CN113311572B - Infrared imaging lens and imaging device - Google Patents
Infrared imaging lens and imaging device Download PDFInfo
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- CN113311572B CN113311572B CN202110867848.4A CN202110867848A CN113311572B CN 113311572 B CN113311572 B CN 113311572B CN 202110867848 A CN202110867848 A CN 202110867848A CN 113311572 B CN113311572 B CN 113311572B
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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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- 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
- G02B13/14—Optical objectives specially designed for the purposes specified below for use with infrared or ultraviolet radiation
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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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- G02B7/00—Mountings, adjusting means, or light-tight connections, for optical elements
- G02B7/02—Mountings, adjusting means, or light-tight connections, for optical elements for lenses
- G02B7/028—Mountings, adjusting means, or light-tight connections, for optical elements for lenses with means for compensating for changes in temperature or for controlling the temperature; thermal stabilisation
Abstract
The invention discloses an infrared imaging lens and imaging equipment, wherein the infrared imaging lens sequentially comprises a first group with negative focal power, a diaphragm and a second group with positive focal power from an object side to an imaging surface along an optical axis; the first group comprises in order from the object side to the imaging plane: a first lens element having a negative refractive power, the object-side surface of which is concave at the paraxial region and the image-side surface of which is concave; a second lens with positive focal power, wherein the object side surface of the second lens is a convex surface, and the image side surface of the second lens is a concave surface; the second group comprises in order from the object side to the imaging plane: a third lens having a positive refractive power, both the object-side surface and the image-side surface of the third lens being convex; a fourth lens having a positive refractive power, both the object-side surface and the image-side surface of the fourth lens being convex; and the object side surface of the fifth lens with positive focal power is a convex surface. The infrared imaging lens has the advantages of large clear aperture, large field angle and stable optical performance at the temperature of minus 40 ℃ to plus 105 ℃.
Description
Technical Field
The invention relates to the technical field of imaging lenses, in particular to an infrared imaging lens and imaging equipment.
Background
The Driver monitoring System (abbreviated as DMS) can effectively standardize the driving behavior of the Driver, reduce accidents caused by human errors and protect the Driver for driving safety. In recent years, with the enhancement of safety awareness of automobile driving and the continuous improvement of related laws of DMS at home and abroad, the number of DMS cameras equipped in automobiles is rapidly increasing. Meanwhile, a ToF (Time-of-Flight) lens widely used in a mobile phone performs imaging by using infrared light to measure distance and depth data, has unique advantages in the aspects of depth measurement, face recognition, motion capture and the like, is an accurate and safe recognition mode, and is very suitable for being applied to a DMS.
With the deep fusion of the ToF technology and the DMS technology, a ToF lens using infrared imaging starts to reveal a corner in an intelligent driving system. Because the application environment of the automobile is complicated and changeable and the safety performance requirement is higher, higher requirements are provided for the lens carried in the DMS, stronger environmental adaptability is required to be provided so as to ensure that the lens can keep better resolving power under high and low temperature environments, and a larger aperture and an ultra-wide visual angle are required to be provided so as to better and more comprehensively capture the facial information and driving behaviors of a driver. However, most of the infrared imaging lenses in the market have the defects of large temperature drift, small clear aperture, small field angle and the like, and the use requirement of the DMS is difficult to meet.
Disclosure of Invention
Therefore, the invention aims to provide an infrared imaging lens and an imaging device, which at least have the advantages of large clear aperture, large field angle and stable optical performance in the temperature of minus 40 ℃ to plus 105 ℃.
The embodiment of the invention implements the above object by the following technical scheme.
In a first aspect, the present invention provides an infrared imaging lens, sequentially including, from an object side to an imaging surface along an optical axis: a first group with negative focal power, a diaphragm, a second group with positive focal power; the first group comprises the following components in sequence from an object side to an imaging surface: a first lens having a negative optical power, an object-side surface of the first lens being concave at a paraxial region, an image-side surface of the first lens being concave; the second lens is provided with positive focal power, the object side surface of the second lens is a convex surface, and the image side surface of the second lens is a concave surface; the second group comprises the following components in sequence from the object side to the imaging surface: a third lens having a positive optical power, the third lens having convex object and image side surfaces; the fourth lens is provided with positive focal power, and the object side surface and the image side surface of the fourth lens are convex surfaces; a fifth lens having a positive optical power, an object side surface of the fifth lens being convex; the first lens is a glass aspheric lens, and the second lens, the third lens, the fourth lens and the fifth lens are all glass aspheric lenses.
In a second aspect, the present invention provides an imaging device, including an imaging element and the infrared imaging lens provided in the first aspect, wherein the imaging element is configured to convert an optical image formed by the infrared imaging lens into an electrical signal.
Compared with the prior art, the infrared imaging lens and the imaging equipment provided by the invention have the advantages that the structure of five full-glass lenses is adopted, the infrared spectrum optimization design is adopted, the lens can clearly image in the infrared band of 900 nm-980 nm through the reasonable matching of one negative focal power lens and four positive focal power lenses, and meanwhile, the large field angle exceeding 140 degrees is realized, and the infrared rays in a larger range can be collected; due to the adoption of the all-glass lens, the lens has good thermal stability, and can effectively compensate focus offset caused by temperature change; due to the improvement of the processing technical precision of the aspheric lens, the negative focal power is concentrated on the first lens, so that the first lens cannot cause overlarge sensitivity, and the lens has an overlarge aperture which is not more than 1.5 by reasonably setting the focal power and the surface type of the first lens, so that the high-definition imaging performance is realized in the light and dark environment; because the focal power of the lens groups before and after the diaphragm and the surface shape position of each lens are reasonably arranged, the aberration of the lens is well corrected, and high-definition resolving power is achieved.
Drawings
Fig. 1 is a schematic structural diagram of an infrared imaging lens according to a first embodiment of the present invention;
FIG. 2 is a field curvature graph of an infrared imaging lens according to a first embodiment of the present invention;
FIG. 3 is a graph illustrating relative illuminance of an infrared imaging lens according to a first embodiment of the present invention;
FIG. 4 is a MTF curve of the infrared imaging lens of the first embodiment of the present invention in a wavelength band of 900nm to 980 nm;
fig. 5 is a schematic structural diagram of an infrared imaging lens according to a second embodiment of the present invention;
FIG. 6 is a field curvature graph of an infrared imaging lens according to a second embodiment of the present invention;
FIG. 7 is a graph illustrating relative illuminance of an IR imaging lens according to a second embodiment of the present invention;
FIG. 8 is a MTF curve of the infrared imaging lens of the second embodiment of the present invention in a wavelength range from 900nm to 980 nm;
fig. 9 is a schematic structural diagram of an infrared imaging lens according to a third embodiment of the present invention;
fig. 10 is a field curvature graph of an infrared imaging lens according to a third embodiment of the present invention;
FIG. 11 is a graph illustrating relative illuminance of an IR imaging lens according to a third embodiment of the present invention;
FIG. 12 is a MTF curve of an infrared imaging lens of a third embodiment of the present invention in a wavelength band of 900nm to 980 nm;
fig. 13 is a schematic structural diagram of an infrared imaging lens according to a fourth embodiment of the present invention;
fig. 14 is a field curvature graph of an infrared imaging lens according to a fourth embodiment of the present invention;
FIG. 15 is a graph illustrating relative illuminance of an IR imaging lens according to a fourth embodiment of the present invention;
FIG. 16 is a MTF curve of an infrared imaging lens of a fourth embodiment of the present invention in a wavelength band of 900nm to 980 nm;
fig. 17 is a schematic configuration diagram of an image forming apparatus according to 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 infrared imaging lens, which sequentially comprises a first group with negative focal power, a diaphragm, a second group with positive focal power and an optical filter from an object side to an imaging surface along an optical axis.
The first group comprises the following components in sequence from an object side to an imaging surface: a first lens having a negative optical power, an object-side surface of the first lens being concave at a paraxial region, an image-side surface of the first lens being concave; the second lens is provided with positive focal power, the object side surface of the second lens is a convex surface, and the image side surface of the second lens is a concave surface;
the diaphragm is arranged between the first group and the second group;
the second group comprises the following components in sequence from the object side to the imaging surface: a third lens having a positive optical power, the third lens having convex object and image side surfaces; the fourth lens is provided with positive focal power, and the object side surface and the image side surface of the fourth lens are convex surfaces; the lens comprises a fifth lens with positive focal power, wherein the object side surface of the fifth lens is a convex surface, and the image side surface of the fifth lens is a convex surface or a concave surface;
and the optical filter is arranged between the second group and the imaging surface.
The first lens is a glass aspheric lens, and the second lens, the third lens, the fourth lens and the fifth lens are all glass aspheric lenses.
Further, the infrared imaging lens satisfies the conditional expression:
2.6<f/(IH/tanθ)<3.2；（1）
1.4 mm/rad<IH/θ<1.53 mm/rad；（2）
wherein f represents the effective focal length of the infrared imaging lens, theta represents the maximum half field angle of the infrared imaging lens, and IH represents the maximum true half image height of the infrared imaging lens. The conditional expressions (1) and (2) are respectively the optical distortion and the f-theta distortion of the infrared imaging lens, and the distortion of the lens can be effectively improved by meeting the conditional expressions.
In some embodiments, the infrared imaging lens satisfies the following conditional expression:
0.16<BFL/TTL<0.19；（3）
wherein, TTL represents the optical total length of the infrared imaging lens, and BFL represents the optical back focus of the infrared imaging lens. The condition formula (3) is met, so that the lens has larger optical back focus, and the assembly difficulty between the lens and the imaging chip is reduced; meanwhile, the lens has smaller optical total length, and the miniaturization of products is realized.
In some embodiments, the infrared imaging lens satisfies the following conditional expression:
0.05<ENPD/TTL<0.11；（4）
the ENPD represents the entrance pupil diameter of the infrared imaging lens, and the TTL represents the total optical length of the infrared imaging lens. Satisfying the above conditional expression (4), the entrance pupil position of the lens can be closer to the object side end of the lens, which is beneficial to improving the relative illumination of the lens.
In some embodiments, the infrared imaging lens satisfies the following conditional expression:
-1.55＜φI/φII＜-1.2；（5）
wherein phi isIDenotes the power of the first group, phiIIRepresenting the optical power of the second group. The positive and negative focal power collocation of the first group and the second group is reasonably distributed to be beneficial to correcting the field curvature of the system; when phi isI/φIIWhen the value of (b) exceeds the lower limit, the difference between positive and negative powers of the front and rear lens groups becomes too large, which is disadvantageous for correction of curvature of field.
In some embodiments, the infrared imaging lens satisfies the following conditional expression:
-1.3<f1/f<-1；（6）
-40 mm2<R1×R2<-15 mm2；（7）
-12<R1/R2<0；（8）
where f1 denotes an effective focal length of the first lens, f denotes an effective focal length of the infrared imaging lens, R1 denotes a radius of curvature of an object-side surface of the first lens, and R2 denotes a radius of curvature of an image-side surface of the first lens. Satisfying the conditional expressions (6) to (8), the divergence angle of the light after passing through the first lens can be increased by controlling the focal length and the surface type structure of the first lens, and the aperture of the light beam is enlarged, so that the lens has the effect of large aperture not greater than 1.5; if the value of R1 × R2 exceeds the upper limit, the light divergence angle is too small, and the large aperture effect cannot be achieved; if the value of R1 × R2 exceeds the lower limit, the divergence angle of light is too large, which is not favorable for reducing the aperture of the lens and increasing the difficulty of assembling the lens.
In some embodiments, the infrared imaging lens satisfies the following conditional expression:
0<φ2/φ<0.20；（9）
0.3＜φ3/φ＜0.55；（10）
0.24＜φ4/φ＜0.35；（11）
0.15＜φ5/φ＜0.20；（12）
wherein, phi 2 represents the focal power of the second lens, phi 3 represents the focal power of the third lens, phi 4 represents the focal power of the fourth lens, phi 5 represents the focal power of the fifth lens, and phi represents the focal power of the infrared imaging lens. Satisfy above-mentioned conditional expression (9), can effectively reduce the exit angle through first lens light for exit light and optical axis contained angle after the second lens reduce, and exit light is gently to follow-up lens transition, so that follow-up optical system corrects optical aberration. The positive focal power of the lens can be reasonably shared by the third lens and the fourth lens by satisfying the conditional expressions (10) and (11), the sensitivity of a single lens is reduced, and the assembly yield is improved. When the conditional expression (12) is satisfied, astigmatism of the lens can be effectively corrected, and the resolving power of the lens can be improved. The conditional expressions (6) and (9) to (12) show that the infrared imaging lens not only can increase the relative illumination of the lens, but also can enable light to stably transit to an image plane, reduce aberration and improve imaging quality through reasonable collocation of the first negative focal power lens and the four back positive focal power lenses.
In some embodiments, the infrared imaging lens satisfies the following conditional expression:
0.2<T2/TTL<0.3；（13）
0.2< (T3+T4+T5)/TTL<0.4；（14）
0.45<T12/T45<0.9；（15）
wherein TTL denotes an optical total length of the infrared imaging lens, T2, T3, T4 and T5 denote center thicknesses of the second lens, the third lens, the fourth lens and the fifth lens, respectively, T12 denotes an air space between the first lens and the second lens on an optical axis, and T45 denotes an air space between the fourth lens and the fifth lens on the optical axis. Satisfying the above conditional expressions (13) to (15), the thickness of each lens and the air space between each lens can be set reasonably, the sensitivity of the air space between each lens is reduced, and the assembly yield is improved.
In some embodiments, the applicable spectral range of the infrared imaging lens is 900nm to 980nm, which can meet the imaging characteristics of a ToF lens and realize dynamic identification and image capture in a specific infrared band.
In some embodiments, the infrared imaging lens satisfies the following conditional expression:
5×10-6/℃<(dn/dt)3+(dn/dt)4<10×10-6/℃；（16）
wherein (dn/dt)3 represents a temperature coefficient of refractive index of a material of the third lens, and (dn/dt)4 represents a temperature coefficient of refractive index of a material of the fourth lens. The condition (16) is satisfied, and the lens has small focus offset in the environment of minus 40 ℃ to plus 125 ℃ and stable imaging performance by reasonably distributing the thermal expansion coefficients of the lenses.
The invention is further illustrated below in the following examples. In each embodiment, the thickness, the curvature radius and the material selection part of each lens in the infrared imaging lens are different, and specific differences can be referred to in a parameter table of each embodiment. 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.
The aspheric surface shape of the infrared imaging lens in each embodiment of the invention satisfies the following equation:
wherein z represents the distance in the optical axis direction from the curved surface vertex, c represents the curvature of the curved surface vertex, K represents the conic coefficient, h represents the distance from the optical axis to the curved surface, and B, C, D, E and F represent the fourth, sixth, eighth, tenth and twelfth order curved surface coefficients, respectively.
First embodiment
Referring to fig. 1, a schematic structural diagram of an infrared imaging lens 100 according to a first embodiment of the present invention is shown, in which the infrared imaging lens 100 includes, in order from an object side to an image plane, a first group I with negative power, a diaphragm ST, a second group II with positive power, and a filter G1.
The first group I comprises in order from the object side to the imaging plane: a first lens L1 having a negative power, the object-side surface S1 of the first lens being concave at the paraxial region and the image-side surface S2 of the first lens being concave; a second lens L2 with positive power, the object-side surface S3 of the second lens being convex, the image-side surface S4 of the second lens being concave;
the stop ST is provided between the second lens L2 and the third lens L3;
the second group II includes, in order from the object side to the image plane: a third lens L3 having positive optical power, the object-side surface S5 and the image-side surface S6 of the third lens being convex; a fourth lens L4 having positive optical power, the object-side surface S7 and the image-side surface S8 of the fourth lens being convex; the fifth lens L5 having positive optical power, the object-side surface S9 and the image-side surface S10 of the fifth lens are convex.
The first lens L1 is a glass aspheric lens, and the second lens L2, the third lens L3, the fourth lens L4 and the fifth lens L5 are all glass aspheric lenses.
Specifically, the parameters related to each lens in the infrared imaging lens 100 in this embodiment are shown in table 1.
TABLE 1
The aspheric parameters of the infrared imaging lens 100 in this embodiment are shown in table 2.
TABLE 2
In the present embodiment, the field curvature curve, the relative illumination curve and the MTF curve in the operating band of the infrared imaging lens 100 are respectively shown in fig. 2, fig. 3 and fig. 4.
As can be seen from fig. 2, the field curvature of the infrared imaging lens 100 in the working wavelength band is within ± 0.05mm, and the difference between the field curvatures in the meridional direction and the sagittal direction of the same wavelength does not exceed 0.05mm, which indicates that the field curvature of the lens is well corrected.
As can be seen from fig. 3, the relative illumination of the infrared imaging lens 100 is above 80%, which indicates that the central illumination of the lens is close to the edge illumination, indicating that the lens has a higher resolution in the entire field of view.
As can be seen from FIG. 4, the infrared imaging lens 100 has an MTF of 88% in a central field of view at 50lp/mm and an MTF of 63% in an edge field of view at 50lp/mm within an operating band of 900 nn-980 nm. The lens has high-definition resolution within the working band.
Second embodiment
Referring to fig. 5, a structural diagram of an infrared imaging lens 200 according to a second embodiment of the present invention is shown, where the structure of the infrared imaging lens 200 in this embodiment is substantially the same as that of the infrared imaging lens 100 in the first embodiment, but the difference is that the curvature radius, thickness, and material selection of each lens of the optical imaging lens in this embodiment are different, and specific relevant parameters of each lens are shown in table 3.
TABLE 3
The aspheric parameters of the infrared imaging lens 200 in this embodiment are shown in table 4.
TABLE 4
In the present embodiment, the field curvature curve, the relative illumination curve and the MTF curve in the operating band of the infrared imaging lens 200 are respectively shown in fig. 6, fig. 7 and fig. 8.
As can be seen from fig. 6, the field curvature of the infrared imaging lens 200 in the working wavelength band is within ± 0.05mm, and the difference between the field curvatures in the meridional direction and the sagittal direction of the same wavelength does not exceed 0.05mm, which indicates that the field curvature of the lens is well corrected.
As can be seen from fig. 7, the relative illumination of the infrared imaging lens 200 is above 80%, which indicates that the central illumination of the lens is close to the edge illumination, indicating that the lens has a higher resolution in the entire field of view.
As can be seen from FIG. 8, in the working band of 900 nn-980 nm, the MTF of the central field of view of the infrared imaging lens 200 reaches 90% at 50lp/mm, and the MTF of the edge field of view of the infrared imaging lens 200 reaches 63% at 50 lp/mm. The lens has high-definition resolution within the working band.
Third embodiment
Referring to fig. 9, a structural diagram of an infrared imaging lens 300 according to a third embodiment of the present invention is shown, where the structure of the infrared imaging lens 300 in this embodiment is substantially the same as that of the infrared imaging lens 100 in the first embodiment, and the difference is that an image-side surface S10 of a fifth lens of the infrared imaging lens 300 in this embodiment is a concave surface, and curvature radii, thicknesses, and material choices of the lenses are different, and specific relevant parameters of the lenses are shown in table 5.
TABLE 5
The aspheric parameters of the infrared imaging lens 300 in this embodiment are shown in table 6.
TABLE 6
In the present embodiment, the field curvature curve, the relative luminance curve and the MTF curve in the operating band of the infrared imaging lens 300 are respectively shown in fig. 10, fig. 11 and fig. 12.
As can be seen from fig. 10, the field curvature of the infrared imaging lens 300 in the working band is within ± 0.05mm, and the difference between the field curvatures in the meridional direction and the sagittal direction of the same wavelength does not exceed 0.05mm, which indicates that the field curvature of the lens is well corrected.
As can be seen from fig. 11, the relative illumination of the infrared imaging lens 300 is changed to be more than 85%, which indicates that the central illumination of the lens is close to the edge illumination, indicating that the lens has a higher resolution in the entire field of view.
As can be seen from FIG. 12, the infrared imaging lens 300 has an MTF of 80% in a central field of view at 50lp/mm and an MTF of 58% in an edge field of view at 50lp/mm within an operating band of 900 nn-980 nm. The lens has high-definition resolution within the working band.
Fourth embodiment
Referring to fig. 13, a structural diagram of an infrared imaging lens 400 according to a fourth embodiment of the present invention is shown, in which the infrared imaging lens 400 in this embodiment is substantially the same as the infrared imaging lens 100 in the first embodiment, except that an image side surface S10 of a fifth lens of the infrared imaging lens 400 in this embodiment is a concave surface, and curvature radii, thicknesses, and material choices of the lenses are different, and specific relevant parameters of the lenses are shown in table 7.
TABLE 7
The aspheric parameters of the infrared imaging lens 400 in this embodiment are shown in table 8.
TABLE 8
In the present embodiment, the field curvature curve, the relative illuminance curve and the MTF curve in the operating band of the infrared imaging lens 400 are respectively shown in fig. 14, fig. 15 and fig. 16.
As can be seen from fig. 14, the field curvature of the infrared imaging lens 400 in the working band is within ± 0.05mm, and the difference between the field curvatures in the meridional direction and the sagittal direction of the same wavelength does not exceed 0.05mm, which indicates that the field curvature of the lens is well corrected.
As can be seen from fig. 15, the relative illumination of the infrared imaging lens 400 is changed to be more than 85%, which indicates that the central illumination of the lens is close to the edge illumination, indicating that the lens has a higher resolution in the entire field of view.
As can be seen from FIG. 16, the infrared imaging lens 400 has an MTF of 78% in a central field of view at 50lp/mm and an MTF of 60% in an edge field of view at 50lp/mm within an operating band of 900 nn-980 nm. The lens has high-definition resolution within the working band.
Table 9 shows the four embodiments and their corresponding optical characteristics, including the finite focal length F, F #, the field angle 2 θ, the total optical length TTL, and the values corresponding to each of the foregoing conditional expressions.
TABLE 9
In conclusion, the infrared imaging lens provided by the invention all achieve the following optical indexes: (1) the field angle 2 theta is more than or equal to 140 degrees; (2) total optical length TTL <14 mm; (3) F # is < 1.5;
by integrating the above embodiments, the infrared imaging lens provided by the invention has the following advantages:
(1) the infrared imaging lens provided by the invention is designed by adopting five glass lenses, so that the temperature drift can be effectively reduced, and the lens has excellent optical performance in the environment of minus 40 ℃ to plus 105 ℃.
(2) According to the infrared imaging lens provided by the invention, the ratio of focal powers of the front lens group and the rear lens group of the diaphragm is reasonably distributed, so that the curvature of field of the system is well corrected, and the infrared imaging lens has clear resolving power; the lens group in front of the diaphragm is mainly responsible for collecting light rays, and converts large-angle light rays into gentle light rays to be incident to the optical system, so that the field curvature can be corrected conveniently; when the ratio of focal powers of the front lens group and the rear lens group of the diaphragm is in a specific range, the curvature of field of the lens can be effectively corrected, and the resolving power is improved.
(3) According to the infrared imaging lens, the focal power and the surface type of the first lens are reasonably controlled, so that the lens has a large clear aperture and excellent optical performance in light and dark environments; meanwhile, the first lens adopts an aspheric surface design, so that the number of the lenses is greatly reduced, and the miniaturization of the lens is realized.
Fifth embodiment
Referring to fig. 17, an imaging device 500 according to a fifth embodiment of the present invention is shown, where the imaging device 500 may include an imaging element 510 and an infrared imaging lens (e.g., infrared imaging 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 vehicle-mounted camera, a monitoring device, or any other electronic device equipped with the infrared imaging lens.
The imaging device 500 provided by the embodiment of the application comprises the infrared imaging lens 100, and as the infrared imaging lens 100 has the advantages of large clear aperture, large field angle and stable optical performance in the temperature range from-40 ℃ to +105 ℃, the imaging device 500 with the infrared imaging lens 100 also has the advantages of large clear aperture, large field angle and stable optical performance in the temperature range from-40 ℃ to +105 ℃.
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 (11)
1. An infrared imaging lens is characterized in that the number of lenses in the infrared imaging lens is 5, and the infrared imaging lens sequentially comprises a first group with negative focal power, a diaphragm and a second group with positive focal power from an object side to an imaging surface along an optical axis;
the number of the lenses in the first group is 2, and the lenses in the first group sequentially comprise from the object side to the imaging plane: a first lens having a negative optical power, an object-side surface of the first lens being concave at a paraxial region, an image-side surface of the first lens being concave; the second lens is provided with positive focal power, the object side surface of the second lens is a convex surface, and the image side surface of the second lens is a concave surface;
the number of the lenses in the second group is 3, and the lenses in the second group sequentially include from the object side to the imaging plane: a third lens having a positive optical power, the third lens having convex object and image side surfaces; the fourth lens is provided with positive focal power, and the object side surface and the image side surface of the fourth lens are convex surfaces; a fifth lens having a positive optical power, an object side surface of the fifth lens being convex;
the first lens is a glass aspheric lens, and the second lens, the third lens, the fourth lens and the fifth lens are glass spherical lenses;
the infrared imaging lens meets the following conditional expression:
0.05<ENPD/TTL<0.11；
the ENPD represents the entrance pupil diameter of the infrared imaging lens, and the TTL represents the total optical length of the infrared imaging lens.
2. The infrared imaging lens of claim 1, characterized in that the infrared imaging lens satisfies the following conditional expression:
2.6<f/(IH/tanθ)<3.2；
1.4mm/rad <IH/θ <1.53mm/rad；
wherein f represents the effective focal length of the infrared imaging lens, IH represents the maximum real half-image height of the infrared imaging lens, and theta represents the maximum half-field angle of the infrared imaging lens.
3. The infrared imaging lens of claim 1, characterized in that the infrared imaging lens satisfies the following conditional expression:
0.16<BFL/TTL<0.19；
wherein, TTL represents the optical total length of the infrared imaging lens, and BFL represents the optical back focus of the infrared imaging lens.
4. The infrared imaging lens of claim 1, characterized in that the infrared imaging lens satisfies the following conditional expression:
-1.55＜φI/φII＜-1.2；
wherein phi isIRepresents the optical power of the first group, phiIIRepresenting the optical power of the second group.
5. The infrared imaging lens of claim 1, characterized in that the infrared imaging lens satisfies the following conditional expression:
-1.3<f1/f<-1；
-40 mm2<R1×R2<-15 mm2；
-12<R1/R2<0；
wherein f1 denotes an effective focal length of the first lens, f denotes an effective focal length of the infrared imaging lens, R1 denotes a radius of curvature of an object-side surface of the first lens, and R2 denotes a radius of curvature of an image-side surface of the first lens.
6. The infrared imaging lens of claim 1, characterized in that the infrared imaging lens satisfies the following conditional expression:
0<φ2/φ<0.20；
0.3＜φ3/φ＜0.55；
0.24＜φ4/φ＜0.35；
0.15＜φ5/φ＜0.20；
wherein φ 2 represents the focal power of the second lens, φ 3 represents the focal power of the third lens, φ 4 represents the focal power of the fourth lens, φ 5 represents the focal power of the fifth lens, and φ represents the focal power of the infrared imaging lens.
7. The infrared imaging lens of claim 1, characterized in that the infrared imaging lens satisfies the following conditional expression:
0.2<T2/TTL<0.3；
0.2< (T3+T4+T5)/TTL<0.4；
0.45<T12/T45<0.9；
wherein TTL denotes an optical total length of the infrared imaging lens, T2, T3, T4 and T5 denote center thicknesses of the second lens, the third lens, the fourth lens and the fifth lens, respectively, T12 denotes an air space between the first lens and the second lens on an optical axis, and T45 denotes an air space between the fourth lens and the fifth lens on the optical axis.
8. The infrared imaging lens as claimed in claim 1, wherein the applicable spectrum range of the infrared imaging lens is 900nm to 980 nm.
9. The infrared imaging lens of claim 1, characterized in that the infrared imaging lens satisfies the following conditional expression:
5×10-6/℃<(dn/dt)3+(dn/dt)4< 10×10-6/℃；
wherein (dn/dt)3 represents a temperature coefficient of refractive index of a material of the third lens, and (dn/dt)4 represents a temperature coefficient of refractive index of a material of the fourth lens.
10. The infrared imaging lens as claimed in claim 1, wherein the image side surface of the fifth lens element is convex or concave.
11. An imaging apparatus comprising the infrared imaging lens according to any one of claims 1 to 10, and an imaging element for converting an optical image formed by the infrared imaging lens into an electric signal.
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