DMS optical lens based on infrared image and imaging method

Abstract

The application relates to a DMS optical lens based on an infrared image, and the optical system of the lens is composed of a first lens, a second lens, a third lens and a fourth lens arranged in sequence from left to right along the light path of light incidence, and a diaphragm is arranged on the S1 surface of the lens L1. The first lens is a glass spherical lens, and the second, third and fourth lenses are plastic 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 requirement is met, the structure form of combining the plastic aspherical lens and the glass spherical lens 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 lens, in particular to a DMS optical lens based on infrared image and imaging method. BACKGROUND

[0002] Fatigue driving and distraction are important reasons for traffic accidents and fatal accidents. According to the estimate of the American Automobile Association Traffic Safety Foundation, 30% of the fatal motor vehicle accidents in the United States in 2016 were caused by fatigue driving or distraction of the driver. The introduction of the driver monitoring system can effectively reduce the occurrence of such conditions. Among all its technical solutions, the driver monitoring system based on visual information such as visible light image and infrared image is the current mainstream technical solution. As a requirement for 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, etc. Optical performance, so the market is limited in small volume, and glass lenses are designed or the volume is opened, resulting in high cost or not conducive to integration. SUMMARY

[0003] In view of the deficiencies of the prior art, the technical problem to be solved by the present application is to provide a DMS optical lens based on infrared image, which meets the requirements of small size, low production cost and all-weather 24-hour normal use while meeting the requirements of high resolution, large aperture and low distortion and other optical characteristics.

[0004] In order to solve the above technical problems, the technical scheme of the present application is: a DMS optical lens based on infrared image, the optical system of the lens is composed of a diaphragm, a first lens, a second lens, a third lens and a fourth lens arranged in order from left to right along the light incident path, in the case of not 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 double-concave negative lens, the object side is concave, and the image side is concave; the third lens is a meniscus convex positive lens, the object side is concave, and the image side is convex; the fourth lens is a meniscus concave negative lens, the object side is convex, and the image side is concave; the first lens is a glass spherical lens, and the second lens, the third lens and the fourth lens are plastic aspherical lenses.

[0005] Preferably, 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, wherein f1, f2, f3 and f4 satisfy the following proportions: 1.0 < f1 / f < 2.0, -2.0 < f2 / f < -1.0, 0.0 < f3 / f < 1.0, -1.0 < f4 / f < 0.0.

[0006] Preferably, the first lens satisfies the relationship: 1.5≤N d ≤1.8, V d ≥50.0; the second lens satisfies the relationship: 1.5≤N d ≤1.8, V d ≤50.0; the third lens satisfies the relationship: 1.5≤N d ≤1.8, V d ≥50.0; the fourth lens satisfies the relationship: 1.5≤N d ≤1.8, V d ≥50.0; wherein N d is the refractive index, V d is the Abbe number.

[0007] Preferably, the air gap between the first lens and the second lens is 0.5-1.0mm; the air gap between the second lens and the third lens is 0.0-0.5mm; and the air gap between the third lens and the fourth lens is 0.0-0.5mm.

[0008] Preferably, the second lens, the third lens and the fourth lens are all aspherical lenses, and the aspherical curve equation is:

[0009]

[0010] wherein Z is the sagittal height of the aspherical surface at a height of r 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.

[0011] Preferably, the total optical length TTL of the optical system and the focal length f of the optical system satisfy the relationship: TTL / f≤2.0.

[0012] Preferably, the F number of the optical system is ≤2.5.

[0013] Preferably, the image height H of the optical system and the focal length f of the optical system satisfy the relationship: H / f≤1.0.

[0014] Preferably, a filter is arranged on the right side of the fourth lens, and the filter is an equivalent glass flat.

[0015] An imaging method of a DMS optical lens based on an infrared image is performed according to the following steps: light rays pass through a diaphragm, a first lens, a second lens, a third lens and a fourth lens in sequence from left to right, and then are imaged on an imaging surface.

[0016] Compared with the prior art, the present application has the following beneficial effects:

[0017] 1. The lens has an imaging angle of the object greater than 46.4 degrees, and has the advantages of high imaging definition, large light aperture, low tolerance sensitivity, good high and low temperature stability, etc., and can monitor the scene outside the vehicle more comprehensively;

[0018] 2. The imaging system is composed of one glass spherical lens and three plastic aspherical lenses. The plastic aspherical lenses have a cost much lower than the glass lenses, and can ensure the imaging quality while reducing the production cost. Through reasonable matching of the optical lenses, the system structure is compact and reasonable, the total length is 8mm, easy to assemble, low tolerance sensitivity, and more suitable for large-scale high-yield production;

[0019] 3. The glass-plastic hybrid structure has low manufacturing cost and light weight, which is beneficial to the manufacturing and installation of the module;

[0020] 4. The focusing surface displacement can be compensated well at high and low temperatures, and the system has good adaptability to complex environments;

[0021] 5. The axial color difference, sagittal color difference and high-order color difference are corrected, so that the imaging system can also have high imaging quality at a large angle.

[0022] 6. The advantages of aspherical lenses in correcting aberrations are fully utilized, the high-definition imaging is met, the lens outer diameter is smaller, and the optical total length is shorter, so that the miniaturization of the lens is ensured, the lens body length is less than 7mm, and the lens outer diameter is less than 6mm, which ensures the optical performance of the camera module and reduces the overall size of the lens, and improves the aesthetic appearance.

[0023] 7. The lens is provided with a glass spherical lens in the first to fourth lenses, which controls the temperature drift and improves the influence of high temperature or low temperature on the image quality of the lens, and the cost is further reduced due to the use of the spherical lens.

[0024] The application will be further described in detail in combination with the drawings and specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0025] Fig. 1 The optical structure of the embodiment of the application is shown in the figure;

[0026] Fig. 2 The full working waveband axial color difference graph of the embodiment of the application is shown in the figure;

[0027] Fig. 3 The full working waveband sagittal color difference graph of the embodiment of the application is shown in the figure;

[0028] Fig. 4 The full working waveband field curvature distortion graph of the embodiment of the application is shown in the figure.

[0029] In the figure: STO-optical stop; L1-first lens; L2-second lens; L3-third lens; L4-fourth lens; L5-equivalent glass flat plate; IMA-imaging plane. DETAILED DESCRIPTION

[0030] In order to make the above features and advantages of the present application more obvious and easy to understand, the following specific examples are described in detail below with reference to the accompanying drawings.

[0031] As shown in Figs. 1-4 , a DMS optical lens based on infrared image, the optical system of the lens is composed of an optical stop, a first lens, a second lens, a third lens and a fourth lens arranged in sequence from left to right along the light incident path, and the optical stop is arranged on the S1 surface of the lens L1. As shown in Figs. 2 to 4 , by reasonable lens matching, the various aberration problems of the system are effectively optimized, and the imaging quality is improved.

[0032] In the embodiment of the present application, the on-axis distance between each lens satisfies the following relationship: the air gap between the first lens and the second lens is 0.5-1.0 mm; the air gap between the second lens and the third lens is 0.0-0.5 mm; and the air gap between the third lens and the fourth lens is 0.0-0.5 mm. In the case of meeting the imaging requirements, reducing the distance between each lens is beneficial to the total length of the lens, and ensures miniaturization.

[0033] The technical indicators realized by the optical system of the embodiment are as follows:

[0034] (1) focal length: 5.0≤EFFL≤6.0 mm;

[0035] (2) aperture F≤2.5;

[0036] (3) field of view angle: 2w≥56.4°;

[0037] (4) working waveband: 940 nm short-wave infrared waveband.

[0038] In order to realize the above design parameters, the specific design adopted by the optical system of the embodiment is shown in the following table:

[0039]

[0040]

[0041] The aspheric coefficients of each aspheric lens of the optical system of the embodiment are as follows:

[0042]

[0043] The optical system of the embodiment can make the design meet the requirements of the imaging performance of the lens, adopt the structure of combining the plastic aspheric lens and the glass spherical lens, reduce the total length of the lens and the radial dimension of each lens, and achieve the miniaturization of the lens group and the reduction of the cost by reasonably allocating the focal power, the surface type of each lens, the central thickness of each lens, and the axial distance between each lens.

[0044] The above is only the preferred embodiment of the present application, and is not intended to limit the present application in other forms. Any skilled person in the art can modify or change the above disclosed technical content to equivalent embodiments. However, any simple modification, equivalent change and modification of the above embodiments made according to the technical essence of the present application without departing from the technical solution of the present application still falls within the protection scope of the present application.

Claims

1. An infrared image-based DMS optical lens comprising an optical system, characterized in that: The optical system of the lens is composed of a diaphragm, a first lens, a second lens, a third lens and a fourth lens arranged in sequence from left to right along the light path of the incident light rays, wherein the first lens is a meniscus convex positive lens, the second lens is a double-concave negative lens, the third lens is a meniscus convex positive lens, and the fourth lens is a meniscus concave negative lens. The first lens is a glass spherical lens, and the second lens, the third lens and the fourth lens are plastic aspherical lenses. The object side of the first lens is a convex surface, and the image side is a concave surface; the object side of the second lens is a concave surface, and the image side is a concave surface; the object side of the third lens is a concave surface, and the image side is a convex surface; and the object side of the fourth lens is a convex surface, and the image side is a concave surface. The air gap between the first lens and the second lens is 0.800 mm; the air gap between the second lens and the third lens is 0.209 mm; and the air gap between the third lens and the fourth lens is 0.100 mm.

2. The DMS optical lens based on infrared images 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, wherein f1, f2, f3 and f4 satisfy the following ratios: 1.0 < f1 / f < 2.0, -2.0 < f2 / f < -1.0, 0.0 < f3 / f < 1.0, and -1.0 < f4 / f < 0.

0.

3. The DMS optical lens based on infrared images according to claim 1, characterized in that: The first lens satisfies the relationship: 1.5 ≤ N d ≤ 1.8, V d ≥ 50.0; the second lens satisfies the relationship: 1.5 ≤ N d ≤ 1.8, V d ≤ 50.0; the third lens satisfies the relationship: 1.5 ≤ N d ≤ 1.8, V d ≥ 50.0; the fourth lens satisfies the relationship: 1.5 ≤ N d ≤ 1.8, V d ≥ 50.0; where N d is the refractive index, V d is the Abbe number.

4. The DMS optical lens based on infrared images according to claim 1, characterized in that: The second lens, the third lens and the fourth lens are aspherical lenses, and the aspherical curve equation is as follows: wherein Z is the sagittal height of the aspherical surface at a height of r along the optical axis; c is the paraxial curvature of the aspherical surface; k is the conic constant; 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 the following relationship: TTL / f ≤ 2.

0.

5. The DMS optical lens based on infrared images according to claim 1, characterized in that: The F number of the optical system is ≤ 2.

5.

6. The DMS optical lens based on infrared images 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 relationship: H / f ≤ 1.

0.

7. The DMS optical lens based on infrared images according to claim 1, characterized in that: The light rays pass through the diaphragm, the first lens, the second lens, the third lens and the fourth lens in sequence from left to right and then form an image on the imaging plane.

8. An imaging method applied to the DMS optical lens based on infrared image of claim 1, characterized in that, ​

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