An ultra-wide-angle low-distortion lens

Abstract

The present invention discloses an ultra-wide-angle low-distortion lens, comprising a lens body, wherein the lens body comprises, from the object plane to the image plane, a first glass meniscus lens with a negative focal length, a second lens with a negative focal length, a third lens with a positive focal length, a fourth lens with a positive focal length, a fifth lens with a negative focal length, a sixth lens with a positive focal length, a filter and a photosensitive film, the surface curvature radius of the first glass meniscus lens with a negative focal length close to the object is R1, the overall focal length of the lens body is F, the full image height of the lens body is H, and the relationship is satisfied: R1 / H<3.7, F / H<0.33. The present invention is convenient and quick to use, can achieve small distortion, and under the same horizontal field of view angle, the overall distortion is controlled within ‑13%, and plastic lenses are used to replace glass lenses to reduce weight and facilitate carrying.

Description

Technical Field

[0001] The present invention relates to the field of optical imaging technology, and in particular to an ultra-wide-angle low-distortion lens. Background Art

[0002] In recent years, as the application scope of camera lenses has become more and more extensive, for example, police law enforcement instruments, border surveillance lenses, etc., the existing law enforcement instruments and border surveillance lenses generally have the following shortcomings: the viewing angle is not large enough, the aperture is small, and the external dimensions are large. When used, they appear to be large in size and occupy more space. In order to achieve a wide viewing angle effect, the general imaging lens will have a large amount of optical distortion, so that the scenery at the edge of the picture is easily compressed, causing the user to see a deformed object. Therefore, in order to avoid the problem of severe deformation of edge objects, a lens design with a narrower viewing angle is usually adopted. Therefore, there is a need for an imaging lens design that can take into account both wide viewing angle and low compression deformation, and can provide lower manufacturing costs and better imaging quality.

[0003] The existing lens had too much distortion, up to 25%. Summary of the invention

[0004] The main purpose of the present invention is to provide an ultra-wide-angle low-distortion lens, which can effectively solve the problems in the background technology.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] An ultra-wide-angle low-distortion lens comprises a lens body, wherein the lens body comprises, from an object plane to an image plane, a first glass meniscus lens with a negative focal length, a second lens with a negative focal length, a third lens with a positive focal length, a fourth lens with a positive focal length, a fifth lens with a negative focal length, a sixth lens with a positive focal length, a filter and a photosensitive film, wherein a surface curvature radius of the first glass meniscus lens with a negative focal length close to the object is R1, the overall focal length of the lens body is F, the total image height of the lens body is H, and the relationship: R1 / H<3.7, F / H<0.33 is satisfied.

[0007] Preferably, the second lens with negative focal length is a meniscus plastic aspherical lens.

[0008] Preferably, the third lens with positive focal length is a biconvex glass spherical lens.

[0009] Preferably, the fourth lens with a positive focal length is a biconvex plastic aspheric lens.

[0010] Preferably, the fifth lens with negative focal length is a meniscus plastic aspherical lens.

[0011] Preferably, the sixth lens with a positive focal length is a biconvex plastic aspheric lens.

[0012] Preferably, the surface of the first glass meniscus lens with a negative focal length facing the object plane is convex, and the surface facing the image plane is concave; the surface of the second lens with a negative focal length facing the object plane is convex, and the surface facing the image plane is concave; the surface of the fifth lens with a negative focal length facing the object plane is concave, and the surface facing the image plane is convex.

[0013] Preferably, the refractive index of the third lens having a positive focal length satisfies: nd3>1.84.

[0014] Compared with the prior art, the present invention has the following beneficial effects: the ultra-wide-angle low-distortion lens has small distortion, and under the same horizontal field of view, the overall distortion is controlled within -13%. Plastic lenses are used instead of glass lenses, which reduces weight and is easy to carry. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The figure is a schematic diagram of a lens of an ultra-wide-angle low-distortion lens according to the present invention.

[0016] Figure 2 This is an analytical diagram of visible light of an ultra-wide-angle low-distortion lens of the present invention.

[0017] Figure 3 This is a analytical diagram of 850nm infrared light of an ultra-wide-angle low-distortion lens of the present invention.

[0018] Figure 4 This is a Spot image of an ultra-wide-angle low-distortion lens of the present invention.

[0019] Figure 5 This is a field curvature diagram of an ultra-wide-angle low-distortion lens of the present invention.

[0020] Figure 6 This is a distortion diagram of an ultra-wide-angle low-distortion lens of the present invention.

[0021] In the figure: 1. a first glass meniscus lens with a negative focal length; 2. a second lens with a negative focal length; 3. a third lens with a positive focal length; 4. a fourth lens with a positive focal length; 5. a fifth lens with a negative focal length; 6. a sixth lens with a positive focal length; 7. a filter; 8. a photosensitive film; 9. a lens body. DETAILED DESCRIPTION

[0022] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0023] like Figure 1-6As shown, an ultra-wide-angle low-distortion lens comprises a lens body 9, which comprises, from the object plane to the image plane, a first glass meniscus lens 1 with a negative focal length, a second lens 2 with a negative focal length, a third lens 3 with a positive focal length, a fourth lens 4 with a positive focal length, a fifth lens 5 with a negative focal length, a sixth lens 6 with a positive focal length, a filter 7 and a photosensitive film 8. The surface curvature radius of the first glass meniscus lens 1 with a negative focal length close to the object is R1, the overall focal length of the lens body 9 is F, and the full image height of the lens body 9 is H, satisfying the relationship: R1 / H<3.7, F / H<0.33.

[0024] The second lens 2 with a negative focal length is a meniscus plastic aspheric lens; the third lens 3 with a positive focal length is a biconvex glass spherical lens; the fourth lens 4 with a positive focal length is a biconvex plastic aspheric lens; the fifth lens 5 with a negative focal length is a meniscus plastic aspheric lens; the sixth lens 6 with a positive focal length is a biconvex plastic aspheric lens; the surface of the first glass meniscus lens 1 with a negative focal length facing the object plane is convex, and the surface facing the image plane is concave; the surface of the second lens 2 with a negative focal length facing the object plane is convex, and the surface facing the image plane is concave; the surface of the fifth lens 5 with a negative focal length facing the object plane is concave, and the surface facing the image plane is convex; the refractive index of the third lens 3 with a positive focal length satisfies: nd3>1.84.

[0025] It should be noted that the present invention is an ultra-wide-angle low-distortion lens. When in use, when the working distance is infinity, the total focal length of the ultra-wide-angle low-distortion lens is f=1.95mm, FNO=2.0, the horizontal field of view angle FOV=111°, the total length of the lens TTL=16.3mm, it can match a 4-megapixel chip, and the full field of view image height is 6.17mm. The parameters of the lens group are listed in Table 1:

[0026]

[0027]

[0028] Table 1

[0029] Note: The mirror numbers 1 and 2 of the optical system provided in Table 1 represent the two mirrors of lens 1 along the light incident direction, mirror numbers 3 and 4 represent the two mirrors of lens 2 along the light incident direction, mirror numbers 5 and 6 represent the two mirrors of lens 3 along the light incident direction, mirror numbers 7 and 8 represent the two mirrors of lens 4 along the light incident direction, mirror numbers 9 and 10 represent the two mirrors of lens 5 along the light incident direction, and mirror numbers 11 and 12 represent the two mirrors of lens 6 along the light incident direction.

[0030] From Table 1, we can get

[0031] The surface curvature radius R1 of the first glass meniscus lens 1 with a negative focal length close to the object is 22.502602.

[0032] R1 / H=22.502602 / 6.17=3.64<3.7,

[0033] F / H=1.95 / 6.17=0.316<0.33,

[0034] Nd3=1.850136,

[0035] All requirements are met;

[0036] In addition, in the embodiment of the present invention, the surfaces S3 and S4 of the second lens 2 with a negative focal length, the surfaces S7 and S8 of the fourth lens 4 with a positive focal length are aspherical surfaces, the surfaces S9 and S10 of the fifth lens 5 with a negative focal length are aspherical surfaces, and the surfaces S11 and S12 of the sixth lens 6 with a positive focal length are aspherical surfaces. The relevant values ​​of the aspherical surfaces are listed in Table 2:

[0037]

[0038]

[0039] Table 2

[0040] In the above table of the embodiment of the present patent, Index is the refractive index, Radius is the radius of curvature, and the focal lengths of the first glass meniscus lens 1 with a negative focal length to the sixth lens 6 with a positive focal length are f1 to f6 respectively. The lens provided in the embodiment is to provide an ultra-wide-angle, small distortion, high-resolution, lightweight and low-cost lens to overcome the shortcomings of the prior art. Six lenses are used, and the first lens is made of glass material, which has the characteristics of wear resistance, scratch resistance, acid and alkali corrosion resistance, etc. Four of the lenses are aspherical lenses made of plastic materials, which effectively reduce the weight and manufacturing cost of the lens and improve the competitiveness of the product; by reasonably using plastic aspherical lenses and limiting the optical focal length of each lens, the distortion of the wide-angle lens is effectively improved, and the camera effect is improved. This patent takes into account the characteristics of large field of view, low distortion, high resolution and low cost to overcome the shortcomings of the prior art.

[0041] Figure 2 Figure 3The MTF (Modulation Transfer Function) value diagram at 20 degrees Celsius in the embodiment is based on the parameters in Table 1. The measurement of the quality of the optical lens, such as resolution, is the most important. The MTF value is defined to be greater than 0 and less than 1. In the technical field, the closer the MTF value is to 1, the better the performance of the lens, that is, the higher the resolution. The variable is the spatial frequency, which is measured by the number of lines that can be presented within a mm range, and its unit is lp / mm. The fixed high-frequency (such as 250lp / mm) curve represents the lens resolution characteristic. The higher this curve is, the higher the lens resolution is. The ordinate is the MTF value. The abscissa can be set as the distance from the center of the image field to the measurement point. The lens is a symmetrical structure centered on the optical axis. The imaging quality change law from the center to all directions is the same. Due to the influence of factors such as aberrations, the farther the distance between a point in the image field and the center of the image field is, the MTF value generally shows a downward trend. Therefore, the distance from the center of the image field to the edge of the image field is used as the abscissa to reflect the imaging quality of the edge of the lens.

[0042] In addition, at a position deviated from the center of the image field, the MTF values ​​measured by the sinusoidal grating along the tangential direction and along the radial direction are different. The MTF curve generated by the lines parallel to the diameter is called the sagittal curve, marked as S (Sagittal), and the MTF curve generated by the lines parallel to the tangent is called the meridian curve, marked as T (eridional). In this way, there are generally two MTF curves, namely the S curve and the T curve. Figure 2 , Figure 3 There are multiple groups of MTF curves from the center of the image field to the edge of the image field, reflecting that this lens system has a high resolution of up to 5 million pixels, and its optical performance is greatly improved compared with the current mainstream optical system.

[0043] Figure 4 This is the point diagram corresponding to the optical lens. Its centroid radius and geometric radius are shown in the figure, which can achieve good imaging quality.

[0044] The field curvature diagram corresponding to the visible light part of the lens system consists of three curves T and three curves S; the three curves T represent the aberrations of the tangential rays corresponding to the three wavelengths (486nm, 587nm and 656nm), and the three curves S represent the aberrations of the sagittal rays corresponding to the three wavelengths (486nm, 587nm and 656nm). The smaller the meridional field curvature and sagittal field curvature values ​​are, the better the imaging quality is. Figure 5 As shown, the meridian field curvature value is controlled within the range of -0.02 to 0.02 mm, and the sagittal field curvature value is controlled within the range of -0.02 to 0.02 mm.

[0045] In summary, the present invention is an ultra-wide-angle low-distortion lens, an ultra-wide-angle, small-distortion, high-resolution, lightweight and low-cost lens, which overcomes the shortcomings of the prior art. Six lenses are used, and the first lens is made of glass, which has the characteristics of wear resistance, scratch resistance, acid and alkali corrosion resistance, etc. Four of the lenses are aspherical lenses made of plastic materials, which effectively reduce the weight and manufacturing cost of the lens and improve product competitiveness; through the reasonable use of plastic aspherical lenses and limiting the optical focal length of each lens, the distortion of the wide-angle lens is effectively improved, and the camera effect is improved. This patent takes into account the characteristics of large field of view, low distortion, high resolution and low cost to overcome the shortcomings of the prior art.

[0046] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. An ultra-wide-angle low-distortion lens, comprising a lens body (9), characterized in that: The lens body (9) has six lenses, which include, from the object plane to the image plane, a first glass meniscus lens (1) with a negative focal length, a second lens (2) with a negative focal length, a third lens (3) with a positive focal length, a fourth lens (4) with a positive focal length, a fifth lens (5) with a negative focal length, a sixth lens (6) with a positive focal length, a filter (7) and a photosensitive film (8). The surface curvature radius of the first glass meniscus lens (1) with a negative focal length close to the object is R1. The overall focal length of the lens body (9) is F, F=1.95 mm. The total image height of the lens body (9) is H, which satisfies the relationship: R1 / H<3.7, F / H<0.

33. The surface of the first glass meniscus lens (1) with a negative focal length facing the object plane is a convex surface, and the surface facing the image plane is a concave surface; the surface of the second lens (2) with a negative focal length facing the object plane is a convex surface, and the surface facing the image plane is a concave surface; the surface of the fifth lens (5) with a negative focal length facing the object plane is a concave surface, and the surface facing the image plane is a convex surface; The second lens (2) with a negative focal length is a meniscus plastic aspheric lens; the third lens (3) with a positive focal length is a biconvex glass spherical lens; the fourth lens (4) with a positive focal length is a biconvex plastic aspheric lens; the fifth lens (5) with a negative focal length is a meniscus plastic aspheric lens; and the sixth lens (6) with a positive focal length is a biconvex plastic aspheric lens.

2. The ultra-wide-angle low-distortion lens according to claim 1, characterized in that: The refractive index of the third lens (3) with a positive focal length satisfies: nd3>1.84.

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