Small optical system and working method thereof

Abstract

The invention relates to a small optical system and a working method thereof. The optical system is composed of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens which are sequentially arranged in the light incidence direction. According to the invention, the focal power and the surface type of each lens, the central thickness of each lens, the axial distance between the lenses and the like are reasonably distributed, the imaging performance requirement of the lens is met, the total length of the lens and the radial size of each lens are reduced, and the miniaturization of the lens group is realized.

Description

Technical Field

[0001] This invention relates to a small optical system and its operating method. Background Technology

[0002] With the rapid popularization of autonomous driving technology and Advanced Driver Assistance Systems (ADAS), forward-facing automotive cameras, as core optical components for perceiving the environment, play a crucial role in realizing functions such as lane keeping, obstacle detection, and adaptive cruise control (ACC). The high-definition imaging capability of forward-facing cameras directly affects the decision-making accuracy of ADAS systems. The operating environment of forward-facing cameras is complex and variable, requiring them to cope with extreme weather, wide temperature ranges, strong light variations, road vibrations, and gravel impacts. These conditions demand that lenses possess excellent resistance to thermal deformation, anti-glare performance, high light transmittance, and mechanical stability. Furthermore, modern automotive design emphasizes modularity and lightweighting, requiring lenses to be miniaturized and low-power to fit into the compact installation space at the front of the vehicle and reduce overall vehicle energy consumption. Existing forward-facing camera technology has several shortcomings. While all-glass lens designs perform stably in high-temperature and strong-light environments, the large number of lenses leads to high cost, weight, and complex assembly, hindering mass production and vehicle lightweighting. These limitations make it difficult for existing lenses to simultaneously meet the requirements of high performance, low cost, and automotive-grade durability. Summary of the Invention

[0003] In view of the shortcomings of the prior art, the present invention provides a small optical system that achieves clear imaging while having a small size and strong environmental adaptability.

[0004] The solution adopted by the present invention to solve the technical problem is: a small optical system: the optical system consists of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens arranged sequentially along the incident direction of light, wherein the fifth lens and the sixth lens are cemented together to form a cemented lens group, and an aperture stop is provided between the fourth lens and the fifth lens.

[0005] Furthermore, the first lens is a meniscus negative lens with a convex object-side surface and a concave image-side surface; the second lens is a biconcave negative lens with a concave object-side surface and a concave image-side surface; the third lens is a biconvex positive lens with a convex object-side surface and a convex image-side surface; the fourth lens is a biconvex positive lens with a convex object-side surface and a convex image-side surface; the fifth lens is a biconvex positive lens with a convex object-side surface and a convex image-side surface; the sixth lens is a meniscus negative lens with a concave object-side surface and a convex image-side surface; and the seventh lens is a meniscus positive lens with a convex object-side surface and a concave image-side surface.

[0006] Furthermore, the first, third, fourth, fifth, and sixth lenses are glass spherical lenses, while the second and seventh lenses are plastic aspherical lenses.

[0007] Furthermore, the air gap between the first lens and the second lens is 4.0~4.5mm; the air gap between the second lens and the third lens is 0.1~0.5mm; the air gap between the third lens and the fourth lens is 0.1~0.5mm; the air gap between the fourth lens and the aperture stop is 0~0.5mm; the air gap between the aperture stop and the fifth lens is 1.0~1.5mm; and the air gap between the sixth lens and the seventh lens is 1.0~1.5mm.

[0008] Furthermore, the first lens satisfies the following relationships: 1.7≤Nd≤2.0, Vd≤50; the second lens satisfies the following relationship: 1.3≤Nd≤1.6, Vd≥50; the third lens satisfies the following relationship: 2.0≤Nd≤2.3, Vd≤50; the fourth lens satisfies the following relationship: 1.7≤Nd≤2.0, Vd≥50; the fifth lens satisfies the following relationship: 1.3≤Nd≤1.6, Vd≥50; the sixth lens satisfies the following relationship: 1.7≤Nd≤2.0, Vd≤50; and the seventh lens satisfies the following relationship: 1.7≤Nd≤2.0, Vd≤50; where Nd is the refractive index and Vd is the Abbe constant.

[0009] Furthermore, the focal length of the optical system is f, and the focal lengths of the first lens, second lens, third lens, fourth lens, fifth lens, sixth lens, and seventh lens are f1, f2, f3, f4, f5, f6, and f7, respectively, wherein f1, f2, f3, f4, f5, f6, and f7 satisfy the following ratio with f: -2.0 <f1 / f<-1.0,-3.0<f2 / f<-2.0,3.0<f3 / f<4.0,2.0<f4 / f<3.0,1.0<f5 / f<2.0,-2.0<f6 / f<-1.0,6.0<f7 / f<7.0。

[0010] Furthermore, the equations for the aspherical lens curves of the second and seventh lenses are as follows: Where z is the distance from the vertex of the aspherical surface to the optical axis at a height of h; c is the paraxial curvature of the aspherical surface; r = 1 / c; k is the conic constant; and a1, a2, a3, a4, a5, a6, a7, and a8 are all higher-order coefficients.

[0011] 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 ≤ 7.6.

[0012] Furthermore, the image height H of the optical lens and the focal length f of the optical lens satisfy the following condition: H / f≥1.1.

[0013] A working method of a small optical system: When light is incident, the light path sequentially enters the first lens, the second lens, the third lens, the fourth lens, the aperture, the fifth lens, the sixth lens, and the seventh lens, and finally forms an image on the image plane.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. The lens employs seven optical elements, consisting of five glass spherical lenses 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 lens's total length is less than 31 mm and its outer diameter is less than 14 mm, ensuring the optical performance of the camera assembly while reducing the overall size of the lens and improving aesthetics. The second and seventh lenses are plastic aspherical lenses, which can balance aberrations across different fields of view, further enhancing the overall image quality of the lens.

[0015] 2. This lens has an imaging angle of more than 140 degrees and also has the advantages of high imaging clarity, large light aperture, and low tolerance sensitivity, which can more comprehensively monitor the scene outside the vehicle. 3. By rationally matching the various optical lenses, the system structure is compact and reasonable, easy to assemble, has low tolerance sensitivity, and is more suitable for large-scale high-yield production; 4. The use of five glass lenses combined with two plastic lenses reduces costs while adapting to different environments; 5. The chromatic aberration along each axis, the transverse chromatic aberration, and higher-order chromatic aberrations have been corrected to ensure that the imaging system can maintain high imaging quality even at large angles. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the optical structure of the present invention; Figure 2 This is the axial chromatic aberration diagram of the entire working band of the present invention; Figure 3 This is the transverse chromatic aberration diagram of the entire working band of the present invention; Figure 4 This is the field curvature distortion diagram of the entire working band of the present invention.

[0017] In the diagram: STO - aperture stop; L1 - first lens; L2 - second lens; L3 - third lens; L4 - fourth lens; L5 - fifth lens; L6 - sixth lens; L7 - seventh lens; IR - filter; CG - sensor protective glass; IMA - imaging plane. Detailed Implementation

[0018] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0019] like Figure 1 As shown, a small optical system is provided: the optical system consists of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens arranged sequentially along the incident direction of light. The fifth lens and the sixth lens are cemented together to form a cemented lens group, and an aperture stop is provided between the fourth lens and the fifth lens.

[0020] In this embodiment, without considering the curvature caused by the aspherical coefficient, the first lens is a meniscus negative lens with a convex object side and a concave image side; the second lens is a biconcave negative lens with a concave object side and a concave image side; the third lens is a biconvex positive lens with a convex object side and a convex image side; the fourth lens is a biconvex positive lens with a convex object side and a convex image side; the fifth lens is a biconvex positive lens with a convex object side and a convex image side; the sixth lens is a meniscus negative lens with a concave object side and a convex image side; and the seventh lens is a meniscus positive lens with a convex object side and a concave image side.

[0021] In this embodiment, the first lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are glass spherical lenses, and the second lens and the seventh lens are plastic aspherical lenses.

[0022] In this embodiment, the second lens is an aspherical lens with negative optical power. While adjusting large-angle light, its aspherical shape corrects spherical aberration and distortion of the optical system. The fifth and sixth lenses form an achromatic cemented doublet, controlling chromatic aberration within a reasonable range in the visible light band. The seventh lens is an aspherical lens with positive optical power, adjusting the light from each field of view to strike the sensor at a reasonable angle, correcting higher-order aberrations, and improving edge image quality. This reasonable lens combination enables the optical system to achieve a small size, large field of view, and large aperture, while effectively correcting on-axis and off-axis aberrations, resulting in good image quality. Figures 2 to 4 As shown.

[0023] In this embodiment, the air gap between the first lens and the second lens is 4.0~4.5mm; the air gap between the second lens and the third lens is 0.1~0.5mm; the air gap between the third lens and the fourth lens is 0.1~0.5mm; the air gap between the fourth lens and the aperture stop is 0~0.5mm; the air gap between the aperture stop and the fifth lens is 1.0~1.5mm; and the air gap between the sixth lens and the seventh lens is 1.0~1.5mm.

[0024] In this embodiment, the first lens satisfies the following relationship: 1.7≤Nd≤2.0, Vd≤50; the second lens satisfies the following relationship: 1.3≤Nd≤1.6, Vd≥50; the third lens satisfies the following relationship: 2.0≤Nd≤2.3, Vd≤50; the fourth lens satisfies the following relationship: 1.7≤Nd≤2.0, Vd≥50; the fifth lens satisfies the following relationship: 1.3≤Nd≤1.6, Vd≥50; the sixth lens satisfies the following relationship: 1.7≤Nd≤2.0, Vd≤50; and the seventh lens satisfies the following relationship: 1.7≤Nd≤2.0, Vd≤50; where Nd is the refractive index and Vd is the Abbe constant.

[0025] In this embodiment, the focal length of the optical system is f, and the focal lengths of the first lens, second lens, third lens, fourth lens, fifth lens, sixth lens, and seventh lens are f1, f2, f3, f4, f5, f6, and f7, respectively, wherein f1, f2, f3, f4, f5, f6, and f7 satisfy the following ratio with f: -2.0 <f1 / f<-1.0,-3.0<f2 / f<-2.0,3.0<f3 / f<4.0,2.0<f4 / f<3.0,1.0<f5 / f<2.0,-2.0<f6 / f<-1.0,6.0<f7 / f<7.0。

[0026] In this embodiment, the equations for the aspherical lens curves of the second and seventh lenses are as follows: Where z is the distance from the vertex of the aspherical surface to the optical axis at a height of h; c is the paraxial curvature of the aspherical surface; r = 1 / c; k is the conic constant; and a1, a2, a3, a4, a5, a6, a7, and a8 are all coefficients of higher-order terms.

[0027] 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 ≤ 7.6.

[0028] In this embodiment, the image height H of the optical lens and the focal length f of the optical lens satisfy the following condition: H / f≥1.1.

[0029] In this embodiment, the F-number of the optical system is ≤1.8.

[0030] In this embodiment, a filter is provided on the rear side of the seventh lens.

[0031] A working method of a small optical system: When light is incident, the light path sequentially enters the first lens, the second lens, the third lens, the fourth lens, the aperture, the fifth lens, the sixth lens, and the seventh lens, and finally forms an image on the image plane.

[0032] The technical specifications achieved by the optical system in this embodiment are as follows: (1) Focal length: 3.8≤EFFL≤4.2mm; (2) Aperture F≤1.7; (3) Field of view: 2w ≥ 140°; (4) Operating band: Visible light band.

[0033] To achieve the above design parameters, the specific design of the optical system adopted in this embodiment is shown in the table below: The aspherical coefficients of the aspherical lenses in the optical system of this embodiment are shown in the table below: The optical system in this embodiment achieves miniaturization of the lens assembly and reduces costs by rationally allocating the optical power, surface shape, center thickness of each lens, and on-axis distance between each lens, while meeting the lens imaging performance requirements.

[0034] Unless otherwise stated, if any of the technical solutions disclosed in this invention specify a numerical range, then the disclosed numerical range is a preferred numerical range. Anyone skilled in the art should understand that the preferred numerical range is merely one among many feasible numerical values ​​that has a more obvious or representative technical effect. Because there are many numerical values, it is impossible to list them all. Therefore, this invention discloses only some numerical values ​​to illustrate the technical solutions of this invention. Furthermore, the numerical values ​​listed above should not constitute a limitation on the scope of protection of this invention.

[0035] If the terms "first" or "second" are used in this document to specify components, those skilled in the art should know that the use of "first" or "second" is merely for the purpose of distinguishing components in description, and unless otherwise stated, the above terms have no special meaning.

[0036] If this invention discloses or relates to mutually fixedly connected components or structural parts, 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, mutually fixed connections can also be replaced by an integral structure (e.g., manufactured in one piece using a casting process) (except where it is obviously impossible to use an integral molding process).

[0037] Furthermore, the orientations or positional relationships used in any of the technical solutions disclosed in this invention above to indicate positional relationships, such as "longitudinal," "lateral," "up," "down," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing this patent. They are not intended to 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 patent. In addition, unless otherwise stated, the terms used to indicate shape in any of the technical solutions disclosed in this invention above include shapes that are similar to, close to, or approximate with it.

[0038] 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.

[0039] 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 miniature optical system, characterized in that: The optical system consists of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens arranged sequentially along the incident direction of light. The fifth lens and the sixth lens are cemented together to form a cemented lens group, and an aperture stop is provided between the fourth lens and the fifth lens.

2. The miniature optical system according to claim 1, characterized in that: The first lens is a meniscus negative lens with a convex object-side surface and a concave image-side surface; the second lens is a biconcave negative lens with a concave object-side surface and a concave image-side surface; the third lens is a biconvex positive lens with a convex object-side surface and a convex image-side surface; the fourth lens is a biconvex positive lens with a convex object-side surface and a convex image-side surface; the fifth lens is a biconvex positive lens with a convex object-side surface and a convex image-side surface; the sixth lens is a meniscus negative lens with a concave object-side surface and a convex image-side surface; and the seventh lens is a meniscus positive lens with a convex object-side surface and a concave image-side surface.

3. The miniature optical system according to claim 1, characterized in that: The first, third, fourth, fifth, and sixth lenses are glass spherical lenses, while the second and seventh lenses are plastic aspherical lenses.

4. The miniature optical system according to claim 1, characterized in that: The air gap between the first lens and the second lens is 4.0~4.5mm; the air gap between the second lens and the third lens is 0.1~0.5mm; the air gap between the third lens and the fourth lens is 0.1~0.5mm; the air gap between the fourth lens and the aperture stop is 0~0.5mm; the air gap between the aperture stop and the fifth lens is 1.0~1.5mm; and the air gap between the sixth lens and the seventh lens is 1.0~1.5mm.

5. The miniature optical system according to claim 1, characterized in that: The first lens satisfies the following relationship: 1.7≤Nd≤2.0, Vd≤50; the second lens satisfies the following relationship: 1.3≤Nd≤1.6, Vd≥50; the third lens satisfies the following relationship: 2.0≤Nd≤2.3, Vd≤50; the fourth lens satisfies the following relationship: 1.7≤Nd≤2.0, Vd≥50; the fifth lens satisfies the following relationship: 1.3≤Nd≤1.6, Vd≥50; the sixth lens satisfies the following relationship: 1.7≤Nd≤2.0, Vd≤50; and the seventh lens satisfies the following relationship: 1.7≤Nd≤2.0, Vd≤50; where Nd is the refractive index and Vd is the Abbe constant.

6. The miniature optical system according to claim 1, characterized in that: The focal length of the optical system is f, and the focal lengths of the first lens, second lens, third lens, fourth lens, fifth lens, sixth lens, and seventh lens are f1, f2, f3, f4, f5, f6, and f7, respectively. The ratios of f1, f2, f3, f4, f5, f6, and f7 to f satisfy the following ratio: -2.0 <f1 / f<-1.0,-3.0<f2 / f<-2.0,3.0<f3 / f<4.0,2.0<f4 / f<3.0,1.0<f5 / f<2.0,-2.0<f6 / f<-1.0,6.0<f7 / f<7.0。 7. The miniature optical system according to claim 3, characterized in that: The equations for the aspherical lens curves of the second and seventh lenses are as follows: Where z is the distance from the vertex of the aspherical surface to the optical axis at a height of h; c is the paraxial curvature of the aspherical surface; r = 1 / c; k is the conic constant; and a1, a2, a3, a4, a5, a6, a7, and a8 are all higher-order coefficients.

8. The miniature optical system according to claim 1, characterized in that: The total optical length (TTL) of the optical system and the focal length (f) of the optical system satisfy the following condition: TTL / f ≤ 7.

6.

9. The miniature optical system 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 condition: H / f≥1.

1.

10. A method for operating a small optical system, employing the small optical system as described in any one of claims 1-9, characterized in that: When light is incident, the light path sequentially enters the first lens, the second lens, the third lens, the fourth lens, the aperture, the fifth lens, the sixth lens, and the seventh lens, and finally forms an image on the image plane.

Images