An ultra-compact low-cost automotive cabin wide-angle monitoring optical system

Abstract

The present application relates to a kind of ultra-small low-cost car cabin wide-angle monitoring optical systems, the system includes six pieces of lens, diaphragm, filter, protective glass and image surface, wherein lens is made of 2G+4P structure, reduce production cost, improve product performance ratio, while using low dispersion lens material, optimize purple edge effect, also have thermal compensation effect, working temperature can be from-40 DEG C to 105 DEG C, adapt to complex temperature scene.The system can meet the requirement of 5 million pixel back-illuminated chip OX05B1S, can simultaneously consider visible light and near infrared light, realize day and night high-definition monitoring, and field of view angle can reach 160 degrees, the range that can be shot is larger.The total length of the system is 12mm, the minimum front end diameter is 8.5mm, realize the demand of cabin miniaturization, horizontal angle can reach 140 degrees, can simultaneously compatible driver fatigue driving monitoring and rear passenger monitoring, cover traditional DMS and in-vehicle monitoring application, save the manufacturing cost of automobile camera.

Description

Technical Field

[0001] The present invention relates to the technical field of optical systems, and particularly to an ultra-small and low-cost wide-angle monitoring optical system for the interior of an automobile cabin. Background Art

[0002] In recent years, with the continuous improvement of the scientific and technological level and the increasing attention paid to automobile safety, various auxiliary driving systems have emerged. Among them, the market demand for the in-vehicle occupant monitoring system (OMS) supporting intelligent driving has been increasing day by day. It mainly tracks the status of the rear passengers in the car to ensure the safety of passengers. The OMS system is generally installed in the area between above the inner rearview mirror and below the dome light, and can realize functions such as real-time monitoring of the vehicle occupants and detection of children left in the vehicle.

[0003] As the image acquisition component of the OMS system, the requirements for the monitoring optical system have also been continuously improved. In the existing OMS monitoring optical systems, there are generally problems such as a relatively small field of view, a relatively large volume, a relatively high cost, poor high and low temperature drift stability, poor day and night confocal effect, and relatively serious purple fringing at the edges. Summary of the Invention

[0004] The present invention is an ultra-small and low-cost wide-angle monitoring optical system for the interior of an automobile cabin, aiming to better solve the problems mentioned in the background art.

[0005] The above technical object of the present invention is achieved through the following technical solutions: An ultra-small and low-cost wide-angle monitoring optical system for the interior of an automobile cabin includes a first lens, a second lens, a third lens, an aperture stop, a fourth lens, a fifth lens, a sixth lens, a filter, a protective glass, and an image plane arranged in sequence from the object side to the image side. The six lenses are composed of a 2G+4P structure (that is, composed of two glass lenses and four plastic lenses), which is different from other all-glass structures or glass+glass aspherical structures, reducing the production cost and greatly improving the product cost performance. In addition, the lenses adopt low-dispersion lens materials, optimizing the purple fringing effect at the edges of the object, better restoring the real scene, and at the same time enabling the entire optical system to have a thermal compensation effect, with the working temperature ranging from -40°C to 105°C, greatly enhancing the adaptability of the product to complex temperature scenarios.

[0006] The first lens is a meniscus lens with a negative optical power, the second lens is a meniscus lens with a negative optical power, the third lens is a meniscus lens with a positive optical power, the fourth lens is a biconvex lens with a positive optical power, the fifth lens is a biconcave lens with a negative optical power, and the sixth lens is a biconvex lens with a positive optical power;

[0007] The ratio of the focal length of the first to sixth lenses to the focal length of the lens satisfies the following set relationship: 0.8 < |f1 / f| < 1.5, 4.7 < |f2 / f| < 5.6, 2.4 < |f3 / f| < 3.3, 1.2 < |f4 / f| < 1.8, 0.9 < |f5 / f| < 1.6, 1.0 < |f6 / f| < 1.9;

[0008] Where f1 represents the effective focal length of the first lens, f2 represents the effective focal length of the second lens, f3 represents the effective focal length of the third lens, f4 represents the effective focal length of the fourth lens, f5 represents the effective focal length of the fifth lens, f6 represents the effective focal length of the sixth lens, and f represents the effective focal length of the optical system.

[0009] The optical system can meet the requirements of the 5-megapixel back-illuminated chip OX05B1S, and can simultaneously handle 400-700nm visible light and 940nm near-infrared light, with an infrared defocus of 4um, enabling high-definition monitoring during both day and night.

[0010] In some embodiments, the refractive indices of the second lens and the sixth lens are both greater than 1.35 and less than 1.65, and the Abbe numbers are both greater than 40 and less than 65.

[0011] The refractive indices of the third and fifth lenses are both greater than 1.40 and less than 1.75, and the Abbe coefficients are both greater than 10 and less than 35.

[0012] In some embodiments, the optical system satisfies the following condition:

[0013] TTL / h < 1.92;

[0014] Where: TTL represents the total length of the optical system, and h represents the maximum image circle of the optical system.

[0015] In some embodiments, the total optical length (TTL) of the optical system satisfies the following condition:

[0016] The TTL is 11mm≤TTL≤13mm, with TTL preferably being 12mm, and the front diameter of the optical system (i.e., the effective diameter of the first optical element of the optical system) is at least 8.5mm, perfectly meeting the requirement of miniaturization within the cabin.

[0017] In some embodiments, the field of view of the optical system is 2W ≥ 160°, allowing for a wider shooting range.

[0018] In some embodiments, the optical back focal length BFL of the optical system and the effective focal length f satisfy the condition: BFL / f > 1.86.

[0019] In some embodiments, the optical system satisfies the following condition:

[0020] 0.1<(h / 2) / (f×tan(FOV / 2))<0.5;

[0021] Where: f represents the effective focal length of the optical system, FOV represents the maximum field of view of the optical system, and h represents the maximum image circle of the optical system.

[0022] The horizontal angle of the optical system (i.e., the horizontal angle of the effective imaging area on the imaging plane of the optical system) can reach 140 degrees, thus simultaneously enabling monitoring of driver fatigue and rear-seat passengers. Functionally, it covers both traditional DMS (Driver Monitoring System) lens applications and in-vehicle monitoring applications, achieving the application of two optical systems with a single system, thereby saving on the manufacturing cost of automotive cameras.

[0023] In some embodiments, the first lens has a convex surface facing the object side and a concave surface facing the image side; the second lens has a concave surface facing the object side and a slightly convex surface facing the image side; the third lens has a concave surface facing the object side and a convex surface facing the image side; the fourth lens has a slightly convex surface facing the object side and a large convex surface facing the image side; the fifth lens has a slightly concave surface facing the object side and a large concave surface facing the image side; and the sixth lens has a slightly convex surface facing the object side and a large convex surface facing the image side.

[0024] In summary, the present invention has the following beneficial effects:

[0025] This invention provides an ultra-miniaturized, low-cost wide-angle monitoring optical system for automotive cabins. By rationally utilizing lenses with specific shapes and structures and limiting the optical power of each lens, it achieves excellent image quality, meeting the requirements of a 5-megapixel back-illuminated chip OX05B1S. It also accommodates 400-700nm visible light and 940nm near-infrared light, with an infrared defocus of 4µm, achieving high-definition monitoring requirements both day and night. Furthermore, it boasts a 160-degree field of view, allowing for a wider shooting range. Its 2G+4P structure distinguishes it from other all-glass or glass-based systems. The aspherical glass structure reduces production costs and significantly improves product cost-effectiveness. The use of low-dispersion lens materials optimizes the purple fringing effect at object edges, better reproducing realistic scenes. Simultaneously, the entire optical system has thermal compensation, allowing for an operating temperature range of -40℃ to 105℃, greatly enhancing the product's adaptability to complex temperature environments. The optical system has a total length of 12mm and a minimum front-end diameter of 8.5mm, perfectly meeting the miniaturization requirements for in-cabin applications. The horizontal angle reaches 140 degrees, simultaneously supporting driver fatigue monitoring and rear passenger monitoring. Functionally, it covers both traditional DMS (Driver Monitoring System) lens applications and in-vehicle monitoring applications, achieving the application of two optical systems in one, saving on automotive camera manufacturing costs. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of a lens according to an embodiment of the present invention;

[0027] Figure 2 This is an analytical plot of 125 lp / mm MTF at 20°C according to an embodiment of the present invention;

[0028] Figure 3 This is a defocusing curve at 20°C with a focal length of 125 lp / mm, according to an embodiment of the present invention.

[0029] Figure 4 This is a defocusing curve at 85°C and 125 lp / mm, according to an embodiment of the present invention.

[0030] Figure 5 This is a defocusing curve at -40℃ with 125 lp / mm, according to an embodiment of the present invention.

[0031] Figure 6 This is a field curvature diagram of an embodiment of the present invention;

[0032] Figure 7 This is an F-THETA distortion diagram from an embodiment of the present invention;

[0033] Figure 8 This is a defocus curve of 125 lp / mm at 940 nm near-infrared light according to an embodiment of the present invention;

[0034] Figure 9 This is an imaging point array diagram of an embodiment of the present invention.

[0035] In the diagram: E1: First lens; E2: Second lens; E3: Third lens; STO (Stop): Aperture stop; E4: Fourth lens; E5: Fifth lens; E6: Sixth lens; IR (Infrared Filter): Filter; CG (Cover Glass): Cover glass; IMA (Image Surface): Image plane;

[0036] S1: The object-side side of the first lens; S2: The image-side side of the first lens; S3: The object-side side of the second lens; S4: The image-side side of the second lens; S5: The object-side side of the third lens; S6: The image-side side of the third lens; S8: The object-side side of the fourth lens; S9: The image-side side of the fourth lens; S10: The object-side side of the fifth lens; S11: The image-side side of the fifth lens; S12: The object-side side of the sixth lens; S13: The image-side side of the sixth lens. Detailed Implementation

[0037] Embodiments of the present invention are described in detail below, examples of which are illustrated 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 the present invention, and should not be construed as limiting the present invention.

[0038] In the description of this invention, 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 invention 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 invention.

[0039] 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 invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0040] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," 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 invention according to the specific circumstances.

[0041] In this embodiment, the parameters of the lens group are listed in Table 1:

[0042] Surf Radius Thickness Index ABB EFL-E OBJ 20000 3000 1 9.552446674 0.45 1.73 54.7 -2.861 2 1.758138058 1.497706842 3 -4.415403941 0.4 1.51 56.2 -12.692 4 -14.11081986 0.108089023 5 -9.590686392 0.783080482 1.66 20.4 7.433 6 -3.372448035 0.45 STO infinity 0.156729563 8 5.455874234 1.455510001 1.59 68.6 3.590 9 -3.165912947 0.1 10 -10.45728806 0.5 1.66 20.4 -3.354 11 2.9151175 0.127773212 12 3.069708864 1.318326685 1.54 56.0 3.658 13 -4.734542473 0.1 14 infinity 0.7 1.52 64.2 15 infinity 3.902784192 IMA infinity 0

[0043] Table 1

[0044] Aspherical coefficients are shown in Table 2:

[0045]

[0046]

[0047]

[0048] Table 2 shows the aspherical coefficients that satisfy the following equation:

[0049]

[0050] Where z is the aspherical sagitta, c is the paraxial curvature of the aspherical surface, 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.

[0051] Specifically, the R-values ​​and thicknesses of each lens surface in this embodiment are shown in Table 1, and the aspherical parameters are shown in Table 2.

[0052] The optical system provided in Table 1 has an effective focal length of 2.52 mm, a total length of 12 mm, and a field of view of 160 degrees (2w). In Table 1, mirror numbers 1 and 2 represent the two mirrors of the first lens along the direction of light incidence, mirror numbers 3 and 4 represent the two mirrors of the second lens along the direction of light incidence, mirror numbers 5 and 6 represent the two mirrors of the third lens along the direction of light incidence, mirror numbers 8 and 9 represent the two mirrors of the fourth lens along the direction of light incidence, mirror numbers 10 and 11 represent the two mirrors of the fifth lens along the direction of light incidence, and mirror numbers 12 and 13 represent the two mirrors of the sixth lens along the direction of light incidence.

[0053] This embodiment provides an ultra-miniaturized, low-cost wide-angle monitoring optical system for automotive cabins, the structural schematic of which is shown below. Figure 1 As shown, the optical system includes a first lens E1, a second lens E2, a third lens E3, an aperture stop STO, a fourth lens E4, a fifth lens E5, a sixth lens E6, an IR filter, a protective glass CG, and an image plane IMA arranged sequentially from the object side to the image side. The six lenses are composed of a 2G+4P structure, which consists of two glass lenses and four plastic lenses. This is different from other all-glass structures or glass + glass aspherical structures, which reduces production costs and greatly improves the product's cost-effectiveness. In addition, the lenses use low-dispersion lens materials, which optimizes the purple fringing effect at the edges of objects and better restores the true scene. At the same time, the entire optical system has a thermal compensation effect, and the operating temperature can range from -40℃ to 105℃, which greatly improves the product's adaptability to complex temperature scenarios.

[0054] Specifically, the first lens E1 is a meniscus lens with negative optical power, the second lens E2 is a meniscus lens with negative optical power, the third lens E3 is a meniscus lens with positive optical power, the fourth lens E4 is a biconvex lens with positive optical power, the fifth lens E5 is a biconcave lens with negative optical power, and the sixth lens E6 is a biconvex lens with positive optical power. The ratio of the focal length of the first lens E1 to the sixth lens E6 to the focal length of the lens satisfies the following set relationship: 0.8 < |f1 / f| < 1.5, 4.7 < |f2 / f| <5.6, 2.4<|f3 / f|<3.3, 1.2<|f4 / f|<1.8, 0.9<|f5 / f|<1.6, 1.0<|f6 / f|<1.9; where f1 represents the effective focal length of the first lens E1, f2 represents the effective focal length of the second lens E2, f3 represents the effective focal length of the third lens E3, f4 represents the effective focal length of the fourth lens E4, f5 represents the effective focal length of the fifth lens E5, f6 represents the effective focal length of the sixth lens E6, and f represents the effective focal length of the optical system. This optical system can meet the requirements of the 5-megapixel back-illuminated chip OX05B1S, and can simultaneously handle 400-700nm visible light and 940nm near-infrared light, with an infrared defocus of 4um, enabling high-definition monitoring requirements both day and night.

[0055] In this embodiment, the refractive index of the second lens E2 and the sixth lens E6 are both 1.5, and the Abbe number is 55; the refractive index of the third lens E3 and the fifth lens E5 are both 1.6, and the Abbe number is 25. This optical system satisfies the following condition: TTL / h < 1.92; where TTL represents the total length of the optical system, and h represents the maximum image circle of the optical system. The total optical length TTL of this optical system is 12 mm, and the minimum front diameter of the optical system (i.e., the effective diameter of the first optical element) is 8.5 mm, perfectly meeting the requirement of miniaturization within the cabin. The field of view of this optical system is 2W ≥ 160°, allowing for a wider shooting range. The optical back focal length BFL and the effective focal length f of this optical system satisfy the condition: BFL / f > 1.86. This optical system satisfies the following condition: 0.1 < (h / 2) / (f × tan(FOV / 2)) < 0.5; where f represents the effective focal length of the optical system, FOV represents the maximum field of view of the optical system, and h represents the maximum image circle of the optical system. The horizontal angle of this optical system (i.e., the horizontal angle of the effective imaging area on the imaging plane of the optical system) can reach 140 degrees, thus simultaneously enabling monitoring of driver fatigue and rear-seat passengers. Functionally, it covers both traditional DMS (Driver Monitoring System) lens applications and in-vehicle monitoring applications, achieving the application of two optical systems in one system, thereby saving on the manufacturing cost of automotive cameras.

[0056] In this embodiment, the first lens E1 has a convex surface S1 facing the object side and a concave surface S2 facing the image side; the second lens E2 has a concave surface S3 facing the object side and a slightly convex surface S4 facing the image side; the third lens E3 has a concave surface S5 facing the object side and a convex surface S6 facing the image side; the fourth lens E4 has a slightly convex surface S8 facing the object side and a large convex surface S9 facing the image side; the fifth lens E5 has a slightly concave surface S10 facing the object side and a large concave surface S11 facing the image side; and the sixth lens E6 has a slightly convex surface S12 facing the object side and a large convex surface S13 facing the image side.

[0057] In an embodiment of the present invention, Figure 2 This is a modulation transfer function (MTF) curve for the visible light band, representing the overall resolving power of an optical system. The horizontal axis represents spatial frequency, in cycles per millimeter (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. The higher and smoother the curve, the better the image quality and the stronger the ability to reproduce the true image. Figure 2It can be seen that in the visible light band, at a spatial frequency of 125 lp / mm, the MTF in the imaging region near the center is >0.6, indicating good imaging quality. Figure 3 The defocus curve shows that the lens has good MTF concentration, making focusing easy. From... Figure 4 and Figure 5 It can be seen that the defocus curves at both high and low temperatures meet the requirements of high resolution, with small changes in focus 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 -0.03mm and 0.03mm. The smaller the field curvature value, the better the image quality of the lens. Figure 7 This is represented as an F-THETA distortion map. The smaller the F-THETA distortion, the less the compression at the edges of the image. Figure 8 This is represented as a defocus curve at 940nm in near-infrared light. The smaller the defocus curve offset, the better the day-night confocal effect of the optical system.

[0058] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A miniaturized, low-cost wide-angle monitoring optical system for automotive cabins, characterized in that: It includes a first lens, a second lens, a third lens, an aperture stop, a fourth lens, a fifth lens, a sixth lens, a filter, a protective glass, and an image plane arranged sequentially from the object side to the image side; The monitoring optical system has 6 lenses; The first lens is a meniscus lens with negative optical power, the second lens is a meniscus lens with negative optical power, the third lens is a meniscus lens with positive optical power, the fourth lens is a biconvex lens with positive optical power, the fifth lens is a biconcave lens with negative optical power, and the sixth lens is a biconvex lens with positive optical power. The ratio of the focal length of the first to sixth lenses to the focal length of the monitoring optical system satisfies the following set relationship: 0.8 < |f1 / f| < 1.5, 4.7 < |f2 / f| < 5.6, 2.4 < |f3 / f| < 3.3, 1.2 < |f4 / f| < 1.8, 0.9 < |f5 / f| < 1.6, 1.0 < |f6 / f| < 1.9; Where f1 represents the effective focal length of the first lens, f2 represents the effective focal length of the second lens, f3 represents the effective focal length of the third lens, f4 represents the effective focal length of the fourth lens, f5 represents the effective focal length of the fifth lens, f6 represents the effective focal length of the sixth lens, and f represents the effective focal length of the monitoring optical system.

2. The ultra-miniaturized, low-cost automotive cabin wide-angle monitoring optical system according to claim 1, characterized in that: The refractive indices of the second and sixth lenses are both greater than 1.35 and less than 1.65, and the Abbe numbers are both greater than 40 and less than 65. The refractive indices of the third and fifth lenses are both greater than 1.40 and less than 1.75, and the Abbe coefficients are both greater than 10 and less than 35.

3. The ultra-miniaturized, low-cost automotive cabin wide-angle monitoring optical system according to claim 1, characterized in that: The monitoring optical system satisfies the following condition: TTL / h < 1.92; Where: TTL represents the total length of the optical system, and h represents the maximum image circle of the optical system.

4. The ultra-miniaturized, low-cost automotive cabin wide-angle monitoring optical system according to claim 3, characterized in that: The total optical length (TTL) of the optical system satisfies the following condition: 11mm≤TTL≤13mm.

5. The ultra-miniaturized, low-cost automotive cabin wide-angle monitoring optical system according to claim 1, characterized in that: The field of view of the optical system is 2W ≥ 160°.

6. The ultra-miniaturized, low-cost automotive cabin wide-angle monitoring optical system according to claim 1, characterized in that: The optical back focal length BFL and the effective focal length f of the optical system satisfy the condition: BFL / f > 1.

86.

7. The ultra-miniaturized, low-cost automotive cabin wide-angle monitoring optical system according to claim 1, characterized in that: The optical system satisfies the following condition: 0.1<(h / 2) / (f×tan(FOV / 2))<0.5; Where: f represents the effective focal length of the optical system, FOV represents the maximum field of view of the optical system, and h represents the maximum image circle of the optical system.

8. The ultra-miniaturized, low-cost automotive cabin wide-angle monitoring optical system according to claim 1, characterized in that: The first lens has a convex surface facing the object side and a concave surface facing the image side; the second lens has a concave surface facing the object side and a convex surface facing the image side; the third lens has a concave surface facing the object side and a convex surface facing the image side; the fourth lens has a convex surface facing the object side and a convex surface facing the image side; the fifth lens has a concave surface facing the object side and a concave surface facing the image side; and the sixth lens has a convex surface facing the object side and a convex surface facing the image side.

Images