Low-cost 8m forward-looking optical system and imaging method thereof

Abstract

The application relates to a low-cost 8M forward-looking optical system and an imaging method thereof. The optical system has lenses with optical power along an incident light path in sequence, and the lenses are a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens. A diaphragm is arranged between the fourth lens and the fifth lens, wherein the fifth lens and the sixth lens are tightly connected to form a cemented lens group. The first lens is a meniscus concave negative lens, the second lens is a meniscus concave negative lens, the third lens is a meniscus convex positive lens, the fourth lens is a double-convex positive lens, the fifth lens is a double-convex positive lens, the sixth lens is a double-concave negative lens, and the seventh lens is a double-convex positive lens. The first lens, the second lens, the fourth lens, the fifth lens and the sixth lens are glass spherical lenses, and the third lens and the seventh lens are plastic aspherical lenses. The lens has the advantages of an imaging angle greater than 194 degrees, super-high 8M imaging definition, a large light aperture, low tolerance sensitivity, good high-low temperature stability and the like.

Description

TECHNICAL FIELD

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

[0002] Since entering the 21st century, people's demand for automobiles is no longer satisfied with more powerful power, more comfortable driving experience and more reliable safety. With the development of technologies such as electronics, artificial intelligence, 5G and industrial design and manufacturing capabilities, intelligentization has become a certainty trend in the development of today's automobile industry, and intelligent automobile technologies represented by automatic driving, ADAS and intelligent cockpit have become the technology highland that is fiercely competed for by major technology companies.

[0003] The forward-looking camera installed on the front windshield is mainly used to realize the visual perception and recognition function of driving, and can be divided into a forward-looking main camera, a forward-looking narrow-angle camera and a forward-looking wide-angle camera according to the function, but the adoption of the three cameras greatly increases the cost of the entire camera module, which is not conducive to the popularization of the market. Therefore, an ultra-wide-angle 8MP lens is adopted to realize a single-lens forward-looking camera module, but in order to consider the optical performance such as ultra-wide-angle, high image quality, large light aperture and low temperature drift, multiple glass pieces are often used, resulting in an increase in cost. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a low-cost 8M forward-looking optical system and an imaging method thereof, which has a large imaging angle and meets the low-cost 8M ultra-wide-angle imaging performance requirements of the lens and has a small size.

[0005] The application adopts the following scheme: a low-cost 8M forward-looking optical system, the optical system has lenses with optical power along the incident light path in sequence, which are a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens, and a diaphragm is arranged between the fourth lens and the fifth lens, wherein the fifth lens and the sixth lens are tightly connected to form a cemented lens group; the first lens is a meniscus concave negative lens, the second lens is a meniscus concave negative lens, the third lens is a meniscus convex positive lens, the fourth lens is a double-convex positive lens, the fifth lens is a double-convex positive lens, the sixth lens is a double-concave negative lens, and the seventh lens is a double-convex positive lens; the first, second, fourth, fifth and sixth lenses are glass spherical lenses, and the third and seventh lenses are plastic aspherical lenses.

[0006] 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 ratios: -4.0 < f1 / f < -3.0, -3.0 < f2 / f < -2.0, 11.0 < f3 / f < 12.0, 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.

[0007] Further, the first lens satisfies the relationship: 2.0 ≤ Nd ≤ 2.3 and Vd ≤ 50.0, the second lens satisfies the relationship: 1.7 ≤ Nd ≤ 2.0 and Vd ≤ 50.0, the third lens satisfies the relationship: 1.5 ≤ Nd ≤ 1.8 and Vd ≤ 50.0, the fourth lens satisfies the relationship: 2.0 ≤ Nd ≤ 2.3 and Vd ≤ 50.0, the fifth lens satisfies the relationship: 1.7 ≤ Nd ≤ 2.0 and Vd ≤ 50.0, the sixth lens satisfies the relationship: 1.7 ≤ Nd ≤ 2.0 and Vd ≤ 50.0, and the seventh lens satisfies the relationship: 1.5 ≤ Nd ≤ 1.8 and Vd ≥ 50.0; wherein Nd is the refractive index and Vd is the Abbe number.

[0008] Further, 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, the air gap between the third lens and the fourth lens is 1.1-1.5mm, the air gap between the fourth lens and the diaphragm is 0.1-0.5mm, the air gap between the diaphragm and the fifth lens is 0.1-0.5mm, and the air gap between the sixth lens and the seventh lens is 0.5-1.0mm.

[0009] Further, the total optical length TTL of the optical system and the focal length f of the optical system satisfy the relationship: TTL / f ≤ 10.0.

[0010] Further, the F number of the optical system is ≤1.6.

[0011] Further, the image height H of the optical system and the focal length f of the optical system satisfy the relationship: H / f ≥ 1.0.

[0012] Further, the rear side of the seventh lens is provided with a filter.

[0013] Another technical solution of the present application is an imaging method of the low-cost 8M forward-looking optical system as described above, and the light rays are sequentially imaged after passing through 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 filter.

[0014] Compared with the prior art, the present application has the following beneficial effects:

[0015] 1. The lens has an imaging angle of more than 194 degrees for an object, and has the advantages of super-high 8M imaging definition, large light aperture, low tolerance sensitivity, and good high-low temperature stability, etc. Meanwhile, the lens can monitor the scene outside the vehicle more comprehensively.

[0016] 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.

[0017] 3. The glass-plastic hybrid structure is adopted, which has low manufacturing cost and light weight, and is beneficial to the manufacturing and installation of the module.

[0018] 4. The lens can make good compensation for the focal plane displacement at high and low temperatures, and has complex environment adaptability.

[0019] 5. The axial color difference, sagittal color difference, and high-order color difference are corrected, so that the imaging system can also have high imaging quality at a large angle.

[0020] 6. The advantages of aspheric lens in correcting aberration are fully utilized, so that the lens can meet the requirement of high-definition imaging while having smaller lens outer diameter and shorter total optical length, and ensure the miniaturization of the lens.

[0021] In order to make the purpose, technical scheme and advantages of the present application more clear, specific embodiments and related drawings will be further described in detail below. BRIEF DESCRIPTION OF DRAWINGS

[0022] Fig. 1 is a schematic diagram of the optical structure of the present application;

[0023] Fig. 2 is an axial color difference diagram of the full working waveband of the present application;

[0024] Fig. 3 is a sagittal color difference diagram of the full working waveband of the present application;

[0025] Fig. 4 is a field curvature distortion diagram of the full working waveband of the present application;

[0026] Explanation of reference numerals in the drawings: STO - diaphragm; L1 - first lens; L2 - second lens; L3 - third lens; L4 - fourth lens; L5 - fifth lens; L6 - sixth lens; L7 - seventh lens; L8 - equivalent glass flat plate; L9 - equivalent glass flat plate; IMA - imaging surface. DETAILED DESCRIPTION

[0027] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0028] 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.

[0029] like Figs. 1-4 As shown, a low-cost 8M forward-looking optical system comprises lenses of optical power along the incident light path, namely 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 fourth and fifth lenses. The fifth and sixth lenses are closely connected to form a cemented lens group. Ignoring the curvature caused by aspherical coefficients, the first lens is a meniscus negative lens with a convex object-side surface and a concave image-side surface; the second lens is also a meniscus negative lens with a convex object-side surface and a concave image-side surface. The third lens is a meniscus convex positive lens with a convex object side and a concave 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 biconcave negative lens with a concave object side and a concave image side; the seventh lens is a biconvex positive lens with a convex object side and a convex image side; the lenses are made of plastic and glass, with the first, second, fourth, fifth, and sixth lenses being glass spherical lenses, and the third and seventh lenses being plastic aspherical lenses.

[0030] The well-chosen lens combination enables the optical system to achieve low cost, 8M resolution, ultra-wide angle, large aperture, day and night confocal focus, and low temperature drift design. Simultaneously, it effectively corrects on-axis and off-axis aberrations, resulting in good image quality. Figs. 2-4 As shown.

[0031] In the embodiment, 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, 11.0 < f3 / f < 12.0, 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.

[0032] In the embodiment, the first lens satisfies the relationship: 2.0 ≤ Nd ≤ 2.3 and Vd ≤ 50.0; the second lens satisfies the relationship: 1.7 ≤ Nd ≤ 2.0 and Vd ≤ 50.0; the third lens satisfies the relationship: 1.5 ≤ Nd ≤ 1.8 and Vd ≤ 50.0; the fourth lens satisfies the relationship: 2.0 ≤ Nd ≤ 2.3 and Vd ≤ 50.0; the fifth lens satisfies the relationship: 1.7 ≤ Nd ≤ 2.0 and Vd ≤ 50.0; the sixth lens satisfies the relationship: 1.7 ≤ Nd ≤ 2.0 and Vd ≤ 50.0; and the seventh lens satisfies the relationship: 1.5 ≤ Nd ≤ 1.8 and Vd ≥ 50.0; wherein Nd is the refractive index and Vd is the Abbe number.

[0033] In the embodiment, the axial distance between each lens satisfies the following relationship: the air gap between the first lens and the second lens is 2.0-2.5 mm; the air gap between the second lens and the third lens is 1.0-1.5 mm; the air gap between the third lens and the fourth lens is 1.1-1.5 mm; the air gap between the fourth lens and the diaphragm is 0.1-0.5 mm; the air gap between the diaphragm and the fifth lens is 0.1-0.5 mm; and the air gap between the sixth lens and the seventh lens is 0.5-1.0 mm.

[0034] In the embodiment, the third lens and the seventh lens are aspherical lenses, and the aspherical curve equation expression is:

[0035] wherein Z is the sagittal height 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, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y and Z are high-order term coefficients.

[0036] The aspherical coefficients of each aspherical lens are as follows:

[0037]

[0038] In the embodiment, the total optical length TTL of the optical system and the focal length f of the optical system satisfy: TTL / f ≤ 10.0.​

[0039] In the embodiment, the F number of the optical system is ≤1.6.

[0040] 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.

[0041] In the embodiment, the rear side of the seventh lens is provided with a filter.

[0042] The technical index realized by the optical system in the embodiment is as follows:

[0043] Focal length: 1.0 ≤EFFL ≤2.0 mm;

[0044] F number: F ≤1.6;

[0045] Field of view: 2w ≥194°;

[0046] Working waveband: visible light waveband.

[0047] To realize the design parameters mentioned above, the specific parameter design of the optical system in the embodiment is shown in the following table:

[0048]

[0049] The optical system in the embodiment realizes small size of the lens group by reasonably allocating the optical power, surface type of each lens, the central thickness of each lens, and the on-axis distance between each lens, etc., while meeting the low-cost 8M super wide-angle imaging performance requirements of the lens.

[0050] An imaging method of the low-cost 8M forward-looking optical system as mentioned above, light rays are sequentially imaged after passing through 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 filter.

[0051] Any technical solution disclosed in the present application, unless otherwise stated, if it discloses a numerical range, the disclosed numerical range is a preferred numerical range, 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 values, it is impossible to enumerate them all, so the present application only discloses some values to illustrate the technical solutions of the present application, and the above-mentioned enumerated values should not constitute a limitation on the protection scope of the present application.

[0052] If the present application discloses or involves mutually fixedly connected parts or structural members, unless otherwise stated, the fixed connection can be understood as: detachably fixedly connected (for example, connected using bolts or screws), and can also be understood 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, integrally formed by using a casting process) (obviously, an integral forming process cannot be used).

[0053] In addition, the terms used to represent the positional relationship or shape in any of the technical solutions disclosed in the present application include states or shapes similar, similar or close to them, unless otherwise stated.

[0054] 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.

[0055] The above 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 on the basis of the technical essence of the present application to the above embodiments without departing from the technical solution content of the present application still belongs to the protection scope of the present application.

Claims

1. A low cost 8M forward looking optical system characterized by: The lens with optical power along the incident light path of 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 arranged in sequence, and a diaphragm is arranged between the fourth lens and the fifth lens, wherein the fifth lens and the sixth lens are tightly arranged to form a cemented lens group; the first lens is a meniscus concave negative lens, the second lens is a meniscus concave negative lens, the third lens is a meniscus convex positive lens, the fourth lens is a biconvex positive lens, the fifth lens is a biconvex positive lens, the sixth lens is a biconcave negative lens, and the seventh lens is a biconvex positive lens; the first lens, the second lens, the fourth lens, the fifth lens and the sixth lens are glass spherical lenses, and the third lens and the seventh lens are plastic aspherical lenses; the air gap between the first lens and the second lens is 2.390 mm; the air gap between the second lens and the third lens is 1.355 mm; the air gap between the third lens and the fourth lens is 1.206 mm; the air gap between the fourth lens and the diaphragm is 0.270 mm; the air gap between the diaphragm and the fifth lens is 0.348 mm; and the air gap between the sixth lens and the seventh lens is 0.949 mm.

2. The low cost 8M forward looking optical system of claim 1, wherein: 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: -4.0 < f1 / f < -3.0, -3.0 < f2 / f < -2.0, 11.0 < f3 / f < 12.0, 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.

3. The low cost 8M forward looking optical system of claim 1, wherein: The first lens satisfies the relationship: Nd = 2.0 and Vd = 29.13; the second lens satisfies the relationship: Nd = 1.80 and Vd = 46.57; the third lens satisfies the relationship: Nd = 1.66 and Vd = 20.38; the fourth lens satisfies the relationship: Nd = 2.0 and Vd = 29.13; the fifth lens satisfies the relationship: Nd = 1.80 and Vd = 46.57; the sixth lens satisfies the relationship: Nd = 1.95 and Vd = 17.94; and the seventh lens satisfies the relationship: Nd = 1.54 and Vd = 55.71; wherein Nd is the refractive index and Vd is the Abbe number.

4. The low cost 8M forward looking optical system of claim 1, wherein: The total optical length TTL of the optical system and the focal length f of the optical system satisfy: TTL / f ≤ 10.

0.

5. The low cost 8M forward looking optical system of claim 1, wherein: The F number of the optical system is ≤ 1.

6.

6. The low cost 8M forward looking optical system of claim 1, wherein: The image height H of the optical system and the focal length f of the optical system satisfy: H / f ≥ 1.

0.

7. The low cost 8M forward looking optical system of claim 1, wherein: The rear side of the seventh lens is provided with a filter.

8. A method of imaging for a low cost 8M forward looking optical system as claimed in claim 7, characterized by: The light rays are sequentially imaged after passing through 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 filter.

Images