Lens element, optical imaging system, laser radar and electric equipment

Abstract

The utility model relates to a lens element, an optical imaging system, a laser radar and electric equipment. The lens element comprises at least two kinds of phase regulation and control units, and the at least two kinds of phase regulation and control units are arranged at intervals. One phase regulation and control unit corresponds to incident light with one wavelength, and different phase regulation and control units have different steering angles so as to regulate and control the phases of the incident light with different wavelengths respectively; the focal lengths of incident light with different wavelengths are equal after the incident light passes through the corresponding phase regulation and control units; and after incident light with different wavelengths passes through the corresponding phase regulation and control units, focuses of the incident light are staggered from each other. According to the lens element, the optical imaging system, the laser radar and the electric equipment provided by the invention, off-axis focusing achromatism can be realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lenses, in particular to a lens element, an optical imaging system, a laser radar and an electrical equipment. BACKGROUND

[0002] Intelligent driving is a trend of vehicle development. Laser radars are widely used in intelligent driving at present. Laser radars often use laser beams of different wavelengths to adapt to different scenes and meet the imaging needs of different detection distances. Laser radars generally use lens elements for imaging, and a single lens element can only correspond to incident light of one wavelength. The lens element converges incident light (parallel light) with the corresponding wavelength to the designed focal point. For incident light with other wavelengths, since it does not completely satisfy the phase modulation formula, it will be converged to other positions on the optical axis. In this way, the line width of the overall focused spot and the aggregation efficiency will be poor, which will produce an axial chromatic aberration. With the increase of the working bandwidth of the lens element and the diameter of the lens element, the axial chromatic aberration will gradually increase, so that the lens element cannot focus normally. CONTENT OF THE UTILITY MODEL

[0003] The present application provides a lens element, an optical imaging system, a laser radar and an electrical equipment capable of eliminating axial chromatic aberration and focusing.

[0004] In order to achieve the above-mentioned purpose, in a first aspect, the present application provides a lens element, the lens element comprising at least two phase modulation units, the at least two phase modulation units being arranged at intervals; one phase modulation unit corresponds to incident light of one wavelength, and the turning angles of the at least two phase modulation units are different to respectively modulate the phases of incident light of different wavelengths; the focal lengths of incident light of different wavelengths after passing through the corresponding phase modulation units are equal; and the focal points of incident light of different wavelengths after passing through the corresponding phase modulation units are staggered with each other.

[0005] In some embodiments of the present application, the phase modulation units have different sizes, and the phase modulation units with different sizes are configured to respectively modulate the phases of incident light of different wavelengths; wherein the turning angles of the phase modulation units with different sizes are different.

[0006] In some embodiments of the present application, the sizes of the phase modulation units are in the order of two-dimensional sub-wavelength.

[0007] In some embodiments of the present application, the focal points of incident light of different wavelengths after passing through the corresponding phase modulation units are staggered with each other by r / n; wherein r is the equivalent radius of the lens element, and n is a positive integer.

[0008] In some embodiments of the present application, each phase control unit comprises a substrate and a phase control structure, the phase control structure is located on the substrate and extends along the first direction.

[0009] In some embodiments of the present application, the refractive index of the substrate is lower than the refractive index of the phase control structure.

[0010] In some embodiments of the present application, the phase control unit has a cross section perpendicular to the first direction; wherein the shape of the cross section has anisotropy at least in the second direction and the third direction, the second direction intersects the third direction, and at least one of the second direction and the third direction is perpendicular to the first direction.

[0011] In some embodiments of the present application, the phase control units for controlling the phase of incident light with different wavelengths have the same size in the first direction; the phase control units for controlling the phase of incident light with different wavelengths have different sizes in the second direction and / or the third direction.

[0012] In some embodiments of the present application, the size of the phase control unit increases with the increase of the wavelength of the incident light corresponding thereto.

[0013] In some embodiments of the present application, the phase control units for controlling the phase of incident light with different wavelengths are periodically arranged.

[0014] In some embodiments of the present application, the plurality of phase control units comprises a first phase control unit corresponding to incident light with a first wavelength and a second phase control unit corresponding to incident light with a second wavelength; wherein the first phase control unit and the second phase control unit are periodically arranged along a direction.

[0015] In some embodiments of the present application, the plurality of phase control units further comprises a third phase control unit corresponding to incident light with a third wavelength, the third phase control unit is located on the side of the second phase control unit away from the first phase control unit; wherein the first phase control unit, the second phase control unit and the third phase control unit are periodically arranged along a direction.

[0016] In some embodiments of the present application, the plurality of phase control units comprises a plurality of periodically arranged phase control unit groups, each phase control unit group comprises a plurality of first phase control units, a plurality of second phase control units and a plurality of third phase control units; wherein within the same phase control unit group, the plurality of first phase control units, the plurality of second phase control units and the plurality of third phase control units are respectively arranged at intervals along the same direction.

[0017] In some embodiments of the present application, the number of first phase control units, the number of second phase control units, and the number of third phase control units are the same or different in different phase control unit groups; and / or the number of first phase control units, the number of second phase control units, and the number of third phase control units are the same or different in the same phase control unit group.

[0018] In some embodiments of the present application, the incident light is circularly polarized incident light.

[0019] In a second aspect, the present application further provides an optical imaging system, which comprises the lens element as above.

[0020] In a third aspect, the present application further provides a laser radar, which comprises the optical imaging system as above.

[0021] In a fourth aspect, the present application further provides an electrical equipment, which comprises the optical imaging system or the laser radar as above.

[0022] The lens element, the optical imaging system, the laser radar, and the electrical equipment provided by the present application can meet the phase requirements of incident light with different wavelengths by including multiple phase control units with different turning angles and arranged at intervals in the same lens element to respectively control the phase of incident light with different wavelengths. The present application can meet the phase requirements of incident light with different wavelengths by arranging at least two phase control units with different turning angles in the same lens element based on a geometric control mode, so that the focal lengths of incident light with different wavelengths after passing through the corresponding phase control units are equal, and the focal points of incident light with different wavelengths after passing through the corresponding phase control units are staggered. In this way, the incident light with different wavelengths can be focused at different positions of the optical axis of the lens element after passing through the lens element, so as to eliminate the axial chromatic aberration. The focal points of the incident light with different wavelengths after passing through the lens element of the present application are distributed on both sides of the optical axis, so that the lens element, the optical imaging system, and the electrical equipment of the present application can achieve the purpose of off-axis focusing and achromatization.

[0023] Other features and advantages of the present application will be described in detail in the following specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0025] For a more complete understanding of the present application and the advantages thereof, reference is now made to the following descriptions taken in connection with the accompanying drawings in which like parts are marked with like numbers throughout the several figures.

[0026] Figure 1A A perspective view of a lens element is provided for some exemplary embodiments of the present application.

[0027] Figure 1B A perspective view of a lens element is provided for some exemplary embodiments of the present application. Figure 1A A top view of the lens element is shown.

[0028] Figure 2A A perspective view of a lens element is provided for some exemplary embodiments of the present application. Figure 1A A partial enlarged view of the lens element is shown.

[0029] Figure 2B A perspective view of a lens element is provided for some exemplary embodiments of the present application. Figure 1A A partial enlarged view of the lens element is shown.

[0030] Figure 3 A perspective view of a lens element is provided for some exemplary embodiments of the present application. Figure 2A An enlarged view of one phase control unit of the lens element is shown.

[0031] Figure 4 Outgoing phase diagrams of the phase control unit for three incident lights are shown.

[0032] Figure 5 Conversion efficiency diagrams of the phase control unit for different sizes are shown.

[0033] Figure 6 A perspective view of a lens element is provided for some exemplary embodiments of the present application. Figure 1A Additional phase diagrams of the lens element for three different wavelengths of incident light are shown.

[0034] Figure 7A A focusing schematic of the lens element in the XZ plane for the first wavelength of incident light is shown based on Figure 1A

[0035] A focusing schematic of the lens element in the XY plane for the first wavelength of incident light is shown based on Figure 7B Figure 1A A focusing schematic of the lens element in the XZ plane for the second wavelength of incident light is shown based on

[0036] Figure 8A Figure 1A A focusing schematic of the lens element in the XY plane for the second wavelength of incident light is shown based on

[0037] Figure 8B A focusing schematic of the lens element in the XZ plane for the third wavelength of incident light is shown based on Figure 1A

[0038] A focusing schematic of the lens element in the XY plane for the third wavelength of incident light is shown based on Figure 9A Figure 1A ​​​A focusing schematic view of the lens element in the XZ plane.

[0039] Figure 9B The focal length of the incident light of the third wavelength is based on Figure 1A A focusing schematic view of the lens element in the XY plane.

[0040] Figure 10 A module schematic view of the optical imaging system provided in the present application.

[0041] Figure 11 A module schematic view of the laser radar provided in the present application.

[0042] Figure 12 A module schematic view of the power utilization equipment provided in the present application.

[0043] Legend of reference signs:

[0044] 1000, power utilization equipment; 1001, laser radar; 100, optical imaging system; 200, transceiver system; 110, lens element; 1101, phase control unit group; 10, phase control unit; 11, first phase control unit; 12, second phase control unit; 13, third phase control unit; 111, substrate; 112, phase control structure; Z, first direction; X, second direction; Y, third direction; 101, first side; 102, second side. DETAILED DESCRIPTION

[0045] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person skilled in the art without creative effort fall within the protection scope of the present application.

[0046] Please refer to Figure 1A , 1B , 2A, 2B and Figure 3 , some example embodiments of the present application provide a lens element 110, the lens element 110 includes at least two kinds of phase control units 10, the at least two kinds of phase control units 10 are arranged at intervals, one kind of phase control unit 10 corresponds to incident light with one kind of wavelength, the turning angles of the at least two kinds of phase control units 10 are different, so as to respectively control the phases of the incident light with different wavelengths; the focal lengths of the incident light with different wavelengths after passing through the corresponding phase control units 10 are equal; the focal points of the incident light with different wavelengths after passing through the corresponding phase control units 10 are staggered.

[0047] Among them, please refer to Figure 3Each phase control unit 10 has a first side 101 and a second side 102. The angle between the arrangement direction of each phase control unit 10 and the extension line of the first side 101 is the turning angle θ of the phase control unit 10 (the phase control structure 112, see below). In the embodiment, the length of the first side 101 is greater than the length of the second side 102. In other embodiments, the length of the first side 101 can also be less than the length of the second side 102.

[0048] By including multiple phase control units with different turning angles in the same lens element, the present application controls at least two phase control units with different turning angles in the same lens element based on geometric control, so that the phase control requirements of incident light with different wavelengths can be met, thereby making the focal lengths of incident light with different wavelengths after passing through the corresponding phase control units equal, and the focal points of incident light with different wavelengths after passing through the corresponding phase control units staggered with each other. In this way, the probability of incident light with different wavelengths focusing at different positions of the optical axis of the lens element after passing through the lens element can be reduced, thereby better reducing the influence of axial chromatic aberration on imaging. Since the focal points of incident light with different wavelengths after passing through the lens element of the present application are distributed on both sides of the optical axis, the lens element of the present application can achieve the purpose of off-axis focusing and achromatization.

[0049] In some embodiments of the present application, the sizes of each phase control unit 10 are the same, and the sizes of different phase control units 10 are different. By controlling the sizes of multiple phase control units 10, the phase control requirements of incident light with different wavelengths can be further met, and more flexible and accurate phase control can be achieved, thereby improving the performance and function of the optical system.

[0050] In some embodiments of the present application, the phase control unit 10 has a size in the order of two-dimensional sub-wavelength. Sub-wavelength refers to the size of an object or structure being smaller than the wavelength of the incident electromagnetic wave. In the field of optics, the order of wavelength is usually microns, so the order of sub-wavelength is nanometers. The phase control unit in the order of sub-wavelength can control the phase, amplitude and other parameters of the incident light, so that the lens element has an ultra-thin planar structure. It realizes various functions such as focusing imaging similar to geometric optical lens and precise control of light wave phase, thereby realizing wideband achromatic function, which is very important to improve imaging quality and reduce chromatic aberration. By arranging sub-wavelength phase control units in a two-dimensional plane, the lens element can realize complex optical functions in a very small space, which makes the optical system more compact and portable. The sub-wavelength structure is easy to integrate with other optical elements, and the multi-dimensional and dynamic phase control can be realized by changing the geometric parameters of the phase control unit, thereby improving the integration and flexibility of the lens element. The phase control unit in the order of sub-wavelength can provide a diffraction angle close to 90°, which is much higher than that of traditional optical elements, which helps to improve the diffraction efficiency and enhance the imaging performance. In summary, the lens element uses two-dimensional phase control units in the order of sub-wavelength to realize high-precision phase control, reduce the volume of the optical system, improve the integration and flexibility, avoid the limitations of traditional optical elements, and optimize the diffraction efficiency, thereby showing great potential and advantages in modern optical applications.

[0051] The phase control unit has a unit period, which refers to the interval at which the structure repeats in the lens element (superlens). The unit period is usually in the order of sub-wavelength, which is smaller than the wavelength of the incident light and larger than the size of the phase control unit in the direction perpendicular to the first direction (height direction). This sub-wavelength unit period can produce a special electromagnetic response to the incident light, thereby achieving precise control of the phase, amplitude, polarization and other characteristics of the incident light. This design applied in superlens can achieve phase delay of different wavelengths of incident light, so that the superlens can effectively focus the incident light in a wider wavelength range without causing large chromatic aberration.

[0052] In some embodiments of the present application, the focal lengths of the incident light with different wavelengths after passing through the corresponding phase control unit 10 are equal, and the focal points of the incident light with different wavelengths after passing through the corresponding phase control unit 10 are staggered. By controlling the turning angle, size and arrangement of the phase control unit 10, the focal lengths of the incident light with different wavelengths can be made equal and the focal points can be staggered. In this way, the purpose of off-axis focusing and achromatism can be achieved.

[0053] In some embodiments of this application, incident light of different wavelengths, after passing through the corresponding phase adjustment unit 10, has its focal points offset by r / n; where r is the equivalent radius of the lens element and n is a positive integer. n can be set according to actual conditions. In this way, off-axis focusing and chromatic aberration can be achieved while maintaining the overall size of the lens element.

[0054] In some embodiments of this application, each phase control unit 10 includes a substrate 111 and a phase control structure 112, the phase control structure 112 being located on the substrate 111 and extending along a first direction Z.

[0055] Please continue reading for more details. Figure 3 Multiple phase control units 10 of each type are arranged along the second direction X, and different types of phase control units 10 are arranged along the third direction Y. The second direction X and the third direction Y intersect, and the second direction X and the third direction Y intersect the first direction Z respectively and are located in different planes from the first direction Z. The angle between the second direction X and the extension line of the first side 101 is the turning angle θ of the phase control unit 10 (phase control structure 112, see below).

[0056] In some embodiments of this application, the refractive index of the substrate 111 is lower than that of the phase modulation structure 112, so as to improve the conversion efficiency of the phase modulation unit 10 for circularly polarized incident light.

[0057] In some embodiments of this application, the material of the substrate 111 may include silicon dioxide (SiO2), and the material of the phase modulation structure 112 may include silicon (Si), titanium dioxide (TiO2), gallium phosphide (GaP), and silicon nitride (SiN), etc.

[0058] In some embodiments of this application, the phase adjustment unit 10 has a cross section perpendicular to the first direction Z; wherein the shape of the cross section is anisotropic in at least two directions perpendicular to the first direction, that is, the shape of the cross section cannot be a centrally symmetric shape such as a square or a circle, so as to facilitate the dimensional adjustment of the phase adjustment unit 10. For example, the shape of the cross section of the phase adjustment unit 10 is a rectangle, an ellipse, or the like.

[0059] In some embodiments of this application, the phase control units 10 used to control the phase of incident light with different wavelengths have the same size in the first direction; the phase control units 10 used to control the phase of incident light with different wavelengths have different sizes in at least one direction perpendicular to the first direction Z. Provided that the heights of the phase control units 10 are equal, the size of the phase control units 10 is adjusted by controlling the length or width of the phase control units 10, so that the size of each phase control unit 10 is different.

[0060] In some embodiments of the present application, the size of the phase control unit increases with the increase of the wavelength of the incident light corresponding thereto. The reason why the size of the phase control unit is larger when the wavelength of the incident light is longer can be explained from the optical principle and the material characteristics. First, the size of the phase control unit is closely related to the wavelength of the incident light, because the phase control depends on the propagation characteristics of the light wave in the medium. When the wavelength of the incident light is longer, in order to achieve effective phase control, a larger structure size is needed to match the longer wavelength, so as to ensure that the propagation path and phase change of the light wave in the medium can be accurately controlled. In addition, factors such as the refractive index of the material, the grating period, etc. also affect the design of the phase control unit, and studies have shown that a longer wavelength requires a larger structure size to achieve a specific optical effect. Therefore, a longer wavelength of the incident light requires a larger size of the phase control unit in order to physically achieve the required phase control effect.

[0061] In some embodiments of the present application, the phase control units 10 for controlling the phase of incident light with different wavelengths are periodically arranged. By periodically arranging the phase control units 10, not only can 2π phase coverage be achieved, but also an additional phase compensation factor can be introduced, so that the superlens element 110 can achieve ideal focusing effect at different wavelengths, and the design process can be simplified, and more types of phase control units 10 can be introduced to achieve larger bandwidth achromatic focusing effect, etc. In general, the periodic arrangement of the phase control units 10 for controlling the phase of incident light with different wavelengths helps to achieve more efficient geometric phase control, improve design flexibility and application potential, and optimize phase response, thereby showing greater application prospects in optical imaging and display technology.

[0062] In some embodiments of the present application, the lens element 110 includes a first phase control unit 11 corresponding to incident light with a first wavelength and a second phase control unit 12 corresponding to incident light with a second wavelength, and the first phase control unit 11 and the second phase control unit 12 are arranged at intervals and periodically arranged in one direction. By arranging the first phase control unit and the second phase control unit at intervals and periodically arranging them in one direction, the geometric phase of the incident light of two different wavelengths can be controlled, and then the phase can be accurately and efficiently controlled.

[0063] In some embodiments of the present application, the lens element 110 further comprises a third phase control unit 13 corresponding to incident light with a third wavelength, the third phase control unit 13 is located on the side of the second phase control unit 12 away from the first phase control unit 11, and the first phase control unit 11, the second phase control unit 12 and the third phase control unit 13 are arranged periodically in one direction. By arranging the first phase control unit 11, the second phase control unit 12 and the third phase control unit 13 periodically in one direction, the geometric phase of more incident light with different wavelengths can be controlled, and the precise and efficient control of the phase can be realized.

[0064] In some embodiments of the present application, the lens element 110 comprises a plurality of periodically arranged phase control unit groups 1101, each phase control unit group 1101 comprises a plurality of first phase control units 11, a plurality of second phase control units 12 and a plurality of third phase control units 13; wherein, in the same phase control unit 10, the plurality of first phase control units 11, the plurality of second phase control units 12 and the plurality of third phase control units 13 are arranged periodically in the same direction. By arranging the plurality of first phase control units 11, the plurality of second phase control units 12 and the plurality of third phase control units 13 periodically in the same direction, not only can the arrangement of different types of phase control units be more reasonable, but also is conducive to the formation of mutually staggered focal points by incident light with different wavelengths through corresponding types of phase control units.

[0065] In other embodiments, the plurality of same type phase control unit groups 1101 can also be distributed in an array, and the arrangement manner is not limited to the listed arrangement manners, and can be determined according to actual needs.

[0066] In other embodiments, the lens element 110 can further comprise more types of phase control units 10, such as fourth phase control units, fifth phase control units, etc., the type of phase control unit included in the lens element 110 depends on different application scenarios of the lens element, and in different application scenarios, the wavelengths of incident light are different, and it can also be considered that the type of phase control unit included in the lens element 110 depends on the need to have several wavelengths of incident light.

[0067] In some embodiments of the present application, the number of first phase control units 11, the number of second phase control units 12, and the number of third phase control units 13 in different phase control units 10 are the same or different; and / or the number of first phase control units 11, the number of second phase control units 12, and the number of third phase control units 13 in the same phase control unit 10 are the same or different. That is to say, in different phase control units 10, the number of each phase control unit 10 can be reasonably designed according to the shape and size of the substrate, so that the phase control units are generally uniformly distributed, thereby improving the utilization rate of the substrate.

[0068] In some embodiments of the present application, the incident light is circularly polarized incident light. The circularly polarized incident light has at least the following advantages: using circularly polarized light as the incident light source can significantly improve the focusing efficiency of the lens element; when the circularly polarized light passes through the surface of the lens element, it can achieve continuous phase control of 0 to 2π for the incident circularly polarized light by rotating the phase control structure, which makes the lens element can flexibly control the phase of the outgoing light field, thereby realizing precise wavefront manipulation; the circularly polarized light exhibits unique polarization conversion characteristics in the phase control structure of the lens element, for example, left-handed circularly polarized light (LCP or LH-CPL) and right-handed circularly polarized light (RCP or RH-CPL) can achieve phase changes by different rotation angles, which makes it possible to realize independent control of different polarization states. In summary, choosing circularly polarized incident light not only improves the focusing efficiency and phase control flexibility of the lens element, but also simplifies the design process and has a wide application prospect in various applications.

[0069] For a rectangular micro-nano scale phase control unit, the central axes corresponding to the long and short sides can be regarded as the fast axis and the slow axis of the birefringent element. The P-B phase modulation effect of the phase control unit on the light field can be represented by the Jones matrix as:

[0070]

[0071] Here, Et represents the electromagnetic scattering response of the phase control unit under circularly polarized incident light, Ex and Ey represent the electric field scattering components of the phase control unit in the x-axis direction and the y-axis direction, respectively, Mani represents the scattering matrix of the phase control unit, tx and ty represent the co-polarization transmission coefficients of the phase control unit under excitation of electromagnetic waves linearly polarized along the x-axis and y-axis directions in the non-rotated case, and a represents the rotation angle of the metasurface unit. [1, i] represents the unnormalized left-handed circularly polarized light Jones matrix, and [1, -i] represents the unnormalized right-handed circularly polarized light Jones matrix. As can be seen from the mathematical relationship shown in the formula, under the action of circularly polarized incident light, by rotating the phase control structure along the z-axis by an angle a through the P-B phase, a phase modulation of 2a can be generated on the cross-polarization transmission phase. Moreover, this modulation effect is independent of the wavelength. That is, for different wavelengths, the phase modulation of 2a is constant.

[0072] By rotating the steering of the phase control unit 10 (the phase control structure 112), the adjustment of the exit phase of the circularly polarized incident light can be realized. In order to achieve the purpose of multi-wavelength off-axis focusing achromatism of the present application, the following will use three wavelengths of incident light to illustrate and verify the principle. First, the size of three different kinds of phase control units 10 of the lens element 110 needs to be determined, and the conversion efficiency of the three kinds of phase control units 10 to circularly polarized incident light and the phase of the exit light are obtained.

[0073] To improve the conversion efficiency, the material of the base 111 of the lens element 110 is selected as low refractive index silicon dioxide, and the material of the phase control structure 112 is selected as high refractive index monocrystalline silicon. The incident light is left-handed circularly polarized light with wavelengths of 589 nm, 808 nm and 980 nm. These three wavelengths are common diode laser module wavelengths, commonly used in laser scanning systems, laser printing systems, and even laser radars. This application selects these three wavelengths to illustrate the ability of the lens element to off-axis achromatic focusing of these three common laser wavelengths. In order to achieve control of the three wavelengths, the size of the phase control unit 10 should be in the order of subwavelength. According to the actual magnitude of the three wavelengths and the difference between them, we correspondingly control the three wavelengths of 589 nm, 808 nm and 980 nm and the different sizes of the first phase control unit 11, the second phase control unit 12 and the third phase control unit 13. The length of the first phase control unit 11, the second phase control unit 12 and the third phase control unit 13 is set to 0.15 um, 0.205 um and 0.251 um respectively, the width is set to 0.085 um, 0.105 um and 0.155 um respectively, and the height is uniform 0.4 um. The unit period of the first phase control unit 11, the second phase control unit 12 and the third phase control unit 13 is 0.3 um*0.3 um. The material of the base 111 is silicon dioxide, and the material of the phase control structure 112 is monocrystalline silicon.

[0074] Please refer to Figure 4 and Figure 5 , Figure 4 and Figure 5 are the exit phase diagram and conversion efficiency diagram obtained by rotating the three different sizes of phase control structure 112 in the angle range of 0-180 degrees. Here different dashed lines represent the incident light with wavelengths of 589 nm, 808 nm and 980 nm respectively. Figure 4 It can be seen that the phase difference of the three wavelengths can cover (-pi, pi), that is, 2pi phase coverage can be achieved. Moreover, within the rotation range of 0-180 degrees, the phase difference is always stable, which means that the unit period of 0.3 um is appropriate. Because the prerequisite for designing a superlens is that the phase control structure 112 cannot be resonantly coupled. At the same time, the conversion efficiency of left-handed to right-handed circularly polarized light is maintained above 0.25, which is better than the metal medium, so the three phase control units 10 can be used to design superlenses based on P-B phase (also known as geometric phase type control method) to control the wavefront. In order to achieve the design goal of off-axis focusing achromatism, the wavefront phase formulas of the three incident lights are respectively:

[0075]

[0076]

[0077] In the formulas ①, ②, ③, λ1, λ2, λ3 are the wavelengths of the incident light, respectively equal to 589 nm, 808 nm, 980 nm. f1, f2, f3 are the focal lengths of the three wavelengths, and we set f1, f2, f3 to be 15 um in order to make the focal lengths of the three incident lights the same. In order to achieve off-axis focusing, that is, to make the focal lengths of the three wavelengths staggered on the concentric axis, the variables x in the formulas ①, ②, ③ are staggered by a distance of r / 4, where r is the radius of the superlens (lens element 110), and in an embodiment of the present application, r is equal to 10 um.

[0078] We expect that by designing the phase formulas of the three incident lights in this way, the three incident lights of different wavelengths will be focused on the same distance after passing through the superlens (lens element 110). However, the positions of the three wavelengths are not simply overlapped at the same position, but are staggered by a distance of r / 4 from each other. In this way, the superlens (lens element 110) achieves the purpose of off-axis focusing of three-color light, but achromatic design.

[0079] It should be pointed out that when constructing the target phase wavefront, we obtain the phase wavefront required for off-axis achromatic focusing of three wavelengths by sampling in turn according to the three formulas ①, ②, ③. From the perspective of the superlens, this is also the additional phase that the off-axis achromatic superlens needs to achieve for the three incident lights, as shown in Figure 6 . Figure 6 The phase pattern that the lens element 110 needs to add to the three incident lights of different wavelengths. As can be seen from Figure 6 , the phase distribution presents a periodic fringe pattern, and these fringes represent the periodic change of the phase, which corresponds to the periodic structure of the lens element 110 (such as the periodically arranged phase control structure 112). The change of the phase can be represented by the color change in the figure, and the color bar shows the range of the phase value. Based on the above discussion around the formulas ①, ②, ③, in order to use the lens element 110 to achieve the different phase differences for the three incident lights of different wavelengths as shown in Figure 6 , we need to combine the P-B phase and rotate the three phase control structures 112 of different sizes to obtain the distribution and rotation direction of the phase control structure 112 on the lens element 110 for the three incident light wavelengths of 589 nm, 808 nm and 980 nm. The distribution and rotation direction of the phase control structure 112 can be referred to as described above and Figures 1A-3 . A plurality of each phase control unit 10 is arranged along the second direction X at intervals, and different phase control units 10 are arranged along the third direction Y at intervals.

[0080] The above is the discussion of designing three kinds of off-axis focusing achromatic lens elements of different wavelengths. After the lens element is constructed in the software, we can set the light source as left-handed circularly polarized light with wavelengths of 589 nm, 808 nm and 980 nm, respectively, and observe the actual design effect. Figure 7A 、 Figure 8A 、 Figure 9A are the focusing schematic diagrams of the left-handed circularly polarized light with wavelengths of 589 nm, 808 nm and 980 nm, respectively, after passing through the lens element 110 in the XZ plane. Figure 7B 、 Figure 8B and Figure 9B are the focusing schematic diagrams of the left-handed circularly polarized light with wavelengths of 589 nm, 808 nm and 980 nm, respectively, after passing through the lens element 110 in the XZ plane.

[0081] As can be seen from Figure 7A , the left-handed polarized incident light with a wavelength of 589 nm is focused at a focal length of 15 um, but at a position 5 um to the left of the concentric axis of the lens element. As can be seen from Figure 7B , the left-handed circularly polarized incident light with a wavelength of 808 nm is also focused at a focal length of 15 um, but on the concentric axis of the lens element. As can be seen from Figure 8A , the left-handed circularly polarized incident light with a wavelength of 980 nm is also focused at a position 15 um from the plane of the lens element (focal length of 15 um), but at a position 5 um to the right of the concentric axis of the lens element. Therefore, it can be concluded that the left-handed circularly polarized incident light of three different wavelengths can be focused after passing through the lens element, and the focal spots of each other are staggered.

[0082] At the same time, it should be pointed out that from Figure 7B 、 Figure 8B and Figure 9B , it can be seen that the left-handed circularly polarized incident light with wavelengths of 589 nm, 808 nm and 980 nm can not only be focused after passing through the lens element, but also have little sign of dispersion of the focal spot, which also illustrates the scientificity and rationality of the design of the lens element of the present application.

[0083] In summary, the off-axis achromatic lens element proposed in the present application can indeed focus the left-handed circularly polarized incident light of three different wavelengths at the same focal length, and the focal points of the incident light of three different wavelengths are staggered, achieving the purpose of focusing and achromatizing three wavelengths of light. The lens element provided by the present application has the potential to be applied in occasions requiring light splitting imaging, etc.

[0084] Please refer to Figure 10 , the present application also provides an optical imaging system 100, which comprises the lens element 110 as above.

[0085] Referring to Figure 11 The application also provides a laser radar 1001, which comprises the optical imaging system 100 as above.

[0086] In some embodiments of the application, the optical imaging system 100 is a light-splitting imaging system.

[0087] The laser radar 1001 can further comprise a transceiver system 200, etc. Details are not described here.

[0088] Referring to Figure 12 The application also provides a power-consuming device 1000, which comprises the laser radar 1001 as above or the optical imaging system 100 as above.

[0089] In the application, the power-consuming device 1000 can comprise a vehicle, a robot, an airborne laser radar system integrated on a drone or an aircraft, a wind-measuring laser radar, an intelligent traffic system, an industrial detection device, a security monitoring system, etc. In the embodiment, the power-consuming device 1000 is a vehicle.

[0090] In the description of the application, the terms “first” and “second” are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with “first” and “second” can explicitly or implicitly include one or more features. In the description of the application, the meaning of “multiple” is two or more, unless otherwise specifically limited.

[0091] In the above embodiments, the description of each embodiment is focused on, and the parts not described in detail in a certain embodiment can be referred to the relevant description of other embodiments.

[0092] The embodiments, implementation manners and related technical features of the application can be combined or replaced with each other without conflict.

[0093] The above is only the preferred embodiments of the application, and does not limit the application in any form. Although the description of each embodiment of the application is focused on, and the parts not described in detail in a certain embodiment can be referred to the relevant description of other embodiments, any modification, equivalent change and modification of the above embodiments according to the technical essence of the application are still within the scope of the technical solution of the application.

Claims

1. A lens element characterized by, The lens element comprises at least two phase control units, and the at least two phase control units are arranged at intervals. Each phase control unit corresponds to incident light with a specific wavelength, and the steering angles of different phase control units are different to control the phases of incident light with different wavelengths. The focal lengths of incident light with different wavelengths after passing through the corresponding phase control units are equal. The focal points of incident light with different wavelengths after passing through the corresponding phase control units are staggered.

2. The lens element of claim 1, wherein The sizes of each phase control unit are the same, and the sizes of different phase control units are different.

3. The lens element of claim 1, wherein The sizes of the phase control units are in the order of two-dimensional sub-wavelength.

4. The lens element of claim 1, wherein The focal points of incident light with different wavelengths after passing through the corresponding phase control units are staggered by r / n, where r is the equivalent radius of the lens element, and n is a positive integer.

5. The lens element according to any one of claims 1 to 4, wherein Each phase control unit comprises a substrate and a phase control structure, and the phase control structure is located on the substrate and extends along a first direction.

6. The lens element of claim 5, wherein The refractive index of the substrate is lower than that of the phase control structure.

7. The lens element of claim 5, wherein The phase control structure has a cross section perpendicular to the first direction. The shape of the cross section is anisotropic in at least two directions perpendicular to the first direction.

8. The lens element of claim 7, wherein The sizes of the phase control units for controlling the phases of incident light with different wavelengths are the same in the first direction. The sizes of the phase control units for controlling the phases of incident light with different wavelengths are different in at least one direction perpendicular to the first direction.

9. The lens element of claim 2, wherein The sizes of the phase control units increase with the increase of the wavelengths of the corresponding incident light.

10. The lens element of claim 5, wherein The phase control units for controlling the phases of incident light with different wavelengths are periodically arranged.

11. The lens element of claim 10, wherein, The lens element comprises a first phase control unit corresponding to incident light with a first wavelength and a second phase control unit corresponding to incident light with a second wavelength. The first phase control unit and the second phase control unit are arranged at intervals and periodically arranged along a direction.

12. The lens element of claim 11, wherein, The lens element further comprises a third phase control unit corresponding to incident light with a third wavelength, which is located on the side of the second phase control unit away from the first phase control unit. The first phase control unit, the second phase control unit and the third phase control unit are periodically arranged along a direction.

13. The lens element of claim 12, wherein, The lens element comprises a plurality of periodically arranged phase control unit groups, each of which comprises a plurality of first phase control units, a plurality of second phase control units and a plurality of third phase control units. Within the same phase control unit group, the plurality of first phase control units, the plurality of second phase control units and the plurality of third phase control units are arranged at intervals along the same direction.

14. The lens element of claim 13, wherein, In different phase control unit groups, the number of first phase control units, the number of second phase control units and the number of third phase control units are the same or different; and / or The number of the first phase control unit, the second phase control unit and the third phase control unit in the same phase control unit group is the same or different.

15. The lens element according to any one of claims 1 to 4, wherein The incident light is circularly polarized incident light.

16. The lens element of claim 5, wherein The phase control unit has a unit period, the unit period is of a sub-wavelength order, the size of the unit period is less than the wavelength of the incident light and greater than the size of the phase control unit in the direction perpendicular to the first direction.

17. An optical imaging system characterized by, An optical imaging system comprising a lens element as claimed in any of claims 1 to 16.

18. A lidar, comprising: An optical imaging system comprising a lens element as claimed in claim 17.

19. An electrical device, characterized by A lidar comprising a lens element as claimed in claim 18.

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