A 1.4mm wide-angle optical system and imaging method thereof

Abstract

The present invention relates to a 1.4mm wide-angle optical system, comprising a first lens, a second lens, an aperture, a third lens, a fourth lens and a fifth lens which are sequentially arranged from left to right along the incident light path of the light; wherein the first lens is a negative meniscus lens, the second lens is a positive meniscus lens, and the two constitute a front lens group with negative optical power, the concave surface of the first lens faces the aperture, and the concave surface of the second lens faces away from the aperture; the third lens is a biconvex positive lens, the fourth lens is a biconcave negative lens, and the fifth lens is a biconvex positive lens, and the three constitute a rear lens group with positive optical power. The design of the present invention has the characteristics of large field of view angle and large light flux; it adopts a multi-piece aspherical lens design scheme, with high overall reliability, low sensitivity of lens group assembly, high yield and low cost, which is conducive to large-scale production; the imaging quality is high, reaching the level of two million pixel high-definition camera.

Description

Technical Field

[0001] The invention relates to a 1.4mm wide-angle optical system and an imaging method thereof. Background Art

[0002] Car rearview cameras are widely used in car monitoring systems to provide drivers with car rearview images, reversing assistance and other functions. With the development of the automotive industry, higher requirements are placed on the performance of car rearview cameras. Common rearview cameras generally use a 5-6-piece all-glass lens structure. The lens is large and heavy, which cannot meet the requirements of miniaturization and has a high manufacturing cost. In addition, the aperture of common rearview lenses is small, resulting in insufficient light transmission at the edge of the large field of view, unclear edge imaging, and the overall imaging quality is affected.

[0003] In view of the shortcomings of the prior art, the present invention aims to provide a 1.4mm wide-angle optical system, which achieves the purpose of achieving 2 million high-definition image quality, miniaturization and cost reduction by adopting more aspherical lenses. Summary of the invention

[0004] The purpose of the present invention is to address the above deficiencies and provide a 1.4 mm wide-angle optical system with a simple structure and an imaging method thereof.

[0005] The technical solution of the present invention is a 1.4mm wide-angle optical system, comprising a first lens, a second lens, an aperture, a third lens, a fourth lens and a fifth lens which are sequentially arranged from left to right along the incident light path of the light;

[0006] The first lens is a negative meniscus lens, and the second lens is a positive meniscus lens, which together form a front lens group with negative optical power. The concave surface of the first lens faces the aperture, and the concave surface of the second lens faces away from the aperture.

[0007] The third lens is a double convex positive lens, the fourth lens is a double concave negative lens, and the fifth lens is a double convex positive lens. The three constitute a rear lens group with positive optical power.

[0008] Furthermore, the air gap between the first lens and the second lens is 1.65-1.70 mm, the air gap between the third lens and the fourth lens is 0.25-0.30 mm, the air gap between the fourth lens and the fifth lens is 0.10-0.15 mm, and the air gap between the front lens group and the rear lens group is 1.0-1.2 mm.

[0009] Furthermore, the focal length of the optical system composed of the front lens group and the rear lens group is f, and the focal lengths of the first lens, the second lens, the third lens, the fourth lens, and the fifth lens are f1, f2, f3, f4, and f5, respectively, wherein f1, f2, f3, f4, and f5 satisfy the following ratio with f:

[0010] -2.5<f1 / f<-2, 5.5<f2 / f<6, 1.5<f3 / f<1.8, -1.5<f4 / f<-0.5, 1<f5 / f<2

[0011] Furthermore, the first lens satisfies the relationship: N d ≥1.7, V d ≤50; the second lens satisfies the relationship: N d ≥1.6, V d ≤30; the third lens satisfies the relationship: N d ≥1.5, V d ≥55; the fourth lens satisfies the relationship: N d ≥1.6, V d ≤30; the fifth lens satisfies the relationship: N d ≥1.5, V d ≥55, where N d is the refractive index, V d is the Abbe constant.

[0012] Furthermore, the first lens is a spherical lens made of glass; the second lens, the third lens, the fourth lens, and the fifth lens are aspherical lenses, all made of plastic materials.

[0013] An imaging method of a 1.4mm wide-angle optical system is performed according to the following steps: light rays are imaged after passing through a first lens, a second lens, a third lens, a fourth lens, and a fifth lens from left to right in sequence.

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

[0015] 1. The 1G4P design structure is adopted. Compared with the all-glass design, it is not only simpler in structure, but also smaller in size and weight. The overall reliability of the system is high, and the assembly sensitivity is reduced, which increases the yield and reduces the cost, which is conducive to large-scale production.

[0016] 2. At the same time, it ensures a large field of view angle, a large aperture, sufficient light intake, and good edge imaging quality; through reasonable glass material matching and lens focal length distribution, the axial chromatic aberration and lateral chromatic aberration of the entire optical system are well corrected, and the reasonable surface design also enables the high-level aberrations of the entire optical system to be effectively corrected. At the same time, the incident angle of light on each mirror surface is small, and the overall imaging quality of the system is excellent. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention is further described below in conjunction with the accompanying drawings.

[0018] Figure 1 is a schematic diagram of the optical structure of an embodiment of the present invention;

[0019] Figure 2 is a visible light MTF curve diagram of an embodiment of the present invention;

[0020] Figure 3 is an axial chromatic aberration curve diagram of an embodiment of the present invention;

[0021] Figure 4 is a lateral chromatic aberration curve diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0022] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0023] like Figures 1 to 4 As shown, a 1.4 mm wide-angle optical system includes a first lens A1, a second lens A2, an aperture C, a third lens B1, a fourth lens B2 and a fifth lens B3 which are sequentially arranged from left to right along the incident light path of the light;

[0024] The first lens is a negative meniscus lens, and the second lens is a positive meniscus lens, which together form a front lens group with negative optical power. The concave surface of the first lens faces the aperture, and the concave surface of the second lens faces away from the aperture.

[0025] The third lens is a double convex positive lens, the fourth lens is a double concave negative lens, and the fifth lens is a double convex positive lens. The three constitute a rear lens group with positive optical power.

[0026] In this embodiment, the air gap between the first lens and the second lens is 1.65-1.70 mm, the air gap between the third lens and the fourth lens is 0.25-0.30 mm, the air gap between the fourth lens and the fifth lens is 0.10-0.15 mm, and the air gap between the front lens group and the rear lens group is 1.0-1.2 mm.

[0027] In this embodiment, an aperture is provided between the second lens and the third lens, the air gap between the second lens and the aperture is 1.05 mm, the air gap between the third lens and the aperture is 0.1 mm, and a filter 1 D1 and a filter 2 D2 are provided on the rear side of the fifth lens.

[0028] In this embodiment, the focal length of the optical system composed of the front lens group and the rear lens group is f, and the focal lengths of the first lens, the second lens, the third lens, the fourth lens, and the fifth lens are f1, f2, f3, f4, and f5, respectively, wherein f1, f2, f3, f4, and f5 satisfy the following ratio with f:

[0029] -2.5<f1 / f<-2, 5.5<f2 / f<6, 1.5<f3 / f<1.8, -1.5<f4 / f<-0.5, 1<f5 / f<2.

[0030] By reasonably distributing the focal power of the optical system formed by the present invention according to the above ratio, each lens is in a certain ratio relative to the focal length f of the system, so that the aberration of the optical system formed by the present invention in the wavelength range of 420 to 700 nm can be reasonably corrected and balanced.

[0031] In this embodiment, the first lens satisfies the relationship: N d ≥1.7, V d ≤50; the second lens satisfies the relationship: N d ≥1.6, V d ≤30; the third lens satisfies the relationship: N d ≥1.5, V d ≥55; the fourth lens satisfies the relationship: N d ≥1.6, V d ≤30; the fifth lens satisfies the relationship: N d ≥1.5, V d ≥55, where N d is the refractive index, V d is the Abbe constant.

[0032] In this embodiment, the first lens is a spherical lens made of glass; the second lens, the third lens, the fourth lens, and the fifth lens are aspherical lenses made of plastic.

[0033] An imaging method of a 1.4mm wide-angle optical system is performed according to the following steps: light rays are imaged after passing through a first lens, a second lens, a third lens, a fourth lens, and a fifth lens from left to right in sequence.

[0034] Example 1: The air gap between the first lens and the second lens is 1.67 mm, the air gap between the third lens and the fourth lens is 0.27 mm, the air gap between the fourth lens and the fifth lens is 0.12 mm, and the air gap between the front lens group and the rear lens group is 1.15 mm.

[0035] Table 1 shows the curvature radius R, thickness d, refractive index N of each lens of the optical lens of Example 1. d and the Abbe number V d .

[0036]

[0037] Table 1 Specific lens parameters

[0038] This embodiment uses five lenses as an example. By reasonably allocating the focal length, surface shape, center thickness of each lens, and axial spacing between lenses, the field of view of the lens is effectively expanded, the total length of the lens is shortened, and small distortion and high illumination of the lens are ensured; at the same time, various aberrations are corrected to improve the resolution and imaging quality of the lens. The surface shape Z of each aspherical surface is defined by the following formula:

[0039]

[0040] Among them, Z is the height of the aspheric surface from the vertex of the aspheric surface when the aspheric surface is at a height of h along the optical axis; c is the paraxial curvature of the aspheric surface, c = 1 / R (that is, the paraxial curvature c is the reciprocal of the curvature radius R in Table 1 above); k is the cone constant; A, B, C, D, and E are all high-order coefficients.

[0041] Table 2 shows the cone constant k and the high-order coefficients A, B, C, D, and E that can be used for each aspherical lens surface in this embodiment.

[0042]

[0043]

[0044] Table 2 Parameters of various aspherical lenses

[0045] In this embodiment, the technical indicators achieved by this optical system are as follows:

[0046] (1) Focal length: EFFL = 1.39 mm; (2) Aperture F = 2.0; (3) Field of view: 2w ≥ 155°; (4) Optical distortion: < -65%; (5) Imaging circle diameter greater than φ4.8; (6) Working band: 420 ~ 700 nm; (7) Total optical length TTL ≤ 11.5 mm, optical back focus BFL ≥ 2.1 mm; (8) This lens is suitable for 2 million pixel CCD or CMOS cameras.

[0047] In the embodiment of the present invention, the first lens has a large refractive index and optical focal length, ensuring that the system can collect light within a large field of view; the second lens adopts an aspherical lens, and the distortion of the optical system is effectively corrected by selecting a suitable surface shape; a typical front negative and rear positive structure is adopted, and the negative optical focal length of the front lens group corrects the positive optical focal length aberration of the rear lens group.

[0048] Four aspherical lenses correct all high-level aberrations and spherical aberrations. Through a reasonable distribution of refractive index and optical power ratio, the incident angle of light between the lenses of the front lens group and the lenses of the rear lens group is limited. A smaller incident angle of light can effectively reduce the image curvature of the optical system. In the rear lens group, the fourth lens with a medium refractive index and ultra-high dispersion effectively corrects the chromatic aberration and astigmatism of the imaging system. The fourth lens and the fifth lens also have the function of compensating for the high and low temperature characteristics of the system.

[0049] Through the optical system composed of the above lenses, the total length of the optical path is short, the lens size is small, the back focus is large, and it can be used with cameras of various different interfaces; at the same time, the system aperture is large and the imaging quality is excellent; among them, the second lens, the third lens, the fourth lens, and the fifth lens are plastic aspherical lenses with good image quality, low cost, high overall reliability of the lens group, and excellent cost performance.

[0050] Depend on Figure 2 It can be seen that the optical system has good MTF performance in the visible light band. The MTF value of the 0.8F field of view is greater than 0.4 at the spatial frequency of 80pl / mm, and the MTF value of the central field of view is greater than 0.5 at the spatial frequency of 160pl / mm, which can meet the resolution requirements of 2 million high-definition. Figure 3 and Figure 4 is the axial chromatic aberration curve and lateral chromatic aberration curve of the optical system. Figure 3 It can be seen that the maximum axial chromatic aberration of the optical system is 1.86 μm. Figure 4 It can be seen that the lateral chromatic aberration of the optical system is within the range of the Airy disk, and the lateral chromatic aberration is well corrected. In summary, it can be seen that the optical system has excellent imaging quality and fully meets the requirements of 2 million pixel photography.

[0051] The preferred embodiments listed above further illustrate the objectives, technical solutions and advantages of the present invention in detail. It should be understood that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A 1.4mm wide-angle optical system, characterized in that: The wide-angle optical system is composed of five lenses, including a first lens, a second lens, an aperture, a third lens, a fourth lens and a fifth lens, which are arranged in sequence from left to right along the incident light path of the light; The first lens is a negative meniscus lens, and the second lens is a positive meniscus lens, which together form a front lens group with negative optical power. The concave surface of the first lens faces the aperture, and the concave surface of the second lens faces away from the aperture. The third lens is a biconvex positive lens, the fourth lens is a biconcave negative lens, and the fifth lens is a biconvex positive lens. The three lenses constitute a rear lens group with positive optical power. The focal length of the optical system composed of the front lens group and the rear lens group is f, and the focal lengths of the first lens, the second lens, the third lens, the fourth lens, and the fifth lens are f1, f2, f3, f4, and f5 respectively, where f1, f2, f3, f4, and f5 satisfy the following ratio with f: -2.5<f1 / f<-2, 5.5<f2 / f<6, 1.5<f3 / f<1.8, -1.5<f4 / f<-0.5, 1<f5 / f<2; The air space between the first lens and the second lens is 1.65-1.70 mm, the air space between the third lens and the fourth lens is 0.25-0.30 mm, the air space between the fourth lens and the fifth lens is 0.10-0.15 mm, and the air space between the front lens group and the rear lens group is 1.0-1.2 mm.

2. The 1.4 mm wide-angle optical system according to claim 1, characterized in that: The first lens satisfies the relationship: N d ≥1.7, V d ≤50; the second lens satisfies the relationship: N d ≥1.6, V d ≤30; the third lens satisfies the relationship: N d ≥1.5, V d ≥55; the fourth lens satisfies the relationship: N d ≥1.6, V d ≤30; the fifth lens satisfies the relationship: N d ≥1.5, V d ≥55, where N d is the refractive index, V d is the Abbe constant.

3. The 1.4 mm wide-angle optical system according to claim 1, characterized in that: The first lens is a spherical lens made of glass; the second lens, the third lens, the fourth lens and the fifth lens are aspherical lenses all made of plastic materials.

4. An imaging method using the 1.4 mm wide-angle optical system as claimed in any one of claims 1 to 3, characterized in that: Proceed in the following steps: light rays pass through the first lens, the second lens, the third lens, the fourth lens, and the fifth lens from left to right to form an image.

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