Low total length 8m forward looking optical system and method of operation thereof

Abstract

The application relates to a low-total-length 8M forward-looking optical system and a working method thereof, characterized in that the optical system is composed of a first lens, a second lens, a third lens, a fourth lens, a diaphragm, a fifth lens, a sixth lens and a seventh lens arranged in sequence from left to right along the light path of light incidence. The lenses are made of plastic and glass materials, the first, second, fourth, fifth and sixth lenses are glass spherical lenses, the third and seventh lenses are plastic aspherical lenses, and the fifth and sixth lenses are cemented lens groups. By reasonably distributing the optical power, surface type, central thickness of each lens and the distance between the lenses on the optical axis, the total length of the lens and the radial size of each lens are reduced while meeting the requirements of the forward-looking wide-angle camera and the forward-looking narrow-angle camera, and the lens group is miniaturized.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of lenses, in particular to a low-total-length 8M forward-looking optical system and a working method thereof. BACKGROUND

[0002] A vehicle-mounted camera module needs to select a lens with different field angles according to different use scenarios. For example, in a lane departure detection system and a driver fatigue detection system, in order to improve the detection accuracy and reduce the distortion of the picture edge, a lens with a suitable field angle range needs to be selected for the vehicle-mounted camera module, and an ultra-wide-angle lens is generally selected.

[0003] Among them, the forward-looking vehicle-mounted lens is an important part of the advanced driver assistance system, and the driver can discover obstacles in front of the vehicle through the forward-looking vehicle-mounted lens to avoid driving accidents; according to the function, it can be divided into a forward-looking main camera, a forward-looking narrow-angle camera and a forward-looking wide-angle camera, but the use of the three cameras greatly increases the cost of the entire camera module, which is not conducive to market popularization.

[0004] To realize a single-lens module, the forward-looking optical lens needs to meet the requirements of 8M high resolution, large field angle, good environmental adaptability and the like, and therefore has the shortcomings of a large number of lenses and a long optical total length, which is not conducive to the miniaturization of the overall system.

[0005] At present, the searched Chinese patent "Vehicle-mounted forward-looking optical lens" with the announcement number CN216870927U is provided with a first lens, a second lens, a third lens, a diaphragm, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an infrared filter I R, a protective glass CG and an image plane I MA in sequence along the light incidence direction; wherein the first lens is a glass aspheric lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens are all glass spherical lenses; wherein the fifth lens and the sixth lens are combined to form a cemented lens or the fourth lens and the fifth lens are combined to form a cemented lens; the patent provides a vehicle-mounted forward-looking optical lens with high resolution, large aperture, high resolution, large field of view and low production cost; but the lens cannot replace the forward-looking wide-angle camera and the forward-looking narrow-angle camera to realize a single-lens forward-looking camera module. SUMMARY

[0006] In view of the shortcomings of the prior art, the purpose of the present application is to provide a low-total-length 8M forward-looking optical system. The optical system of the present application can realize low total length and low cost 8MP imaging while realizing the visual perception and recognition function of driving, so as to replace the forward-looking wide-angle camera and the forward-looking narrow-angle camera to realize a single-lens forward-looking camera module, greatly reduce the cost and improve the market popularization.

[0007] In order to solve the above technical problems, the technical scheme of the present application is: a low total length 8M forward-looking optical system, the optical system is composed of a first lens, a second lens, a third lens, a fourth lens, a diaphragm, a fifth lens, a sixth lens and a seventh lens in sequence from left to right along the light path; the first lens is a meniscus concave negative lens, the object side surface is a convex surface, and the image side surface is a concave surface; the second lens is a meniscus concave negative lens, the object side surface is a convex surface, and the image side surface is a concave surface; the third lens is a meniscus concave negative lens, the object side surface is a concave surface, and the image side surface is a convex surface; the fourth lens is a double-convex positive lens, the object side surface is a convex surface, and the image side surface is a convex surface; the fifth lens is a double-convex positive lens, the object side surface is a convex surface, and the image side surface is a convex surface; the sixth lens is a double-concave negative lens, the object side surface is a concave surface, and the image side surface is a concave surface; the seventh lens is a double-convex positive lens, the object side surface is a convex surface, and the image side surface is a convex surface; the image side surface of the fifth lens and the object side surface of the sixth lens are cemented to form a cemented lens group; the first, second, fourth, fifth and sixth lenses are glass spherical lenses, and the third and seventh lenses are plastic aspherical lenses.

[0008] Preferably, the focal length of the optical system is f, and the focal lengths of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens are f1, f2, f3, f4, f5, f6 and f7 respectively, wherein f1, f2, f3, f4, f5, f6 and f7 satisfy the following ratios: -4.0 < f1 / f < -3.0, -3.0 < f2 / f < -2.0, -14.0 < f3 / f < -13.0, 2.0 < f4 / f < 3.0, 1.0 < f5 / f < 2.0, -2.0 < f6 / f < -1.0, and 3.0 < f7 / f < 4.0.

[0009] Preferably, the first lens satisfies the relationship: 2.0 ≤ N d ≤ 2.3, V d ≤ 50.0; the second lens satisfies the relationship: 1.7 ≤ N d ≤ 2.0, V d ≤ 50.0; the third lens satisfies the relationship: 1.5 ≤ N d ≤ 1.8, V d ≤ 50.0; the fourth lens satisfies the relationship: 1.7 ≤ N d ≤ 2.0, V d ≤ 50.0; the fifth lens satisfies the relationship: 1.7 ≤ N d ≤ 2.0, V d ≤ 50.0; the sixth lens satisfies the relationship: 1.7 ≤ N d ≤ 2.0, V d ≤ 50.0; and the seventh lens satisfies the relationship: 1.5 ≤ N d ≤ 1.8, V d ≥ 50.0; wherein N dV is the refractive index, and d V is the Abbe number.

[0010] Preferably, the distance between each lens on the optical axis satisfies the following relationship: the air gap between the first lens and the second lens is 1.5-2.0 mm; the air gap between the second lens and the third lens is 2.5-3.0 mm; the air gap between the third lens and the fourth lens is 0.1-0.5 mm; the air gap between the fourth lens and the diaphragm is 0.5-1.0 mm; the air gap between the diaphragm and the fifth lens is 0.1-0.5 mm; the fifth lens and the sixth lens are a cemented lens, and the air gap is 0 mm; and the air gap between the sixth lens and the seventh lens is 0.5-1.0 mm.

[0011] Preferably, the third lens and the seventh lens are both aspherical lenses, and the aspherical curve equation is expressed as:

[0012]

[0013] wherein Z is the sagittal height of the aspherical surface at a height of r along the optical axis from the vertex of the aspherical surface; c is the paraxial curvature of the aspherical surface; k is the conic constant; and α1, α2, α3, α4, α5, α6, α7, and α8 are all high-order coefficients.

[0014] Preferably, the total optical length TTL of the optical system and the focal length f of the optical system satisfy: TTL / f≤11.0.

[0015] Preferably, the F number of the optical system is ≤1.6.

[0016] Preferably, the image height H of the optical system and the focal length f of the optical system satisfy: H / f≥1.0.

[0017] Preferably, the rear side of the seventh lens is provided with a filter.

[0018] Compared with the prior art, the present application has the following advantages:

[0019] 1. The lens has an imaging angle of more than 194 degrees for an object, and simultaneously has the advantages of super-high 8M imaging clarity, large light aperture, low tolerance sensitivity, and good high-low temperature stability, etc. Meanwhile, the lens can more comprehensively monitor the scene outside the vehicle.

[0020] 2. By reasonably matching each optical lens, the system structure is compact and reasonable, the total length is 17 mm, easy to assemble, the tolerance sensitivity is low, and it is more suitable for large-scale high-yield production.

[0021] 3. The glass-plastic hybrid structure is adopted, which has a low manufacturing cost and a light weight, and is beneficial to the manufacturing and installation of the module.

[0022] 4. It can effectively compensate for focal plane displacement at high and low temperatures, and has adaptability to complex environments;

[0023] 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.

[0024] 6. Fully leverage the advantages of aspherical lenses in correcting aberrations, achieving high-definition imaging while featuring a smaller lens outer diameter and shorter overall optical length, ensuring lens miniaturization.

[0025] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the optical structure of the present invention;

[0027] Figure 2 This is the axial chromatic aberration diagram of the entire working band of the present invention;

[0028] Figure 3 This is the transverse chromatic aberration diagram of the entire working band of the present invention;

[0029] Figure 4 This is the field curvature distortion diagram of the entire working band of the present invention;

[0030] 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; L8 - equivalent glass plate; L9 - equivalent glass plate; IMA - imaging plane. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and specific implementation methods.

[0032] like Figure 1 As shown, a low total length 8M forward-looking optical system is provided, wherein the optical system is provided with a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, an aperture, a fifth lens L5, a sixth lens L6 and a seventh lens L7 in sequence from the object side to the image side. Without considering the reverse curvature caused by the aspherical coefficients,The first lens is a meniscus concave negative lens, the object side surface of which is a convex surface, and the image side surface is a concave surface; the second lens is a meniscus concave negative lens, the object side surface of which is a convex surface, and the image side surface is a concave surface; the third lens is a meniscus concave negative lens, the object side surface of which is a concave surface, and the image side surface is a convex surface; the fourth lens is a double-convex positive lens, the object side surface of which is a convex surface, and the image side surface is a convex surface; the fifth lens is a double-convex positive lens, the object side surface of which is a convex surface, and the image side surface is a convex surface; the sixth lens is a double-concave negative lens, the object side surface of which is a concave surface, and the image side surface is a concave surface; the seventh lens is a double-convex positive lens, the object side surface of which is a convex surface, and the image side surface is a convex surface; the image side surface of the fifth lens and the object side surface of the sixth lens are cemented to form a cemented lens group; the first, second, fourth, fifth and sixth lenses are glass spherical lenses, and the third and seventh lenses are plastic aspherical lenses.

[0033] The first lens, the second lens and the third lens adopt lenses with negative focal lengths, which can adjust large-angle light, and the third lens is a plastic aspherical lens, which also has the effect of reducing the distortion of the optical system; the fifth lens and the sixth lens form an achromatic double-cemented lens; reasonable lens matching enables the optical system to achieve low cost, low total length, 8M, super wide angle, large aperture, day and night confocal, low temperature drift design, and simultaneously corrects on-axis and off-axis aberrations, and has good imaging quality.

[0034] The focal length of the optical system is f, and the focal lengths of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens are f1, f2, f3, f4, f5, f6 and f7 respectively, wherein f1, f2, f3, f4, f5, f6 and f7 satisfy the following ratios: -4.0 < f1 / f < -3.0, -3.0 < f2 / f < -2.0, -14.0 < f3 / f < -13.0, 2.0 < f4 / f < 3.0, 1.0 < f5 / f < 2.0, -2.0 < f6 / f < -1.0, and 3.0 < f7 / f < 4.0.

[0035] The first lens satisfies the relationship: 2.0 ≤ N d ≤ 2.3, V d ≤ 50.0; the second lens satisfies the relationship: 1.7 ≤ N d ≤ 2.0, V d ≤ 50.0; the third lens satisfies the relationship: 1.5 ≤ N d ≤ 1.8, V d ≤ 50.0; the fourth lens satisfies the relationship: 1.7 ≤ N d ≤ 2.0, V d ≤ 50.0; the fifth lens satisfies the relationship: 1.7 ≤ N d ≤ 2.0, V d ≤ 50.0; and the sixth lens satisfies the relationship: 1.7 ≤ N d ≤ 2.0, Vd ≤50.0; the seventh lens satisfies the relationship: 1.5≤N d ≤1.8, V d ≥50.0; wherein N d is the refractive index, V d is the Abbe number.

[0036] The distance between each lens on the optical axis satisfies the following relationship: the air gap between the first lens and the second lens is 1.5-2.0 mm; the air gap between the second lens and the third lens is 2.5-3.0 mm; the air gap between the third lens and the fourth lens is 0.1-0.5 mm; the air gap between the fourth lens and the diaphragm is 0.5-1.0 mm; the air gap between the diaphragm and the fifth lens is 0.1-0.5 mm; the fifth lens and the sixth lens are a cemented lens with an air gap of 0 mm; and the air gap between the sixth lens and the seventh lens is 0.5-1.0 mm.

[0037] The third lens and the seventh lens are both aspherical lenses, and the aspherical curve equation expression is:

[0038]

[0039] wherein Z is the sagittal height of the aspherical surface at a height of r along the optical axis from the vertex of the aspherical surface; c is the paraxial curvature of the aspherical surface; k is the conic constant; and α1, α2, α3, α4, α5, α6, α7, and α8 are high-order coefficients.

[0040] The total optical length TTL of the optical system and the focal length f of the optical system satisfy: TTL / f≤11.0; the F number of the optical system is ≤1.6; the image height H of the optical system and the focal length f of the optical system satisfy: H / f≥1.0; and the rear side of the seventh lens is provided with a filter.

[0041] As Figures 2 to 4 shown, the technical indicators achieved by the optical system of the embodiment of the present application are as follows:

[0042] (1) focal length: 1.0≤EFFL≤2.0 mm;

[0043] (2) aperture F≤1.6;

[0044] (3) field of view angle: 2w≥194°;

[0045] (4) working waveband: visible light waveband.

[0046] To achieve the above design parameters, the specific design adopted by the optical system of the embodiment is shown in the following table:

[0047]

[0048] The aspheric coefficients of the aspheric lenses of the optical system of the present embodiment are as follows:

[0049]

[0050] The optical system of the present embodiment, by reasonably allocating the focal power of each lens, the surface shape, the central thickness of each lens, and the distance between each lens on the optical axis, etc., while meeting the low total length 8M super wide-angle imaging performance requirements of the lens, reduces the total length of the lens and the radial size of each lens, and achieves miniaturization of the lens group.

[0051] The above description is only a preferred embodiment of the present application, and is not intended to limit the present application in other forms. Any person skilled in the art can modify or change the above disclosed technical content to equivalent embodiments. However, any simple modification, equivalent change and modification made according to the technical essence of the present application without departing from the technical solution content of the present application shall still fall within the protection scope of the present application.

Claims

1. A low overall length 8M forward looking optical system characterized by: The optical system is composed of a first lens, a second lens, a third lens, a fourth lens, a diaphragm, a fifth lens, a sixth lens and a seventh lens in sequence from left to right along the light path; the first lens is a meniscus concave negative lens, the object side surface of which is a convex surface and the image side surface is a concave surface; the second lens is a meniscus concave negative lens, the object side surface of which is a convex surface and the image side surface is a concave surface; the third lens is a meniscus concave negative lens, the object side surface of which is a concave surface and the image side surface is a convex surface; the fourth lens is a double-convex positive lens, the object side surface of which is a convex surface and the image side surface is a convex surface; the fifth lens is a double-convex positive lens, the object side surface of which is a convex surface and the image side surface is a convex surface; the sixth lens is a double-concave negative lens, the object side surface of which is a concave surface and the image side surface is a concave surface; the seventh lens is a double-convex positive lens, the object side surface of which is a convex surface and the image side surface is a convex surface; the image side surface of the fifth lens and the object side surface of the sixth lens are cemented to form a cemented lens group; the first, second, fourth, fifth and sixth lenses are glass spherical surface lenses, and the third and seventh lenses are plastic aspherical surface lenses; the specific parameters of the optical system are shown in the following table: 。 2. A working method of the low total length 8M forward-looking optical system according to claim 1, characterized in that: When the light is incident, it enters the first lens, the second lens, the third lens, the fourth lens, the diaphragm, the fifth lens, the sixth lens, the seventh lens and the equivalent glass flat plate in sequence along the light path, and then is imaged on the IMA imaging plane.

Images