CN111273429A - Optical imaging system - Google Patents
Optical imaging system Download PDFInfo
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- CN111273429A CN111273429A CN202010221313.5A CN202010221313A CN111273429A CN 111273429 A CN111273429 A CN 111273429A CN 202010221313 A CN202010221313 A CN 202010221313A CN 111273429 A CN111273429 A CN 111273429A
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/001—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras
- G02B13/0015—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/001—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras
- G02B13/0015—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design
- G02B13/002—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design having at least one aspherical surface
- G02B13/0045—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design having at least one aspherical surface having five or more lenses
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Abstract
The invention discloses an optical imaging system which is of a seven-piece aspheric structure and comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an infrared filter and an image sensor which are sequentially arranged from an object side to an image side, wherein the first lens has positive diopter, the second lens has negative diopter, the third lens has positive diopter, the fourth lens has diopter, the fifth lens has diopter, the object side surface of the fifth lens is in an inverse curved shape, the central part of the fifth lens is convex towards the object surface direction, the edge part of the fifth lens is totally curved towards the object surface direction and is in an Arabic numeral '3' shape, the sixth lens has diopter, and the seventh lens has diopter Tolerance sensitivity of eccentricity, concentricity and inclination error improves the yield of the camera module.
Description
Technical Field
The present invention relates to an optical imaging system, and more particularly, to a miniaturized optical imaging system applied to an electronic product.
Background
At present, smart phones which are newly released in the market are continuously upgraded on a rear camera. The mobile phone camera is experiencing the trend of upgrading from 6M → 8M → 13M → 16M → 24M → 48M → 64M → 108M in a short period of years, and the rear pixels almost show the trend of upgrading from year to year. It is known from the supply chain channel of the camera industry that some well-known cell phone manufacturers have planned to include a 216M pixel development agenda in the next two years. Each mobile phone manufacturer gains the market through the continuous upgrade of camera pixels and the addition of camera functions.
In order to achieve the continuous upgrade of the pixels of the mobile phone camera, a great change of the current mobile phone camera technology is to adopt a CMOS with a larger size used on the digital camera to improve the image quality. The 1/1.7 inch class of CMOS is now the new choice for cell phone camera sensors. More handsets have also used sensors on the order of 1/2.3 inch. The sensors used by these conventional card DC cameras have become the choice of the next generation of camera phones. Obviously, cell phones have begun to eliminate conventional digital cameras from the hardware parameters.
Because the requirements for the number of pixels and the resolution ratio are continuously improved, the top-level specification of all smart phone cameras with more than 2 million pixels is generally a mobile phone camera with six-piece aspheric lens, which has been used for many years, but the top-level specification of all smart phone cameras with more than 2 million pixels can only be used for a mobile phone camera with less than 24M generally, and a mobile phone camera with higher pixels is difficult to meet the requirements due to the increase of the size and the view field of a sensor panel, so that a mobile phone camera with seven-piece aspheric lens or a plastic aspheric mobile phone camera with more than one piece is required. With the expansion of the application of mobile phone cameras with multiple lenses and seven-piece aspheric lenses, the smart phone needs to detonate the camera in the future.
At present, each famous mobile phone manufacturer has a three-lens or multi-lens scheme, and a mobile phone camera with seven-piece aspheric lenses is discussed. In the three lenses, each single lens has a high specification, and in the future, the three lenses can also see one or two mobile phone cameras with seven-piece aspheric lenses.
For a mobile phone camera with a seven-piece aspheric lens, the specification is higher, better imaging quality can be achieved, but great challenges are provided for optical design, ultra-precision machining and assembly precision of the lens and yield of final assembly. The first is a mobile phone camera with seven-piece aspheric lens, and because each piece is a plastic aspheric surface, the requirements on surface type errors, concentricity, gradient and assembly errors of the lens are very strict. Firstly, the surface type error and the Asia Si of the lens are generally required to be within 1 Newton ring (namely, the surface type error is approximately 0.3 micron), the assembly error between the lens and the lens is generally required to be within 2 microns, and the concentricity of two surfaces of the lens and the concentricity between the lenses are also required to be within 1 micron, so that the imaging definition on the sensor can be ensured. Meanwhile, as seven plastic aspheric surfaces are adopted, the integral transmittance of the mobile phone camera is also reduced by a lot and is generally not more than 70%; in addition, as the number of the mobile phone cameras is more, the Fresnel part reflection between each surface is also more, and the problem of stray light or ghost image is more serious than that of the prior six or five cameras, so that the problem of transmittance and stray light can be improved by plating an antireflection film on each lens of the camera.
In recent years, a seven-piece mobile phone camera has been designed, for example, patent TW201403166A in taiwan, which solves the problems of a large field of view (a field angle greater than 80 degrees) and a large panel sensor, and can obtain a clear image. However, these configurations also have problems with the fact that the second face 162 of the sixth lens 160, whose central portion is too convex, has a central thickness that is more than twice the thickness of the edge of the lens, which results in the face 162 being very sensitive to face type errors, decentration, concentricity, and tilt errors. Still there is the thickness inequality of lens easily to lead to the lens in the injection moulding drawing of patterns in-process, produce the inferior si phenomenon of XY direction face type error imbalance, lead to the camera and produce blurring and ghost image when shooing, reduced the yields of camera, another main problem is that the partial reflection of the middle protruding position of second face 162 of sixth lens 160 can lead to miscellaneous light and ghost image, under the condition that is met strong light irradiation, the position within 0.707 visual field of image plane easily produces the miscellaneous light that can not dispel, the solution only through plating the antireflection coating that the transmissivity is high on the surface of lens, can improve the problem of miscellaneous light to a certain extent.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, and provides an optical imaging system which can well solve the problem of stray light, greatly reduce the tolerance sensitivity of the camera module to face shape errors, eccentricity, concentricity and inclination errors and improve the yield of the camera module.
In order to achieve the above object, the present invention provides an optical imaging system, which is a seven-piece aspheric structure, and includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an infrared filter and an image sensor sequentially arranged from an object side to an image side, wherein the first lens has a positive refractive power, the second lens has a negative refractive power, the third lens has a positive refractive power, the fourth lens has a refractive power, the fifth lens has a fifth lens object side surface and a fifth lens image side surface, the fifth lens object side surface is a reverse curved shape, a central portion is convex toward an object plane, an area between the central portion and the edge portion is curved toward an image plane, and the edge portion of the fifth lens, the fourth lens is provided with a refractive power, the sixth lens is provided with a sixth lens object side surface and a sixth lens image side surface, the center part of the sixth lens object side surface is convex towards the object side direction, the center part of the sixth lens image side surface is convex towards the image plane direction, the seventh lens is provided with a refractive power, the seventh lens is provided with a seventh lens object side surface and a seventh lens image side surface, the center part of the seventh lens object side surface is concave towards the inside of the lens, and the center part of the seventh lens image side surface is concave towards the inside of the lens.
Preferably, the ratio of the edge thickness to the center thickness of the fourth, fifth and sixth lenses is: DT/DC is more than 0.2 and less than 4.
Preferably, the combined focal length of the optical imaging system ranges from: f is more than 3.65mm and less than 7.5mm, and the diagonal size of the image surface is more than 6.4 mm.
Preferably, the first lens has a first lens object-side surface and a first lens image-side surface, both of which are curved in the image plane direction, and the ratio of the focal length f1 of the first lens to the combined focal length f of the optical imaging system is
The first lens is an optical material component with low refractive index and high dispersion coefficient, the refractive index nd of the first lens is less than 1.58, and the dispersion coefficient vd of the first lens is more than 50.
Preferably, the second lens has a central thickness thinner than an edge thickness, and a ratio of a focal length f2 of the second lens to a combined focal length f of the optical imaging system is
The second lens is an optical material component with high refractive index and low dispersion coefficient, the refractive index nd is more than 1.6, and the dispersion coefficient vd is less than 30.
Preferably, the ratio of the focal length f3 of the third lens to the combined focal length f of the optical imaging system is
The third lens is an optical material component with low refractive index and high dispersion coefficient, the refractive index nd of the third lens is less than 1.58, and the dispersion coefficient vd of the third lens is more than 50.
Preferably, the fourth lens has a fourth lens object-side surface and a fourth lens image-side surface, the fourth lens object-side surface is curved toward the object plane, and a ratio of a focal length f4 of the fourth lens to a combined focal length f of the optical imaging system is
The fourth lens is an optical material component with high refractive index and low dispersion coefficient, the refractive index nd is more than 1.6, and the dispersion coefficient vd is less than 30.
Preferably, the fifth lens has a fifth lens object side surface anda fifth lens image side surface having a relatively flat curved surface design with a sagittal height to clear optical aperture ratio of less than 0.2, i.e. a
Its radius of curvature R251The ratio to the combined focal length f of the optical imaging system is
The ratio of the focal length f5 of the fifth lens to the combined focal length f of the optical imaging system is
Preferably, the ratio of the focal length f6 of the sixth lens to the combined focal length f of the optical imaging system is
Preferably, the seventh lens is thinner in the middle, gradually thicker from the middle to the edge, and then thinner, the ratio of the thickest part to the thinnest part of the seventh lens is less than 3, the object side surface and the image side surface of the seventh lens are both relatively gentle, and the ratio of the sagittal height to the caliber is less than 0.2, namely
And
compared with the prior art, the invention has the beneficial effects that:
the invention is provided with an optical imaging system, the optical imaging system is a seven-piece aspheric structure, and comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an infrared filter and an image sensor which are arranged in sequence from an object side to an image side, the first lens is provided with positive diopter, the second lens is provided with negative diopter, the third lens is provided with positive diopter, the fourth lens is provided with diopter, the fifth lens is provided with a fifth lens object side surface and a fifth lens surface, the fifth lens object side surface is in a reverse curve shape, a central part is convex towards the object surface direction, a region between the central part and a marginal part is curved towards the image surface direction, the marginal part of the fifth lens is curved towards the object surface direction, the shape of the optical imaging system is Arabic numeral '3', the sixth lens has a diopter, the sixth lens has a sixth lens object side surface and a sixth lens image side surface, the center of the sixth lens object side surface is convex towards the object plane direction, the center of the sixth lens image side surface is convex towards the image plane direction, the seventh lens has a diopter, the seventh lens has a seventh lens object side surface and a seventh lens image side surface, the center of the seventh lens object side surface is concave towards the lens interior, the fifth lens is designed to be a reverse-curved shape, the diopter of a part of the sixth lens can be shared, the sixth lens can be thinned, the optical imaging system can control the ratio of the edge thickness to the center thickness of the fourth lens, the fifth lens and the sixth lens to be within 0.5 < DT/DC < 2, meanwhile, the thickness ratio of the seventh lens is electrically controlled, the problem of image surface curvature caused by the size of a large sensor can be solved, the optical imaging system can well solve the problem of stray light, the tolerance sensitivity of the camera module to surface errors, eccentricity, concentricity and inclination errors is greatly reduced, and the yield of the camera module is improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a cross-sectional view of a seven-plate optical imaging system proposed in patent TW 201403166A;
FIG. 2 is a cross-sectional view of an optical imaging system in accordance with an embodiment of the present invention;
FIG. 3 is a cross-sectional view of a first lens of an optical imaging system in accordance with an embodiment of the present invention;
FIG. 4 is a cross-sectional view of a second optic of an optical imaging system in accordance with an embodiment of the present invention;
FIG. 5 is a cross-sectional view of a third optic of an optical imaging system in accordance with an embodiment of the present invention;
FIG. 6 is a cross-sectional view of a fourth optic of an optical imaging system in accordance with an embodiment of the present invention;
FIG. 7 is a cross-sectional view of a fifth optic of an optical imaging system in accordance with an embodiment of the present invention;
FIG. 8 is a cross-sectional view of a sixth optic of an optical imaging system in accordance with an embodiment of the present invention;
FIG. 9 is a cross-sectional view of a seventh optic of an optical imaging system in accordance with an embodiment of the present invention;
FIG. 10 is an optical path diagram of an optical imaging system in accordance with an embodiment of the present invention;
FIG. 11 is a modulation transfer function MTF curve for an optical imaging system in accordance with an embodiment of the present invention;
FIG. 12 is an MTF-depth of focus curve for an optical imaging system in accordance with an embodiment of the present invention;
FIG. 13 is a dot-column diagram of an optical imaging system in accordance with an embodiment of the present invention;
FIG. 14 illustrates field curvature and F-Tan (θ) distortion of an optical imaging system in accordance with an embodiment of the present invention;
FIG. 15 is a cross-sectional view of an optical imaging system according to a second embodiment of the invention;
FIG. 16 is a cross-sectional view of a first lens of an optical imaging system in accordance with a second embodiment of the present invention;
FIG. 17 is a cross-sectional view of a second lens of an optical imaging system in accordance with a second embodiment of the invention;
FIG. 18 is a cross-sectional view of a third lens of an optical imaging system in accordance with a second embodiment of the invention;
FIG. 19 is a cross-sectional view of a fourth lens of an optical imaging system in accordance with a second embodiment of the invention;
FIG. 20 is a cross-sectional view of a fifth lens of an optical imaging system in accordance with a second embodiment of the invention;
FIG. 21 is a cross-sectional view of a sixth lens of an optical imaging system in accordance with a second embodiment of the invention;
FIG. 22 is a cross-sectional view of a seventh optic of an optical imaging system in accordance with a second embodiment of the present invention;
FIG. 23 is an optical path diagram of an optical imaging system according to a second embodiment of the present invention;
FIG. 24 is a dot-column diagram of an optical imaging system according to a second embodiment of the present invention;
FIG. 25 shows the field curvature and F-Tan (θ) distortion of an optical imaging system according to a second embodiment of the present invention;
FIG. 26 is a cross-sectional view of a third optical imaging system in accordance with embodiments of the present invention;
FIG. 27 is a cross-sectional view of a first lens of a third optical imaging system in accordance with an embodiment of the present invention;
FIG. 28 is a cross-sectional view of the second and third lenses of a three-mode optical imaging system in accordance with an embodiment of the present invention;
FIG. 29 is a cross-sectional view of a fourth lens of a third optical imaging system in accordance with an embodiment of the present invention;
FIG. 30 is a cross-sectional view of a fifth lens of a third optical imaging system in accordance with an embodiment of the present invention;
FIG. 31 is a cross-sectional view of a sixth lens of a third optical imaging system in accordance with an embodiment of the present invention;
FIG. 32 is a cross-sectional view of a seventh optic of a third optical imaging system in accordance with an embodiment of the present invention;
FIG. 33 is an optical path diagram of an optical imaging system according to a third embodiment of the present invention;
FIG. 34 is a dot-column diagram of an optical imaging system in accordance with a third embodiment of the present invention;
FIG. 35 shows the field curvature and F-Tan (θ) distortion of three optical imaging systems according to embodiments of the present invention.
The figure includes:
2-optical imaging system, 21-first lens, 22-second lens, 23-third lens, 24-fourth lens, 25-fifth lens, 26-sixth lens, 27-seventh lens, 28-infrared filter, 29-image sensor, 211-first lens object side surface, 212-first lens image side surface, 221-second lens object side surface, 222-second lens image side surface, 231-third lens object side surface, 232-third lens image side surface, 241-fourth lens object side surface, 242-fourth lens image side surface, 251-fifth lens object side surface, 252-fifth lens image side surface, 261-sixth lens object side surface, 262-sixth lens image side surface, 271-seventh lens object side surface, 272, the image side surface of the seventh lens, the object side surface of the 281-infrared filter, the image side surface of the 282-infrared filter and 291-image surface.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are one embodiment of the present invention, and not all embodiments of the present invention. All other embodiments obtained by a person skilled in the art based on the embodiments of the present invention without any creative work shall fall within the protection scope of the present invention.
Example one
Referring to fig. 2 to 9, in the first embodiment, an optical imaging system is provided, where the optical imaging system 2 has a seven-piece aspheric structure, and includes a first lens 21, a second lens 22, a third lens 23, a fourth lens 24, a fifth lens 25, a sixth lens 26, a seventh lens 27, an infrared filter 28 and an image sensor 29, which are sequentially disposed from an object side to an image side, and an aperture stop of the optical imaging system is located on an object side surface 211 of the first lens.
The range of the combined focal length of the optical imaging system 2 is: f is more than 3.65mm and less than 7.5mm, the diagonal size of the image plane is more than 6.4mm, and the preferred combined focal length of the optical imaging system 2 in this embodiment is: and f is 3.827817451978569 mm.
The cross-sectional view of the first lens 21 is shown in FIG. 3, which has a positive refractive powerThe first lens 21 has a first lens object-side surface 211 and a first lens image-side surface 212, both the first lens object-side surface 211 and the first lens image-side surface 212 are curved in the image plane direction, and a ratio of a focal length f1 of the first lens 21 to a combined focal length f of the optical imaging system 2 is
The first lens 21 is an optical material member with low refractive index and high dispersion coefficient, the refractive index nd is less than 1.58, and the dispersion coefficient vd is more than 50.
The cross-sectional view of the second lens 22 is shown in fig. 4, which has a negative refractive power, the center thickness of the second lens 22 is thinner than the edge thickness, the second lens 22 has a second lens object-side surface 221 and a second lens image-side surface 222, the second lens object-side surface 221 has a slight reverse curvature, the center portion of the second lens object-side surface 221 is curved toward the image plane direction, and the edge portion is curved slightly toward the object side direction; the image-side surface 222 of the second lens element is curved in the image plane direction, and the ratio of the focal length f2 of the second lens element 22 to the combined focal length f of the optical imaging system 2 is
The second lens 22 is an optical material member with high refractive index and low dispersion coefficient, the refractive index nd is more than 1.6, and the dispersion coefficient vd is less than 30.
The cross-sectional view of the third lens element 23 is shown in fig. 5, which has a positive refractive power, the third lens element 23 has a third lens element object-side surface 231 and a third lens element image-side surface 232, the third lens element object-side surface 231 curves in the image plane direction, the third lens element image-side surface 232 curves in the object plane direction, and a ratio of a focal length f3 of the third lens element 23 to a combined focal length f of the optical imaging system 2 is
The third lens 23 is an optical material member with low refractive index and high dispersion coefficient, the refractive index nd is less than 1.58, and the dispersion coefficient vd is more than 50.
The fourth lens 24 is shown in cross-sectionFig. 6 shows a refractive power, the fourth lens 24 has a fourth lens object-side surface 241 and a fourth lens image-side surface 242, the fourth lens object-side surface 241 and the fourth lens image-side surface 242 are both curved toward the object plane, and a ratio of a focal length f4 of the fourth lens 24 to a combined focal length f of the optical imaging system 2 is
The fourth lens 24 is an optical material member with high refractive index and low dispersion coefficient, the refractive index nd is more than 1.6, and the dispersion coefficient vd is less than 30.
The cross-sectional view of the fifth lens 25 is shown in fig. 7, which has a refractive power, the fifth lens 25 has a fifth lens object-side surface 251 and a fifth lens image-side surface 252, the fifth lens object-side surface 251 has a reverse curved shape, a central portion is convex toward the object plane, a region between the central portion and the edge portion is curved toward the image plane, all the edge portions of the fifth lens object-side surface 251 and the fifth lens image-side surface 252 are curved toward the object plane, and have shapes of arabic numbers "3", the reverse curved design of the fifth lens 25 can share a part of the refractive power of the sixth lens 26, so that the thickness of the sixth lens 26 can be reduced, the curved design of the fifth lens object-side surface 251 is relatively gentle, and the ratio of the sagittal height to the optical clear aperture is less than 0.2, that is to say, the fifth lens 25 has a fifth lens object-side surface 251 and a fifth lens image-side surface 252
The fifth lens object side surface 251 having a radius of curvature R251The ratio to the combined focal length f of the optical imaging system 2 is
The ratio of the focal length f5 of the fifth lens element 25 to the combined focal length f of the optical imaging system 2 is
The cross-sectional view of the sixth lens 26 is shown in FIG. 8, which has optical power, and the sixth lens 26 has optical powerA sixth lens object-side surface 261 and a sixth lens image-side surface 262, wherein the sixth lens object-side surface 261 has a slightly reverse curved shape, a central portion thereof is curved in an image plane direction and convex in an object plane direction, an edge portion thereof is curved in an object plane direction, the sixth lens image-side surface 262 is curved in the object plane direction and convex in the image plane direction, and a ratio of a focal length f6 of the sixth lens 26 to a combined focal length f of the optical imaging system 2 is
The cross-sectional view of the seventh lens 27 is shown in fig. 9, which has diopter, the seventh lens 27 is thinner in the middle, gradually thickens from the middle to the edge, and then becomes thinner, the ratio of the thickest portion to the thinnest portion of the seventh lens 27 is less than 3, the seventh lens 27 has a seventh lens object-side surface 271 and a seventh lens image-side surface 272, the center portion of the seventh lens object-side surface 271 curves toward the object plane, the edge portion curves toward the image plane, the center portion of the seventh lens surface 272 curves toward the image plane, the edge portion curves toward the object plane, the object-side surface 271 and the seventh lens image-side surface 272 are both more compact, the ratio of the vector height to the aperture is less than 0.2, that is, the seventh lens object-side surface 271 and the seventh lens image-side surface 272 are both less flat, that is
And
in the optical imaging system 2 with a seven-piece aspheric structure provided in this embodiment, the fifth lens 25 is designed into a reverse-curved shape, and can share a part of diopter of the sixth lens 26, so that the sixth lens 26 can be thinned, the optical imaging system 2 can control the ratio of the edge thickness to the center thickness of the fourth lens 24, the fifth lens 25 and the sixth lens 26 to be within 0.2 < DT/DC < 4, and simultaneously control the thickness ratio of the seventh lens 27, and can improve the problem of curvature of image plane caused by a large sensor size, the optical imaging system 2 can well solve the problem of stray light, greatly reduce the tolerance of the camera module to the face shape error, eccentricity, concentricity and inclination error, and improve the yield of the camera module.
The optical path parameters of the lens in the optical imaging system 2 of the present embodiment, including the radius of curvature, the thickness, the refractive index nd, the abbe number Vd, the clear aperture, the conic coefficient and the focal length of each lens, are shown in table 1.
The first lens 21 has a positive diopter, the first lens 21 is an optical material member with a low refractive index and a high dispersion coefficient, the refractive index nd is less than 1.58, the dispersion coefficient vd is greater than 50, in the first embodiment, the refractive index nd is 1.544502, the abbe coefficient vd is 55.986991, and the focal length is 5.6502358 mm.
The second lens 22 has a negative refractive power, the second lens 22 is an optical material member with a high refractive index and a low abbe number, the refractive index nd is greater than 1.60, the abbe number vd is less than 30, in the first embodiment, the refractive index nd is 1.661319, the abbe number vd is 20.374576, and the focal length is-12.584821 mm.
The third lens 23 has a positive refractive power, the third lens 23 is an optical material member with a low refractive index and a high dispersion coefficient, the refractive index nd is less than 1.58, the dispersion coefficient vd is greater than 50, in the first embodiment, the refractive index nd is 1.544502, the abbe coefficient vd is 55.986991, and the focal length is 6.4870885 mm.
The fourth lens 24 has diopter, and the fourth lens 24 is an optical material member with high refractive index and low dispersion coefficient, the refractive index nd is greater than 1.60, the dispersion coefficient vd is less than 30, in the first embodiment, the refractive index nd is 1.661319, the abbe coefficient vd is 20.374576, and the focal length is-5.3258553 mm.
The fifth lens 25 has diopter, the fifth lens 25 is an optical material member with low refractive index and high dispersion coefficient, the refractive index nd is less than 1.58, the dispersion coefficient vd is greater than 50, in the first embodiment, the refractive index nd is 1.544502, the abbe coefficient vd is 55.986991, and the focal length is 3.7967055 mm.
The sixth lens 26 has diopter, and the sixth lens 26 is an optical material member with high refractive index and low abbe number, the refractive index nd is greater than 1.60, the abbe number vd is less than 30, in the first embodiment, the refractive index nd is 1.661319, the abbe number vd is 20.374576, and the focal length is 5.3048433 mm.
The seventh lens 27 has diopter, the seventh lens 27 is an optical material member with low refractive index and high dispersion coefficient, the refractive index nd is less than 1.58, the dispersion coefficient vd is greater than 50, in the first embodiment, the refractive index nd is 1.544919, the abbe coefficient vd is 55.929938, and the focal length is-2.4182302 mm.
Table 1 optical path parameters of the lens in an optical imaging system 2 of the present embodiment:
the aspheric coefficients of each mirror surface in the optical imaging system 2 of the present embodiment have respective aspheric coefficients from a quadratic coefficient a1 to a sixteen quadratic coefficient a8, as shown in table 2. The expression of the aspheric surface is shown as the following formula:
wherein z is rise-of-rise (SAG); c is the curvature, which is the inverse of the radius of curvature; r is the radius of the aspheric caliber; a1, a2, a3 … … … are aspheric coefficients.
Table 2 aspherical surface coefficients of each mirror surface in the optical imaging system 2 of the present embodiment:
in the optical path diagram of the optical imaging system 2 of the present embodiment, as shown in fig. 10, the MTF curve is as shown in fig. 11, and at the position of 110 line pairs, the modulation transfer function of the central field exceeds 0.82, the worst modulation transfer function of the edge 1 field also exceeds 0.55, and the modulation transfer functions of the other fields are all above 0.6. The MTF-depth of focus curve is shown in FIG. 12, the MTF of the focus position is concentrated, almost no focus offset is caused by field curvature, the dot diagram is shown in FIG. 13, the size of the dot diagram of the minimum root mean square of the central field of view is about 1 micron, the curve diagram of the field curvature and the distortion is shown in FIG. 14, the F-Tan (theta) is controlled within 1.5%, the design result reaches the expected target, and meanwhile, because the fourth lens 24, the fifth lens 25 and the sixth lens 26 are all designed to be relatively flat, the image side surface 262 of the sixth lens has no specially convex part, the tolerance sensitivity of the lenses is greatly improved, the problem of stray light is solved, and the yield of the camera is improved.
Example two
Referring to fig. 15 to 22, in a second embodiment, an optical imaging system is provided, in which the optical imaging system 2 has a seven-piece aspheric structure, and includes a first lens 21, a second lens 22, a third lens 23, a fourth lens 24, a fifth lens 25, a sixth lens 26, a seventh lens 27, an infrared filter 28 and an image sensor 29, which are sequentially disposed from an object side to an image side, and an aperture stop of the optical imaging system is located on an image side surface 212 of the first lens.
Fig. 15 is a cross-sectional view of an optical imaging system 2 provided in the second embodiment, where a combined focal length of the optical imaging system 2 ranges from: f is more than 3.65mm and less than 7.5mm, the diagonal size of the image plane is more than 6.4mm, and the preferred combined focal length of the optical imaging system 2 in the second embodiment is: and f is 4.2878353 mm.
The cross-sectional view of the first lens 21 is shown in fig. 16, which has a positive refractive power, the first lens 21 has a first lens object-side surface 211 and a first lens image-side surface 212, both the first lens object-side surface 211 and the first lens image-side surface 212 are curved in the image plane direction, and a ratio of a focal length f1 of the first lens 21 to a combined focal length f of the optical imaging system 2 is
The first lens 21 is an optical material member with low refractive index and high dispersion coefficient, the refractive index nd is less than 1.58, and the dispersion coefficient vd is more than 50.
The cross-sectional view of the second lens 22 is shown in fig. 17, which has negative refractive power, the center thickness of the second lens 22 is thinner than the edge thickness, the second lens 22 has a second lens object-side surface 221 and a second lens image-side surface 222, the second lens object-side surface 221 is curved in the image plane direction, the second lens image-side surface 222 is curved in the image plane direction, and the ratio of the focal length f2 of the second lens 22 to the combined focal length f of the optical imaging system 2 is
The second lens 22 is an optical material member with high refractive index and low dispersion coefficient, the refractive index nd is more than 1.6, and the dispersion coefficient vd is less than 30.
The cross-sectional view of the third lens 23 is shown in fig. 18, which has a positive refractive power, the third lens 23 has a third lens object-side surface 231 and a third lens image-side surface 232, the third lens object-side surface 231 has a slightly reverse curved shape, a central portion thereof is curved toward the image plane, a peripheral portion thereof is curved toward the object side, the third lens image-side surface 232 is curved toward the object plane, and a ratio of a focal length f3 of the third lens 23 to a combined focal length f of the optical imaging system 2 is
The third lens 23 is an optical material member with low refractive index and high dispersion coefficient, the refractive index nd is less than 1.58, and the dispersion coefficient vd is more than 50.
The cross-sectional view of the fourth lens 24 is shown in fig. 19, which has refractive power, the fourth lens 24 has a fourth lens object-side surface 241 and a fourth lens image-side surface 242, both the fourth lens object-side surface 241 and the fourth lens image-side surface 242 are curved toward the object plane, and a ratio of a focal length f4 of the fourth lens 24 to a combined focal length f of the optical imaging system 2 is
The fourth lens 24 is an optical material member with high refractive index and low dispersion coefficient, the refractive index nd is more than 1.6, and the dispersion coefficient vd is less than 30.
The cross-sectional view of the fifth lens 25 is shown in fig. 20, which has a refractive power, the fifth lens 25 has a fifth lens object-side surface 251 and a fifth lens image-side surface 252, the fifth lens object-side surface 251 has a reverse curved shape, a central portion is convex toward the object plane, a region between the central portion and a peripheral portion is curved toward the image plane, the peripheral portions of the fifth lens object-side surface 251 and the fifth lens image-side surface 252 are all curved toward the object plane, and have shapes of arabic numbers "3", the reverse curved design of the fifth lens 25 can share a part of the refractive power of the sixth lens 26, so that the thickness of the sixth lens 26 can be reduced, the curved design of the fifth lens object-side surface 251 is relatively gentle, and the ratio of the sagittal height to the optical clear aperture is less than 0.2, that is to say, that
The fifth lens object side surface 251 having a radius of curvature R251The ratio to the combined focal length f of the optical imaging system 2 is
The ratio of the focal length f5 of the fifth lens element 25 to the combined focal length f of the optical imaging system 2 is
The cross-sectional view of the sixth lens 26 is shown in fig. 21, which has diopter, the sixth lens 26 has a sixth lens object-side surface 261 and a sixth lens image-side surface 262, the sixth lens object-side surface 261 has a slightly reverse curved shape, a central portion thereof is curved in the image plane direction and convex in the object plane direction, an edge portion thereof is curved in the object plane direction, the sixth lens image-side surface 262 is curved in the object plane direction and convex in the image plane direction, and the sixth lens 26 has a sixth lens object-side surface 261 and a sixth lens image-side surface 262The ratio of the focal length f6 of the six-lens 26 to the combined focal length f of the optical imaging system 2 is
The cross-sectional view of the seventh lens 27 is shown in fig. 22, which has a refractive power, the seventh lens 27 is thinner at the middle, gradually gets thicker from the middle to the edge, and then gets thinner, the ratio of the thickest part to the thinnest part of the seventh lens 27 is less than 3, the seventh lens 27 has a seventh object-side surface 271 and a seventh image-side surface 272, the center of the seventh object-side surface 271 is curved toward the object plane, the edge of the seventh object-side surface 271 is concave toward the image plane, the center of the seventh surface 272 is curved toward the image plane, the edge of the seventh surface 272 is curved toward the object plane, the object-side surface 271 and the image-side surface 272 are both less than 0.2 in comparison, the ratio of the vector height to the aperture is less than 0.2, that is, i.e., the seventh object-side surface 271 and the seventh image-side surface 272 are both
And
in the optical imaging system 2 with a seven-piece aspheric structure provided in the second embodiment, the fifth lens 25 is designed into a reverse-curved shape, and can share a part of diopter of the sixth lens 26, so that the sixth lens 26 can be thinned, the optical imaging system 2 can control the ratio of the edge thickness to the center thickness of the fourth lens 24, the fifth lens 25 and the sixth lens 26 to be within 0.2 < DT/DC < 4, and simultaneously control the thickness ratio of the seventh lens 27, and can improve the problem of curvature of image plane caused by a large sensor size, the optical imaging system 2 can well solve the problem of stray light, greatly reduce the tolerance of the camera module to face shape errors, eccentricity, concentricity and inclination errors, and improve the yield of the camera module.
The optical path parameters of the lenses in the second optical imaging system 2 of this embodiment, including the radius of curvature, the thickness, the refractive index nd, the abbe number Vd, the clear aperture, the conic coefficient, and the focal length of each lens, are shown in table 3.
The first lens 21 has a positive diopter, the first lens 21 is an optical material member with a low refractive index and a high dispersion coefficient, the refractive index nd is less than 1.58, the dispersion coefficient vd is greater than 50, in the second embodiment, the refractive index nd is 1.544502, the abbe coefficient vd is 55.986991, and the focal length is 5.7430798 mm.
The second lens 22 has a negative refractive power, the second lens 22 is an optical material member with a high refractive index and a low abbe number, the refractive index nd is greater than 1.60, the abbe number vd is less than 30, in the second embodiment, the refractive index nd is 1.661319, the abbe number vd is 20.374576, and the focal length is-17.3394354 mm.
The third lens 23 has a positive refractive power, the third lens 23 is an optical material member with a low refractive index and a high dispersion coefficient, the refractive index nd is less than 1.58, the dispersion coefficient vd is greater than 50, in the second embodiment, the refractive index nd is 1.544502, the abbe coefficient vd is 55.986991, and the focal length is 9.1200987 mm.
The fourth lens 24 has diopter, the fourth lens 24 is an optical material member with high refractive index and low dispersion coefficient, the refractive index nd is greater than 1.60, the dispersion coefficient vd is less than 30, in the second embodiment, the refractive index nd is 1.635517, the abbe coefficient vd is 23.971841, and the focal length is-10.2106903 mm.
The fifth lens 25 has diopter, the fifth lens 25 is an optical material member with high refractive index and low dispersion coefficient, the refractive index nd is larger than 1.60, the dispersion coefficient vd is smaller than 30, in the second embodiment, the refractive index nd is 1.671371, the abbe coefficient vd is 19.244900, and the focal length is-65.7029839 mm.
The sixth lens 26 has diopter, the sixth lens 26 is an optical material member with low refractive index and high dispersion coefficient, the refractive index nd is less than 1.58, the dispersion coefficient vd is greater than 50, in the second embodiment, the refractive index nd is 1.544502, the abbe coefficient vd is 55.986991, and the focal length is 2.6088521 mm.
The seventh lens 27 has diopter, the seventh lens 27 is an optical material member with low refractive index and high dispersion coefficient, the refractive index nd is less than 1.58, the dispersion coefficient vd is greater than 50, in the second embodiment, the refractive index nd is 1.544502, the abbe coefficient vd is 55.986991, and the focal length is-2.2351735 mm.
Table 3 optical path parameters of the lens in the second optical imaging system 2 of the present embodiment:
the aspheric coefficients of each mirror surface in the second optical imaging system 2 of the present embodiment have respective aspheric coefficients from the quadratic coefficient a1 to the sixteen quadratic coefficient a8, as shown in table 4. The expression of the aspheric surface is shown as the following formula:
wherein z is rise-of-rise (SAG); c is the curvature, which is the inverse of the radius of curvature; r is the radius of the aspheric caliber; a1, a2, a3 … … … are aspheric coefficients.
Table 4 aspherical surface coefficient of each mirror surface in the second optical imaging system 2 of the present embodiment:
in the optical path diagram of the second optical imaging system 2 of this embodiment, as shown in fig. 23, the dot diagram is shown in fig. 24, the size of the dot diagram with the minimum root mean square of the central field of view is about 1 micron, the curve of the field curvature and the distortion is shown in fig. 25, the F-Tan (θ) is controlled within 1.5%, the design result reaches the expected target, and meanwhile, since the fourth lens 24, the fifth lens 25 and the sixth lens 26 are designed to be relatively flat, the image-side surface 262 of the sixth lens has no particularly convex portion, and the thickest portion in the center is not more than 2 times thicker than the thinnest portion at the edge, the tolerance sensitivity of the lenses is greatly improved, and meanwhile, the problem of stray light is solved, and the yield of the camera is improved.
EXAMPLE III
Referring to fig. 26 to 32, a third embodiment provides an optical imaging system, in which the optical imaging system 2 has a seven-piece aspheric structure, and includes a first lens 21, a second lens 22, a third lens 23, a fourth lens 24, a fifth lens 25, a sixth lens 26, a seventh lens 27, an infrared filter 28 and an image sensor 29, which are sequentially disposed from an object side to an image side, wherein the second lens 22 and the third lens 23 are glued together by canadian glue, and an aperture stop thereof is located on an image side surface 212 of the first lens.
Fig. 26 is a cross-sectional view of an optical imaging system 2 provided in a third embodiment, where a combined focal length of the optical imaging system 2 ranges from: f is more than 3.65mm and less than 7.5mm, the diagonal size of the image plane is more than 6.4mm, and the preferred combined focal length of the optical imaging system 2 in this embodiment is: and f is 3.8186254 mm.
The cross-sectional view of the first lens 21 is shown in fig. 27, which has a positive refractive power, the first lens 21 has a first lens object-side surface 211 and a first lens image-side surface 212, both the first lens object-side surface 211 and the first lens image-side surface 212 are curved in the image plane direction, and a ratio of a focal length f1 of the first lens 21 to a combined focal length f of the optical imaging system 2 is
The first lens 21 is an optical material member with low refractive index and high dispersion coefficient, the refractive index nd is less than 1.58, and the dispersion coefficient vd is more than 50.
The second lens element 22 and the third lens element 23 are cemented together to form a cemented aspheric lens assembly, and the cross-sectional view of the cemented aspheric lens assembly is shown in fig. 28. the second lens element 22 has a negative refractive power, the center thickness of the second lens element 22 is thinner than the edge thickness, the second lens element 22 has a second object-side surface 221 and a second image-side surface 222, the second object-side surface 221 has a slight reverse curvature, and the second object-side surface 221 has a convex shapeThe central part is bent towards the image surface direction, and the edge part is slightly bent towards the object side direction; the image-side surface 222 of the second lens element is curved in the image plane direction, and the ratio of the focal length f2 of the second lens element 22 to the combined focal length f of the optical imaging system 2 is
The second lens 22 is an optical material member with high refractive index and low dispersion coefficient, the refractive index nd is more than 1.6, and the dispersion coefficient vd is less than 30.
The third lens element 23 has a positive refractive power, the third lens element 23 has a third lens element object-side surface 231 and a third lens element image-side surface 232, the third lens element object-side surface 231 and the second lens element image-side surface 222 are the same, the third lens element object-side surface 231 and the second lens element image-side surface 222 have the same aspheric coefficients, the third lens element object-side surface 231 curves in the image plane direction, the third lens element object-side surface 231 and the second lens element image-side surface 222 are bonded together by canadian glue, the third lens element image-side surface 232 curves in the object plane direction, and a ratio of a focal length f3 of the third lens element 23 to a combined focal length f of the optical imaging system 2 is
The third lens 23 is an optical material member with low refractive index and high dispersion coefficient, the refractive index nd is less than 1.58, and the dispersion coefficient vd is more than 50.
The cross-sectional view of the fourth lens element 24 is shown in fig. 29, which has refractive power, the fourth lens element 24 has a fourth lens element object-side surface 241 and a fourth lens element image-side surface 242, both the fourth lens element object-side surface 241 and the fourth lens element image-side surface 242 are curved toward the object plane, and the ratio of the focal length f4 of the fourth lens element 24 to the combined focal length f of the optical imaging system 2 is
The fourth lens 24 is an optical material member with high refractive index and low dispersion coefficient, the refractive index nd is more than 1.6, and the dispersion coefficient vd is less than 30.
The cross-sectional view of the fifth lens 25 is shown in FIG. 30The fifth lens 25 has a refractive power, the fifth lens 25 has a fifth lens object-side surface 251 and a fifth lens image-side surface 252, the fifth lens object-side surface 251 is reversely curved, the central portion thereof is convex toward the object plane, the area between the central portion and the edge portion thereof is curved toward the image plane, the edge portions of the fifth lens object-side surface 251 and the fifth lens image-side surface 252 are both curved toward the object plane, the shape thereof is an arabic numeral "3", the fifth lens 25 can share a part of the refractive power of the sixth lens 26 by designing the reverse curve of the fifth lens 25, so that the thickness of the sixth lens 26 can be reduced, the curved surface design of the fifth lens object-side surface 251 is relatively gentle, and the ratio of the height to the optical clear aperture is less than 0.2, that is, i.e., the fifth lens 25 has a fifth lens object-side surface 251 and a
The fifth lens object side surface 251 having a radius of curvature R251The ratio to the combined focal length f of the optical imaging system 2 is
The ratio of the focal length f5 of the fifth lens element 25 to the combined focal length f of the optical imaging system 2 is
The cross-sectional view of the sixth lens 26 is shown in fig. 31, which has diopter, the sixth lens 26 has a sixth lens object-side surface 261 and a sixth lens image-side surface 262, the sixth lens object-side surface 261 has a slightly reverse curved shape, a central portion thereof is curved toward the image plane and convex toward the object plane, an edge portion thereof is curved toward the object plane, the sixth lens image-side surface 262 is curved toward the object plane and convex toward the image plane, and a ratio of a focal length f6 of the sixth lens 26 to a combined focal length f of the optical imaging system 2 is
The cross-sectional view of the seventh lens 27 is shown in FIG. 32, which has diopter, thereforeThe seventh lens 27 is thinner in the middle, gradually becomes thicker from the middle to the edge, and then becomes thinner, the ratio of the thickest part to the thinnest part of the seventh lens 27 is less than 3, the seventh lens 27 has a seventh lens object side surface 271 and a seventh lens image side surface 272, the center part of the seventh lens object side surface 271 bends toward the object plane, the edge part thereof is concave toward the image plane, the center part of the seventh lens image side surface 272 bends toward the image plane, the edge part thereof is concave toward the lens, the edge part thereof bends toward the object plane, the seventh lens object side surface 271 and the seventh lens image side surface 272 are gentler, the ratio of the sagittal height to the aperture is less than 0.2, that is, the seventh lens object side surface 271 and the seventh lens image side surface 272 are all gentler, and the ratio of the sagittal height to the aperture
And
in the optical imaging system 2 with a seven-piece aspheric structure provided in the third embodiment, the fifth lens 25 is designed into a reverse-curved shape, and can share a part of diopter of the sixth lens 26, so that the sixth lens 26 can be thinned, the optical imaging system 2 can control the ratio of the edge thickness to the center thickness of the fourth lens 24, the fifth lens 25 and the sixth lens 26 to be within 0.2 < DT/DC < 4, and simultaneously control the thickness ratio of the seventh lens 27, and can improve the problem of curvature of image plane caused by a large sensor size, the optical imaging system 2 can well solve the problem of stray light, greatly reduce the tolerance of the camera module to face shape errors, eccentricity, concentricity and inclination errors, and improve the yield of the camera module.
The optical path parameters of the lenses in the three-optical imaging system 2 of the present embodiment, including the radius of curvature, the thickness, the refractive index nd, the abbe number Vd, the clear aperture, the conic coefficient, and the focal length of each lens, are shown in table 5.
The first lens 21 has a positive diopter, the first lens 21 is an optical material member with a low refractive index and a high dispersion coefficient, the refractive index nd is less than 1.58, the dispersion coefficient vd is greater than 50, in the third embodiment, the refractive index nd is 1.544502, the abbe coefficient vd is 55.986991, and the focal length is 5.3818184 mm.
The second lens 22 has a negative refractive power, the second lens 22 is an optical material member with a high refractive index and a low abbe number, the refractive index nd is greater than 1.60, the abbe number vd is less than 30, in the third embodiment, the refractive index nd is 1.661319, the abbe number vd is 20.374576, and the focal length is-10.7468271 mm.
The third lens 23 has a positive refractive power, the third lens 23 is an optical material member with a low refractive index and a high dispersion coefficient, the refractive index nd is less than 1.58, the dispersion coefficient vd is greater than 50, in the third embodiment, the refractive index nd is 1.544502, the abbe coefficient vd is 55.986991, and the focal length is 6.4297160 mm.
The fourth lens 24 has diopter, and the fourth lens 24 is an optical material member with high refractive index and low dispersion coefficient, the refractive index nd is greater than 1.60, the dispersion coefficient vd is less than 30, in the third embodiment, the refractive index nd is 1.661319, the abbe coefficient vd is 20.374576, and the focal length is-4.7478218 mm.
The fifth lens 25 has diopter, the fifth lens 25 is an optical material member with low refractive index and high dispersion coefficient, the refractive index nd is less than 1.58, the dispersion coefficient vd is greater than 50, in the third embodiment, the refractive index nd is 1.544502, the abbe coefficient vd is 55.986991, and the focal length is 2.9569209 mm.
The sixth lens 26 has diopter, and the sixth lens 26 is an optical material member with high refractive index and low abbe number, the refractive index nd is greater than 1.60, the abbe number vd is less than 30, in the third embodiment, the refractive index nd is 1.661319, the abbe number vd is 20.374576, and the focal length is 6.4275854 mm.
The seventh lens 27 has diopter, the seventh lens 27 is an optical material member with low refractive index and high dispersion coefficient, the refractive index nd is less than 1.58, the dispersion coefficient vd is greater than 50, in the third embodiment, the refractive index nd is 1.544502, the abbe coefficient vd is 55.986991, and the focal length is-2.3091884 mm.
Table 5 optical path parameters of the lens in the three-optical imaging system 2 of the present embodiment:
the aspherical surface coefficient of each mirror surface in the three-optical imaging system 2 of the present embodiment is the aspherical surface coefficients of the terms from the quadratic term coefficient a1 to the sixteen-order term coefficient a8, as shown in table 6. The expression of the aspheric surface is shown as the following formula:
wherein z is rise-of-rise (SAG); c is the curvature, which is the inverse of the radius of curvature; r is the radius of the aspheric caliber; a1, a2, a3 … … … are aspheric coefficients.
Table 6 aspherical surface coefficient of each mirror surface in the three-optical imaging system 2 of the present embodiment:
in the optical path diagram of the three-optical imaging system 2 of this embodiment, as shown in fig. 33, the dot diagram is shown in fig. 34, the size of the dot diagram with the minimum root mean square of the central field of view is about 1.5 micrometers, the graph of the field curvature and distortion is shown in fig. 35, the F-Tan (θ) is controlled within 1.5%, the design result reaches the expected target, and meanwhile, since the fourth lens 24, the fifth lens 25 and the sixth lens 26 are all designed to be relatively gentle, the image side surface 262 of the sixth lens has no particularly convex portion, the thickest portion in the center is thinner than the portion with the thinnest edge, and the thickness is not more than 2 times, the tolerance sensitivity of the lenses is greatly improved, and meanwhile, the problem of stray light is electrically solved, and the yield of the camera is improved.
Claims (10)
1. An optical imaging system, characterized in that the optical imaging system (2) is a seven-piece aspheric structure, comprising a first lens (21), a second lens (22), a third lens (23), a fourth lens (24), a fifth lens (25), a sixth lens (26), a seventh lens (27), an infrared filter (28) and an image sensor (29) arranged in order from an object side to an image side, the first lens (21) having a positive refractive power, the second lens (22) having a negative refractive power, the third lens (23) having a positive refractive power, the fourth lens (24) having a refractive power, the fifth lens (25) having a fifth lens object side surface (251) and a fifth image side surface (252), the fifth lens object side surface (251) being a sigmoidal shape, the central part is convex towards the object plane, the area between the central part and the edge part is curved towards the image plane, the edge part of the fifth lens (25) is curved towards the object plane, in the shape of the Arabic numerals "3", said sixth lens (26) having a refractive power, the sixth lens (26) having a sixth lens object side surface (261) and a sixth lens image side surface (262), a central part of the sixth lens object side surface (261) is convex towards the object plane direction, a central part of the sixth lens image side surface (262) is convex towards the image plane direction, the seventh lens (27), having a refractive power, the seventh lens (27) having a seventh lens object side surface (271) and a seventh lens image side surface (272), the center of the seventh lens object side surface (271) is concave towards the inside of the lens, and the center of the seventh lens image side surface (272) is concave towards the inside of the lens.
2. An optical imaging system according to claim 1, characterized in that the fourth (24), fifth (25) and sixth (26) lenses have a ratio of edge thickness to central thickness of: DT/DC is more than 0.2 and less than 4.
3. An optical imaging system according to claim 1, characterized in that the combined focal length of the optical imaging system (2) ranges from: f is more than 3.65mm and less than 7.5mm, and the diagonal size of the image surface is more than 6.4 mm.
4. The method of claim 1An optical imaging system, characterized in that the first lens (21) has a first lens object side surface (211) and a first lens image side surface (212), the first lens object side surface (211) and the first lens image side surface (212) are both curved towards the image plane direction, the ratio of the focal length f1 of the first lens (21) to the combined focal length f of the optical imaging system (2) is
The first lens (21) is an optical material component with low refractive index and high dispersion coefficient, the refractive index nd is less than 1.58, and the dispersion coefficient vd is more than 50.
5. An optical imaging system according to claim 1, characterized in that the second lens (22) has a central thickness thinner than the peripheral thickness, the ratio of the focal length f2 of the second lens (22) to the combined focal length f of the optical imaging system (2) being such that
The second lens (22) is an optical material component with high refractive index and low dispersion coefficient, the refractive index nd is more than 1.6, and the dispersion coefficient vd is less than 30.
6. An optical imaging system according to claim 1, characterized in that the ratio of the focal length f3 of the third lens element (23) to the combined focal length f of the optical imaging system (2) is
The third lens (23) is an optical material component with low refractive index and high dispersion coefficient, the refractive index nd of the third lens is less than 1.58, and the dispersion coefficient vd of the third lens is more than 50.
7. The optical imaging system of claim 1, wherein the fourth lens element (24) has a fourth lens element object-side surface (241) and a fourth lens element image-side surface (242), the fourth lens element object-side surface (241) is curved toward the object plane, and a focal length f4 of the fourth lens element (24) and the optical imaging system(2) Has a ratio of the combined focal lengths f of
The fourth lens (24) is an optical material component with high refractive index and low dispersion coefficient, the refractive index nd is more than 1.6, and the dispersion coefficient vd is less than 30.
8. An optical imaging system according to claim 1, characterized in that the fifth lens (25) has a fifth lens object-side surface (251) and a fifth lens image-side surface (252), the curved design of the fifth lens object-side surface (251) being relatively gentle with a vector height to optical clear aperture ratio of less than 0.2, i.e. the ratio of the optical clear aperture is smaller than
Its radius of curvature R251The ratio of the combined focal length f of the optical imaging system (2) to the combined focal length f is
The ratio of the focal length f5 of the fifth lens (25) to the combined focal length f of the optical imaging system (2) is
9. An optical imaging system according to claim 1, characterized in that the ratio of the focal length f6 of the sixth lens element (26) to the combined focal length f of the optical imaging system (2) is
10. An optical imaging system according to claim 1, characterized in that the seventh lens (27) is thinner in the middle, gradually thicker from the middle to the edge and then thinner, the ratio of the thickest to the thinnest part of the seventh lens (27) is less than 3, the object-side surface (271) and the image-side surface (27) of the seventh lens are2) Are all relatively gentle, and the ratio of rise to caliber is less than 0.2, namely
And
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