship: , ; wherein is the refractive index, is the Abbe number.

[0010] Further, the optical total length TTL of the optical system and the focal length f of the optical system satisfy: TTL / f≤2.0.

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

[0012] Further, the image height H of the optical system and the focal length f of the optical system satisfy: H / f≤1.0.

[0013] Further, a filter is further arranged between the right side of the third lens and the imaging surface.

[0014] A low-cost imaging method of a DMS lens, light rays from the object side to the image side pass through the first lens, the second lens, the third lens and the filter in sequence from left to right and then are imaged on the imaging surface.

[0015] Compared with the prior art, the present application has the following advantages:

[0016] 1. The lens has an imaging angle of the object greater than 52 degrees, and has the advantages of high imaging clarity, large light aperture, low tolerance sensitivity, good high-low temperature stability, etc., and can more comprehensively monitor the scene outside the vehicle.

[0017] 2. The imaging system consists of one glass spherical lens and two plastic aspherical lenses. Using plastic aspherical lenses, which are significantly cheaper than glass lenses, reduces production costs while ensuring image quality. Through the rational combination of optical lenses, the system structure is compact and reasonable, with a total length of less than 10 mm, making it easy to assemble, with low tolerance sensitivity, and more suitable for large-scale, high-yield production.

[0018] 3. The glass-plastic hybrid structure has lower manufacturing costs and lighter weight, which is beneficial for module manufacturing and installation;

[0019] 4. It can effectively compensate for focal plane displacement at high and low temperatures, and has adaptability to complex environments;

[0020] 5. 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] 6. Fully leverage the advantages of aspherical lenses in correcting aberrations, achieving high-definition imaging while featuring a smaller lens outer diameter and shorter overall optical length, ensuring lens miniaturization. The lens body length is less than 8 mm and the outer diameter is less than 4 mm, ensuring the optical performance of the camera assembly while reducing the overall size of the lens and improving aesthetics.

[0022] 7. A glass spherical lens is set in the first to third lens elements to control temperature drift and improve the effect of high or low temperature on the image quality of the lens. Furthermore, the use of a spherical lens further reduces costs. Attached Figure Description

[0023] Fig. 1 This is a schematic diagram of the optical structure of the present invention;

[0024] Fig. 2 This is the axial chromatic aberration diagram for the entire working band of this invention;

[0025] Fig. 3 This is the transverse chromatic aberration diagram for the entire working band of this invention;

[0026] Fig. 4 This is a field curvature distortion diagram for the entire working band of this invention;

[0027] In the diagram: STO - aperture stop; L1 - first lens; L2 - second lens; L3 - third lens; L4 - equivalent glass plate; IMA - imaging plane. Detailed Implementation

[0028] 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.

[0029] refer to Figs. 1 to 4

[0030] The low-cost DMS lens, the optical system of the lens is composed of a first lens L1, a second lens L2 and a third lens L3 arranged in sequence from left to right along the light path of the incident light, and the diaphragm is the object side of the first lens. Through reasonable lens matching, various aberration problems of the system are effectively optimized, and the imaging quality is improved. In the case of not considering the reverse bending caused by the aspherical coefficient, the first lens is a meniscus convex positive lens, the object side is convex, and the image side is concave; the second lens is a meniscus convex positive lens, the object side is concave, and the image side is convex; the third lens is a double-concave negative lens, the object side is concave, and the image side is concave; wherein the first lens is a glass spherical lens, and the second lens and the third lens are plastic aspherical lenses.

[0031] In the embodiment, the air gap between the first lens and the second lens is 2.0-2.5mm; the air gap between the second lens and the third lens is 0.0-0.5mm. In the case of meeting the imaging requirements, the distance between each lens is reduced, which is beneficial to the total length of the lens and ensures miniaturization.

[0032] In the embodiment, the focal length of the optical system is , the focal length of the first lens, the second lens and the third lens is , wherein and satisfy the following ratio: , , .

[0033] In the embodiment, the first lens satisfies the relationship: , ; the second lens satisfies the relationship: , ; the third lens satisfies the relationship: , ; wherein is the refractive index, is the Abbe number.

[0034] In the embodiment, the total length of the optical system TTL and the focal length f of the optical system satisfy: TTL / f≤2.0; the image height H of the optical system and the focal length f of the optical system satisfy: H / f≤1.0.

[0035] In the embodiment, a filter is further arranged between the right side of the third lens and the imaging surface, and the filter is an equivalent glass flat plate L4.

[0036] In the embodiment, the aspherical surface curve equation expression of the second lens and the third lens is:

[0037]

[0038] Wherein, Z is the sag of the aspheric surface at the position with height r along the optical axis direction from the vertex of the aspheric surface; c is the paraxial curvature of the aspheric surface; k is the conic constant; All are high order term coefficients.

[0039] In the embodiment, the technical index realized by the optical system is as follows:

[0040] (1) focal length: 7.0≤EFFL≤8.0mm;

[0041] (2) aperture F≤2.0;

[0042] (3) field of view angle: 2w≥52.6°;

[0043] (4) working waveband: 940nm short wave infrared waveband.

[0044] In the embodiment, in order to realize the above design parameters, the specific design of each lens is shown in the following table:

[0045] .

[0046] In the embodiment, the aspheric surface coefficients of each aspheric surface lens of the optical system are as follows:

[0047] .

[0048] An imaging method of a low-cost DMS lens, light rays from the object side to the image side pass through the first lens, the second lens, the third lens and the filter in sequence from left to right and then are imaged on the imaging plane.

[0049] The optical system reasonably allocates the optical power, surface shape, central thickness of each lens and the axial distance between each lens, so that the design meets the imaging performance requirements of the lens, adopts the structure form of combining plastic aspheric lenses and glass spherical lenses, reduces the total length of the lens and the radial size of each lens, and realizes the miniaturization and cost reduction of the lens group.

[0050] The above only describes the preferred embodiments of the present application, and for those skilled in the art, according to the teaching of the present application, designing a low-cost DMS lens with different forms does not need creative labor, and any equivalent change, modification, replacement and transformation made within the scope of the present application should be included in the scope of the present application.

Claims

1. A low cost DMS lens characterized in that, The optical system of the lens is composed of a first lens, a second lens and a third lens arranged in sequence along the light path of the incident light from left to right, the light passing hole of the object side of the first lens serving as the diaphragm; without considering the reverse bending caused by the aspherical coefficient, the first lens is a meniscus convex positive lens, the object side of which is a convex surface and the image side is a concave surface; the second lens is a meniscus convex positive lens, the object side of which is a concave surface and the image side is a convex surface; the third lens is a double-concave negative lens, the object side of which is a concave surface and the image side is a concave surface; wherein the first lens is a spherical lens, and the second lens and the third lens are aspherical lenses; the focal length of the optical system is , the focal lengths of the first lens, the second lens and the third lens are respectively , wherein and satisfy the following ratio: , , ; the first lens satisfies the relationship: , ; the second lens satisfies the relationship: , ; the third lens satisfies the relationship: , ; wherein is the refractive index, is the Abbe number; the optical total length TTL of the optical system and the focal length f of the optical system satisfy: TTL / f≤2.

0.

2. A low cost DMS lens according to claim 1, wherein, The first lens is a glass spherical lens, and the second lens and the third lens are plastic aspherical lenses.

3. A low cost DMS lens according to claim 1 or 2, characterized in that The air gap between the first lens and the second lens is 2.0-2.5 mm, and the air gap between the second lens and the third lens is 0.0-0.5 mm.

4. A low cost DMS lens according to claim 1, wherein, The F number of the optical system is less than or equal to 2.

0.

5. A low cost DMS lens according to claim 1, 2 or 4, wherein, The image height H of the optical system and the focal length f of the optical system satisfy H / f≤1.

0.

6. A low cost DMS lens according to claim 1, wherein, A filter is arranged between the right side of the third lens and the imaging surface.

7. An imaging method applied to the low-cost DMS lens of claim 6, characterized in that, Light rays pass through the first lens, the second lens, the third lens and the filter in sequence from the object side to the image side from left to right and then are imaged on the imaging surface.

Images