A short-focus, small F-number lens

Abstract

The present invention discloses a short-focus, low-F-number lens, comprising a lens barrel and a photosensitive image surface. The photosensitive image surface is disposed on the image-side surface of the lens barrel. A light aperture is provided at one end of the object-side surface of the lens barrel. Lens 1, 2, 3, 4, and a filter are sequentially disposed within the lens barrel from the object-side surface to the photosensitive image surface. The focal length (EFL) from lens 1 to the photosensitive image surface is 3.687 mm, the field of view (FOV) is greater than 106′, and the F-number is 1.7. Compared with the prior art, the lens of the present invention features a large aperture, a large field of view, a short focus, and a high cost-effectiveness, addressing the shortcomings of the prior art and enriching the lens category.

Description

Technical Field

[0001] The present invention relates to the field of optical imaging lenses, and in particular to a short-focus, small F-number lens. Background Art

[0002] Security surveillance lenses are used in security systems and serve as the eyes of the security industry. Without them, we wouldn't be able to see the targets we monitor. They provide a true picture of the monitored object, extending the human eye's observation distance and spatial range. They can also replace manual surveillance in harsh environments, allowing users to see everything happening at the scene and record it with a video recorder. For safety reasons, the security industry is gaining increasing attention. Furthermore, with the advancement and development of security technology, the requirements for security lenses are becoming increasingly stringent, requiring them to have a wide aperture, a short focal length, a wide field of view, and a low price. Existing security lenses have small apertures, resulting in unclear images, and long focal lengths, making it difficult to achieve these requirements simultaneously. Summary of the Invention

[0003] The present invention aims to provide a short-throw, small F-number lens. It features a large aperture, wide field of view, short focus, and high cost-effectiveness, thus overcoming the shortcomings of existing technologies and enriching the category of security lenses.

[0004] To achieve the above object, the present invention is implemented according to the following technical solutions:

[0005] The present invention includes a lens barrel and a photosensitive element image surface, wherein the photosensitive element image surface is arranged on the image side of the lens barrel, and a light hole is provided at one end of the object side of the lens barrel. Lens 1, lens 2, lens 3, lens 4, and a filter are sequentially arranged in the lens barrel from the object side to the photosensitive element image surface, wherein the central axis position of the object side of the lens 1 is convex, and the central axis position of the image side is concave, the central axis position of the object side of the lens 2 is convex, and the central axis position of the image side is convex, the central axis position of the object side of the lens 3 is convex, and the central axis position of the image side is convex, and the central axis position of the object side of the lens 4 is concave, and the central axis position of the image side is concave;

[0006] The focal length EFL from the lens 1 to the image plane of the photosensitive element is 3.687 mm, the field of view angle FOV is greater than 106°, and the F number is 1.7.

[0007] A spacer ring 1 is provided between the lens 1 and the lens 2, a spacer ring 2 is provided between the lens 2 and the lens 3, a light shielding sheet is provided between the lens 3 and the lens 4, and light holes are provided in the middle of the spacer ring 1, the spacer ring 2 and the light shielding sheet.

[0008] Air gaps are provided between the lens one, lens two, lens three and lens four. The air gap between lens one and lens two is AIR01, AIR01=5.3509mm; the air gap between lens two and lens three is AIR02, AIR02=1.7709mm; the air gap between lens three and lens four is AIR03, AIR03=0.1mm.

[0009] A protective glass is provided between the filter and the image plane of the photosensitive element.

[0010] The first lens is an aspherical lens with a refractive index nd=1.535 and an Abbe number vd=56.1; an outer diameter=Φ12.0mm, a center thickness=1.0mm, and an edge thickness=3.06mm; the object side curvature radius is 30.000mm, the aspherical diameter is Φ9.44mm, and the image side curvature radius is 2.6094mm, and the aspherical diameter is Φ5.930mm.

[0011] The second lens is a standard spherical lens with a refractive index nd=1.603, an Abbe number vd=60.63; an outer diameter size=Φ8.6mm, a center thickness size=4.60mm; a curvature radius of the object side is 9.9319mm, and a curvature radius of the image side is -9.9319mm.

[0012] The third lens is an aspherical lens with a refractive index nd = 1.535 and an Abbe number vd = 56.1; the outer diameter is Φ7.60 mm, the middle thickness is 2.3791 mm, the edge thickness is 1.16 mm, the object side curvature radius is 3.8843 mm, the aspherical diameter is Φ5.48 mm, the image side curvature radius is -4.2548 mm, and the aspherical diameter is Φ5.34 mm.

[0013] The lens four is an aspherical lens with a refractive index nd = 1.64, an Abbe number vd = 23.5, an outer diameter = Φ7.40mm, a middle thickness = 0.7048mm, an edge thickness = 1.74mm, a curvature radius of the object side of -4.1441mm, an aspherical diameter of Φ5.21mm, a curvature radius of the image side of 20.000mm, and an aspherical diameter of Φ4.63mm.

[0014] Preferably, the lens 1, lens 3 and lens 4 are all made of plastic. The filter is made of glass, with a refractive index nd=1.517, an Abbe number vd=64.2 and a thickness of 0.3 mm. The lens 2 (3) is made of glass.

[0015] The beneficial effects of the present invention are:

[0016] The present invention is a short-focus, small F-number lens. Compared with the existing technology, the lens of the present invention has the characteristics of large aperture, large field of view, short focus and high cost performance, which solves the shortcomings of the existing technology and enriches the category of lenses. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic diagram of the optical path of the present invention;

[0018] Figure 2 It is a schematic cross-sectional structure diagram of the present invention;

[0019] Figure 3 is a cross-sectional view of a lens of the present invention;

[0020] Figure 4 is a second cross-sectional view of the lens of the present invention;

[0021] Figure 5 is a three-section view of the lens of the present invention;

[0022] Figure 6 1 is a four-section view of the lens of the present invention;

[0023] Figure 7 is the 110LP / MM diffraction MTF diagram of the present invention;

[0024] Figure 8 is a field curvature distortion diagram of the present invention;

[0025] Figure 9 This is an axial aberration diagram of the present invention. DETAILED DESCRIPTION

[0026] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. The exemplary embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0027] First embodiment:

[0028] like Figure 1 As shown: The present invention includes a lens barrel 8 and a photosensitive element image surface 11. The photosensitive element image surface 11 is arranged on the image side of the lens barrel 8. A light hole is provided at one end of the object side of the lens barrel 8 for controlling the amount of light passing through, and a screw thread is provided on the outer ring of the lens barrel for connection. Lens 1 1, lens 2 3, lens 3 5, lens 4 7, and filter 9 are sequentially provided in the lens barrel 8 from the object side to the photosensitive element image surface 11. The object side center axis position of lens 1 1 is convex, and the image side center axis position is concave. The object side center axis position of lens 2 3 is convex, and the image side center axis position is convex. The object side center axis position of lens 3 5 is convex, and the image side center axis position is convex. The object side center axis position of lens 4 7 is concave, and the image side center axis position is concave.

[0029] The focal length EFL from the lens 1 to the image plane 11 of the photosensitive element is 3.687 mm, the field of view angle FOV is greater than 106°, and the F number is 1.7.

[0030] A spacer ring 2 is provided between the lens 1 and the lens 2 3, a spacer ring 2 4 is provided between the lens 2 3 and the lens 3 5, a light shielding plate 6 is provided between the lens 3 5 and the lens 4 7, and light holes are provided in the middle of the spacer ring 2, the spacer ring 2 4 and the light shielding plate 6.

[0031] like Figure 2 As shown in the figure, the center line indicated by letter A is the optical axis of the lens of the present invention, and the position indicated by letter B is the glue dispensing groove of the lens, where all the components in the lens barrel are glued and packaged. Figure 2 At the position indicated by the letter C, a spacer groove is provided to allow the lens 1 (1) to press the spacer 1 (2) to prevent the lens barrel (8) from pressing against the lens 1 (1) and becoming loose. A light-through hole is provided in the middle of the spacer 1 (2), and its minimum light-through hole is the aperture stop, and its diameter is about Φ4.6mm. Spacer 1 (2) and spacer 2 (4) are provided between the lens 1 (1) and the lens 2 (3), and between the lens 2 (3) and the lens 3 (5). Together with the inner wall of the lens barrel (8), they support and fix the lenses to prevent the lenses from being eccentric and tilted. A light-shielding plate (6) is provided between the lens 3 (5) and the lens 4 (7), and a light-through hole is provided in the middle of the light-shielding plate, and the surface of the light-shielding plate is treated with a glare-removing treatment. Its main function is to constrain light and control the generation of stray light.

[0032] Air gaps are provided between the lens 1, lens 2, lens 3, lens 3, and lens 4, 7. The air gap between lens 1 and lens 2, 3, is AIR01, AIR01 = 5.3509 mm; the air gap between lens 2, 3, and lens 3, 5, is AIR02, AIR02 = 1.7709 mm; and the air gap between lens 3, 5, and lens 4, 7, is AIR03, AIR03 = 0.1 mm.

[0033] A protective glass 10 is provided between the filter 9 and the image plane 11 of the photosensitive element.

[0034] The lens 1 is an aspherical lens with a refractive index nd=1.535 and an Abbe number vd=56.1; the outer diameter dimension D1=Φ12.0mm, the center thickness dimension CT1=1.0mm, and the edge thickness dimension ET1=3.06mm; the object side curvature radius is 30.000mm, the aspherical diameter is Φ9.44mm, and the image side curvature radius is 2.6094mm, and the aspherical diameter is Φ5.930mm.

[0035] Lens 2 (3) is a standard spherical lens with a refractive index of nd = 1.603 and an Abbe number of vd = 60.63. Its outer diameter D2 is Φ8.6mm, and its median thickness CT2 is 4.60mm. The object-side curvature radius is 9.9319mm, and the image-side curvature radius is -9.9319mm. The curvature radii of the R1 and R2 surfaces are equal, eliminating the need to distinguish between different directions, thus ensuring a foolproof design.

[0036] The lens three 5 is an aspherical lens with a refractive index nd=1.535 and an Abbe number vd=56.1; the outer diameter dimension D3=Φ7.60mm, the center thickness dimension CT3=2.3791mm, the edge thickness dimension ET3=1.16mm, the object side curvature radius is 3.8843mm, the aspherical diameter is Φ5.48mm, the image side curvature radius is -4.2548mm, and the aspherical diameter is Φ5.34mm.

[0037] The lens 24 7 is an aspherical lens with a refractive index nd=1.64, an Abbe number vd=23.5, an outer diameter D4=Φ7.40mm, a center thickness CT4=0.7048mm, an edge thickness ET4=1.74mm, an object side curvature radius of -4.1441mm, an aspherical diameter of Φ5.21mm, an image side curvature radius of 20.000mm, and an aspherical diameter of Φ4.63mm.

[0038] Preferably, the lens 1, lens 3, and lens 4 are all made of plastic. The filter 9 is made of glass with a refractive index of nd = 1.517, an Abbe number vd = 64.2, and a thickness of 0.3 mm. The lens 2 is also made of glass.

[0039] Each lens is composed of two surfaces: the surface closest to the object side is called R1, and the surface closest to the image side is called R2. The distance between the two vertices of the lens surface is called the center thickness, and the distance between the two large flat surfaces at the edge of the lens is called the edge thickness. FOV refers to the field of view of the lens, which is the range that the lens can capture. EFL refers to the ultimate focal length of the lens. The lens operates in the visible light band, with a dominant wavelength of 555 nanometers.

[0040] The lens 1, lens 3, and lens 4 adopt an aspheric surface type, and the aspheric surface calculation formula is as follows:

[0041]

[0042] In the formula, C refers to the curvature of the lens surface, which is the reciprocal of the curvature radius (R), that is, C = 1 / R, K is the cone coefficient, r is the distance between the lens surface and the optical axis, a4, a6, a8, a10... are the aspheric higher-order coefficients, and SAG is the position at a height of r along the optical axis with the surface vertex as the reference point.

[0043] The imaging lens has a particularly small F number of 1.6. The smaller the F number, the larger the aperture, which allows for a particularly large amount of light to enter and produces clearer images. The lens has a short effective focal length (EFL) and a relatively large field of view (FOV), with EFL = 3.687 mm and FOV > 106°, allowing it to capture a wider space. The lens has a large image circle and can match large-sized photosensitive chips such as 1 / 2.7 inches and 1 / 2.9 inches. The imaging lens adopts a four-piece structure with a relatively small number of pieces, and three of the pieces are injection-molded using plastic molds, which allows for mass production. The production efficiency is higher than that of traditional glass lenses, so the cost is lower than that of similar lenses, making it highly cost-effective.

[0044] The following is a first embodiment of the present invention:

[0045]

[0046] The following are the conic coefficients and higher-order coefficients of the aspherical lens of the first embodiment:

[0047]

[0048] like Figure 7 As shown in the 110LP / MM diffraction MTF diagram, except for the slightly lower MTF in the T direction at the maximum image height, the other MTF values are all greater than 0.45. Figure 8 As shown in the field curvature distortion diagram, the field curvature is controlled within ±0.1mm. The maximum field angle shown in the lower left corner is 56.653 degrees, which is half the field of view. The actual full field angle is 56.653*2=113.306 degrees. Figure 9 As shown in the axial aberration diagram, the curve is controlled within ±0.05mm, indicating that the spherical aberration of this optical system is particularly small.

[0049] The imaging lens of the present invention has the following characteristics:

[0050] a. The F number of the lens is very small, F Number = 1.6. The smaller the F number, the larger the aperture, which allows a particularly large amount of light to enter and produces a clear image;

[0051] b. The focal length (EFL) of the lens is short and the field of view (FOV) is relatively large. EFL = 3.687mm, FOV > 106°, which can capture a wider space.

[0052] c. The image circle of the lens is large, with an image circle diameter of 7.0mm, which can match large-sized photosensitive chips such as 1 / 2.7 inches and 1 / 2.9 inches;

[0053] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. Any technical variations made according to the technical solution of the present invention fall within the protection scope of the present invention.

Claims

1. A short-focus, small F-number lens, comprising a lens barrel (8) and a photosensitive element image surface (11), wherein the photosensitive element image surface (11) is arranged on the image side of the lens barrel (8), and a light hole is provided at one end of the object side of the lens barrel (8), characterized in that: The lens barrel (8) is provided with lens one (1), lens two (3), lens three (5), lens four (7), and filter (9) in sequence from the object side to the image side of the photosensitive element (11). The center axis position of the object side of the lens one (1) is convex, and the center axis position of the image side is concave. The center axis position of the object side of the lens two (3) is convex, and the center axis position of the image side is convex. The center axis position of the object side of the lens three (5) is convex, and the center axis position of the image side is convex. The center axis position of the object side of the lens four (7) is concave, and the center axis position of the image side is concave. The number of lenses with refractive power is four. The focal length EFL from the lens 1 (1) to the image plane (11) of the photosensitive element is 3.687 mm, the field of view FOV>106°, and the F number is 1.7; Air gaps are provided between the lens 1 (1), the lens 2 (3), the lens 3 (5) and the lens 4 (7). The air gap between the lens 1 (1) and the lens 2 (3) is AIR01, AIR01 = 5.3509 mm; the air gap between the lens 2 (3) and the lens 3 (5) is AIR02, AIR02 = 1.7709 mm; the air gap between the lens 3 (5) and the lens 4 (7) is AIR03, AIR03 = 0.1 mm; The lens (1) has a refractive index nd = 1.535, a center thickness (CT1) = 1.0 mm, an object side curvature radius of 30.000 mm, and an image side curvature radius of 2.6094 mm; The refractive index of the lens 2 (3) is nd=1.603, the thickness (CT2) is 4.60mm; the object side curvature radius is 9.9319mm, and the image side curvature radius is -9.9319mm; The refractive index of the lens three (5) is nd = 1.535, the medium thickness size (CT3) is 2.3791mm, the object side curvature radius is 3.8843mm, and the image side curvature radius is -4.2548mm; The refractive index of the lens four (7) is nd=1.64, the medium thickness size (CT4) is 0.7048mm, the object side curvature radius is -4.1441mm, and the image side curvature radius is 20.000mm.

2. The short-focus, small F-number lens according to claim 1, wherein: A spacer ring 1 (2) is provided between the lens 1 (1) and the lens 2 (3), a spacer ring 2 (4) is provided between the lens 2 (3) and the lens 3 (5), a light shielding sheet (6) is provided between the lens 3 (5) and the lens 4 (7), and light holes are provided in the middle of the spacer ring 1 (2), the spacer ring 2 (4) and the light shielding sheet (6).

3. The short-focus, small F-number lens according to claim 1, wherein: A protective glass (10) is provided between the filter (9) and the image plane (11) of the photosensitive element.

4. The short-focus, small F-number lens according to claim 1 or 2, wherein: The lens 1 (1) is an aspherical lens with an Abbe number vd=56.1; an outer diameter size (D1)=Φ12.0mm, an edge thickness size (ET1)=3.06mm; an aspherical diameter is Φ9.44mm, and an aspherical diameter is Φ5.930mm.

5. The short-focus, small F-number lens according to claim 1 or 2, wherein: The second lens (3) is a standard spherical lens with an Abbe number vd = 60.63 and an outer diameter (D2) = Φ8.6mm.

6. The short-focus, small F-number lens according to claim 1 or 2, wherein: The lens three (5) is an aspherical lens with an Abbe number vd=56.1; an outer diameter size (D3)=Φ7.60mm, an edge thickness size (ET3)=1.16mm, an aspherical diameter of Φ5.48mm, and an aspherical diameter of Φ5.34mm.

7. The short-focus, small F-number lens according to claim 1 or 2, wherein: The lens four (7) is an aspherical lens with an Abbe number vd=23.5, an outer diameter size (D4)=Φ7.40mm, an edge thickness size (ET4)=1.74mm, an aspherical diameter of Φ5.21mm, and an aspherical diameter of Φ4.63mm.

8. The short-focus, small F-number lens according to claim 1 or 2, wherein: The lens one (1), lens three (5) and lens four (7) are all made of plastic.

9. The short-focus, small F-number lens according to claim 1, wherein: The filter (9) is made of glass, with a refractive index nd=1.517, an Abbe number vd=64.2, and a thickness of 0.3 mm; the second lens (3) is made of glass.

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