CN113253434B - Optical lens and imaging apparatus - Google Patents
Optical lens and imaging apparatus Download PDFInfo
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- CN113253434B CN113253434B CN202110759461.7A CN202110759461A CN113253434B CN 113253434 B CN113253434 B CN 113253434B CN 202110759461 A CN202110759461 A CN 202110759461A CN 113253434 B CN113253434 B CN 113253434B
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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
- G02B13/004—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 four lenses
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
- G02B1/04—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of organic materials, e.g. plastics
- G02B1/041—Lenses
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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
- G02B13/06—Panoramic objectives; So-called "sky lenses" including panoramic objectives having reflecting surfaces
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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
- G02B13/18—Optical objectives specially designed for the purposes specified below with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration
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Abstract
The invention discloses an optical lens and imaging equipment, the optical lens includes from the object side to the imaging surface along the optical axis in turn: a first lens having a negative optical power, an object-side surface of the first lens being convex at a paraxial region and having at least one inflection point, an image-side surface of the first lens being concave; a diaphragm; the second lens is provided with positive focal power, and the object side surface and the image side surface of the second lens are convex surfaces; a third lens having a positive optical power, the third lens having convex object and image side surfaces; a fourth lens element having a negative optical power, the fourth lens element having a concave object-side surface and a convex image-side surface at a paraxial region; the first lens, the third lens and the fourth lens are plastic aspheric lenses, and the second lens is a glass spherical lens. The optical lens has the advantages of large field angle, high pixel, day and night confocal property, good thermal stability and relatively low cost.
Description
Technical Field
The present invention relates to the field of imaging lens technology, and in particular, to an optical lens and an imaging device.
Background
With the gradual expansion of the application range and the scene of the security monitoring video technology and the increasingly strengthened requirements of security monitoring in the aspects of high definition, networking, intellectualization and the like, the technical level requirements of security monitoring lens products in the aspects of obtaining a large visual field, outputting high-definition images, performing day-night confocal color imaging, overcoming the influence of severe environment on imaging quality and the like are also increasingly improved.
Most of monitoring lenses popular in the market at present have small field angles, are difficult to acquire imaging pictures in a large field of view, and cannot meet actual requirements; in addition, many monitoring lenses have more lenses, even lenses made of all-glass materials, so that the lenses have higher cost and larger volume, and are not favorable for popularization and application in the market.
Disclosure of Invention
Therefore, the present invention is directed to an optical lens and an imaging apparatus, which have at least the advantages of large field angle, high pixel, day and night confocal property, good thermal stability and relatively low cost.
The embodiment of the invention implements the above object by the following technical scheme.
In a first aspect, the present invention provides an optical lens, comprising, in order from an object side to an image plane along an optical axis: a first lens having a negative optical power, an object-side surface of the first lens being convex at a paraxial region and having at least one inflection point, an image-side surface of the first lens being concave; a diaphragm; the second lens is provided with positive focal power, and the object side surface and the image side surface of the second lens are convex surfaces; a third lens having a positive optical power, the third lens having convex object and image side surfaces; a fourth lens element having a negative optical power, the fourth lens element having a concave object-side surface and a convex image-side surface at a paraxial region; the first lens, the third lens and the fourth lens are plastic aspheric lenses, and the second lens is a glass spherical lens.
In a second aspect, the present invention provides an imaging apparatus, comprising an imaging element and the optical lens provided in the first aspect, wherein the imaging element is configured to convert an optical image formed by the optical lens into an electrical signal.
Compared with the prior art, the optical lens and the imaging equipment provided by the invention effectively control the hot focal point offset by reasonably matching the shapes and focal powers of the four glass-plastic mixed lenses with specific refractive power, so that the lens still has good imaging performance in high and low temperature environments (-40-80 ℃); the position of the diaphragm and the surface shape of each lens are reasonably arranged, so that the lens has the characteristics of large wide angle and super-large aperture, and the imaging requirement of a light and shade environment is met; meanwhile, the device has the advantages of high pixel, day and night confocal property and relatively low cost, and can meet the use requirements of security monitoring equipment.
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
fig. 1 is a schematic structural diagram of an optical lens according to a first embodiment of the present invention;
FIG. 2 is a vertical axis chromatic aberration diagram of an optical lens according to a first embodiment of the present invention;
FIG. 3 is a defocus graph of the central field of view of the visible light band of the optical lens according to the first embodiment of the present invention;
FIG. 4 is a defocus graph of the central field of view of the infrared band of the optical lens according to the first embodiment of the present invention;
FIG. 5 is a MTF graph of the optical lens of the first embodiment of the present invention at a temperature of-40 ℃;
FIG. 6 is a MTF graph of the optical lens of the first embodiment of the present invention at a high temperature of 80 ℃;
FIG. 7 is a vertical axis chromatic aberration diagram of an optical lens according to a second embodiment of the present invention;
FIG. 8 is a defocus graph of the central field of view of the visible light band of the optical lens according to the second embodiment of the present invention;
FIG. 9 is a defocus graph of the central field of view of the infrared band of the optical lens according to the second embodiment of the present invention;
FIG. 10 is a MTF graph of an optical lens of a second embodiment of the present invention at a temperature of-40 ℃;
FIG. 11 is a MTF graph of an optical lens of a second embodiment of the present invention at a high temperature of 80 ℃;
FIG. 12 is a vertical axis chromatic aberration diagram of an optical lens according to a third embodiment of the present invention;
FIG. 13 is a defocus plot of the central field of view in the visible light band of the optical lens according to the third embodiment of the present invention;
FIG. 14 is a defocus plot of the central field of view of the infrared band of the optical lens according to the third embodiment of the present invention;
FIG. 15 is a MTF graph of an optical lens of a third embodiment of the present invention at a temperature of-40 ℃;
FIG. 16 is a MTF graph of an optical lens of a third embodiment of the present invention at a high temperature of 80 ℃;
FIG. 17 is a vertical axis chromatic aberration diagram of an optical lens according to a fourth embodiment of the present invention;
FIG. 18 is a defocus graph of the central field of view in the visible light band of the optical lens according to the fourth embodiment of the present invention;
FIG. 19 is a defocus plot of the central field of view of the infrared band of the optical lens according to the fourth embodiment of the present invention;
FIG. 20 is a MTF graph of an optical lens of a fourth embodiment of the present invention at a temperature of-40 ℃;
FIG. 21 is a MTF graph of an optical lens of a fourth embodiment of the present invention at a high temperature of 80 ℃;
fig. 22 is a schematic structural view of an image forming apparatus provided in a fifth embodiment of the present invention.
Detailed Description
In order to make the objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. Several embodiments of the invention are presented in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Like reference numerals refer to like elements throughout the specification.
The invention provides an optical lens, which sequentially comprises a first lens, a diaphragm, a second lens, a third lens, a fourth lens and an optical filter from an object side to an image plane along an optical axis.
The first lens element has a negative focal power, an object-side surface of the first lens element is convex at a paraxial region and has at least one inflection point, and an image-side surface of the first lens element is concave.
The second lens has positive focal power, and both the object-side surface and the image-side surface of the second lens are convex surfaces.
The third lens has positive focal power, and both the object-side surface and the image-side surface of the third lens are convex surfaces.
The fourth lens element has a negative power, a concave object-side surface, and a convex image-side surface at a paraxial region.
As an embodiment, the optical lens satisfies the following conditional expression:
-2.6<f1/EPD<-2.4；（1）
where f1 denotes a focal length of the first lens, and EPD denotes an entrance pupil diameter of the optical lens. When the conditional expression (1) is satisfied, the light transmission amount of the optical lens can be reasonably controlled, the aberration of the optical lens can be favorably reduced, and the resolving power of the optical lens can be improved.
As an embodiment, the optical lens satisfies the following conditional expression:
3<R1/R2<5；（2）
1.5<SAG1.1/SAG1< 1.8；（3）
where R1 represents the radius of curvature of the object-side surface of the first lens, R2 represents the radius of curvature of the image-side surface of the first lens, SAG1.1 represents the saggital height of the object-side surface of the first lens at the point of reverse curvature, and SAG1 represents the edge saggital height of the object-side surface of the first lens. When the conditional expressions (2) and (3) are met, the surface type and the position of the inflection point of the first lens can be reasonably controlled, the focal power of the first lens is enhanced, the system can well correct aberration under large aperture, meanwhile, the incident angle of each field ray can be reasonably controlled, and the distortion of the optical lens can be corrected.
As an embodiment, the optical lens satisfies the following conditional expression:
1.5mm<R2/tan(θ2)<1.8mm；（4）
where R2 denotes a radius of curvature of the image-side surface of the first lens, and θ 2 denotes a maximum surface inclination angle of the image-side surface of the first lens. When the conditional expression (4) is satisfied, the curvature radius of the image side surface of the first lens can be reasonably controlled, the aperture of the subsequent lens and the total length of the optical lens can be reduced, and the system volume miniaturization is realized.
As an embodiment, the optical lens satisfies the following conditional expression:
-1.9<R3/R4<-1.5；（5）
4×10-5mm/℃<f2×(dn/dt)2<7×10-5mm/℃；（6）
where R3 denotes a radius of curvature of an object-side surface of the second lens, R4 denotes a radius of curvature of an image-side surface of the second lens, f2 denotes a focal length of the second lens, and (dn/dt)2 denotes a temperature coefficient of refractive index of a material of the second lens. When the conditional expressions (5) and (6) are satisfied, the surface type of the second lens can be reasonably controlled, the sensitivity of the optical lens can be favorably reduced, and meanwhile, the high-temperature and low-temperature performance of the optical lens can be favorably improved by controlling the relation between the focal length of the second lens and the refractive index coefficient of the material.
As an embodiment, the optical lens satisfies the following conditional expression:
1.6<CT2/CT3<2.0；（7）
1.5<CT12/CT23<2.0；（8）
200<TTL/CT34<280；（9）
wherein CT2 denotes a center thickness of the second lens, CT3 denotes a center thickness of the third lens, CT12 denotes an air space between the first lens and the second lens on the optical axis, CT23 denotes an air space between the second lens and the third lens on the optical axis, CT34 denotes an air space between the third lens and the fourth lens on the optical axis, and TTL denotes an optical total length of the optical lens. When the conditional expressions (8) and (9) are met, the air intervals among the lenses are reasonably distributed, so that the sensitivity of the optical lens is favorably reduced, and the production yield of products is improved; meanwhile, the condition (7) is met, the central thicknesses of the second lens and the third lens can be reasonably distributed, so that the second lens has larger central thickness, and the optical lens is favorable for realizing day and night confocal performance.
As an embodiment, the optical lens satisfies the following conditional expression:
-1.3<f1/f3<-1.0；（10）
1.0<f3/f<1.2；（11）
-0.7<f3/f4<-0.5；（12）
where f denotes a focal length of the optical lens, f1 denotes a focal length of the first lens, f3 denotes a focal length of the third lens, and f4 denotes a focal length of the fourth lens. When the conditional expressions (10), (11) and (12) are satisfied, the correction of high-order aberration is favorably reduced and the resolution quality of the optical lens is improved by reasonably matching the focal power of each lens.
As an embodiment, the optical lens satisfies the following conditional expression:
-1.9<f4/f<-1.7；（13）
1.05<R6/R7<1.15；（14）
where f denotes a focal length of the optical lens, f4 denotes a focal length of the fourth lens, R6 denotes a radius of curvature of an image-side surface of the third lens, and R7 denotes a radius of curvature of an object-side surface of the fourth lens. When the conditional expressions (13) and (14) are satisfied, the focal length and the surface shape of the fourth lens can be reasonably controlled, the total length of the optical lens can be reduced, and the system size can be miniaturized.
As an embodiment, the optical lens satisfies the following conditional expression:
0.04<CT4/TTL<0.07；（15）
-0.18<SAG8/CT4<-0.13；（16）
where CT4 denotes the center thickness of the fourth lens, TTL denotes the total optical length of the optical lens, and SAG8 denotes the edge rise of the image side surface of the fourth lens. When the conditional expressions (15) and (16) are met, the thickness of the fourth lens can be reasonably controlled, the high-low temperature performance of the optical lens can be enhanced, and meanwhile, the resolution quality of the optical lens can be improved.
As an embodiment, the optical lens satisfies the following conditional expression:
1.3<BFL/f<1.5；（17）
where f denotes a focal length of the optical lens, and BFL denotes an optical back focus of the optical lens. When the conditional expression (17) is satisfied, the ratio of the optical back focus to the effective focal length can be reasonably controlled, and the total length of the optical lens can be reduced.
As an embodiment, the first lens, the third lens and the fourth lens may be aspheric lenses, and optionally, the first lens, the third lens and the fourth lens are plastic aspheric lenses, and the second lens is a glass spherical lens; adopt the structure of glass-plastic hybrid lens collocation, when making the camera lens have good formation of image quality, still have good thermal stability and less volume.
As an embodiment, when the lenses in the optical lens are aspherical lenses, each aspherical surface type may satisfy the following equation:
wherein z is the distance rise from the aspheric surface vertex when the aspheric surface is at the position with the height h along the optical axis direction, c is the paraxial curvature of the surface, k is the conic coefficient, A2iIs the aspheric surface type coefficient of 2i order.
The optical lens provided by the invention has the advantages that the four lenses with specific refractive power are adopted, the lens shapes and focal power combinations among the first lens, the second lens, the third lens and the fourth lens are reasonably matched, the structure is more compact on the premise of meeting the requirement of high pixel of the lens, the size miniaturization and the balance of wide visual angle are better realized, the high and low temperature performance and day and night confocal performance are better, and the use experience of a user can be effectively improved.
The invention is further illustrated below in the following examples. In various embodiments, the thickness, the curvature radius, and the material selection of each lens in the optical lens are different, and the specific differences can be referred to in the parameter tables of the various embodiments. The following examples are only preferred embodiments of the present invention, but the embodiments of the present invention are not limited only by the following examples, and any other changes, substitutions, combinations or simplifications which do not depart from the innovative points of the present invention should be construed as being equivalent substitutions and shall be included within the scope of the present invention.
First embodiment
Referring to fig. 1, a schematic structural diagram of an optical lens 100 according to a first embodiment of the present invention is shown, where the optical lens 100 sequentially includes, from an object side to an image plane along an optical axis: a first lens L1, an aperture stop ST, a second lens L2, a third lens L3, a fourth lens L4 and a filter G1.
The first lens element L1 has negative power, the object-side surface S1 of the first lens element is convex at paraxial region and has a point of inflection, and the image-side surface S2 of the first lens element is concave.
The second lens L2 has positive refractive power, and both the object-side surface S3 and the image-side surface S4 of the second lens are convex.
The third lens L3 has positive refractive power, and both the object-side surface S5 and the image-side surface S6 of the third lens are convex.
The fourth lens L4 has negative power, the object-side surface S7 of the fourth lens is concave, and the image-side surface S8 of the fourth lens is convex at the paraxial region.
The first lens element L1, the third lens element L3 and the fourth lens element L4 are all plastic aspheric lenses, and the second lens element L2 is a glass spherical lens.
In this embodiment, the distance from the retroflection point of the object-side surface of the first lens L1 to the optical axis is 2.749mm, and the rise is 0.1775 mm.
Referring to table 1, related parameters of each lens of the optical lens 100 according to the first embodiment of the invention are shown.
TABLE 1
Referring to table 2, the surface coefficients of the aspheric surfaces of the optical lens 100 according to the first embodiment of the present invention are shown.
TABLE 2
Referring to fig. 2 to 6, a vertical axis chromatic aberration graph, a center defocus graph of a visible light band, a center defocus graph of an infrared band, an MTF graph at a temperature of-40 ℃ and an MTF graph at a temperature of 80 ℃ of the optical lens 100 in the first embodiment are respectively shown.
The vertical axis chromatic aberration curve in fig. 2 shows chromatic aberration at different image heights on the image forming plane for the longest wavelength and the shortest wavelength, in which the horizontal axis shows the vertical axis chromatic aberration value (unit: μm) of each wavelength with respect to the center wavelength, and the vertical axis shows the normalized angle of view. As can be seen from fig. 2, the vertical chromatic aberration of the longest wavelength and the shortest wavelength are controlled within ± 2.5 microns, which indicates that the vertical chromatic aberration of the optical lens 100 is well corrected.
Fig. 3 and 4 show defocus curves of the lens in the central fields of view of the visible light band and the infrared 850nm band, respectively, in which the horizontal axis shows defocus positions (unit: μm) and the vertical axis shows MTF values. As can be seen from fig. 3 and 4, the defocus amount of the optical lens 100 in the central field of view of the infrared 850nm band is less than 0.01mm compared to the defocus curve of the visible band, which indicates that the optical lens 100 has better day and night confocal performance.
Fig. 5 and 6 show MTF graphs at low temperature-40 c and high temperature 80 c of the lens, respectively, in which the horizontal axis represents spatial frequency (unit: line pair/per millimeter (lp/mm)) and the vertical axis represents MTF values. As can be seen from fig. 5 and 6, the MTF values of the optical lens are greater than 0.5 in both the low temperature environment of-40 ℃ and the high temperature environment of 80 ℃, which indicates that the optical lens 100 has stable imaging performance and good resolution quality in the high and low temperature environments.
Second embodiment
The optical lens system provided in the second embodiment of the present invention has substantially the same structure as the optical lens system 100 provided in the first embodiment, and mainly differs in the radius of curvature and material selection of each lens.
In the present embodiment, the distance from the inflection point of the object-side surface of the first lens L1 to the optical axis is 2.770mm, and the rise is 0.1976 mm.
Referring to table 3, parameters related to each lens in an optical lens system according to a second embodiment of the present invention are shown.
TABLE 3
Referring to table 4, the surface coefficients of the aspheric surfaces of the optical lens according to the second embodiment of the present invention are shown.
TABLE 4
Referring to fig. 7 to 11, a vertical axis chromatic aberration graph, a center defocus graph of a visible light band, a center defocus graph of an infrared band, an MTF graph at a low temperature of-40 ℃ and an MTF graph at a high temperature of 80 ℃ of the optical lens in the second embodiment are respectively shown.
As can be seen from fig. 7, the vertical chromatic aberration of the longest wavelength and the shortest wavelength are controlled within ± 2.5 microns, which indicates that the vertical chromatic aberration of the optical lens in this embodiment is well corrected.
As can be seen from fig. 8 and 9, the defocus amount of the central field of view of the optical lens of this embodiment in the infrared 850nm band is less than 0.01mm compared to the defocus curve of the visible light band, which indicates that the optical lens of this embodiment has better day and night confocal performance.
As can be seen from fig. 10 and 11, the MTF values of the lens are greater than 0.45 in both the low temperature environment of-40 ℃ and the high temperature environment of 80 ℃, which indicates that the optical lens of the embodiment has stable imaging performance and good resolution quality in the high and low temperature environment.
Third embodiment
The optical lens system provided in the third embodiment of the present invention has substantially the same structure as the optical lens system 100 provided in the first embodiment, and mainly differs in the radius of curvature and material selection of each lens.
In this embodiment, the distance from the inflection point of the object-side surface of the first lens L1 to the optical axis is 2.644mm, and the rise is 0.1863 mm.
Referring to table 5, parameters related to each lens in an optical lens system according to a third embodiment of the present invention are shown.
TABLE 5
Referring to table 6, the surface coefficients of the aspheric surfaces of the optical lens according to the third embodiment of the present invention are shown.
TABLE 6
Referring to fig. 12 to 16, a vertical axis chromatic aberration graph, a center defocus graph of a visible light band, a center defocus graph of an infrared band, an MTF graph at a low temperature of-40 ℃ and an MTF graph at a high temperature of 80 ℃ of the optical lens in the third embodiment are respectively shown.
As can be seen from fig. 12, the vertical chromatic aberration of the longest wavelength and the shortest wavelength are controlled within ± 2.5 microns, which indicates that the vertical chromatic aberration of the optical lens of the embodiment is well corrected.
As can be seen from fig. 13 and 14, the defocus amount of the central field of view of the infrared 850nm band of this embodiment is less than 0.01mm compared to the defocus curve of the visible band, which indicates that the optical lens of this embodiment has better day and night confocal performance.
As can be seen from fig. 15 and 16, the MTF values of the lens are greater than 0.5 in both the low temperature environment of-40 ℃ and the high temperature environment of 80 ℃, which indicates that the optical lens of the embodiment has stable imaging performance and good resolution quality in the high and low temperature environments.
Fourth embodiment
The optical lens system provided in the fourth embodiment of the present invention has substantially the same structure as the optical lens system 100 provided in the first embodiment, but the difference is mainly in the radius of curvature and material selection of each lens.
In this embodiment, the distance from the inflection point of the object-side surface of the first lens L1 to the optical axis is 2.617mm, and the rise is 0.1827 mm.
Referring to table 7, parameters related to each lens in an optical lens system according to a fourth embodiment of the present invention are shown.
TABLE 7
Referring to fig. 8, a surface type coefficient of each aspheric surface of the optical lens 100 according to the fourth embodiment of the present invention is shown.
TABLE 8
Referring to fig. 17 to 21, a vertical axis chromatic aberration graph, a center defocus graph of a visible light band, a center defocus graph of an infrared band, an MTF graph at a temperature of-40 ℃ and an MTF graph at a temperature of 80 ℃ of the optical lens in the fourth embodiment are respectively shown.
As can be seen from fig. 17, the vertical chromatic aberration of the longest wavelength and the shortest wavelength are controlled within ± 2.5 microns, which indicates that the vertical chromatic aberration of the optical lens of the embodiment is well corrected.
As can be seen from fig. 18 and 19, the defocus amount of the central field of view of the infrared 850nm band of this embodiment is less than 0.01mm compared to the defocus curve of the visible band, which indicates that the optical lens of this embodiment has better day and night confocal performance.
As can be seen from fig. 20 and 21, the MTF values of the lens are greater than 0.5 in both the low temperature environment of-40 ℃ and the high temperature environment of 80 ℃, which indicates that the optical lens of the embodiment has stable imaging performance and good resolution quality in the high and low temperature environment.
Referring to table 9, optical characteristics corresponding to the optical lenses provided in the three embodiments are shown. The optical characteristics mainly include a focal length F, an F # of the optical lens, an entrance pupil diameter EPD, a total optical length TTL, and a field angle FOV of the optical lens, and a correlation value corresponding to each of the aforementioned conditional expressions.
TABLE 9
In summary, the optical lens provided by the invention has the following advantages:
(1) the four glass-plastic mixed lens structure with specific refractive power is adopted, and all the lenses are matched through specific surface shapes, so that the total length of the lens is effectively shortened, the volume of the lens is reduced, and the miniaturization of the system volume is realized.
(2) The field angle of the optical lens can reach 109 degrees, the optical distortion can be effectively corrected, the requirements of large field angle and high-definition imaging can be met, meanwhile, the optical lens can work in an environment with the temperature ranging from-40 ℃ to 80 ℃ and has good thermal stability in high and low temperature environments.
(3) The optical lens can realize that the maximum defocusing amount of a visible light wave band and an infrared wave band is less than 0.01mm, and has good day and night confocal performance.
Fifth embodiment
Referring to fig. 22, an imaging apparatus 500 according to a fifth embodiment of the present invention is shown, where the imaging apparatus 500 may include an imaging element 510 and an optical lens (e.g., the optical lens 100) in any of the embodiments described above. The imaging element 510 may be a CMOS (Complementary Metal Oxide Semiconductor) image sensor, and may also be a CCD (Charge Coupled Device) image sensor.
The imaging device 500 may be a monitoring camera, a vehicle-mounted camera, or any other electronic device equipped with the optical lens.
The imaging device 500 provided in the embodiment of the application includes the optical lens 100, and since the optical lens 100 has the advantages of large field angle, high pixel, day and night confocal property, good thermal stability, and relatively low cost, the imaging device 500 having the optical lens 100 also has the advantages of large field angle, high pixel, day and night confocal property, good thermal stability, and relatively low cost.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. An optical lens, wherein the number of lenses in the optical lens is 4, and the optical lens sequentially includes, from an object side to an image plane along an optical axis:
a first lens having a negative optical power, an object-side surface of the first lens being convex at a paraxial region and having at least one inflection point, an image-side surface of the first lens being concave;
a diaphragm;
the second lens is provided with positive focal power, and the object side surface and the image side surface of the second lens are convex surfaces;
a third lens having a positive optical power, the third lens having convex object and image side surfaces;
a fourth lens element having a negative optical power, the fourth lens element having a concave object-side surface and a convex image-side surface at a paraxial region;
the first lens, the third lens and the fourth lens are plastic aspheric lenses, and the second lens is a glass spherical lens;
the optical lens satisfies the following conditional expression:
1.5mm<R2/tan(θ2)<1.8mm；
where R2 denotes a radius of curvature of an image-side surface of the first lens, and θ 2 denotes a maximum surface inclination angle of the image-side surface of the first lens.
2. An optical lens according to claim 1, characterized in that the optical lens satisfies the following conditional expression:
-2.6<f1/EPD<-2.4；
where f1 denotes a focal length of the first lens, and EPD denotes an entrance pupil diameter of the optical lens.
3. An optical lens according to claim 1, characterized in that the optical lens satisfies the following conditional expression:
3<R1/R2<5；
1.5<SAG1.1/SAG1<1.8；
wherein R1 represents a radius of curvature of the object-side surface of the first lens, R2 represents a radius of curvature of the image-side surface of the first lens, SAG1.1 represents a sagittal height of the object-side surface of the first lens at the point of reverse curvature, and SAG1 represents an edge sagittal height of the object-side surface of the first lens.
4. An optical lens according to claim 1, characterized in that the optical lens satisfies the following conditional expression:
-1.9<R3/R4<-1.5；
4×10-5mm/℃<f2×(dn/dt)2<7×10-5mm/℃；
wherein R3 denotes a radius of curvature of an object-side surface of the second lens, R4 denotes a radius of curvature of an image-side surface of the second lens, f2 denotes a focal length of the second lens, and (dn/dt)2 denotes a material refractive index temperature coefficient of the second lens.
5. An optical lens according to claim 1, characterized in that the optical lens satisfies the following conditional expression:
1.6< CT2/CT3<2.0；
1.5< CT12/CT23<2.0；
200<TTL/CT34<280；
wherein CT2 denotes a center thickness of the second lens, CT3 denotes a center thickness of the third lens, CT12 denotes an air space between the first lens and the second lens on an optical axis, CT23 denotes an air space between the second lens and the third lens on an optical axis, CT34 denotes an air space between the third lens and the fourth lens on an optical axis, and TTL denotes a total optical length of the optical lens.
6. An optical lens according to claim 1, characterized in that the optical lens satisfies the following conditional expression:
-1.3<f1/f3<-1.0；
1.0<f3/f<1.2；
-0.7<f3/f4<-0.5；
where f denotes a focal length of the optical lens, f1 denotes a focal length of the first lens, f3 denotes a focal length of the third lens, and f4 denotes a focal length of the fourth lens.
7. An optical lens according to claim 1, characterized in that the optical lens satisfies the following conditional expression:
-1.9<f4/f<-1.7；
1.05<R6/R7<1.15；
where f denotes a focal length of the optical lens, f4 denotes a focal length of the fourth lens, R6 denotes a radius of curvature of an image-side surface of the third lens, and R7 denotes a radius of curvature of an object-side surface of the fourth lens.
8. An optical lens according to claim 1, characterized in that the optical lens satisfies the following conditional expression:
0.04<CT4/TTL<0.07；
-0.18<SAG8/CT4<-0.13；
wherein CT4 denotes a center thickness of the fourth lens, TTL denotes an optical total length of the optical lens, and SAG8 denotes an edge rise of an image side surface of the fourth lens.
9. An optical lens according to claim 1, characterized in that the optical lens satisfies the following conditional expression:
1.3<BFL/f<1.5；
wherein f represents a focal length of the optical lens, and BFL represents an optical back focus of the optical lens.
10. An imaging apparatus comprising the optical lens according to any one of claims 1 to 9 and an imaging element for converting an optical image formed by the optical lens into an electric signal.
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| CN114355559A (en) * | 2021-12-29 | 2022-04-15 | 福建福光股份有限公司 | Large-aperture high-resolution optical lens |
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