A day and night confocal 2 million pixel wide-angle optical lens

Abstract

The present invention relates to a day and night confocal 2 million pixel wide-angle optical lens, wherein the lens comprises a first lens element, a second lens element, an aperture, a third lens element, a fourth lens element and a filter in sequence from the object side to the image side, and is characterized in that: the first lens element is a concave-convex aspheric plastic lens with negative optical power, the second lens element is a concave-convex aspheric plastic lens with positive optical power, the third lens element is a biconvex aspheric plastic lens with positive optical power, and the fourth lens element is a concave-convex aspheric plastic lens with negative optical power.

Description

Technical Field

[0001] The present invention relates to the field of optical imaging technology, specifically to a day and night confocal 2 million pixel wide-angle lens, which is mainly used in smart home monitoring, video doorbells, etc., and the present invention is compatible with multiple types of chips and can also be used for other monitoring applications. Background Art

[0002] With the rapid development of Internet of Things technology, smart life has gradually entered thousands of households; the research report "Smart Home Surveillance Camera Market Analysis and Forecast" recently released by market research organization Strategy Analytics pointed out that by 2023, global consumers' spending on smart home surveillance cameras will exceed US$9.7 billion; among them, video doorbells will be the fastest growing market segment, with a scale of more than US$500 million in 2018 and a market size of US$1.4 billion by 2023.

[0003] In order to meet the needs of built-in video doorbells, the market trend is to miniaturize the lens and improve the image quality. In addition, due to the temperature difference between day and night and throughout the year and long working hours, the reliability of the lens is required to be very high. The most important point is the high cost performance of the lens product. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a 2-megapixel wide-angle lens with day and night confocality, which achieves the requirements of 2-megapixel high definition, large field of view, day and night confocality on the basis of miniaturization of the lens volume, and has a wide range of applications.

[0005] The objective of the present invention is achieved through the following technical solutions: a day and night confocal 2 million pixel wide-angle optical lens, the lens comprises a first lens element, a second lens element, an aperture, a third lens element, a fourth lens element and a filter in sequence from the object side to the image side, the first lens element is a concave-convex aspheric plastic lens with negative optical power, the second lens element is a concave-convex aspheric plastic lens with positive optical power, the third lens element is a biconvex aspheric plastic lens with positive optical power, and the fourth lens element is a concave-convex aspheric plastic lens with negative optical power.

[0006] Preferably, the surface of the first lens element is coated with ultra-particle hardening and anti-reflection film; the surface of the fourth lens element is coated with ultra-particle hardening and anti-reflection film.

[0007] Preferably, the first lens element satisfies: 1.52≤Nd 1 ≤1.56; 55.7≤Vd 1 ≤56.3.

[0008] Where Nd is the refractive index and Vd is the Abbe coefficient.

[0009] In design, optical materials with ND and VD within this range can meet the requirements of the optical system. Preferably, the second lens element satisfies: 1.52≤Nd 2 ≤1.56; 55.7≤Vd 2 ≤56.3.

[0010] Preferably, the third lens element satisfies: 1.52≤Nd 3 ≤1.56; 55.7≤Vd 3 ≤56.3.

[0011] Preferably, the fourth lens element satisfies: 1.66≤Nd 4 ≤1.68;23.2≤Vd 4 ≤23.8.

[0012] Preferably, the lens meets the following requirements: EFL (focal length) = 2.6 ± 5% mm; TTL (total optical length) = 9.15 ± 0.2 mm; F / NO (aperture) = 2.0 ± 5%; FOV (field of view angle) = 120 ± 5°; image height ≥ 4.7 mm; CRA (chief ray angle) < 21.2°; brightness ≥ 50%; TV distortion ≤ 25%; day and night confocal defocus ≤ 0.005 mm. Through the optimized optical system design, the above optical specifications are output to meet the lens imaging requirements; the day and night confocal 2 megapixel wide-angle optical lens can meet the compatibility of OV2732 or SP140A or GC1054 or SC1042 or other chips.

[0013] Beneficial effects of the present invention: 1. The present invention adopts 4 plastic aspheric lenses, which greatly reduces the volume of the lens and fully meets the needs of miniaturization of practical application products; 2. The lenses are made of plastic and are all formed by molds, with a short production cycle, high efficiency and low cost; 3. The present invention adopts aspheric lenses and large aperture design, with high image quality, small chromatic aberration and good picture brightness; 4. The day and night confocal defocus of the present invention is ≤0.005mm, which can ensure normal imaging in day and night environments; 5. The distortion of the scheme of the present invention is ≤25%, thereby improving the realism of the picture; 6. By coating the first and fourth lens surfaces with ultra-fine particle hardening and anti-reflection films, the lens has better light transmittance, less light energy loss, and can effectively prevent the lens surface from being scratched and fine scratches; the coating materials are silicon dioxide and titanium pentoxide, and the film thickness is about 0.005mm; it can enhance the light transmittance of the lens element, reduce light energy loss, and effectively protect the optical lens from scratches and resist the influence of harsh environmental changes during use, 7. The lens can fully realize normal imaging in the working temperature range of -20℃~60℃, and has a wide applicable temperature range. 8. The structural tolerance of the lens of the present invention is loose, with a production yield of 95%. By analyzing, controlling and optimizing the stray light of the lens, the actual imaging effect of the lens is more excellent. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 : is a schematic diagram of the specific structure of the lens of the present invention;

[0015] Figure 2 : is the MTF resolution curve diagram of the lens of the present invention;

[0016] Figure 3 : It is the field curvature and distortion curve diagram of the invented lens;

[0017] Figure 4 : is a point diagram of the lens of the present invention;

[0018] Figure 5 : is a relative brightness curve diagram of the lens of the present invention;

[0019] Figure 6 : is a chromatic aberration diagram of the lens of the present invention;

[0020] Figure 7 : is a CRA curve diagram of the lens of the present invention;

[0021] Figure 8 : Contrast and difference of day and night confocal defocus curves (temperature: 20℃ day and night confocal defocus: 0.0141mm);

[0022] Fig. 9 : Comparison and difference of defocus curves at -20℃ and 60℃ (temperature: 20℃ defocus: 0mm);

[0023] Fig.10 : Comparison and difference of defocus curves at -20℃ and 60℃ (temperature: -20℃ defocus amount: 0.0384mm);

[0024] Fig.11 : Comparison and difference of defocus curves at -20℃ and 60℃ (temperature: -60℃ defocus amount: 0.0435mm);

[0025] Among them: a first lens element 1, a second lens element 2, an aperture 3, a third lens element 4, a fourth lens element 5, and a filter 6. DETAILED DESCRIPTION

[0026] The present invention is further described below with reference to embodiments, but the scope of protection claimed by the present invention is not limited to the scope described in the embodiments. Example 1

[0027] A day and night confocal 2 million pixel wide-angle optical lens such as Figure 1 As shown, the optical lens comprises a first lens element 1, a second lens element 2, an aperture 3, a third lens element 4, a fourth lens element 5 and a filter 6 from the object side to the image side.

[0028] Preferably, the second lens element 2 is a concave-convex aspheric plastic lens with positive power, the third lens element 4 is a biconvex aspheric plastic lens with positive power, and the fourth lens element 5 is a concave-convex aspheric plastic lens with negative power.

[0029] The surface of the first lens element 1 is coated with ultra-fine particles for hardening and anti-reflection film; the surface of the fourth lens element 5 is coated with ultra-fine particles for hardening and anti-reflection film.

[0030] The film thickness is 0.003-0.007 mm.

[0031] Preferably, Nd 1 =1.553; Vd 1 =55.956;Nd 2 =1.538; Vd 2 =55.973; Nd 3 =1.546; Vd 3 =55.975;Nd 4 =1.67; Vd 4 =23.618.

[0032] Preferably, the lens meets the following requirements: EFL=2.6±5%mm; TTL=9.15±0.2mm; F / NO=2.0±5%; FOV=120±5°; image height≥4.7mm; CRA<21.2°; brightness≥50%; TV distortion≤25%; day and night confocal defocus amount≤0.005mm.

[0033] The day and night confocal 2 million pixel wide-angle optical lens can be compatible with OV2732 or SP140A or GC1054 or SC1042 or other chips.

[0034] Through the above configuration, a large field of view, large aperture, and high imaging clarity can be achieved, which is particularly suitable for home smart monitoring, video doorbells, etc.

[0035] In addition, the present embodiment reasonably controls the value of the optical focal length (through the optimized design of the optical system to achieve the characteristics of the lens), which on the one hand effectively controls the height of the incident light to reduce the height of the optical system and the outer diameter of the lens, and on the other hand can reduce the incident angle of the main light to improve the relative brightness of the optical system; the first and fourth lens elements of the present embodiment are coated with ultra-fine particle hardening and anti-reflection films on the surface, which can effectively protect the optical lens from scratches during use and resist the influence of harsh environmental changes, increase the light transmittance of the lens, and reduce light energy loss; the present embodiment uses an aspherical lens made of plastic material, which greatly reduces the height of the optical system, and the temperature resistance and stability can also be ensured.

[0036] Figure 2-Figure 11 An effective optical performance curve diagram is provided for this embodiment. It can be seen from the diagram that the lens of this embodiment has optimized various aberrations to the best and can reach a practical level.

Claims

1. A four-element day and night confocal 2-megapixel wide-angle optical lens, characterized in that: The lens comprises, from the object side to the image side, a first lens element (1), a second lens element (2), an aperture (3), a third lens element (4), a fourth lens element (5) and a filter (6); the first lens element (1) is a concave-convex aspheric plastic lens with negative focal length, the second lens element (2) is a concave-convex aspheric plastic lens with positive focal length, the third lens element (4) is a biconvex aspheric plastic lens with positive focal length, and the fourth lens element (5) is a concave-convex aspheric plastic lens with negative focal length; the first lens element (1) has a convex surface facing the object side and a concave surface facing the image side, the second lens element (2) has a concave surface facing the object side and a convex surface facing the image side, and the fourth lens element (5) has a concave surface facing the object side and a convex surface facing the image side; the lens satisfies the following requirements: EFL=2.6±5%mm; TTL=9.15±0.2mm; F / NO=2.0±5%; FOV=120±5°; image height≥4.7mm; CRA<21.2°; brightness ≥50%; TV distortion ≤25%; day and night confocal defocus ≤0.005mm.

2. The four-element day and night confocal 2 megapixel wide-angle optical lens according to claim 1, characterized in that: The surface of the first lens element (1) is coated with ultra-fine particles for hardening and anti-reflection film; the surface of the fourth lens element (5) is coated with ultra-fine particles for hardening and anti-reflection film.

3. The four-piece day and night confocal 2 megapixel wide-angle optical lens according to claim 2, characterized in that: The film thickness is 0.003-0.007 mm.

4. The four-element day and night confocal 2 megapixel wide-angle optical lens according to claim 1, characterized in that: The first lens element (1) satisfies: 1.52≤Nd1≤1.56; 55.7≤Vd1≤56.

3.

5. The four-element day and night confocal 2 megapixel wide-angle optical lens according to claim 1, characterized in that: The second lens element (2) satisfies: 1.52≤Nd2≤1.56; 55.7≤Vd2≤56.

3.

6. The four-element day and night confocal 2 megapixel wide-angle optical lens according to claim 1, characterized in that: The third lens element (4) satisfies: 1.52≤Nd3≤1.56; 55.7≤Vd3≤56.

3.

7. The four-element day and night confocal 2 megapixel wide-angle optical lens according to claim 1, characterized in that: The fourth lens element (5) satisfies: 1.66≤Nd4≤1.68; 23.2≤Vd4≤23.

8.

8. A four-element day and night confocal 2 megapixel wide-angle optical lens as claimed in any one of claims 1 to 7, characterized in that: Compatible with chip OV2732 or SP140A or GC1054 or SC1042.

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