A 3mm large aperture day and night confocal lens and imaging method thereof

Abstract

The present invention relates to a 3mm large aperture day and night confocal lens and an imaging method thereof, wherein the optical system of the lens comprises a front lens group, an aperture and a rear lens group arranged in sequence along the optical path direction; the front lens group is provided with a meniscus negative lens L1, a double concave negative lens L2 and a double convex positive lens L3 in sequence along the incident optical path, and the rear lens group is provided with a meniscus positive lens L4, a cemented group formed by closely connecting a double convex positive lens L5 and a meniscus negative lens L6, and a double convex positive lens L7 in sequence along the incident optical path. The 3mm large aperture day and night confocal lens of the present invention can better correct purple fringing chromatic aberration, has excellent imaging quality, realizes a simple structure and a function of day and night use, fully meets the requirements of eight million pixel photography, and is suitable for 4K pixel CCD or CMOS cameras.

Description

Technical Field

[0001] The invention relates to a 3mm large-aperture day-night confocal lens and an imaging method thereof. Background Art

[0002] Modern society has higher and higher requirements for security precautions. Security optical lenses are also developing from standard definition to high definition, and from single visible light imaging to visible light and infrared confocal imaging. Megapixel, day and night dual-use zoom security lenses will become the main requirements of the future market. Common day and night dual-use lenses achieve confocality by switching filters of different thicknesses. Summary of the invention

[0003] In view of this, the purpose of the present invention is to provide a 3mm large aperture day and night confocal lens with excellent imaging quality and an imaging method thereof, which realizes a simple structure and day and night dual-use functions and fully meets the requirements of 8 million pixel photography.

[0004] The present invention is implemented by the following scheme: a 3mm large aperture day and night confocal lens, the optical system of the lens includes a front lens group, an aperture and a rear lens group arranged in sequence along the light path direction; the front lens group is provided with a meniscus negative lens L1, a double concave negative lens L2 and a double convex positive lens L3 in sequence along the incident light path, and the rear lens group is provided with a meniscus positive lens L4, a cemented group formed by closely connecting a double convex positive lens L5 and a meniscus negative lens L6, and a double convex positive lens L7 in sequence along the incident light path.

[0005] Furthermore, all lenses in the front lens group and the rear lens group are made of glass and are spherical lenses, and a protective glass is provided on the rear side of the double convex positive lens L7.

[0006] Furthermore, the air gap between the meniscus negative lens L1 and the double concave negative lens L2 is 2.1-2.5 mm, the air gap between the double concave negative lens L2 and the double convex positive lens L3 is 0.9-1.3 mm, the air gap between the double convex positive lens L3 and the aperture is 1.7-1.9 mm, the air gap between the aperture and the meniscus positive lens L4 is 0-1 mm, the air gap between the meniscus positive lens L4 and the cemented group is 0-1 mm, and the air gap between the cemented group and the seventh lens L7 is 0-1.5 mm.

[0007] Furthermore, the focal lengths of the meniscus negative lens L1, the biconcave negative lens L2, the biconvex positive lens L3, the meniscus positive lens L4, the biconvex positive lens L5, the meniscus negative lens L6, and the biconvex positive lens L7 are f1, f2, f3, f4, f5, f6, and f7, respectively. The focal length of the lens optical system is f, wherein f1, f2, f3, f4, f5, f6, and f7 satisfy the following ratio with f: -2.3 <f1 / f<-2.0,-2.5<f2 / f<-2.3,1.9<f3 / f<2.2,5.2<f4 / f<6.3,1.6<f5 / f<1.8,-3.5<f6 / f<-3.0,4.0<f7 / f<4.1。

[0008] Furthermore, the refractive index N of the meniscus negative lens L1 is d and the Abbe constant V d Satisfy the relationship: N d ≥1.5, V d ≥50; the refractive index N of the biconcave negative lens L2 d and the Abbe constant V d Satisfy the relationship: N d ≥1.5, V d ≥50; the refractive index N of the biconvex positive lens L3 d and the Abbe constant V d Satisfy the relationship: N d ≥1.8, V d ≤40; the refractive index N of the meniscus positive lens L4 d and the Abbe constant V d Satisfy the relationship: N d ≥1.5, V d ≥50; the refractive index N of the biconvex positive lens L5 d and the Abbe constant V d Satisfy the relationship: N d ≥1.5, V d ≥50; the refractive index N of the meniscus negative lens L6 d and the Abbe constant V d Satisfy the relationship: N d ≥1.8, V d ≤40; the refractive index N of the biconvex positive lens L7 d and the Abbe constant V d Satisfy the relationship: N d ≥1.5, V d ≤50.

[0009] Furthermore, the total optical length TTL of the optical system and the focal length f of the optical system satisfy: TTL / f≤13.

[0010] Another technical solution of the present invention: an imaging method of the 3mm large aperture day and night confocal lens as described above, wherein light passes through a meniscus negative lens L1, a double concave negative lens L2, a double convex positive lens L3, a meniscus positive lens L4, a double convex positive lens L5, a meniscus negative lens L6, a double convex positive lens L7 and a protective glass from left to right to form an image.

[0011] Compared with the prior art, the present invention has the following beneficial effects: the 3mm large aperture day and night confocal lens of the present invention can better correct purple fringing chromatic aberration, has excellent imaging quality, realizes the function of simple structure and day and night dual use, fully meets the requirements of 8 million pixel camera, and is suitable for 4K pixel CCD or CMOS camera.

[0012] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below through specific embodiments and related drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a structural diagram of an optical system according to an embodiment of the present invention;

[0014] Figure 2 is the MTF diagram of the lens of the embodiment of the present invention in the visible light band;

[0015] Figure 3 is a graph showing axial chromatic aberration of a lens according to an embodiment of the present invention;

[0016] Figure 4 is a dispersion focus shift diagram of a lens according to an embodiment of the present invention;

[0017] Explanation of the numbers in the figure: 1-meniscus negative lens L1; 2-biconcave negative lens L2; ​​3-biconvex positive lens L3; 4-aperture; 5-meniscus positive lens L4; 6-biconvex positive lens L5; 7-meniscus negative lens L6; 8-biconvex positive lens L7; 9-protective glass; 10-imaging surface. DETAILED DESCRIPTION

[0018] like Figures 1 to 4 As shown, a 3mm large aperture day and night confocal lens, the optical system of the lens comprises a front lens group, an aperture and a rear lens group arranged in sequence along the light path direction; the front lens group is provided with a meniscus negative lens L1, a double concave negative lens L2 and a double convex positive lens L3 in sequence along the incident light path, the object side surface of the meniscus negative lens L1 is convex, and the image side surface is concave; the object side surface and the image side surface of the double concave negative lens L2 are both concave; the rear lens group is provided with a meniscus positive lens L4, a cemented group formed by closely connecting a double convex positive lens L5 and a meniscus negative lens L6, and a double convex positive lens L7 in sequence along the incident light path, and a protective glass 9 is arranged on the rear side of the double convex positive lens L7; the object side surface of the meniscus positive lens L4 is concave, and the image side surface is convex; the object side surface of the meniscus negative lens L6 is concave, and the image side surface is convex.

[0019] In this embodiment, all lenses in the front lens group and the rear lens group are made of glass and are spherical lenses.

[0020] In this embodiment, the air gap between the meniscus negative lens L1 and the biconcave negative lens L2 is 2.1-2.5 mm, preferably 2.43 mm; the air gap between the biconcave negative lens L2 and the biconvex positive lens L3 is 0.9-1.3 mm, preferably 1.05 mm; the air gap between the biconvex positive lens L3 and the aperture is 1.7-1.9 mm, preferably 1.82 mm; the air gap between the aperture and the meniscus positive lens L4 is 0-1 mm, preferably 0.07 mm; the air gap between the meniscus positive lens L4 and the cemented group is 0-1 mm, and the air gap between the cemented group and the seventh lens L7 is 0-1.5 mm, preferably 0.10 mm.

[0021] In this embodiment, the focal lengths of the meniscus negative lens L1, the biconcave negative lens L2, the biconvex positive lens L3, the meniscus positive lens L4, the biconvex positive lens L5, the meniscus negative lens L6, and the biconvex positive lens L7 are f1, f2, f3, f4, f5, f6, and f7, respectively. The focal length of the lens optical system is f, wherein f1, f2, f3, f4, f5, f6, and f7 satisfy the following ratio with f: -2.3 <f1 / f<-2.0,-2.5<f2 / f<-2.3,1.9<f3 / f<2.2,5.2<f4 / f<6.3,1.6<f5 / f<1.8,-3.5<f6 / f<-3.0,4.0<f7 / f<4.1。

[0022] In this embodiment, the refractive index N of the meniscus negative lens L1 is d and the Abbe constant V d Satisfy the relationship: N d ≥1.5, V d ≥50; the refractive index N of the biconcave negative lens L2 d and the Abbe constant V d Satisfy the relationship: N d ≥1.5, V d ≥50; the refractive index N of the biconvex positive lens L3 d and the Abbe constant V d Satisfy the relationship: N d ≥1.8, V d ≤40; the refractive index N of the meniscus positive lens L4 d and the Abbe constant V d Satisfy the relationship: N d ≥1.5, V d ≥50; the refractive index N of the biconvex positive lens L5 d and the Abbe constant V d Satisfy the relationship: Nd ≥1.5, V d ≥50; the refractive index N of the meniscus negative lens L6 d and the Abbe constant V d Satisfy the relationship: N d ≥1.8, V d ≤40; the refractive index N of the biconvex positive lens L7 d and the Abbe constant V d Satisfy the relationship: N d ≥1.5, V d ≤50.

[0023] In this embodiment, the total optical length TTL of the optical system and the focal length f of the optical system satisfy: TTL / f≤13.

[0024] The specific parameters of each lens in the lens optical system of the present invention are shown in the following table:

[0025]

[0026] The optical system composed of the above lenses achieves the following optical indicators:

[0027] (1) Focal length: EFFL = 3.00 mm;

[0028] (2) Aperture F = 1.80;

[0029] (3) Field of view: 2w ≥ 157°;

[0030] (4) |TV distortion| < 20%;

[0031] (5) The imaging circle diameter is greater than φ6.8;

[0032] (6) Working band: 420~650nm;

[0033] (7) Total optical length TTL ≤ 23 mm, optical back focus BFL ≥ 3 mm;

[0034] (8) This lens is suitable for 8-megapixel CCD or CMOS cameras.

[0035] 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 edge field of view is greater than 0.3 at the spatial frequency of 120pl / mm, and the MTF value of the center field of view is greater than 0.6 at the spatial frequency of 120pl / mm, which can meet the 4K resolution requirements. Figure 3 and Figure 4 is the axial chromatic aberration curve and dispersion focus shift diagram of the optical system. Figure 3It can be seen that the optical system also incorporates the 420nm blue light into the evaluation system, which can better correct the purple fringing chromatic aberration, thereby achieving the purpose of improving image quality. Figure 4 It can be seen that in the 420~650nm band, the lateral chromatic aberration is 3.5um, which is less than the size of two pixels. In summary, it can be seen that the optical system has excellent imaging quality and fully meets the requirements of 8 million pixel cameras.

[0036] An imaging method of the 3mm large aperture day and night confocal lens as described above, wherein light passes through a meniscus negative lens L1, a double concave negative lens L2, a double convex positive lens L3, a meniscus positive lens L4, a double convex positive lens L5, a meniscus negative lens L6, a double convex positive lens L7 and a protective glass from left to right to form an image on the image plane.

[0037] Unless otherwise stated, any technical solution disclosed in the present invention disclosed above, if it discloses a numerical range, then the disclosed numerical range is a preferred numerical range, and any technician in the field should understand that the preferred numerical range is only a numerical value with a more obvious technical effect or representative value among many implementable numerical values. Since there are too many numerical values ​​to be exhaustive, the present invention discloses some numerical values ​​to illustrate the technical solution of the present invention, and the numerical values ​​listed above should not constitute a limitation on the scope of protection of the present invention.

[0038] If the present invention discloses or involves components or structures that are fixedly connected to each other, then, unless otherwise stated, the fixed connection can be understood as: a detachable fixed connection (for example, connection using bolts or screws), and can also be understood as: a non-detachable fixed connection (for example, riveting, welding). Of course, the mutual fixed connection can also be replaced by an integrated structure (for example, manufactured by integrated molding using a casting process) (except when it is obviously impossible to use an integrated molding process).

[0039] In addition, unless otherwise stated, the terms used to indicate positional relationships or shapes in any of the technical solutions disclosed in the present invention include states or shapes that are approximate, similar, or close to them.

[0040] Any component provided by the present invention may be assembled from a plurality of separate components, or may be a separate component manufactured by an integral forming process.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the present invention, which should be included in the scope of the technical solution for protection of the present invention.

Claims

1. A 3mm large aperture day and night confocal lens, characterized by: The optical system of the lens comprises a front lens group, an aperture and a rear lens group which are arranged in sequence along the optical path direction; the front lens group is provided with a meniscus negative lens L1, a double concave negative lens L2 and a double convex positive lens L3 in sequence along the incident optical path; the rear lens group is provided with a meniscus positive lens L4, a cemented group formed by closely connecting a double convex positive lens L5 and a meniscus negative lens L6, and a double convex positive lens L7 in sequence along the incident optical path; the focal lengths of the meniscus negative lens L1, the double concave negative lens L2, the double convex positive lens L3, the meniscus positive lens L4, the double convex positive lens L5, the meniscus negative lens L6 and the double convex positive lens L7 are f1, f2, f3, f4, f5, f6, f7 in sequence, and the focal length of the lens optical system is f, wherein f1, f2, f3, f4, f5, f6, f7 and f satisfy the following ratios: -2.3< f1 / f<-2.0, -2.5< f2 / f<-2.3, 1.9< f3 / f<2.2, 5.2< f4 / f<6.3, 1.6< f5 / f<1.8, -3.5< f6 / f<-3.0, 4.0< f7 / f<4.1; the total optical length TTL of the optical system and the focal length f of the optical system satisfy: TTL / f≤13.

2. The 3 mm large aperture day and night confocal lens according to claim 1, characterized in that: All lenses in the front and rear lens groups are made of glass and are spherical lenses. A protective glass is set on the back side of the double convex positive lens L7.

3. The 3 mm large aperture day and night confocal lens according to claim 1, characterized in that: The air gap between the meniscus negative lens L1 and the double concave negative lens L2 is 2.1-2.5 mm, the air gap between the double concave negative lens L2 and the double convex positive lens L3 is 0.9-1.3 mm, the air gap between the double convex positive lens L3 and the aperture is 1.7-1.9 mm, the air gap between the aperture and the meniscus positive lens L4 is 0-1 mm, the air gap between the meniscus positive lens L4 and the cemented group is 0-1 mm, and the air gap between the cemented group and the seventh lens L7 is 0-1.5 mm.

4. The 3 mm large aperture day and night confocal lens according to claim 1, characterized in that: The refractive index N of the meniscus negative lens L1 is d and the Abbe constant V d Satisfy the relationship: N d ≥1.5, V d ≥50; the refractive index N of the biconcave negative lens L2 d and the Abbe constant V d Satisfy the relationship: N d ≥1.5, V d ≥50; the refractive index N of the biconvex positive lens L3 d and the Abbe constant V d Satisfy the relationship: N d ≥1.8, V d ≤40; the refractive index N of the meniscus positive lens L4 d and the Abbe constant V d Satisfy the relationship: N d ≥1.5, V d ≥50; the refractive index N of the biconvex positive lens L5 d and the Abbe constant V d Satisfy the relationship: N d ≥1.5, V d ≥50; the refractive index N of the meniscus negative lens L6 d and the Abbe constant V d Satisfy the relationship: N d ≥1.8, V d ≤40; the refractive index N of the biconvex positive lens L7 d and the Abbe constant V d Satisfy the relationship: N d ≥1.5, V d ≤50.

5. An imaging method of the 3 mm large aperture day and night confocal lens as claimed in claim 2, characterized in that: The light passes through the meniscus negative lens L1, the double concave negative lens L2, the double convex positive lens L3, the meniscus positive lens L4, the double convex positive lens L5, the meniscus negative lens L6, the double convex positive lens L7 and the protective glass from left to right to form an image.

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