DMS optical imaging lens for safe driving of automobile
By designing a DMS optical imaging lens with a 2G+2P structure, the problems of small target surface, blurred imaging, and poor high and low temperature stability were solved, achieving high-definition imaging of a large target surface and temperature stability, and reducing product costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- SHANGHAI FENGMEI OPTICAL TECH CO LTD
- Filing Date
- 2025-06-16
- Publication Date
- 2026-05-05
AI Technical Summary
Existing DMS lenses have problems such as small target surface, inability to match large target surface chips, visual blind spots, blurry images, and poor stability at high and low temperatures.
An optical imaging lens for automotive safety driving DMS was designed, including a first lens, an aperture, a second lens, a third lens, a fourth lens, a filter, and a protective glass. The lenses are combined into a 2G+2P structure to meet specific focal length, Abbe constant, and refractive index relationships, achieving a large target surface, high-definition pixels, and calorimetry-free effect.
It achieves a larger target surface coverage, clearly presents subtle changes in the driver, reduces the probability of misjudgment and missed judgment, maintains stable imaging when the temperature changes, and has a low cost.
Smart Images
Figure CN224203503U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the technical field of optical systems and vehicle imaging devices, specifically, it is an optical imaging lens for automotive safety driving DMS. Background Technology
[0002] With the development of the automotive industry, intelligentization has become a significant trend, with continuous advancements in technologies such as autonomous driving, intelligent cockpits, and advanced driver assistance systems (ADAS). Driver Monitoring System (DMS), as a crucial component of intelligent vehicles, monitors the driver's status in real time, enabling driver identification, fatigue monitoring, distraction detection, and monitoring of dangerous driving behaviors. This improves driving safety and is a necessary system for protecting driving safety and facilitating human-vehicle interaction. Research indicates that over 60% of traffic accidents are caused by driver inattention or fatigue. The DMS optical imaging lens, a key component of the DMS system, needs to clearly and accurately capture the driver's facial images, eye movements, head posture, and other information to provide high-quality image data for subsequent analysis and judgment. This allows for timely warnings to the driver in dangerous situations, reminding them to improve their driving behavior and reducing the incidence of traffic accidents.
[0003] However, current DMS lenses often suffer from problems such as small target surfaces that cannot be matched with large target surface chips, resulting in visual blind spots; blurry images that cannot clearly show subtle changes in the driver's facial expressions and eye movements; and poor high and low temperature stability, making it impossible to achieve clear imaging in complex environments. Utility Model Content
[0004] This invention proposes an optical imaging lens for automotive safety driving DMS, which features low cost, large target area, no thermalization, and high-definition pixels.
[0005] The above-mentioned technical objective of this utility model is achieved through the following technical solution: an optical imaging lens for safe driving in automobiles, which includes, in sequence along the optical axis from the object plane to the image plane: a first lens, an aperture stop, a second lens, a third lens, a fourth lens, a filter, a protective glass, and an image plane;
[0006] The first lens has a convex surface on the object side and a concave surface on the image side;
[0007] The second lens has a convex surface on both the object plane and the image plane sides;
[0008] The third lens has a convex surface on both the object plane and the image plane sides;
[0009] The fourth lens has a concave surface on the object side and a convex surface on the image side;
[0010] The third and fourth lenses form a set of cemented lenses;
[0011] And it satisfies the following relationship:
[0012] 1.3<|f1 / f|<2.4; 1.1<|f2 / f|<2.2; 0.8<|f3 / f|<1.7; 13.6<|f4 / f|<14.6;
[0013] Where f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, and f is the effective focal length of the entire optical system.
[0014] In some embodiments, the Abbe constant Vd1 of the first lens is greater than 60 and less than 72, and the Abbe constants Vd2, Vd3, and Vd4 of the second lens, the third lens, and the fourth lens are all greater than 35 and less than 47.
[0015] In some embodiments, the refractive indices of the individual lenses in the optical system satisfy the following condition:
[0016] 1.55<Nd1<1.68; 1.86<Nd2<1.97; 1.53<Nd3<1.65; 1.58<Nd4<1.69;
[0017] Wherein, Nd1 is the refractive index of the first lens, Nd2 is the refractive index of the second lens, Nd3 is the refractive index of the third lens, and Nd4 is the refractive index of the fourth lens.
[0018] In some embodiments, the maximum target surface IH of the optical system satisfies the following condition:
[0019] IH≥7.41mm.
[0020] In some embodiments, the aperture of the optical system satisfies the following condition:
[0021] F / NO = 2.0.
[0022] In some embodiments, the total length TTL of the optical system and the effective focal length f of the optical system satisfy the following condition:
[0023] 4.5≤TTL / f≤5.2.
[0024] In some embodiments, the first lens is concave-convex, with the object side being convex and the image side being concave, and its optical power is negative.
[0025] The second lens is biconvex, with a convex surface on the object side and a convex surface with a plateau on the image side, and its optical power is positive.
[0026] The third lens is biconvex, with a small convex surface on the object side and a large convex surface on the image side, and its optical power is positive.
[0027] The fourth lens is concave-convex, with the object side being concave and the image side being convex, and its optical power is negative.
[0028] In some embodiments, the aperture stop is disposed between the first lens and the second lens.
[0029] In summary, this utility model has the following beneficial effects:
[0030] This utility model has a large target area IH≥7.41mm, which can cover a wider range and completely capture the driver's upper body and even more areas of movement and posture, reducing blind spots in monitoring.
[0031] This invention features high-definition pixels, which can clearly present subtle changes in the driver's facial expressions and eye movements, helping the system to accurately judge the driver's fatigue, distraction, and other states; it provides a high-quality data foundation for subsequent image analysis and algorithm processing, reducing the probability of misjudgment and missed judgment.
[0032] This invention features heatless operation, ensuring stable imaging even with significant temperature changes without the need for refocusing, and preventing issues such as image blurring or distortion caused by temperature variations.
[0033] This utility model has low cost, adopts a 2G+2P structure design, and is designed in a cost-effective way, which reduces the cost of the product. Attached Figure Description
[0034] Figure 1 A schematic diagram of the optical system provided in an embodiment of this utility model;
[0035] Figure 2 MTF resolution diagram of the optical system provided in this embodiment of the present invention at 940 nm;
[0036] Figure 3 Defocus curve of the optical system provided in this embodiment of the present invention at a wavelength of 940nm and a temperature of 20°C;
[0037] Figure 4 Defocus curve of the optical system provided in this embodiment of the present invention at 940nm wavelength - 40℃;
[0038] Figure 5 A defocusing curve of the optical system provided in this embodiment of the present invention at a wavelength of 940nm and a temperature of 95°C;
[0039] Figure 6 Field curvature diagram of the optical system provided in this embodiment of the utility model;
[0040] Figure 7 F-THETA distortion diagram of the optical system provided in the embodiment of this utility model;
[0041] Figure 8 Standard dot matrix diagram provided for embodiments of this utility model; Detailed Implementation
[0042] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this utility model, and should not be construed as limiting this utility model.
[0043] In the description of this utility model, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.
[0044] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.
[0045] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.
[0046] like Figure 1 As shown, this embodiment provides an optical imaging lens for automotive safety driving DMS, which includes, along the optical axis from the object plane to the image plane, the following components in sequence: a first lens E1, an aperture stop STO, a second lens E2, a third lens E3, a fourth lens E4, a filter IR, a protective glass CG, and an image plane IMA.
[0047] The object plane side S1 of the first lens E1 is convex, and the image plane side S2 is concave.
[0048] The object plane side S4 of the second lens E2 is convex, and the image plane side S5 is convex.
[0049] The object plane side S6 of the third lens E3 is convex, and the image plane side S7 is convex.
[0050] The fourth lens E4 has a concave surface on the object side S7 and a convex surface on the image side S8;
[0051] The third lens E3 and the fourth lens E4 form a set of cemented lenses;
[0052] And it satisfies the following relationship:
[0053] 1.3<|f1 / f|<2.4; 1.1<|f2 / f|<2.2; 0.8<|f3 / f|<1.7; 13.6<|f4 / f|<14.6;
[0054] Where f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, and f is the effective focal length of the entire optical system.
[0055] As an improvement, the Abbe constant Vd1 of the first lens is greater than 60 and less than 72, and the Abbe constants Vd2, Vd3, and Vd4 of the second, third, and fourth lenses are all greater than 35 and less than 47.
[0056] As an improvement, the refractive indices of each lens in the optical system satisfy the following condition:
[0057] 1.55<Nd1<1.68; 1.86<Nd2<1.97; 1.53<Nd3<1.65; 1.58<Nd4<1.69;
[0058] Wherein, Nd1 is the refractive index of the first lens, Nd2 is the refractive index of the second lens, Nd3 is the refractive index of the third lens, and Nd4 is the refractive index of the fourth lens.
[0059] As an improvement, the maximum target surface IH of the optical system satisfies the following condition:
[0060] IH≥7.41mm.
[0061] As an improvement, the aperture of the optical system satisfies the following condition:
[0062] F / NO=2.0.
[0063] As an improvement, the total length TTL of the optical system and the effective focal length f of the optical system satisfy the following condition:
[0064] 4.5≤TTL / f≤5.2.
[0065] As an improvement, the first lens is concave-convex, with the object side being convex and the image side being concave, and its optical power is negative.
[0066] The second lens is biconvex, with a convex surface on the object side and a convex surface with a plateau on the image side, and its optical power is positive.
[0067] The third lens is biconvex, with a small convex surface on the object side and a large convex surface on the image side, and its optical power is positive.
[0068] The fourth lens is concave-convex, with the object side being concave and the image side being convex, and its optical power is negative.
[0069] As an improvement, the aperture ST0 is positioned between the first lens E1 and the second lens E2.
[0070] In this patent embodiment, when the working distance is 0.6m, the total focal length of the optical system (optical lens) is f=3.75mm, the aperture F / NO=2.0, and the maximum target surface IH=7.41mm.
[0071] This specific embodiment is merely an explanation of the present utility model and is not intended to limit the present utility model. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but as long as they are within the scope of the claims of the present utility model, they are protected by patent law.
[0072] The parameters of each lens in this embodiment are listed in Table 1 below, and the aspherical coefficients of the lenses are shown in Table 2 below.
[0073] Table 1 Physical parameters of each lens
[0074]
[0075] Table 2 Aspherical coefficients of lenses
[0076]
[0077] The aspherical coefficients satisfy the following equation:
[0078]
[0079] Where z is the aspherical sagitta, c is the paraxial curvature of the aspherical surface, the curvature is the reciprocal of the radius of curvature, y is the lens aperture, k is the conic coefficient, a4 is the 4th order aspherical coefficient, a6 is the 6th order aspherical coefficient, a8 is the 8th order aspherical coefficient, and a10 is the 10th order aspherical coefficient.
[0080] Specifically, in this embodiment, the R-value (radius of curvature), thickness, refractive index, Abbe number (ABB), and focal length (EFL-E) of each lens surface are shown in Table 1, and the aspherical parameters are shown in Table 2. In Table 1, Surf represents the mirror surface number, and INFINITY represents infinity. In Table 2, R1 represents the radius of curvature of the corresponding lens surface facing the object side, and R2 represents the radius of curvature of the corresponding lens surface facing the image side. A positive radius of curvature indicates that the mirror is curved towards the object side, and a negative radius of curvature indicates that the mirror is curved towards the image side. Mirror surface numbers 1 and 2 represent the two mirror surfaces of the first lens E1 along the direction of light incidence, respectively; mirror surface numbers 4 and 5 represent the two mirror surfaces of the second lens E2 along the direction of light incidence, respectively; mirror surface number 6 represents the object-facing mirror surface of the third lens E3; mirror surface number 7 represents the cemented surface of the third lens E3 and the fourth lens E4; and mirror surface number 8 represents the image-facing mirror surface of the fourth lens E4.
[0081] In this embodiment of the utility model, Figure 2 The modulation transfer function (MTF) curve, representing the visible light band, indicates the overall resolving power of an optical system. The horizontal axis represents spatial frequency (lp / mm), and the vertical axis represents the MTF value. The MTF value is used to evaluate the image quality of a lens, ranging from 0 to 1. It is worth noting that the optical transfer function is a relatively accurate, intuitive, and common way to evaluate the image quality of an optical system; a higher and smoother curve indicates better image quality and a stronger ability to reproduce the true image. Figure 2 It can be seen that in the visible light band, at a spatial frequency of 83 lp / mm, the MTF in the imaging region near the center is >0.7, indicating good imaging quality. Figure 3 This is represented as a defocus curve at 20°C in the visible light band. Figure 3 It can be seen that the lens has good MTF concentration, making focusing easy, and the defocus curve trend is consistent across different field of view angles. From Figure 4 and Figure 5 It can be seen that the defocus curves at low temperature -40℃ and high temperature 95℃ both meet the requirements of high resolution, with small focus changes and stable thermal drift effect; Figure 6 Represented as a field curve diagram, by Figure 6 It can be seen that the field curvature value should be controlled between -0.12mm and 0.12mm. The smaller the field curvature value, the better the image quality of the lens. Figure 7 To represent it as an F-THETA distortion map, the smaller the F-THETA distortion, the less the compression at the edges of the image. Figure 8 It is represented as a standard point array diagram.
Claims
1. An optical imaging lens for automotive safety driving DMS, characterized in that: Along the optical axis from the object plane to the image plane, it includes, in sequence: first lens, aperture stop, second lens, third lens, fourth lens, filter, protective glass, and image plane; The first lens has a convex surface on the object side and a concave surface on the image side; The second lens has a convex surface on both the object plane and the image plane sides; The third lens has a convex surface on both the object plane and the image plane sides; The fourth lens has a concave surface on the object side and a convex surface on the image side; The third and fourth lenses form a set of cemented lenses; And it satisfies the following relationship: 1.3<|f1 / f|<2.4; 1.1<|f2 / f|<2.2; 0.8<|f3 / f|<1.7; 13.6<|f4 / f|<14.6; Where f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, and f is the effective focal length of the entire optical system.
2. The automotive safety driving DMS optical imaging lens according to claim 1, characterized in that: The Abbe constant Vd1 of the first lens is greater than 60 and less than 72, while the Abbe constants Vd2, Vd3, and Vd4 of the second, third, and fourth lenses are all greater than 35 and less than 47.
3. The automotive safety driving DMS optical imaging lens according to claim 1, characterized in that: The refractive indices of all lenses in the optical system satisfy the following condition: 1.55<Nd1<1.68; 1.86<Nd2<1.97; 1.53<Nd3<1.65; 1.58<Nd4<1.69; Wherein, Nd1 is the refractive index of the first lens, Nd2 is the refractive index of the second lens, Nd3 is the refractive index of the third lens, and Nd4 is the refractive index of the fourth lens.
4. The automotive safety driving DMS optical imaging lens according to claim 1, characterized in that: The maximum image height IH of the optical system satisfies the following condition: IH≥7.41mm.
5. The automotive safety driving DMS optical imaging lens according to claim 1, characterized in that: The aperture of the optical system satisfies the following condition: F / NO = 2.
0.
6. The automotive safety driving DMS optical imaging lens according to claim 1, characterized in that: The total length (TTL) of the optical system and the effective focal length (f) of the optical system satisfy the following condition: 4.5≤TTL / f≤5.
2.
7. The automotive safety driving DMS optical imaging lens according to claim 1, characterized in that: The first lens is concave-convex, with the object side being convex and the image side being concave, and its optical power is negative. The second lens is biconvex, with a convex surface on the object side and a convex surface with a plateau on the image side, and its optical power is positive. The third lens is biconvex, with a small convex surface on the object side and a large convex surface on the image side, and its optical power is positive. The fourth lens is concave-convex, with the object side being concave and the image side being convex, and its optical power is negative.
8. The automotive safety driving DMS optical imaging lens according to claim 1, characterized in that: The aperture is positioned between the first lens and the second lens.