Seven-piece 4k forward-viewing narrow-angle optical system and imaging method thereof

Abstract

The present application relates to a kind of seven-piece 4K front view narrow-angle optical system and its imaging method, the optical system has the lens of optical power in the order of first lens, second lens, third lens, fourth lens, fifth lens, sixth lens and seventh lens along the direction of incidence of optical path, diaphragm is arranged between third lens and fourth lens;First lens is meniscus positive lens, its object side is convex, and image side is concave;Second lens is double-concave negative lens;Third lens is meniscus positive lens, its object side is convex, and image side is concave;Fourth lens is double-concave negative lens;Fifth lens is double-convex positive lens;Sixth lens is double-convex positive lens;Seventh lens is meniscus negative lens, its object side is convex, and image side is concave;All lenses are made of glass material, wherein sixth, seventh lens is aspherical lens, second lens and third lens are tightly connected to form first cemented lens group, and fourth lens and fifth lens are tightly connected to form second cemented lens group.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lenses, in particular to a seven-piece 4K forward-viewing narrow-angle optical system and an imaging method thereof. BACKGROUND

[0002] Currently, vehicle-mounted cameras mounted on vehicles are mainly divided into five categories according to the installation position, namely, forward-viewing cameras, surround-view cameras, rear-view cameras, side-view cameras and built-in cameras. The forward-viewing camera is mainly installed on the front windshield and is used to realize the visual perception and recognition function of driving. According to the function, it can be divided into a forward-viewing main camera, a forward-viewing narrow-angle camera and a forward-viewing wide-angle camera. The forward-viewing narrow-angle camera is mainly used for target recognition such as traffic lights and pedestrians. Generally, a narrow-angle lens is selected, and a lens with an angle of about 30°~40° can be selected. On this basis, the market pursues higher pixel density and longer detection distance to improve the accuracy and application range of visual perception and recognition of driving. SUMMARY

[0003] Therefore, the purpose of the present application is to provide a seven-piece 4K forward-viewing narrow-angle optical system and an imaging method thereof, which can realize 4K clear imaging while having a small size.

[0004] The present application adopts the following scheme: a seven-piece 4K forward-viewing narrow-angle optical system, the optical system has lenses with optical power in the order of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens along the incident direction of the optical path, and a diaphragm is arranged between the third lens and the fourth lens; the first lens is a meniscus positive lens, the object side surface of which is convex, and the image side surface of which is concave; the second lens is a double-concave negative lens; the third lens is a meniscus positive lens, the object side surface of which is convex, and the image side surface of which is concave; the fourth lens is a double-concave negative lens; the fifth lens is a double-convex positive lens; the sixth lens is a double-convex positive lens; the seventh lens is a meniscus negative lens, the object side surface of which is convex, and the image side surface of which is concave; all the lenses are made of glass material, wherein the sixth and seventh lenses are aspherical lenses, the second lens and the third lens are in close contact to form a first cemented lens group, and the fourth lens and the fifth lens are in close contact to form a second cemented lens group.

[0005] Further, 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 proportions: 3.0<f1 / f<4.0, -1.0<f2 / f<0.0, 0.0<f3 / f<1.0, -1.0<f4 / f<0.0, 0.0<f5 / f<1.0, 0.0<f6 / f<1.0 and -2.0<f7 / f<-1.0.

[0006] Further, the first lens satisfies the relationship: 1.7≤N d ≤2.0, 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: 1.7≤N d ≤2.0, V d ≤50.0; the fourth lens satisfies the relationship: 1.5≤N d ≤1.8, 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: 1.5≤N d ≤1.8, V d ≥50.0; the seventh lens satisfies the relationship: 1.7≤N d ≤2.0, V d ≤50.0; wherein N d is the refractive index, V d is the Abbe number.

[0007] Further, the air gap between the first lens and the second lens is 1.5-2.0mm; the second lens and the third lens are a cemented lens group, and the air gap is 0mm; the air gap between the third lens and the diaphragm is 2.1-2.5mm; the air gap between the diaphragm and the fourth lens is 0.5-1.0mm; the fourth lens and the fifth lens are a cemented lens group, and the air gap is 0mm; the air gap between the fifth lens and the sixth lens is 0.1-0.5mm; and the air gap between the sixth lens and the seventh lens is 0.1-0.5mm.

[0008] Further, the total optical length TTL of the optical system and the focal length f of the optical system satisfy: TTL / f≤2.2;

[0009] Further, the F number of the optical system is ≤1.5.

[0010] Further, the image height H of the optical system and the focal length f of the optical system satisfy: H / f≤1.0.

[0011] Further, the rear side of the seventh lens is provided with a filter.

[0012] Another technical solution of the present application is an imaging method of the above-mentioned seven-piece 4K forward-looking narrow-angle optical system, and light rays are sequentially imaged after passing through the first lens, the second lens, the third lens, the diaphragm, the fourth lens, the fifth lens, the sixth lens, the seventh lens and the filter.

[0013] Compared with the prior art, the present application has the following beneficial effects:

[0014] 1. The lens has an imaging angle of more than 30 degrees for an object, and has the advantages of 4K imaging definition, large light aperture, low tolerance sensitivity, good high and low temperature stability, etc., and can monitor the scene in front of the vehicle and the distant scene more comprehensively.

[0015] 2. By reasonably matching the optical lenses, the system structure is compact and reasonable, easy to assemble, low in tolerance sensitivity, and more suitable for large-scale high-yield production.

[0016] 3. The all-glass structure has high stability, can compensate the focusing surface displacement well at high and low temperatures, and has complex environment adaptability.

[0017] 4. The axial color difference, the sagittal color difference and the high-order color difference are corrected, so that the imaging system can also have high imaging quality at a large angle.

[0018] In order to make the purpose, technical scheme and advantages of the present application clearer, the following will further describe the present application through specific examples and related drawings. BRIEF DESCRIPTION OF DRAWINGS

[0019] Fig. 1 is a schematic diagram of the optical system structure of the present application;

[0020] Fig. 2 is an axial color difference graph of the full working waveband of the present application;

[0021] Fig. 3 is a sagittal color difference graph of the full working waveband of the present application;

[0022] Fig. 4 is a field curvature distortion graph of the full working waveband of the present application;

[0023] In the figure: STO- stop; L1- first lens; L2- second lens; L3- third lens; L4- fourth lens; L5- fifth lens; L6- sixth lens; L7- seventh lens; L8- filter; L9- equivalent glass flat plate; IMA- imaging surface. DETAILED DESCRIPTION

[0024] It should be pointed out that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as generally understood by those skilled in the art to which the present application belongs.

[0025] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0026] like Figs. 1-4 As shown, a seven-element 4K forward-looking narrow-angle optical system comprises lenses of optical power arranged sequentially along the incident direction of the optical path: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens. An aperture stop is provided between the third and fourth lenses. Ignoring the curvature caused by aspherical coefficients, the first lens is a meniscus positive lens with a convex object-side surface and a concave image-side surface; the second lens is a biconcave negative lens with both object-side and image-side surfaces concave; the third lens is a meniscus positive lens with a convex object-side surface and a concave image-side surface; and the fourth lens is a biconcave... The first lens is a negative lens with a concave object side and a concave image side; the second lens is a biconvex positive lens with a convex object side and a convex 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 meniscus negative lens with a convex object side and a concave image side; all lenses are made of glass. The first, second, third, fourth, and fifth lenses are all spherical lenses, while the sixth and seventh lenses are aspherical lenses. The second and third lenses are closely connected to form the first cemented lens group, and the fourth and fifth lenses are closely connected to form the second cemented lens group.

[0027] The second and third lenses form an achromatic cemented doublet, and the fourth and fifth lenses also form an achromatic cemented doublet. This reasonable lens combination enables the optical system to achieve a small size, 4K resolution, large aperture, day and night confocal focus, and low temperature drift design. Simultaneously, it provides good correction for on-axis and off-axis aberrations, resulting in good image quality. Figs. 2-4 As shown.

[0028] 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. The ratios of f1, f2, f3, f4, f5, f6, and f7 to f satisfy the following ratio: 3.0 <f1 / f<4.0,-1.0<f2 / f<0.0,0.0<f3 / f<1.0,-1.0<f4 / f<0.0,0.0<f5 / f<1.0,0.0<f6 / f<1.0,-2.0<f7 / f<-1.0。

[0029] In the present embodiment, the first lens satisfies the relationship: 1.7 ≤ N d ≤ 2.0, 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: 1.7 ≤ N d ≤ 2.0, V d ≤ 50.0; the fourth lens satisfies the relationship: 1.5 ≤ N d ≤ 1.8, 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: 1.5 ≤ N d ≤ 1.8, V d ≥ 50.0; the seventh lens satisfies the relationship: 1.7 ≤ N d ≤ 2.0, V d ≤ 50.0; wherein N d is the refractive index, and V d is the Abbe number.

[0030] In the present embodiment, the air gap between the first lens and the second lens is 1.5-2.0 mm; the second lens and the third lens are a cemented lens group, and the air gap is 0 mm; the air gap between the third lens and the diaphragm is 2.1-2.5 mm; the air gap between the diaphragm and the fourth lens is 0.5-1.0 mm; the fourth lens and the fifth lens are a cemented lens group, and the air gap is 0 mm; the air gap between the fifth lens and the sixth lens is 0.1-0.5 mm; and the air gap between the sixth lens and the seventh lens is 0.1-0.5 mm.

[0031] In the present embodiment, the sixth and seventh lenses are both aspherical lenses. The aspherical curve equation expression is:

[0032] ,

[0033] wherein Z is the sag of the aspherical surface at a height of r along the optical axis; c is the paraxial curvature of the aspherical surface; k is the conic constant; and A , , , , , , , are the high-order term coefficients.

[0034] The aspherical surface coefficients of the aspherical lenses of the optical system of the present embodiment are as follows:

[0035]

[0036] In the embodiment, the total track length TTL of the optical system and the focal length f of the optical system satisfy: TTL / f≤2.2.

[0037] In the embodiment, the F number of the optical system is ≤1.5.

[0038] In the embodiment, the image height H of the optical system and the focal length f of the optical system satisfy: H / f≤1.0.

[0039] In the embodiment, the rear side of the seventh lens is provided with a filter.

[0040] The technical index realized by the optical system in the embodiment is as follows:

[0041] (1) focal length: 14.0≤EFFL≤15.0mm;

[0042] (2) aperture F≤1.5;

[0043] (3) field of view angle: 2w≥30°;

[0044] (4) working waveband: visible light waveband.

[0045] To realize the design parameters, the specific design of the optical system in the embodiment is as follows:

[0046]

[0047] The optical system in the embodiment realizes the miniaturization of the lens group by reasonably distributing the optical power, surface shape, central thickness of each lens, and on-axis distance between each lens, etc., while meeting the 4K imaging performance requirements of the lens.

[0048] The mechanical structure part (i.e. the barrel structure) matched with the optical system is a conventional prior art, and will not be specifically described here.

[0049] An imaging method of the seven-piece 4K forward-looking narrow-angle optical system is provided, and light rays are sequentially imaged after passing through the first lens, the second lens, the third lens, the diaphragm, the fourth lens, the fifth lens, the sixth lens, the seventh lens, and the filter.

[0050] If the above-mentioned any technical solution of the present application discloses a numerical range, the disclosed numerical range is a preferred numerical range, and any person skilled in the art should understand that the preferred numerical range is only one of the many implementable numerical values with more obvious technical effects or representative values. Because there are too many numerical values to enumerate, the present application discloses some numerical values to illustrate the technical solutions of the present application, and the above-mentioned enumerated numerical values should not constitute a limitation on the protection scope of the present application.

[0051] If the present application discloses or involves mutually fixed connecting parts or structural parts, the fixed connection can be understood as: detachable fixed connection (for example, using bolt or screw connection), or as: non-detachable fixed connection (for example, riveting, welding), of course, the mutually fixed connection can also be replaced by an integral structure (for example, using casting process to integrally form and manufacture) (except for obvious cases that cannot use integral forming process).

[0052] In addition, the terms used to represent the positional relationship or shape in any technical solution disclosed above, unless otherwise stated, include states or shapes that are approximate, similar or close to them.

[0053] Any component provided by the present application can be assembled from multiple individual components, or can be a single component manufactured by an integral forming process.

[0054] The above is only a preferred embodiment of the present application, and is not a limitation on other forms of the present application. Any person skilled in the art can modify or change the above-mentioned 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 still belongs to the protection scope of the present application.

Claims

1. A seven-piece 4K forward-viewing narrow-angle optical system characterized by: The optical system has lenses with optical power in sequence along the light path in the direction of incidence of the light path, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens, a diaphragm is arranged between the third lens and the fourth lens, the number of lenses with optical power in the optical system is 7; the first lens is a meniscus positive lens, the object side surface of which is convex and the image side surface of which is concave; the second lens is a double-concave negative lens; the third lens is a meniscus positive lens, the object side surface of which is convex and the image side surface of which is concave; the fourth lens is a double-concave negative lens; the fifth lens is a double-convex positive lens; the sixth lens is a double-convex positive lens; the seventh lens is a meniscus negative lens, the object side surface of which is convex and the image side surface of which is concave; all the lenses are made of glass material, wherein the sixth lens and the seventh lens are aspherical lenses, the second lens and the third lens are in close contact to form a first cemented lens group, and the fourth lens and the fifth lens are in close contact to form a second cemented lens group; 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 and f satisfy the following ratios: 3.0 < f1 / f < 4.0, -1.0 < f2 / f < 0.0, 0.0 < f3 / f < 1.0, -1.0 < f4 / f < 0.0, 0.0 < f5 / f < 1.0, 0.0 < f6 / f < 1.0, and -2.0 < f7 / f < -1.0; the total optical length TTL of the optical system and the focal length f of the optical system satisfy: TTL / f ≤ 2.2; the image height H of the optical system and the focal length f of the optical system satisfy: H / f ≤ 1.

0.

2. The seven-piece 4K front-view narrow angle optical system of claim 1, wherein: The first lens satisfies the relationship: 1.7 ≤ N d ≤ 2.0, 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: 1.7 ≤ N d ≤ 2.0, V d ≤ 50.0; the fourth lens satisfies the relationship: 1.5 ≤ N d ≤ 1.8, 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: 1.5 ≤ N d ≤ 1.8, V d ≥ 50.0; the seventh lens satisfies the relationship: 1.7 ≤ N d ≤ 2.0, V d ≤ 50.0; wherein N d is the refractive index, and V d is the Abbe number.

3. The seven-piece 4K front-view narrow angle optical system of claim 1, wherein: The air gap between the first lens and the second lens is 1.5-2.0 mm; the second lens and the third lens form the first cemented lens group, and the air gap is 0 mm; the air gap between the third lens and the diaphragm is 2.1-2.5 mm; the air gap between the diaphragm and the fourth lens is 0.5-1.0 mm; the fourth lens and the fifth lens form the second cemented lens group, and the air gap is 0 mm; the air gap between the fifth lens and the sixth lens is 0.1-0.5 mm; and the air gap between the sixth lens and the seventh lens is 0.1-0.5 mm.

4. The seven-piece 4K front-view narrow angle optical system of claim 1, wherein: The F number of the optical system is ≤1.

5.

5. The seven-piece 4K front-view narrow angle optical system of claim 1, wherein: The rear side of the seventh lens is provided with a filter.

6. An imaging method of the seven-piece 4K forward-viewing narrow angle optical system according to claim 5, characterized in that: Light rays are sequentially imaged through the first lens, the second lens, the third lens, the diaphragm, the fourth lens, the fifth lens, the sixth lens, the seventh lens and the filter.

Images