Six-piece 8m front-view optical system and imaging method

Abstract

The present application relates to a kind of six-piece 8M front-view optical systems and imaging method, optical lens is sequentially provided with first lens, diaphragm, second lens, third lens, fourth lens, fifth lens and sixth lens from object side to image side.Lens is made of glass material, first, second, third, fifth, sixth lens is glass spherical lens, fourth lens is glass aspherical lens, wherein second lens and third lens, fifth lens and sixth lens are cemented lens group.By reasonably distributing the optical power of each lens, surface type, the center thickness of each lens and the axial distance between each lens, etc., while meeting the 8M imaging performance of six-piece lens to replace the requirements of front-view wide-angle camera and front-view narrow-angle camera, the total length of the lens and the radial dimension of each lens are reduced, and the lens group is miniaturized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lens, in particular to a six-piece 8M forward-looking optical system and imaging method. BACKGROUND

[0002] The functions of the vehicle-mounted forward-looking camera system mainly include two aspects: one is to record the driving track, which is one of the important basis for determining the responsibility after the traffic accident; the other is to assist driving, which can prevent lane deviation and avoid colliding with pedestrians on the road during driving, thereby effectively reducing the occurrence of traffic accidents. Therefore, the vehicle-mounted forward-looking camera system is an important hardware terminal in the advanced driving assistance system. According to the functions, the forward-looking camera can be divided into a forward-looking main camera, a forward-looking narrow-angle camera and a forward-looking wide-angle camera. The function of the forward-looking wide-angle camera is mainly to identify objects at a relatively close distance, which is mainly used in urban road conditions, low-speed driving and other scenes, and the field of view angle is 120°-150° and the detection distance is about 50m. Therefore, if 8MP lenses are widely used, the camera can be replaced, thereby reducing the cost of the forward-looking module, and at the same time, the lower number of lenses is beneficial to the further popularization and popularization of the market. SUMMARY

[0003] In view of the deficiencies of the prior art, the technical problem to be solved by the present application is to provide a six-piece 8M forward-looking optical system, which realizes the visual perception and identification function of driving while realizing 8MP imaging, so as to replace the forward-looking wide-angle camera and the forward-looking narrow-angle camera, realize a single lens to form a forward-looking camera module, greatly reduce the cost and improve the market popularity.

[0004] In order to solve the above technical problems, the technical scheme of the present application is as follows: a six-piece 8M forward-looking optical system, the optical system of the lens is composed of a first lens, a diaphragm, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens arranged in order from left to right along the light incident path, without considering the reverse curvature caused by the aspherical coefficient, the first lens is a meniscus concave negative lens, the object side is convex, and the image side is concave; the second lens is a double-convex positive lens, the object side is convex, and the image side is convex; the third lens is a double-concave negative lens, the object side is concave, and the image side is concave; the fourth lens is a meniscus convex positive lens, the object side is concave, and the image side is convex; the fifth lens is a double-convex positive lens, the object side is convex, and the image side is convex; the sixth lens is a meniscus concave negative lens, the object side is concave, and the image side is convex; the first lens, the second lens, the third lens, the fifth lens and the sixth lens are glass spherical lenses, and the fourth lens is a glass aspherical lens, wherein the second lens and the third lens, and the fifth lens and the sixth lens are cemented lens groups.

[0005] 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 and the sixth lens are f1, f2, f3, f4, f5 and f6 respectively, wherein f1, f2, f3, f4, f5 and f6 satisfy the following ratios: -2.0 < f1 / f < -1.0, 0.0 < f2 / f < 1.0, -2.0 < f3 / f < -1.0, 2.0 < f4 / f < 3.0, 1.0 < f5 / f < 2.0, and -2.0 < f6 / f < -1.0.

[0006] Preferably, the first lens satisfies the relationship: 1.7 ≤ N d ≤ 2.0, and V d ≤ 50.0; the second lens satisfies the relationship: 2.0 ≤ N d ≤ 2.3, and V d ≤ 50.0; the third lens satisfies the relationship: 1.7 ≤ N d ≤ 2.0, and V d ≤ 50.0; the fourth lens satisfies the relationship: 1.5 ≤ N d ≤ 1.8, and V d ≥ 50.0; the fifth lens satisfies the relationship: 1.5 ≤ N d ≤ 1.8, and V d ≥ 50.0; and the sixth lens satisfies the relationship: 1.7 ≤ N d ≤ 2.0, and V d ≤ 50.0; wherein N d is the refractive index, and V d is the Abbe number.

[0007] Preferably, the axial distance between each lens satisfies the following relationships: the air gap between the first lens and the diaphragm is 4.5-5.0 mm; the air gap between the diaphragm and the second lens is 0.0-0.5 mm; the second lens and the third lens are cemented lenses with an air gap of 0 mm; the air gap between the third lens and the fourth lens is 0.5-1.0 mm; the air gap between the fourth lens and the fifth lens is 0.1-0.5 mm; and the fifth lens and the sixth lens are cemented lenses with an air gap of 0 mm.

[0008] Preferably, the fourth lens is a non-spherical lens. The non-spherical curve equation is expressed as:

[0009]

[0010] wherein Z is the sagittal height of the non-spherical lens at a height of r along the optical axis; c is the paraxial curvature of the non-spherical lens; k is the conic constant; and α1, α2, α3, α4, α5, α6, α7 and α8 are high-order coefficients.

[0011] Preferably, the optical total length TTL of the optical system and the focal length f of the optical system satisfy: TTL / f≤7.0.

[0012] Preferably, the F number of the optical system is ≤1.8.

[0013] Preferably, the image height H of the optical system and the focal length f of the optical system satisfy: H / f≥1.0.

[0014] Preferably, the diaphragm is arranged between the first lens and the second lens, and the sixth lens is arranged with a filter on the image side, and the filter is selected from an equivalent glass flat plate.

[0015] An imaging method of a six-piece 8M forward-looking optical system is performed in the following steps: light rays are sequentially imaged on an imaging surface after passing through a first lens, a diaphragm, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens from left to right.

[0016] Compared with the prior art, the present application has the following beneficial effects:

[0017] 1. The lens has an imaging angle of more than 127 degrees for an object, and has the advantages of super-high 8M imaging clarity, large light aperture, low tolerance sensitivity and good high-low temperature stability, etc., and can more comprehensively monitor the scene outside the vehicle.

[0018] 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.

[0019] 3. The all-glass structure has high stability, can adapt to harsh environments, fully utilizes the advantages of aspherical lenses in correcting aberrations, meets the requirements of high-definition imaging, has smaller lens outer diameter and shorter optical total length, and ensures the miniaturization of the lens.

[0020] 4. The focus surface displacement can be well compensated at high and low temperatures, and the system has good adaptability to complex environments.

[0021] 5. The axial color difference, sagittal color difference and high-order color difference are corrected, and the imaging system can also have high imaging quality at a large angle.

[0022] The present application will be further described in detail below in combination with the drawings and specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0023] Fig. 1 The optical structure of the embodiment of the present application is shown in the figure;

[0024] Fig. 2 The full working waveband axial color difference graph of the embodiment of the present application is shown in the figure;

[0025] Fig. 3 The full working waveband field curvature distortion chart of the embodiment of the present application;

[0026] Fig. 4 The full working waveband field curvature distortion chart of the embodiment of the present application;

[0027] In the figure: STO - diaphragm; L1 - first lens; L2 - second lens; L3 - third lens; L4 - fourth lens; L5 - fifth lens; L6 - sixth lens; L7 - equivalent glass flat plate; L8 - equivalent glass flat plate; IMA - imaging plane. DETAILED DESCRIPTION

[0028] In order to make the above features and advantages of the present application more obvious and easy to understand, the following specific embodiments are described in detail below, and the drawings are described as follows.

[0029] As shown in Figs. 1-4 , a six-piece 8M front-view optical system is provided with a first lens, a diaphragm, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens in order from the object side to the image side. Among them, the first lens is a glass lens with negative focal power, which can adjust the large-angle light. The fourth lens is a glass aspheric surface, which can reduce the distortion of the optical system. The second lens and the third lens, and the fifth lens and the sixth lens are cemented lens groups. Reasonable lens matching makes the optical system realize six-piece, 8M, super wide angle, large aperture, day and night focus, low temperature drift design, and at the same time, the on-axis and off-axis aberrations are well corrected, and the imaging quality is good, as shown in Figs. 2 to 4 . The technical indicators realized by the optical system of the embodiment are as follows:

[0030] (1) focal length: 3.0≤EFFL≤4.0mm;

[0031] (2) aperture F≤1.8;

[0032] (3) field of view angle: 2w≥127°;

[0033] (4) working waveband: visible light waveband.

[0034] In order to realize the above design parameters, the specific design of the optical system of the embodiment is shown in the following table:

[0035]

[0036]

[0037] The aspheric coefficients of the aspheric lenses of the optical system of the embodiment are as follows:

[0038]

[0039] The optical system of the embodiment of the present application can meet the 8M imaging performance requirement of the six-piece lens while reducing the total length of the lens and the radial size of each lens by reasonably distributing the focal power, surface shape, central thickness of each lens and the axial distance between each lens.

[0040] The above description is only the 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 into equivalent embodiments with equivalent changes. However, any simple modification, equivalent change and modification of the above embodiments made without departing from the technical solution of the present application and according to the technical essence of the present application still falls within the protection scope of the technical solution of the present application.

Claims

1. A six-piece 8M forward looking optical system comprising an optical system characterized by: The lens of the optical system is composed of a first lens, a diaphragm, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens arranged in sequence from left to right along the light incident path, wherein, without considering the reverse bending caused by the aspherical surface coefficient, the first lens is a meniscus concave negative lens; the second lens is a biconvex positive lens; the third lens is a double concave negative lens; the fourth lens is a meniscus convex positive lens; the fifth lens is a biconvex positive lens; and the sixth lens is a meniscus concave negative lens; the first lens, the second lens, the third lens, the fifth lens and the sixth lens are glass spherical lenses, and the fourth lens is a glass aspherical lens, wherein the second lens and the third lens and the fifth lens and the sixth lens are cemented lens groups. The object side of the first lens is convex, and the image side is concave; the object side of the second lens is convex, and the image side is convex; the object side of the third lens is concave, and the image side is concave; the object side of the fourth lens is concave, and the image side is convex; the object side of the fifth lens is convex, and the image side is convex; and the object side of the sixth lens is concave, and the image side is convex. 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 and the sixth lens are f1, f2, f3, f4, f5 and f6 respectively, wherein f1, f2, f3, f4, f5 and f6 and f satisfy the following ratios: -2.0 < f1 / f < -1.0, 0.0 < f2 / f < 1.0, -2.0 < f3 / f < -1.0, 2.0 < f4 / f < 3.0, 1.0 < f5 / f < 2.0, and -2.0 < f6 / f < -1.

0.

2. A six-element 8M front-view optical system according to claim 1, characterized in that: The first lens satisfies the relationship: 1.7 ≤ N d ≤ 2.0, V d ≤ 50.0; the second lens satisfies the relationship: 2.0 ≤ N d ≤ 2.3, 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: 1.5 ≤ N d ≤ 1.8, V d ≥ 50.0; the sixth 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 six-element 8M front-view optical system of claim 1, wherein: The on-axis distance between each lens satisfies the following relationship: the air gap between the first lens and the diaphragm is 4.5-5.0 mm; the air gap between the diaphragm and the second lens is 0.0-0.5 mm; the second lens and the third lens are cemented lenses with an air gap of 0 mm; the air gap between the third lens and the fourth lens is 0.5-1.0 mm; the air gap between the fourth lens and the fifth lens is 0.1-0.5 mm; and the fifth lens and the sixth lens are cemented lenses with an air gap of 0 mm.

4. The six-element 8M front-view optical system of claim 1, wherein: The fourth lens is an aspherical lens, and the aspherical curve equation is expressed as: wherein Z is the off-axis 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 α1, α2, α3, α4, α5, α6, α7 and α8 are high-order coefficients.

5. The six-element 8M front-view 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 ≤ 7.

0.

6. A six-element 8M front-view optical system according to claim 1, characterized in that: The F number of the optical system is ≤1.

8.

7. The six-element 8M front-view 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.

8. An imaging method applied to the six-piece 8M front-view optical system of claim 1, characterized in that, The following steps are performed: light rays pass through the first lens, the diaphragm, the second lens, the third lens, the fourth lens, the fifth lens and the sixth lens in sequence from left to right, and then are imaged on the imaging plane.

Images