DMS optical lens based on infrared image and imaging method thereof

Abstract

The application relates to a DMS optical lens based on an infrared image and an imaging method thereof. An 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 an optical path of light incidence. The first lens is a plano-convex positive lens, the second lens is a meniscus concave negative lens, the third lens is a double-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 application adopts four optical lenses, that is, one glass spherical lens and three plastic aspherical lenses to form an imaging system, so that the total length of the lens and the radial size of each lens are reduced, and the purpose of miniaturization of the lens group and cost reduction is achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lenses, and particularly relates to a DMS optical lens based on an infrared image and an imaging method thereof. BACKGROUND

[0002] Since the 21st century, the rapid development of artificial intelligence, information technology and electronic technology has promoted the rise of intelligent vehicles in the field of the automobile industry. Among them, technologies such as autonomous driving, intelligent cockpit and advanced driving assistance system have been rapidly developed and applied. The driver monitoring system, as a necessary system for protecting driving safety and realizing human-vehicle interaction, and a research hotspot in the field of intelligent vehicles, is mainly used to monitor the state and dangerous driving behavior of the driver, including but not limited to fatigue, smoking and making phone calls. Among them, the driver monitoring system based on visual information such as visible light images and infrared images is the current mainstream technical solution, which is required to be used normally in all-weather 24 hours as a kind of in-vehicle monitoring, such as day and night confocal, high and low temperature stability, etc. On this basis, it is also required to guarantee its high resolution, large aperture and low distortion optical performance, so the market adopts glass lenses for design or releases the volume, resulting in high cost or being not conducive to integration under the restriction of small volume. SUMMARY

[0003] The application improves the prior art, and the technical problem to be solved by the application is to provide a DMS optical lens based on an infrared image and an imaging method thereof.

[0004] In order to achieve the above purpose, the technical scheme adopted by the application is as follows: a DMS optical lens based on an infrared image, an 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 incident path, the first lens is a plano-convex positive lens, the second lens is a meniscus concave negative lens, the third lens is a double-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.

[0005] Further, the object side of the first lens is a convex surface, and the image side is a plane; the object side of the second lens is a convex surface, and the image side is a concave surface; the object side of the third lens is a convex 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.

[0006] Further, 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.

[0007] Further, the first lens satisfies the relationship: 1.5 ≤ N d ≤ 1.8, and V d ≤ 50.0; the second lens satisfies the relationship: 1.5 ≤ N d ≤ 1.8, and V d ≥ 50.0; the third lens satisfies the relationship: 1.5 ≤ N d ≤ 1.8, and V d ≥ 50.0; and the fourth lens satisfies the relationship: 1.5 ≤ N d ≤ 1.8, and V d ≥ 50.0; wherein N d is the refractive index, and V d is the Abbe number.

[0008] Further, the air gap between the first lens and the second lens is 0.0-0.5 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.

[0009] Further, the aspherical surface curve equation expressions of the second lens, the third lens and the fourth lens are:

[0010]

[0011] wherein Z is the sagittal height of the aspherical surface at a height of h along the optical axis from the vertex of the aspherical surface; 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.

[0012] Further, the optical total length TTL of the optical system and the focal length f of the optical system satisfy: TTL / f ≤ 1.6.

[0013] Further, the F number of the optical system is ≤2.0; and the image height H of the optical system and the focal length f of the optical system satisfy: H / f ≥ 0.5.

[0014] Further, the diaphragm is located on the object side of the first lens; and the rear side of the fourth lens is provided with a first equivalent glass flat plate and a second equivalent glass flat plate.

[0015] Another technical solution adopted in this invention is: an imaging method for a DMS optical lens based on infrared images, wherein during imaging: light enters from left to right through the aperture stop, the first lens, the second lens, the third lens, the fourth lens, the first equivalent glass plate, and the second equivalent glass plate, and then forms an image on the imaging surface.

[0016] Compared with the prior art, the present invention has the following effects: The present invention uses four optical lenses, consisting of one glass spherical lens and three plastic aspherical lenses to form an imaging system, thereby reducing the total length of the lens and the radial dimensions of each lens, so as to achieve the purpose of miniaturization of the lens assembly and reduction of cost. Attached image description:

[0017] Figure 1 This is a schematic diagram of the optical structure according to an embodiment of the present invention;

[0018] Figure 2 This is an axial chromatic aberration diagram of the entire working band of this invention.

[0019] Figure 3 This is a transverse chromatic aberration diagram of the entire working band of this invention.

[0020] Figure 4 This is a field curvature distortion diagram of the entire working band according to an embodiment of the present invention.

[0021] In the picture:

[0022] STO - Aperture stop; L1 - First lens; L2 - Second lens; L3 - Third lens; L4 - Fourth lens; L5 - First equivalent glass plate; L6 - Second equivalent glass plate; IMA - Imaging surface. Detailed implementation method:

[0023] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0024] like Figure 1 As shown, this invention discloses a DMS optical lens based on infrared images. While meeting optical characteristics such as high resolution, large aperture, and low distortion, it also meets the requirements of small size, low production cost, and 24 / 7 all-weather operation. Specifically, the lens's optical system consists of an aperture stop STO, a first lens L1, a second lens L2, a third lens L3, and a fourth lens L4, arranged sequentially from left to right along the incident light path. The aperture stop is located on the object-side surface of the first lens. The first lens L1 is a plano-convex positive lens, the second lens L2 is a meniscus concave negative lens, the third lens L3 is a biconvex positive lens, and the fourth lens L4 is a meniscus concave negative lens. The first lens is a glass spherical lens, while the second, third, and fourth lenses are all plastic aspherical lenses. Figures 2 to 4As shown, by proper lens matching, various aberration problems of the system are effectively optimized, and the imaging quality is improved.

[0025] In this embodiment, the object side surface of the first lens is convex, the image side surface is flat; the object side surface of the second lens is convex, the image side surface is concave; the object side surface of the third lens is convex, the image side surface is convex; the object side surface of the fourth lens is convex, the image side surface is concave.

[0026] In this embodiment, 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, -1.0 < f4 / f < 0.0.

[0027] In this embodiment, 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, and V d is the Abbe number.

[0028] In this embodiment, the on-axis distance between each lens satisfies the following relationship: the air gap between the first lens and the second lens is 0.0-0.5mm; the air gap between the second lens and the third lens is 0.0-0.5mm; the air gap between the third lens and the fourth lens is 0.0-0.5mm. In the case of meeting the imaging requirements, reducing the distance between each lens is conducive to the optical total length of the lens, ensuring miniaturization.

[0029] In this embodiment, the aspherical surface curve equation expressions of the second lens, the third lens and the fourth lens are:

[0030]

[0031] wherein Z is the sagittal height of the aspherical surface at a height of h along the optical axis from the vertex of the aspherical surface; 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.

[0032] In this embodiment, the aspherical coefficients of each aspherical lens of the optical system are as follows:

[0033]

[0034] In this embodiment, the total optical length TTL of the optical system and the focal length f of the optical system satisfy: TTL / f≤1.6.

[0035] In this embodiment, the F number of the optical system is ≤2.0.

[0036] In this embodiment, the image height H of the optical system and the focal length f of the optical system satisfy: H / f≥0.5.

[0037] In this embodiment, the rear side of the fourth lens is provided with a first equivalent glass plate L5, and the rear side of the first equivalent glass plate L5 is provided with a second equivalent glass plate L6.

[0038] In this embodiment, the technical indicators achieved by the optical system are as follows:

[0039] (1) focal length: 3.5≤EFFL≤4.0mm;

[0040] (2) aperture F≤2.0;

[0041] (3) field of view angle: 2w≥60°;

[0042] (4) working waveband: 940nm short-wave infrared waveband.

[0043] To achieve the above design parameters, the specific design of the optical system in this embodiment is shown in the following table:

[0044]

[0045] In this embodiment, the imaging method of the DMS optical lens based on infrared images is as follows: when imaging, light rays enter the stop STO, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the first equivalent glass plate L5, and the second equivalent glass plate L6 from left to right, and then are imaged on the imaging surface.

[0046] In this embodiment, the optical system reasonably allocates the optical power, surface shape, central thickness of each lens, and axial distance between each lens, so that the design meets the requirements of lens imaging performance, adopts a structure form combining plastic aspherical lenses and glass spherical lenses, reduces the total length of the lens and the radial size of each lens, and achieves the purposes of miniaturization of the lens group and cost reduction.

[0047] The application has the advantages that four optical lenses are adopted, one glass spherical lens and three plastic aspherical lenses are adopted to form an imaging system, the plastic aspherical lenses with a cost much lower than the glass lenses are adopted to reduce the production cost while ensuring the imaging quality, the total length of the lens is less than 7mm and the outer diameter is less than 6mm, the optical performance of the camera group is ensured while the overall size of the lens is reduced and the aesthetic degree is improved, in addition, one glass spherical lens is arranged in the first to fourth lenses to control the temperature drift and improve the influence of high temperature or low temperature on the image quality of the lens, and the spherical lens is adopted to further reduce the cost.

[0048] If the application discloses or relates to mutually fixed connecting parts or structural parts, the fixed connection can be understood as: detachable fixed connection (such as bolt or screw connection), and can also be understood as: non-detachable fixed connection (such as riveting, welding), of course, the mutually fixed connection can also be replaced by an integral structure (such as using casting process to integrally form) (obviously, the integral forming process cannot be used).

[0049] In addition, the terms used to represent the position relationship or shape in any of the technical solutions disclosed in the application include the approximate, similar or close state or shape unless otherwise stated.

[0050] Any component provided by the application can be assembled from multiple individual components, or can be a single component manufactured by integral forming process.

[0051] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the application and not to limit them; although the application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the specific embodiments of the application can be modified or some technical features can be replaced by equivalents; without departing from the spirit of the technical solutions of the application, they should be covered in the technical solution range of the application claimed by the application.

Claims

1. An infrared image-based DMS optical lens, 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, the first lens is a plano-convex positive lens, the second lens is a meniscus concave negative lens, the third lens is a double-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 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; 3.5mm ≤ f ≤ 4.0mm; the optical total length TTL of the optical system and the focal length f of the optical system satisfy: TTL / f ≤ 1.6; the working waveband of the DMS optical lens is a 940nm short-wave infrared waveband.

2. The DMS optical lens based on infrared images according to claim 1, characterized in that: The object side of the first lens is a convex surface, and the image side is a plane; the object side of the second lens is a convex surface, and the image side is a concave surface; the object side of the third lens is a convex 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.

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; and the fourth lens satisfies the relationship: 1.5 ≤ N d ≤ 1.8, V d ≥ 50.0; wherein N d is the refractive index, and V d is the Abbe number.

4. The DMS optical lens based on infrared images according to claim 1, characterized in that: The air gap between the first lens and the second lens is 0.0-0.5mm; 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.

5. The DMS optical lens based on infrared images according to claim 1, characterized in that: The aspherical surface curve equation expression of the second lens, the third lens and the fourth lens is: wherein z is the sagittal height of the aspheric surface from the vertex of the aspheric surface at a position along the optical axis at a height h; c is the paraxial curvature of the aspheric surface; k is a conic constant; and α1, α2, α3, α4, α5, α6, α7, and α8 are higher order coefficients.

6. The DMS optical lens based on infrared images according to claim 1, characterized in that: The F number of the optical system is ≤2.0; and the image height H of the optical system and the focal length f of the optical system satisfy: H / f ≥ 0.

5.

7. The DMS optical lens based on infrared images according to claim 1, characterized in that: The diaphragm is located on the object side of the first lens; and the rear side of the fourth lens is provided with a first equivalent glass flat plate and a second equivalent glass plate.

8. An imaging method of a DMS optical lens based on an infrared image, characterized in that: The DMS optical lens based on infrared images comprises the first lens, the second lens, the third lens and the fourth lens, and when imaging, light enters the diaphragm, the first lens, the second lens, the third lens, the fourth lens, the first equivalent glass flat plate and the second equivalent glass plate from left to right and is imaged on the imaging surface.

Images