Laser radar lighting device and laser radar system

Abstract

The embodiment of the invention discloses a laser radar lighting device and a laser radar system. In one specific embodiment, the device comprises a semiconductor laser, a pyramid prism, a lens group and a receiving lens, the semiconductor laser is used for emitting Gaussian beams; the lens group is used for carrying out preliminary collimation on Gaussian beams emitted by the semiconductor laser and outputting the Gaussian beams to the top surface of the pyramid prism; and the pyramid prism is used for segmenting the preliminarily collimated Gaussian beam input from the top surface of the pyramid prism and outputting a plurality of segmented beams from the bottom surface of the pyramid prism to a to-be-measured target, so that the segmented beams are subjected to incoherent superposition on the surface of the to-be-measured target to form a flat-topped beam for illumination. According to the embodiment, the beam splitting characteristic of the pyramid prism is utilized, the preliminarily collimated beam is segmented, and incoherent superposition is carried out on the surface of the to-be-measured target to obtain the flat-topped beam which is uniform in intensity, has good distance transmission characteristic and meets field-of-view matching.

Description

Technical Field

[0001] The present invention relates to the field of laser radar technology, and more specifically, to a laser radar lighting device and a laser radar system. Background Art

[0002] LiDAR is an optoelectronic remote sensing detection device that uses laser as a radiation source and utilizes physical parameters such as reflected light echo intensity, phase, and polarization to actively measure the target distance, i.e., depth data.

[0003] The main function of the laser radar lighting device is to illuminate the target to be measured, and the quality of the illumination beam has a great influence on the measurement accuracy and imaging quality. The semiconductor laser, namely the laser diode, in the laser radar lighting device is a suitable active illumination light source for the laser radar. The semiconductor laser has a special resonant cavity structure and working mode. The spatial distribution of the light beam is asymmetric, and the light intensity distribution is uneven within the divergence angle in each direction. The unshaped semiconductor laser beam cannot meet the lighting requirements of the laser radar system, because the asymmetry of the illumination field does not match the receiving surface of the sensor, which is not conducive to the full utilization of light energy, and the uneven distribution of light intensity in the illumination field leads to a reduction in the dynamic range available to the system.

[0004] At present, the commonly used semiconductor laser beam homogenization technologies include: diffuse reflectors, diffractive optical elements, binary diffraction gratings, liquid crystal spatial light modulators, compound eye lenses, optical fibers, integrating rods, etc.

[0005] However, the inventors found that the use of diffractive optical elements can achieve flat-top uniform illumination, but cannot maintain spatial propagation characteristics. The quality level of binary diffraction gratings is restricted by the development level of micro-fine processing technology, and the laser damage threshold is low, and there are still difficulties in the application of high-power laser systems. The laser damage threshold of liquid crystal spatial light modulators is low, the device is expensive, and it is not easy to integrate and use. The compound eye lens can only produce a uniform light beam within a specific range, and the edge has a considerable proportion of non-uniform areas. This type of method has low coupling efficiency and high coupling cost, great technical difficulty, and is not conducive to miniaturization and integration. Methods such as optical fibers and integrating rods have low coupling efficiency and high coupling cost, large energy loss, great technical difficulty, and are not conducive to miniaturization and integration.

[0006] In summary, the illumination of LiDAR needs to meet three conditions at the same time: field of view matching, high-quality uniformity, and good distance transmission characteristics. However, the above-mentioned uniform illumination technology methods have deficiencies to varying degrees and are not suitable for or cannot meet the illumination needs of LiDAR. Summary of the invention

[0007] The object of the present invention is to provide a laser radar lighting device and a laser radar system for homogenizing light through a pyramid prism, so as to solve at least one of the problems existing in the prior art.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A first aspect of the present invention provides a laser radar lighting device, comprising:

[0010] Semiconductor lasers, lens groups and pyramid prisms;

[0011] The semiconductor laser is used to emit a Gaussian beam;

[0012] The lens group is used to preliminarily collimate the Gaussian beam emitted by the semiconductor laser and output it to the top surface of the pyramid prism;

[0013] The pyramid prism is used to split the preliminarily collimated Gaussian beam input from its top surface and output multiple split beams from its bottom surface to the target to be measured, so that the split beams are incoherently superimposed on the surface of the target to be measured to form a flat-top beam for illumination.

[0014] Furthermore, the pyramid prism includes a quadrangular pyramid portion and a rectangular parallelepiped portion, the conical surface of the quadrangular pyramid serves as the top surface of the pyramid prism, and the surface of the rectangular parallelepiped away from the quadrangular pyramid serves as the bottom surface of the pyramid prism.

[0015] Furthermore, the bottom surface of the quadrangular pyramid is coplanar with the surface of the cuboid close to the quadrangular pyramid.

[0016] Furthermore, the angle between the opposite cone surfaces of the quadrangular pyramid is designed to satisfy the following conditions:

[0017]

[0018] Wherein, α is the angle between the opposite cone surfaces of the tetrahedron, K is the F degree of the preliminary collimated light beam, and n is the refractive index of the pyramid prism material.

[0019] Furthermore, the first optical axis of the Gaussian beam emitted by the semiconductor laser and the second optical axis of the preliminary collimated beam output by the lens group are coaxial, and the second optical axis and the optical axes of each split beam output by the pyramid prism are parallel to each other.

[0020] Furthermore, the top and bottom surfaces of the pyramid prism are coated with anti-reflection films.

[0021] Furthermore, the lens group and the pyramid prism are made of K9 glass or quartz.

[0022] A second aspect of the present invention provides a laser radar system, comprising:

[0023] A laser radar system, characterized by comprising:

[0024] At least one laser radar lighting device as described in the first aspect, used to output a plurality of split light beams to a target to be measured, so that the split light beams are incoherently superimposed on the surface of the target to be measured to form a flat-top light beam for illumination;

[0025] The split light beams are incoherently superimposed on the surface of the target to be measured to form a flat-top light beam for illumination and then reflected;

[0026] A receiving lens, used for receiving the flat-top light beam reflected by the target to be measured;

[0027] A detection sensor, used for detecting the flat-top light beam received by the receiving lens and reflected by the target to be measured;

[0028] The processing and display module is used to process and display the data detected by the detection sensor.

[0029] Furthermore, the optical axis of the split light beam output by the laser radar lighting device is parallel to the receiving optical axis of the receiving lens.

[0030] Furthermore, the laser radar system includes a plurality of laser radar lighting devices and the plurality of laser radar lighting devices are distributed in an array.

[0031] The beneficial effects of the present invention are as follows:

[0032] The present invention utilizes the light splitting characteristics of the pyramid prism itself to split the initially collimated light beam and perform incoherent superposition on the surface of the target to be measured to obtain a flat-top light beam with uniform intensity, good distance transmission characteristics and field matching. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0034] Figure 1 A schematic diagram showing the structure of an illumination device provided by one embodiment of the present invention when a target to be measured is illuminated and has a shadow;

[0035] Figure 2 A schematic diagram showing the structure of a laser radar system provided by an embodiment of the present invention when a target to be detected is illuminated and has no shadow;

[0036] Figure 3 A schematic diagram showing a structure in which a preliminarily collimated Gaussian beam is incident on a pyramid prism according to an embodiment of the present invention;

[0037] Figure 4 A schematic diagram showing a structure in which split light beams provided by an embodiment of the present invention are incoherently superimposed on the surface of a target to be measured;

[0038] Figure 5 A combination diagram showing images taken with a camera, images obtained with a pyramid prism, and images obtained without a pyramid prism at different detection distances and different targets provided by an embodiment of the present invention.

[0039] Description of reference numerals:

[0040] 1. LiDAR lighting device; 11. Semiconductor laser; 12. Lens group; 13. Pyramid prism; 2. Receiving lens; 3. Detection sensor; 4. Target to be measured. DETAILED DESCRIPTION

[0041] In order to explain the present invention more clearly, the present invention is further described below in conjunction with embodiments and drawings. Similar components in the drawings are represented by the same reference numerals. It should be understood by those skilled in the art that the content specifically described below is illustrative rather than restrictive, and the protection scope of the present invention should not be limited thereto.

[0042] A laser radar lighting device 1, comprising:

[0043] Semiconductor laser 11, lens group 12 and pyramid prism 13;

[0044] The semiconductor laser 11 is used to emit a Gaussian beam;

[0045] The lens group 12 is used to preliminarily collimate the Gaussian beam emitted by the semiconductor laser 11 and output it to the top surface of the pyramid prism;

[0046] The pyramid prism 13 is used to split the preliminarily collimated Gaussian light beam input from its top surface and output multiple split light beams from its bottom surface to the target 4 to be measured, so that the split light beams are incoherently superimposed on the surface of the target 4 to form a flat-top light beam for illumination.

[0047] In a possible implementation, the pyramid prism 13 includes a quadrangular pyramid portion and a rectangular parallelepiped portion, the conical surface of the quadrangular pyramid serves as the top surface of the pyramid prism 13 , and the surface of the rectangular parallelepiped away from the quadrangular pyramid serves as the bottom surface of the pyramid prism 13 .

[0048] The bottom surface of the quadrangular pyramid is coplanar with the surface of the rectangular parallelepiped close to the quadrangular pyramid. Further, the pyramid prism 13 is an integrally formed structure so that the contact surface between the quadrangular pyramid part and the rectangular parallelepiped part has sufficient light transmittance.

[0049] The present invention utilizes the light splitting property of the pyramid prism 13 itself to split the initially collimated light beam and perform incoherent superposition on the surface of the target to be measured to obtain a flat-top light beam with uniform intensity, good distance transmission property and field matching.

[0050] In a possible implementation, the angle between the opposite cone surfaces of the quadrangular pyramid is designed to satisfy the following conditions:

[0051]

[0052] Wherein α is the angle between the opposite cone surfaces of the four-sided pyramid, K is the F degree of the preliminary collimated light beam, and n is the refractive index of the material of the pyramid prism 13 .

[0053] The first optical axis of the Gaussian beam emitted by the semiconductor laser 11 and the second optical axis of the preliminary collimated beam output by the lens group 12 are coaxial, and the second optical axis and the optical axes of each split beam output by the pyramid prism 13 are parallel to each other.

[0054] In a possible implementation manner, the top and bottom surfaces of the pyramid prism 13 are coated with an anti-reflection film.

[0055] By coating the surface of the pyramid prism 13 with an anti-reflection film, the transmittance of the light beam incident to the pyramid prism 13 and emitted from the pyramid prism 13 is increased.

[0056] In a possible implementation, the lens group 12 and the pyramid prism 13 are made of K9 glass or quartz.

[0057] In a specific embodiment, the semiconductor laser 11 emits a Gaussian beam to the lens group 12, which initially collimates the Gaussian beam and sends it to the top surface of the pyramid prism 13; the pyramid prism 13 splits the initially collimated Gaussian beam and outputs the split beams to the target to be measured, and the split beams are incoherently superimposed on the surface of the target to be measured to obtain a flat-top beam for illumination. In order to ensure that the split beams can be effectively superimposed, avoid Figure 2 When the split beam is irradiated to the surface of the target to be measured, a part that cannot be irradiated by the split beam (i.e., a shadow) appears, so the following design is required:

[0058] like Figure 3 and Figure 4 As shown, the relationship between the beam angle of the split light beam and the angle between two adjacent pyramidal surfaces of the pyramid prism 13 is determined as follows:

[0059] δ=(n-1)α (2)

[0060] Among them, δ is the angle between the two light rays at the illumination boundary of the Gaussian light beam after preliminary collimation and with the largest angle after they are incident on the pyramid prism 13; α is the angle between the opposite cone surfaces of the four-sided pyramid; and n is the refractive index of the material of the pyramid prism 13.

[0061] Determine the value of the angle between the two light rays at the illumination boundary of the Gaussian light beam after preliminary collimation and with the largest angle after they are incident on the pyramid prism 13;

[0062]

[0063] Wherein, δ is the angle between the two light rays at the illumination boundary of the Gaussian light beam after preliminary collimation and with the largest angle after incident on the pyramid prism 13; K is the F degree of the preliminary collimated light beam.

[0064] Substituting formula (2) into formula (3) yields the range of values ​​of the angle between the two side surfaces of the pyramid prism 13 .

[0065] In order to ensure that the split light beam will not fail to illuminate the target surface after irradiating it, the angle between the relative cone surfaces of the tetrahedron is designed to meet the following conditions:

[0066]

[0067] Wherein, α is the angle between the opposite cone surfaces of the tetrahedron, K is the F degree of the preliminary collimated light beam, and n is the refractive index of the pyramid prism material.

[0068] Combination Figure 2 , Figure 3 as well as Figure 4 The split light beams include a first light beam, a second light beam, a third light beam and a fourth light beam. The preliminarily collimated Gaussian light beam is split into four light beams symmetrical about the optical axis of the split light beams by a pyramid prism 13, wherein the light beam irradiated on the P1 surface is split by the pyramid and irradiates the S1 area of ​​the target to be measured as the first light beam. Similarly, the light beam irradiated on the P2 surface is split by the pyramid and irradiates the S2 area of ​​the target to be measured as the second light beam. The light beam irradiated on the P3 surface is split by the pyramid and irradiates the S3 area of ​​the target to be measured as the third light beam. The light beam irradiated on the P4 surface is split by the pyramid and irradiates the S4 area of ​​the target to be measured as the fourth light beam.

[0069] like Figure 4 As shown, on the basis of satisfying formula (1), by using pyramid prisms 13 with different angles, the size is adjusted, and then the size of the shadow area of ​​the target to be measured is adjusted to eliminate the shadow area; the Gaussian beams after the initial collimation after the segmentation are effectively superimposed.

[0070] In a specific embodiment, the semiconductor laser 11 has a wavelength in the near-infrared band, including but not limited to 850nm, 905nm, 940nm, and 1550nm; the lens group 12 is an optical lens group 12, and the material of the lens group 12 and the pyramid prism 13 are both K9 glass or quartz; K9 glass belongs to optical glass, and the advantage of using K9 glass as the material is that the price is low, but the purity of K9 glass quartz is low, and the absorption rate of light will be higher. Although the corresponding quartz glass has a higher cost, the purity of quartz is high, and the absorption rate of light will be lower.

[0071] More specifically, in order to increase the light transmittance of the pyramid prism 13 , the anti-reflection film in this embodiment uses a near-infrared band anti-reflection film.

[0072] In another aspect, the present invention provides a laser radar system, comprising:

[0073] At least one laser radar lighting device 1 as described above, used to output a plurality of split light beams to a target 4 to be measured, so that the split light beams are incoherently superimposed on the surface of the target to be measured to form a flat-top light beam for illumination;

[0074] A receiving lens 2, used for receiving the flat-top beam reflected by the target to be measured;

[0075] The detection sensor 3 is used to detect the flat-top light beam received by the receiving lens 2 and reflected by the target to be measured;

[0076] The processing and display module is used to process and display the data detected by the detection sensor 3.

[0077] In a possible implementation, the optical axis of the split light beam output by the laser radar lighting device (1) and the receiving optical axis of the receiving lens 2 are parallel to each other.

[0078] In one possible implementation, the laser radar system includes a plurality of laser radar lighting devices 1 and the plurality of laser radar lighting devices 1 are distributed in an array.

[0079] In one possible implementation, the system further includes a power module, which is used to supply power to the laser radar lighting device 1, the detection sensor 3, and the processing and display module respectively.

[0080] In a specific embodiment, Figure 3 As shown, the leftmost column is the actual image taken by the camera of the present invention, the middle column is the image collected when the pyramid prism 13 is not used in the present invention, and the rightmost column is the image collected when the pyramid prism 13 is used in the present invention; more specifically, Figure 3The first row shows images when the detection distance is 1.21m; the second row shows images when the detection distance is 3.75m, the third row shows images when the detection distance is 7.79m, and the fourth row shows images when the detection distance is 18.71m. It can be clearly seen from the figures that the images collected by the present invention after shaping the light through the pyramid prism 13 at different detection distances and different scenes are obviously more complete and comprehensive than the images collected without the pyramid prism 13, and more information elements are collected.

[0081] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper" and "lower" and the like is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the system or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. Unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0082] It should also be noted that, in the description of the present invention, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0083] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the embodiments here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A laser radar lighting device, characterized in that: include: Semiconductor lasers, lens groups and pyramid prisms; The semiconductor laser is used to emit a Gaussian beam; The lens group is used to preliminarily collimate the Gaussian beam emitted by the semiconductor laser and output it to the top surface of the pyramid prism; The pyramid prism is used to split the preliminarily collimated Gaussian beam input from its top surface and output multiple split beams from its bottom surface to the target to be measured, so that the split beams are incoherently superimposed on the surface of the target to be measured to form a flat-top beam for illumination.

2. The device according to claim 1, characterized in that The pyramid prism includes a quadrangular pyramid portion and a rectangular parallelepiped portion. The conical surface of the quadrangular pyramid serves as the top surface of the pyramid prism, and the surface of the rectangular parallelepiped away from the quadrangular pyramid serves as the bottom surface of the pyramid prism.

3. The device according to claim 2, characterized in that The bottom surface of the quadrangular pyramid is coplanar with the surface of the cuboid close to the quadrangular pyramid.

4. The device according to claim 2, characterized in that The angle between the opposite cone surfaces of the tetrahedron is designed to meet the following conditions: Wherein, α is the angle between the opposite cone surfaces of the tetrahedron, K is the F degree of the preliminary collimated light beam, and n is the refractive index of the pyramid prism material.

5. The device according to claim 1, characterized in that The first optical axis of the Gaussian beam emitted by the semiconductor laser and the second optical axis of the preliminary collimated beam output by the lens group are coaxial, and the second optical axis and the optical axes of each split beam output by the pyramid prism are parallel to each other.

6. The device according to claim 1, characterized in that The top and bottom surfaces of the pyramid prism are coated with anti-reflection films.

7. The device according to claim 1, characterized in that The lens group and the pyramid prism are made of K9 glass or quartz.

8. A laser radar system, characterized in that: include: At least one laser radar lighting device as claimed in any one of claims 1 to 7, used to output a plurality of split light beams to a target to be measured, so that the split light beams are incoherently superimposed on the surface of the target to be measured to form a flat-top beam for illumination; A receiving lens, used for receiving the flat-top light beam reflected by the target to be measured; A detection sensor, used for detecting the flat-top light beam received by the receiving lens and reflected by the target to be measured; The processing and display module is used to process and display the data detected by the detection sensor.

9. The system according to claim 8, characterized in that The optical axis of the split light beam output by the laser radar lighting device is parallel to the receiving optical axis of the receiving lens.

10. The system according to claim 8, characterized in that The laser radar system includes a plurality of laser radar lighting devices, and the plurality of laser radar lighting devices are distributed in an array.

Images