CN113589475A - Projection lens suitable for 3D face recognition - Google Patents

Projection lens suitable for 3D face recognition Download PDF

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CN113589475A
CN113589475A CN202110752167.3A CN202110752167A CN113589475A CN 113589475 A CN113589475 A CN 113589475A CN 202110752167 A CN202110752167 A CN 202110752167A CN 113589475 A CN113589475 A CN 113589475A
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lens
light source
projection
projection lens
spot
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CN113589475B (en
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杨小威
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Alipay Hangzhou Information Technology Co Ltd
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Alipay Hangzhou Information Technology Co Ltd
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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
    • 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
    • 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
    • G02B13/0035—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 three lenses
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B13/00—Optical objectives specially designed for the purposes specified below
    • G02B13/16—Optical objectives specially designed for the purposes specified below for use in conjunction with image converters or intensifiers, or for use with projectors, e.g. objectives for projection TV
    • 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 embodiment of the specification discloses a projection lens suitable for 3D face recognition. The projection lens comprises a projection light source, and a first lens, a second lens and a third lens which are sequentially arranged along the optical axis direction of the projection light source. The first lens element with positive refractive power has two convex surfaces; the second lens element with negative refractive power has a concave surface near the light source and a convex surface far from the light source; the third lens element with positive refractive power has a concave surface near the light source and a convex surface far from the light source.

Description

Projection lens suitable for 3D face recognition
Technical Field
The specification relates to the technical field of face recognition, in particular to a projection lens suitable for 3D face recognition.
Background
With the development of technology and the enhancement of requirements of people on data security, the application of improving data security is more and more extensive by carrying out identity verification through a face recognition technology.
Currently, the commonly used face recognition techniques include: the living body detection and recognition are performed through blinking, shaking and other actions, the face recognition (for example, the face recognition based on 3D structured light) is performed through constructing a three-dimensional space based on the face, and the like. When a three-dimensional space based on a human face is constructed by adopting the projection lens, the projection lens is possibly influenced by factors such as temperature and the like, so that the constructed three-dimensional space generates deviation.
Based on this, a more accurate projection lens suitable for 3D face recognition is required.
Disclosure of Invention
One or more embodiments of the present disclosure provide a projection lens suitable for 3D face recognition, so as to solve the following technical problems: a more accurate projection lens suitable for 3D face recognition is required.
To solve the above technical problem, one or more embodiments of the present specification are implemented as follows:
one or more embodiments of the present specification provide a projection lens suitable for 3D face recognition, including a projection light source, and a first lens, a second lens, and a third lens sequentially arranged along an optical axis direction of the projection light source;
the first lens element with positive refractive power has two convex surfaces;
the second lens has negative refractive power, and the surface of the second lens, which is close to the light source, is a concave surface, and the surface of the second lens, which is far from the light source, is a convex surface;
the third lens element with positive refractive power has a concave surface near the light source and a convex surface far from the light source.
At least one technical scheme adopted by one or more embodiments of the specification can achieve the following beneficial effects:
the first lens, the second lens and the third lens are arranged in the projection lens, and specific two-side shapes, positive refractive power and negative refractive power are arranged for the lenses, so that light emitted by a projection light source can be projected in a collimating way through the lenses, the projection lens is ensured to have smaller distortion, the tolerance of the projection lens to high temperature is improved, the influence of high temperature on the projection lens is reduced, the change of the overall performance of the projection lens at high temperature is smaller, the stability of the projection lens is enhanced, the accuracy of constructing a three-dimensional space of a human face by adopting the projection lens is improved, and the accuracy of 3D human face recognition is further improved.
Drawings
In order to more clearly illustrate the embodiments of the present specification or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, it is obvious that the drawings in the following description are only some embodiments described in the present specification, and for those skilled in the art, other drawings can be obtained according to the drawings without any creative effort.
Fig. 1 is a schematic structural diagram of a projection lens suitable for 3D face recognition according to one or more embodiments of the present disclosure;
fig. 2 is a specific application of the projection lens in fig. 1 in an application scenario according to one or more embodiments of the present disclosure;
FIG. 3 is a schematic diagram of lens distortion corresponding to the projection lens of FIG. 2 provided in one or more embodiments of the present disclosure;
FIG. 4 is a spot diagram corresponding to the projection lens of FIG. 2 at 20 ℃ where the laser light is projected to 300mm according to one or more embodiments of the present disclosure;
FIG. 5 is a spot diagram corresponding to the projection lens of FIG. 2 at-40 ℃ with laser projection to 300mm according to one or more embodiments of the present disclosure;
FIG. 6 is a spot diagram corresponding to the projection lens of FIG. 2 at-10 ℃ with laser projection to 300mm according to one or more embodiments of the present disclosure;
FIG. 7 is a spot diagram corresponding to the projection lens of FIG. 2 at 50 ℃ where the laser light is projected to 300mm according to one or more embodiments of the present disclosure;
FIG. 8 is a spot diagram corresponding to the projection lens of FIG. 2 at 85 ℃ where the laser light is projected to 300mm according to one or more embodiments of the present disclosure;
fig. 9 is a specific application of the projection lens in fig. 1 in another application scenario provided in one or more embodiments of the present disclosure;
FIG. 10 is a schematic diagram of lens distortion corresponding to the projection lens of FIG. 9 provided in one or more embodiments of the present disclosure;
FIG. 11 is a spot diagram corresponding to the projection lens of FIG. 9 at 20 ℃ where the laser light is projected to 300mm according to one or more embodiments of the present disclosure;
FIG. 12 is a spot diagram corresponding to the projection lens of FIG. 9 at-40 ℃ with laser projection to 300mm according to one or more embodiments of the present disclosure;
FIG. 13 is a spot diagram corresponding to the projection lens of FIG. 9 at-10 ℃ with laser projection to 300mm according to one or more embodiments of the present disclosure;
FIG. 14 is a spot diagram corresponding to the projection lens of FIG. 9 at 50 ℃ with laser projection to 300mm according to one or more embodiments of the present disclosure;
fig. 15 is a spot diagram corresponding to the projection lens in fig. 9 projected by the laser to 300mm at 85 ℃ according to one or more embodiments of the present disclosure.
Detailed Description
The embodiment of the specification provides a projection lens suitable for 3D face recognition.
In order to make those skilled in the art better understand the technical solutions in the present specification, the technical solutions in the embodiments of the present specification will be clearly and completely described below with reference to the drawings in the embodiments of the present specification, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any inventive step based on the embodiments of the present disclosure, shall fall within the scope of protection of the present application.
In one or more embodiments of the present specification, a first lens, a second lens and a third lens are designed in a projection lens, the overall performance of the projection lens is optimized by respectively controlling the shapes, positive refractive power and negative refractive power of the first lens, the second lens and the third lens, setting the proportion of the effective focal length of the lenses and the overall focal length of the projection lens, controlling the curvature radius, the center thickness, the distance between the lenses, the aspheric surface coefficient, the selection of materials and the like of the lenses, so that the projection lens has the characteristics of excellent performance and stability, low distortion, high and low temperature tolerance (mainly aiming at the temperature range of-40 ℃ to 85 ℃, which is the temperature range in which the lens for human face recognition can be positioned during actual work), the accuracy of the three-dimensional space of the face to be recognized constructed through the projection lens is improved, and the accuracy of face recognition is enhanced. The following is a detailed description based on such a concept.
Fig. 1 is a schematic structural diagram of a projection lens suitable for 3D face recognition according to one or more embodiments of the present disclosure. The projection lens is applied to face recognition requirements of service scenes in different service fields, such as payment service in the field of internet financial service, transaction service in the field of electric business service, information interaction service in the field of instant messaging service, account login service in the field of game service, access control service in the field of public service and the like.
The projection lens in fig. 1 includes a projection light source 1, and a first lens 2, a second lens 3, and a third lens 4 which are sequentially arranged in an optical axis direction of the projection light source. The light emitted by the projection light source 1 sequentially passes through the first lens 2, the second lens 3 and the third lens, irradiates the face to be recognized and is reflected, so that a three-dimensional space corresponding to the face to be recognized is constructed according to the collected reflected light, and the face recognition is carried out. Along the optical axis direction, the position of the projection light source 1 can be called a light source surface, and the position of a human face to be recognized (i.e. the side far away from the projection light source 1) can be called an object surface. The projection light source 1 is, for example, a laser emitting array, a laser emitting surface, or the like.
As shown in fig. 1, the first lens element 2 with positive refractive power has convex surfaces on both sides; the second lens element 3 with negative refractive power has a concave surface near the light source and a convex surface far from the light source; the third lens element 4 with positive refractive power has a concave surface near the light source and a convex surface away from the light source.
In one or more embodiments of the present disclosure, by providing the first lens, the second lens, and the third lens in the projection lens, and setting a specific two-sided shape, positive refractive power, and negative refractive power for each lens, light emitted by the projection light source can be projected in a collimated manner through each lens, so as to ensure that the projection lens has smaller distortion, improve the tolerance of the projection lens to high temperature, reduce the influence of high temperature on the projection lens, reduce the overall performance change of the projection lens at high temperature, and enhance the stability of the projection lens, so as to improve the accuracy of constructing the three-dimensional space of a human face by using the projection lens, and further improve the accuracy of 3D human face recognition.
Based on the structure of fig. 1, the present specification also provides some specific embodiments and extensions of the structure, which are explained further below.
In one or more embodiments of the present description, a ratio of an overall focal length to an optical overall length of the projection lens is greater than 0.8 and less than 1.3. Specifically, it can be expressed as:
Figure BDA0003145122110000031
the overall focal length f represents the overall effect of the focal lengths of the first lens, the second lens and the third lens included in the projection lens, and the total optical length TTL represents the distance from the projection light source to the outer side of the projection lens. The projection lens has the characteristics of low distortion and high temperature tolerance by setting the range of the ratio of the integral focal length to the total optical length of the projection lens.
Further, the ratio of the focal lengths of the third lens and the first lens is greater than 1 and less than 2; the ratio of the focal length of the second lens to the overall focal length is greater than-0.7 and less than-0.1. Specifically, it can be expressed as:
Figure BDA0003145122110000041
wherein f is1Denotes the focal length of the first lens, f2Denotes the focal length of the second lens, f3Denotes a focal length of the third lens, and f denotes an overall focal length of the projection lens. Through the configuration of the focal length of each lens, the focal power can be reasonably distributed, the miniaturization design of the projection lens is favorably realized, and the volume of the projection lens is reduced.
Further, a ratio of the center thicknesses of the first lens and the second lens is greater than 1 and less than 2.2. Specifically, it can be expressed as:
Figure BDA0003145122110000042
wherein d is1Denotes the center thickness of the first lens, d2The center thickness of the second lens is indicated. By setting the central thickness of the first lens and the second lens, each lens has the optimal thickness, so that the production of lens lenses and the assembly of a projection lens are facilitatedAnd is convenient to use.
In one or more embodiments of the present description, a ratio of a radius of curvature of a light source-near surface of the first lens to a light source-far surface of the third lens is greater than-1.6 and less than-0.7; the ratio of the curvature radius of the light source far surface of the first lens to the curvature radius of the light source far surface of the second lens is more than 2 and less than 30; the ratio of the curvature radius of the light source surface of the second lens to the curvature radius of the light source surface of the third lens is greater than 0 and less than 0.3. Specifically, it can be expressed as:
Figure BDA0003145122110000043
wherein r is1Denotes a radius of curvature, r, of a surface of the first lens close to the light source2Denotes the radius of curvature, r, of the first lens surface remote from the light source3Denotes a radius of curvature, r, of a surface of the second lens close to the light source4Denotes the radius of curvature, r, of the surface of the second lens remote from the light source5Denotes a radius of curvature, r, of a surface of the third lens close to the light source6The radius of curvature of the third lens away from the light source surface is shown. The curvature radiuses of the first lens, the second lens and the third lens are set, so that aberration of the projection lens can be corrected, the projection lens has excellent performance, light can be collimated and projected through the lenses, and the lens distortion is small.
Further, a change value of the refractive index of the first lens per temperature change in degrees centigrade is greater than-0.00001 and less than 0; the second lens has a change in refractive index per degree celsius change in temperature of less than-0.00005. Specifically, it can be expressed as:
Figure BDA0003145122110000044
wherein the content of the first and second substances,
Figure BDA0003145122110000045
which represents a temperature change coefficient of the first lens, i.e., a change value of the refractive index of the first lens at a temperature change of 1 c,
Figure BDA0003145122110000046
indicating the coefficient of change of the temperature of the second lens, i.e. the refractive index of the second lens changes at temperatureChange at 1 ℃. By designing the temperature change coefficient of the lens and carrying out targeted optimization on the actual thermal expansion coefficient of the material adopted by the lens, the performance parameters of the projection lens under different temperature conditions can drift less along with the temperature, so that the projection lens is not influenced too much by the temperature, the requirement of stable work of the projection lens in a wider temperature range (such as-40 ℃ -85 ℃) is met, the stability of the projection lens can be enhanced, the adaptability of the projection lens to different temperatures is improved, and the subsequent accuracy of 3D face recognition is favorably improved.
Further, the first lens is closer to the projection light source, so that the thermal stability is better due to the glass material, and the second lens and the third lens are made of the same plastic material (for example, EP8000) so as to reduce the cost and stabilize the performance on the one hand and have better matching consistency on the other hand.
In one or more embodiments of the present disclosure, the first lens, the second lens, and the third lens are all of even aspheric surface type. Therefore, more optimized variables can be obtained for correcting the aberration of the projection lens, the thermal stability and the overall performance stability of the projection lens are improved, the use number of lenses in the projection lens is reduced, the size of the projection lens can be effectively reduced, and the cost is saved.
Furthermore, the surfaces of the first lens, the second lens and the third lens are provided with the inflection points, so that the overall performance requirement of the projection lens can be met, and the stability of the overall performance of the projection lens is improved. Specifically, 1 inflection point may be respectively disposed on a light source far surface of the first lens, a light source near surface of the second lens, a light source far surface of the second lens, and a light source far surface of the third lens, and 2 inflection points may be disposed on a light source near surface of the third lens. The structure enables the lens to have the characteristics of low distortion and high performance, and is beneficial to keeping stable performance under temperature change.
Furthermore, the projection light source is a laser emission array working in a wavelength band of 920nm to 960nm, and the light source in the wavelength band can obtain a better projection effect by matching with the structure and the exemplary parameters of the scheme. The size ratio of the laser emitting array used is, for example, 0.61mm by 0.55mm, and the single-spot laser emitting angle ratio is, for example, H/V (9.44 °/8.51 °).
In conjunction with the foregoing description, one or more embodiments of the present disclosure provide a specific application of the projection lens in fig. 1 in an application scenario, as shown in fig. 2. The variable sign in this embodiment is as described above.
Specifically, the overall focal length of the projection lens, the focal length of the first lens, the focal length of the second lens, and the focal length of the third lens may adopt the values in table 1.
TABLE 1
Figure BDA0003145122110000051
Specifically, the radii of curvature, center thicknesses, refractive indices, abbe numbers, and the like of the first lens, the second lens, and the third lens may take the values in table 2.
TABLE 2
Figure BDA0003145122110000052
Wherein L1 represents the distance from the projection light source to the first lens along the optical axis, and L2 represents the thickness of the first lens along the optical axis, i.e., d is described above1L3 denotes a distance between the first lens and the second lens along the optical axis, L4 denotes a thickness of the second lens along the optical axis, i.e., d described above2L5 denotes a distance between the second lens and the third lens along the optical axis, L6 denotes a thickness of the third lens along the optical axis, and L7 denotes a distance between the third lens and the surface of the projection object (i.e., a corresponding position on the face to be recognized) along the optical axis, which can be set to an arbitrary value.
Specifically, the aspherical coefficients of the respective surfaces of the first lens, the second lens, and the third lens may take the values in table 3.
TABLE 3
Serial number k a4 a6 a8 a10 a12 a14 a16
r1 -3.33E+00 1.50E-01 -1.08E+00 7.96E+00 -4.59E+01 1.60E+02 -3.10E+02 2.41E+02
r2 -1.00E+02 -1.70E-01 -4.76E-01 1.23E+00 -7.83E-01 -8.60E+00 4.24E+00 1.85E+01
r3 -1.19E+00 9.98E-01 2.51E+00 -2.91E+01 2.51E+01 1.08E+03 -1.21E+04 4.35E+04
r4 -2.62E+00 1.21E+00 3.17E+00 -2.10E+01 1.19E+02 -2.54E+02 -1.66E+03 7.20E+03
r5 -1.77E+01 1.94E-01 1.88E-01 1.95E-01 1.25E-02 -2.74E-01 1.35E+00 -8.98E-01
r6 -1.13E+00 2.91E-02 9.95E-02 3.45E-01 -1.11E-01 5.98E-01 -9.80E-01 3.02E+00
Specifically, the inflection points provided on the first lens, the second lens, and the third lens may be determined in the manner in table 4.
TABLE 4
Number of points of inflection Position of reverse curvature 1 Position of reverse curvature 2
r1 0
r 2 1 0.571
r 3 1 0.387
r 4 1 0.362
r 5 2 0.404 0.644
r 6 1 0.637
Wherein the position of the inflection point represents the perpendicular distance in mm from the inflection point to the optical axis.
In summary, according to the values in tables 1 to 4, the condition that the projection lens meets the above formulas can be determined. Specific examples are shown in table 5:
TABLE 5
Figure BDA0003145122110000061
Figure BDA0003145122110000071
Fig. 3 is a lens distortion diagram corresponding to the projection lens in fig. 2 provided in one or more embodiments of the present disclosure. In fig. 3, the abscissa represents the distortion value, the distortion value of 1 represents the distortion degree of 1%, the distortion value of-1 represents the distortion degree of-1%, and the ordinate represents the position of the light emitting point on the laser emission array with the center thereof being the coordinate point of 0. Through the experiment of fig. 3, the optical distortion of the projection lens is small, less than or even far less than 0.2%, and the projection lens has excellent performance and strong stability.
Fig. 4 is a spot diagram corresponding to the spot projected by the projection lens of fig. 2 at 20 ℃ to 300mm by the laser according to one or more embodiments of the present disclosure.
Fig. 4 includes 11 spot diagrams, where the object plane values above the spot diagrams represent positions on the laser emission array with the center of the laser emission array as a coordinate point 0, and are 0.0000mm, 0.0450mm, 0.0900mm, 0.1350mm, 0.1800mm, 0.2250mm, 0.2700mm, 0.3150mm, 0.3600mm, 0.4050mm, and 0.4500mm from left to right and from top to bottom, and the image plane values below the spot diagrams represent the converging positions of the light emitted by the laser emission array at 300mm, and are 0.000mm, -3.667mm, -7.336mm, -11.006mm, -14.674mm, -18.338mm, -22.001mm, -25.664mm, -29.332mm, -33.006mm, and-36.693 mm from left to right and from top to bottom. The legend on the right side of the dot pattern indicates the wavelength, which is 930nm, 940nm, 950nm, and 960nm from top to bottom.
Two groups of numerical values of Root Mean Square (RMS) radius and geographic information positioning (GEO) radius are displayed below the spot-spot diagram, which are two statistical methods, and respectively represent the spot radius of a spot on a 300mm plane after a spot light emitted by a point light source at 11 object planes passes through a lens of a projection lens at the temperature of 20 ℃. The RMS radius is 29.305, 29.294, 29.338, 29.468, 29.645, 30.103, 30.884, 31.166, 31.251, 32.277 and 33.747 in the unit of micrometer from left to right, and the GEO radius is 59.684, 60.603, 61.219, 61.534, 61.876, 75.899, 90.355, 93.276, 79.567, 74.892 and 87.165 in the unit of micrometer from left to right. In this specification, the spot size change at different temperatures is compared by the difference in GEO radius. The stippling patterns in the other embodiments below may be similarly understood with reference to the description of fig. 4.
Fig. 5 is a spot diagram corresponding to the projection lens in fig. 2 projected by the laser to 300mm at-40 ℃ according to one or more embodiments of the present disclosure.
Fig. 5 includes 11 spot diagrams, where an object plane value above each spot diagram indicates a position on the laser emitting array with the center of the laser emitting array as a coordinate point 0, and an image plane value below each spot diagram indicates a convergence position of light emitted by the laser emitting array at a position of 300 mm. The legend on the right side of the dot pattern indicates the wavelength, which is 930nm, 940nm, 950nm, and 960nm from top to bottom. Two groups of numerical values of RMS radius and GEO radius are displayed below the spot-spot diagram, and respectively represent the spot radius of a light spot emitted by a point light source at 11 object planes on a 300mm plane after passing through a lens of a projection lens at the temperature of minus 40 ℃. Specific values can be seen in fig. 5.
Fig. 6 is a spot diagram corresponding to the projection lens in fig. 2 projected by the laser to 300mm at-10 ℃ according to one or more embodiments of the present disclosure.
Fig. 6 includes 11 spot diagrams, where an object plane value above each spot diagram indicates a position on the laser emitting array with the center of the laser emitting array as a coordinate point 0, and an image plane value below each spot diagram indicates a convergence position of light emitted by the laser emitting array at a position of 300 mm. The legend on the right side of the dot pattern indicates the wavelength, which is 930nm, 940nm, 950nm, and 960nm from top to bottom. Two groups of numerical values of RMS radius and GEO radius are displayed below the spot-spot diagram, and respectively represent the spot radius of a light spot emitted by a point light source at 11 object planes on a 300mm plane after passing through a lens of a projection lens at the temperature of minus 10 ℃. Specific values can be seen in fig. 6.
Fig. 7 is a spot diagram corresponding to the projection lens in fig. 2 at 50 ℃ where the laser is projected to 300mm according to one or more embodiments of the present disclosure.
Fig. 7 includes 11 spot diagrams, where an object plane value above each spot diagram indicates a position on the laser emitting array with the center of the laser emitting array as a coordinate point 0, and an image plane value below each spot diagram indicates a convergence position of light emitted by the laser emitting array at a position of 300 mm. The legend on the right side of the dot pattern indicates the wavelength, which is 930nm, 940nm, 950nm, and 960nm from top to bottom. Two groups of numerical values of RMS radius and GEO radius are displayed below the spot-spot diagram, and respectively represent the spot radius of a light spot emitted by a point light source at 11 object planes on a 300mm plane after passing through a lens of a projection lens at the temperature of 50 ℃. Specific values can be seen in fig. 7.
Fig. 8 is a spot diagram corresponding to the projection lens in fig. 2 projected by laser light to 300mm at 85 ℃ according to one or more embodiments of the present disclosure.
Fig. 8 includes 11 spot diagrams, where an object plane value above each spot diagram indicates a position on the laser emitting array with the center of the laser emitting array as a coordinate point 0, and an image plane value below each spot diagram indicates a convergence position of light emitted by the laser emitting array at a position of 300 mm. The legend on the right side of the dot pattern indicates the wavelength, which is 930nm, 940nm, 950nm, and 960nm from top to bottom. Two groups of numerical values of RMS radius and GEO radius are displayed below the spot-spot diagram, and respectively represent the spot radius of a light spot emitted by a point light source at 11 object planes on a 300mm plane after passing through a lens of a projection lens at the temperature of 85 ℃. Specific values can be seen in fig. 8.
As can be seen from fig. 4 to 8, in the temperature range of-40 ℃ to 85 ℃, the maximum variation of the spot radius at 300mm with respect to the maximum variation at normal temperature (20 ℃) is 50um, and the projection lens is less affected by temperature, has high temperature latitude, and has good stability.
In conjunction with the foregoing description, one or more embodiments of the present disclosure provide a specific application of the projection lens in fig. 1 in another application scenario, as shown in fig. 9. The variable sign in this embodiment is as described above.
Specifically, the overall focal length of the projection lens, the focal length of the first lens, the focal length of the second lens, and the focal length of the third lens may adopt the values in table 6.
TABLE 6
Figure BDA0003145122110000091
Specifically, the radii of curvature, center thicknesses, refractive indices, abbe numbers, and the like of the first lens, the second lens, and the third lens may take the values in table 7.
TABLE 7
Figure BDA0003145122110000092
Wherein L1 represents the distance from the projection light source to the first lens along the optical axis, and L2 represents the thickness of the first lens along the optical axis, i.e., d is described above1L3 denotes a distance between the first lens and the second lens along the optical axis, L4 denotes a thickness of the second lens along the optical axis, i.e., d described above2L5 denotes a distance between the second lens and the third lens along the optical axis, L6 denotes a thickness of the third lens along the optical axis, and L7 denotes a distance between the third lens and the surface of the projection object (i.e., a corresponding position on the face to be recognized) along the optical axis, which can be set to an arbitrary value.
Specifically, the aspherical coefficients of the respective surfaces of the first lens, the second lens, and the third lens can take the values in table 8.
TABLE 8
Serial number k a4 a6 a8 a10 a12 a14 a16
r1 -8.95E+00 3.54E-01 -1.68E+00 6.48E+00 -3.00E+01 1.13E+02 -2.38E+02 1.93E+02
r2 -9.43E+01 -4.32E-01 -1.81E-01 1.16E+00 1.41E+00 -8.25E+00 -1.06E+01 3.35E+01
r3 -1.84E+00 1.08E+00 3.01E+00 -2.73E+01 -7.53E+01 1.57E+03 -9.71E+03 2.49E+04
r4 -7.83E+00 1.95E+00 3.47E+00 -2.11E+01 1.24E+02 -7.70E+02 9.32E+02 4.50E+03
r5 1.79E+01 1.92E-01 1.34E-01 3.14E-01 -2.12E-01 -3.08E-01 1.66E+00 -1.07E+00
r6 -1.44E+00 2.68E-02 1.31E-01 1.69E-01 1.29E-01 1.17E+00 -3.63E+00 5.16E+00
Specifically, the inflection points provided on the first lens, the second lens, and the third lens may be determined in the manner in table 9.
TABLE 9
Number of points of inflection Position of reverse curvature 1 Position of reverse curvature 2
r1 0
r 2 1 0.564
r 3 1 0.386
r 4 1 0.23
r 5 2 0.45 0.641
r 6 1 0.632
Wherein the position of the inflection point represents the perpendicular distance in mm from the inflection point to the optical axis.
In summary, according to the values in tables 6 to 9, the condition that the projection lens meets the above formulas can be determined. Specific examples are shown in table 10:
watch 10
Figure BDA0003145122110000101
Fig. 10 is a lens distortion diagram corresponding to the projection lens in fig. 9 provided in one or more embodiments of the present disclosure. The experiment of fig. 10 shows that the optical distortion of the projection lens is small, less than 0.2%, and the projection lens has excellent performance and strong stability.
Fig. 11 is a spot diagram corresponding to the spot projected by the projection lens of fig. 9 at 20 ℃ to 300mm by the laser according to one or more embodiments of the present disclosure.
Fig. 11 includes 11 spot diagrams, where the object plane values above the spot diagrams represent positions on the laser emission array with the center of the laser emission array as a coordinate point 0, and are 0.0000mm, 0.0450mm, 0.0900mm, 0.1350mm, 0.1800mm, 0.2250mm, 0.2700mm, 0.3150mm, 0.3600mm, 0.4050mm, and 0.4500mm from left to right and from top to bottom, and the image plane values below the spot diagrams represent the converging positions of the light emitted by the laser emission array at 300mm, and are 0.000mm, -3.666mm, -7.333mm, -10.998mm, -14.661mm, -18.318mm, -21.971mm, -25.621mm, -29.273mm, -32.939mm, and-36.644 mm from left to right and from top to bottom. The legend on the right side of the dot pattern indicates the wavelength, which is 930nm, 940nm, 950nm, and 960nm from top to bottom.
Two groups of numerical values of RMS radius and GEO radius are displayed below the spot-spot diagram, and respectively represent the spot radius of a light spot emitted by a point light source at 11 object planes on a 300mm plane after passing through a lens of a projection lens at the temperature of 20 ℃. The RMS radius is 28.752, 28.840/29.101, 29.435, 29.674, 29.926, 30.459, 30.937, 30.827, 30.586 and 30.764 in the unit of micrometer from left to right, and the GEO radius is 56.399, 60.459, 63.846, 65.203, 65.786, 67.278, 83.793, 94.531, 87.090, 73.407 and 84.169 in the unit of micrometer from left to right. In this specification, the spot size change at different temperatures is compared by the difference in GEO radius.
Fig. 12 is a spot diagram corresponding to the projection lens of fig. 9 at-40 ℃ where the laser is projected to 300mm according to one or more embodiments of the present disclosure.
Fig. 12 includes 11 spot diagrams, where an object plane value above each spot diagram indicates a position on the laser emitting array with the center of the laser emitting array as a coordinate point 0, and an image plane value below each spot diagram indicates a convergence position of light emitted by the laser emitting array at a position of 300 mm. The legend on the right side of the dot pattern indicates the wavelength, which is 930nm, 940nm, 950nm, and 960nm from top to bottom. Two groups of numerical values of RMS radius and GEO radius are displayed below the spot-spot diagram, and respectively represent the spot radius of a light spot emitted by a point light source at 11 object planes on a 300mm plane after passing through a lens of a projection lens at the temperature of minus 40 ℃. Specific values can be seen in fig. 12.
Fig. 13 is a spot diagram corresponding to the projection lens in fig. 9 projected by the laser to 300mm at-10 ℃ according to one or more embodiments of the present disclosure.
Fig. 13 includes 11 spot diagrams, where an object plane value above each spot diagram indicates a position on the laser emitting array with the center of the laser emitting array as a coordinate point 0, and an image plane value below each spot diagram indicates a converging position of light emitted by the laser emitting array at a position of 300 mm. The legend on the right side of the dot pattern indicates the wavelength, which is 930nm, 940nm, 950nm, and 960nm from top to bottom. Two groups of numerical values of RMS radius and GEO radius are displayed below the spot-spot diagram, and respectively represent the spot radius of a light spot emitted by a point light source at 11 object planes on a 300mm plane after passing through a lens of a projection lens at the temperature of minus 10 ℃. Specific values can be seen in fig. 13.
Fig. 14 is a spot diagram corresponding to the projection lens in fig. 9 at 50 ℃ where the laser is projected to 300mm according to one or more embodiments of the present disclosure.
Fig. 14 includes 11 spot diagrams, where an object plane value above each spot diagram indicates a position on the laser emitting array with the center of the laser emitting array as a coordinate point 0, and an image plane value below each spot diagram indicates a converging position of light emitted by the laser emitting array at a position of 300 mm. The legend on the right side of the dot pattern indicates the wavelength, which is 930nm, 940nm, 950nm, and 960nm from top to bottom. Two groups of numerical values of RMS radius and GEO radius are displayed below the spot-spot diagram, and respectively represent the spot radius of a light spot emitted by a point light source at 11 object planes on a 300mm plane after passing through a lens of a projection lens at the temperature of 50 ℃. Specific values can be seen in fig. 14.
Fig. 15 is a spot diagram corresponding to the projection lens in fig. 9 projected by the laser to 300mm at 85 ℃ according to one or more embodiments of the present disclosure.
Fig. 15 includes 11 spot diagrams, where an object plane value above each spot diagram indicates a position on the laser emitting array with the center of the laser emitting array as a coordinate point 0, and an image plane value below each spot diagram indicates a converging position of light emitted by the laser emitting array at a position of 300 mm. The legend on the right side of the dot pattern indicates the wavelength, which is 930nm, 940nm, 950nm, and 960nm from top to bottom. Two groups of numerical values of RMS radius and GEO radius are displayed below the spot-spot diagram, and respectively represent the spot radius of a light spot emitted by a point light source at 11 object planes on a 300mm plane after passing through a lens of a projection lens at the temperature of 85 ℃. Specific values can be seen in fig. 15.
As can be seen from fig. 11 to 15, in the temperature range of-40 ℃ to 85 ℃, the maximum variation of the spot radius at 300mm from the maximum variation at normal temperature (20 ℃) is 50um, and the projection lens is less affected by temperature, has high temperature latitude, and has good stability.
It is to be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments.
The above description is merely one or more embodiments of the present disclosure and is not intended to limit the present disclosure. Various modifications and alterations to one or more embodiments of the present description will be apparent to those skilled in the art. Any modification, equivalent replacement, improvement or the like made within the spirit and principle of one or more embodiments of the present specification should be included in the scope of the claims of the present specification.

Claims (10)

1. A projection lens suitable for 3D face recognition comprises a projection light source, and a first lens, a second lens and a third lens which are sequentially arranged along the optical axis direction of the projection light source;
the first lens element with positive refractive power has two convex surfaces;
the second lens has negative refractive power, and the surface of the second lens, which is close to the light source, is a concave surface, and the surface of the second lens, which is far from the light source, is a convex surface;
the third lens element with positive refractive power has a concave surface near the light source and a convex surface far from the light source.
2. The projection lens of claim 1 having a ratio of overall focal length to total optical length greater than 0.8 and less than 1.3.
3. The projection lens of claim 2 wherein the ratio of the focal length of the third lens to the focal length of the first lens is greater than 1 and less than 2;
the ratio of the focal length of the second lens to the overall focal length is greater than-0.7 and less than-0.1.
4. The projection lens of claim 1 wherein the ratio of the center thickness of the first lens to the second lens is greater than 1 and less than 2.2.
5. The projection lens of claim 1, wherein the ratio of the curvature radius of the light source surface of the first lens to the curvature radius of the light source surface of the third lens is greater than-1.6 and less than-0.7;
the ratio of the curvature radius of the light source far surface of the first lens to the curvature radius of the light source far surface of the second lens is more than 2 and less than 30;
the ratio of the curvature radius of the light source approaching surface of the second lens to the curvature radius of the light source approaching surface of the third lens is greater than 0 and less than 0.3.
6. The projection lens of claim 1, wherein the first lens has a change value of a refractive index per degree celsius temperature change of more than-0.00001 and less than 0;
the second lens has a change in refractive index per degree celsius change in temperature of less than-0.00005.
7. The projection lens of any one of claims 1 to 6, wherein the first lens is made of glass material, and the second lens and the third lens are made of the same plastic material.
8. The projection lens of any one of claims 1 to 6, wherein the first lens, the second lens and the third lens are all of even aspheric surface type.
9. The projection lens of any one of claims 1 to 6, wherein the projection light source is a laser emission array operating in a wavelength band of 920nm to 960 nm.
10. The projection lens of any one of claims 1 to 6, wherein 1 inflection point is respectively disposed on a light source far surface of the first lens, a light source near surface of the second lens, a light source far surface of the second lens, and a light source far surface of the third lens, and 2 inflection points are respectively disposed on a light source near surface of the third lens.
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