Lidar beam scanning system based on combination of hyperlens and refractive lens

Abstract

The application discloses a laser radar beam scanning system based on a combination of a super lens and a refractive lens, which comprises laser radars, refractive lenses and super lenses arranged at intervals; scanning beams with different exit angles of the laser radars are focused by the refractive lenses and then deflected by the super lenses; wherein the super lens has a nano structure layer composed of a nano structure array, and the deflection angles of all scanning angles are equal to a target deflection angle through weighting optimization of the deflection angle and the divergence angle. The nano structure layer can realize large-angle deflection of the scanning beams, is not sensitive to the polarization angle, solves the problem that the existing laser radar beam scanning system cannot simultaneously realize large scanning angle, small system volume, high scanning speed, high resolution and long detection distance, is favorable for realizing high-performance beam scanning effect and can meet the beam processing of various scanning angles.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of micro-nano optical technology, and in particular to a laser radar beam scanning system based on a combination of superlenses and refractive lenses. BACKGROUND

[0002] With the continuous progress of society, emerging fields such as wearable near-eye displays, autonomous vehicles, and satellite imaging are emerging, and the demand for small and lightweight optical systems is becoming increasingly urgent. Among the many optical systems, refractive lenses play a core role and are important traditional optical elements. However, the traditional aberration-corrected refractive lens system is relatively large in size and weight, which is contrary to the current demand for small and lightweight. Fortunately, existing optical design technology and micro-nano processing technology can effectively solve this problem.

[0003] A superlens is an array of subwavelength structures that play a key role in regulating the phase, amplitude, and polarization of light. By carefully designing the basic atomic structure and its distribution on the plane surface, the wavefront shape can be adjusted at will. The multiple advantages of superlenses, such as lightness, compactness, economy, design freedom, and high focusing quality, make them gradually replace traditional optical lenses and become the first choice. This trend is consistent with the current development direction of pursuing miniaturization and lightweight of optical systems, providing new possibilities for various modern optical applications.

[0004] Laser radar is an advanced detection method combining laser technology and modern photoelectric detection technology, composed of a transmitting system, a receiving system, and an information processing system. Laser radar uses transmitted laser beams to detect targets and obtain characteristic information such as the position and speed of the target from the reflected light. The wavelength used by laser radar is usually 800-1550 nm, and the current mainstream wavelengths are 905 nm and 1550 nm. The main evaluation indicators of laser radar include detection distance, scanning angle, resolution, scanning rate, etc.

[0005] Traditional laser radar systems based on mechanical structure beam scanning modules have complex structures, difficult assembly, large size, high power consumption, high cost, and low scanning rate, making it difficult to meet the modern demand for small and lightweight. Compared with mechanical beam scanning laser radar, all-solid-state laser radar has the advantages of compactness, stability, durability, and speed, gradually entering the field of view of researchers. Among them, the most typical is silicon-based optical phased array (OPA). Currently, silicon-based OPA can achieve one-dimensional scanning with a large angle and high precision. However, OPA still has the problem of insufficient field of view angle, and the scanning angle of high-resolution laser radar is generally within 10°. Therefore, how to increase the scanning angle of two-dimensional laser radar while maintaining high resolution and compact structure has become a problem to be solved.

[0006] Some solutions have been proposed to solve the above problems, such as a cascaded liquid crystal polarization grating, which can increase the deflection momentum through the grating structure, without sacrificing the scanning accuracy, but is limited by the deflection speed of the liquid crystal molecules (<1 kHz). The traditional inverted telescope structure will not reduce the scanning speed, but will increase the system volume. And using the super lens optical system, due to the process limitation, it is difficult to manufacture a large aperture (centimeter level) super lens, so it cannot be applied to large aperture laser radar, which limits its detection distance. The patent combines the super lens and the refractive lens, without reducing the scanning speed, greatly reducing the system volume compared to the pure refractive lens system, and can be applied to large aperture laser radar, with long detection distance, which has important scientific significance and practical value.

[0007] The information disclosed in this BACKGROUND section is only for the purpose of increasing the understanding of the background of the application and should not be taken as an acknowledgment or any form of suggestion that this information forms prior art with respect to any country. SUMMARY

[0008] The technical problem to be solved by the present application is how to solve the problem that the current laser radar beam scanning system cannot simultaneously realize large scanning angle, small system volume, large aperture, high scanning speed and high resolution.

[0009] The present application solves the above technical problems by the following technical means: a laser radar beam scanning system based on the combination of super lens and refractive lens, which comprises small emission angle OPA laser radars arranged at intervals, a refractive lens group and a super lens; the scanning beams of different emission angles of the laser radar are focused by the refractive lens group and then deflected by the super lens; wherein the super lens has a nano structure layer composed of a nano structure array, and the deflection angle and the divergence angle are optimized to make the deflection angles of all scanning angles equal to the target deflection angle.

[0010] Further, the scanning beams emitted by the laser radar include positive scanning beams and oblique scanning beams, which meet the beam processing of various scanning angles.

[0011] Further, the super lens comprises a substrate layer and a nano structure layer; the substrate layer is used for transmitting light beams, and the nano structure layer is located above the substrate layer and is used for realizing light beam deflection.

[0012] Further, the nano structure layer is composed of a periodic nano structure array to realize the light beam deflection function.

[0013] Further, the nano structure array satisfies the following phase distribution:

[0014]

[0015] wherein, for the phase distribution of the nanostructure array, λ is the wavelength of the scanning beam, r is the actual ring radius, and f is the focal length coefficient.

[0016] Further, the focal length coefficient f is adjusted to reduce the optimization of the following function FOM:

[0017]

[0018] where i is the different exit angle of the laser radar, is the deflection angle weight, θ i is the deflection angle, θ i,target is the target deflection angle, is the divergence angle weight, α i is the divergence angle, and the target divergence angle is 0; the optimization target is to make the deflection angle of the light beam at all scanning angles equal to the target deflection angle, and the divergence angle as small as possible.

[0019] Further, the diameter of the nanostructure array is 1-10mm.

[0020] Further, the refractive lens group comprises one or more refractive lenses.

[0021] The beneficial effects of the present application are:

[0022] (1) The present application uses the exit scanning beam of the laser radar, and the scanning beam is first refracted by the refractive lens, and then enters the substrate layer and the nanostructure layer of the superlens. The nanostructure layer can realize large-angle deflection of the scanning beam, and the polarization angle is not sensitive. The problem that the existing laser radar beam scanning system cannot simultaneously realize large scanning angle, small system volume, high scanning speed, high resolution, and long detection distance is solved. It is beneficial to realize high-performance beam scanning effect and can meet the beam processing of various scanning angles.

[0023] (2) In the laser radar beam scanning system based on the combination of the superlens and the refractive lens, the polarization angle of the laser emitted by the laser radar has no effect on the imaging result, and the polarization angle is not sensitive.

[0024] (3) The laser radar beam scanning system based on the combination of the superlens and the refractive lens has few structural parts, and uses a single refractive lens (which can be multiple) and a single superlens to realize beam deflection, which meets the current requirements for small and lightweight optical devices, and is easy to integrate into detection equipment such as autonomous driving vehicles and aircraft. While increasing the scanning angle, the volume and weight are reduced. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0026] Figure 1 is a structural schematic diagram of a laser radar beam scanning system based on a combination of superlenses and refractive lenses according to an embodiment of the present application;

[0027] Figure 2 is a top view of a nanostructure array according to an embodiment of the present application;

[0028] Figure 3 is a working schematic diagram of a laser radar beam scanning system based on a combination of superlenses and refractive lenses according to an embodiment of the present application;

[0029] Figure 4 is a 1000m far point spread function image of a laser radar beam scanning system based on a combination of superlenses and refractive lenses under a 0° scanning angle in the y direction at a 1550nm wavelength band;

[0030] Figure 5 is a 1000m far x direction intensity image of a laser radar beam scanning system based on a combination of superlenses and refractive lenses under a 0° scanning angle in the y direction at a 1550nm wavelength band;

[0031] Figure 6 is a 1000m far y direction intensity image of a laser radar beam scanning system based on a combination of superlenses and refractive lenses under a 0° scanning angle in the y direction at a 1550nm wavelength band;

[0032] Figure 7 is a 1000m far point spread function image of a laser radar beam scanning system based on a combination of superlenses and refractive lenses under a 0.5° scanning angle in the y direction at a 1550nm wavelength band;

[0033] Figure 8 is a 1000m far x direction intensity image of a laser radar beam scanning system based on a combination of superlenses and refractive lenses under a 0.5° scanning angle in the y direction at a 1550nm wavelength band;

[0034] Figure 9 is a 1000m far y direction intensity image of a laser radar beam scanning system based on a combination of superlenses and refractive lenses under a 0.5° scanning angle in the y direction at a 1550nm wavelength band;

[0035] Figure 10is a 1000m far point spread function image under a 1° scanning angle in the y direction at a 1550nm waveband of a laser radar beam scanning system based on a combination of a superlens and a refractive lens;

[0036] Figure 11 is a 1000m far x direction intensity image under a 1° scanning angle in the y direction at a 1550nm waveband of a laser radar beam scanning system based on a combination of a superlens and a refractive lens;

[0037] Figure 12 is a 1000m far y direction intensity image under a 1° scanning angle in the y direction at a 1550nm waveband of a laser radar beam scanning system based on a combination of a superlens and a refractive lens;

[0038] Figure 13 is a 1000m far point spread function image under a 1.5° scanning angle in the y direction at a 1550nm waveband of a laser radar beam scanning system based on a combination of a superlens and a refractive lens;

[0039] Figure 14 is a 1000m far x direction intensity image under a 1.5° scanning angle in the y direction at a 1550nm waveband of a laser radar beam scanning system based on a combination of a superlens and a refractive lens;

[0040] Figure 15 is a 1000m far y direction intensity image under a 1.5° scanning angle in the y direction at a 1550nm waveband of a laser radar beam scanning system based on a combination of a superlens and a refractive lens;

[0041] In the figure, the label: 100, laser radar; 200, refractive lens; 300, superlens; 310, base layer; 320, nanostructure layer; S, scanning beam; S1, positive scanning beam; S2, oblique scanning beam. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0043] Embodiment one:

[0044] The present application provides a laser radar beam scanning system based on a combination of a superlens and a refractive lens, as shown in Figure 1 including laser radars 100, refractive lenses 200 and superlenses 300 arranged at intervals.

[0045] LiDAR 100 is used to emit a scanning beam S;

[0046] The refractive lens 200 is arranged at intervals with the lidar 100 to receive and focus the scanning beam S emitted by the lidar 100. The refractive lens can be replaced by a system composed of several refractive lenses. Optimization tests show that sometimes adding several refractive lenses can reduce the system size without changing the function.

[0047] The superlens 300 is arranged at intervals with the refracting lens 200 and is used to receive the focused beam of the refracting lens 200 and deflect the beam.

[0048] In this embodiment, the scanning beam S includes a normal scanning beam S1 and an oblique scanning beam S2, thereby enabling beam processing at various scanning angles and achieving beam deflection effects at different scanning angles.

[0049] In this embodiment, as Figure 2 As shown, the superlens 300 includes a substrate layer 310 and a nanostructure layer 320; the substrate layer 310 is used to transmit light beams and is made of a low-loss material with a low dielectric constant, such as quartz glass; the nanostructure layer 320 is located above the substrate layer 310 and is connected to the bottom surface of the substrate layer 310 to achieve light beam deflection.

[0050] The nanostructure layer 320 is designed with the LiDAR wavelength as the center wavelength. By periodically arranging the nanostructure array, the beam deflection function is achieved. The diameter of the nanostructure array is 1-10 mm.

[0051] To meet the requirements for beam deflection, the nanostructure array satisfies the following phase distribution, and beam deflection is achieved by setting the phase:

[0052]

[0053] in, λ represents the phase distribution of the nanostructure array, λ is the scanning beam wavelength, r is the actual ring radius, and f is the focal length coefficient.

[0054] The focal length coefficient f is determined by optimizing the final deflection angle and divergence angle of the scanning beam from the lidar at different exit angles after passing through the system. The optimization function is as follows:

[0055]

[0056] Where i represents different emission angles of the lidar. As the weight of the deflection angle, θ i For the deflection angle, θ i,target For the target deflection angle, For the divergence angle weight, α iFor the divergence angle, the target divergence angle is 0 (the target is finally a parallel light beam). The smaller the deflection angle is from the target deflection angle and the smaller the divergence angle is, indicating that the deflection effect is better, so the focal length coefficient f of the nano structure array is adjusted to adjust the phase, and the deflection angle is changed by adjusting the phase i and the divergence angle i to reduce the optimization function FOM, and at the same time adjust and so that the deflection angle of the light beam at all scanning angles is equal to the target deflection angle, and the divergence angle is as small as possible, that is, the light beam has a good deflection effect in the scanning angle range of the laser radar, and a large-angle light beam scanning is realized.

[0057] The nano structure layer 320 can be made of the same material or different materials, and the preparation material can be a high dielectric constant, low loss visible light medium material or a semiconductor material, such as monocrystalline silicon, titanium dioxide or silicon nitride, etc. In this embodiment, the nano structure layer 320 is made of monocrystalline silicon. The cross-sectional shape of the nano column of the nano structure layer 320 can be a square, a circular or a hole structure, etc., which can be designed according to the actual functional effect.

[0058] The present application can realize large-angle deflection of the scanning light beam by the laser radar, and the scanning light beam is first refracted by the refractive lens, and then enters the substrate layer and the nano structure layer of the super lens. The nano structure layer can realize large-angle deflection of the scanning light beam, and the polarization angle is not sensitive. The problem that the existing laser radar beam scanning system cannot simultaneously realize large scanning angle, small system volume, high scanning speed, high resolution and long detection distance is solved, which is conducive to realizing high-performance beam scanning effect and can meet the beam processing of various scanning angles.

[0059] The working process of this embodiment is as follows:

[0060] Referring to Figure 3 Fig. 1, in the laser radar beam scanning system based on the combination of the super lens and the refractive lens, the laser radar 100 emits a normal scanning light beam S1 and an oblique scanning light beam S2, which are incident on the refractive lens 200. After the scanning light beams with different angles pass through the refractive lens 200, they pass through the substrate layer 310 of the super lens and are incident on different positions (different radius rings) of the nano structure layer 320 of the super lens, to perform beam deflection. The light beams with different scanning angles are deflected to different angles to be approximately parallel light, thereby realizing a large-angle beam scanning effect.

[0061] Embodiment two:

[0062] In this embodiment, the wavelength of the laser radar selected for the test is 1550 nm based on the above-mentioned embodiment.

[0063] The laser radar 100 has a beam exit diameter of 15 mm; the refractive lens 200 has a diameter of 20 mm; the superlens base layer 310 is made of silicon dioxide and has a thickness of 0.5 mm; and the nanostructure layer 320 is made of monocrystalline silicon and has a diameter of 1 mm.

[0064] As shown in FIG. 8, the point spread function image of the laser radar beam scanning system based on the combination of the superlens and the refractive lens at a distance of 1000 m under a scanning angle of 0° in the y direction is as shown in FIG. 9, the x-direction intensity image is as shown in FIG. 10, the y-direction intensity image is as shown in FIG. 11, the center in the x direction is 0.000 m, the FWHM is 1.704 m, the deflection angle is 0.000°, and the divergence angle is 0.098°, and the center in the y direction is 0.000 m, the FWHM is 1.704 m, the deflection angle is 0.000°, and the divergence angle is 0.098°. Figure 4 Figure 5 Figure 6

[0065] As shown in FIG. 12, the point spread function image of the laser radar beam scanning system based on the combination of the superlens and the refractive lens at a distance of 1000 m under a scanning angle of 0.5° in the y direction is as shown in FIG. 13, the x-direction intensity image is as shown in FIG. 14, the y-direction intensity image is as shown in FIG. 15, the center in the x direction is 0.000 m, the FWHM is 2.105 m, the deflection angle is 0.000°, and the divergence angle is 0.121°, and the center in the y direction is 170.6 m, the FWHM is 2.406 m, the deflection angle is 9.684°, and the divergence angle is 0.134°. Figure 7 Figure 8 Figure 9

[0066] As shown in FIG. 16, the point spread function image of the laser radar beam scanning system based on the combination of the superlens and the refractive lens at a distance of 1000 m under a scanning angle of 1° in the y direction is as shown in FIG. 17, the x-direction intensity image is as shown in FIG. 18, the y-direction intensity image is as shown in FIG. 19, the center in the x direction is 0.000 m, the FWHM is 3.108 m, the deflection angle is 0.000°, and the divergence angle is 0.178°, and the center in the y direction is 356.4 m, the FWHM is 4.010 m, the deflection angle is 19.618°, and the divergence angle is 0.204°. Figure 10 Figure 11 Figure 12

[0067] As shown in FIG. 20, the point spread function image of the laser radar beam scanning system based on the combination of the superlens and the refractive lens at a distance of 1000 m under a scanning angle of 1.5° in the y direction is as shown in FIG. 21, the x-direction intensity image is as shown in FIG. 22, the y-direction intensity image is as shown in FIG. 23, the center in the x direction is 0.000 m, the FWHM is 3.108 m, the deflection angle is 0.000°, and the divergence angle is 0.178°, and the center in the y direction is 356.4 m, the FWHM is 4.010 m, the deflection angle is 19.618°, and the divergence angle is 0.204°. Figure 13 Figure 14 Figure 15 ​​​​​​​​​​​As shown, the x-direction center is 0.000 m, the FWHM is 4.712 m, the deflection angle is 0.000°, the divergence angle is 0.270°, the y-direction center is 578.6 m, the FWHM is 8.822 m, the deflection angle is 30.056°, and the divergence angle is 0.379°.

[0068] According to the above test results, for a scanning angle of 0-1.5°, the deflection angle of the laser radar beam scanning system based on the combination of the super lens and the refractive lens is 0-30°, a 20-fold scanning angle magnification is achieved, the divergence angle increases with the increase of the deflection angle, and the maximum does not exceed 0.3°, the spot size at a distance of 1000 m is less than 9 m, and the deflection effect is good.

[0069] The laser radar beam scanning system based on the combination of the super lens and the refractive lens has few structural parts, uses a single refractive lens (which can be multiple) and a single super lens to realize beam deflection, meets the current requirements for small and lightweight optical devices, is easy to integrate into detection equipment such as autonomous driving vehicles and aircraft, increases the scanning angle while reducing the volume and weight, solves the problem that the existing laser radar beam scanning system cannot simultaneously achieve large scanning angle, small system volume, high scanning speed, high resolution, long detection distance, is conducive to achieving high-performance beam scanning effect, and can meet the beam processing of various scanning angles.

[0070] The above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A lidar beam scanning system based on a combination of a metalens and a refractive lens, characterized in that, The system comprises a laser radar, a refractive lens group and a superlens arranged at intervals; the scanning beams emitted by the laser radar include normal scanning beams and oblique scanning beams, which meet the beam processing of various scanning angles; the scanning beams of different emission angles of the laser radar are focused by the refractive lens group and then deflected by the superlens; wherein the superlens has a nanostructure layer composed of a nanostructure array, and the deflection angles of all scanning angles are equal to the target deflection angle through the empowerment optimization of the deflection angle and the divergence angle; the nanostructure layer is composed of a periodic nanostructure array to realize the light beam deflection function. The phase distribution satisfied by the nanostructure array is as follows: ； wherein is the phase distribution of the nanostructure array, is the wavelength of the scanning beam, is the actual annulus radius, is the focal length coefficient; Adjusting focal length coefficients to reduce the following optimization function : ； wherein, is the different exit angle of the laser radar, is the deflection angle weight, is the deflection angle, is the target deflection angle, is the divergence angle weight, is the divergence angle, and the target divergence angle is 0; the optimization target is to make the deflection angle of the light beam equal to the target deflection angle at all scanning angles, and the divergence angle is as small as possible.

2. The laser radar beam scanning system based on the combination of the superlens and the refractive lens according to claim 1, characterized in that, The superlens comprises a substrate layer and a nanostructure layer; the substrate layer is used for transmitting light beams, and the nanostructure layer is located above the substrate layer and is used for realizing light beam deflection.

3. The laser radar beam scanning system based on the combination of the superlens and the refractive lens according to claim 1, characterized in that, The diameter of the nanostructure array is 1-10mm.

4. The laser radar beam scanning system based on the combination of the superlens and the refractive lens according to claim 1, characterized in that, The refractive lens group comprises one or more refractive lenses.

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