Three-piece small-size DMS optical lens and imaging method thereof

Abstract

The invention relates to a three-piece small-size DMS optical lens and an imaging method thereof, an optical system of the lens is composed of a first lens, a diaphragm, a second lens and a third lens which are sequentially arranged from left to right along a light incident light path, the first lens is a meniscus convex positive lens, the second lens is a meniscus convex positive lens, and the third lens is a meniscus convex positive lens. The first lens is a glass aspheric lens, and the second lens and the third lens are both plastic aspheric lenses. The three optical lenses are adopted, one glass aspheric lens and two plastic aspheric lenses form an imaging system, the optical characteristics of high resolution, large aperture, low distortion and the like are met, and meanwhile the requirements of small size, low production cost and 24-hour normal use are met.

Description

Technical fields: This invention belongs to the field of lens technology, and in particular relates to a three-element small-volume DMS optical lens and its imaging method. Background technology: As governments worldwide increasingly focus on traffic safety issues caused by poor driving habits, many countries and regions have successively introduced regulations and industry standards related to Driver Monitoring Systems (DMS) for passenger and commercial vehicles in recent years. These efforts aim to effectively reduce traffic accident rates through regulations and other administrative means, while also strongly promoting the development of the DMS market. Among existing DMS technologies, driver monitoring systems based on visual information (such as visible light and infrared images) are currently the mainstream solution. As a type of in-vehicle monitoring, these systems require lenses that can operate normally 24 / 7 while maintaining day and night focus and high stability at high and low temperatures. Furthermore, they must also guarantee high resolution, large aperture, and low distortion optical performance. Because the market often uses glass lenses or relaxes size constraints to limit the design, this leads to increased costs or hinders integration. Summary of the Invention: The present invention addresses the problems existing in the prior art, namely, the technical problem to be solved by the present invention is to provide a three-element small-volume DMS optical lens and its imaging method.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is: a three-element small-volume DMS optical lens, wherein the optical system of the lens consists of a first lens, an aperture, a second lens, and a third lens arranged sequentially from left to right along the incident light path. The first lens is a meniscus positive lens, the second lens is a meniscus positive lens, and the third lens is a meniscus negative lens. The first lens is a glass aspherical lens, and the second and third lenses are both plastic aspherical lenses.

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

[0006] Furthermore, the focal length of the optical system is The focal lengths of the first lens, the second lens, and the third lens are respectively , , ,in , , and Meets the following ratio: 1.0 < / <2.0, 0.0< / <1.0, -2.0< / <-1.0.

[0007] Furthermore, the first lens satisfies the relationship: 1.5 ≤ ≤1.8, ≤50.0; The second lens satisfies the relationship: 1.5≤ ≤1.8, ≤50.0; The third lens satisfies the relationship: 1.5≤ ≤1.8, ≥50.0; of which For refractive index, Let be Abbe's constant.

[0008] Furthermore, 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 0.5~1.0mm; and the air gap between the second lens and the third lens is 0.0~0.5mm.

[0009] Furthermore, the equations for the aspherical curves of the first lens, the second lens, and the third lens are as follows: Where Z is the distance vector from the vertex of the aspherical surface along the optical axis at a position of height h; c is the paraxial curvature of the aspherical surface; and k is the conic constant. , , , , , , , All are coefficients of higher-order terms.

[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 ≤ 1.6.

[0011] Furthermore, the F-number of the optical system is ≤2.0; the image height H of the optical system and the focal length f of the optical system satisfy the condition: H / f≥0.5.

[0012] Furthermore, the aperture stop of the optical system is located behind the first lens; a filter is provided on the rear side of the third lens.

[0013] Another technical solution adopted in this invention is: an imaging method for a three-element small-volume DMS optical lens, wherein during imaging: light enters the first lens, aperture, second lens, third lens and filter from left to right and then forms an image on the imaging surface.

[0014] Compared with the prior art, the present invention has the following advantages: The present invention uses three optical lenses, consisting of one glass aspherical lens and two plastic aspherical lenses to form an imaging system, which not only meets the optical characteristics of high resolution, large aperture and low distortion, but also meets the requirements of small size, low production cost and normal use 24 hours a day. Attached image description: Figure 1 This is a schematic diagram of the optical structure according to an embodiment of the present invention; Figure 2 This is an axial chromatic aberration diagram of the entire working band of this invention. Figure 3 This is a cross-axis chromatic aberration diagram of the entire working band of this invention. Figure 4 This is a field curvature distortion diagram of the entire working band of this invention embodiment; In the picture: STO - Aperture stop; L1 - First lens; L2 - Second lens; L3 - Third lens; L4 - First equivalent glass plate; L5 - Second equivalent glass plate; IMA - Imaging surface. Detailed implementation method: The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0017] like Figure 1 As shown, this invention discloses a three-element compact DMS optical lens that, while meeting optical characteristics such as high resolution, large aperture, and low distortion, also requires small size, low production cost, and 24 / 7 all-weather operation. Specifically, the optical system of the lens consists of a first lens, an aperture stop, a second lens, and a third lens arranged sequentially from left to right along the incident light path. The first lens is a meniscus convex positive lens with a convex object-side surface and a concave image-side surface; the second lens is a meniscus convex positive lens with a concave object-side surface and a convex image-side surface; and the third lens is a meniscus concave negative lens with a convex object-side surface and a concave image-side surface. The three lenses are made of glass and plastic materials, wherein the first lens is a glass aspherical lens, and the second and third lenses are both plastic aspherical lenses. Figures 2 to 4 As shown, by using appropriate lens combinations, various aberrations in the system are effectively optimized, and the system size is reduced.

[0018] In this embodiment, the focal length of the optical system is The focal lengths of the first lens, the second lens, and the third lens are respectively , , ,in , , and Meets the following ratio: 1.0 < / <2.0, 0.0< / <1.0, -2.0< / <-1.0.

[0019] In this embodiment, the first lens satisfies the relationship: 1.5 ≤ ≤1.8, ≤50.0; The second lens satisfies the relationship: 1.5≤ ≤1.8, ≤50.0; The third lens satisfies the relationship: 1.5≤ ≤1.8, ≥50.0; of which For refractive index, Let be Abbe's constant.

[0020] In this embodiment, the on-axis distances between the lenses 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 0.5~1.0mm; and the air gap between the second lens and the third lens is 0.0~0.5mm. Reducing the distance between the lenses while meeting imaging requirements is beneficial for the overall optical length of the lens and ensures miniaturization.

[0021] In this embodiment, the equations for the aspherical curves of the first lens, the second lens, and the third lens are as follows: Where Z is the distance vector from the vertex of the aspherical surface along the optical axis at a position of height h; c is the paraxial curvature of the aspherical surface; and k is the conic constant. , , , , , , , All are coefficients of higher-order terms.

[0022] The aspherical coefficients of the aspherical lenses in the optical system of this embodiment are shown in the table below: 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≤1.6.

[0023] In this embodiment, the F-number of the optical system is ≤2.0; the image height H of the optical system and the focal length f of the optical system satisfy the condition: H / f≥0.5.

[0024] In this embodiment, the aperture stop of the optical system is located behind the first lens.

[0025] In this embodiment, a filter is provided on the rear side of the third lens. The filter consists of two equivalent glass plates, including a first equivalent glass plate L4 and a second equivalent glass plate L5 distributed from left to right.

[0026] In this embodiment, the technical specifications achieved by the optical system are as follows: (1) Focal length: 4.5≤EFFL≤5.0mm; (2) Aperture F≤2.0; (3) Field of view: 2w ≥ 70°; (4) Operating band: 940nm shortwave infrared band.

[0027] To achieve the above design parameters, the specific design of the optical system adopted in this embodiment is shown in the table below: In this embodiment, when the optical system images, light enters the first lens, aperture, second lens, third lens and filter from left to right and then forms an image on the imaging surface.

[0028] The optical system in this embodiment rationally allocates the optical power, surface shape, center thickness of each lens, and on-axis distance between each lens. This design meets the lens imaging performance requirements while employing a structure that combines plastic aspherical lenses and glass aspherical lenses. This reduces the overall length of the lens and the radial dimensions of each lens, thereby achieving the goal of miniaturizing the lens assembly and reducing costs.

[0029] The advantages of this invention are as follows: It employs three optical lenses, consisting of one glass aspherical lens and two plastic aspherical lenses to form the imaging system. The use of plastic aspherical lenses, which are significantly cheaper than glass lenses, reduces production costs while maintaining image quality. The total lens length is less than 8 mm and the outer diameter is less than 3 mm, ensuring the optical performance of the camera assembly while reducing the overall size of the lens and improving aesthetics. Furthermore, the inclusion of a glass aspherical lens controls temperature drift, mitigating the impact of high or low temperatures on image quality, and the use of an aspherical lens further enhances image quality.

[0030] If this invention discloses or relates to components or structural parts that are fixedly connected to each other, then, unless otherwise stated, a fixed connection can be understood as: a detachable fixed connection (e.g., using bolts or screws) or a non-detachable fixed connection (e.g., riveting, welding). Of course, a fixed connection can also be replaced by an integral structure (e.g., manufactured by casting) (except where it is obviously impossible to use an integral molding process).

[0031] In addition, unless otherwise stated, the terms used in any of the technical solutions disclosed in this invention to indicate positional relationships or shapes include states or shapes that are similar to, close to, or approximate with those states or shapes.

[0032] Any component provided by this invention can be assembled from multiple individual components or can be a single component manufactured by a one-piece molding process.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A three-piece small volume DMS optical lens characterized by: The optical system of the lens is composed of a first lens, a diaphragm, a second lens and a third lens arranged in sequence from left to right along the light incident path, the first lens is a meniscus convex positive lens, the second lens is a meniscus convex positive lens, and the third lens is a meniscus concave negative lens, wherein the first lens is a glass aspheric lens, and the second lens and the third lens are plastic aspheric lenses.

2. The three-piece small volume DMS optical lens of claim 1, wherein: 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 convex surface; and the object side of the third lens is a convex surface, and the image side is a concave surface.

3. The three-piece small volume DMS optical lens of claim 1, wherein: The focal length of the optical system is , the focal lengths of the first, second and third lenses are , , , wherein , and satisfy the following ratios: 1.0 / < 2.0, 0.0 / < 1.0, -2.0 / < -1.

0.

4. The three-piece small volume DMS optical lens of claim 1, wherein: The first lens satisfies the relationship: 1.5 ≤ ≤ 1.8, ≤ 50.0; the second lens satisfies the relationship: 1.5 ≤ ≤ 1.8, ≤ 50.0; the third lens satisfies the relationship: 1.5 ≤ ≤ 1.8, ≥ 50.0; wherein is the refractive index, is the Abbe number.

5. The three-piece small volume DMS optical lens of claim 1, wherein: The air gap between the first lens and the diaphragm is 0.0-0.5 mm; the air gap between the diaphragm and the second lens is 0.5-1.0 mm; and the air gap between the second lens and the third lens is 0.0-0.5 mm.

6. The three-piece small volume DMS optical lens of claim 1, wherein: The aspheric curve equation expression of the first lens, the second lens and the third lens is as follows: Wherein, Z is the distance from the vertex of the aspheric surface to the height h along the optical axis direction; c is the paraxial curvature of the aspheric surface; k is the conic constant; 、 、 、 、 、 、 、 are high order coefficients.

7. The three-piece small volume DMS optical lens of claim 1, wherein: The optical total length TTL of the optical system and the focal length f of the optical system satisfy TTL / f≤1.

6.

8. The three-piece small volume DMS optical lens of claim 1, wherein: 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.

9. The three-piece small volume DMS optical lens of claim 1, wherein: The diaphragm of the optical system is located behind the first lens; and a filter is arranged at the rear side of the third lens.

10. An imaging method of a three-piece small volume DMS optical lens characterized by: The three-piece small-volume DMS optical lens is adopted, and when imaging, light enters the first lens, the diaphragm, the second lens, the third lens and the filter from left to right, and then is imaged on an imaging surface.

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