Linear laser homogenizer and lidar

Abstract

The application discloses a linear laser homogenizer and a laser radar, and relates to the technical field of laser radars.The linear laser homogenizer comprises a substrate and a plurality of nano-pillar structure units arranged on the surface of the substrate, the plurality of nano-pillar structure units are arranged in an array, and the array arrangement mode of the plurality of nano-pillar structure units is calculated according to the parallel relationship between the propagation direction of light and the phase gradient of an optical wave field.The linear laser homogenizer is based on the super-structured surface array structure formed by the nano-pillar structure units and the substrate, the array mode of the nano-pillar structure units is calculated according to the parallel relationship between the propagation direction of light and the phase gradient of an optical wave field, and the linear divergence homogenization of laser can be realized.The application constructs a super-structured surface by using the nano-pillar structure units, and realizes the linear laser homogenization while having the integration of ultra-lightness and ultra-thinness.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser radar, in particular to a linear laser homogenizer and laser radar. BACKGROUND

[0002] Laser radar is a remote sensing technology that measures the distance of a target and obtains target information by emitting a laser beam. Laser radar linear scanning technology is a kind of laser radar technology that obtains three-dimensional spatial information of a target through linear scanning, can quickly obtain a large amount of point cloud data, form a three-dimensional surface model of the target object, and has the characteristics of high precision, high resolution and high efficiency. The design and performance of the beam homogenization shaping device in the laser radar optical system directly affect the scanning efficiency, resolution and accuracy of the laser radar system, but currently such devices have the common problems of high cost, complex processing and low integration. SUMMARY

[0003] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application proposes a linear laser homogenizer and laser radar, which can realize homogenization shaping function and improve the integration of the laser radar system.

[0004] In a first aspect, the linear laser homogenizer according to the embodiments of the present application comprises: a substrate and a plurality of nano-pillar structure units arranged on the surface of the substrate, the plurality of nano-pillar structure units are arranged in an array, and the array arrangement mode of the plurality of nano-pillar structure units is calculated according to the parallel relationship between the propagation direction of light and the phase gradient of the optical wave field. Each nano-pillar structure unit is composed of the relative stacking of the upper surfaces of two circular truncated cones with consistent geometric parameters, and any cross section is circular.

[0005] According to some embodiments of the present application, the parallel relationship between the propagation direction of light and the phase gradient of the optical wave field is:

[0006] ;

[0007] wherein, is the wavelength of the light, the propagation coordinates of the light are , and the normal vector of the phase curve of the optical wave field is ; p is the arrangement period of the nano-pillar structure unit, P is the side length of the equal-area region divided on the target surface, and the calculation formula of P is:

[0008] ;

[0009] wherein, α is the target divergence half-angle, d is the distance between the superstructure surface and the target surface, and x is the number of equal-area regions divided on the target surface.

[0010] According to some embodiments of the present application, the radius of the upper and lower ends of the nano-pillar structure unit ranges from 40nm to 140nm, and the tapered radius ranges from 20nm to 120nm.

[0011] According to some embodiments of the present application, the difference between the end surface radius of the upper and lower ends of the nano-pillar structure unit and the tapered radius ranges from 20nm to 25nm.

[0012] According to some embodiments of the present application, the substrate is made of silicon dioxide.

[0013] According to some embodiments of the present application, the material of the nano-pillar structure unit is amorphous silicon.

[0014] According to some embodiments of the present application, the arrangement of the nano-pillar structure unit is determined according to the target divergence angle.

[0015] According to some embodiments of the present application, after the target divergence angle is determined, the phase delay difference required by the metasurface of the linear laser homogenizer is calculated through the parallel relationship between the target propagation direction of the incident light and the phase gradient of the light wave field, and the nano-pillar structure unit is arranged according to the phase delay difference.

[0016] In a second aspect, the laser radar according to the embodiments of the present application comprises the linear laser homogenizer according to the embodiments of the above aspect.

[0017] The linear laser homogenizer and the laser radar according to the embodiments of the present application have at least the following beneficial effects: the metasurface array structure composed of the nano-pillar structure unit and the substrate, the array mode of the nano-pillar structure unit is calculated according to the parallel relationship between the propagation direction of the light and the phase gradient of the light wave field, and the linear divergence homogenization of the laser can be realized. The present application uses the nano-pillar structure unit to construct the metasurface, which realizes the linear laser homogenization while having the integration of ultra-light and ultra-thin.

[0018] Additional aspects and advantages of the present application will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0019] The above and / or additional aspects and advantages of the present application will become apparent and be readily understood from the following description, taken in conjunction with the accompanying drawings, in which:

[0020] Figure 1 FIG. 1 is a structural schematic diagram of a linear laser homogenizer according to an embodiment of the present application;

[0021] Figure 2 FIG. 5 is a phase delay curve comparison diagram of a nano-pillar structure unit with a tapered radius of 20nm according to an embodiment of the present application;

[0022] Figure 3 This is a schematic diagram of the simulation results of the line laser homogenizer according to an embodiment of the present invention;

[0023] Figure 4 A scanning electron microscope image of the nanopillar structure unit of the line laser homogenizer according to an embodiment of the present invention;

[0024] Figure 5 This is an actual effect diagram of the line laser homogenizer according to an embodiment of the present invention;

[0025] Figure 6 The light intensity test results are for the line laser homogenizer in this embodiment of the invention. Detailed Implementation

[0026] The embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. The step numbers in the following embodiments are set only for ease of explanation, and there is no limitation on the order between the steps. The execution order of each step in the embodiments can be adaptively adjusted according to the understanding of those skilled in the art.

[0027] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0028] The terms "first," "second," "third," and "fourth," etc., used in the specification, claims, and accompanying drawings of this invention are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0029] Reference to "an embodiment" or "the embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase "in an embodiment" or "in the embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive.

[0030] Laser radar is a remote sensing technology that measures the distance of a target and obtains information of the target by emitting a laser beam. Laser radar linear scanning technology is one of the laser radar technologies, which obtains three-dimensional spatial information of a target through linear scanning, can quickly obtain a large amount of point cloud data, forms a three-dimensional surface model of the target object, and has the characteristics of high precision, high resolution and high efficiency. The design and performance of the beam homogenization shaping device in the laser radar optical system directly affect the scanning efficiency, resolution and accuracy of the laser radar system, but currently such devices have the common problems of high cost, complex processing and low integration.

[0031] To this end, the embodiment of the application provides a linear laser homogenizer and a laser radar, which are based on a metasurface array structure composed of a nano-pillar structure unit and a substrate. The array mode of the nano-pillar structure unit is calculated according to the parallel relationship between the propagation direction of light and the phase gradient of the optical wave field, so that linear divergence homogenization of laser can be realized. The application uses the nano-pillar structure unit to construct a metasurface, which realizes linear laser homogenization while having ultra-light and ultra-thin integration.

[0032] The linear laser homogenizer and the laser radar of the embodiment of the application will be described in detail below with reference to the accompanying drawings.

[0033] On the one hand, the embodiment of the application provides a linear laser homogenizer, as shown in Figure 1 The linear laser homogenizer comprises a substrate 100 and a plurality of nano-pillar structure units 200 arranged on the surface of the substrate 100. The plurality of nano-pillar structure units 200 are arranged in an array, and the array arrangement mode of the plurality of nano-pillar structure units 200 is calculated according to the parallel relationship between the propagation direction of light and the phase gradient of the optical wave field.

[0034] The substrate 100 can be made of quartz glass, calcium fluoride, barium fluoride or infrared chalcogenide glass, and in this example, the material of the substrate 100 is silicon dioxide. The substrate 100 made of silicon dioxide has high transmittance and low refractive index, which can minimize the influence of the substrate 100 on the line laser homogenization. The nano-pillar structure unit 200 can be made of gallium nitride, hafnium dioxide, titanium dioxide, silicon nitride, silicon or germanium, and in this example, the material of the nano-pillar structure unit 200 is amorphous silicon. Arranging the nano-pillar structure unit 200 made of amorphous silicon on the substrate 100 made of silicon dioxide, the high refractive index of silicon has stronger light confinement capability, which can better confine the incident light and ensure the divergence effect of the line laser.

[0035] In the embodiments of the present application, a plurality of nano-pillar structure units 200 are arranged in an array on the substrate 100, and the spacing of any two adjacent nano-pillar structure units 200 is equal. Changing the array period of the nano-pillar structure unit 200 can adjust the effective wavelength range of the super-structured surface of the line laser homogenizer; changing the arrangement mode of the nano-pillar structure unit 200 can change the laser divergence angle of the line laser homogenization device.

[0036] The array mode of the nano-pillar structure unit 200 is calculated according to the parallel relationship between the propagation direction of the light and the phase gradient of the light wave field, which can realize the linear divergence homogenization of the laser. Based on the edge ray theory of non-imaging optics, a mathematical model for accurately mapping the light rays from the super-structured surface to the target surface is established to solve the light ray vector coordinates. According to the consistency of the direction of the light and the direction of the phase gradient of the light wave field (i.e., the parallel relationship between the propagation direction of the light and the phase gradient of the light wave field), the phase distribution of the super-structured surface is calculated by using the light ray vector coordinates corresponding to each point.

[0037] According to the accurate light ray mapping relationship from the super-structured surface to the target surface, the propagation coordinates of the light rays are: , the normal vector of the phase curve of the light wave field is: ; i is the step of the super-structured surface structure unit, is the phase corresponding to the step point, P is the arrangement period of the nano-pillar structure unit, p is the side length of the equal-area region divided on the target surface, and the calculation formula of p is:

[0038] ;

[0039] wherein, a is the target divergence half-angle, d is the distance between the super-structured surface and the target surface, and x is the number of equal-area regions divided on the target surface.

[0040] The parallel relationship between the propagation direction of the light and the phase gradient of the light wave field is:

[0041] ;

[0042] The wavelength of the light ray is randomly given an initial phase , which is substituted into the parallel relationship to sequentially obtain subsequent phase values and obtain the array arrangement of the nanocolumn structure unit 200.

[0043] As shown in Figure 1 , in some embodiments of the present application, each nanocolumn structure unit 200 is composed of the opposite stacking of the upper two bottom surfaces of two circular truncated cones with the same geometric parameters, and has a structure shape of thick at both ends and thin in the middle, and any cross section is circular. This structure has higher energy concentration, and the energy is completely concentrated in the tapered portion in the middle of the nanocolumn structure unit, reducing the influence of the processing error of the nanocolumn structure unit 200 on the effect of the linear laser homogenization device. The nanocolumn structure unit 200 has the following structure parameters, which are the radius Rtop=Rbottom of the upper and lower two ends, the tapered radius Rmid, the unit height H, and the tapered height Hmid=1 / 2H. In this example, the radius (Rtop / Rbottom) of the upper and lower two ends of the nanocolumn structure unit 200 ranges from 40nm to 140nm, the tapered radius ranges from 20nm to 120nm, and the difference between the end face radius of the upper and lower two ends of the nanocolumn structure unit 200 and the tapered radius ranges from 20nm to 25nm. In this example, the difference between the end face radius of the upper and lower two ends of the nanocolumn structure unit 200 and the tapered radius is maintained at 20nm, at which time, as shown in Figure 2 , the phase delay curve is the smoothest and the curve is continuous, the selected radius range can completely cover 2π phase, and the size of the selected radius range is moderate, which is beneficial to processing.

[0044] After determining the target divergence angle of the superstructure surface of the linear laser homogenizer, the required phase delay difference of each point on the superstructure surface can be calculated through the parallel relationship between the target propagation direction of the incident light ray and the phase gradient of the light wave field, and the nanocolumn structure unit 200 is arranged according to the phase delay difference to form a nanocolumn array structure. It is shown in the formula that: first, the variable α in the formula represents the target divergence half-angle, when α changes, the side length p of the equal-area region divided on the target surface also changes, which finally affects the discrete phase distribution of the superstructure surface and the structure unit parameters corresponding to each discrete phase point. The height and arrangement mode of the nanocolumn structure unit 200 are determined according to the target divergence angle, and by changing the structure parameters and arrangement mode of the nanocolumn structure unit 200, the superstructure surface abrupt phase distribution curve can be changed to achieve different divergence angles.

[0045] The linear laser homogenizer according to the embodiments of the present application has the following advantages:

[0046] 1. The linear laser homogenization device based on the nano-pillar structure unit 200 of the embodiment of the application is applied to the visible light waveband, the light beam is incident from the rear of the structure stack, and the homogenized light beam with the target angle can be realized after the light beam passes through the super-structured surface of the nano-pillar structure unit 200 arranged in a specific manner. The entire super-structured surface has a micron-level thickness, can replace the traditional optical shaping element, and has the characteristics of high integration while realizing the same linear laser homogenization effect.

[0047] 2. Compared with the ordinary cylindrical structure unit, the nano-pillar structure unit 200 has higher energy concentration, and the energy is concentrated in the relatively thin tapered portion in the middle of the column structure unit, so that the influence of the processing error of the nano-pillar structure unit on the effect of the linear laser homogenization device is reduced.

[0048] 3. The amorphous silicon nano-pillar structure unit is arranged on the silicon dioxide substrate, the high refractive index of silicon has stronger light confinement capability, can better confine the incident light, and ensures the divergence effect of the linear laser; the silicon dioxide substrate has high transmittance and low refractive index, and can minimize the influence of the substrate 100 on the linear laser homogenization.

[0049] 4. By changing the structure parameters of the nano-pillar structure unit 200, the phase delay caused by a single structure unit can be changed, the array period of the nano-pillar structure unit 200 can be changed to adjust the effective wavelength range of the super-structured surface, and the arrangement mode of the nano-pillar structure unit 200 can be changed to change the laser divergence angle of the linear laser homogenization device.

[0050] The linear laser homogenization device of the embodiment of the application will be described in detail below with one specific embodiment. It should be noted that the following is only an exemplary description, but not a specific limitation of the application.

[0051] As shown in Figure 1 The embodiment of the application proposes a linear laser homogenization device based on a super-structured surface array structure composed of a nano-pillar structure unit 200 and a silicon dioxide substrate 100. The structural relationship characteristics are that the nano-pillar structure unit 200 is composed of the opposite stacking of the two upper bases of two geometric parameters completely consistent truncated cones, is arranged in a square arrangement mode with equal distances between adjacent structure units above the substrate 100, the period P=350nm, the structure unit height H=500nm, the upper and lower radii Rtop=Rbottom of the nano-pillar structure unit 200 change in the range of 40nm-140nm, the tapered radius Rmid changes in the range of 20nm-120nm, the difference between the end face radius and the tapered radius is kept at 20nm, and the tapered height Hmid=250nm.

[0052] AsFigure 2 As shown, when the radius difference of the nanocolumn structure unit 200 is 20 nm, the phase delay curve is the smoothest, and the curve is continuous, the selected radius range can completely cover 2pi phase, and the size of the selected radius range is moderate, which is beneficial to processing.

[0053] Figure 3 The simulation result diagram of the line laser homogenization device of the embodiment of the application is shown in the figure. From the simulation result, it can be seen that the superstructure surface can achieve the expected divergence angle.

[0054] Figure 4 The SEM diagram of the structural unit of the line laser homogenization device of the embodiment of the application is shown in the figure. The structural unit of the homogenization device has the structural characteristics of thick at both ends and thin in the middle.

[0055] Figure 5 The actual effect diagram of the line laser homogenization device of the nanocolumn array structure of the application is shown in the figure. The length of the light spot in the image is 247.60mm, the distance d between the superstructure surface and the target surface of the receiving screen is 200mm, the calculated divergence angle is 91.79°, which is basically consistent with the expected divergence angle effect. The light spot intensity is collected, the root mean square error RMSE calculation formula is selected as the evaluation formula of the light spot uniformity, and the calculation result shows that the light spot uniformity is 68.34%.

[0056] Figure 6 The light intensity test result of the line laser homogenization device of the nanocolumn array structure of the application is shown in the figure. The blue rectangular range is the effective divergence angle, and the calculated effective divergence angle is 91.66°.

[0057] On the other hand, the embodiment of the application also proposes a laser radar comprising the line laser homogenization device of the above-mentioned aspect embodiment.

[0058] The above has made a detailed description of the embodiment of the application combined with the drawings, but the application is not limited to the above-mentioned embodiment, and various changes can be made within the knowledge range of ordinary skilled in the art without departing from the purpose of the application.

Claims

1. A line laser homogenizer, characterized by, The application relates to a linear laser homogenizer, comprising: a substrate and a plurality of nano-column structure units arranged on the surface of the substrate, wherein the plurality of nano-column structure units are arranged in an array, the array arrangement mode of the plurality of nano-column structure units is calculated according to the parallel relationship between the propagation direction of light and the phase gradient of an optical wave field, each nano-column structure unit is composed of the opposite stacking of the upper surfaces of two geometrically consistent circular truncated cones, and the arbitrary cross section is circular; the parallel relationship between the propagation direction of light and the phase gradient of an optical wave field is: ； wherein, is the wavelength of the light, the propagation coordinate of the light is , the phase curve normal vector of the light wave field is ; i is the step of the nano pillar structure unit, is the phase corresponding to the corresponding step point, P is the arrangement period of the nano pillar structure unit, p is the side length of the equal-area region of the target surface division, and the calculation formula of p is: ； wherein alpha is a target divergence half-angle, d is the distance between the metasurface of the linear laser homogenizer and the target surface, and x is the number of equal-area regions divided on the target surface.

2. The line laser homogenizer of claim 1, wherein, The variation range of the radii of the upper and lower ends of the nano-column structure unit is 40nm-140nm, and the variation range of the tapered radius is 20nm-120nm.

3. The line laser homogenizer of claim 2, wherein, The difference between the end surface radius of the upper and lower ends of the nano-column structure unit and the tapered radius is 20nm-25nm.

4. The line laser homogenizer of claim 1, wherein, The material of the substrate is silicon dioxide.

5. The line laser homogenizer of claim 1, wherein, The material of the nano-column structure unit is amorphous silicon.

6. The line laser homogenizer of claim 1, wherein, The arrangement mode of the nano-column structure unit is determined according to a target divergence angle.

7. The line laser homogenizer of claim 6, wherein, After the target divergence angle is determined, the phase delay difference required by the metasurface of the linear laser homogenizer is calculated through the parallel relationship between the target propagation direction of incident light and the phase gradient of an optical wave field, and the nano-column structure units are arranged according to the phase delay difference.

8. A lidar, comprising: The application further relates to a linear laser homogenizer comprising any one of the linear laser homogenizers according to claims 1-7.

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