Small imaging lens and imaging method thereof

Abstract

The invention relates to a small imaging lens and an imaging method thereof. The small imaging lens comprises an optical system, and the optical system is composed of a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens which are sequentially arranged from left to right along a light incident light path; the first lens is a negative meniscus lens, the second lens is a negative meniscus lens, the third lens is a biconvex positive lens, the fourth lens is a negative meniscus lens, the fifth lens is a plano-convex positive lens, and the sixth lens is a biconvex positive lens. By reasonably distributing 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, the total length of the lens and the radial size of each lens are reduced while the imaging performance and rear focus requirements of the lens are met, and the miniaturization of the lens group is realized.

Description

Technical Field

[0001] This invention relates to a small imaging lens and its imaging method. Background Technology

[0002] With the rapid development of autonomous driving technology and intelligent transportation systems, LiDAR (Light Detection and Ranging) has become a core component of high-precision environmental perception technology, finding widespread application in automobiles, robotics, and drones. The LiDAR receiver lens is a crucial optical element in a LiDAR system, responsible for collecting reflected laser signals and focusing them onto the detector. Its performance directly impacts the system's ranging accuracy, field of view coverage, and resistance to environmental interference. Industry data indicates that LiDAR systems need to achieve long-range, high-resolution, and wide-field-of-view detection to meet the demands of autonomous driving in complex road environments. LiDAR receiver lenses must withstand extreme outdoor conditions, including a wide temperature range, intense direct sunlight, rain, snow, fog, dust particles, and mechanical vibration and impact. These factors require lenses with high optical transmittance, excellent thermal stability, and mechanical durability, while maintaining low stray light and a high signal-to-noise ratio.

[0003] Furthermore, as LiDAR systems evolve towards miniaturization and integration, receiver lenses need to achieve compact designs to reduce size and weight, adapting to vehicle space constraints and lowering overall vehicle power consumption. Existing LiDAR receiver lenses primarily employ hybrid glass-plastic multi-element designs or simple single-lens structures, both of which have significant drawbacks. While hybrid designs can reduce cost and weight through plastic aspherical lenses, the high coefficient of thermal expansion of plastic materials makes them prone to deformation under high temperatures or prolonged UV exposure, leading to focal length drift, signal attenuation, or increased aberrations, failing to meet automotive-grade durability standards (such as AEC-Q100). Single-lens or low-element solutions simplify the structure, but their optical performance is limited, making it difficult to balance wide field of view with high resolution. Severe spherical aberration and distortion, especially at the edges of the field of view, result in low light collection efficiency and reduced detection accuracy. These shortcomings limit the application of LiDAR receiver lenses in high-performance autonomous driving systems, necessitating a novel optical design with an all-glass spherical lens structure. This design, through optimized combination of multiple spherical lenses, aims to achieve a balance between high optical performance, low cost, and environmental adaptability. Summary of the Invention

[0004] The present invention improves upon the above-mentioned problems. Specifically, the technical problem to be solved by the present invention is to provide a small imaging lens and its imaging method, which achieves clear imaging while having a small size and low manufacturing cost.

[0005] The present invention is configured as follows: it includes an optical system consisting of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens arranged sequentially from left to right along the incident light path; the first lens is a meniscus negative lens, the second lens is a meniscus negative lens, the third lens is a biconvex positive lens, the fourth lens is a meniscus negative lens, the fifth lens is a plano-convex positive lens, and the sixth lens is a biconvex positive lens.

[0006] 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 convex, and the image-side surface is concave; the object-side surface of the third lens is convex, and the image-side surface is convex; the object-side surface of the fourth lens is convex, and the image-side surface is concave; the object-side surface of the fifth lens is flat, and the image-side surface is convex; and the object-side surface of the sixth lens is convex, and the image-side surface is convex.

[0007] Furthermore, the air gap between the first lens and the second lens is 2.0~2.5mm; the air gap between the second lens and the third lens is 1.0~1.5mm; an aperture stop is provided between the third lens and the fourth lens, the air gap between the third lens and the aperture stop is -0.5~0.0mm; the air gap between the aperture stop and the fourth lens is 1.0~1.5mm; the air gap between the fourth lens and the fifth lens is 0.5~1.0mm; and the air gap between the fifth lens and the sixth lens is 0.1~0.5mm.

[0008] Furthermore, the focal length of the optical system is set as f, and the focal lengths of the first lens, second lens, third lens, fourth lens, fifth lens, and sixth lens are f1, f2, f3, f4, f5, and f6, respectively, wherein f1, f2, f3, f4, f5, and f6 satisfy the following ratio with f: -3.0 <f1 / f<-2.0,-5.0<f2 / f<-4.0,2.0<f3 / f<3.0,-6.0<f4 / f<-5.0,3.0<f5 / f<4.0,3.0<f6 / f<4.0。

[0009] Furthermore, the first lens satisfies the relationship: 2.0 ≤ N d ≤2.3, V d ≤50; the second lens satisfies the relationship: 1.3≤N d ≤1.6, V d ≥50; The third lens satisfies the relationship: 1.7≤N d ≤2.0, V d ≤50; The fourth lens satisfies the relationship: 1.7≤N d ≤2.0, V d ≤50; the fifth lens satisfies the relationship: 2.0≤Nd ≤2.3, V d ≤50; The sixth lens satisfies the relationship: 2.0≤N d ≤2.3, V d ≤50; where N d V is the refractive index. d Let be Abbe's constant.

[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 ≤ 9.7.

[0011] Furthermore, the image height H of the optical system and the focal length f of the optical system satisfy the following condition: H / f≥1.2.

[0012] Furthermore, the F-number of the optical system is ≤1.6.

[0013] Furthermore, a filter and an imaging surface are sequentially arranged behind the sixth lens.

[0014] Furthermore, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are all glass spherical lenses. Furthermore, in the imaging method of a small imaging lens, when light is incident, the light path passes through the first lens, the second lens, the third lens, the fourth lens, and the fifth lens in sequence to form an image.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) The lens uses six optical lenses, which form the imaging system. The glass spherical lenses are manufactured using mature technology, which reduces the manufacturing cost. By selecting appropriate glass materials and allocating the optical power of each lens, the thermal stability of the system under high and low temperature environments is achieved. The total length of the lens is less than 23 mm and the outer diameter is less than 12 mm, which ensures optical performance while reducing the overall size of the lens. (2) The lens has an imaging angle of more than 150 degrees. By reasonably matching positive and negative lenses, high image quality is achieved within the field of view. (3) By reasonably matching each optical lens, the system structure is compact and reasonable, easy to assemble, and has low tolerance sensitivity, making it more suitable for large-scale high-yield production. (4) The use of six glass lenses reduces costs while adapting to the environment. (5) Axial chromatic aberration, transverse chromatic aberration, and higher-order chromatic aberration are corrected to ensure that the imaging system has high imaging quality in each field of view. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the optical structure of an embodiment of the present invention; Figure 2 This is an axial chromatic aberration diagram of the entire working band of this invention embodiment; Figure 3This is a transverse 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 diagram: STO - aperture stop; L1 - first lens; L2 - second lens; L3 - third lens; L4 - fourth lens; L5 - fifth lens; L6 - sixth lens; IR - filter; IMA - imaging plane. Detailed Implementation

[0017] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0018] Example: Figures 1-4 As shown, an embodiment of the present invention provides a small imaging lens, including an optical system. The optical system consists of a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, and a sixth lens L6 arranged sequentially from left to right along the incident light path. The first lens is a meniscus negative lens, the second lens is a meniscus negative lens, the third lens is a biconvex positive lens, the fourth lens is a meniscus negative lens, the fifth lens is a plano-convex positive lens, and the sixth lens is a biconvex positive lens.

[0019] The first and second lenses are negative power meniscus lenses, which expand the field of view and improve field curvature. The fifth and sixth lenses are positive power plano-convex and biconvex lenses, which correct residual aberrations while controlling and adjusting the light rays from each field of view to strike the image plane at a reasonable angle. Figures 2-4 As shown, the reasonable lens combination enables the optical system to achieve small size, large aperture, and low CRA, while also providing good correction for on-axis and off-axis aberrations, resulting in good image quality.

[0020] In this embodiment of the invention, 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 convex and the image-side surface is concave; the object-side surface of the third lens is convex and the image-side surface is convex; the object-side surface of the fourth lens is convex and the image-side surface is concave; the object-side surface of the fifth lens is flat and the image-side surface is convex; and the object-side surface of the sixth lens is convex and the image-side surface is convex.

[0021] In this embodiment of the invention, the air gap between the first lens and the second lens is 2.0~2.5mm; the air gap between the second lens and the third lens is 1.0~1.5mm; an aperture stop STO is provided between the third lens and the fourth lens, the air gap between the third lens and the aperture stop is -0.5~0.0mm; the air gap between the aperture stop and the fourth lens is 1.0~1.5mm; the air gap between the fourth lens and the fifth lens is 0.5~1.0mm; and the air gap between the fifth lens and the sixth lens is 0.1~0.5mm.

[0022] In this embodiment of the invention, the focal length of the optical system is set as f, and the focal lengths of the first lens, second lens, third lens, fourth lens, fifth lens, and sixth lens are f1, f2, f3, f4, f5, and f6, respectively, wherein f1, f2, f3, f4, f5, and f6 satisfy the following ratio with f: -3.0 <f1 / f<-2.0,-5.0<f2 / f<-4.0,2.0<f3 / f<3.0,-6.0<f4 / f<-5.0,3.0<f5 / f<4.0,3.0<f6 / f<4.0。

[0023] In this embodiment of the invention, the first lens satisfies the relationship: 2.0 ≤ N d ≤2.3, V d ≤50; the second lens satisfies the relationship: 1.3≤N d ≤1.6, V d ≥50; The third lens satisfies the relationship: 1.7≤N d ≤2.0, V d ≤50; The fourth lens satisfies the relationship: 1.7≤N d ≤2.0, V d ≤50; the fifth lens satisfies the relationship: 2.0≤N d ≤2.3, V d ≤50; The sixth lens satisfies the relationship: 2.0≤N d ≤2.3, V d ≤50; where N d V is the refractive index. d Let be Abbe's constant.

[0024] In this embodiment of the invention, the total optical length (TTL) of the optical system and the focal length (f) of the optical system satisfy the following condition: TTL / f ≤ 9.7.

[0025] In this embodiment of the invention, the image height H of the optical system and the focal length f of the optical system satisfy the following condition: H / f≥1.2.

[0026] In this embodiment of the invention, the F-number of the optical system is ≤1.6.

[0027] In this embodiment of the invention, a filter IR and an imaging surface IMA are sequentially arranged behind the sixth lens; when light is incident, the light path passes through the first lens, the second lens, the third lens, the fourth lens, and the fifth lens in sequence to form an image.

[0028] In this embodiment of the invention, each lens is made of glass material, and the first lens, second lens, third lens, fourth lens, fifth lens and sixth lens are all glass spherical lenses. In this embodiment of the invention, the technical specifications achieved by the optical system are as follows: (1) Focal length: 2.0≤EFFL≤2.5mm; (2) Aperture F≤1.6; (3) Field of view: 2w ≥ 150°; (4) Principal ray incident angle: CRA≤3°; (5) Operating band: near-infrared band.

[0029] To achieve the above design parameters, the specific design parameters of the optical system in this embodiment of the invention are shown in Table 1 below: Table 1 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.

[0030] 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.

[0031] Furthermore, if the present 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 using a casting process) (except where it is obviously impossible to use an integral molding process).

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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 small imaging lens, characterized in that, The system includes an optical system consisting of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens arranged sequentially from left to right along the incident light path; the first lens is a meniscus negative lens, the second lens is a meniscus negative lens, the third lens is a biconvex positive lens, the fourth lens is a meniscus negative lens, the fifth lens is a plano-convex positive lens, and the sixth lens is a biconvex positive lens.

2. A small imaging lens according to claim 1, characterized in that, The first lens has a convex object-side surface and a concave image-side surface; the second lens has a convex object-side surface and a concave image-side surface; the third lens has a convex object-side surface and a convex image-side surface; the fourth lens has a convex object-side surface and a concave image-side surface; the fifth lens has a flat object-side surface and a convex image-side surface; and the sixth lens has a convex object-side surface and a convex image-side surface.

3. A small imaging lens according to claim 1, characterized in that, The air gap between the first lens and the second lens is 2.0~2.5mm; the air gap between the second lens and the third lens is 1.0~1.5mm; an aperture stop is provided between the third lens and the fourth lens, the air gap between the third lens and the aperture stop is -0.5~0.0mm; the air gap between the aperture stop and the fourth lens is 1.0~1.5mm; the air gap between the fourth lens and the fifth lens is 0.5~1.0mm; and the air gap between the fifth lens and the sixth lens is 0.1~0.5mm.

4. A small imaging lens according to claim 1, characterized in that, The focal length of the optical system is set to f. The focal lengths of the first, second, third, fourth, fifth, and sixth lenses are f1, f2, f3, f4, f5, and f6, respectively, where f1, f2, f3, f4, f5, and f6 satisfy the following ratio with f: -3.0 <f1 / f<-2.0,-5.0<f2 / f<-4.0,2.0<f3 / f<3.0,-6.0<f4 / f<-5.0,3.0<f5 / f<4.0,3.0<f6 / f<4.0。 5. A small imaging lens according to claim 1, characterized in that, The first lens satisfies the relationship: 2.0 ≤ N d ≤2.3, V d ≤50; the second lens satisfies the relationship: 1.3≤N d ≤1.6, V d ≥50; The third lens satisfies the relationship: 1.7≤N d ≤2.0, V d ≤50; The fourth lens satisfies the relationship: 1.7≤N d ≤2.0, V d ≤50; the fifth lens satisfies the relationship: 2.0≤N d ≤2.3, V d ≤50; The sixth lens satisfies the relationship: 2.0≤N d ≤2.3, V d ≤50; where N d V is the refractive index. d Let be Abbe's constant.

6. A miniature imaging lens according to claim 1, characterized in that, The total optical length (TTL) of an optical system and the focal length (f) of the optical system satisfy the following condition: TTL / f ≤ 9.

7.

7. A small imaging lens 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.

2.

8. A small imaging lens according to claim 1, characterized in that, The F-number of the optical system is ≤1.

6.

9. A small imaging lens according to claim 1, characterized in that, A filter and an imaging surface are sequentially arranged behind the sixth lens.

10. An imaging method using a small imaging lens as described in any one of claims 1-9, characterized in that, When light is incident, the light path passes through the first lens, the second lens, the third lens, the fourth lens, and the fifth lens in sequence to form an image.

Images