A low-cost, low-distortion day-night confocal lens and imaging method thereof

Abstract

The present invention relates to a low-cost, low-distortion day-night confocal lens and an imaging method thereof, comprising a front lens group A, an aperture C and a rear lens group B arranged in sequence from left to right along the incident light path of light, wherein the front lens group A comprises a first meniscus negative lens; the rear lens group B comprises a first biconvex positive lens, a second biconvex positive lens and a first biconcave negative lens arranged in sequence, wherein the first meniscus negative lens, the second biconvex positive lens and the first biconcave negative lens are all plastic aspheric lenses. The present invention has a simple structure, small size, low cost, low distortion, large aperture, high resolution, a working distance of 0.1M‑Inf, day-night confocality, and can be used with a 6-megapixel CCD or CMOS chip.

Description

Technical field:

[0002] The invention relates to a low-cost, low-distortion day-night confocal lens and an imaging method thereof. Background technology:

[0004] In recent years, as the application scope of camera lenses has become more and more extensive, people have higher and higher requirements for lens imaging. However, existing lenses generally have the following disadvantages: (1) The optical distortion of the imaging is too large, which causes the edge image to be compressed and blurred, affecting the resolution of the edge field of view; (2) The imaging object distance requirement is relatively far, and it is impossible to image the close-up; (3) There is no day and night confocal design, and another lens is required for night imaging; (4) The aperture is small, and it cannot meet the minimum imaging illumination requirement of the CCD chip under low illumination and cannot form a clear image; the cost is high; (5) The size is large and occupies more space. Summary of the invention:

[0006] The present invention makes improvements on the problems existing in the above-mentioned prior art, that is, the technical problem to be solved by the present invention is to provide a low-cost, low-distortion day and night confocal lens and an imaging method thereof.

[0007] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a low-cost, low-distortion day and night confocal lens, comprising a front lens group A, an aperture C and a rear lens group B arranged in sequence from left to right along the incident light path of the light, the front lens group A includes a first meniscus negative lens; the rear lens group B includes a first biconvex positive lens, a second biconvex positive lens and a first biconcave negative lens arranged in sequence, the first meniscus negative lens, the second biconvex positive lens and the first biconcave negative lens are all plastic aspheric lenses.

[0008] Furthermore, the air gap between the first meniscus negative lens and the first biconvex positive lens is 5.2mm-5.3mm, the air gap between the first biconvex positive lens and the second biconvex positive lens is 0.3mm-0.35mm, and the air gap between the second biconvex positive lens and the first biconcave negative lens is 0.09mm-0.11mm.

[0009] Furthermore, the total focal length of the lens is set to f, and the focal lengths of the first meniscus negative lens, the first biconvex positive lens, the second biconvex positive lens, and the first biconcave negative lens are set to f1, f2, f3, and f4 in sequence along the incident direction of the light. The relationship between the focal lengths of the lenses is as follows: -2.2 <f1 / f<-2、2.4<f2 / f<2.5、1.0<f3 / f<1.1、-1.1<f4 / f<-1.0。

[0010] Furthermore, a parallel flat plate is provided on the right side of the rear lens group B, and an IMA image surface is provided on the right side of the parallel flat plate.

[0011] Another technical solution adopted by the present invention is: an imaging method of a low-cost, low-distortion day and night confocal lens. When imaging, the light passes through the first meniscus negative lens, the aperture C, the first biconvex positive lens, the second biconvex positive lens, the first biconcave negative lens and the parallel plate from left to right, and finally forms an image on the IMA image plane.

[0012] Compared with the prior art, the present invention has the following effects: the present invention has a simple structure, small size, low cost, low distortion, large aperture, high resolution, a working distance of 0.1M-Inf, day and night confocality, and can be used with a 6-megapixel CCD or CMOS chip. Description of the drawings:

[0014] Figure 1 is a schematic structural diagram of an optical system according to an embodiment of the present invention;

[0015] Figure 2 is a schematic diagram of the visible light MTF value of an embodiment of the present invention;

[0016] Figure 3 850nm night vision MTF value schematic diagram of an embodiment of the present invention;

[0017] Figure 4 Schematic diagram of field curvature and optical distortion according to an embodiment of the present invention.

[0018] In the figure:

[0019] 100-front lens group A; 110-first meniscus negative lens; 200-rear lens group B; 210-first biconvex positive lens; 220-second biconvex positive lens; 230-third biconcave negative lens; 300-aperture C; 400-parallel plate; 500-IMA image plane. Specific implementation method:

[0021] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0023] like Figures 1 to 4As shown, a low-cost, low-distortion day-night confocal lens of the present invention comprises a front lens group A100, an aperture C300 and a rear lens group B200 arranged in sequence from left to right along the incident light path of the light, wherein the front lens group A100 comprises a first meniscus negative lens 110; the rear lens group B200 comprises a first biconvex positive lens 210, a second biconvex positive lens 220 and a first biconcave negative lens 230 arranged in sequence, wherein the first meniscus negative lens 110, the second biconvex positive lens 220 and the first biconcave negative lens 230 are all plastic aspheric lenses, and the first biconvex positive lens 210 is made of glass. The lens has a simple structure, small size, low cost, low distortion, large aperture, high resolution, a working distance of 0.1M-Inf, day-night confocality, and can be used with a 6-megapixel CCD or CMOS chip.

[0024] In this embodiment, the air gap between the first meniscus negative lens 110 and the first biconvex positive lens 210 is 5.2mm-5.3mm, the air gap between the first biconvex positive lens 210 and the second biconvex positive lens 220 is 0.3mm-0.35mm, and the air gap between the second biconvex positive lens 220 and the first biconcave negative lens 230 is 0.09mm-0.11mm.

[0025] In this embodiment, the total focal length of the lens is set to f, and the focal lengths of the first meniscus negative lens 110, the first biconvex positive lens 210, the second biconvex positive lens 220, and the first biconcave negative lens 230 are set to f1, f2, f3, and f4 in sequence along the incident direction of the light. The relationship between the focal lengths of the lenses is as follows: -2.2 <f1 / f<-2、2.4<f2 / f<2.5、1.0<f3 / f<1.1、-1.1<f4 / f<-1.0。

[0026] In this embodiment, a parallel plate 400 is disposed on the right side of the rear lens group B200 , and an IMA image plane 500 is disposed on the right side of the parallel plate 400 .

[0027] In this embodiment, specific lens parameters are shown in Table 1 below:

[0028]

[0029] Table 1

[0030] In this embodiment, the surface equation of the aspheric surface is as follows:

[0031]

[0032] Among them, z is the distance vector height from the vertex of the aspherical surface when the aspherical surface is at a height of r along the optical axis, c is the curvature of the aspherical surface paraxially, c=1 / R, R is the radius of curvature, c is the reciprocal of the radius of curvature, k is the cone coefficient, a1 is the second-order coefficient of the aspherical surface, a2 is the fourth-order coefficient of the aspherical surface, a3 is the sixth-order coefficient of the aspherical surface, a4 is the eighth-order coefficient of the aspherical surface, a5 is the tenth-order coefficient of the aspherical surface, a6 is the twelfth-order coefficient of the aspherical surface, a7 is the fourteenth-order coefficient of the aspherical surface, and a8 is the sixteenth-order coefficient of the aspherical surface. The aspherical coefficients of the three aspherical lenses (the first meniscus negative lens, the second double convex positive lens, and the first double concave negative lens) are as follows:

[0033] (1) First meniscus negative lens:

[0034]

[0035] (2) Second biconvex positive lens:

[0036]

[0037] (3) The first double concave negative lens:

[0038]

[0039] In this embodiment, the technical indicators achieved by the lens are as follows: (1) focal length: EFFL = 2.25mm; (2) F number = 2.6; (3) field of view: 2w ≥ 85°; (4) imaging circle diameter greater than Ф4mm; (5) working spectrum range: 430nm ~ 730nm (Day) 850nm (Night); (6) total optical length TTL ≤ 13.8mm, optical back intercept ≥ 1.8mm; (7) maximum semi-diameter of the lens < 2.9mm; (8) optical distortion < -3%; (9) the lens is suitable for 6 million pixel high-resolution CCD or CMOS cameras.

[0040] In this embodiment, when the low-cost and low-distortion day and night confocal lens forms an image, the light passes through the first meniscus negative lens, the aperture C, the first biconvex positive lens, the second biconvex positive lens, the first biconcave negative lens and the parallel plate from left to right, and finally forms an image on the IMA image plane; when the light passes through the front group A100, the first meniscus negative lens of the front group lens A100 can converge the incident angle of the light, and when the light passes through the rear group lens B200, the three lenses of the rear group B200 balance the aberrations, reasonably use the materials of the high and low dispersion aspheric surfaces, control the aspheric surface shape and the air distance between the aspheric surfaces, so that the chromatic aberration is well corrected, and day and night confocality is achieved.

[0041] In this embodiment, when designing the lens, two structures of the visible spectrum of F, C, and D and the night vision spectrum of 850nm are adopted, and the F / # is set to 2.6, the aperture is large, and the image can be quickly and clearly formed in low illumination. By reasonably allocating the optical power of the four lenses, the total optical length of the lens is compressed while maintaining small distortion, making the optical system structure compact, which is conducive to saving the use cost.

[0042] This lens adopts a four-piece structure and reasonably distributes the optical power. The front lens group converges the incident angle of light, and the rear three lenses balance the aberration. The material combination of high and low dispersion aspherical surfaces is reasonably used to control the air distance between the aspherical surface shape and the aspherical surface, so that the chromatic aberration is well corrected and the day and night confocality is achieved.

[0043] 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).

[0044] 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.

[0045] 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.

[0046] 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 low-cost, low-distortion day-night confocal lens, characterized by: It comprises a front lens group A, an aperture C and a rear lens group B which are arranged in sequence from left to right along the incident light path of the light, wherein the front lens group A comprises a first meniscus negative lens; the rear lens group B comprises a first biconvex positive lens, a second biconvex positive lens and a first biconcave negative lens which are arranged in sequence, and the first meniscus negative lens, the second biconvex positive lens and the first biconcave negative lens are all plastic aspherical lenses; The air gap between the first meniscus negative lens and the first biconvex positive lens is 5.2mm-5.3mm, the air gap between the first biconvex positive lens and the second biconvex positive lens is 0.3mm-0.35mm, and the air gap between the second biconvex positive lens and the first biconcave negative lens is 0.09mm-0.11mm; Set the total focal length of the lens to f, and set the focal lengths of the first meniscus negative lens, the first biconvex positive lens, the second biconvex positive lens, and the first biconcave negative lens to f1, f2, f3, and f4 in sequence along the incident direction of the light. The relationship between the focal lengths of the lenses is as follows: -2.2 <f1 / f<-2、2.4<f2 / f<2.5、1.0<f3 / f<1.1、-1.1<f4 / f<-1.0; The lens parameters are shown in the following table: The surface equation of an aspheric surface is as follows: Wherein, z is the distance vector height from the vertex of the aspheric surface when the aspheric surface is at a height of r along the optical axis, c is the curvature of the paraxial aspheric surface, c=1 / R, R is the radius of curvature, c is the reciprocal of the radius of curvature, k is the cone coefficient, a1 is the second-order coefficient of the aspheric surface, a2 is the fourth-order coefficient of the aspheric surface, a3 is the sixth-order coefficient of the aspheric surface, a4 is the eighth-order coefficient of the aspheric surface, a5 is the tenth-order coefficient of the aspheric surface, a6 is the twelfth-order coefficient of the aspheric surface, a7 is the fourteenth-order coefficient of the aspheric surface, and a8 is the sixteenth-order coefficient of the aspheric surface; The aspheric coefficients of the first meniscus negative lens are as follows: The aspheric coefficients of the second biconvex positive lens are as follows: The aspheric coefficients of the first biconcave negative lens are as follows: 。 2. The low-cost, low-distortion day-night confocal lens according to claim 1, characterized in that: A parallel flat plate is provided on the right side of the rear lens group B, and an IMA image surface is provided on the right side of the parallel flat plate.

3. A low-cost, low-distortion day-night confocal lens imaging method, characterized in that: The invention comprises a low-cost, low-distortion day-night confocal lens as claimed in any one of claims 1 to 2. When imaging, light passes through a first meniscus negative lens, an aperture C, a first biconvex positive lens, a second biconvex positive lens, a first biconcave negative lens and a parallel plate from left to right in sequence, and finally forms an image on an IMA image plane.

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