CN109669226B - Laser radar scanning device based on super-surface lens group array and design method thereof - Google Patents
Laser radar scanning device based on super-surface lens group array and design method thereof Download PDFInfo
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- G—PHYSICS
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- G02B3/00—Simple or compound lenses
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- G02B3/0037—Arrays characterized by the distribution or form of lenses
- G02B3/0062—Stacked lens arrays, i.e. refractive surfaces arranged in at least two planes, without structurally separate optical elements in-between
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- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
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- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
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- G01S7/4817—Constructional features, e.g. arrangements of optical elements relating to scanning
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- G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
- G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
- G02B26/10—Scanning systems
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Abstract
The invention discloses a laser radar scanning device based on a super-surface lens group array and a design method thereof. The device comprises two layers of parallel super-surface lens groups, wherein the first layer of super-surface lens realizes ideal focusing or diverging of vertical incidence parallel light beams, and the focus or virtual focus of the first layer of super-surface lens is on the front focal plane of the second layer of super-surface lens group. The second layer of super-surface lens group converts the light beam converged and then diverged by the first layer of super-surface lens or the directly diverged light beam into parallel light to be emitted; when the first layer of super-surface lens generates transverse displacement, the focal position generates the same transverse displacement, and for the second layer of super-surface lens group, the light wave emitted by a point on the front focal plane and off-axis is equivalent to a plane wave with a certain emergence angle through the lens; the lens group is arrayed, the light transmission caliber of the lens group is enhanced, and the high-speed, high-resolution and large-angle laser radar design under the condition of small displacement is realized.
Description
Technical Field
The invention belongs to the field of micro-nano optics and optical chip integration, and particularly relates to a laser radar scanning device based on a super-surface lens group array and a design method thereof.
Background
Laser radar (Light Detection And Ranging, abbreviated as Lidar) is an optical remote sensing technology for acquiring relevant information of a target by detecting the characteristics of scattered Light of a long-distance target. The laser radar is a product of combining the traditional radar technology and the modern laser technology, uses a laser beam as an information carrier, and can carry information by using the amplitude, the phase, the polarization and the frequency of light. Compared with the conventional microwave radar, the laser radar can obtain higher resolution and detect a finer target object. However, the conventional laser radar uses the high-speed rotation of the reflector to realize the beam scanning, and due to the speed limitation of the mechanical rotation, the laser radar cannot obtain a fast scanning frequency and a large scanning angle, so that the scanning positioning requirements of the wide high-speed object are disconnected to a certain extent, and the cost is high, so that the development of the laser radar is limited.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a laser radar scanning device based on a super-surface lens group array and a design method thereof.
The technical scheme adopted by the invention for solving the technical problems is as follows: a laser radar scanning device based on a super-surface lens group array comprises two layers of parallel super-surface lens group arrays, wherein a first layer of super-surface lens group array on an incidence surface realizes ideal focusing or divergence of vertical incidence parallel light beams, so that the focus or virtual focus of the vertical incidence parallel light beams is on the front focal plane of a second layer of super-surface lens group, and a second layer of super-surface lens group array on an emergence surface converts the light beams diverged after the first layer of super-surface lens group array converges or directly diverged light beams into parallel light to be emitted; when the first layer of super surface lens array generates transverse displacement, the focus position generates the same transverse displacement, and the light wave emitted by the off-axis point on the front focal plane is equivalent to a plane wave with a certain emergence angle after passing through the lens corresponding to the second layer of super surface lens array;
the first super-surface lens group array layer is composed of a first transparent substrate and a sub-wavelength microstructure on one side of the first transparent substrate, the transparent substrate is used for transmitting incident light and supporting the sub-wavelength microstructure, and the sub-wavelength microstructure is used for realizing phase modulation on light beams transmitted by the transparent substrate and is composed of a plurality of nano medium columns;
the second super-surface lens group array layer is composed of a second transparent substrate and sub-wavelength microstructures on two sides of the second transparent substrate, the transparent substrate is used for transmitting incident light and supporting the sub-wavelength microstructures, the sub-wavelength microstructures on the incident surface are used for collimating the incident light, the sub-wavelength microstructures on the emergent surface are used for correcting aberration of emergent light at different angles, and the sub-wavelength microstructures on the two sides are composed of a plurality of nano medium columns.
Furthermore, piezoelectric ceramics are loaded on the first layer of super-surface lens group array or the second layer of super-surface lens group array, so that the angle scanning of the emergent light beam is realized.
Furthermore, the device also comprises a super surface phase modulation layer which is arranged on a focusing plane between the first layer of super surface lens group array and the second layer of super surface lens group array and is used for realizing the phase compensation of the whole scanning device, thereby improving the resolution of the emergent light beam.
Furthermore, the lens aperture of the emergent surface of the first layer of super-surface lens group array is equal to the lens aperture of the incident surface of the second layer of super-surface lens group array, so that the utilization rate of light beams is improved; the ratio of the lens caliber of the emergent surface of the second layer of super-surface lens array to the lens caliber of the incident surface of the first layer of super-surface lens array is more than 1: 1.36 to eliminate multiple slit diffraction side lobes.
Further, the distance between the first layer of super-surface lens group array and the second layer of super-surface lens group array is equal to the sum of the focal length of the first layer of super-surface lens group array and the focal length of the second layer of super-surface lens group array, and the numerical apertures of the first layer of super-surface lens group array and the second layer of super-surface lens group array are equal to ensure that the exit surface of the second layer of super-surface lens group is filled with the pupil by the light beam, so that diffraction side lobes are reduced.
Furthermore, the lattice constant of the nano-medium column is smaller than the working wavelength, the transmission amplitude at the working wavelength is close to 1, and the transmission phases of the nano-medium columns with different sizes cover 0-2 pi.
Further, the arrangement of the nano-medium columns of each layer of the sub-wavelength microstructure satisfies the following conditions: different phases are compensated for each lattice position over the face to achieve the phase distribution requirements of each face design.
A design method of a laser radar scanning device based on a super-surface lens group array comprises the following steps:
and (1) determining the working wavelength, the scanning angle range and the scanning frequency of the scanning device according to the design index requirements and the process limitations, thereby calculating the structural size and the focal length of each lens in the two-layer super-surface lens group array, the working angle of each lens in the second-layer super-surface lens group array and the displacement required by the maximum scanning angle.
Simulating two layers of super-surface lens group arrays in ZEMAX by using a Binary optical element (Binary2) according to the structural parameters obtained by calculation in the step (1) to obtain ideal phase distribution and a structural light path diagram on the super surface; in the laser radar design, the optimized lenses need to be reversely arranged to serve as a second layer of super-surface lens group array.
And (3) calculating the transmission amplitude and the phase of the nano-medium columns with different sizes by using electromagnetic simulation software, wherein when the size of the nano-medium column is selected, the lattice constant of the nano-medium column is required to be smaller than the working wavelength, the transmission amplitude of the working wavelength is close to 1, and the transmission phase of the nano-medium columns with different sizes covers 0-2 pi.
And (4) designing a distribution mode of the nano medium columns according to the phase requirement of each lattice position of each layer of super surface lens group array.
And (5) applying piezoelectric ceramics on the single-layer super-surface lens array, and realizing the transverse movement of the super-surface lens array by using the change of signal voltage, so that the focused light wave is changed into parallel light with a certain emergence angle under the action of the second-layer super-surface lens array, and the two-dimensional large-angle scanning of the front object is realized by the two-dimensional movement of the super-surface array.
Further, the specific design method in the step (1) is as follows:
in the second layer of super surface lens group array, the working angle of each lens is equal to the designed scanning angle, the image height corresponding to the working angle is the required displacement, the caliber and the focal length of the incident surface of each lens are obtained by ZEMAX optimization, each lens in the second layer of super surface lens group array has the image height as small as possible in the required field of view by optimization, and the corresponding focal length and caliber are the designed optimal values at the moment.
Obtaining the relation between the focal length f and the displacement l of each lens in the second-layer super-surface lens group array by using the geometrical relation:
0.5*l/f＝tanθ (1)
where θ is the exit direction angle.
Therefore, the displacement amount in the structural parameters and the focal length value of each lens in the second-layer super-surface lens group array can be obtained, and the relation between the light ray emergence angle and the image height is not completely determined by the formula (1) due to the fact that actually designed lenses have distortion, but the formula determines an initial structural parameter.
The aperture of each lens of the first layer of super-surface lens group array is equal to the aperture of the incident surface of each lens of the second layer of super-surface lens group array so as to improve the utilization rate of light beams, and the numerical aperture of each lens of the first layer of super-surface lens group array is the same as that of each lens of the second layer of super-surface lens group array so as to determine the aperture and the focal length of each lens of the first layer of super-surface lens group array.
Further, in the step (2), the phase distribution of the super-surface is simulated by using a binary optical element, and the phase distribution is defined as an even polynomial of a radial coordinate:
φ(ρ)＝∑an(ρ/R)2n(2)
where R is the super-surface lens radius, ρ is the radial coordinate on the super-surface, coefficient anTo optimize the parameters for minimizing the focal point (root mean square of the focal point size) at the maximum angle of incidence, n is an even polynomial term, thereby resulting in an ideal phase distribution for each super-surface lens.
The invention has the beneficial effects that: through the combination of micro-nano optical technology and piezoceramics, use piezoceramics control microlens array to take place micro lateral displacement, can realize the transform to vertical incidence light wave exit angle, make full use of super surface microlens's high numerical aperture, can integrate and the automatically controlled displacement's of piezoceramics characteristics, can realize laser radar's big angle, high-frequency scanning, still have simultaneously light in weight, thickness are thin, can integrate advantages such as application to can control its cost in large-scale manufacturing. Therefore, the laser radar design based on the super surface lens group array provides a very effective solution to the problems faced at present.
Drawings
FIG. 1 is a schematic diagram of laser radar scanning using super surface lens array, where a and b are the first and second super surface lens array layers in design.
FIG. 2 is a schematic diagram of simulation optimization of a second-layer double-layer super-surface micro-lens set.
FIG. 3 is a diagram of a structure of a design cell and an array of cells of the same structure, where h is the height of the nano-scale lattice and d is the height of the nano-scale lattice1、d2The diameters of the central nano-pillar and the edge nano-pillar respectively, and p is the lattice period.
FIG. 4(a) is the results of transmittance and phase retardation values at 946nm wavelength for different radius combinations of composite building elements designed.
FIG. 4(b) is the results of transmittance and phase retardation values at 1550nm wavelength for different radius combinations of composite building blocks designed.
FIG. 5(a) is a fitting graph of radial phase distribution function of the super-surface micro-lens at 946nm light wave.
FIG. 5(b) is a fitting graph of radial phase distribution function of the super-surface micro-lens at 1550nm optical wave.
In fig. 6, (a) is a lower structure diagram of the artificial super surface lens array infrared microscope, (b) is a lower structure diagram of the artificial super surface lens array 100X visible light microscope, and (c) is a focusing condition of the artificial super surface lens array on incident infrared light.
Fig. 7(a) is a simulation diagram of beam transformation of the super-surface lens combination array without relative displacement.
FIG. 7(b) is a angular spectrum of the output light field of FIG. 7 (a).
Fig. 8(a) is a simulation diagram of beam transformation at maximum relative displacement for a combined super-surface lens array.
FIG. 8(b) is a angular spectrum of the output light field of FIG. 8 (a).
Detailed Description
The invention is described in further detail below with reference to the figures and specific examples.
The invention provides a laser radar scanning device based on a super-surface lens group array, which comprises two layers of parallel super-surface lens group arrays, wherein the first layer of super-surface lens group array on an incident surface realizes ideal focusing or divergence of vertical incident parallel light beams, so that the focus or virtual focus of the first layer of super-surface lens group array is on the front focal surface of the second layer of super-surface lens group, and the second layer of super-surface lens group array on an emergent surface converts the converged and diverged light beams of the first layer of super-surface lens group array or directly diverged light beams into parallel light to be emitted; when the first super surface lens group array generates the transverse displacement, the focus position generates the same transverse displacement, and the light wave emitted by the off-axis point on the front focal plane is equivalent to the light wave emitted by the off-axis point on the front focal plane corresponding to the second super surface lens group array, and the light wave is changed into the plane wave with a certain emergence angle after passing through the lens.
As shown in fig. 1, the first super-surface lens array a focuses the plane wave of vertical incidence on the front focal plane of the second super-surface lens array b, and the second super-surface lens array transforms the light wave into the plane wave.
When the first super surface lens group array generates the transverse displacement, the focus position generates the same transverse displacement, for the second super surface lens group array, the light wave emitted by the off-axis point on the front focal plane is equivalent to the plane wave with a certain emergence angle after passing through the lens.
The first super-surface lens group array is composed of a first transparent substrate and a sub-wavelength microstructure on one side of the first transparent substrate, the transparent substrate is used for transmitting incident light and supporting the sub-wavelength microstructure, and the sub-wavelength microstructure is used for realizing phase modulation on light beams transmitted by the transparent substrate and is composed of a plurality of nano medium columns.
The second super-surface lens group array layer is composed of a second transparent substrate and sub-wavelength microstructures on two sides of the second transparent substrate, the transparent substrate is used for transmitting incident light and supporting the sub-wavelength microstructures, the sub-wavelength microstructures on the incident surface are used for collimating the incident light, the sub-wavelength microstructures on the emergent surface are used for correcting aberration of emergent light at different angles, and the sub-wavelength microstructures on the two sides are composed of a plurality of nano medium columns.
Furthermore, piezoelectric ceramics are loaded on the first layer of super-surface lens group array or the second layer of super-surface lens group array, so that the angle scanning of the emergent light beam is realized.
Furthermore, the device also comprises a super surface phase modulation layer which is arranged on a focusing plane between the first layer of super surface lens group array and the second layer of super surface lens group array and is used for realizing the phase compensation of the whole scanning device, thereby improving the resolution of the emergent light beam.
Furthermore, the lens aperture of the emergent surface of the first layer of super-surface lens group array is equal to the lens aperture of the incident surface of the second layer of super-surface lens group array, so that the utilization rate of light beams is improved; the ratio of the lens caliber of the emergent surface of the second layer of super-surface lens array to the lens caliber of the incident surface of the first layer of super-surface lens array is more than 1: 1.36 to eliminate multiple slit diffraction side lobes.
Further, the distance between the first layer of super-surface lens group array and the second layer of super-surface lens group array is equal to the sum of the focal length of the first layer of super-surface lens group array and the focal length of the second layer of super-surface lens group array, and the numerical apertures of the first layer of super-surface lens group array and the second layer of super-surface lens group array are equal to ensure that the exit surface of the second layer of super-surface lens group is filled with the pupil by the light beam, so that diffraction side lobes are reduced.
Furthermore, the lattice constant of the nano-medium column is smaller than the working wavelength, the transmission amplitude at the working wavelength is close to 1, and the transmission phases of the nano-medium columns with different sizes cover 0-2 pi.
Further, the arrangement of the nano-medium columns of each layer of the sub-wavelength microstructure satisfies the following conditions: compensating for different phases at each lattice site over the entire face to achieve phase profile requirements for each face design
A laser radar design based on a super-surface lens group array specifically comprises the following steps:
and (1) determining the working wavelength, the scanning angle range and the scanning frequency of the scanning device according to the design index requirements and the process limitations, thereby calculating the structural size and the focal length of each lens in the two-layer super-surface lens group array, the working angle of each lens in the second-layer super-surface lens group array and the displacement required by the maximum scanning angle.
And (2) simulating the two-layer super-surface lens group array in ZEMAX by using a Binary optical element (Binary2) according to the structural parameters obtained by calculation in the step (1), so as to obtain ideal phase distribution on the super surface and a structural light path diagram. FIG. 2 is a light path diagram of a Zemax optimized double-layer super-surface lens assembly structure.
And (3) calculating the transmission amplitude and the phase of the nano-medium columns with different sizes by using electromagnetic simulation software, wherein when the size of the nano-medium column is selected, the lattice constant of the nano-medium column is required to be smaller than the working wavelength, the transmission amplitude of the working wavelength is close to 1, and the transmission phase of the nano-medium columns with different sizes covers 0-2 pi. Fig. 3 shows a designed dual-wavelength working composite nano-dielectric column unit cell, which is composed of two types of nano-dielectric columns, wherein h is the height of a nano-rod, d1 and d2 are the diameters of a central nano-dielectric column and an edge nano-dielectric column, respectively, and p is the lattice period. According to the phase value calculated by electromagnetic simulation software, selecting a nano-medium column with a proper structure (a composite nano-medium column structure is used in dual wavelength) as a basic unit of the medium-based artificial specific plane, wherein different transmission phases can be obtained by changing the parameters (d)1，d2) The realization is that the parameter combination (d) of the composite structure unit cell is shown in FIG. 4(a) and FIG. 4(b)1，d2) The transmission amplitude and phase values at the two wavelengths are indexed.
And (4) designing a distribution mode of the nano medium columns according to the phase requirement of each lattice position of each layer of super surface lens group array. FIG. 5(a) and FIG. 5(b) are graphs of fitting effects of the transmission phase function at 946nm and 1550nm in the radial direction of the super-surface microlens using the results of FIG. 4(a) and FIG. 4(b), respectively. FIG. 6 is a drawing of an experimental sample of a super-surface lens array.
And (5) applying piezoelectric ceramics on the single-layer super-surface lens array, and realizing the transverse movement of the super-surface lens array by using the change of signal voltage, so that the focused light wave is changed into parallel light with a certain emergence angle under the action of the second-layer super-surface lens array, and the two-dimensional large-angle scanning of the front object is realized by the two-dimensional movement of the super-surface array.
As shown in the simulation results of fig. 7(a) and 7(b), when the first super-surface microlens has a slight lateral displacement, the light wave passing through the second super-surface microlens set will be deflected. Fig. 7(a) shows the output optical field angle spectrum of fig. 7(a) when the light wave is emitted vertically without displacement. Fig. 8(a) is a simulated optical path diagram when the lens array is displaced, and fig. 8(b) is an output field angle spectrum diagram of fig. 8 (a).
Further, the specific design method in the step (1) is as follows:
in the second layer of super surface lens group array, the working angle of each lens is equal to the designed scanning angle, the image height corresponding to the working angle is the required displacement, the caliber and the focal length of the incident surface of each lens are obtained by ZEMAX optimization, each lens in the second layer of super surface lens group array has the image height as small as possible in the required field of view by optimization, and the corresponding focal length and caliber are the designed optimal values at the moment.
Obtaining the relation between the focal length f and the displacement l of each lens in the second-layer super-surface lens group array by using the geometrical relation:
0.5*l/f＝tanθ (1)
where θ is the exit direction angle.
Therefore, the displacement amount in the structural parameters and the focal length value of each lens in the second-layer super-surface lens group array can be obtained, and the relation between the light ray emergence angle and the image height is not completely determined by the formula (1) due to the fact that actually designed lenses have distortion, but the formula determines an initial structural parameter.
The aperture of each lens of the first layer of super-surface lens group array is equal to the aperture of the incident surface of each lens of the second layer of super-surface lens group array so as to improve the utilization rate of light beams, and the numerical aperture of each lens of the first layer of super-surface lens group array is the same as that of each lens of the second layer of super-surface lens group array so as to determine the aperture and the focal length of each lens of the first layer of super-surface lens group array.
Further, in the step (2), the phase distribution of the super-surface is simulated by using a binary optical element, and the phase distribution is defined as an even polynomial of a radial coordinate:
φ(ρ)＝∑an(ρ/R)2n(2)
where R is the super-surface lens radius, ρ is the radial coordinate on the super-surface, coefficient anTo optimize the parameters for minimizing the focal point (root mean square of the focal point size) at the maximum angle of incidence, n is an even polynomial term, thereby resulting in an ideal phase distribution for each super-surface lens.
The above-described embodiments are intended to illustrate rather than to limit the invention, and any modifications and variations of the present invention are within the spirit of the invention and the scope of the appended claims.
Claims (10)
1. A laser radar scanning device based on a super-surface lens group array is characterized by comprising two layers of parallel super-surface lens group arrays, wherein a first layer of super-surface lens group array on an incident surface realizes ideal focusing or divergence of vertical incident parallel light beams, so that the focus or virtual focus of the first layer of super-surface lens group array is on the front focal surface of a second layer of super-surface lens group, and a second layer of super-surface lens group array on an emergent surface converts the converged and diverged light beams of the first layer of super-surface lens group array or directly diverged light beams into parallel light for emergence; when the first layer of super surface lens array generates transverse displacement, the focus position generates the same transverse displacement, and the light wave emitted by the off-axis point on the front focal plane is equivalent to a plane wave with a certain emergence angle after passing through the lens corresponding to the second layer of super surface lens array; the transverse displacement is specifically as follows: the piezoelectric ceramics acts on the single-layer super-surface lens array, and the transverse movement of the super-surface lens array is realized by utilizing the change of signal voltage, so that the focused light wave is changed into parallel light with a certain emergence angle under the action of the second-layer super-surface lens array, and the two-dimensional large-angle scanning of a front object is realized by the two-dimensional movement of the super-surface array;
the first super-surface lens group array layer is composed of a first transparent substrate and a sub-wavelength microstructure on one side of the first transparent substrate, the transparent substrate is used for transmitting incident light and supporting the sub-wavelength microstructure, and the sub-wavelength microstructure is used for realizing phase modulation on light beams transmitted by the transparent substrate and is composed of a plurality of nano medium columns;
the second super-surface lens group array layer is composed of a second transparent substrate and sub-wavelength microstructures on two sides of the second transparent substrate, the transparent substrate is used for transmitting incident light and supporting the sub-wavelength microstructures, the sub-wavelength microstructures on the incident surface are used for collimating the incident light, the sub-wavelength microstructures on the emergent surface are used for correcting aberration of emergent light at different angles, and the sub-wavelength microstructures on the two sides are composed of a plurality of nano medium columns.
2. The lidar scanning device based on super surface lens group array according to claim 1, wherein piezoelectric ceramics are loaded on the first layer super surface lens group array or the second layer super surface lens group array to realize the angle scanning of the emergent beam.
3. The lidar scanning device based on super surface lens group array according to claim 1, characterized in that, the device further comprises a super surface phase modulation layer arranged on the focusing plane between the first layer of super surface lens group array and the second layer of super surface lens group array, for realizing the phase compensation of the whole scanning device, thereby improving the resolution of the emergent beam.
4. The lidar scanning device based on super surface lens group array according to claim 1, wherein the lens aperture of the emergent surface of the first super surface lens group array is equal to the lens aperture of the incident surface of the second super surface lens group array, so as to improve the utilization rate of the light beam; the ratio of the lens caliber of the emergent surface of the second layer of super-surface lens array to the lens caliber of the incident surface of the first layer of super-surface lens array is more than 1: 1.36 to eliminate multiple slit diffraction side lobes.
5. The lidar scanning device according to claim 1, wherein the distance between the first super surface lens array and the second super surface lens array is equal to the sum of the focal length of the first super surface lens array and the focal length of the second super surface lens array, and the numerical apertures of the first super surface lens array and the second super surface lens array are equal to ensure that the exit surface of the second super surface lens array is filled with the pupil and the diffraction side lobe is reduced.
6. The lidar scanning device based on super surface lens group array according to claim 1, characterized in that the lattice constant of the nano-medium columns is smaller than the working wavelength, the transmission amplitude at the working wavelength is close to 1, and the transmission phase of the nano-medium columns with different sizes covers 0-2 pi.
7. The lidar scanning device based on super surface lens group array according to claim 1, wherein the nano medium columns of each layer of sub-wavelength microstructure are arranged to satisfy: different phases are compensated for each lattice position over the face to achieve the phase distribution requirements of each face design.
8. A method of designing a lidar scanning device according to any of claims 1 to 7, comprising the steps of:
determining the working wavelength, the scanning angle range and the scanning frequency of a scanning device according to design index requirements and process limitations, and thus calculating the structure size and the focal length of each lens in a two-layer super-surface lens group array, the working angle of each lens in a second-layer super-surface lens group array and the displacement required by the maximum scanning angle;
simulating two layers of super-surface lens group arrays in ZEMAX by using a Binary optical element (Binary2) according to the structural parameters obtained by calculation in the step (1) to obtain ideal phase distribution and a structural light path diagram on the super surface; in the laser radar design, optimized lenses need to be reversely arranged to serve as a second layer of super-surface lens group array;
step (3) calculating the transmission amplitude and phase of the nano-medium columns with different sizes by using electromagnetic simulation software, wherein when the size of the nano-medium column is selected, the requirement that the lattice constant of the nano-medium column is smaller than the working wavelength is met, the transmission amplitude of the working wavelength is close to 1, and the transmission phase of the nano-medium columns with different sizes covers 0-2 pi is met;
step (4), designing a distribution mode of the nano medium columns according to the phase requirement of each lattice position of each layer of super surface lens group array;
and (5) applying piezoelectric ceramics on the single-layer super-surface lens array, and realizing the transverse movement of the super-surface lens array by using the change of signal voltage, so that the focused light wave is changed into parallel light with a certain emergence angle under the action of the second-layer super-surface lens array, and the two-dimensional large-angle scanning of the front object is realized by the two-dimensional movement of the super-surface array.
9. The method according to claim 8, wherein the step (1) is specifically designed as follows:
in the second layer of super-surface lens group array, the working angle of each lens is equal to the designed scanning angle, the image height corresponding to the working angle is the required displacement, the caliber and the focal length of the incident surface of each lens are obtained by ZEMAX optimization, each lens in the second layer of super-surface lens group array has the image height as small as possible in the required field of view through optimization, and the corresponding focal length and caliber are the designed optimal values at the moment;
obtaining the relation between the focal length f and the displacement l of each lens in the second-layer super-surface lens group array by using the geometrical relation:
0.5*l/f＝tanθ (1)
wherein θ is the exit direction angle;
therefore, the displacement in the structural parameters and the focal length value of each lens in the second-layer super-surface lens group array can be obtained, and the relation between the light ray emergence angle and the image height is not completely determined by the formula (1) due to the fact that actually designed lenses have distortion, but the formula determines an initial structural parameter;
the aperture of each lens of the first layer of super-surface lens group array is equal to the aperture of the incident surface of each lens of the second layer of super-surface lens group array so as to improve the utilization rate of light beams, and the numerical aperture of each lens of the first layer of super-surface lens group array is the same as that of each lens of the second layer of super-surface lens group array so as to determine the aperture and the focal length of each lens of the first layer of super-surface lens group array.
10. The method of claim 8, wherein in step (2), the phase profile of the super-surface is modeled with a binary optical element, the phase profile being defined as an even polynomial of radial coordinates:
φ(ρ)＝∑an(ρ/R)2n(2)
where R is the super-surface lens radius, ρ is the radial coordinate on the super-surface, coefficient anTo optimize the parameters for minimizing the focal point at the maximum angle of incidence, n is an even polynomial term, thereby resulting in an ideal phase distribution for each super-surface lens.
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| CN110609386B (en) * | 2019-08-16 | 2020-10-13 | 浙江大学 | Design method and application of small-F-number large-depth-of-field lens based on superlens |
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| CN111190164B (en) * | 2020-02-21 | 2022-03-29 | 奥比中光科技集团股份有限公司 | Scanning device and scanning method |
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